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Thread: Woofer size and power usage.

  1. #26
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    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.

  2. #27
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    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...

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  3. #28
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    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.
    Last edited by chew*; 02-12-2011 at 11:56 AM.
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  4. #29
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    4KW is childs play these days

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

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  5. #30
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    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.


    - 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

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

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  6. #31
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    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

    All along the watchtower the watchmen watch the eternal return.

  7. #32
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    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.

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  8. #33
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    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.

    All along the watchtower the watchmen watch the eternal return.

  9. #34
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    Quote Originally Posted by STEvil View Post
    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".
    heatware chew*
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  10. #35
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    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.

    All along the watchtower the watchmen watch the eternal return.

  11. #36
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    I mean I would like a rating of continuous square wave handling power, not an every now and then peak power rating.

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  12. #37
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    Why would you want to feed that kind of signal? I would sound horrible.

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  13. #38
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    Just to know 100%, that if anything ever clips, my equipment won't get damaged.

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  14. #39
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    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):

    All along the watchtower the watchmen watch the eternal return.

  15. #40
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    Small bump.. pulled apart a dead 18" sub rated at 5,000w RMS today...



    and... wow.


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  16. #41
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    @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.

  17. #42
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    Quote Originally Posted by STEvil View Post
    Small bump.. pulled apart a dead 18" sub rated at 5,000w RMS today...



    and... wow.

    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?
    Last edited by chew*; 02-20-2011 at 01:12 PM.
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  18. #43
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    Dear christ, that is one busted ass sub.

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  19. #44
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    Quote Originally Posted by NEOAethyr View Post
    @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.

    Quote Originally Posted by chew* View Post
    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.

    Quote Originally Posted by SabreWulf69 View Post
    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.
    Last edited by STEvil; 02-20-2011 at 07:07 PM.

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  20. #45
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    Quote Originally Posted by STEvil View Post
    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

    Keep us updated.
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  21. #46
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    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.

    All along the watchtower the watchmen watch the eternal return.

  22. #47
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    Quote Originally Posted by STEvil View Post
    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.
    Last edited by chew*; 02-21-2011 at 02:06 AM.
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  23. #48
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    Bob Perillo? Not sure, I only see stats to 2009. Was running 180KW it looks like.. wow!

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

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  24. #49
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    Quote Originally Posted by STEvil View Post
    Bob Perillo? Not sure, I only see stats to 2009. Was running 180KW it looks like.. wow!

    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
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  25. #50
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    Poor mike.. lol http://www.youtube.com/watch?v=W0yoZarML2M

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



    bigger picture: http://i216.photobucket.com/albums/c...warhorse-1.jpg

    All along the watchtower the watchmen watch the eternal return.

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