Axiom Home Page Forums General Discussion Stereo M-60s with McIntosh amp

Has anyone used their M-60s or M-80s with a McIntosh amp? I picked up a used one a year ago that puts out 100 watts a side. It's running through an Acurus Act 3 preamp. The bass from it is amazing to the point that I didn't know the M60s could put out as much as they do with the McIntosh hooked up. But the soundstage seems to be different for some reason now. When I had them hooked up to the Act 3 and a 150 watts Acurus amp, the soundstage was always three-dimensional. Now it seems blown out. The music sounds good from either CDs or records, but the 3D quality seems to have gone.

I sit about 9 feet away from the speakers, and they're positioned about 7 feet across. I've tried repositioning them or toeing them in but nothing seems to help get the soundstage back to where it used to be. The only thing I can't do is move the chair back further away from the speakers because of the limits of the room. Because I can't move the chair back, it's making me wonder if the soundstage is just bigger with the McIntosh and I need to be back further. Since this is my first piece of McIntosh equipment, I'm not sure what to have expected. Any help is greatly appreciated.

Gain set too high on mcintosh.

Turn down on mcintosh and up on acurus.

It may be worth checking the left and right channel balance if you have an SPL meter. It could be the amp is weak on one side.

Mcintosh, overrated, but good resale value ... easy to get rid of.

Thanks for the replies, everyone.

I'm not sure how to even turn the gain down on the McIntosh. I know there are knobs on the back that seem to go from 1v to 2.5v but I don't know if those are the gain controls so I need to educate myself before I start changing any settings. I'll have to look it up on the Act 3 as well but maybe that's it. Appreciate the help.

Hi KCskins

I didn't see any model number for your McIntosh, however, it sounds like it is a power amp. If so, the volume is controlled by the preamp.

Most McIntoshes have cool blue lit power meters.

Change to 2.5v. That is the voltage sensitivity I would guess.

If it was at 1v you could be overdriving the input stage with the pre.

If you change to 2.5v and it gets quieter you are on the right track.

Some power amps have an input sensitivity switch or control knob. In your case it's a knob which makes it a bit harder to setup. You want the gain of each channel to be the same and set so that the full volume of your preamp produces the full volume of what the amp is capable of. The setup method I'd use is probably not the one you would as it involves a signal generator and a scope.

The method most use is to play a 0db test tone and adjust the amps sensitivity looking for a target voltage at the amps full output. You can google this. But the quick take is disconnect your speakers, set your preamp to about 80% volume, play a 1kHz tone (you can get files off the web), and measure the AC output voltage of your amp (remember to set the meter to AC). In your case if you have a speaker with a nominal 8 ohm impedance ... then the target voltage would be ~28 volts ... sqrt( 100W x 8 ohms )

Have fun

Yup, assuming it's not a 100wpc tube amp, in which case you don't want to drive it without a load.

Thanks again for the help, everyone. For those asking, the amp is a McIntosh MC58. I've bridged the first three channels for the left, right and center speakers, which makes them all 100w each. There are still two more 50 watt channels the amp has which I'm not currently using because I'm not running a full surround setup and we're only using it for stereo listening, or to watch TV.

I will be changing the voltage to 2.5 as soon as I get home today, and hopefully that works.