Finally completed a project for my old man (dad) that’s taken 2 years.
Mainly took this long because I’m on the other side of the country, so I had to chip away at it on visits.
For his 2-channel system, he’s loved his ESS Labs speakers for 25+ years. They were built approx 50 years ago.
A couple years ago one of the Heil AMTs and one of the original woofers started to fail. So rather than repair the woofer I proposed we bring these speakers into 21st century.
I proposed we replace all woofers and Heil AMTs diaphragms and rip out the 50 year old passive crossover and I’d let software work it’s magic with HQPlayer for DSP crossover and room correction.
He was really nervous… but 2 years later (with lots of mistakes and learning along the way 
) it’s now working flawlessly on this Easter holiday visit.
Left and right are basically 3-way design, with pair of his favourite M&K subs handling <80Hz.
From the listening position, frequency response is capable of being flat from 20-20kHz and impulse response just about textbook, thanks to Audiolense frequency response and “True Time Domain” correction.
For target response we’re using a slight modification of the Harman Target Curve as his old ears prefers more treble and some other small differences. Tone control to his own tastes but done the proper way.
Roon & HQPlayer server on the other side of the house plays to HQPlayer endpoints over Cat6 around the house.
In this room, D to A is handled by Focusrite 18i20 Gen3 multichannel interface, connected to multichannel amp. Then direct connections to each driver.
Each driver individually time aligned, using measurements at the listening position (Earthworks M23 calibrated mic).
These ESS Labs Heil AMTs tweeters are truely magical. I’ll be getting a new pair for myself for my own DIY DSP crossover speaker build soon.
Most important thing is seeing the big smile on his face , happy with the results.
