[dinaudio]

I have 10 pars of inwall speakers (Niles brand) in each room, basement, garage, living room, ... Each pair is controled by a dial control knob.
That inwall speaker systems had fried two amps so far -- NAD 314 and Hafler 220.
I cannot explain exactly how it is set up, but there is one (two?) circuit board in the basement with all the wires leading to each pair of speakers. In the living room, there is only one pair of connection to the amplifier. So, with a 2 channel amp, I can turn all 10 pair of speakers.
That was the problem. NAD314 lasted a couple of days. Hafler lasted a couple of weeks. Both time, I had multiple pair of speakers turned on (set the volume knob to the mid position).

Is this configuration normal? How come only one speaker outlet jacks for 10 pairs of speakers? What I can think of is that turning more than one pair of speakers essentially lowered the impedance to half. If I was listening to 4 pairs of speakers, the overall impedance would have been 1 ohm, which no amp can sustain for a long time.

[Phil A]

I don't think the configuration was meant to drive 10 pair of speakers.  It was meant to connect amplifiers to speaker leads in the basement.

[Audiophiliac]

It depends on what this "circuit board" is. Niles does make an autoformer impedance matching piece that accomodates 10 pr. of speakers. It is the SMS-10. Other companies make them too. It basically provides a selectable load to your amplifier.

My guess is that something is not wired correctly, or the amps you are trying to use are not designed to output the current you might be demanding of it. I would test all the wiring to make sure there is not a short anywhere. Use a multi-meter to check all the wires in the basement. And then, turn all your volume controls to mid-way or so and test the resistance of the leads at the amplifier.

Case in point. We had a system that we did not install, but were called to come service and upgrade. We put in a new 12 channel amp and a few days later, it died. We went out with a new amp. And sure enough. A week or so later, it died. So we started looking at every volume control...every speaker. And sure enough. We found that on one of the volume controls, the labels on the phoenix plugs had been swapped so the speakers were connected on the input side and vice-versa. It played music still, but it was not right.

Could be a number of things. But there are systems that work just as yours is wired. Good luck.

[dinaudio]

Many thanks for your reply.
I am still learning about whole this.
The pics show what I have in the basement and the speaker outlets in the living room.
I purchased a Niles 30WPC 12 channel amp. Would I need to install the amp in the basement? Then, what's the purpose of having the control board (transformers?) in the basement?

From right angle


From center view


speaker outlet

[dinaudio]

Here's what I found on the two transformers.
200W
XF 00001E
There are five lines on one side with 1.2, 1.5, 2, 3, 8 ohm, and on another side 6 lines with common, .60, .66, .75, .887, 1 ohm.

Anybody has an idea what kind of transformers they are? I don't have any manual, and I was not told anything about ex-owner of the house about what kinds of amp should be used with the inwall speakers. I just blew up NAD314 and then Haffler220/Transcendence 2.
I would appreciate if somebody can tell me what kind of amp should I need to use to match the speakers and the transformers.

Edit: The control board is Niles Audio SMS-10, High Power Impedance Matching System. It indeed looks very likely that something wrong in overall wirings.