I sent this to Brian Ding (Rythmik) and Danny Ritchie (GR Research), but I thought I might get some ideas from you guys as well.
The Rythmik/GR Research A370PEQ servo amp is a marvel of flexibility. But that flexibility comes at a price: no, not in dollars ($399 per each monoblock) but in complexity. Using the warble tones from Stereophile Test CD 2 and a Phonic PAA3 Personal Audio Assistant professional sound-level meter I have spent many hours trying to get the maximum performance from my combination of GR Research LS-9 open-baffle main speakers and three-stack per side open-baffle servo subs. But with the A370PEQ’s fifteen knobs and switches per side, some having a large range of potential values - - not to mention the effects of speaker placement - - the possible configurations are almost overwhelming.
What I (and, I believe, others) need is a procedure with a starting point and a series of steps. So, let me try this one based upon everything I think I’ve learned from the internet, Rythmik’s FAQs, etc. I am interested only in the best settings for classical music, not HT.
Starting point (one speaker at a time) for PEQ controls:
1. PEQ: OFF
2. CROSSOVER GROUP
a. DELAY: zero
b. CROSSOVER: eighty
c. LEVEL: 12 o’clock
3. EXTENSION FILTER
a. FREQ: 28
b. DAMP: Hi (Q=.5)
a. LOW: 80/24
b. RUMBLE: OFF (turn on later if woofer pumping)
1. Left main speaker and sub: ON
2. Adjust only DELAY, XOVER, LEVEL until smoothest response through 200Hz
3. Left main speaker and sub: OFF
4. Right main speaker and sub: ON
5. Adjust only DELAY, XOVER, LEVEL until smoothest response through 200Hz
6. Left main speaker and sub: Back ON
7. Adjust only DELAY, XOVER, LEVEL until smoothest response through 200Hz for both sides
8. If peak or trough after this, use PEQ to optimize each speaker separately.
9. Have a very Merry Christmas