Axiom Home Page Forums General Discussion Technical Questions curious results...hope someone can explain

As many of you know I have been switching my M60's from system to system during the 30 day trial. Today I thought I would be very clever and hook the speakers to both the 2 ch reciever with the upper speaker connects and to the HT set up through the lower speaker connects. Hoping I would just be able to switch between the 2 recievers at will. Keep in mind I was only sending the signal at any given time from one of the recievers leaving the power off on the unit not in use. When I did this the speakers would go on and off. I thought my old HK was wigging out on me. I thought it was going to give up the ghost. As soon as I disconnected the speaker connects to the HT everything was fine again. What did I do wrong? I would think as long as only one source was sending a signal to the speakers at a time everything would be fine. Both channels would just go out and then after a few seconds they would come back on and play for a few seconds and then they would go out again. On, off, on, off. Can anyone explain this to me?
Thanks oz
oz

Probably some kind of feedback. Remember that most electronics are not off when you power them down, they're on standby. I would be very cautious about this; you could damage both pieces of equipment.

Yeah... I didn't let it go for very long and then disconnected one of the sets of speakers cables. I figured it sounded potentially dangerous. Thought I'd ask here. I hadn't thought about the fact that the HT is actually in standby and not off. That could be it.
oz

You can probably surmise by how your electronics were behaving during your experiment that connecting two amps and alternating between them is not a good idea. Remember that the top posts on the speaker are only wired internally to the mids and tweeters, while the bottom posts are only wired to the woofers. Even if your electronics were functioning normally, this would not be a good way to compare equipment since you're not getting the whole picture. In order for all the drivers to be firing, you need to be applying power to both sets of posts simultaneously.

As to why your electronics were cutting in and out, they were probably going into overload protection mode. I don't believe the sets of posts are entirely electically separate since they still must go through crossover circuitry inside the speakers. The amp that is active might still "see" the inactive amp as a load on the wire, causing it to strain while attempting to drive the extra load.

I don't think feedback from the standby receiver had much to do with as it probably would have occurred had it been physically unplugged, as well.

Keep the straps between the posts in place and resign yourself having to swap cables.

I had the straps in place at all times. I had the 2 ch speaker cables going to the top connects and the HT going to the botton connects with the straps in place. Thinking I would only have one unit powered up at a time would not hurt anything. Obviously I was wrong. I was wondering what the technical explanation might be.
Thanks,
oz

Yikes! With the straps in place, that was definitely a no no. You were sending the power both to your speaker AND to the other receiver -- even though it was off. I'm glad things seem to have survived, since it's entirely possible you could have burnt something out.

Oz, as Peter indicated, the active amplifier "sees" both the M60 impedance and the impedance of the inactive amplifier(assuming that the speaker terminal straps are there to complete the circuit)even when the second amp is turned off. The result is similar to making a parallel connection with the M60 and another speaker of extremely low impedance, resulting in a very low net impedance.

John
My bad! I guess I thought it was like a one way street. Glad nothing permanent happened. Half bubble off plumb for sure this time. Thanks for the explanation.
oz