Tubes with Infinity IRS Betas

SS amps like the big Threshold Class A mono’s with preferably ARC tube mono’s driving the mid/high panels is a well worn path. I recall Arnie Nudell voiced the IRS speakers with ARC tubes up top. The key is you need powerful ss amps to drive the bass towers, and reasonably powerful tube mono’s to drive the mid/high panels. Basically the more power, the better.

One solution for such an impedance curve is a set of ZEROs (www.zeroimpedance.com) which will put the Betas in the range that most tube amps can handle.

We were an Infinity dealer, everything except IRS
the Big CJ Premier 1 had the needed gruntbut sounded even better with an Acoustat amp driving the low end
as Melbguy says

imo more problematic is integrating the bass towers into the room and not ending up with a seriously screwed up sense of depth
i always took the Opus 3 depth of image LP with me when setting up..

oh ya, I still do !!!!

have fun
great speakers

rvito
Tubes with Infinity IRS Betas

When they were first shown in Australia many moons ago at the Amada Conference Room Artarmon, the importer Ceto from Audio Excellence gave the old propaganda speech before playing them.

In that speech before we listened he said after conversing with Arnie Nudell, many will ask why we have the big Audio Research mono blocks on the bass and the (just as big) Threshold monoblocks on the mids and highs.

It was because of the IRS Beta’s impedance curve, it sounded better this way in the mids and highs and the bass was still in control with the tubes on them, with the tubes on the mids and highs there was a distinct lack of hf extension, air and dynamics.

https://www.stereophile.com/images/archivesart/988BETAFIG1.jpg

This is what was said on Stereophile with VTL300’s on the mids and highs " with a rising output impedance with frequency will produce a sound that is much mellower in the treble"
You don’t want this as this is what we got with the AR’s on the mids and highs

And what they got with the Mark Levinson on the mids and highs
" Mark Levinson No.20.5 amplifiers produced a sound from the Betas possessing considerably more HF energy than the VTL 300 tube amplifiers".

I would suggest a good powerfull solid state with high Class-A ability, not the Krell plateau biasing class-A, I’ve never thought that system sounded like it should of.
But set class-A like the user adjustable Class-A Gryphon Antillion or the bigger Pass Labs XA series


Cheers George