Blown Sub - Cause?

[CzarDestructo]

So about three weeks ago I was listening to some tunes and the sub cut out, checked the 50amp fuse and it was blown. Replaced it with a 60amp fuse and everything was cool until two days ago. I'm not really terribly familiar with subwoofer design and I'm looking for some input.

 

The enclosure the sub is currently in I custom made out of fiberglass and was the first time I attempted anything like that. I had to drill a hole in the back in order to anchor it to the car. I did my best to make a good clean rubber seal between some really big fender washers but I'm worried it wasn't enough.

 

My question is could a leaking enclosure have caused my sub to blow like this?

 

10" MA Audio - 1200watt peak I think

Fosgate 500watt RMS amp, 1500 peak

 

The sub is rather old, a hand-me-down and was made in 2001. I had months of trouble free use before this and the owner before me used it for a year with this same amp. I just want to make sure my shabby enclosure isn't a sub killer before I go ahead and buy a new one.

 

Video of what the subwoofer is doing:

[ame=http://www.youtube.com/watch?v=ORigdaYNamM]YouTube - Blown sub[/ame]

[ean611]

A leaking enclosure will NOT cause a sub to break.

 

based on that video, it looks like the voice coil got damaged somehow, perhaps too much power, who knows.

 

I would suggest either a JL audio or Image Dynamics sub to replace it. It is not your box that broke the sub, all a leak will do is make it sound worse, as if the leak is porous enough, it'll act almost like a port, but not quite.

s

If you replaced a 50A fuse with a 60A, your consuming over 625w. Seeing as fuses rarely blow, your amp may have a problem. Speakers will be damaged by highly distorted high volume output of an amp.

 

 

If your amp is 500w RMS, it's reasonable for it to consume over 600w. Keep in mind, that is VERY loud, as in competition make your self deaf 120+dB loud. Those kind of volumes take their toll on subs, especially old ones.

 

Good luck, and don't fret getting a new sub, although I'll suggest you get a new amp with it. (JL Audio amps rock, I love my new 500/5)

 

EDIT: You're in Boston!! If you want help, I'll gladly look at it in person if you have some time. (I'm free all day 7/13) PM me if you'd like. I can also show you my setup, and give you some advice on sub if you're interested.

[CzarDestructo]

I'm curious now, 500W RMS does seem like it should be really loud, and yet I find that this setup wasn't that loud at all. I had the gain at 3/4 and even when the system was cranked it was never that loud. I always just assumed because it was a smaller woofer, my last system was two 12s.

 

Maybe the sub was weak all along? I think one of the coils was blown to begin with.

[icrackedcorn]

have the amp looked at by someone with fancy diagnostic stuff

[CzarDestructo]

I doubt the amp is the problem, how could an amp degrade over time? Eitherway I'm an electrical engineer, I suppose I could fiddle with it but I don't like the idea of the super high amperage.

[ean611]

CzarDestructo:

 

Could be the vibration of the car shook loose a cold solder joint. Not likely, but it is a way that the amp could have "degraded" over time.

 

By the way, I have a Kicker ZR240 and Kicker CompVR 10. (sub is around a year old, very lightly used). Both are not being used right now. If you'd like to do some experimentation with your setup, that may shed some light on what is wrong. If nothing else, the Kicker isn't a bad sub, and it's for sale, cheap. Plus, the amp isn't bad either, and it's less likely to blow up a 10" sub.

 

/Also Electrical Engineer

//Mostly digital professionally

[Underdog]

Nick,

 

I also have a 10" Polk/MOMO sub (400W rms, 800W peak) that I am trying to sell in another thread. It really is a nice sub but I just don't want/need the extra bass and weight in my car. I'd be much happier getting out of my apartment and into a friend's car.

 

Let me know...

-Rick

[CzarDestructo]

So the general consensus is that the enclosure shouldn't be the problem, its either the sub was tired or the amp itself correct?

 

Should I be dropping another sub in and risking it?

 

I took the sub out today and the spider is still connected. When I press on the center cap I hear a light scrapping noise, in case that helps.

 

edit: I should have mentioned but recently I fiberglassed a 12v fan mount and sloppily hot wired it up with a MOSFET from the accessory power, this might have caused the fuse to blow.

[Underdog]

Hmm, that is bizarre.

 

I have to disagree with ean611 though... I could definitely see a used sub of unknown condition failing due to a leaky sub box. However, I would expect to see more damage to the cone or surround rather than the internals of the voice coil.

 

Oh yeah, why don't you use that VC we made back in the day? I bet it could handle the 500W...

[ean611]

CzarDestructo,

 

your description sounds like a blown voice coil, especially with the scraping. You threw too much power at the sub and melted the voice coil. (most likely)

 

It is almost definitely NOT your enclosure.

 

Being in Boston, my offer stands, if you want another pair of eyes looking at it live. (Yeah, I spend too much time with sound...)

[CzarDestructo]

Duh, I just looked at the back of the sub, 1000W is the only label on it, I assume thats 1000W max and maybe 300-500W RMS. Maybe lower because MA Audio does seem like a lower end brand. I guess the meathead that sold it to me gave me some wrong numbers and I never bothered to check.

 

Thanks for the offer Ean but I'm in RI right now and I won't be back until later tonight. The next few days are going to be a bit busy for me so I think I'm going to have to put the sub on back burner until Thursday.

[ItalynStylion]

have the amp looked at by someone with fancy diagnostic stuff

Best.....response......ever

[whobaru]

Speaking from 8 years of car audio sales/installation experience, the enclosure wasn't the problem. Theoretically, the worst enclosure shape for air movement could cause a speaker to move irregularly, but a small hole isn't enough to affect such a large speaker. Speakers age over time. Each time a speaker is distorted, it loses part of it's life. An amp can get tired as well. This may have been a combination of a tired amp and a worn down voice-coil, but more likely it was just the woofer getting old. Amps are generally pretty solid and rarely the cause of a blown sub.

 

Note: As a woofer moves irregularly from distortion or being driven too hard, it begins to heat up. As the heat builds, the chances of a single, catastrophic event from a large, distorted bass note increase. In addition, as an amplifier heats up, distortion increases. As distortion increases, heat increases...and it snowballs. Add the summer heat in a suffocated trunk and you've got a recipe for disaster.

[ean611]

No worries CzarDestructo.

 

Just figured that you'd want to know what happened. I know that when something goes wrong, I hate not being able to get a result.

 

whobaru's response is dead on. I'm not terribly sure how to electrically describe a "tired" amp, however, chances are if you had it turned up, it may have been distorting quite a bit.

 

By the way, what is the approximate volume of your new fiberglass box? (Mostly curious, as it effects what sub you should use as a replacement)

[CzarDestructo]

If I had to guess I'd say about .5 cu ft.

 

I actually discovered a bunch of the coil wire in the bottom of the enclosure. Long 1-2" pieces. Def a toasted voice.

[ean611]

Hmmm.

 

at around .5 cu ft, you're going to have to find a special woofer that will will match such a small enclosure. Most 10 inch subs want around .75-1cu or more depending on the sub.

 

The Image Dynamics ID10 and IDQ10 are both rated to go into a enclosure as small as yours. I know there are no Boston dealers for them, but you can find them on Woofers etc.

 

The issue with subs like a JL W3 or Kicker CompVR (just two subs I'm familiar with) will be that both are designed to run in around 1 cu ft of air, so their resonance will go up quite a bit in your small box.

 

ItalynStylion recommended I try Image Dynamics, and I'm quite happy with a pair of their woofers. One of those is probably your best bet to replace your MA Audio woofer. They're also a very good bang for the buck.

[executor485]

I have a JL 12w6v2 if your looking to upgrade lol

 

FWIW, I have 2 JL 10w3's in custom fiberglass boxes mated with a 500/1 and never had any problems. The boxes probably arent a full cubic ft each, but they still hit pretty hard and havent had any blowouts yet (now that I've jinx'd myself... lol).

 

Good luck in finding some new bump

[FishingFiend]

edit: I should have mentioned but recently I fiberglassed a 12v fan mount and sloppily hot wired it up with a MOSFET from the accessory power, this might have caused the fuse to blow.

 

The sub is blown, but I believe your splice job is what's causing the fuse to blow and bring doubt to your fosgate amp. Redo the splice, replace the sub and get back to bumping. Double checking all your power/ground runs would be a safe move too.

[ItalynStylion]

Hmmm.

 

at around .5 cu ft, you're going to have to find a special woofer that will will match such a small enclosure. Most 10 inch subs want around .75-1cu or more depending on the sub.

 

The Image Dynamics ID10 and IDQ10 are both rated to go into a enclosure as small as yours. I know there are no Boston dealers for them, but you can find them on Woofers etc.

 

The issue with subs like a JL W3 or Kicker CompVR (just two subs I'm familiar with) will be that both are designed to run in around 1 cu ft of air, so their resonance will go up quite a bit in your small box.

 

ItalynStylion recommended I try Image Dynamics, and I'm quite happy with a pair of their woofers. One of those is probably your best bet to replace your MA Audio woofer. They're also a very good bang for the buck.

 

Another good option for a single 10" setup in a small airspace would be a Sound Splinter RL-i10. Plenty of punch with sound quality that will blend with anything. Very nice woofer.

http://www.soundsplinter.com/rli10_subwoofer_information.html

[MaStaMooN]

3/4 gain is no good either... usually a blown sub would equal no output(in my not so extensive experience)... so it may be the amp.. if that's not a mono amp, try running the sub on a different channel.