Newbie question - amp sounding strange

[jbonecpa]

I have a 12 channel amp powering 6 pairs of speakers along with 6 impedance matching volume controls throughout the house. When I connect one particular pair of speakers they are distorted and only play at a very low volume. If I put my ear to the amp I can hear a distorted audio signal which is alarming because the amp doesn't have any internal speakers to be outputing any sound. I get the same result no matter which channel I connect this particular set of speakers to so it must have something to do with the wiring for these speakers. All the other speakers sound fine.
Would this be a short in the wiring??? Or something else????

 

[Privateer]

Would this be a short in the wiring??? Or something else????

Possible, what amp and speakers are you using?

 

[jbonecpa]

Possible, what amp and speakers are you using?

Phoenix Gold MX1260 amp with Polk in ceiling speakers, I believe they are Ri45.

 

[mtrycrafts]

I have a 12 channel amp powering 6 pairs of speakers along with 6 impedance matching volume controls throughout the house. When I connect one particular pair of speakers they are distorted and only play at a very low volume. If I put my ear to the amp I can hear a distorted audio signal which is alarming because the amp doesn't have any internal speakers to be outputing any sound. I get the same result no matter which channel I connect this particular set of speakers to so it must have something to do with the wiring for these speakers. All the other speakers sound fine.
Would this be a short in the wiring??? Or something else????

Since this happens with only one of the channels, swapping other channels to drive this one results in the same effects, it is not the amp. And, since all other speakers sound fine, if I read you correctly, your problem is limited to that one run of speakers, either the volume controller, wiring, or the speaker itself.

If you are capable, start with the speaker. Swap it out for one of the others. Then swap the volume controller if not the speaker. Sure hope it is not a wiring problem.

 

[jcPanny]

Volume Controls

Since you have 12 seperate amplifier channels, you don't need to use the impedence matching feature, so verify that all of the volume controls are set up for use with 1 pair of speakers. The impedence matching feature is used when you want to take the output from 2 stereo amplifier channels and connect it to speakers in 2, 4, or 8 rooms. The volume control divides the power between rooms so that the receiver will still see an 8 ohm impedence.

Also, before returning the speakers you could verify that the volume control is not the issue. Turn the volume controls in the 5 working rooms to the minimum level. Bypass the volume control in the problem room and use the volume on your receiver to adjust the sound level. If there is still a problem then replace the speakers. Your polks probably have a 2+ year warantee so getting a replacent speaker should be easy.

 

[j_garcia]

The "easy" way to test it would be to connect some wires and extra speakers directly to the amp for that connection - at the very least, this eliminates or identifies if the amp is the problem. If the amp works, you know it is something in the wiring after the amp. It sounds like the phase is wrong (wrong + to+ and - to -) somewhere in that particular wiring after the amp to me, or possibly even at the amp itself.

 

[mtrycrafts]

The "easy" way to test it would be to connect some wires and extra speakers directly to the amp for that connection - at the very least, this eliminates or identifies if the amp is the problem. If the amp works, you know it is something in the wiring after the amp. It sounds like the phase is wrong (wrong + to+ and - to -) somewhere in that particular wiring after the amp to me, or possibly even at the amp itself.

He checked if it was the amp channel. It is not. So, only a few options left: wireing, speakers, his volume control in the room.

 

[Eric Apple]

I had same problem

I had the same problem, it turned out to be a short where the wire entered the volume control binding post. Another symptom I had was amp shutdown at only medium volume levels. Seems the long wire runs have enough resistance to not cause a "dead" short. But, instead look like a low impedance speaker. The sound coming from the amp is the power supply transformer laminations or windings moving a bit as the high current to drive to extream load is being supplied. It's called magnetorestiction or something like that.

Or it's something else and I'm totatally wrong

 

[jcPanny]

Speaker wire resistance

According to the Belden spec, the resistance of 14 AWG speaker wire is only 2.5 ohms per 1000 feet. A short in most in-wall speaker runs would provide a very low resistance causing most amps to go into shutdown.

If you suspect a short in the wiring, pick up a $10 multimeter from Radio Shack and measure the resistance from the positive to negative wires when they are disconnected from the amp. If you are seeing less than the 8 ohm impedence of the speaker, than something is wrong.

 

[Eric Apple]

Low R is true..

Of course JC is correct on the low R. But, when only a single stand touches it's a little higer R then the entire wire correctly terminated. No doubt about it, it actually happened with a run of maybe 120'. The amp did shut down before getting extreamly loud. But, it actually still worked OK. Worked a whole lot better after the short was removed.