Tube Amp for Martin Logan Speakers
Hi Bruce the Quad are not too bad http://www.stereophile.com/images/66Quadfig01.jpg when you look at the ML Monolith' http://www.martinloganowners.com/forum/showthread.php?6301-Impedance-curver-graph&p=69831&viewfull=1#post69831 Cheers George |
With the Quad 2805's your AR Ref 150 would be fine on the 4ohm tap as they are below 1ohm output impedance, maybe not so on the ML Monolith's http://www.stereophile.com/content/audio-research-reference-150-power-amplifier-measurements Cheers George |
Thanks George. Very interesting plots for the Quads and MLs. Looking at the Quads, I see the bass impedance spike is literally off the chart. Heck, it's almost an open circuit. I don't know, .... schlepping around a 75 amp to a dealer ... auugh. I ain't gettin' the warm and fuzzies. The MLs have one of the flatest phase angle plots I have ever seen. Even still, I would be concerned that my amp might be challenged driving the MLs because its impedance is incredibly low in the treble region, almost a short. So here, if I blundered into a combo involving the MLs and the Ref 150 and my back was up against the wall, ZEROs might help. So ... if impedance was doubled, the bass region impedance wouldn't be outrageously high. But jeez, impedance in the treble region is about 1 ohm. Even if doubled, we're still talking about 2 ohms. That's pretty low. I suppose the only way to know for sure is to try it out and see what happens. But why would I want to drop a ton of bucks on such an uncertain proposition, even with ZEROs. I gotta tell ya George, ... unless I read a lot of testimonials on A'gon declaring the Ref 150 and one of these ESLs is a match made in heaven, I would be very skeptical. Even if there were a number of approbations, I'd still call ARC and the ESL manufacturers to get a bead from the tech folks. It kinda raises a different question -- what ARE folks using to drive this ESL speakers? A hydro-electric plant?? Thanks, Bruce |
Robert Deutsch reviewed the ML Montis hybrid for Stereophile and concluded that despite the .5 ohm impedance at 20khz, the speakers could be driven nicely by the McIntosh 275 on their 8 ohm taps and even by the PrimaLuna Prologue Premium integrated amp. He didn't like the matchup with his Audiopax model 88s though. In spite of the impedance curve, I haven't heard of people having problems driving them and I haven't had that problem myself. |
That's because the McIntosh 275 has quite a low output impedance for a tube P/P amp at .57ohms from the 8ohm tap.(probably has a fare amount of negative feedback) But the Montis would still be a hard load for many amps as John Alexander's measurements state " The shape of the impedance trace will result in the Montis's top octaves shelving down when the speaker is driven by a tube amplifier having a high source impedance. This is why Robert Deutsch found that his Audiopax amplifier sounded too soft and lacking in definition." Cheers George |
