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Discussion Starter #1

I was hoping someone may be able to clear something up for me when it comes to impedance matching.  I am trying to set up a whole-house audio scenario using a Yamaha RX-V673 as the source.  I want to connect the zone-2 output of the receiver to six different pairs of 8 ohm speakers in six separate rooms of the house.  This is how I hope to have it set up:

 

Receiver --> (Amplifier?) --> Distribution Block --> Impedance Matching volume knob --> 1 Pair of Speakers

 

I would like to get volume knobs that have on/off switches on them, so that I can completely cut power to the speakers when not in use rather than just turn the volume all the way down. Will this be an issue when it comes to the impedance matching?  For example, if each volume knob is set for the appropriate impedance matching while using 6 pairs of speakers, what will happen when only one pair is active and the rest are turned off?

 

Would I essentially be running a single set of 8 ohm speakers at a much (much) higher impedance, and would I even be able to hear them?  Also, is there any possibility of damaging hardware in this case?  Any input on this matter would be greatly appreciated, as I have been having trouble finding an answer online.

 

As a side question, is it likely my receiver would be able to handle the extra load for all of the speakers at once, or should I invest in an external amplifier as well?  I am not sure how to determine how much power I will need.

 

Thanks!
 

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I took a quick look at your Yammy's specs and, I may be wrong, but it seems like zone 2 is a line level output (i.e. unamplified) - so you'd definitely need a supplemental amplifier to power your additional speakers. If this is the case, you could select something like a 12-channel amp to handle everything.


To answer your question about running parallel speakers and turning off individual pairs, this isn't an issue: it's just like not connecting a parallel branch to the circuit. The one (major) consideration is the total current draw on your amp - as you were alluding to, adding more speakers increases the amperage drawn and at some point you will exceed the current that the amplifier can deliver....which is not a good thing! Although a bit heavy going, this is a good article on calculating loads, etc.: http://www.prestonelectronics.com/audio/Impedance.htm - the type of amplifier you buy (# of channels) will dictate how things get wired.


Re. power requirements, I think that most people vastly over estimate the power needed to run at reasonable listening levels - if you pick a decently powered amp, that can handle the current draw, I suspect you'll never run anywhere near to maximum volume. Even a 15w amp can be painfully loud!


Hope that helps a bit.


Dave
 

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Discussion Starter #3

Thanks for the info, I'll check that article out.  The receiver actually has both line-level outs and amplified outputs for zone 2.  In the picture below, you can see the spring clips on the right hand side labeled "ZONE 2/PRESENCE" which are the powered outputs, and the rca jacks on the bottom labeled "ZONE 2 OUT" which are the line-level outputs.

 

I was hoping to stay away from purchasing an external amp simply because of cost, but not if there is any likelihood of damaging my receiver trying to power 6 pairs of speakers off of the internal zone 2 amp.

 

 

 

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Any decent amp when faced with too much load will simply shut down - not fail.


As long as you set your IMVC devices correctly things should be fine.


If by some chance setting the IMVC to the OFF position removes the load that's still OK as too little load is not a problem.
 
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