Woofer size and power usage.

[[DANGERDAN]]

Sup guys :), I was told a while ago that the smaller the woofer the harder it is to drive for eg. 6 inch vs 8 inch, i was told the 6 inch would be harder to drive (need more watts) because it has to move more air so i thought id see what you guys thought.

:up:

[OldChap]

Only true for the same volume (loudness) the frequency is set say 50Hz that is the speed the cone is moving in and out now think of the area of a 6" cone and that of a 10" cone that is the amount of air being moved (loudness) now think of the amplitude of the movement say 6mm start multiplying these together for an idea of the difference in audible output as frequency drops. Adding more power is only good up to the limit of the speaker extrusion (the max the cone will go in and out)

If you actually know such things as impedance this calculation can be done properly (I'd have to look up the equation)

Want to learn about tis stuff? try to find a copy of the loudspeaker design cookbook by Vance Dickerson there are many editions but even an early one would serve its purpose here.

To give an idea on power I once had an active system with 30w amps on the treble and 300w amps on the bass (both 8ohm loads)

[STEvil]

largely dependent on room size and box design (sealed, ported, t-line, horn, x-order, etc etc etc..), motor rest position (overhung/underhung), motor strength (dependent on coil length, material, magnet material, magnet design, and how close the magnet is to the coil), excursion (not extrusion), and even the frequency bandwidth your driver is capable of using.

Of importance as well is that the weight of the diaphram between a smaller driver and a larger one will be different. So even though a 6" needs to move further to create the same decibel level the power usage will be similar overall, until you run into the point you start causing power compression.

[Nanometer]

The general biggest factor is room size and aesthetics. You might be surprised as I was to try a 300 watt sub in a small room, think it sounds just great until you bring it to a room that is double in size. Suddenly you are low on power and have lost the room shacking prowess. These guys summed up this stuff pretty nicely.

[Donnie27]

The general biggest factor is room size and aesthetics. You might be surprised as I was to try a 300 watt sub in a small room, think it sounds just great until you bring it to a room that is double in size. Suddenly you are low on power and have lost the room shacking prowess. These guys summed up this stuff pretty nicely.

After reading this, it took a few days but I tried mine at friend's with a den that 20 x 40 feet, with hardwood floors. I don't know, but I call that big. My dinky cheap Pioneer with only a 240W Dayton Plate AMP like that room better than my Den that's something like 11 by 24 rectangle.

In the corner and a large enough area for the Bass to expand was awesome!:shocked: I'm no big fan of SPL as STEVil can tell you but my bud's son is now copying my smaller Sub.

Nothing special went into this sub and at least 3 people have recreated it and all are happy with the results. I was so impressed I ordered another 250w when I was about to get the 500W version for my next Sub.

As one of my friends would say, "You can't hold good Bass Down".

[SabreWulf69]

Bigger speaker = more mass to move in and out. You'll always require larger amounts of power to properly drive larger speakers, it's just common sense.

[STEvil]

Bigger speaker = more mass to move in and out. You'll always require larger amounts of power to properly drive larger speakers, it's just common sense.

No.

Larger speakers usually have larger voice coils which provide them with higher or equal motor force to diaphram weight ratios compared to smaller drivers. If you buy "large" speakers with tiny voice coils they probably suck anyways.

[SabreWulf69]

I swear this is the case. Science of whatever aside, common sense and experience says, bigger driver, bigger power requirements. I dare you to run an MTX Jackhammer from a 30W tweeter amplifier and have any sort of decent result, and vice versa with out the tweeter exploding in a fraction of a second. Is simple, if you have 2 drivers made out of the EXACT same stuff, in the EXACT same way, but one is larger in every component and material that is used compared to the smaller driver, the bigger one will use more power. More practical tests, hook it up to measuring equipment, the bigger one will use more power. This isn't the science of schrodinger's cat, nor the complex semantics of theology or philosophy, it's just plain Jane common sense.

[STEvil]

Ever bothered to look at the efficiency or sensativity ratings of the driver? Most tend to be in the range of 80-95db @ 1w. Some can be as high as 110db @ 1w.

Comparing a jackhammer (you mean the 22/24, right?) and a tweeter just isnt a valid argument at all given that they are meant for completely different frequency ranges.

Again, given a proper build method, you do not "need" more power for a larger driver.

[SabreWulf69]

Efficiency and sensitivity are only one part of the picture, then there's damping control, what you want to get out of the speaker to begin with and a whole other range of things to consider.

...OK then, power a Jackhammer with a headphone amplifier, and run a low-pass filter to it, or is it again, 'meant for different things'?. Proper build. I give up, your a genius engineer. Who needs big power for big speakers?, I mean clubs do, and concerts, and big subs, and generally every other large speaker from anyone of significance that can build 'proper' speakers like KEF, Bowers & Wilkins, Wilson Audio just for example. But yeah, your somehow right, and I'm somehow arrogant and dumb. No psuedo sciences for me, just plain 'it makes sense'. :shakes:

Give a real life example of this miracle massive speaker that can for example be powered by a 1-watt amp and play extremely loudly and clear and then I'll be listening. You sure are re-writing the engineering books on this one and throwing out all the required power rating systems they have on I think every speaker in existence.

I have briefly read the Loudspeaker Design Cookbook by Vance Dickinson plus many more including Audio Engineering - Know it all, Master Handbook of Acoustics, Sound Reproduction - Loudspeakers And Rooms by Floyd Toole, and High Performance Loudspeakers - Fourth Edition by Martin Colloms. In which and where are you referring to your theory, if you can point it out without mincing their words, then I'll listen, until then, small speakers = small power, big speakers = big power. Even with tube amps and electrostatics your theory doesn't work in reality, even though 'normal' drivers is what the OP is talking about. :shrug:

Trust me I'm willing to listen, if you can convince me otherwise. I'd love to power my dual 12" towers at home without a power thirsty amplifier, I really would. I'm talking about if *everything* is larger on the larger driver.

[Edit]
Technically your saying, maybe 2 *different* drivers of different sizes, and having the magnet and voicecoil on the larger one extremely small and having only the diaphragm, frame and surrounding significantly larger than the small one then it would be in this situation that you would need significantly less power than the smaller one?, or the other way around?, I don't know, I prefer my common sense. I look at this as mincing meanings, when I hear bigger driver, I mean bigger driver overall, I say what I mean as a whole and mention if it is only in part.

[STEvil]

I think you've forgotten to look at the basic laws of physics in play or you were misreading something.. anyways.

Driver diaphragm area (note: general numbers, not taking into account surround width).
8" = 50.27 in^2
10" = 78.54 in^2
12" = 113.1 in^2
15" = 176.71 in^2
18" = 254.47 in^2

Voice coil area (note: assuming a 2" winding depth for all coils).
2" = 12.56637 in^2
2.5" = 15.70796 in^2
3" = 18.84956 in^2
3.5" = 21.99115 in^2
4" = 25.13274 in^2
6" = 37.69911 in^2

Assuming motor strength (magnet power) is the same between all drivers and discounting gauss saturation the moving mass (diaphragm, coil, suspension compliance) is pretty much the only factor at play. Most loud speakers generate between 1 and 5 teslas of force. 1 tesla is the force of 1 newton being exerted on 1 wire carrying 1 amp of current. After the math that comes out to a force that accelerates 1kg of mass at 1 meter per second squared.

So, if we have a tesla of "1" for simplicities sake and compare a 10" driver with 2" voice coil to a 15" driver with 3" voice coil we can see that although the 10" driver has a better diaphragm area to voice coil area ratio (6.25 vs 9.37) the 3" coil is also providing 1.5 times more effective area for the motor force to of the magnet to act on. Also the 10" driver must move 2.2 times further than the 15" driver to attain the same amount of air excitation. In short, you will need more power for the smaller driver to attain the same performance as the larger driver given that they are constructed with reasonable similarity aside from voice coil size. Of course voice coil size will also increase moving mass (a 3" coil can be 2-3 times the weight of a 2" coil depending on construction), but if you are using a larger driver you should be considering your application anyways. Asking a 15" driver to perform the same characteristics of an 8" or 10" in the vocal ranges is generally not going to happen while also handling lower frequency output.

Of importance is that you seem to think I am indicating that reduced power is required. I am not suggesting this. What I am saying is that believing you need large power for a large diaphragm is a misnomer. Yes, more power can be utilized. Yes, a larger speaker is more likely to be found in a larger auditorium environment where it can make use of more power. However 150w for a 10" or 150w for a 15" is probably going to give you basically the same effective loudness in a confined area such as a home. In a large area the drivers chosen for the venue will likely be constructed with the ability to handle more power as well, and thus will require more power be default as well.

Heck, i've got a set of towers with dual 10's in them that are very much more sensitive than my smaller towers with dual 6.5's in them. Can barely turn the amp up past 1/8th power before they are obnoxiously loud for average listening. This is just on a tiny old phillips 2x50w amp.

As for a real-life example of a "massive" speaker playing loudly on a small amount of power, I have a 21" Pyle Pro. Its rated at 105db with 1 watt. That rating is a load of dung, but i'll agree that its loud and efficient as it can keep up with the dual 10 tower in a free-air environment quite easily on the same power. The dual 10 towers are SPL Monitor 4000's. They were cheap and sound decent :) The Pyle works well up to about 170hz.

edit

I was going to add a link to some "extreme" testing but I cant find it anymore. Had to do with "Team Riprock" and their quest for 180+ db.

[SabreWulf69]

So as long as the voice coil increases in size proportionately along with the size of everything else in the larger driver not just in 'steps' of inches compared to the smaller driver i.e. just larger for the sake of more power handling when you give the smaller and the larger driver the same amount of power they will be equal to the same loudness, correct? I can see some downfalls of this as mentioned with power compression from over-excursion if all competing drivers are being driven to their limits.

Also, with SPL, (just an example) would a 500W 8" sub put out the exact same amount of volume as a 500W 12" sub without over-excursion when driven with identical loads? Realistically would you really expect to see a 8" driver having higher or equal operating mechanical and electrical limits compared to a similarly priced 12" driver? Also with damping factor, aren't larger loads (specifically the relationship with impedance changing with frequency) more demanding from larger speakers than smaller? I am also guessing that with frequency changes speakers can become (depending on size) more or less sensitive and efficient.

I guess the aim to designing a good speaker is getting as close to a hypothetical perfect speaker which has perfect infinite pistonic motion across the entire frequency spectrum with infinite stiffness and zero mass as much as possible.

[STEvil]

So as long as the voice coil increases in size proportionately along with the size of everything else in the larger driver not just in 'steps' of inches compared to the smaller driver i.e. just larger for the sake of more power handling when you give the smaller and the larger driver the same amount of power they will be equal to the same loudness, correct? I can see some downfalls of this as mentioned with power compression from over-excursion if all competing drivers are being driven to their limits.

Until you hit the points of compression and saturation, pretty much yes.


Also, with SPL, (just an example) would a 500W 8" sub put out the exact same amount of volume as a 500W 12" sub without over-excursion when driven with identical loads?

As long as the load is within their mechanical ability this could be possible. The 12" will have more mechanical ability, however.


Realistically would you really expect to see a 8" driver having higher or equal operating mechanical and electrical limits compared to a similarly priced 12" driver?

Examples of this do exist in the car-audio world.. :)


Also with damping factor, aren't larger loads (specifically the relationship with impedance changing with frequency) more demanding from larger speakers than smaller? I am also guessing that with frequency changes speakers can become (depending on size) more or less sensitive and efficient.

Impedence will change less on a driver experiencing less excursion than one experiencing more excursion. With less movement of the coil there will be less change of dampening factor over frequency range and even phase-plugs and pole vents for horn enclosures become less of an issue. If you stay at lower excursion levels.


I guess the aim to designing a good speaker is getting as close to a hypothetical perfect speaker which has perfect infinite pistonic motion across the entire frequency spectrum with infinite stiffness and zero mass as much as possible.

Of course :)

[SabreWulf69]

That pretty much clears all of that up about what I was assuming, cheers.

[Nanometer]

Yea, interesting read there. Far more than I ever considered in the speaker world.

[[DANGERDAN]]

Man some of the stuff you guys know lol its like a frizzy gorilla doing accounting haha, good read good debate :).

[SabreWulf69]

A good reference on this / these topics, besides a load of books, can be found on these pages -

Overpowering, Underpowering, Distortion, Clipping, and Everything in Between (http://audiojunkies.com/forum/blog/4736-overpowering-underpowering-distortion-clipping-everything-between.html)

Heavy Load: How Loudspeakers Torture Amplifiers (http://stereophile.com/reference/707heavy/)


and as a little bonus this is just really awesome :-) v

Bowers & Wilkins - A Sound Experience Video Series (How they make their 800D series speakers) (http://www.youtube.com/watch?v=D1JgjSEEuPM&feature=PlayList&p=2177A824EF45695C&index=0&playnext=1)


[Edit]
I believe you can overpower something, just don't overdrive it, if you want to hear the maximum fidelity and loudness from a speaker, make sure it is amplified properly, have your gains set correctly among other things, then you can't go wrong. I have always said music no matter what it is can't kill a system, people, incorrect configurations, and poorly made components kill systems. The general science is --> 3 things kill speakers 1) Exceding thermal limits. 2) Exceding mechanical limits. 3) Material degradation. "Generally, amplifiers use the formula V1=G*V2. To power the amplifying device, you usually need two reference points, +Vcc and -Vcc. For symetrical reasons, they usually have the same absolute value. If these values are not high enough, the amplified peak value may exceed +-Vcc, causing clipping". Clipping can = harsh and distorted sounding speakers.

[Donnie27]

Ever bothered to look at the efficiency or sensitivity ratings of the driver? Most tend to be in the range of 80-95db @ 1w. Some can be as high as 110db @ 1w.

Comparing a jackhammer (you mean the 22/24, right?) and a tweeter just isnt a valid argument at all given that they are meant for completely different frequency ranges.

Again, given a proper build method, you do not "need" more power for a larger driver.

QFT! It should have simply ended here!:up:

[STEvil]

Yeah, clipping can kill a voice coil very easily. I've seen tests done on extreme car audio subwoofers where they were fed 7,000w RMS (two separate coils for 1 driver so 3,500RMS per coil) for hours on end of clean power and didnt die. Feeding that same power below the tuning frequency or using clipped signals/power would result in thermal destruction in just a few minutes. Even 1000w of clipped power can cause damage to the same drivers.

[SabreWulf69]

QFT! It should have simply ended here!:up:

I made my points, which I thought were valid.

I still don't see how a smaller speaker would directly load an amplifier *more* than an equivalently made larger speaker. I get told one thing from those articles I posted and read certain things about it in various books, and get told differently, I don't know what to think now. Trolls aside, could you once more explain to me in terms that other people use from articles like the ones I have posted, in how this is possible with proportionately larger drivers? Could you please, please quote me or link me to some reference material?

[STEvil]

I'm not sure what exactly I could point you at to clear it up any further. Maybe you need to think of it in terms of decibels versus distance (or room size, discounting construction materials/strength) from the diaphram/speaker. For example if you had an 8" driver and a 12" driver both rated at 88 decibels efficiency at 1 watt at 1 meter, the 8" driver may only reach 75 decibels at 5 meters, whereas the 12" may still be near to 80-85 decibels.

[SabreWulf69]

I'm not sure what exactly I could point you at to clear it up any further. Maybe you need to think of it in terms of decibels versus distance (or room size, discounting construction materials/strength) from the diaphram/speaker. For example if you had an 8" driver and a 12" driver both rated at 88 decibels efficiency at 1 watt at 1 meter, the 8" driver may only reach 75 decibels at 5 meters, whereas the 12" may still be near to 80-85 decibels.

So therefore the smaller driver is quieter than the larger one, well that is indeed simple and relates to everything that I was trying to say from the beginning.

[STEvil]

I cleaned out donnie's.. posts..

Anyways, yeah. The smaller speaker is "quieter" for a given amount of power, but that doesnt mean a larger speaker requires more power. Most of the efficiency has to do with the voice coil being inside the magnetic gap. The more it leaves the gap the less efficient the coil is.

[[DANGERDAN]]

The woofer size's differentiate in SPL and in the performance of how well it can handle a given frequency, what makes sense to me is that maybe at frequency's where the cone does not have to move very much ( 1khz ) that they may not have a very different power usage level.
But If given a frequency to the drivers that forces it to move at its hardest you would see a big difference id say, generally the bigger the woofer size the more air it can move and the more power is needed to move that driver at its physical peak.

Now obviously a smaller driver can try to produce what a bigger driver can do much more easily and fail because it does not have the physical properties to naturally reproduce this frequency, so the smaller driver would not pull much power trying to produce what the bigger driver is built to do.

I have not looked much into SPL but it seems to me as the driver size increases the easier it is to drive ( less watts ) but then as you increase the size of the woofer the more capability the driver has to produce lower frequency's and then the physical limit is increased and more power is needed to drive to its peak.

My guess is if SPL is your goal at a frequency that's the easiest for the given driver size then generally the bigger the more easy it is to drive, but the way i would do it is the physical limit pushing its max and measuring those results because speakers are made to reproduce at its best the entire frequency range.

Be gentle with me i could be wrong as most of this is best guess at how i think it all works, but i do believe that the bigger the driver the more power is required to drive at its peak frequency ( impedance dip ).

[STEvil]

peak frequency is not related to this. Impedance change (rise and dip) are due to excursion. More excursion means more power required.

[[DANGERDAN]]

Yes but isn't the excursion dependent on what electrical signal is drawn to the woofer, different electrical signals ( frequency ) give a different excursion effect.
So depending on the woofers Max excursion depends on its lowest frequency it can produce, the lower the frequency the bigger the excursion and the more power is required.

[STEvil]

Excursion is the least at the octave(s) nearest the tuning frequency of the enclosure and the resonant frequency of the room or auditorium (also depends on dampening factor and driver fs). Enclosure type plays a huge role whether excursion will be more centric on the tuning frequency or "flat"..

lower frequency only requires more excursion if you want it loud, but most systems have frequencies below the tuning point of the driver attenuated...

[chew*]

Good topic,

In the car audio competition world we used to have a phrase.

Amps don't kill speakers. Distortion kills speakers. Speakers kill amps.

Distort, clip or generally just abuse a sub and one of 2 things will happpen, the voice coil will fry, or the speaker will create enough feedback to kill the amp.

When I was competing hardcore in SPL, i used to use a single memphis mojo 15" quad 1 ohm sub. We put about 4000 watts to it.

Generally speaking you can put massive amounts of wattage to a sub without killing it as long as the signal is clean and there is no clipping.

All things considered however to put 4 times the RMS power ( 4000 watts give or take in my case ) into a speaker requires level matching and also a properly tuned enclosure.

Usually in this application whats considered a One note wonder, in my case it was 52 hz which was the resonant frequency of my little mazda mx3.

Port was tuned just a tad off from that frequency to account for the "rise time" of the sub.

Running lower frequency can detonate sub almost instantly in cases like this which is why you also want some form of active or passive crossover in the line with a very sharp cutoff, like 18-24db slope.

[STEvil]

4KW is childs play these days :)

Alan Dante is running 88KW+ to a single 18" lol.

[SabreWulf69]

One of the most fundamentally misunderstood concepts in audio is what
happens when we apply power to a speaker. We understand that power is
what makes the magic happen, but so few of us "get" what that power
does. For example, you've probably heard about someone who was
"underpowering" their speaker; what on earth does this mean? You've
probably heard this before and if you haven't it will probably be a
wake-up call: if underpowering really existed, you would be
"underpowering" your speaker every time you turned down the volume.
This is one of many ideas that continues to falsely permeate the audio
industry and, together, we can put an end to it.

[more]
So where do these misunderstandings come from? Well, the power concept
is inevitably encountered in two situations: 1) You are looking for a
certain level of output, and 2) You have a speaker that doesn't work
anymore. These two concepts are completely related: if you seek a
certain level of output that requires more power than the driver can
handle, then you're looking at scenario #2.

*Definitions*
To understand the idea behind power, let's define a few things first,
shall we?

/Overpowering/ - Overpowering should be simple to understand: a driver
is being "overpowered" any time it has been damaged. If the driver has
not been damaged, have you really "over" powered it? Logic should say
no. In fact, this is probably a term you can stop using in the future.

/Underpowering/ - As I mentioned above, this is a completely useless
and non-sensical term. If you don't have the output you want to hear
from a speaker, say as much. Again, we should stop using this term.

/Distortion/ - Distortion can come from a lot of sources. In the
simplest sense, distortion is when the output signal differs from the
input signal. For the purpose of this article, we will be looking
primarily at distortion generated by the amplifier and passed to a
speaker. As a secondary form of distortion, we will briefly talk about
driving a speaker into distortion, by which I mean that the speaker has
been driven beyond Xmax. Distortion from your speaker is a whole other
ball of wax and we will only briefly stop here today.

/Clipping/ - Here we will strictly stick to the type of clipping that is
passed from your amplifier to your speaker, and is created by setting
the input sensitivity (read: gain) too high when considering the input
voltage from your source unit (ie. headunit, preamp, etc).

*Clipping and Distortion*
Warning: Much of the following will directly oppose everything you've
ever been told about power, distortion, and clipping. The fact remains
that power is almost completely misunderstood, even by many experts in
the industry.

Let us start the next section by breaking down distortion generated by
the amplifier and clipping, which are really the same thing. As we said
early, distortion occurs when the output signal is different than the
input signal. I will give a very simple example here and introduce you
to a concept that may be new to you.

When we play a signal on your speaker, the resulting sound consists of a
number of frequencies with various amplitudes. If we play a 100 Hz sine
wave through a speaker, then the fundamental frequency is 100 Hz. Now,
we may also see response at other frequencies that are typically a given
order higher than the fundamental. Assuming a fundamental frequency of
100 Hz, we can say that the second harmonic is 200 Hz, the third
harmonic is 300 Hz, the 4th is 400 Hz, and so on. The presence of any
of these additional harmonics is considered distortion as they were not
present in the original signal. Typically, the amplitude of these
harmonics decrease as the harmonic itself increases, ie. second harmonic
distortion is often higher than third, third is higher than fourth, etc.

Clipping is itself a form of distortion. In the above example, we
assumed a 100 Hz signal. However, if we were to increase the gain until
we have fully clipped the signal, the result would be the fundamental
frequency (100 Hz) and its higher order harmonics. If you've ever heard
a speaker reproducing a clipped signal, you probably already know that
is sounds like distortion, but you've probably also been told something
else: that distortion or clipping an amplifier will immediately damage
your speaker. Hold on to your hats: it doesn't! Perhaps a little
further explanation is required?

Here is a picture demonstrating what a sine wave looks like, as well as
a square wave (fully clipped signal), a triangle wave, and a sawtooth wave.

http://media.audiojunkies.com/sine-wave-audio-signal.jpg
- Image: Wikipedia

That square wave sure looks ugly! More importantly, you should notice
one very important thing, though, when comparing a sine wave and a
square wave: the area under the curve from any point A to any point B
will always be greater with a square wave than with a sine wave. In
other words, a square wave carries more power over a given time. I like
to call it "increased average power over time" because it sounds cooler
that way. Hopefully the visual makes this next sentence understandable
as well: if the amplitude of the signal increases (the power increases)
within a given period of time, then the average power over time has
increased as well.

*How a Speaker is Damaged*
Let's take a moment now to examine why and how speakers are damaged by
power. Essentially, there are two types of failure:

1) Mechanical - This means that the speaker has physically been driven
beyond its limits; usually stuff starts banging together. For example,
a speaker can be mechanically damaged if the former is smashed into the
backplate a time or two. This occurs from applying too much
instantaneous power (read: power at any given moment) in a certain
enclosure. Since excursion (which is how much the coil moves) increases
as frequency decreases, we know that a speaker is more likely to have
over-extended itself at low frequencies. This is increasingly likely if
the enclosure is larger than typical for that subwoofer, or if you are
playing frequencies that fall below the "tuning frequency" of your
vented enclosure.
2) Thermal - Simply put, this happens when more power is dumped into the
voice coil than the coil can handle.

But stop! Thermal damage doesn't just come from too much power. Have
you ever wondered why a speaker can take ungodly amounts of power for a
brief moment without the coil exploding? Well, that's because it is
average power over time that matters. There are many subwoofers that
can take 10 kW or more for a second or two, but not many that can take
it for a full minute. And here we come full circle: whether it is a
sine wave, square wave or any wave in between, the speaker will not be
damaged thermally if the input average power over time is less than the
driver can handle. That's right: a low amplitude clipped signal will
not damage your speaker at all! You can test this for yourself: get a
speaker, hook it up, play a clipped signal, and keep the volume low.
You will not see any damage at all.

*When is it too much? When is it not enough?*
So the natural question arises: what is too much average power over
time? To be honest, it is tough for any layperson to make a good
estimate. Manufacturers typically publish power handling specifications
like "100 Watts RMS," which is misleading because there really is no
such thing as "Watts RMS" (a story for another day, or you can read here).
However, we know that we can apply more or less power if we adjust the
time over which this power is applied accordingly, which is why I
support buying just enough.

Dynamite in a monkey's hand is quite dangerous and too much power in a
novice's hands is equally so (minus the casualties). One has to wonder,
though: what is really gained by exceeding the manufacturer's own
recommendations? Is the associated thermal risk of increasing power
really worth it? The answer is simply no, unless you are chasing tenths
in SPL competitions. When more power is applied to the voice coil, the
voice coil becomes hot (duh!). At a certain point, this heat begins to
increase the resistance of the voice coil to the current flowing through
it. So we add more power, and more power, and more power... and before
you know it, the resistance of the voice coil has increased such that
adding more power will not gain any more output. Better yet is the
nature of the human ear: an increase in sound pressure of 1-3 dB is just
barely audible for most humans. To achieve such an increase, we are
looking at doubling the power we are already applying and, thus, putting
the coil at greater risk of thermal failure.

In the event you can't achieve the output you're looking for within the
manufacturer's recommended power handling specifications, your best
solution is usually to look for a different speaker. Of course,
achieving high-output is an equally complicated concept, but more power
than a speaker is rated for is rarely the solution (and will most
certainly void your warranty).

*Conclusion*
In short, you should now understand that only power can damage a
speaker. There are no mystery clipping gnomes that will kill your
speaker at the first sign of distortion. Furthermore, you should be
aware that power is just a way to get a speaker moving: there is no
underpowering or overpowering, there are just various levels of output
and a damaged speaker. Next week we will look even more closely at some
of these concepts, but please ask questions or correct me if something
is unclear. It is time to stop perpetuating these myths that never seem
to die and a good education is the right battle-axe to wield in this fight.

Source (http://audiojunkies.com/forum/blog/4736-overpowering-underpowering-distortion-clipping-everything-between.html)

Sorry to seem like a troll, but I seriously think this is definitely relevant

[STEvil]

Relevant to? Me and Charlie already know that :)

Of interesting note is that the material did not cover a clipped power output stage (high level) of an amplifier, only a clipped input signal. 1500-1800W of clipped power can easily cause thermal failure on a high end subwoofer or two. I should know, i've got a pair of subs rated at 5KW each and on only 1500-1800W RMS i've managed to make them stink, lol.

Mind you that is also at below tuning frequency to make them do that. At tuning or above they would probably handle it fine.

This guy sums it up high level clipping pretty good: http://audiojunkies.com/forum/9625-post14.html

[SabreWulf69]

I guess I'd like a whole bunch of equipment to be have continuous peak power ratings instead of having an average rating overall. That way no matter what material you put into a voice coil, the harmonics, and extra power from square waves will not kill your speakers.

[STEvil]

The harmonics arent the issue, they're just a frequency like the rest of the frequency you're putting in. The issue is the high level clipped signal.

Continuous is RMS. Peak is usually at least twice the RMS rating (doubling RMS equals high level clipped signal power) and sometimes 3 or 4 times, and tends to be the number that cheap amps are sold by.

[chew*]

4KW is childs play these days :)

Alan Dante is running 88KW+ to a single 18" lol.

Damn. Crazy stuff. I just couldn't afford it anymore. I still have my future project car for SPL that i won't let go though. Little tiny ford festiva was going to get a wall with a single 18".

[STEvil]

Its possible to do it relatively cheaply, but you cant play in the big leagues without spending major dollars :( The big thing thats blocking me from doing anything is the traveling.. that and I have this thing against the stupid rules they use these days, heh.

[SabreWulf69]

I mean I would like a rating of continuous square wave handling power, not an every now and then peak power rating.

[STEvil]

Why would you want to feed that kind of signal? I would sound horrible.

[SabreWulf69]

Just to know 100%, that if anything ever clips, my equipment won't get damaged.

[STEvil]

I totally forgot to even factor in how voice coil size vs movement will change performance as well.. wow I feel dumb lol. Just to put it shortly, larger coil with less excursion (due to larger driver) retains more motor force and sensativity :)

Also, cant wait to see some finished products of this thing (yes there have been retail products of this design before, but they didnt get marketed very well):
http://www.faultlinecustoms.com/DSCN2877.JPG

[STEvil]

Small bump.. pulled apart a dead 18" sub rated at 5,000w RMS today...

http://i216.photobucket.com/albums/cc232/STEviltoo/HK18s/Hpim0323-small.jpg

and... wow.

http://i216.photobucket.com/albums/cc232/STEviltoo/HK18s/MA18-dead-closeup.jpg

[NEOAethyr]

@STEvil
Are you making your own subs dude?
If so, where are you getting all your parts?

I've only see replacement parts when looking for cerwin vega stroker series subs...
Usually only the cone or surround parts.

I've love to be making my own subs and selling them locally as well.

The wire and coating for that I know of, but the cones and dust covers, surrounds(prefer dual rubber), chassis I guess you could call it and the magnets I don't have a clue where to get from.
Magnets I suppose I could figure out something but everything else I'm unsure of.

[chew*]

Small bump.. pulled apart a dead 18" sub rated at 5,000w RMS today...

http:///Hpim0323-small.jpg

and... wow.

http://i216.MA18-dead-closeup.jpg

Hah looks like that sub bottomed out in a hard hard way.

That is just pure ugly, what the heck did they do.

I never managed to do that even when I ran a 20hz sine wave on a sub in a tuned enclosure for 52hz just to put it out of its misery after a 2 year comp strek ( it was due for a rebuild )

On a side note is that sub going to run a dual spider assembly?

[SabreWulf69]

Dear christ, that is one busted ass sub.

[STEvil]

@STEvil
Are you making your own subs dude?
If so, where are you getting all your parts?

I've only see replacement parts when looking for cerwin vega stroker series subs...
Usually only the cone or surround parts.

I've love to be making my own subs and selling them locally as well.

The wire and coating for that I know of, but the cones and dust covers, surrounds(prefer dual rubber), chassis I guess you could call it and the magnets I don't have a clue where to get from.
Magnets I suppose I could figure out something but everything else I'm unsure of.

fixmyspeaker.com and a few other websites offer cones, baskets, motors (magnet structures), coils, and spiders.

Yes, I will be building a few in a while. I'm working out the specifics of what I need still though.


Hah looks like that sub bottomed out in a hard hard way.

That is just pure ugly, what the heck did they do.

I never managed to do that even when I ran a 20hz sine wave on a sub in a tuned enclosure for 52hz just to put it out of its misery after a 2 year comp strek ( it was due for a rebuild )

On a side note is that sub going to run a dual spider assembly?

I think it got hit with some serious clipping. There were 4 amps on it at the time (2 subs 8 amps total) and it was being fed about 7-8KW.

The black one up top is being made by foreverbumpn on http://www.stevemeadedesigns.com/ and is dual motor and dual separated coils with dual or more spiders.


Dear christ, that is one busted ass sub.

its the worst i've seen lol. Seriously, a hole right through the former (actually there's 2 holes!).. wow.

[chew*]

The black one up top is being made by foreverbumpn on http://www.stevemeadedesigns.com/ and is dual motor and dual separated coils with dual or more spiders.


Since i don't do this anymore i will live vicariously through you :up:

Keep us updated.

[STEvil]

I've got a blazer with some cement poured in the floor and interior gutted. Problem is I dont have anywhere to keep it so its in town at a local audio shop.. haha.

[chew*]

I've got a blazer with some cement poured in the floor and interior gutted. Problem is I dont have anywhere to keep it so its in town at a local audio shop.. haha.

Sound like my old CRX, it lived at my local audio shop. It had an auto tranny and lugging all the weight was making it slip, couldn't afford to trailer it to shows so it just sat there as a demo vehincle :(

Live and learn, all future spl cars had standard traniies.

I wonder what that sub would do in my little festiva. I should take pictures of it, we took it to one show and tossed a box in it quick just to get a baseline and to see what frequency peaked best in it.

My buddy who ran the SLAP events wrote all over it with one of those marker pens.

"It was this or the bus" on the side fenders he wrote "1.0 dual overhead hampster"

Do you follow the USAC events still online? Is my fellow New Englander Big Bob Sandford ( team 420 ) still beating up that blue van of his.

[STEvil]

Bob Perillo? Not sure, I only see stats to 2009. Was running 180KW it looks like.. wow! :D

http://www.youtube.com/watch?v=Ul9tmSpQ51g

[chew*]

Bob Perillo? Not sure, I only see stats to 2009. Was running 180KW it looks like.. wow! :D

http://www.youtube.com/watch?v=Ul9tmSpQ51g

Yep thats Bob, I forgot his last name isn't sandford, thats his partners name.

My Team mate looks like he held his own in 2009 it seems. Michael Gladu.

Our team was TEAM RENOTS, spell that backwards :)

[STEvil]

Poor mike.. lol http://www.youtube.com/watch?v=W0yoZarML2M

speaking of amps, was just down to the border to pick this up today ;)

http://i216.photobucket.com/albums/cc232/STEviltoo/Amps/warhorse.jpg

bigger picture: http://i216.photobucket.com/albums/cc232/STEviltoo/Amps/warhorse-1.jpg

[chew*]

Pure :banana::banana::banana::banana::cool:

[STEvil]

Surprisingly cheap too. $1500 for 10KW, cant complain.

[chew*]

Surprisingly cheap too. $1500 for 10KW, cant complain.

Got a break down on the nitty gritty specs?

Here was the amp's I used to use, mainly chosen so I could compete in a certain wattage class. Cheater amps if you will.

God I loved those 2 amps. Never caught on fire like Mike's MA's :p:

http://www.sonicelectronix.com/item_2349_Kicker-KX1200.1-KX-Series-04KX1200.1.html

Went through about 8 of em, felt like i was binning cpu's.........in the end we found 2 cherry amps which were capable of running strapped with the MOJO quad 1 ohm wired for 1/4 ohm.

Mind you they couldn't run this way sustained for very long, just needed them to hold long enough for a burp though. Others we tested couldn't hold the note long enough :(

I was running a rack of kinetik's just to feed them, Dual 1/0 runs from the front to feed the rack.

Eclipse headunit, was the only thing we could find that wouldn't skip installed in the car without having to have a remote station.

I used a pheonix gold Bass CUBE, for the crossover and cut off, simple but effective.

I still have my box in the garage, was 4 layer 3/4 MDF all around with the face 6 layer, port is painted pink :p: Lost a bet with the 420 guys once :ROTF:

[STEvil]

Got a break down on the nitty gritty specs?

http://www.kicker.com/warhorse

10KW @ 2 ohm
5KW @ 4 ohm

~90% efficiency. :up:

Still listed on their website as $10,000.. lol :)


Here was the amp's I used to use, mainly chosen so I could compete in a certain wattage class. Cheater amps if you will.

God I loved those 2 amps. Never caught on fire like Mike's MA's :p:

http://www.sonicelectronix.com/item_2349_Kicker-KX1200.1-KX-Series-04KX1200.1.html

Went through about 8 of em, felt like i was binning cpu's.........in the end we found 2 cherry amps which were capable of running strapped with the MOJO quad 1 ohm wired for 1/4 ohm.

Mind you they couldn't run this way sustained for very long, just needed them to hold long enough for a burp though. Others we tested couldn't hold the note long enough :(

I was running a rack of kinetik's just to feed them, Dual 1/0 runs from the front to feed the rack.

Eclipse headunit, was the only thing we could find that wouldn't skip installed in the car without having to have a remote station.

I used a pheonix gold Bass CUBE, for the crossover and cut off, simple but effective.

I still have my box in the garage, was 4 layer 3/4 MDF all around with the face 6 layer, port is painted pink :p: Lost a bet with the 420 guys once :ROTF:

I've got a ZX750.1 (750 rms @ 2ohm) in my daily ride at the moment. I've run it down to 0.65 ohms and it stood up like a champ other than browning the pair of 40A fuses I put on it in place of the stock 30A's it took. Its one of my favorite little amps, right next to my old Rockford 200a2. Abused the crap out of it and it never gave me a problem :)

As to anti-skip with a cd player, just mount it with springs! lol :)

[[DANGERDAN]]

Impedance change (rise and dip) are due to excursion. More excursion means more power required.

Impedance change is due to Inductive Reactance, major rise and dips are because of resonance with driver design/materials and enclosure setups.
Excursion does not change impedance frequency does, increased volume raises the excursion level but does not change the impedance only the required power demand.

Smaller speakers are more efficient than larger speakers (free air resonant only), they move less air and have higher power to SPL output.

Sabrewulf.
I have just started reading loudspeaker design cookbook by vance, I took a lot of research with me before i went on to reading this. Even studying physics helps.

[STEvil]

Inductive reactance is a function of current and voltage (and distance and time...) applied to the voice coil. Rise and dip are caused by excursion since excursion changes the applied field strength of the motor structure (via movement and static position in the motor field). As an additional note of interest, I have not researched time (period) as a function of waveform (sine vs square) with fixed power but I suspect it may have further implications on impedance curves.

Frequency can apply an additional resonant (harmonic) waveform and it is heard (and can be measured) as distortion in actual output. The inductive load that harmonics apply to the coil are actually rather small. At and above the tuning frequency of the enclosure they exist because the helmholtz effect acts as a spring to keep the coil in a normal flux of movement in the magnetic field provided by the motor. Once you get below the tuning frequency of the enclosure excursion increases which allows the field to weaken thanks to the coil leaving the gap further (and for a longer time length).

Now, thats not to say what is written in the cookbook is wrong, but that current (applied) technology and theory have not progressed when talking coil-propelled drivers.

The guy I mentioned earlier (Forevrbumpn) has built some really neat prototypes though.. :) http://www.youtube.com/watch?v=rmRYTQAS7W4


edit - interesting thought, aluminum inductiveness by movement..

[[DANGERDAN]]

Inductive reactance is a function of current and voltage (and distance and time...) applied to the voice coil. Rise and dip are caused by excursion since excursion changes the applied field strength of the motor structure (via movement and static position in the motor field). As an additional note of interest, I have not researched time (period) as a function of waveform (sine vs square) with fixed power but I suspect it may have further implications on impedance curves.
As i understand it inductive reactance is a mechanism (might not be the right word) generated within a inductor (coil of wire) that changes it's opposition to current flow proportional to the change of ac current or inductance which is just a increase of current itself i would assume, so i was correct in stating that frequency changes inductive reactance.
This is what is naturally done with a inductor, how crossover/filters are made and also what makes speakers reactive load transducers. Take away all resonant factors in a speaker coil and you essentially just have a straight forward inductor and will always see a rising impedance proportional to the increase/change of frequency or inductance. The impedance is never linear across the changing properties involved of what i think is called faradays law or whas is lenz law ?. I don't remember or know exactly but they both had something to do with inductive reactance. So coming back to rise and droops i assume they are because again of resonances but explaining how those resonances cause a change in the inductive reactance is exactly what you stated in your previous post about field strength change due to excursion.


Frequency can apply an additional resonant (harmonic) waveform and it is heard (and can be measured) as distortion in actual output. The inductive load that harmonics apply to the coil are actually rather small. At and above the tuning frequency of the enclosure they exist because the helmholtz effect acts as a spring to keep the coil in a normal flux of movement in the magnetic field provided by the motor. Once you get below the tuning frequency of the enclosure excursion increases which allows the field to weaken thanks to the coil leaving the gap further (and for a longer time length).
I am not sure what this is relating too, i can only guess your speaking of the reason resonance with porting causes the effects of impedance change due to the coil leaving the gap more and being less efficient, could this be the reason for impedance dips ?.


Now, thats not to say what is written in the cookbook is wrong, but that current (applied) technology and theory have not progressed when talking coil-propelled drivers.
I have only just started and will expect to reread it.Iv only just started lol


The guy I mentioned earlier (Forevrbumpn) has built some really neat prototypes though.. :) http://www.youtube.com/watch?v=rmRYTQAS7W4
I see your interest in extravagant non high fidelity car audio systems, i assume it's more of a hobby and interest to put your knowledge somewhere rather than pursuing to perfect what you already know. I understand the passion but i do not commit that this type of use with audio technology is for musical enjoyment, its not my cup of tea. But i don't disagree that it is some form of music whether it is misrepresentation of the intended use or not, if people like it then that should not be judged.



edit - interesting thought, aluminum inductiveness by movement..

Not a clue, might look up what your saying later on xD.

[STEvil]

off to watch iron man 3, will reply when I get back (a little over 3 hours from now probably).. ;)

[[DANGERDAN]]

off to watch iron man 3, will reply when I get back (a little over 3 hours from now probably).. ;)

Seen that the other day myself, was quite good considering most part 3 movies can be quite underdone.

[STEvil]

I was unimpressed by how the extremis bit was incorporated.. :( Good other than that though.


As i understand it inductive reactance is a mechanism (might not be the right word) generated within a inductor (coil of wire) that changes it's opposition to current flow proportional to the change of ac current or inductance which is just a increase of current itself i would assume, so i was correct in stating that frequency changes inductive reactance.

http://www.allaboutcircuits.com/vol_1/chpt_15/1.html

With current being applied, voltage (frequency) will act as as sine wave if you graph it, when there is no magnetic field present. When the coil is in the gap there is a pre-existing magnetic field which reduces this effect. If the coil is outside of the gap the "sine" wave becomes much more like a square wave since the inductive field being generated is no longer contained. To say that the impedance is changing may be a technical misnomer as you could possibly better characterize it as charge/discharge rates of capacitors.

Back EMF (Lenz/Faraday's law(s)) is the collapse of the inductor-motor circuit as the coil enters or leaves the magnetic gap, which is time/distance related to the charge/discharge cycle of the coil, which is induced by excursion... Voltage/current are related to the time/excursion since they affected the charge/discharge cycles of the voice coil. Lower frequencies often use more excursion to produce the same output level so the charge/discharge cycle of the coil is lengthened significantly, along with secondary EMF (which can be seen as harmonics).

My interest in "extravagant" is to improve what exists, unlike what the rest of the industry seems to be doing. The Audio scene has stagnated for the last 50 years :(

[[DANGERDAN]]

I was unimpressed by how the extremis bit was incorporated.. :( Good other than that though.



http://www.allaboutcircuits.com/vol_1/chpt_15/1.html

With current being applied, voltage (frequency) will act as as sine wave if you graph it, when there is no magnetic field present. When the coil is in the gap there is a pre-existing magnetic field which reduces this effect. If the coil is outside of the gap the "sine" wave becomes much more like a square wave since the inductive field being generated is no longer contained. To say that the impedance is changing may be a technical misnomer as you could possibly better characterize it as charge/discharge rates of capacitors.
Ok so the pre-existing magnetic field changes the natural characteristics that a standard inductor would have and thereby changing the overall reactance value over the frequency, i guess that makes sense because a normal inductor is linear across the proportional change of frequency where as the impedance graphs for voice coils is very.. well reactive. I will have to do some research on the square wave relationship and how it affects things, although i am still being beaten by phase relationship of voltage/current. It just beats me to death trying to understand how you get current and voltage at different phases on the same conductor/circuit. I know i am missing something i always do.

To sum up however frequency does change the impedance (due to reactance) and rise and dips are because of excursion (induced by third party influence like resonance) BUT!, if excursion were the reason for rise and dips. Why is it that when you increase the volume (which increases excursion) that the impedance does not change, because it doesn't. Only changes the power demand required by the amplifier.
I'm guessing it's because the back emf is not changing due to free space resonance, when the speaker is hitting its Fs area.



Back EMF (Lenz/Faraday's law(s)) is the collapse of the inductor-motor circuit as the coil enters or leaves the magnetic gap, which is time/distance related to the charge/discharge cycle of the coil, which is induced by excursion... Voltage/current are related to the time/excursion since they affected the charge/discharge cycles of the voice coil. Lower frequencies often use more excursion to produce the same output level so the charge/discharge cycle of the coil is lengthened significantly, along with secondary EMF (which can be seen as harmonics).
Ah secondary EMF this is interesting.


My interest in "extravagant" is to improve what exists, unlike what the rest of the industry seems to be doing. The Audio scene has stagnated for the last 50 years

I was going to disagree but then i thought i would reword it, i would'n't say the audio scene has stagnated (claiming all of audio technology) but i would put that statement towards speaker technology only hoping that was what you were referring to. We are still using the same type of speaker technology but only improving on what we have like you said as there is no replacement to superseed voice coil technology. Maybe electrostats but they are problematic i think atm.

Hey what kind of engineer are you, i remember someone saying you were but i never caught what type. ?

[STEvil]

Research AC voltage to understand multi-phase (2,3,6) voltage ;)

When increasing volume are you using a fixed tone or a varying tone? When you use a fixed tone the system (coil-motor-etc) operates at a steady state which is measured as "unchanged." If you measured from a full uncharged rest to full discharged stop you might see something different though. If you use changing tones (music), transients, and a few other items you will have a large change in the drivers performance. For example with music you could be producing a 60hz tone at one moment then 30hz at the next and could be at any step of power (speaking about subwoofers). This change could happen at any point in the travel of the coil so you may be sending full power to the driver at either an already full field (deep in the magnet) or at nearly when the coil is out of the gap.

When you think about it, its pure luck that speakers sound as good as they do ;)

Yes, mostly just speaker technology, though there arent many amp companies pushing to change things. Class J amps are interesting, but technically it takes two of them to be sonically the same as a Class A or A/B amp.

Not an engineer, that I know of that is.

edit - Sorry if anything sounds a bit complicated in there, just woke up after over 100 hours work in the last 6 days..

[[DANGERDAN]]

Research AC voltage to understand multi-phase (2,3,6) voltage ;)
I actually plan to be a electrician, i have researched all about AC/DC theory, physics, semiconductors, digital theory. Sites like All About Circuits (http://www.allaboutcircuits.com/) and Lessons In Electric Circuits (http://www.ibiblio.org/kuphaldt/electricCircuits/) I have read top to bottom. Also watched all lectures by Richard A. Muller about physics, about 26 lectures in C10 that go for about a hour each. Also lectures from elec 110 and some of elec 120 for electronics by joe Gryniuk from lake washington tech college. On top of that just general research for filling in gaps like this topic we are on :).

You don't know any good websites like i have linked that are any good ?.



When increasing volume are you using a fixed tone or a varying tone? When you use a fixed tone the system (coil-motor-etc) operates at a steady state which is measured as "unchanged." If you measured from a full uncharged rest to full discharged stop you might see something different though. If you use changing tones (music), transients, and a few other items you will have a large change in the drivers performance. For example with music you could be producing a 60hz tone at one moment then 30hz at the next and could be at any step of power (speaking about subwoofers). This change could happen at any point in the travel of the coil so you may be sending full power to the driver at either an already full field (deep in the magnet) or at nearly when the coil is out of the gap.
I am talking about pure sine wave only to keep things simple (sine wave sweeps are mostly used when graphing a impedance plot) but i do understand the complexity's when multiple sound waves are summed together and/or instantaneous frequency change.



When you think about it, its pure luck that speakers sound as good as they do ;)Quite a lot i have thought that when looking at the research, sometimes you just laugh as to think that if one simple thing was not in existence that speakers would fail to work.



Yes, mostly just speaker technology, though there arent many amp companies pushing to change things. Class J amps are interesting, but technically it takes two of them to be sonically the same as a Class A or A/B amp.Have not researched other classes yet, i have seen plenty of other patented technology's too though like class Z. Problem with patents though is that it sometimes holds back technology.



Not an engineer, that I know of that is.
Whats your profession if that's ok to ask ?



edit - Sorry if anything sounds a bit complicated in there, just woke up after over 100 hours work in the last 6 days..
Na i understand it pretty well, maybe in the past i was always getting confused, specially when i couldn't grasp impedance a couple years back. But iv come along nicely i think.

[STEvil]

No sites off the top of my head, I just tend to stumble around the web reading material as I find it.

Profession is farming and anything related (welding, class 1 truck driving, agronomy, etc..). Electronics is a surprisingly handy skill to have as well when you need to fix something out in the middle of the field and the boss(es) and repair reps sent from the dealership of the item all dont know how it works, lol.

[[DANGERDAN]]

No sites off the top of my head, I just tend to stumble around the web reading material as I find it.

Profession is farming and anything related (welding, class 1 truck driving, agronomy, etc..). Electronics is a surprisingly handy skill to have as well when you need to fix something out in the middle of the field and the boss(es) and repair reps sent from the dealership of the item all dont know how it works, lol.

Ah really I work/live on a farm also, its a dint of a life sometimes haha.