Pass Labs int 60 vs. Luxman 590 uX ii

Hi  builder3

Again, want to emphasize that what's important is the performance, not the theory, but here goes.

The lower a speaker's impedance is, the harder to drive, the more likely an amplifier is to sag, or produce less output in that region than the rest.  The "ideal voltage source" theory, where the output is the same across all frequencies, regardless of impedance, will always fail if the speaker impedance is low enough. 

Here are the measurements for the 1037, which lets us talk about this with specific frequencies in mind:

https://www.stereophile.com/content/focal-electra-1037-be-loudspeaker-measurements

For this particular speaker, the hardest areas to drive are between 30 Hz and 300 Hz.  In this case the issue is more towards the true bass than mid bass.

Focal tends to make speakers which are "demanding" for amplifiers, especially in the bass/mid bass region.  Since bass is the largest signal swing in music and the impedance is lowest there, this is a tough to drive speaker.  Not as tough in absolute terms as others, but difficult nonetheless.  To some, these speakers will appear "discerning" of amplifier, and I worry audiophiles take it to mean they reproduce music better. 

In any event, where the impedance sags below 4 Ohms is a place to listen when comparing amplifiers.  However!!! Just because it produces less bass, is not disqualifying, you might like that, and it may make a better amp/speaker/room match.

builder3 Can you elaborate on your statement regarding the mid-bass, Erik.

Here’s the piece I find important.
Per Luxman’s website, the 590 has: Bipolar 3-parallel push-pull
But the 509 has:Bipolar 4-parallel push-pull
Implying a lower output impedance.

This is bi-polar v mosfet and the lower output impedance (amount of damping factor) can be a bit of a furphy builder3.
As the damping factor also comes down to the amount of "negative feedback" used (global or local), and size of the output resistors the output stage has, to what amp has the "lower output impedance" (better damping factor) it could very well be the Pass Int-60.

Cheers George

For some one who loves Pass, you just did Pass a huge disservice.

No modern amp company I know of has innovated along the lines of amplifier circuits more than Pass.  Attempting to reduce a Luxman vs. Pass to Bipolar vs. MOSFET trope is something no one should do.

Pass very much has a unique sound which has attracted many (not me) and it's nothing to do with how MOSFETs sound.

The Pass sound is unique by design, and it's not just the choice of devices used.

For some one who loves Pass, you just did Pass a huge disservice.

Really!!
No, you just been caught out not knowing what constitutes low output impedance (good damping factor) in an amp and were pulled up on it, that why your backs ups, everyone knows your a Lux pusher.

I actually don’t like the Mosfet sound, when Pass built Threshold bi-polar amps, I much prefer the good ones of those.

I actually own and use the pass int 60. It is a smooth and warm in the middle amp. At the same time is is very transparent. It tends to get out of the way of the music and you just listen. Bass is very controlled and doubles its power into 4 ohm. It has a tube characteristic, which I happen to like. I am using mine with the ls50 meta’s and the sound together is like nothing I have ever owned. I have never heard any of the other amps that have been mentioned, but I can tell you, you will not be disappointed if you go with the pass.