Subwoofer/Mains Integration using A370PEQ

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Subwoofer/Mains Integration using A370PEQ
« on: 23 Dec 2017, 12:51 am »
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
    a.   DELAY: zero
    b.   CROSSOVER: eighty
    c.   LEVEL: 12 o’clock
    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

Early B.

Re: Subwoofer/Mains Integration using A370PEQ
« Reply #1 on: 23 Dec 2017, 01:08 am »
Awww, man!!!!  Are you saying I should have different settings on each amp to get optimal sound?  Yeah, I can see how that can get complex and tedious.


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Re: Subwoofer/Mains Integration using A370PEQ
« Reply #2 on: 23 Dec 2017, 02:26 pm »
I think so. My listening room is dimensionally totally symmetrical, but the left wall is an outside wall and the right wall is an inside wall. Pound on them and they sound different. I'm guessing they have different bass-leakage characteristics as well.

So, theoretically having separate subs/controls should be an advantage rather than an annoyance. But that requires an efficient funneling procedure and I haven't discovered that as yet.


Re: Subwoofer/Mains Integration using A370PEQ
« Reply #3 on: 28 Dec 2017, 03:38 pm »
For measuring the most accurate way is to use a microphone system with signals sent out of your speakers.

Room EQ Wizard (REW) is a free programme that does this. It requires a laptop, external sound card, microphone plus mic stand. It also requires patience in learning to use it effectively but this patience will be rewarded in the long term as any changes to your system will require re-measuring.

I know nothing of using subs but to find the best placement for my full range speakers I used 'The Thirds' set up as a good starting point (each speaker one third of the width and length of the room in from the walls, and listening chair in one third from the rear wall). I then measured with REW, moved the speakers 15cm or so and re-measured. I drew a grid and plotted each measurement until I found the best locations. I did this for each speaker separately and also for the chair (ears) too. I concentrated on the 0-500Hz range.

My room is a simple rectangular shape so I got some idea of the bass issues with this:

Once I found the best speaker and chair locations (actually more or less The Thirds positions) I looked at how room treatment, particularly soffit bass traps, could improve things. I ended up with twenty-one soffit traps (all four wall/wall corners and ceiling/wall corners) and four panels on each of the front and back walls plus two to prevent side wall reflections. That's a lot which I've accumulated over a few years. Using REW I was able to find the best locations for this treatment.

Even with all this there were still bass problems and I reduced these by using a Behringer DEQ2496 digital equaliser. Again I measured with REW and adjusted the equaliser to improve things.

There's a Circle member called Rodney Gold that knows a fair bit about using subs. It may be worth sending him a message.


Re: Subwoofer/Mains Integration using A370PEQ
« Reply #4 on: 7 Jan 2018, 05:06 pm »
Just a couple things I'd  start with a bit different than  what' you've got.
1. I'd "flip" the phase to 180   as a starting point
2. With the LS9's , I'd drop  the c/o point  lower (try 40 or 50hz) , this  setting  is the electronic point at which the slope will begin , you can always bump it up if need be.
3 Chane the  c/o slope from 80 24 to AVr 12.  Right now with the  dial set to 80hz and the slope set at 80/24,  youre dropping them off   at 24/oct starting at 80.  By  going to the avr/12 setting and the lower  c/o point, you  may  get a smoother integration
4.  I usually start with the damping  set to "Med".  You can play  with this later to fine tune  the control of your bass.   Setting it lower can  dramatically  improve the soundstage in some cases
5I usually start with the extension filter  at  20hz, as above, it's a middle point .  In this room,  once I  did some measurements with REW, I discovered I had quite a peak right at the bottom ( say 20hz).  Ggoing to the  28Hz setting really helped bring this under control but until you  do some measurements, it'll  be tough to   know what's  going on.

I know this is a PItA but  I also  do  sub s / speakers  separately. You probably don't have to  but  that was the recommendation I saw Danny  post   some time back (IIRC).   

When you   are trying to keep track of  what changes you've made, if you   don't have this yet , it can be a big help.   It's a printable  image  from @throwback  of the controls  on the A370 to help  record  your setting

Hopefully some of the guys with 9's and the OB H-frames can chimb in a give  more accurat starting points... still going to be  room   dependant  and somewhat subjective