Interesting observation: Lsi7 Impedance

jcaut

I mentioned in another thread that I might try running impedance curves on the pair of 7's while they were new, and then again later, to see if any effects of break-in are apparent.

I also mentioned in an earlier thread that my Denon 3801 didn't seem to drive them very well---- at least it didn't sound good doing it---- while I briefly had them connected to it. They sound totally different when connected to a separate power amp. Now, my other speakers sound different also, but I don't think the difference is AS noticable, with say, the RT800i's. I attributed this to the 4 Ohm impedance of the Lsi's and the Denon's somewhat limited current capability.

I got a couple of surprises when I ran the impedance curve: The 7's don't go all that low. They earn their 4 Ohm rating, I guess, but they only touch 4 Ohms one time between 15Hz and 20KHz.
The impedance phase curve looks pretty benign, too. They don't appear to be a terribly difficult load for most decent amps.

Here's another surprise: For comparison, I also ran a curve on the RT3 that I had sitting here. This is a late 90's small bookshelf with a 5.25" midwoof and a 1" polymer dome tweeter, rated 8 Ohms, nominal. It's impedance is lower than the LSi7 practically everywhere on the curve.

By posting this I'm not trying to say that I think you can run the 7's on just anything. I just found it interesting that they're not as low as I thought they'd be. The dual woofer models would probably present a lower impedance, but I don't have any of those to check.

I'll attach a pic of the Lsi7 and RT3 impedance overlay. I eliminated the phase data for clarity.

Jason

kingtut

Interesting findings. Thanks for the posting of the graph.

Sami

Originally posted by jcaut
I attributed this to the 4 Ohm impedance of the Lsi's and the Denon's somewhat limited current capability.

That might be why I didn't hear much difference with my experiment running the LSi7's with just my H/K AVR7200 and later bi-amped with the AVR and H/K PA2000. I don't have a high wattage power amp, not yet, maybe that would change the sound.

But to me it plays fine with 2*115W on a high current receiver.

jcaut

Could be. The H/K AVR's internal amps might be beefier than my Denon. I've always felt that it does a pretty good job with the speakers I normally have connected to it, especially in HT use. From the manual though it sounds like 6 Ohm is about all it wants.

I hooked the LSi7's to my AVR briefly, in place of my RT800i's, just to get a feel for how they sounded in comparison. Then I switched them to a 375wpc (@8Ohm) Carver TFM 4.0 and Sunfire pre combo, and they sounded much better. However, there are obviously other issues at play there besides just the LSi impedance vs. the 3801's amps.

Jason

gatemplin

Jason, what equipment and software did you use? I would like to try that too for designing crossovers.

jcaut

I build DIY speakers, as a hobby. There's a program called Speaker Workshop, that allows you to measure speakers using a PC and a soundcard. You can read more about it, and/or download it here. I'm amazed that it is free, because the capabilities are pretty impressive. But, the quirky interface and lack of a thorough manual serve to remind you that it really is free, however. And though the program ITSELF is free, there are other required parts that you need, in order to actually do anything with it.

By measuring the impedance curve of an individual driver, you can derive the T/S parameters that you need in order to design a box. The program also allows one to take frequency response measurements. It has a crossover design and optimization program.

All of this stuff is accurate, but not very easy to set up. I've been fooling with it for about a year, and I've got most of it figured out.

Here's another screenshot:

jcaut

I can help, if you want to try and get started. Not that I'm that good or anything,:D but I can tell you what to look out for.

steveinaz

In Stereophiles review of the Lsi7, they also stated that impedance was actually more like 6 ohms, from the measurements they took.

gatemplin

Thanks Jason. I already have that program but havent used it much. I didn't know it could measure impedance, phase etc. I also build DIY speakers as a hobby. I have built a few subs and a pair of wide range speakers using the TB 871s driver. I am planning on building some more speakers in September (hopefully earlier) when Adire Audio's XBL^2 drivers come out.

scottnbnj

thanks much, this might do a bit to explain, after all we've heard about lsi mating habits, why my receiver ran warmer(not hot) with monitor 7b's than lsi9's(not warm).

)