Subwoofer started rattling out of control!? - AVS Forum
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post #1 of 8 Old 09-14-2014, 10:02 PM - Thread Starter
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Exclamation Subwoofer started rattling out of control!?

This morning at around 11am, my receiver was off (standby), pre-amp, and everything else for that matter, and all of a sudden my subwoofer (Dynamo 500) starts rattling out of control at literally 100% power it sounded like.

First thing I did was cut the power, it sounded the like amp was going to explode.

I then unplugged the sub, and the LFE in cable, and let it sit for a bit. I also turned the power knob down to zero percent, and plugged it back in with no LFE cable in.

Turned it on, instantly the same thing occurred, ear deafening rattling and noise. Flipped it off and unplugged it. 12 hours later it is doing the same thing.

I don't have a power conditioner just a power strip so I tried moving it around the house, I moved here recently and suspect a lot interference and dirty power. When I flipped a few light switches one time a little bit of noise came off of the sub, very subtle.

About a year ago, the sub began doing this strange thing where if I would turn my receiver off the sub would remain on and not go in stand by for maybe an hour or so, and when it did finally go in stand by it would begin making this humming/distorted/noise sound. Not very loud and it would last about 30 seconds and then cut out the blue on light would flicker the entire time with it, and then cut out. It has done this every single use since then. However if you start up my receiver while its doing this, it instantly stops and plays bass normally.

I'm suspecting the controller inside has gone absolutely nuts, but I don't know why. I've had for under 2 years and obviously have not mis treated it, it's hardly moved. I also don't really push almost ever.

On one or two occasions, while a video game was being played, a very low pass over would cause it to rattle horribly for a second or two. Very rare. I didn't think much of it, but I guess the writing was on the wall?

I've sent Martin Logan an email, and will call once it's normal business hours.

Does anyone have any insight as to what on earth went wrong? Or even better, has this happened to anyone before?
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post #2 of 8 Old 09-15-2014, 08:11 AM
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The sub is broke and most likely not worth fixing.

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post #3 of 8 Old 09-15-2014, 11:57 PM
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Another plate amp bites the dust. That is what happens when you seal a power amp with NO VENTILATION. I can't stress enough to anyone reading this how plate amps are disposable designs. The cost of the parts to fix it are not expensive so it's worth fixing if you can do it yourself. Unfortunately it will happen again in a few years depending on the parts used.

You can run it off of a rackmount power amp and run the feed into the port to the driver for the time being.
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post #4 of 8 Old 09-17-2014, 10:30 AM
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My Dayton Audio SP-250 did exactly the same thing... The subwoofer turned on in the middle of the night at full power to my poor 12" Polk driver. y wife and I literally thought it was an earthquake, the rumbling was that loud. Sad to say, the amp was bad but luckily PE replaced it for free.

I don't think sealing an amp in the sub will cause premature failures. All the sub amps I have bought have heat sinks and they do not even get that warm. I just think that the sub amps are poorly built and the high power requirements by subs causes premature failures on poorly designed units. I have had subs by Polk, Sunfire and Velodyne all suffer from failures.

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post #5 of 8 Old 09-17-2014, 11:12 AM
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Quote:
Originally Posted by Jon S View Post
I don't think sealing an amp in the sub will cause premature failures. All the sub amps I have bought have heat sinks and they do not even get that warm.
Wasn't referring to the driver's enclosure. The AMP's chassis is sealed airtight so heat just builds up in where all the components are and trust me, it gets warm. Even digital amps. That's why your digital SMPSU on your computer has a fan blowing out warm air.

If these amps had an intake and a fan blowing heat out of them, they would not have been thrown into wild oscillations from components failing. When do you hear of pro sound amps failing like that? There are many stories of plate amps doing that.
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post #6 of 8 Old Today, 01:46 AM
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That's what the heatsink on the outside is designed for! How do you think car amplifiers work for 20+ years with all their internals hidden in a case so small that there is zero air space...the heatsink!!!

Failure is just unfortunate and not due to heat 99% of the time.
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post #7 of 8 Old Today, 04:39 AM
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Quote:
Originally Posted by Shreds View Post
Wasn't referring to the driver's enclosure. The AMP's chassis is sealed airtight so heat just builds up in where all the components are and trust me, it gets warm. Even digital amps. That's why your digital SMPSU on your computer has a fan blowing out warm air.

If these amps had an intake and a fan blowing heat out of them, they would not have been thrown into wild oscillations from components failing. When do you hear of pro sound amps failing like that? There are many stories of plate amps doing that.
Digital plate amps get barely warm. If you made the claim of air inside getting hot- post internal and external temps, when sub is off, and after say 3 hours of constant high output.

I do know subwoofers with class AB amps get hotter, ie BK- they require heatsinks for cooling.

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post #8 of 8 Old Today, 08:49 AM
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Quote:
Originally Posted by fatbottom View Post
Digital plate amps get barely warm. If you made the claim of air inside getting hot- post internal and external temps, when sub is off, and after say 3 hours of constant high output.

I do know subwoofers with class AB amps get hotter, ie BK- they require heatsinks for cooling.
Comon man, don't act like a digital amp is some kind of new alien technology that is 100% efficient.

Digital amps are more efficient than non-SMPSU class A/B but let us examine this. Lets say you have a 1000W class D that is (I'm giving you the benefit of the doubt here) 95% efficient. That's still dissipating 50W of heat at full power. That is significant when it has no way of escaping the chassis. I've seen digital amps (with fans) go into thermal shutdown to save themselves from damage due to heat. Completely enclosing a power amp is dumb. My blu ray player has a SMPSU in it and it gets warm. Not exactly a high current device.

I get it, components fail sometimes but heat is still the enemy of all components. My point is that sealing them with no ventilation makes their life as short as possible and a good cooling system prolongs the life of components to the max. Totally worth a 10 dollar fan or at least some vents no avoid you coming home from work one day to a ruined sub.

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