both my subs blew?! wtf?! update - it's the amp!

[Aharami]

I have two GR Research SW-12B subs wired in parallel to a SA-1 amp. I liked this combo because I got a killer deal on them and although these subs werent super accurate, they went low and served well for my basement HT. I watched a movie Sunday night and the subs were fine. But I fired up a movie last night and found that both subs are rattling. Are they both blown? They havent been used since Sunday. Amp is set to auto on, so it turns off if no signal is detected after a while. It is plugged directly into the wall.

I am baffled as to why both subs are rattling now

 

[sm625]

You gotta be more specific than "its rattling". Inspect the cone, spider, surround, basket, etc. Find out where the rattle is coming from.

 

[Zardnok]

What sort of cabinet do you have the subs in? Sealed or Ported? If ported, what is the tuning frequency?

 

[Aharami]

i will open them up today to see whats going on. both sealed in 1.2 cu ft MDF box

 

[Zardnok]

i will open them up today to see whats going on. both sealed in 1.2 cu ft MDF box

Sealed in 1.2 should protect those speakers pretty well, especially from a low-power amplifier. Make sure the boxes are solid and don't have a side wall busted loose. A loose side wall would definitely contribute to a "rattling" sound. Other potential causes on the speaker side would be a cone disconnected from the voice coil or a loose magnet assembly. A "blown" speaker typically indicates a burnt voice coil which is a "crunching" noise instead of a "rattle". Oh and it smells bad.

Since the problem is in both subs, you might also check further up the signal chain and perhaps see if you have a bad cable between your AVR or perhaps something wrong on the amp itself. Try playing each sub separately to see if the sound is the same.

 

[Aharami]

i tracked it down to the amp. brought in my car amp and sub and hooked those up which showed that my HT subs still work ok. Hooking up my car sub to the HT plate amp shows the same distortion. opened up the amp to find a little burnt mark

no other visible damage on the underside

Looks like a jumper was damaged - which is odd. not sure what caused this

bulging caps?

All the other caps on the circuit board are smaller caps that look to be ok. These two 4700 uF 50V caps are the only two large caps that seem to be bulging. Wonder if replacing the jumper and getting some better caps will fix this issue. I'm thinking of replacing the caps with 4700 uF 80V ones. Good idea? bad idea?

 

[Aharami]

Or I can just replace the amp with this O Audio 500W BASH Amp

500W is probably overkill for what I need, but there's only a $60 difference between the 300W one and the 500W one, and the 500W has more controls

Anyone know anything about OAudio?

 

[NutBucket]

Being that its for a sub amp quality isn't critical. Hopefully you won't kill it

 

[Aharami]

hopefully not

 

[Aharami]

i do want to try and fix the current amp and use it in my living room. should i replace the caps with the same 4700 uF 50V caps, or step it up to something like 4700 uF 60V or 80V caps?

 

[Zardnok]

Or I can just replace the amp with this O Audio 500W BASH Amp

500W is probably overkill for what I need, but there's only a $60 difference between the 300W one and the 500W one, and the 500W has more controls

Anyone know anything about OAudio?

The O-Audio amps have a decent reputation in the DIY community.

As for repairing the old amp, shouldn't be a problem swapping out the caps and replacing the jumper as long as the Caps were the problem and not just a symptom.