Powering LSi's question...

ms8888

I am interested in getting the LSi7's and from what I have read, receivers like Yamaha/Denon will not do them justice. Sorry for the newb question, but I was wondering what the difference is in power thats rated 130wX7 (like on the Yamaha RX-V2500) and the 110wX7 (like on the NAD T773). On the surface, it seems that the Yamaha has more power to drive the speakers, but from the posts I have read it is not the case.

venomclan

Hi ms8888,
Welcome, watt ratings alone are tricky in themselves. The questions to ask is wether that rating was achieved when all channels of the receiver were driven at the same time. Also important to know is how much distortion it produced at that level, and how low in ohms it can realistically go without clipping.
The more headroom(power to spare) on a receiver the better.

Chances are that if you are going to use the LSI'7s at low-moderate listening voules, then those receivers should be ok. The LSi's 4 ohm rating as opposed to most speakers 8 ohm rating, make the LSi's harder to drive. This creates more demand on the amplifier, and it will run hotter than usual, which can also lower the life expectancy of the receiver. It also creates a tendency for the amp to clip more easy, also threatening to blow the speakers.

A seperate amp is ideal for speakers that are harder to drive.
Venom

bertram

The power ratings are for a specific speaker load (resistance): 4 ohms, 6 ohms, 8 ohms, etc. You should see this mentioned somewhere in the receiver's specs (e.g. 110 watts into 8 ohms). 8 ohm speakers are easier for an amplifier to drive than 4 ohm. Better amplifiers will usually do better with lower ohm speakers. An amplifier that provides 110 watts into 8 ohms might manage only 160 watts into 4 ohms. Ideally, the amplifier would be able to deliver 220 watts into 4 ohms and 440 watts into 2 ohms!

The Polk LSi speakers, for example, are all rated at 4 ohms. The RTi series is 8 ohms. So while just about all receivers will drive the RTis to loud levels, the LSis will be much more difficult for most receivers to drive equally loud.

My Denon receivers (like most) carry warnings about using speakers below 6 ohms but I have no problem using them with the LSi speakers because I don't have very large rooms and therefore don't have to crank the volume up too high. Just because a receiver or amplifier is rated at 8 ohms doesn't necessarily mean that it can't do fine with 4 ohm speakers... you just have to be careful with the volume.

ms8888

Thanks for the info.
It helped clear things up a bit.

mantis

Most receivers don't have the current capabilities needed to drive the Lsi's properly.

Compnies like B&K, NAD,Sunfire and Rotel all make receiver that can drive the Lsi's well. This is where you wanna be if a receiver is what you want.

The Rotel rsx1067 is really sweet. Check it out.

Dan

http://www.rotel.com/products/specs/rsx1067.htm

jcaut

I think the keywords from your first post are "do them justice".

Strictly speaking, the LSi7's are not that hard to drive, despite their 4 Ohm rating. The other dual-woofer LSi's may be more difficult, but the 7's impedance is really not much (if any) lower than some of the RTi models. I don't think you'd have to worry about your receiver shutting down, overheating, etc.. You could get by with it.

I know for a fact that my LSi7's sound quite different (but so do the RTxx) when being driven by a power amp, versus my Denon 3801. The difference is current capability. Even though a receiver may be rated 130wpc or whatever, some don't have much current capacity to back it up. As the impedance goes down, power output sags and distortion goes up. Since a speaker's impedance is a curve, with peaks and valleys at different frequencies, the current requirements are very dynamic when playing music. One of the reasons a more powerful amp sounds better is that you have the amp controlling the speaker, vs. the other way around.

The LSi's are very nice speakers, and "doing them justice" with regard to amplification, to me, means using a power amp or at least an upper-tier receiver. Otherwise you're not getting the sound quality that they're capable of.

Jason