Confused about 4-ohm usage

Sean22

Hello Everyone,

I just recently purchased my first set of "real" (non-home-theater-in-a-box) speakers to put together a 7.1 home theater:

RTiA9s for the fronts (8 ohm)
LSiC for the center (4 ohm)
LC60is for the surrounds (4 ohm)
PSW1000 Sub

The room is 18' x 19' x 9' and opens into the kitchen, so it is a pretty decent size.

Was it a bad choice to go with the RTiA9s instead of the LSi15s?

I was planning on purchasing the Denon 4308ci to drive them, but am getting less and less excited as I read more about driving the 4 ohm speakers. The primary reasons for wanting the Denon are the HDMI switching, Dolby TruHD / dts HD decoding, and networking capabilities for music playback. The receiver is only rated for 140W per channel for 8 ohm speakers (although it also makes mention of 6 ohm usage in the manual). The way that I understand it is that because the speakers have a 4 ohm rating, they need to draw more current from the receiver to operate properly. This then leads to overheating / "clipping" of the signal if the receiver can't support the draw. After dropping that kind of money on the speakers and then potentially on the new receiver, I don't want to risk damaging them.

I've been looking through the forums here and have seen some things about using a power amp, but a 5 or 7 channel amp looks like it'll run another $2K.

I'm not sure what to do at this point. Any advice would be greatly appreciated.

Thanks,
Sean

McLoki

Welcome to Club Polk. Kick up your feet and hang around for awhile - you may end up enjoying yourself.

Assuming you want the system mainly for home theater,

At this point, I think you would be better off returning the LSiC (if you can) and LC60i. Then you can purchase the CSi A6 center and TC60i surrounds that match your fronts.

I would still recommend a 2 channel amp to run your RTiA9s on, but that can wait for awhile (and the price difference between the LSi and RTiA lines should about pay for it). Get the AVR you want and you are good to go.

If the cost of a decent 5 or 7 channel amp does not bother you, then just exchange the 9's for LSi15's, add the amp and once again, get whatever AVR you like (as long as it has pre-outs).

Make sense?

reberly

I purchased the Onkyo TX-SR805 for my receiver and have it hooked up to the Polk LSi15 (Cherry) and Polk LSiC with a MartinLogan Dynamo Sub. The SR805 is spec'd for 4ohms and has every bell and whistle you would want in a HT. http://www.us.onkyo.com/model.cfm?m=TX-SR805&class=Receiver&p=i .

tonyb

Even an avr that is rated at 4 ohm will have a tough time when the volume goes up.Movies at reference levels will tax an avr driving 4 0hm speakers.Lets face it,gear cost way too much to risk destroying it,so why push that envelope.Take Mcloki's advice,or shell out some coin for some amps.You can get a 5 channel amp fairly cheap on the used market.No need to spend 2 g's.

Sean22

Thanks for the fast reply! This has been making me crazy...

I'm considering adding the 7ch amp and exchanging the 9s, but that will depend on whether I can convince the wife...do you have any suggestions for a decent amp? I was checking out the B&K 125.7, but I'm not sure what the specs on the amp indicate.

polkatese

125.7 will power your LSis nicely. I had one before I traded up to a Gemstone Blue Diamond.

Oh yeah, welcome!

Dave38

B&K 125.7: RMS Power at 4 Ohms is 185W

Serendipity

I'd agree with the others; 4 ohms is too much of a load for most AVRs.

I'm personally running 4 ohm speakers (Definitive Technology BP10B) on my Onkyo receiver and the receiver runs warmer with a 4 ohm load.

GSRBOB

I currently own RTi series and have recently taken the time to actually meter my RTi 10s. The specifications on these are incorrect, the nominal impedance is actually 4 ohms, unless they are configured for bi-amplification.

GSRBOB

I would think that the new RTi's are also rated incorrectly.

cfrizz

Welcome Sean.

I also agree with Michael. If you do decide to go with an all LSI system, you should spring for at least 200wpc @ 8ohm to get the true benefit of what the LSI's can do. You can get more bang for your buck if you get a used 5-7 channel amp.

Here are some good options.

http://cls.audiogon.com/cgi-bin/cls.pl?ampsmult&1198800340
http://cls.audiogon.com/cgi-bin/cls.pl?ampsmult&1200576771
http://cls.audiogon.com/cgi-bin/cls.pl?ampsmult&1199468653