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Old 15th July 2007, 11:16 PM   #1
ronjodu is offline ronjodu  United States
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Default Speaker protection help

I have 2 BrianGT 3886 chipamps with 2 PSUs connected to 2-28 volt torroids.(measured 70 volt rail to rail on each amp)
I want to connect this setup to my outdoor Bose 151s. The Bose are rated 40watt IEC at 4 ohm. Wire length is about 40 feet 16 gague.
The input to the amp will be either an Ipod Shuffle, 30G ipod or Sansa MP3 player.

My stepson already melted two of these speakers with the 30G ipod. What is the best way to protect the new set from the same fate?(I was fortunate to be able to exchange them for a new set.)

Thanks for any replies.
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Old 16th July 2007, 08:19 AM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
run a single mono signal from the amp to a series pair of the little Bose speakers.
That way you present an 8ohm load to the amplifier, you reduce the losses in the cables and you have a nominal 80W rating for the pair of speakers.
Outdoors the bass response will be way down. Do not try to boost the bass to make them "sound" right. That will overload them and risk blowing again.

Do not bridge the amp, just use one channel.
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Old 16th July 2007, 08:37 AM   #3
Did it Himself
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The only way you can protect those speakers is to buy a compressor/limiter.

I'm curious how you drove speakers off an ipod? They are only headphone output.
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Old 16th July 2007, 08:52 AM   #4
Arx is offline Arx  Canada
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Quote:
Originally posted by richie00boy
The only way you can protect those speakers is to buy a compressor/limiter.

I'm curious how you drove speakers off an ipod? They are only headphone output.
Through the amp, obviously.

The source probably isn't especially relevant, unless it was swinging enough voltage to clip the input, in which case it could be pretty hard on the tweeters.

As long as there's no major defects, like DC on the source, it probably doesn't much matter from one to the next.

A compressor or limiter is the wrong answer. Just find a way to keep the kid from cranking the thing up, if that's the cause.

If it's an electronic problem, fix it.

My bet is someone just enjoys the sound of clipping at max volume. That seems far too common these days.

-Nick
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Old 16th July 2007, 09:24 AM   #5
Did it Himself
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Ah but he wote it like he is only just now trying to connect the amp.

Yes getting the person to not turn it up too much is the right answer. However the only PROTECTION that will suffice is a compressor/limiter.
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Old 16th July 2007, 01:00 PM   #6
BWRX is offline BWRX  United States
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Just put a resistive divider on the input so that the maximum input signal results in an output level below the clipping level (or below the rated power of the speakers) of the amplifier.
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Old 16th July 2007, 07:11 PM   #7
r221b is offline r221b  United States
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A simple way tp offer some protection is by using an in-line fuse. If your speakers are rated at 40w @ 4 ohms, then the current through them would be a bit over 3 amps running at maximum. Use a 3 amp fast blow fuse. If you listen to your music loud with a lot of bass, then you might have to keep a few extra fuses around, just in case. You might try a 2 or 2.5 amp slo-blo fuse if the 3 amp blows too often. Or turn down the volume a bit. It isn't foolproof, but it's cheap and effective.

sherlock
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Old 16th July 2007, 07:36 PM   #8
ronjodu is offline ronjodu  United States
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Thanks for all the replies. Would a buffer on the input/output or both be of any use? If so any buffer suggestions. I like the fuse idea. I have a few inline fuseholders onhand. 2.5 amp it is.

Thanks again
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Old 16th July 2007, 11:06 PM   #9
Arx is offline Arx  Canada
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Quote:
Originally posted by BWRX
Just put a resistive divider on the input so that the maximum input signal results in an output level below the clipping level (or below the rated power of the speakers) of the amplifier.
This is probably a good way to do it, though I can just imagine a kid boosting everything on the eq to compensate. More clipping, blown tweeters.


Quote:
Originally posted by ronjodu
Thanks for all the replies. Would a buffer on the input/output or both be of any use?
Well, it's not likely to help with this particular problem, but it may give better sound on devices without enough current capability on their outputs.

-Nick
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Old 16th July 2007, 11:49 PM   #10
BWRX is offline BWRX  United States
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Quote:
Originally posted by Arx
This is probably a good way to do it, though I can just imagine a kid boosting everything on the eq to compensate. More clipping, blown tweeters.
Hmm, I hadn't even thought of that possibility knowing how ghastly most electronic EQs sound!

ronjodu, perhaps it would be easier and cheaper to teach your stepson how to identify when music sounds bad because the speakers, amp, or source, are being overdriven
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