# Speaker ohm rating vs. receiver ohm rating..



## bd_meme (May 3, 2011)

I can get a great deal on a pair of Polk LSI7s. I currently have a Yamaha HTR-5730 receiver and wondered if the Yamaha could handle the 4 ohm speakers. I checked the back of the receiver and it is rated at 6 ohms. I have a separate powered sub so it won't be expected to push the low end. I don't listen to my music/movies very loud.
Any help will be appreciated. I have seen great reviews on the speakers, but I don't want to have purchase a new amp. Thank you.


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## Guest (May 3, 2011)

Do you have the owners manual? I used to have an old yamaha, and I thought it had a switch for 6ohm speakers. It was older, so maybe the newer ones don't have that.

If you don't push it, it should be able to, but do it at your own risk. I used to run 4ohm speakers using a Onkyo stereo receiver that wasn't rated for 4ohms, and I never broke that.

You probably can, but really, use at your own risk. Never push the volume.


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## Jungle Jack (Jul 28, 2009)

bd_meme said:


> I can get a great deal on a pair of Polk LSI7s. I currently have a Yamaha HTR-5730 receiver and wondered if the Yamaha could handle the 4 ohm speakers. I checked the back of the receiver and it is rated at 6 ohms. I have a separate powered sub so it won't be expected to push the low end. I don't listen to my music/movies very loud.
> Any help will be appreciated. I have seen great reviews on the speakers, but I don't want to have purchase a new amp. Thank you.


Hello,
If you can get a great deal on the Speakers, go for it. Speakers make the biggest impact of any Component in a HT. If your AVR is not up to snuff, do crossover at 80hz (I prefer crossing Speakers there always) and carefully raise the Volume Level and make sure you are not hearing any distortion or hardening of the Speakers.

When funds permit, add an Amplifier if you have Preamp Outputs and or a better AVR.
Cheers,
JJ


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## GranteedEV (Aug 8, 2010)

Speaker impedace is tough to accurately know.

Some nominally 4 ohm speakers are resistive 4 ohm loads. Most amps have little difficulty with this unless sensitivity is low.

Other nominally 4 ohm speakers hover anywhere from 30 ohms to 2 ohms, with notable electrical phase angles affecting apparent current draw. 

Regarding the LSI7s, I think an amp officially rated for a 4 ohm load will be your best bet. I'm skeptical about the yamaha's ability to drive this speaker with good fidelity.

However I'll also throw in my opinion on polk speakers - I don't like em


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## Jungle Jack (Jul 28, 2009)

Hello,
There are definitely Brands I prefer more, but that Line uses ScanSpeak's Ring Radiator Tweeter which is an excellent Tweeter and as far as Polks go is far better than their usual offerings. I suppose it really comes down to how good of a deal it is,
Cheers,
JJ


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## drdoan (Aug 30, 2006)

Welcome to the Forum. Have fun. Dennis


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## robbo266317 (Sep 22, 2008)

Welcome, enjoy your stay.

As others have already said speaker impedance is a complex issue. You can have a speaker rated at a nominal 8 Ω that presents a much lower load to the amp at various frequencies and can cause damage. 
Personally, unless the amp is known to be robust, I would err on the side of caution.


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## Leon_Tyler (May 2, 2011)

Hiya,

In my professional opinion, it's always a good idea to match output impedance with nominal speaker impedance, or exceed it.

But in my personal opinion, it's probably fine. As far as I know, that amp has a speaker/output protect feature that will shut off the power amp section if it's trying to push too much current (or there is a short). So you shouldn't have to worry to much about blowing speakers or the amp.

I'd plug in the speakers, crossed over in your receiver, and start turning up the volume on some reference material. If you don't hear any distortions, you should be in the clear!

If you're sold on the speakers, but they won't work with the amp, you could put a 4 ohm power soak in front of each one--just spliced in between positive on your amp and positive on your speaker. Something like Parts Express item 019-015 would work just fine (can't post a link 'cause i'm so new!)

-T


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## bd_meme (May 3, 2011)

Gentlemen, thank you all. Very impressed with your rapid replies. Looks like I need to make some decisions.


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## Jungle Jack (Jul 28, 2009)

Hello,
You are most certainly welcome. Since you are using a Subwoofer, the load on the Yamaha should be reduced by a good bit provided you set the Crossover to 80hz. If these Speakers are a amazing deal, I would not let your AVR dissuade you from purchasing them. Again, slowly raise the Volume and hear how it responds. As the Bass is where most Speakers are presented the most difficult load, the use of a Subwoofer really might make this work.
Cheers,
JJ


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## GranteedEV (Aug 8, 2010)

Leon_Tyler said:


> Hiya,
> 
> In my professional opinion, it's always a good idea to match output impedance with nominal speaker impedance, or exceed it.
> 
> If you're sold on the speakers, but they won't work with the amp, you could put a 4 ohm power soak in front of each one--just spliced in between positive on your amp and positive on your speaker.


Um... sorry, but this is not good advice, and I recommend you think the nature of AC circuits and speaker impedance loads over carefully. Output impedance of an amplifier should be negligibly close to zero. Further, such an approach as you describe will only reduce sensitivity (requiring more voltage to get the same output).

Back to 'matching output impedance' - this will change the frequency response of the speaker. Most speakers are voiced as driven by a solid state, zero output impedance amp - thus a higher output impedance (even .5 ohms, never mind 4 ohms!) will only serve to colour the speaker's frequency response. This effect can be audibly observed with poor amplifiers such as tubes.


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