Spectra 1100, Problems

Read more on the Acoustat Spectra 1100 in our home audio section

Chris Behrens2004-02-23 22:21

Dear Andy, I\'m having some problems with my Acoustat Spectra 1100s. My biggest problem is my woofer crossover. I found that one of the coils was melted, so I replaced it. I then tested it using an HP audio oscillator and found it went right up to 3 kHz without any attenuation! Then I checked the 1 ohm resistor and found it was fine. I checked the cap using an ohmeter and it read as an open circuit, so it appeared okay. I replaced the cap later to be sure and it still goes up to 3 kHz. I checked that all components were soldered correctly and that there were no problems with the PCB. The only problems left could be the woofer or the biamp switch. Any ideas?

My next problem is with the panel interface. I also tested the esl panels by themselves using the HP oscillator and found that they produced frequencies down to about 60 Hz. Again, it seems that there is a crossover problem. I checked the 10 ohm resistor and it is okay. What else could be wrong with the intereface?

My last problem is with the woofer itself. I am the third owner of these speakers and I have no idea if they are the original woofer, but they are very poor quality woofers. I know the original woofers were designed to be inefficient, but the woofers in these speakers don\'t even get down to 50 Hz without huge SPL drops. I looked at the magnet in the back and it\'s tiny. The bass response of these woofers is awful. Do these sound like the original woofers? Using the Bullock Box design software, I seem to have found a good replacement. It is a Peerless 220WR and in a 1.36 sealed box, it is down -3dB at 40 Hz. It can also be found for $38.00 at www.madisound.com.

Thanks so much for the help. Chris Behrens


Andy Szabo2004-02-23 22:21

From your description, it sounds like you may not have the original woofers. The original woofers have 23 oz. magnets, rubber surrounds, black paper cones, and oversized voice-coil caps. The woofers are capable of credible bass response down to at least 40 Hz.

You didn\'t specify how you measured the response of the crossovers. The woofer crossover cannot be accurately measured without the woofer in-circuit. The best way is to measure the voltage across the woofer\'s terminals. The crossover point is about 150 Hz (or is it 250 Hz?), so it should measure about 3 dB down at that point.

The response of the ESL crossover is difficult to measure, and it must be done as a complete system (i.e. with transformer and panel connected). However, due to the high voltage output, it is not advisable to measure the voltage at the panel. The only recourse is an acoustic measurement, using a microphone. This can be tricky: near-field measurements won\'t give an accurate result, due to the large area of the speaker. And far-field measurements can be corrupted by room acoustics.

I\'m not really sure what the problem might be, or if there really is a problem other than the suspicious woofers. I can\'t conceive of any way that the biamp switch could be the source of the trouble. My only recommendation is to replace the woofers, if you think they are not original. Let us know how that Peerless woofer works out: other people have asked for a source for the woofer, and I haven\'t been able to help.

By the way, you mentioned replacing the crossover coils. Where did you find replacements? Many people (myself included!) would like to know.

Gerald Borgne2010-09-20 23:44

Where can i find replacement crossover coils for my spectra 1100 or the crossovers

Gordon Hazlette Sr.2010-11-18 01:33

I have just purchased a pair of Spectra 1100's. The original owner said that he was listening about 2 months ago, when he heard a "pop" in the left panel. Now there is a intermittent buzz from the panel. What do you think the problem would be? I am guessing that it is located in the electronics. Could you help? Is there someone who could repair this problem here in the U.S.?
Thanks...Gordon in NE Ohio

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