2. amps-preamps
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Just got a pair of Polk Audio LSi15s Need advice

Hi all, just for some background, I am in my early twenties and have been intrigued by hi-fi for a long time. On craigslist, I recently came across a pair of Polk Audio LSi15s for $500 (!!!). They're in pretty much mint condition, too!

Being relatively new to this hobby, I don't have much gear in terms of great amps to plug them straight into. What I do have is a Sony STR-D915 from long ago. I've been reading up a lot on speaker impedance and how not to destroy your equipment. That being said, I'm still a little bit weary about using the Sony with my LSis for extended runs. Here are the tech specs straight from the manual (you can find a PDF-manual on sonystyle.com if you'd like to take a look):

110 watts per channel @ 8-ohm load, from 20-20KHz, minimum RMS power

It does have a 4-ohm/8-ohm selector switch on the rear, so I assume it's been designed to handle loads. I've also read to keep it switched as 8-ohm, so that's what I've been doing.

I am very, very aware that a better amp will make my LSIs sing, but for the moment, the Sony will have to do. Do you see any perceived issues running the LSis with the Sony?

Even though I'll be using the Sony for a while, I'm still doing some shopping/research on possible integrated amps. I took a look at the new Onkyo A-5VL since it has an optical SPID/F input for my MacBook Pro, from which I will feed PCM from Apple Lossless data. The A-5VL has a Burr-Brown DAC which is much better than he DAC inside my MBP, but it only has 40 watts per channel at 8-ohms.

Help me out: how do the 40 watts from the Onkyo compare to the 110 watts from my current Sony? Are my Sony watts "dirty" compared to the power coming from the Onkyo (or any other higher-end amp under ~100 wpc for that matter?

I am trying to understand the importance of "raw power" vs "clean power." Especially concerning the LSis, which have been noted to require a great amount of power (>200~300wpc @ 8-ohms) to make them sing.

If you have any other recommendations for driving these speakers with music coming from Apple Lossless on a MacBook Pro (via optical out), please advise. Also, please note that I cannot spend loads of cash on a dedicated DAC + a pre-amp + 2 dedicated monoblocks, etc.. I did read up on the Bryston B100DA SST, which looks amazing, but just slightly out of my league at the moment. Are there any other reasonable products that can accept digital audio?

Thanks for reading... I am anxious to hear your advice!
yesyeselmer
hifitime
715 posts
 
I'm pretty sure your speakers are 4ohm.I think you need to double check that.If they are,put the 4/8ohm switch on the 4 ohm setting.Otherwise your receiver might be running hot and hard trying to drive the Polks.Actually the Sony looks like it has a more honest power rating than the new Onkyo your looking at.When you look at the power rating for a stereo amp,it should state something like this(40 watts minimum RMS per channel both channels driven into 8 ohms at 20 to 20,000 hertz).It has to at least have the full
audio range specified.The Onkyo is rated 40 continuous at1kz(1000hertz).That means that if a low music note like an organ at 20 hz is being reproduced,the amp might drop down to 10 watts or less(just a guess)at 20 hz.In the audio world,people prefer the true power rating at full audio range of 20hz to 20,000hz.Its a loophole they are using to make it sound more powerful than it is.If you like your music loud,that new amp may be under powered.Mid to Hi-end gear should have clean power.Raw power?You could google true
watts RMS,FTC rules and learn more. Somebody else may be of
help with an amp if you give your $ budget. Compare the Pioneer power rating to HT magazine.A couple links to look at.>>[http://www.angelfire.com/electronic/funwithtubes/Amp-FTC-Power.html] [http://www.hometheatermag.com/receivers/808piorec/index.html] [http://www.hometheatermag.com/receivers/808piorec/index2.html] [http://www.pioneerelectronics.com/PUSA/Products/HomeEntertainment/AV-Receivers/PioneerReceivers/ci.VSX-918V-K.Kuro?tab=B]
darkkeys
99 posts
 
Yes, the Lsi 15's are 4 ohms. I have a pair and they should be mated with proper amplification designed to drive a 4 ohm load. Take a look at my system setup for ideas. I am completely happy with the sound/performance of my setup. Pretty much any amplification from NAD should drive your speakers competently. For your computer music files you may be interested in a product from High Resolution Technologies called the Music Streamer, which is a USB DAC for less than 100 bucks that the reviewers say performs great in terms of sound quality.
loomisjohnson
1,941 posts
 
the outlaw rr2150 receiver is a cool looking piece with an inboard usb hookup for your computer, 100w/ch and good reviews. for around $600, it's the route i'd go.
blainethemono
4 posts
 

Ive owned a pair for over 10 years, and they come alive @ 100RMS per channel.  Course, my 100 watts was from a vintage Yamaha M4... which is a lot more amp then any modern day amp of the same power and cost.

Right now I'm running a Nakamichi PA7 Stasis Mk ll, 4 Ohm load @ around 400 RMS, so I have to be careful...



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