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Did adding a speaker selector screw up my system?

econeditor

econeditor

New Member
I've got two pairs of speakers: a pair of Original Large Advents, and a pair of EPI T/E 100s. I picked up an Adcom GFS-3 speaker selector so that I can A/B between the two, and hooked it up this evening. I'm using a NAD 3020b as a pre-amp and an Exposure 2010s power amplifier. Originally, each pair of speakers sounded good on their own, but playing both pairs together sounded wonderful, as there was a fullness in the sound of all four together. (I didn't engage the protection button on the Adcom; according to the manual it should be able to handle two pairs of 8-ohm speakers, and the power amp should be able to handle 4-ohm impedances). Before too long, though, I noticed some distortion in the sound (I wasn't playing it terribly loud); and then, backing out to just the EPIs I noticed that on their own they sounded significantly fuzzier than when I had started. So: did I screw something up? Did I blow out the speakers? Did I mess up the amp? Did I fry the speaker selector? I'm not quite sure where the problem is or where I should start looking; any guidance is appreciated!
 
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To me, it seems your power amp didn’t like running both pairs of speakers. Even though each was rated at 8 ohms, it’s possible that one or the other, or both, we’re actually operating at less than 8 ohms. If any of the speakers were repaired by replacement with non-spec drivers, or the networks altered, that could cause them to run lower than 8 ohms.
 
Coolhandjjl said:
To me, it seems your power amp didn’t like running both pairs of speakers. Even though each was rated at 8 ohms, it’s possible that one or the other, or both, we’re actually operating at less than 8 ohms.
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Would that continue on when I switched back to running only one set of speakers through the selector? When I went back to using the EPIs alone they still sounded much more distorted.
 
As RVT1K said, take the selector out of the circuit and then see if you still have the issue.

Regardless of rating, those Advents are really much closer to a 4 ohm nominal load. Should have been rated no higher than 6 ohms, at most.
 
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econeditor said:
Would that continue on when I switched back to running only one set of speakers through the selector? When I went back to using the EPIs alone they still sounded much more distorted.
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If you fried some of the output transistors by running the amp at too low of an impedance load, going back to one pair of speakers won’t bring them back. The damage has been done.
 
I believe that amp has over-current protection. If true, and if working correctly, chances of damage to the amp are low.

That said, I'm having trouble coming up with a scenario to explain the cause of OP's problem other than an issue in the amp...assuming it still sounds distorted when running one pair of speakers at a time (with the selector removed).

OP, did you turn the amp off and let it sit for 5-10 mins before trying it with just one pair of speakers?
 
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spark1 said:
I believe that amp has over-current protection. If true, and if working correctly, chances of damage to the amp are low.

That said, I'm having trouble coming up with a scenario to explain the cause of OP's problem other than an issue in the amp...assuming it still sounds distorted when running one pair of speakers at a time (with the selector removed).

OP, did you turn the amp off and let it sit for 5-10 mins before trying it with just one pair of speakers?
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The OP stated that he turned the amps protection circuit off.
 
Coolhandjjl said:
The OP stated that he turned the amps protection circuit off.
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Thanks all. I left the protection switch on the selector off; I think @spark1 is right that the Exposure has over-current protection.

I'll fire up the system this morning (after everyone is up and moving) and hopefully all will be well...
 
You need to try each speaker pair with the Adcom taken out of the circuit. That has now been suggested at least three-times and I don't see where you've tried it.

I have one of those and I think the newest of them is likely over 20-years old. You may have some issue in the Adcom, like the switches, or internal connections. Until you take it out of the system you'll never know.

(I should also add that I've never used mine, or the SAE similar product I've owned for decades. People give me enough sh*t for having a Soundcraftsmen EQ in every system and tell me how much that is degrading my signal. I can't imagine what a speaker switcher will contribute!)
 
BMWCCA said:
You need to try each speaker pair with the Adcom taken out of the circuit. That has now been suggested at least three-times and I don't see where you've tried it.

I have one of those and I think the newest of them is likely over 20-years old. You may have some issue in the Adcom, like the switches, or internal connections. Until you take it out of the system you'll never know.

(I should also add that I've never used mine, or the SAE similar product I've owned for decades. People give me enough sh*t for having a Soundcraftsmen EQ in every system and tell me how much that is degrading my signal. I can't imagine what a speaker switcher will contribute!)
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Very little, actually. It's the impedance protection function that causes most of the problem with sound quality, especially if implemented with resistors (vs autoformers).

OP said above that he will be trying it this morning without the selector in circuit.
 
spark1 said:
OP said above that he will be trying it this morning without the selector in circuit.
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Not that I saw. He said: "I'll fire up the system this morning (after everyone is up and moving) and hopefully all will be well..."
No mention of removing the Adcom. :dunno:
 
BMWCCA said:
Not that I saw. He said: "I'll fire up the system this morning (after everyone is up and moving) and hopefully all will be well..."
No mention of removing the Adcom. :dunno:
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I over drove my system 5 yrs ago sounded all garbled let it set overnite it’s been fine every since just didn’t make that mistake twice !
 
If you are using adcoms impedance protection circuit, it probably won't harm your amp. Like many other speaker selector boxes adds a resistor of perhaps 5 ohms + between the speakers, which are probably connected in Parallel and the amp. This way they can run as many speakers as they want and never send impedance down below 5 ohms, or until the resistor burns up, which ever occurs first. Not very efficient.

If the protection circuit is switched off, you could be overdriving your amp.

I don't see many complaints about these switch boxes. But I wouldn't recommend them for critical listening on an expensive stereo system, they seem to be fine for the average consumer.

A more effective way to drive multiple speakers with one amp is a box that uses transformers instead of resistors. Probably the same principle as the old 70 volt public address system amps. Today either powered speakers, or multi-channel amps are a popular choice.
 
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fredgarvin said:
Well, I'm up and I'm moving. Get moving you other guys!
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Lol. Been at it all morning.

  • Fired things up, unchanged from last night. Speakers still sound fuzzy; Junior nearby confirms: "Yeah, that doesn't sound right."
  • Remove Adcom, connected EPIs directly to power amp; sounds better. So far so good.
  • Reconnect the speakers to Adcom, run Adcom back to power amp, to compare again. Now, the EPIs sound...better? Fuzziness seems to be gone.
I've been going back and forth all morning, which is kind of a pain in the neck since the Exposure only takes banana plugs and the Adcom only has the weird locking inputs, so I have to swap the plugs back and forth each time. I *think* I can hear differences; my wife, who has joined me by now (and pointed out the fuzziness the evening before) thinks it sounds the same regardless of whether I'm playing direct into the power amp or through the selector, perhaps slightly louder when speakers are connected directly to power amp.

My guess: I over-drove my system last night; the Adcom introduces very slight differences in sound, not enough to be really perceptible but enough that I think I hear differences. It's also quite possible I am driving myself slowly crazy .

So...crisis averted, I guess?
 
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econeditor said:
Lol. Been at it all morning.

  • Fired things up, unchanged from last night. Speakers still sound fuzzy; Junior nearby confirms: "Yeah, that doesn't sound right."
  • Remove Adcom, connected EPIs directly to power amp; sounds better. So far so good.
  • Reconnect the speakers to Adcom, run Adcom back to power amp, to compare again. Now, the EPIs sound...better? Fuzziness seems to be gone.
I've been going back and forth all morning, which is kind of a pain in the neck since the Exposure only takes banana plugs and the Adcom only has the weird locking inputs, so I have to swap the plugs back and forth each time. I *think* I can hear differences; my wife, who has joined me by now (and pointed out the fuzziness the evening before) thinks it sounds the same regardless of whether I'm playing direct into the power amp or through the selector, perhaps slightly louder when speakers are connected directly to power amp.

My guess: I over-drove my system last night; the Adcom introduces very slight differences in sound, not enough to be really perceptible but enough that I think I hear differences. It's also quite possible I am driving myself slowly crazy .

So...crisis averted, I guess?
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I'm glad to hear that it came out ok.
 
How about this...,

When you had both pair playing at once, one pair plays louder than the other and you turned it up enough to do damage to the other set of speakers because you initially could not hear the distortion in the other set over the louder set that was also playing.

I don't see where you've gone back and tried each pair of speakers separately and noted if one or both sets are now "fuzzy" but maybe I just missed it
 
charles 1973 said:
If you are using adcoms impedance protection circuit, it probably won't harm your amp. Like many other speaker selector boxes adds a resistor of perhaps 5 ohms + between the speakers, which are probably connected in Parallel and the amp. This way they can run as many speakers as they want and never send impedance down below 5 ohms, or until the resistor burns up, which ever occurs first. Not very efficient.

If the protection circuit is switched off, you could be overdriving your amp.

I don't see many complaints about these switch boxes. But I wouldn't recommend them for critical listening on an expensive stereo system, they seem to be fine for the average consumer.

A more effective way to drive multiple speakers with one amp is a box that uses transformers instead of resistors. Probably the same principle as the old 70 volt public address system amps. Today either powered speakers, or multi-channel amps are a popular choice.
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thanks! With the protection switched on the speaker selector the sound takes a definite hit, which kind of cancels out the improved sound of all four speakers together. Is there a transformer speaker selector you’d recommend? The two pairs running together really does sound good…

maybe I can run the EPIs with the integrated 3020, and the OLAs with the Exposure? That may be slightly beyond my skill level.
 
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