Some information about Polk LSi speakers (1 Viewer)

[Allen Longcor]

Thought I'd pass this along to everyone. I emailed Polk to see if their 4 ohm speakers would cause a problem for my Onkyo 595 should I choose to buy them. 12 hours later (excellent response time since I emailed them last night around 6pm pst) I received an email stating that they average around 6 ohms and should work fine with my Onkyo. So don't let the 4 ohms throw you off if that is a selling point. Of course they could just be trying sell me some speakers.

 

[Mark Austin]

Hmmm...

So in their specs they state that the nominal(average) impedance is 4 ohms, but in emails they are saying they average 6 ohms? I wonder why they would do that? Why not just change thier spec sheet if in fact they were a nominal 6 ohm speaker.

 

[Miklsan K]

I am currently powering LSi9s and an LSi Center with a 575X and a friend is powering the same with his 595. I have not pushed them to insane volume levels, neither of us has experienced any problems yet. By the way, I highly recommend the LSi speakers. They seem like a great speaker at a (relatively) reasonable price. The detail is phenomenal and they are bright but smooth(especially after a little break-in). Good listening!

 

[Gil D]

Here is the link to the Soundstage review measurements of the LSi9 where chart 4 shows impedance vs frequency:
Link Removed
The 4 ohm average rating is most due to the cascaded woofers similar to an MTM. Where the woofs overlap is where the impedance drops. I would think if you receiver is rated for 4ohms then your OK. Of course these speakers probably deserve a separate amp and are biampable which I have not tried yet on my nines.

 

[Mark Austin]

To my eyes, that impedance curve would indicate a nominal impedance of 4 ohms.

 

[Keith Mickunas]

According to that graph it spends a significant amount of time at 6 ohms or higher, with only short ranges at 3k, 200, and 50 that are under 6 ohms. I don't think their out of line calling it 6 ohms if they want. That hump from 400 to 1.5k would have a significant impact on the average, whereas the worst part is at 50, which if you've crossed over at 80 or above then there shouldn't be much draw on the amp at that low level. I'm no expert, but it looks to me that if they want to claim 6ohm, they can, whereas their literature probably states 4ohm just to be on the safe side.

 

[Mark Austin]

Keith,

Maybe I'm looking at the graph wrong. To me the impedance starting at 50hz is at or below 3ohms, then stays under 5ohms 'til about 80hz where it reaches about 6 ohms, then at 100hz it starts to dip again to 5ohms, then from 150-400hz it stays below 5 ohms, from 500-1K it goes up to about 9ohms, then at 2K it's down around 5ohms again, then dips down to 4ohms at about 3K, then starts a rise where it hits 6ohms a little after 5k. I would maybe put it at 5ohms overall.

 

[Keith Mickunas]

Mark, I guess its just a matter of how you average it. My knowledge of the physics of sound is good enough to determine which sides have the most influence of the average, nor can I easily determine where exactly the points on the graph are. I would definitely say it averages greater than 4k because there's so little below that. I'd say from 20-50, definitely over 5ohm, 50-100, perhaps 4ohm, 100-200, 4.5 maybe, 200-500, 5, 500-1k, 7, 1k-2k, 7, 2k-5k, 5, 5k-10k, close to 6, 10k-20k, 6. So there I get an average of 5.5, but that's with a lot of guestimation and assuming that the area between 100 and 200 has the same weight as between 10k and 20k.

The important thing is this, all speakers vary in their impedance, and several things affect this. Then you have to consider which areas are heard the most often. I don't know all the answers to this, but I think, IMHO, and I'm not a an expert in amplifiers, speakers, or the physics of sound, however I do have a BS in CS and Mathematics, that its safe to say that if your amp can handle 6ohm, it can handle these, and you don't need to buy an amp that specifically says it can handle 4ohms. We can argue over the 1 to 1.5ohm difference in our interpertations until we're blue in the face, but without a better graph or a listing we can average, its really moot. Polk said Allen's receiver should be OK, and that's what really matters.