Question for those using McIntosh Power amplifiers with Martin Logan

McIntosh power amplifiers are different than most as they use audio autoformer which requires you to choose 2, 4, or 8 ohm tap to connect your speakers.

What is the best choice to use with Martin Logan speakers ? Spire shows impedance goes from 4 ohms to 0.8 ohms - do I use 4 ohms as nominal is 4 ohms or 2 ohm tap as minimum is 0.8 ohms.

Also read some people using 8 ohm tap with Martin Logan speakers?

For all members with McIntosh power amps, your help be appreciated.

Dan

I have always used the 8 ohm tap with the Vantage, Summit, and now the CLX's.

Oh, and the reason for the choice would be interesting as well...

Spires are rated at 4 ohms, so use the 4 ohm tap. Click the link to read about autoformers.

http://www.roger-russell.com/mcintosh1.htm#autoformer

Do not have McIntosch at front now, but my Audio Research at 8 ohms is too thick at bass with my CLXs. I use 4 ohms, and I do like it there.

using the 4 ohm tap with my Vantage and MC 275

miatancdan said:

McIntosh power amplifiers are different than most as they use audio autoformer which requires you to choose 2, 4, or 8 ohm tap to connect your speakers.

What is the best choice to use with Martin Logan speakers ? Spire shows impedance goes from 4 ohms to 0.8 ohms - do I use 4 ohms as nominal is 4 ohms or 2 ohm tap as minimum is 0.8 ohms.

Also read some people using 8 ohm tap with Martin Logan speakers?



For all members with McIntosh power amps, your help be appreciated.

Dan

Click to expand...

The .08 ohms is for those transient highs and does not reflect sustained performance. The bass and mid-range fall into the 4ohm area and that should be your starting point. However don't be shy about switching between the 4 and 8ohm taps and select the one that sounds best to your ear and does not create excessive heat from the amp.

Len44 said:

Oh, and the reason for the choice would be interesting as well...

Click to expand...

This is not a good answer, so I did not post the reason. Since you asked. I know very little about hooking up equipment. The professional installers are Cedia approved. They have been doing a great job with all my equipment upgrades.

miatancdan said:

McIntosh power amplifiers are different than most as they use audio autoformer which requires you to choose 2, 4, or 8 ohm tap to connect your speakers.

What is the best choice to use with Martin Logan speakers ? Spire shows impedance goes from 4 ohms to 0.8 ohms - do I use 4 ohms as nominal is 4 ohms or 2 ohm tap as minimum is 0.8 ohms.

Also read some people using 8 ohm tap with Martin Logan speakers?

For all members with McIntosh power amps, your help be appreciated.

Dan

Click to expand...

Dan,
I don't believe there is one correct answer as each Martin Logan speaker varies with impedance and frequency response and each McIntosh amplifier has its own sound signature. I have a pair of CLS's and when I power them with the MC275 tube amp the 8 ohm taps sound the best but when I connect them to my MC1.2KW's the 4 ohm taps work best. There is a subtle yet distinct difference between impedance taps, you will have to use your ears to decide what works best in your current setup which will involve components as well as room acoustics. Good Luck...
Rich

while I can't speak to your Mac gear the general rule of thumb with tube gear is to connect to the lowest output tap possible so as to not roll off the higher freq.

twich54 said:

while I can't speak to your Mac gear the general rule of thumb with tube gear is to connect to the lowest output tap possible so as to not roll off the higher freq.

Click to expand...

Twich,
In my system I experienced the exact opposite. I had rolled off highs when I connected my MC275 to the 4 ohm posts vs 8 ohms... weird...
Rich

mosttoysrk said:

Twich,
In my system I experienced the exact opposite. I had rolled off highs when I connected my MC275 to the 4 ohm posts vs 8 ohms... weird...
Rich

Click to expand...

In my system when connected to 8 ohm tap, highs were better + more dynamic.

Dan

I've tried all three, go ahead and experiment. You won't hurt anything. To me it was like Goldilocks and the 3 bears. The 2 tap was too thin, the 8 to fat. But the 4, just right for me.

Gordon

I agree with the 4 ohm tap also that is what I use on my 402

MMc

Knowing Gordon as I do and having had the pleasure to listen to his great MAC based system, I'd put great credence in his recommendation.

GG

On previous generation power amplifiers MC252, MC402 and MC501 the ML sounded better at 4 ohms. This being tried at my work ( stereo shop ) Do not know why but to me the new generation MC302, MC452 and MC601 on ML sound better at 8 ohm taps instead.... Maybe some design changes including thermotrak transisters part of the reason?

Dan

Personally and IMHO, i don't get the fascination of changing impedance knob settings depending on the speakers used. An audiophile power amp should be able to sound musical regardless of the speaker impedance (within limits ofcourse). Though ML speakers dip under 1 ohms at certain frequencies, this makes most tube amps gasp for air hence the often heard "loss of air" with the highs. An audiophile solid-state amp (e.g Mark Levinson and many others) would have no problems at all with these low impedances, freeing the listener to enjoy his/her music with any speaker of their choice.

It is in the tube amps nature to need an impedance match ( designing for 6000ohm and then run at 3000 make no sense ). The beauty with tube amps is that they might not be so flexible, but can be designed to give a perfect match with a speaker.

The price for, in my eyes, extreme open and beautiful sound is well worth pay'ed. I'm not claiming that SS amps cant play fantastic ( Pass labs come to mind ) just saying that that the BEST match I ewer had with ML is Tube's.

Tube amps are expensive, it can take time to find the right one, and they need care over time. They are not for all, but they are defiantly for me *s*

I'm presently running my Prodigy's on the 8 ohm tap of my McIntosh MC240. The music has weight, a liquid midrange, and crisp detail. It will play louder than you would want to stay in the room with. I have the amp's input gain turned down to about 60%.

twich54 said:

while I can't speak to your Mac gear the general rule of thumb with tube gear is to connect to the lowest output tap possible so as to not roll off the higher freq.

Click to expand...

My experience suggests that it is not tubes that cause the high frequency roll-off and associated loss of air, although tube amps are typically a little softer. It is because there is no way to match any output transformer equipped amp with a speaker whose impedence wanders down to 0.6 ohms. Using the 2 ohm taps helps a little but robs power which may be why each bump in my McIntosh power amps, MC2102 > MC402 > MC501, was an improvement. The best sounding midrange and bass will occur using a tap closest to the ML speakers listed nominal impedence. In the end, only a quality direct coupled amp will give you the jaw-dropping transparancy and "air" that Martin Logan speakers are capable of delivering.