Is my sub blown?

[virtuetovice]

Well about a week ago, I scored a 15" Kicker CompVR and Rockford Fosgate 201S amp for the best price there is.

The amp SAYS "600 watts" on the case. Load of bs considering the RMS is 50x2, and the bridged power is 200, both according this page on crutchfield.com. http://www.crutchfield.com/S-oJPx23p...ml#details-tab

The subwoofer is a Kicker CompVR C15D. 4 ohm, 500-600 peak power depending on where I'm reading.

So anyway, I got everything hooked up and the sub worked for a little bit but as I cracked it up, it acted as if that piddly little amp just wasn't enough. I kept messing around with the amp and it eventually overheated and that smell of blown electronics engulfed my car. Since then, I snagged this off craigslist:

http://www.crutchfield.com/S-087MYcj...hn-A8000T.html

400 watts RMS. Much better than those piddly 50 from that last amp right? Not so much. I'm getting hardly anything out of this subwoofer.

IS there any way for sure to tell whether the "new" amp is blown or is it my sub? The guy I got the amp from buys storage units. Real cool older guy, very old fashioned and said he'd have no problem taking it back if it is found to be defective.

[virtuetovice]

Never mind. Hooked it up to the surround sound and got hardly anything. I decided to dissect it and those coils were SCORCHED! Half of them were fused to the magnet in the bottom. Oh well...

[RobertISaar]

so you went from a free amp and subwoofer to needing to replace both now?

[xtremerevolution]

so you went from a free amp and subwoofer to needing to replace both now?

Amp is probably fine. Not like it's worth anything though for subwoofer duty.

What happened is you clipped the sub and exceeded the thermal limitation of the voice coil. I'm 100% sure of it. The RF amp you got is good for front components, not subwoofer use. At 4ohms, that's good for 100W RMS on a good day. I would highly recommend you read the following before proceeding. If you've chosen your components wisely, you'll bottom out the former and hammer the back plate (making loud smacking sounds) of a good subwoofer before you ever thermally fry the voice coil.

The only thing that thermally damages speakers is power... more specifically: average power over time.

I'll explain...

If you take a given amplifier, let's say 100 watts and operate it just below clipping with music material, the "Crest Factor" of the amplifier's output is equivalent to the "Crest Factor" of the program material.

"Crest Factor" is the difference between the average level of the signal and its peak level. For example, a pure sine wave has a "crest factor" of 3dB, meaning that it's peak level is 3dB higher than its average level. We all know that 3dB represents a power factor of 2, so another way to look at it is that the peak power of the signal is twice that of its average level. So, if we play a sine wave on our 100 watt amplifier, just below its clipping level, the average power (over time) the speaker is needing to dissipate is 50 watts.

A true square wave, by comparison, has a crest factor of 0db, so it has equal average and peak power. Our 100 watt amplifier, playing a square wave, unclipped, into our speaker requires that the speaker dissipates 100 watts of power (twice the heat as a sine wave).

Music has a significantly higher crest factor than sine waves or square waves. A highly dynamic recording (Sheffield Lab, Chesky, etc.) typically has a crest factor of 20dB or more, meaning that its average power is 100 times lower than its peak power. So, if we play our 100 watt amplifier just below clipping with the typical audiophile recording our speaker is only needing to dissipate 1 watt of average power over time.

Modern commercial recordings typically exhibit crest factors of around 10dB, meaning that the average power is 10 times lower than the peak power. So, our 100 watt amp just below clipping would deliver an average power over time of 10 watts that the speaker has to dissipate.

Okay, so what happens when we clip the amplifier (which we all do at times). When the amplifier enters into clipping, the peak power no longer increases, but here's the KEY... THE AVERAGE POWER CONTINUES TO INCREASE. We can often tolerate a fair amount of clipping... as much as 10 dB or more above clipping with a reasonably dynamic recording... a bit less with a compressed commercial recording.

So, if we turn the volume up 10dB higher than the clipping level with our Sheffield Lab recording, we have now reduced the crest factor of the signal reaching the speakers by 10dB... so instead of needing to dissipate 1 watt average, we are asking the speaker to dissipate 10 watts average, and we're probably ok.

If we turn up the volume 6dB past clipping on a compressed commercial recording (or bass music recording), we have taken the crest factor of the signal from a starting point of 10dB to only 4dB, asking the speaker to dissipate an average power of 40 watts instead of 10 watts... that's FOUR TIMES the average power, which generates four times the heat.

SO, in most cases, the reason clipping can damage a speaker really has nothing to do with anything other than an increase in average power over time. It's really not the shape of the wave or distortion... it's simply more power over time.

When someone plays Bass Mekanik clean (unclipped) on a 1000 watt amplifier the average power is 100 watts (10dB crest factor). You can also make 100 watts average with Bass Mekanik by heavily clipping a 200 watt amplifier.

If someone is blowing a woofer with 200 watts of power due to a lack of restraint with the volume control... they will blow it even faster with a 1000 watt amplifier because they will probably turn it up even more and now they have more power to play with... this is the recipe for aroma of voice coil.

When woofers are rated for power, an unclipped signal is assumed. We use test signal with a crest factor of 6dB for power testing and can run a speaker at its rated power for hours and hours on end without thermal or mechanical failure. For example, a W1v2 can dissipate 150 watts average power for eight hours or more with signal peaks of 600 watts. So, we rate the speaker for 150W continuous power. This way, when a customer needs to choose an amp for it, they will hopefully choose one that can make about 150 W clean power... Even if they clip the bejeezus out of that amplifier, it is unlikely that the speaker will fail thermally. This is a conservative method, but it needs to account for the high cabin temperatures in a car (think Arizona in the summer) which significantly impacts heat dissipation in the speaker. A top plate that starts at 150 degrees F is not as effective at removing heat as one that starts at 72 degrees F in the lab... and this affects the ramp up of heat in the coil.

DISCLAIMER: The frequency components of clipping can affect tweeters due to their low inductance and lack of low-pass filtering. Clipping essentially raises the average power of high frequencies to a point that can damage tweeters... Woofers and midranges couldn't care less about these high frequency components because their filtering and/or inherent inductance knocks that stuff out of the picture.

Best regards,

Manville Smith
JL Audio, Inc.

http://www.audiogroupforum.com/csfor...11&postcount=6

[virtuetovice]

Well I'm in the market for a new 15 inch...suggestions? Probably gonna end up using that Audiobahn 1600W...took it to a few different car audio places and asked the basic question of "is this junk or is it a good amp?" and got consistent "yeah audiobahn makes good stuff".

[xtremerevolution]

Well I'm in the market for a new 15 inch...suggestions? Probably gonna end up using that Audiobahn 1600W...took it to a few different car audio places and asked the basic question of "is this junk or is it a good amp?" and got consistent "yeah audiobahn makes good stuff".

Are you going to build a new box, or are you looking for a 15" just to fit in an already existing box? If so, how well built is this box, and what are the dimensions (including port dimensions if available)? What's your budget for the 15?"

For the record, Audiobahn is more on the low and midrange of car audio. Very flashy and generally not geared for sound quality. Quality equipment is generally always CEA-2006 certified. I don't believe Audiobahn amps are CEA-2006 certified.

[1988PhantomFE3]

I don't know if your SUB is blown, but mine has multiple blowers on it!

[Addicted2bass]

I second everything Andrei said. You clipped the hell out of that amp and took out the sub. I'm not sure what shops you're going to but I would not say Audiobahn makes "good" stuff. Its not garabage, but not really good either, I've always refered to them as Audioburn. That being said, that amp should be fine to push one 15. Just keep in mind that the amp is only 2 ohm stable so make sure to get a DVC 4 ohm sub.

[Jonathan_C]

Don't worry about the CEA-2006 stuff. First off, it's a voluntary system that only allows for the RMS wattage and harmonic distortion figures to be verified. I would worry more about build quality than the power output anyway.

[xtremerevolution]

Don't worry about the CEA-2006 stuff. First off, it's a voluntary system that only allows for the RMS wattage and harmonic distortion figures to be verified. I would worry more about build quality than the power output anyway.

While this is true, it gives you assurance that the device actually meets and performs at its intended specification. Hifonics amps used to not be CEA certified, and you'd get 1000-1200W of clean power out of their 1600W-2000W RMS rated amps on a good day, and you'd think you were getting a great deal the whole time.

There are a few small but excellent companies that sell equipment that's not CEA-2006 certified (Sundown Audio and Incriminator Audio to name two), but for mainstream use, I don't bother recommending it it if its not unless that specific amp has been bench tested.

[virtuetovice]

Well to be honest, the "Box" was a home made bass tube. It consisted of nothing more than a 15" wide plastic chemical barrel similar to this one, with a 6" wide hole cut in the side; painted black. Creative, but functional and safe for the sub?? Not exactly sure. Of course my barrel doesn't have the spigot or the black thing on top.


Buying a new sub, I probably wouldn't risk installing it in something half-assed like that unless someone more educated in audio thinks it wouldn't pose a threat.

If I WERE to build a new box, I'm pretty sure it would just take up most of the space under the rear deck in my 89 Cutlass.


@1988Phantom: Thanks for that, very funny! I'm not sure your sub would fit in my trunk

[Addicted2bass]

I guess having a sub in a barrel wouldn't hurt anything as long as there are no air leaks. But im sure it would sound like total ass.