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Old 12th December 2013, 09:13 PM   #1
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Default Spectra 1100 Screeching

Can anyone kindly help me with my problem, which is that one of my Spectra 1100's has developed a nasty screetchy, distortion with certain material, most noticeable on female vocals played at loud levels?

I have owned these speakers from new (1989 I think). I did have problems a few years back, when bi-amping, one channel of the amp driving the woofers blew and its corresponding woofer was fried. I replaced the woofers after some kind help from Parts Express with Dayton Audio RSS210HF-4 which I realize may not be an exact copy but to my ears is a big improvement.

I returned to using only one amp for about two years and all was fine but when I attempted to bi-amp again, the same channel started to over heat. I then tried bi-amping vertically with each amp driving both woofer and ESL, one for left speaker and one for right, and that worked fine. But the side that blew is the one that is now distorting.
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Old 13th December 2013, 08:10 PM   #2
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Quote:
Originally Posted by factor8 View Post
Can anyone kindly help me with my problem, which is that one of my Spectra 1100's has developed a nasty screetchy, distortion with certain material, most noticeable on female vocals played at loud levels?

I have owned these speakers from new (1989 I think). I did have problems a few years back, when bi-amping, one channel of the amp driving the woofers blew and its corresponding woofer was fried. I replaced the woofers after some kind help from Parts Express with Dayton Audio RSS210HF-4 which I realize may not be an exact copy but to my ears is a big improvement.

I returned to using only one amp for about two years and all was fine but when I attempted to bi-amp again, the same channel started to over heat. I then tried bi-amping vertically with each amp driving both woofer and ESL, one for left speaker and one for right, and that worked fine. But the side that blew is the one that is now distorting.
My first thought is that you might have a bad audio transformer in the speaker's interface. Since the problem occurs only at loud levels, the transformer might be arcing over.

However, there shouldn't be anything inherant about bi-amping that should cause this problem, unless of course you have simply over-driven the speaker. That can cause high-voltage arc-over in the transformer, leading to eventual failure.

What happens if you go back to driving the speakers with a single stereo amplifier? And, what amplifiers are you using? If you are using bridged amplifiers, that may be another potential problem. When you bridge an amplifier, each half of the bridged amp 'sees' only half the load impedance. Since the speaker is fairly low impedance to begin with, the amplifier may be unstable into that very low impedance, which may also be responsible for that 'screeching' problem.
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Old 14th December 2013, 09:46 AM   #3
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Quote:
Originally Posted by AcoustatAnswerMan View Post
My first thought is that you might have a bad audio transformer in the speaker's interface. Since the problem occurs only at loud levels, the transformer might be arcing over.

However, there shouldn't be anything inherant about bi-amping that should cause this problem, unless of course you have simply over-driven the speaker. That can cause high-voltage arc-over in the transformer, leading to eventual failure.

What happens if you go back to driving the speakers with a single stereo amplifier? And, what amplifiers are you using? If you are using bridged amplifiers, that may be another potential problem. When you bridge an amplifier, each half of the bridged amp 'sees' only half the load impedance. Since the speaker is fairly low impedance to begin with, the amplifier may be unstable into that very low impedance, which may also be responsible for that 'screeching' problem.
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Old 14th December 2013, 09:53 AM   #4
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The problem remains using just the one amp. Amps are Classe DR10 and Rotel 981. I have never used them bridged. Can anything be done with the interface or is the speaker toast?
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Old 16th December 2013, 05:48 PM   #5
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Originally Posted by factor8 View Post
The problem remains using just the one amp. Amps are Classe DR10 and Rotel 981. I have never used them bridged. Can anything be done with the interface or is the speaker toast?
I would suggest swapping the interfaces from one speaker to the other, to see if the problems follows the interface. This will help eliminate other problems with the speaker, or the amplifier channel.

If the problem does follow the interface, then you probably have a bad audio transformer. I don't know if any of those transformers are available. You might check with Sounds Like New, who does Acoustat repairs. Contact info can be found at www.audiocircuit.com, in the Acoustat section.
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