Driving LSi series speakers with vintage amplifier? (HK 730)

Crowsby

Hi all,

I've got a vintage Harmon Kardon 730 with twin power, and lately I've been seeing some LSi-series amps (LSi9 in particular) come up on my local Craigslist. Do you think this amp would be able to do them justice? From the article linked, here are some of the power stats:

The power amplifier is a direct coupled (DC) complementary design (h/k’s first). It is a very low NFB design, which does not have as much ultimate gain, but it ensures greater power reserves and lower noise. The amplifiers are nominally rated at 40WPC, but using modern measurement methods, I found it was capable of 90 watt dynamic peaks (+3.25 dB), and the amplifier output is fairly stable to 2-ohms. Being a DC amplifier, however, it is more sensitive to varying loads than something like the CC Marantz 2230 or h/k 820. h/k’s claim for the frequency response (4Hz – 130kHz) seems to hold true with test loads.

I've currently got a pair of rti4's hooked up to it, and they have never sounded better. And the amp hardly seems to be working at all; anything over 25% volume sounds way too loud.

tonyb

You'd probably be ok at moderate volume levels but the LSI9's are the one speaker in the LSI lineup that has varying dips in impedance....which the description of that amp says it doesn't like.

Personally....I'd get a better amp.

PSOVLSK

tonyb wrote: »

Personally....I'd get a better amp.

Or maybe look at the LSi 7's instead of the 9's.

The 7's cost less, are easier to drive, and some people prefer them over the 9's.

I've owned both the 7's and 9's and if I was forced to pick, I guess I'd go with the 9's, but it wouldn't be a no-brainer decision.

stretchl

PSOVLSK wrote: »

Or maybe look at the LSi 7's instead of the 9's.

What about that set of LSi-15's the guy's selling in Appleton, WI for $500?

PSOVLSK

stretchl wrote: »

What about that set of LSi-15's the guy's selling in Appleton, WI for $500?

A step up the chain, but then I might be back to agreeing with Tony that the H/K will work, but not be optimal. I drove a complete LSi 5-channel setup with and H/K7300. Sounded great, but man did the AVR get hot. Sound quality improved when I added external amplification and room temperature dropped a few degrees as well, which is always good during a Texas summer. LOL

Plus, placement becomes more of an issue. Room size could be a factor also.

Great price on the 15's though. No doubt about it.

Crowsby

Thanks so much for the feedback all; I think I'll be holding off. Also, I just bi-amped the rti4's and it really seemed to make a decent-sounding setup even better.

As a side note, I was astounded to hear the difference an amp can make. I previously had the rti4's hooked up to a Sony HT receiver, and while they didn't sound bad by any means, they've taken on a completely new life with the 730.

ZLTFUL

Crowsby wrote: »

Thanks so much for the feedback all; I think I'll be holding off. Also, I just bi-amped the rti4's and it really seemed to make a decent-sounding setup even better.

As a side note, I was astounded to hear the difference an amp can make. I previously had the rti4's hooked up to a Sony HT receiver, and while they didn't sound bad by any means, they've taken on a completely new life with the 730.

So what second amp and active crossover did you go with? Because if you are thinking that you are bi-amping using an AVR, you aren't. EVen passive bi-amping with an AVR is just dropping the actual power output of each channel being driven.

geppy1

A AV is not iin the same universe as a 730 The 730 is one of the best sounding vintage recveivers there is and has not problem with 4 ohm loads There are two runs of the 730 One sounds a little brighter, the other sounds much like a tube amp. I really wish I had kept my last one.

cnh

I own an HK 730 and though it has great headroom and considerable power for a 40 watt x 2 amp. I'm not sure how well it would drive LSi-9s. It will drive them but not to their potential. As mentioned it could probably manhandle the smaller Lsi-7s but their impedance doesn't dip as low as the 9s.

Give it a try but lay off the volume knob. This is a nice sounding receiver. Not sure HOW you would distinguish between the two models geppy mentions above. Any more info on that?

cnh

Crowsby

ZLTFUL wrote: »

So what second amp and active crossover did you go with? Because if you are thinking that you are bi-amping using an AVR, you aren't. EVen passive bi-amping with an AVR is just dropping the actual power output of each channel being driven.

Whoopers, you're right. I'm using the A + B terminals, so it'd be considered bi-wiring. The sound did improve noticeably (comparing the bi-wired left side to the conventionally-wired right side in mono mode), but perhaps I can chalk that up to doubling up the copper (16AWG).

tonyb

I'd be careful with a vintage piece running both a+b to one speaker as a getto bi-amp. When you do this, as with a lot of vintage pieces, they don't like anything below 8 ohm when running a+b, which the LSI's certainly are not.

F1nut

but perhaps I can chalk that up to doubling up the copper (16AWG).

Yep. Like Tony suggested, running A+B probably isn't the best idea, so take your doubled up speaker cable and run it off of A alone.

Crowsby

Quick follow-up on this: I found a fellow who was selling some LSi15's in amazing shape for $400 on Craigslist. Downside was that it was a 300 mile drive away. Upside: They sound amazing, absolutely jawdropping, compared to the old RTi4's I had in the living room. The vintage H/K 730 doesn't seem to have any problem driving them; I can't foresee ever needing to turn the volume knob over 50%.

cnh

Congrats, that's a great price. But it's hard to believe an HK 730 is getting the best that you can out of the towers.

cnh

Mikey081057

I have driven my modded lsi 9's with many different sources:

Marantz 2385
Marantz 2252B
Yaqin MC100B
Yamaha M80

They have sounded ok with the lower wattage amplification but really sing with the M80 and 2385. They will generate some heat, so make sure you have adequate air circulation around whatever you drive them with.