Paul McGowan / PS Audio
In yesterday’s post I shared with you the fact we’ve made some changes/modifications in Music Room II.
I was quite surprised to find reactions to that news varying from outright betrayal, shock and horror, to ‘atta boy’ and everything in between.
Thank goodness no one in this crowd has any strong opinions. 🙂
The problem we were addressing in the IRS V is as well known one since the introduction of the speaker in 1985. The midrange planar ribbons called EMIM (Electro Magnetic Induction Midrange) can almost stretch as low as 100Hz, and it does, but down at that frequency there’s a ton of distortion as the driver has exceeded its practical limitation. IRS owners know to add the Infinity mandated external high-pass filter to their power amplifier inputs in an effort to reduce the problem.
Having on and off lived with these speakers for decades I am fully aware of this minor limitation and make mental allowances for it when listening.
But back to our story. A little recent history will help us understand what we did and why.
About a year ago our loudspeaker genius, Chris Brunhaver, convinced me it was time to retire the IRSV woofers in favor of more modern and better-designed woofers. Our chief engineer, Bob Stadtherr designed an entirely new woofer amplifying system that removed the IRSV servo and implemented a 1,000-watt amplifier for each woofer. We then used DSP to get the woofer system as flat as possible. Once finished, the changes were remarkable.
Of course, back in 1985 when the speakers were state-of-the-art there was no such thing as DSP nor were there woofers designed like the ones now used in the system.
Now it was time to fix the IRSV EMIM distortion problem and make yet another major improvement to this already wonderful loudspeaker system. Chris proposed designing a custom notch filter with a very specific Q, gentle enough not to be noticed, yet high enough to rid the EMIMs of their distortion without touching elsewhere in the frequency band. Once done we would have a hole in our response that would be filled in with the new woofers—drivers more than capable of excellent performance up to several hundreds of Hz ( a feat the old IRSV woofers were incapable of).
Here’s what the notch filter looks like:
With this network in place the distortion’s gone and the EMIMs have less to do thus helping them sound better overall.
Next was the task of moving the woofers closer (since they now operate at a higher frequency) and readjusting the DSP system. Here’s what they now look like relative to the wings:
How’s it sound? Wonderfull. Much punchier, cleaner, and (hard to believe) even moreresolving than I’ve ever heard it (and that’s saying a lot).
As I wrote yesterday, weekends are great times for rethinking your system and I am glad we spent the time and engineering resources to take our reference system up yet another notch in performance.
Change is never easy and often requires a bit of bravery. Consider that when it comes to making fundamental changes to one of the world’s great reference systems, I’ve got to balance the outcome to the reaction: a combination of social shaming, catcalls, compliments and kudos.
Change is tough but if you move in the right direction it’s the right thing to do.