Question about terminating unfinished wiring in new home

Discussion in 'Home Theater Projects' started by Wade, Jan 20, 2005.

  1. Wade

    Wade Stunt Coordinator

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    Right now I basically have a bundle of wires hidden behind the wall in our family room. There are five pairs of wires for the home theater speakers located in the family room ceiling, there are four two pair wires which I presume are for the master bedroom and back patio volume controls (seems to be two extra for what I don't know) and finally there is one unfinished coax cable. The two extra two pair wires could be for the sub outlet located on one of the side walls. Won't know until I can get to the cover to open it.

    All I want to hook up are the two rear speakers in the family room and the two on the patio and the two in the master bedroom. The patio and master bedroom would need volume controls. I want to do this cleanly without having to chop up the wires behind the wall too much. My question (finally) is it possible to hook up this 8 terminal speaker wall plate with the top four terminals for the rear home theater speakers and the four bottom terminals for the patio and master bedroom volume controls? Can two volume controls be connected to the same terminals and then powered using the multi room capabilities of this Harman Kardon receiver?

    I hope what I am trying to do makes sense. I'm wanting to put up a new entertainment center but want to get all of this worked out first.

    Thanks,
    Wade
     
  2. Allan Jayne

    Allan Jayne Cinematographer

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    I take it that the pairs of wires are all 14 gauge or thicker.

    Provided that the wires behind the wall are floating free and not coming through a junction box, that plate will work OK.

    I would not recommend putting that wall plate on the wall if there is a junction box back there. The junction box behind the cover is most likely much too small to arrange the wires and make the connections.

    The rough rule of thumb for electricians is, two cubic inches for each conductor (plus two cubic inches for all of the grounds plus two cubic inches for all of the jack assemblies.

    But practically speaking, once you made all of the connections, the mass of wires is going to be very stiff and you will have a hard time getting everything into the junction box and screwing on the cover plate.

    Instead you will want to feed all of the cables out into the room and make the connections to banana jacks there. One idea that may work is to have another, preferably wider, junction box with 2 x 3 inch or larger hole in back, fastened outside the wall to the existing junction box inside the wall, you can get an adapter ring wall plate to cover this external box and the Radio Shack wall plate fits on the adapter ring.

    To put two volume controls and two speakers on the same pair of terminals you need to apply the parallel speaker rule, impedance of each speaker needs to be at least twice the rated impedance of the amp. output.

    Speakers should not share a common ground wire. A 12 gauge common ground is the equivalent of individual 14 gauge speaker wires for two speakers or (I guess) individual 16 gauge wires for four speakers.

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  3. Wade

    Wade Stunt Coordinator

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    Allan,

    Thanks for your response.

    Unfortunately the wires are not 14 gauge. The singe pairs running to the five home theater speaker locations appear to be 18 gauge and the two pair wires for the volume controls appear to be 16 gauge. The extra two pair wires are for subwoofer 1 and 2 and the coax is in fact for the sub as well. I'm not using that sub location so these wires will go unused. There's not much I can do about the size of the wire behind the wall. I plan on using 14 gauge to attach everything to the receiver.

    I have come to the conclusion that I don't need the master bedroom speakers hooked up so I will only need to one volume control. So I guess I wont need an impedance matching volume control.

    There is no junction box behind the wall. There is just a mounting plate attached to the stud, it's basically wide open behind there. I'm going to go ahead and get that radio shack wall plate and attach the surround speakers as well as the patio speakers. I just need to confirm wether or not the HK 635 receiver can be used to drive the patio speakers.

    Thanks again,
    Wade
     
  4. Allan Jayne

    Allan Jayne Cinematographer

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    Too thin a wire increases the impedance.

    This does not hurt the amp, but you might notice degradation of the sound particularly when the volume is high or there is a lot of bass (higher current situations).

    You will have no problem feeding the patio speakers using separate amp channels, or using a switch box so a given amp channel feeds only one speaker at a time.

    What is multi-room capability for an amp? Is it having built in switching so one amp channel feeds two pairs of speaker terminals one at a time?
     

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