Speaker Impedance Setting

nsbs

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

Kex

nsbs wrote: »

... 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 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. ...

Welcome to Club Polk nsbs!

Firstly you should really post this outside the "testing area", if you haven't already. Maybe the "basic hookup" area: http://www.polkaudio.com/forums/forumdisplay.php?f=10. You can start a duplicate thread there.

In any case, pairing the 4 ohm LC80i speakers with any receiver that has a specific setting for 4 or 6 ohms is not a very good idea IMO. What these settings do is basically limit the output from the receiver so that it will not damage itself or the speakers (distortion from being driven too hard will eventually blow your tweeters). Receivers that can handle 4 ohm speakers correctly don't use a switch or setting at all. This does not mean the Yamaha is "bad", BTW, it just means it is not designed for 4 ohm speakers.

If you still want to use the LC80i, it probably doesn't really matter which setting you use. The 6 ohm setting may help prevent damage to them, but you will limit the output by using it. Most people would probably recommend using the 8 ohm setting instead, which will not limit the power output, but you will have to be careful not to play too loud. If the sound you are hearing sounds distorted (harsh, unpleasant to listen to), then turn down the sound immediately. Keep the volume setting well away from it's maximum output (at least 20dB "clicks" IMO). At reasonable levels, you should be safe, but if the receiver ever goes into protection mode, you'll have to rethink your options.

Two things are in your favor, however. Firstly, you only have two 4 ohm speakers in the system as you described it, so again, you should be just fine if you are careful, at least for now. Secondly, your receiver has pre-out connections, so with this receiver and those speakers, you should plan to purchase a two channel power amplifier to drive the two 4 ohm speakers. In this case, the receiver will only drive your 8 ohm speakers, and the power amplifier will take care the 4 ohms speakers.

If you think you may add extra 4 ohm speakers in the future, to match your existing ones, then you may want to think about a five or seven channel amplifier instead. One good option currently IMO is this NAD T955 (NAD are famously rated conservatively, and are rated to drive even 2 ohm loads):

http://www.nadelectronics.com/img/datasheets/NAD_T955.pdf
http://www.spearitsound.com/nad/T955.asp

Emotiva has been a popular entry level choice also, but not everyone agrees that they are as good as they claim (I have owned one, and find 70w of NAD power to be more dynamic and more "musical" than 125w of Emotiva power, but YMMV, and the Emotiva fanboiz will say that I'm a NAD fanboy Emotiva hater with delusions).

http://emotiva.com/shop/cart.php?m=product_detail&p=4

For two channel, Emotiva also has a bargain basement option:

http://emotiva.com/shop/cart.php?m=product_detail&p=39

but IMO, you might do better to search the Flea Market here, e-Bay (if you are comfortable shopping there), or AudiogoN for used amplifiers for $200 or less. The big difference is that buying new from Emotiva gives you a warranty, and their c/s is generally considered to be excellent.

http://www.audiogon.com/

For convience, and since I went there to check out what you were using, here is a link to your Yamaha.

http://www.yamaha.com/yec/products/productdetail.html?CNTID=5028422&CTID=5000300&ATRID=1020&DETYP=ATTRIBUTE

RuSsMaN

Thread moved...

Kex

RuSsMaN wrote: »

Thread moved...

So helpful of you, Mr. RuSsMaN!

nsbs

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

TECHNOKID

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

nsbs

Thanks TK, I think I'll go shopping for a new amp.

John K.

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.

!Jeremy

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.

nsbs

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?