[rockadanny]

I have one ACI Titan XL integrated exceptionally well - crossed over at lowest setting. Just obtained a second (thanks Mike D.!). I get the asymmetrical placement thing, but I have two questions as relates to smoothest sub response:
1. Connect them as stereo subs (one channel per) or both channels to each (so both have same signal -> summed outputs)? Remember, crossed at lowest setting (approx. 35Hz?).
2. How to integrate the second sub? Shut off original sub and adjust second one for best integration with mains. Then turn on original and adjust both from there? Not sure how to begin or proceed.

[rockadanny]

FYI: I currently use a pair of ACI passive 65Hz passive in-line filters on my mains.

[Haoleb]

I would definetly use them as true stereo subs.

One of the best things you can do for subwoofer setup is to download the free program called "room eq wizard"

http://www.hometheatershack.com/roomeq/

I like to cross my subwoofers lower than the average, But I think 35hz is too low myself. Of course, its all about what you like but if your using 65hz highpass filters on your mains theres a pretty big gap between where that drops off and where the sub picks up.

[TONEPUB]

Id try running your mains full range and adjust the subs (run as stereo)
to bring up the low bass where the mains taper off.  Chances are good
you will get much better integration there as well....

[Duke]

I don't think it matters whether you run "stereo" signals to the subs or not, if the low-pass filter is set down around 35 Hz.  Very, very few recordings have stereo bass below 80 Hz, much less down at 35 Hz.   

My suggestion would be to set the volume level of one sub (preferably the one that will be getting the most boundary reinforcement) with only one main speaker playing, then duplicate that volume setting for the other sub.  This would be a starting point; from here, go back to both main speakers playing and adjust both subs together to fine-tune the overall level.  I figure that if both subs are at the same output level, their tendency to sum to a smoother overall response will be maximized. 

My understanding of how to apply Geddes' recommendations to this situation would be to set the level of one sub first (the one that will be getting the most boundary reinforcement), with both main speakers playing, then turn up the other sub just enough so that it improves (smoothes) the first sub without making the bass too loud.  Geddes also recommends using a different low-pass filter frequency setting for the subs. 

As an alternative, if you have one sub over on the left-hand side of the room and the other over on the right-hand side, along the sidewalls but not equidistant from the listening position, you might try running one of them out-of-phase with the other.  Or, if the subs have continuously-variable phase controls, run one of the 90 degrees shifted relative to the other.  The latter would be a David Griesinger type setup; the former a pooman's Griesinger setup.  The idea is to synthesize an inter-aural phase difference in the deep bass, because the ear/brain system will interpret this as spaciousness and envelopment. 

Duke

[chosenhandle]

About a year ago, I bought a pair of ACI Force subs. I put them in as a stereo pair. Here is my adventure:

This setup requires a test tone CD and a SPL meter and excel spreadsheet (or other)

1. Set nominal volume level (80db) to use as reference
2. Charted the main speakers (mine dropped off at 42hz with about a 6db rolloff)
3. Turned off mains, turned on subs
4. played with volumes settings (I matched the levels) and adjusted phase to maximize output level (it was amazing how much more output I could get when I messed with the phase). I assume max output meant that the least cancellation was happening (please correct me if I am wrong).  I then adjusted the gain on each sub to get to my reference 80db.
5. Set crossover point at 42hz on subs, with nominal rolloff.
6. played test tones on subs and charted the results
7. Moved the subs in the room. Repeated steps 4, 5 and 6. I moved them about 10 times and picked the best spot (smoothest output). (This was the most time consuming process!)
8.. turned on mains and subs, played test tones from 20 to 120hz charting results
9.. The results showed bloat  in the 40-50 hz range.
10. messed with sub crossover and rolloff and replayed/charted test tones about a dozen more times, settling in at 38hz crossover w/6db per octave rolloff
11. I live with about a +-3db from 20 to 120hz
12. For those who have nothing but time: mark the exact spot of the subs, then move the subs to your second best position and see if you can integrate them any better into the mains. Then the third, etc..... personally, I was so freaked out about the position of the subs and knob settings that I was afraid to move them!

I have not used spectrum analyzers or anything else on my system. To start out, this worked for me. By the way, I have corner basstraps (GK's) and wall panels to help with room acoustics. I am sure my charts would be a lot bumpier if I didnt treat my room.

that was my personal experience. I am not very experienced in stuff like this, I had to wing it.  It took about 2 days of dinking around. There may be a LOT of other better ways, but I thought I would share my experience.

[Brown]

Id try running your mains full range and adjust the subs (run as stereo)
to bring up the low bass where the mains taper off.  Chances are good
you will get much better integration there as well....

I agree. Connect directly from main speakers using solid core cable. Better than using ICs from pre IMO.

[rockadanny]

Thanks for the responses thus far folks.

TONEPUB - I originally had my mains run full range, but after experimenting with the passive 65Hz filters I found the mains to produce less distortion, thus clearing up the sound and better separation of instruments. I never would have thought I had distortion until I did this. But it makes sense - even though I personally feel that my mains are awesome speakers, those 6" plastic drivers just cannot cut the mustard with trying to produce the ultra-low frequencies. They seem better to me relieved of this duty.

Duke - Your responses actually sound like fun to try. I never thought I'd have fun working in this second sub. Maybe I will? Cool ideas. THANKS!!

chosenhandle - Excellent brute-force methodology! I like it. Brute-force can be painful and sweaty but ultimately very satisfying in the victory. Thank you for such a detailed explanation.

Now I can't wait to get home to try out these suggestions! (Hopefully I'll be able to find a gas station with gas on my drive home from the Atlanta airport.)

[satfrat]

I don't think it matters whether you run "stereo" signals to the subs or not, if the low-pass filter is set down around 35 Hz.  Very, very few recordings have stereo bass below 80 Hz, much less down at 35 Hz.   



Duke

Hi Duke, sorry but I need to disagree with your assessment that there's very little material at 80Hz. Using a Sunfire processor set at 80Hz (on a 20Hz input) and playing my Odyssey Lorelei's on "small", I'm geting driver movement on most all recordings. I'm even picking up sub action from my DirecTv all the time, especially on commercials. Could possibly just my setup but my ACI Force XL stays active quite a bit at 80Hz so I thought it worth mentioning, especially considering how I love the integration I have at that frequency.

Cheers,
Robin

[rockadanny]

satfrat - I believe Duke was replying speficially about my concern connecting subs in stereo (one channel per sub) as opposed to both channels both subs. I believe we all agree there is plenty of noise below 80Hz on many recordings. Correct?

[satfrat]

satfrat - I believe Duke was replying speficially about my concern connecting subs in stereo (one channel per sub) as opposed to both channels both subs. I believe we all agree there is plenty of noise below 80Hz on many recordings. Correct?

  Me thinks you're right. I need to read these posts more carefully. Thanks for pointing that out.



Cheers,
Robin

[rockadanny]

My suggestion would be to set the volume level of one sub (preferably the one that will be getting the most boundary reinforcement) with only one main speaker playing, then duplicate that volume setting for the other sub.  This would be a starting point; from here, go back to both main speakers playing and adjust both subs together to fine-tune the overall level.  I figure that if both subs are at the same output level, their tendency to sum to a smoother overall response will be maximized.

I did this as it made most sense to me (so far). Thanks Duke! Did not seem to smooth out the bass much but did end up sounding great! I also was able to fix my biggest issue, which was a -8 to -10db bass null around 55-65Hz with a couple of GIK 244 panels. Pic here:

http://www.audiocircle.com/index.php?topic=60994.msg545422;topicseen#new