That was the idea. Within reason though, I'm not suggesting you can blow a 2000 watt woofer with a 10 watt amp, but hooking a 400 watt amp to a 500 watt speaker and driving it into hilarious clipping (like I hear car guys do all the time) I'd imagine is worse for the driver than having a 500 or 600 watt amp and driving to the same level without clipping.
Speaker Damage
I've modeled dozen's of drivers, 10's, 12's and 15's. I have a hard limit on the box size at about 2.5 cubes net and 16x19x22 overall. Driver cost under $200. Total weight under 60 lb. I know of no other design that meets this criteria with good sensitivity, extension to 35hz, and good headroom.
There are a few pro eminence 12's (single driver, same box) that do about the same in extension and sensitivity, but run out of xmax very quickly. There are no double 12's that would work in that size box for under $200 that I am aware of. The only thing close that I came across was the JBL GTO1214D.
http://www.diyaudio.com/forums/subwoofers/219168-help-me-build-beastly-party-sub-650-budget-3.html
http://www.jbl.com/resources/Brands...ments/en-US/BoxesandParameters/GTO1214DTD.pdf
Extreme clipping will "square out" the loudest (highest amplitude) of musical peaks, but there still is no DC component, at no point does the speaker react like it would (for example) to an input of 48 volts of car batteries alternately switched +/- polarity, where it would be "stuck" in place for whatever the cycle duration is.
For that matter, there are many synthesizer patches that are pretty close to square wave tones in some forms of music, other than the fact that they carry even more average power per amplitude than a sine wave, they won't hurt speakers.
LF clipping does tend to generate high harmonics which can roast the HF driver in a passive crossover set up.
But again, it is not clipping or "square waves" that burn out the HF driver, it is too much average power.
That said, HF drivers have very thin voice coil wire compared to a LF driver, the time constant to blow a HF driver is considerably faster than a LF driver.
LF drivers can be torn up on a huge peak, but seldom burn up, while a HF driver can burn up on a single peak.
I still am using some Eminence Kappa 10s that survived around 116 volt DC due to an amplifier power supply capacitor short circuit to ground (sounded like a shotgun!), tore the surrounds completely, but left the voice coils intact. Patched the surrounds, they work fine (and have a lower FS
)Some LF drivers are very hard to burn, because as they heat up, their impedance rises, the amp delivers less power ("power compression"), and a thermal equilibrium is reached.
Art
"I still am using some Eminence Kappa 10s that survived around 116 volt DC due to an amplifier power supply capacitor short circuit to ground (sounded like a shotgun!), tore the surrounds completely, but left the voice coils intact. Patched the surrounds, they work fine (and have a lower FS )"
That's the quick way of breaking in new drivers! ;-)
"For that matter, there are many synthesizer patches that are pretty close to square wave tones in some forms of music, other than the fact that they carry even more average power per amplitude than a sine wave, they won't hurt speakers."
If you mix two square waves whose fundamental frequencies are related 1:1.44 you approximate the sound of a cowbell and everything needs more cowbell!
That's the quick way of breaking in new drivers! ;-)
"For that matter, there are many synthesizer patches that are pretty close to square wave tones in some forms of music, other than the fact that they carry even more average power per amplitude than a sine wave, they won't hurt speakers."
If you mix two square waves whose fundamental frequencies are related 1:1.44 you approximate the sound of a cowbell and everything needs more cowbell!
I think you should go ask Nelson if a 100Hz square wave generated from a couple center tapped car batteries is fundamentally different. This is the heart of switching supplies and switching amp technology, just much much slower. No problem...
Isn't this contradictory?
Perhaps I'm missing something: so far as I can see, as soon as the amplifier is clipping, there has to be some DC component to the signal the speaker sees (ignoring passive crossovers for the moment), as (maybe only for a brief time) the amplifier output is at one of the PSU rails. More severe clipping would mean a larger DC component.
IMHO, when it comes to amplifier power, go for more power than necessary, and then have some sympathy for the drivers - you can usually tell when things are having a hard time.
Chris
Well, it looks like I've sparked a little side discussion here, so I suppose I should clarify.
The term I use conversationally is "Wow, listen to all that DC voltage!" is really a euphemism whenever I hear heinous amounts of distortion, say from a car driving by with the volume control at maximum. I understand that there are differences.
Essentially though, if you generate a 10 cycle sine wave and play it through a 500 watt amplifier with the gain controls all set to maximum so that the amplifier is absolutely buried in clipping, wouldn't the signal at the speaker be much like if you were to hook your speaker wires to a 24vdc battery and tap the positive connector to the speaker terminal 10 times per second?
The duration of the signal might be short, but if it's not sinusoidal, what is it?
If you do that to a car battery you are using its DC output to create a square wave (or pulse wave) because it changes over time.
I agree that it's a square wave and not really DC voltage, I'm just describing my thought process on referring to it as such. You can almost replicate the signal with a battery if all the conditions are right.
Hey, the reverse is true too, you could generate a dc signal and then rapidly twist the volume control back and forth to make a note! Well, half the wave form anyway.
I know where you are coming from and if you'd look at the resulting waveform through a short enough time window it would be indistinguishable from DC.
But it still is confusing and does not explain why the series capacitor in a passive highpass does nothing to protect the tweeter.
"Hey, the reverse is true too, you could generate a dc signal and then rapidly twist the volume control back and forth to make a note! Well, half the wave form anyway."
VERY coarsely speaking isn't that how amplifiers work?
Only that amps go from +xV to -xV rather than just zero.
But it still is confusing and does not explain why the series capacitor in a passive highpass does nothing to protect the tweeter.
"Hey, the reverse is true too, you could generate a dc signal and then rapidly twist the volume control back and forth to make a note! Well, half the wave form anyway."
VERY coarsely speaking isn't that how amplifiers work?
Only that amps go from +xV to -xV rather than just zero.
Harmonics would be my guess, clipped waveforms generate higher average power I think. My understanding is a little shaky.
Clipping an amp fries tweeters because it generates large current throught the voicecoil without any motion and the coil heats rapidly.
Even a 1.5v battery can fry a tweeter.
without a constantly changing current in a driver, heat builds up and melts adhesives causing failure. Dc generates heat quickly, just ask a dc motor, if you run it too slow it burns up.
Speakers are just short throw ac motors, lol!
Even a 1.5v battery can fry a tweeter.
without a constantly changing current in a driver, heat builds up and melts adhesives causing failure. Dc generates heat quickly, just ask a dc motor, if you run it too slow it burns up.
Speakers are just short throw ac motors, lol!
It is indeed harmonics. A square wave is made up of every sine wave which fits inside it at full level. So a clipped 500W bass signal will contain treble signals at 500W and no tweeter will withstand that for very long.
This can easily be shown with an analogue (subtractive) modular synthesizer like the one I've got.
Essentially you use an oscillator and then filter bits of its output out until you have carved out a sound you like.
A sine wave is no good here because it does not contain any harmonics, after the filter it is either almost unaffected or it almost completely disappears.
If however you clip the output so it resembles a square wave you can then filter it to create all sorts of metallic sounds ie you can use it to synthesize cymbals etc.
Yeah, I get a kick out of watching deadmau5's live stream he does sometimes. He's got a wall of "modcans" that he uses. It's interesting to watch how he comes up with sounds using a mile of patch cable and a room full of gear.
Etocynned,
A 1.5 volt battery would only fry an 8 ohm tweeter that is rated for .28 (or less) watts.
There may be some tweeters that would burn at that level, but even tiny headphones with smaller voice coils than any tweeter I have seen easily survive click testing with a 9 volt battery.
A clipped signal does not hold a voice coil in place, the voice coil is still very much moving if it is audible.
A DC motor does not burn up if run slow unless it is drawing too much amperage for too long. Most DC motors can be run at very low speeds by simply using less voltage.
I have a .8 horsepower DC motor I have used for (so far) an electric bike, a boat motor, and electric car, it continues to work fine even though it has been nearly stalled drawing up to 3 times it's rated amperage for a relatively short period of time. It is rated for 1700 RPM at 24 volts, it turns at 850 rpm at 12 volts.
Art Welter
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