Power Amplifier blew and took a speaker with it

Someone7272 · 10th May 2010, 05:51 PM

DIY disaster. I recently made a pair of 12inch speaker cabs with a horn. Got a new amp today to test it on. Disaster.
Today I got my new Skytec Pro 600 amplifier. I know this puts out about 300W each channel and my speakers are 200W max, but I didn't actually drive the amp, I kept it under 2 on the volume dial, so low that not even the db meter was lighting up. However, when I was testing the amp with my iPod, suddenly, the right channel went silent with all db LEDs lit up so I powered the amp down, heard a pop from the right speaker, and that was it. The right channel never worked again. I replaced the cable, and tried a different working speaker on that channel but it just won't work. So I went back to the original speaker and opened it. It smelled a lot like magic smoke. I took the woofer out. It has blown somehow from under 20watts... The left speaker and channel works fine. The right channel is gone completely and so is my woofer. I'm gonna get replacements hopefully, but what could have caused this just so this doesn't happen again. For the record, the horns and crossovers in the speaker which blew still work, its just the woofer.

Steve Dunlap · 10th May 2010, 06:37 PM

Your amp failed and put out DC. The second speaker you tried is probably blown now also. The horn survived because of the cap in series with it. You may also have burned some of the coils in the crossovers.

LAJ · 10th May 2010, 06:37 PM

Your amp suddenly developed a short and put out DC. Thats why all the LEDs lit up. The DC (probably full rail either plus or minus) burned out the voice coil in the speaker. It was not the audio power (AC voltage) that took out the speaker. An amplifier working properly does not put out DC. Do not reconnect any load until you resolve the DC on the output problem. Typical DC output on any amp is usually like .05 volts. Yours is much more than that!

Rikard Nilsson · 10th May 2010, 06:39 PM

I´d say large amounts of DC offset, but there are usually protection circuits that would turn off the amp, or disconnect the driver using an output relay. Also, the amp could be oscillating badly at HF frequencies, but this is more likely to fry the tweeter or crossover components. The woofer is likely to be the last thing to blow from HF. So in a way it doesn´t make much sense. My bet´s on DC offset.

Mooly · 10th May 2010, 06:42 PM

Was this a brand new amp ? I wonder if there is anything load wise with your speakers that upset it (causing instability), although a commercial amp should be absolutely bullet proof and include DC offset protection. Tough luck

Plammox · 10th May 2010, 06:43 PM

Did you use DC-blocking caps between the iPod and the amp? Hint: measure the DC-level of the iPod output. If the amp is also directly coupled, then your speaker unit is toast. I suppose the crossover did what it was supposed to, and let the DC bypass the horn.

Someone7272 · 10th May 2010, 06:50 PM

Developed a fault? In a matter of minutes? And it blew one of my precious speakers? This is outrageous, good thing the woofer was a cheap crappy 15quid woofer. I'm pretty sure the crossover and horn is fine because it works fine on a hi-fi amp. The second one is fine, I think the right channel is disconnected, its not doing anything now no lights, fuse has probably gone. Is it safe to carry on using the left channel or should I save my second speaker?

Someone7272 · 06:59 PM

Quote:

Originally Posted by Mooly

Was this a brand new amp ? I wonder if there is anything load wise with your speakers that upset it (causing instability), although a commercial amp should be absolutely bullet proof and include DC offset protection. Tough luck

Yes it was a brand new commercial amp

My speakers were 8Ohm, which is in the clear, the min is 4Ohm
Nope, I didn't know a such thing as DC blocking caps existed but I'm pretty sure the iPod is fine.

jaycee · 10th May 2010, 07:12 PM

Quote:

Originally Posted by Someone7272

Developed a fault? In a matter of minutes? And it blew one of my precious speakers? This is outrageous, good thing the woofer was a cheap crappy 15quid woofer. I'm pretty sure the crossover and horn is fine because it works fine on a hi-fi amp. The second one is fine, I think the right channel is disconnected, its not doing anything now no lights, fuse has probably gone. Is it safe to carry on using the left channel or should I save my second speaker?

Probably poor manufacturing. Don't use the other channel - return it for a refund.

Someone7272 · 07:20 PM

Quote:

Originally Posted by jaycee

Probably poor manufacturing. Don't use the other channel - return it for a refund.

Thanks for the info... I can't get a refund, it'll have to be a replacement, looks like I'll be staying with my old 15W Sansui AU2200 for now :/
Could I have caused this by connecting the speakers with musical instrument/microphone cable rather than using professional speaker cable? I think it might have been my fault cos in the manual, I'm meant to use proper speaker cables

10th May 2010, 05:51 PM	#1
Someone7272 diyAudio Member Join Date: May 2010	Power Amplifier blew and took a speaker with it DIY disaster. I recently made a pair of 12inch speaker cabs with a horn. Got a new amp today to test it on. Disaster. Today I got my new Skytec Pro 600 amplifier. I know this puts out about 300W each channel and my speakers are 200W max, but I didn't actually drive the amp, I kept it under 2 on the volume dial, so low that not even the db meter was lighting up. However, when I was testing the amp with my iPod, suddenly, the right channel went silent with all db LEDs lit up so I powered the amp down, heard a pop from the right speaker, and that was it. The right channel never worked again. I replaced the cable, and tried a different working speaker on that channel but it just won't work. So I went back to the original speaker and opened it. It smelled a lot like magic smoke. I took the woofer out. It has blown somehow from under 20watts... The left speaker and channel works fine. The right channel is gone completely and so is my woofer. I'm gonna get replacements hopefully, but what could have caused this just so this doesn't happen again. For the record, the horns and crossovers in the speaker which blew still work, its just the woofer.

10th May 2010, 06:42 PM	#5
Mooly diyAudio Member Join Date: Sep 2007	Was this a brand new amp ? I wonder if there is anything load wise with your speakers that upset it (causing instability), although a commercial amp should be absolutely bullet proof and include DC offset protection. Tough luck __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

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10th May 2010, 06:37 PM	#2
Steve Dunlap diyAudio Member Join Date: Sep 2008 Location: Here	Your amp failed and put out DC. The second speaker you tried is probably blown now also. The horn survived because of the cap in series with it. You may also have burned some of the coils in the crossovers.

10th May 2010, 06:37 PM	#3
LAJ diyAudio Member Join Date: Mar 2008 Location: Atlanta Ga. USA	Your amp suddenly developed a short and put out DC. Thats why all the LEDs lit up. The DC (probably full rail either plus or minus) burned out the voice coil in the speaker. It was not the audio power (AC voltage) that took out the speaker. An amplifier working properly does not put out DC. Do not reconnect any load until you resolve the DC on the output problem. Typical DC output on any amp is usually like .05 volts. Yours is much more than that!

10th May 2010, 06:39 PM	#4
Rikard Nilsson diyAudio Member Join Date: Aug 2008	I´d say large amounts of DC offset, but there are usually protection circuits that would turn off the amp, or disconnect the driver using an output relay. Also, the amp could be oscillating badly at HF frequencies, but this is more likely to fry the tweeter or crossover components. The woofer is likely to be the last thing to blow from HF. So in a way it doesn´t make much sense. My bet´s on DC offset.

10th May 2010, 06:43 PM	#6
Plammox diyAudio Member Join Date: Aug 2008 Location: Luxembourg	Did you use DC-blocking caps between the iPod and the amp? Hint: measure the DC-level of the iPod output. If the amp is also directly coupled, then your speaker unit is toast. I suppose the crossover did what it was supposed to, and let the DC bypass the horn.

10th May 2010, 06:50 PM	#7
Someone7272 diyAudio Member Join Date: May 2010	Developed a fault? In a matter of minutes? And it blew one of my precious speakers? This is outrageous, good thing the woofer was a cheap crappy 15quid woofer. I'm pretty sure the crossover and horn is fine because it works fine on a hi-fi amp. The second one is fine, I think the right channel is disconnected, its not doing anything now no lights, fuse has probably gone. Is it safe to carry on using the left channel or should I save my second speaker?

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