Speaker Impedance Setting

nsbs
nsbs Posts: 5
edited December 2009 in Basic Hookup/Wiring Questions
I'm a little confused as to what to do with the following scenario.

I have just purchased (2) Polk LC80i ceiling mount speakers for living room, (1) Niles CM760DSsi(stereo input) for kitchen, these will be powered by an Yamaha RXV765 Amplifier.

The Polks will be hooked up to the front channel on amp
The Nile will be hooked up to Zone "B".

The impedance for the two manufacturers is different, with the Polk being 4 ohm each, the Nile being 8 ohm.

After reading manual for the amplifier and powering up to make changes, it only allows me to choose from either
6 ohm, or 8 ohm setting. Being new to this I really have no idea what to do.
If anyone can shed some light I would greatly appreciate it.

Thanks
Post edited by nsbs on
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  • RuSsMaN
    RuSsMaN Posts: 17,986
    edited November 2009
    Thread moved...
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
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  • nsbs
    nsbs Posts: 5
    edited November 2009
    First of all I have to apologise for originally posting on the "Testing site" being totally new to posting on a forum I'm a little overwhelmed, thankfully I'm not in public office or I'm sure I would be crucified by now.
    Thank you Kex for the wealth of information you have provided. I really wished I had asked for some input prior to buying the hardware that I now own.

    I have spoken with a tech rep this morning from Niles and described my situation, he has suggested that I run 2 volume control switches, set my amp to 6 ohm setting, and each volume control to 4 ohm setting. I wished I'd paid more attention to the basics of electricity back in High School.

    Can anyone comment on these settings given to me?
    Once again thanks again for the great information
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  • TECHNOKID
    TECHNOKID Posts: 4,298
    edited November 2009
    nsbs wrote: »
    First of all I have to apologise for originally posting on the "Testing site" being totally new to posting on a forum I'm a little overwhelmed, thankfully I'm not in public office or I'm sure I would be crucified by now.
    Thank you Kex for the wealth of information you have provided. I really wished I had asked for some input prior to buying the hardware that I now own.

    I have spoken with a tech rep this morning from Niles and described my situation, he has suggested that I run 2 volume control switches, set my amp to 6 ohm setting, and each volume control to 4 ohm setting. I wished I'd paid more attention to the basics of electricity back in High School.

    Can anyone comment on these settings given to me?
    Once again thanks again for the great information
    If you are to keep the present amp, yes you should set for 6 ohms in order to protect the output drivers of your amp... and yes using selectable impedance matching volume control would allow you to accomplish the desired results: http://www.parts-express.com/pdf/182-866m.pdf
    http://www.parts-express.com/catalog/pdf/2009/073pec09.pdf
    http://www.parts-express.com/wizards/searchhelp.cfm?search=selectable%20impedance%20volume%20control&CFID=3336769&CFTOKEN=71358272

    The one that best suit your need will be determined by the O/P power of speakers and amplifier (the highest rating should be your choice).

    The volume control will also allow you to set the desired volume for each of your area. As Kex points out, the power will be limited slightly to your 4 ohms speakers but at least your amp O/P drivers will not be at risk and you will be able to adjust the power as you desire through the volume control. You will have to make sure your amp is not clipping in order to protect the speakers themself (particularly the 4 ohms). Hope this helps.

    Cheers!
    TK
    DARE TO SOAR:
    “Your attitude, almost always determine your altitude in life” ;)
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  • nsbs
    nsbs Posts: 5
    edited November 2009
    Thanks TK, I think I'll go shopping for a new amp.
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  • John K.
    John K. Posts: 822
    edited November 2009
    NS, you were given some bad advice by the Niles "tech rep". The lower impedance setting should never be used. All this does is to reduce the voltage that the power supply section of the receiver can output. It's there to satisfy UL(Underwriters Laboratory)requirements to help prevent overheating. When the voltage is reduced, so is the current and power, following Ohm's Law. Although this reduces the chance of overheating the receiver, lab tests show that it cuts the maximum power roughly in half. This makes it more likely that the speakers would be damaged if the receiver clips because of the reduced power. To maintain the full capability of your RXV765 leave the setting at 8 ohms.
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  • !Jeremy
    !Jeremy Posts: 17
    edited December 2009
    I have an Onkyo 906 tx nr906 which has a similar setting within the menu. For speakers at 6 ohms and below the recommended setting from the factory is '6 ohm' otherwise set the attribute to 8 ohm. Setting the value to 6 ohm does in fact reduce the overall output of the receiver, but it does allow the receiver to run at a lower temperature. That being said I have been powering a pair LSi9s and LSi FX speakers with the receiver setting at 8 ohm with no issues. The Onkyo will display the internal temperature of the receiver on the lcd display along with the current state of the internal fans. I have yet to get the receiver hot enough to kick on the fans and I do listen to music at high volumes for long periods of time. The only cavaet I can think of is that I intentionally keep all of my electronic equipment out and on shelving which in no way can impede air flow. If you keep your receiver in a cabinet or some sort of stand which can reduce convection then I would suggest keeping the receiver set to to the lower wattage setting to avoid overheating and potentially damaging it.
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  • nsbs
    nsbs Posts: 5
    edited December 2009
    Ok thanks for all the input guys. I have changed my Amp setting back to 8 ohms, now what about the volume controls? Should they be left at the 4 ohms each?
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