Impossible car audio challenge?

[Antichrist]

lol thanks bro.

 

Sub is all packaged up, I'll be sending it back tomorrow to Amazon. I'm going to consider it faulty.

 

So I'll be shopping for a new sub in the near future :-/

[NoGooD]

Subs do not blow with too little power. If this was the case, every time you turn the volume down, your subs/speakers would blow.

I had forgotten the exact reason, so admittedly I had to look it up again. You can blow a sub with an underpowered amp if the amp is pushed beyond what it can appropriately reproduce the frequency at. I think this article explains it better than I ever could.

 

Power Overload and Distortion

 

Amplifier plays a crucial role in safe operation of a speaker. An amplifier can cause the speakers to blow when it sends too much power to the speakers, or because of clipping and Total Harmonic Distortion (THD) due to the power limitations of the amplifier itself.

 

Contrary to common opinion it is not safe to use a low powered amplifier. While it wont overload the speaker with power directly, it will itself be unable to reproduce certain sound levels without distortion, and this distortion can be just as damaging to the speakers.

 

Clipping occurs when an amplifier tries to reproduce higher amplitudes of sound than it is made to handle. It then “clips” the tops and bottoms of the sound waves, distorting them. Distortion in turn causes speakers to move in an abnormal fashion, potentially causing them to blow.

Best Practices

 

Here are a few tips to help you make sure you don’t blow your speakers:

 

Avoid distortion at all costs. If you hear distortion (and it is not part of the music itself, like a distorted electric guitar sound), turn the volume down.

Make sure to use the right amplifier with your speakers, ones that can send an undistorted sound at all sound levels that your speakers can handle. It is generally more advisable to use amplifiers that can provide more power than you need, so long as you don’t overpower your speakers. If you’re unsure use active speakers, with already built in amplifiers, and avoid turning the volume up more than necessary.

Avoid plugging or unplugging the speakers from the sound source (like a sound card) or a power outlet while they are still turned on, and especially if the volume is turned up. This can cause a loud hum or jolts of electricity that could harm the speakers.

Source

 

I've done this myself in the past. Had a good quality sub that was powered by a mid quality amp and ended up blowing it. Amazingly enough when I bought a better amp and the same sub..it sounded much better and could be turned up louder. I scratched my head on it til a buddy of mine that worked at an audio shop explained it to me. Not sure if this is what happened in your situation but I figured it might be a cause.

 

Edit: Also here is a pretty interesting thread with some replies by Manville Smith, VP of Marketing @ JL Audio

Edited August 29, 2011 by NoGooD

[Antichrist]

NoGood That's great info there, thanks for sharing

 

I'm not sure that was my problem though. It could be a few things.. but the exact cause is bothering the hell out of me.

 

The amp is a JBL GTS 180x. http://www.crutchfield.com/S-aaVZzES5LM8/p_109GTS180X/JBL-GTS180X.html

 

It's probably about 10 years old, and hasn't seen much use in the time I've owned it. It's nowhere near Audiophile quality. But it's also FAR from walmart 'roadgear' quality too.

 

Since this whole thing began as me trying to outdo my girlfriend's 2 12"s and 500-600 RMS, with a single 12, and 180 RMS, here's how it went down.

 

I have an old bass CD. You know the one. Woofercooker. Yep.

 

Played it in her car, nice rumble. So we headed over to my truck. Same CD. I turned on the same song. The sine sweep went fine at the beginning of the song. I had my volume at 25, which is the max I've ever used. Then the song goes into some real low frequency bass, maybe 28hz or so? That's where the crackle, buzzing, etc... occured..

[NoGooD]

NoGood That's great info there, thanks for sharing

 

I'm not sure that was my problem though. It could be a few things.. but the exact cause is bothering the hell out of me.

 

The amp is a JBL GTS 180x. http://www.crutchfield.com/S-aaVZzES5LM8/p_109GTS180X/JBL-GTS180X.html

 

It's probably about 10 years old, and hasn't seen much use in the time I've owned it. It's nowhere near Audiophile quality. But it's also FAR from walmart 'roadgear' quality too.

 

Since this whole thing began as me trying to outdo my girlfriend's 2 12"s and 500-600 RMS, with a single 12, and 180 RMS, here's how it went down.

 

I have an old bass CD. You know the one. Woofercooker. Yep.

 

Played it in her car, nice rumble. So we headed over to my truck. Same CD. I turned on the same song. The sine sweep went fine at the beginning of the song. I had my volume at 25, which is the max I've ever used. Then the song goes into some real low frequency bass, maybe 28hz or so? That's where the crackle, buzzing, etc... occured..

 

Actually bro that makes perfect sense. Like you said before you were shooting for a frequency of 33-35hz. In a ported box once the frequency drops below the threshold of the box design, the power handling drops like a rock due to speaker over-excursion. It's one reason I used to run sub-sonic filters. Again since it's been ages since I've screwed with this stuff so I did some digging around and found a better explanation than I can provide. Hope this helps man.

 

This is from http://en.wikipedia.org/wiki/Bass_reflex

Another trade-off for this augmentation is that, at frequencies below 'tuning', the port unloads the cone and allows it to move much as if the speaker were not in an enclosure at all. This means the speaker can be driven past safe mechanical limits at frequencies below the tuning frequency with much less power than in an equivalently sized sealed enclosure. For this reason, high-powered systems using a bass reflex design are often protected by a filter that removes signals below a certain frequency. One such filter is the rumble filter often built in to receivers or amplifiers designed to be used with LP records because of undesired LF rumble from the mechanical parts of the turntable, or from the strong subsonic excitation caused by warped vinyl discs. Unfortunately, electrical filtering adds further frequency-dependent group delay. Even if such filtering can be adjusted not to remove musical content, it may interfere with sonic information connected with the size and ambiance of the recording venue, information which often exists in the low bass spectrum.

[Antichrist]

Well that makes sense.. unfortunately.

 

I never put any thought into what happens to the sub below frequencies that the enclosure is tuned for. Ah well.. live and learn.

 

I'm still leary about buying another Power Acoustik PEN 12W, and since I already have a 2.0^ft box built, I'm most likely just going to cut out the baffle, put a new one in its place, and go sealed so I don't have this problem again.

 

None of my music drops below 33-35hz, so I figured that tuning would be fine. I didn't take into account, that I'd probably try a bass CD to compare to my girlfriend's system.

 

Right now I'm considering the MB Quart ONX302 http://www.sonicelectronix.com/item_33009_MB-Quart-ONX302.html

 

I prefer the dual 2 ohm coils over the single 4 ohm coil, which would allow me to run the sub at 4 ohms series, or run each 2 ohm coil independantly to the amp.

 

EDIT: I'll most likely go 4 ohm series, and bridge the amp. I thought that 2 ohm stereo (90x2) would give me lower THD than running 4 ohm bridged, but I just looked up the specs, and both have .08 THD.

 

Specs sheet: http://www.nodevice.com/manual/newmans/jblharman/GTS180X_smpdf/get46885.html

[TulsaGeoff]

 

Time to bump up the toughness of your sub. Better safe than sorry. It can handles 3000watts all day long and probably upwards of 6000 for your GF competitions.

 

http://www.ddaudio.com/mobile-audio/woofers/z-series.aspx

[NoGooD]

@Anti: It probably wouldn't hurt to invest in a subsonic filter just as a precaution. I know it's gimmicky but the LED's on that MBquart are pretty sweet.

 

@Tulsa: lol..Holy crap. That sub is nuts. You'd need a forklift just to pick it up.

[Fogarty]

you should look for rockford fosgate, punch series, or power series, not too expensive, and even with a low rms power from the sub, it bangs like hell+ my sub wich is a rockford fosgate Punch P215S4 is 250w rms and 500w max however i've got this as a present from my brother in law, it has been in hes car for 2 years and it was overpowered by 2000 watts, otherwise its been banging for quite a long time on 2500watts rms and it's not blown, only problem was that the wires connected to the voice coil we're to short because the excursion was quite to much, jsut like the surround broke by that xd meanwhile it's refoamed with a wider extension for the flex and long wires^^ anyway its not too expensive, you should take a look