2. amps-preamps
  3. 161856-5277

Driving different pairs of speakers with different speaker wire lengths

Looking for some sage advice.  My GF’s stereo is comprised of components I’ve replaced over the years.  It consists of a Denon CD changer, an older Technics multi channel HT receiver, a pair of Sonus Faber bookshelf speakers and a pair of Klipsch bookshelf speakers.  The Sonus Fabers are a couple of feet from the receiver, and the Klipschs are around 30 ft from the receiver (connected with 14 gauge speaker wires that run under the floor).

The receiver has connections for A and B speakers along with rear/surround and subwoofer channels.  I have the speakers connected to the A and B speaker outputs.

I am a civil engineer by degree, and had to take intro to EE twice, and not because I enjoyed it so much the first time - the concepts of matching impedance, etc escape me.  The system sounds very well balanced, but after about an hour of listening the receiver will stop and display an overload condition.  I suspect the difference in the speaker loads, coupled with the vastly different lengths of speaker cable are too much for the receiver to handle.  This irritates the heck outta the GF, so I gotta come up with a solution.

I’m thinking of getting a solid state preamp with two line level out connections (single ended) and a pair of two channel Class D amps - one for each pair of speakers.  This would let each two channel  amp handle the load presented to it individually without the other speaker load adding to it.  Intuitively I think this will work.

The Wyred for Sound MPRe preamp has two sets of RCA preout connections, has a DAC (not needed now, but could come in handy later as I improve her system), and is reasonably priced.  I think this might be part of the solution.  I now need to find a pair of two channel Class D amps that are reasonably priced as well.

The space for all this is really limited, so Class D is my current direction.  I’m scouring the used market for a pair of two channel class D amps that are small, and reliable.  Chances are I’m not gonna find a matching pair so I solicit any recommendations on new ones that are reasonably priced, and thoughts on my overall approach.

Thanks,

Mitch
vermonter

Showing 1 response by atmasphere

atmasphere's avatar
atmasphere
12,088 posts
 
Its unlikely that the different speaker cable lengths are doing anything bad, unless the cables have some sort of high capacitance which is known to mess with certain designs that have poor phase margins. If the cables simply have two conductors side by side this is probably not the case. If anything, the longer cable will cause the amp to see a slightly higher load impedance but IMO/IME it won't amount to a hill of beans.

If the amp is on a shelf and there isn't much room above it, it could be overheating due to poor circulation. The output transistors are mounted on heatsinks and the heatsinks have temperature monitors- if they get too hot the amp will shut down. Otherwise it could be that you simply need speakers of higher efficiency so you don't have to push the amp so hard.
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