[Mike-48]

I did some sweeps with the subs crossed at 36hz. I did both 12 and 24db slopes. Not too much difference. I feel like 44hz is a room thing. Seems to always be there.

Both subs on the front wall. The right sub is facing right, left sub facing straight ahead.

12db slope


24db slope.


The volume was not changed so I cannot understand the difference in volume. That’s a mystery to my ignorance.

So I feel like I should go back to the 12db slope and acknowledge the 44hz peak but look past it and bring up that trough above it. What’s going on at 125 I have no idea. 63hz is always the low point in that part of the frequency range. No idea what to do about that either. Maybe this is the point where I run the full frequency sweep and then play with reflections and then dive into a mini DSP?

I've missed a few posts. Did you adjust phase before making each graph? That is absolutely critical before looking at peaks and dips -- it will change them. And are the graphs of one channel (R or L)? I would look at each channel separately before thinking about a mono sweep.

To me, the 12 dB results look smoother. The sub is helping fill in the dip around 60 Hz.

To get a better picture of what's going on at 120 Hz, I'd run the sweep higher, to 300 Hz or even 500 Hz, well above the Schroeder frequency. It's a more holistic look at things, especially since by 160 Hz the 24 dB/octave graph is way down. That could be an artifact of reaching the end of a smoothed graph or it could be real. It would be good to know.

[ooheadsoo]

In your room, your mains are starting to fall off by 100hz. If play with crossing the subs higher and then play with the level to find the sweet spot where you can use eq just for the peaks.

[WGH]

That peak at 125 Hz is on your first graphs too, now that the sub crossover is lower it is easier to see.



Have you run the sweeps without the subs? The peak may be the Klipsch's.

[Mike-48]

That peak at 125 Hz is on your first graphs too, now that the sub crossover is lower it is easier to see.

Have you run the sweeps without the subs? The peak may be the Klipsch's.

I second that suggestion. A full-range sweep of the mains alone would be a useful baseline. I'm hoping their response really doesn't drop by 10 dB from 100 Hz to 200 Hz (unless you like a very warm sound).

[MONKEYWICKEDMONKEY]

I've missed a few posts. Did you adjust phase before making each graph? That is absolutely critical before looking at peaks and dips -- it will change them. And are the graphs of one channel (R or L)? I would look at each channel separately before thinking about a mono sweep.

To me, the 12 dB results look smoother. The sub is helping fill in the dip around 60 Hz.

To get a better picture of what's going on at 120 Hz, I'd run the sweep higher, to 300 Hz or even 500 Hz, well above the Schroeder frequency. It's a more holistic look at things, especially since by 160 Hz the 24 dB/octave graph is way down. That could be an artifact of reaching the end of a smoothed graph or it could be real. It would be good to know.

Hi Mike, phase on both is set to 0 (as they are both on the front wall). I stop the sweep around 130 or so as I’ve only been interested in readings up to 125hz for now. So that’s why it gets squirrelly above that.

I will re-run the sweeps higher 

[MONKEYWICKEDMONKEY]

In your room, your mains are starting to fall off by 100hz. If play with crossing the subs higher and then play with the level to find the sweet spot where you can use eq just for the peaks.

I tried this before and the huge bump at 44 hz shook the room.  Only recently I started peeling back to the 30’s.

[MONKEYWICKEDMONKEY]

That peak at 125 Hz is on your first graphs too, now that the sub crossover is lower it is easier to see.



Have you run the sweeps without the subs? The peak may be the Klipsch's.

I have but I will re-run then again 

[MONKEYWICKEDMONKEY]

I second that suggestion. A full-range sweep of the mains alone would be a useful baseline. I'm hoping their response really doesn't drop by 10 dB from 100 Hz to 200 Hz (unless you like a very warm sound).

I will re-run them sweeps with mains only tomorrow 

[Mike-48]

Hi Mike, phase on both is set to 0 (as they are both on the front wall).

Yes, that is logical . . . but unless it's based on adjusting phase as you look at frequency response, it's probably wrong.

The sub has a crossover, which likely has some latency. The subs are on the front wall . . . are the mains on the front wall, too?
 
If there is any time or path-length difference between the subs and the mains, relative to the main listening position, there will be cancellation and enhancement at frequencies centered around the crossover frequency. And that will affect your response curve in a major way. If you have not yet set phase that way, you may be able to get better -- possibly much better -- results by doing so.

The effects of this are minimized by some audiophiles, simply because not all subs have a phase control. Bad reason! It's like the old joke about the drunk looking for his keys under the lamp post. "Where did you lose them?" "Over there -- but the light's better here."

Sorry to be a broken record. Trying to fix frequency response without optimizing phase is wasting your time.

[MONKEYWICKEDMONKEY]

Yes, that is logical . . . but unless it's based on adjusting phase as you look at frequency response, it's probably wrong.

The sub has a crossover, which likely has some latency. The subs are on the front wall . . . are the mains on the front wall, too?
 
If there is any time or path-length difference between the subs and the mains, relative to the main listening position, there will be cancellation and enhancement at frequencies centered around the crossover frequency. And that will affect your response curve in a major way. If you have not yet set phase that way, you may be able to get better -- possibly much better -- results by doing so.

The effects of this are minimized by some audiophiles, simply because not all subs have a phase control. Bad reason! It's like the old joke about the drunk looking for his keys under the lamp post. "Where did you lose them?" "Over there -- but the light's better here."

Sorry to be a broken record. Trying to fix frequency response without optimizing phase is wasting your time.

I freely admit I don’t  know much about phase. My subs do have a rotary knob rather than a 2 position switch for it so it’s adjustable.

As for the positioning, the subs are inside the mains, roughly 12” further back from the listener (at the front baffle). So should I be adjusting phase to try to compensate for that distance? Is there something I should be listening for or is it adjust, measure and repeat?

[WGH]

Some people use Jennifer Warnes’ “Ballad of the Runaway Horse” to find the optimal positions for stereo speakers, the track may be useful for bass phase too. The procedure would take 2 people, one to sit in the sweet spot and one to twist the knob while listening to Rob Rasserman's taught deep bass line. The bass will be deepest when all the speakers are in phase.

You should use the CD or vinyl (excellent) for calibration but here is a taste:
https://www.youtube.com/watch?v=5BD7CFwiIsI

[MONKEYWICKEDMONKEY]

Some people use Jennifer Warnes’ “Ballad of the Runaway Horse” to find the optimal positions for stereo speakers, the track may be useful for bass phase too. The procedure would take 2 people, one to sit in the sweet spot and one to twist the knob while listening to Rob Rasserman's taught deep bass line. The bass will be deepest when all the speakers are in phase.

You should use the CD or vinyl (excellent) for calibration but here is a taste:
https://www.youtube.com/watch?v=5BD7CFwiIsI

OK, so I am adjusting each sub against each other and the mains for the deepest sounding bass. I will play with that. WOuld it also be possible to play a repeating deep bass drum and tune the left sub to the left main, then disconnect those and do the right sub to the right main? Just spit balling here...

[Carl V]

Another way to check for phase is Reverse your L speaker wires,
 i.e, make it out of phase. Now listen for less bass or the null.
do the same with the Right Speaker. 

And if your subs are behind the plane of your L & R....then yes you
will have a Phase issue.  How audible or Critical is your call.

[MONKEYWICKEDMONKEY]

Another way to check for phase is Reverse your L speaker wires,
 i.e, make it out of phase. Now listen for less bass or the null.
do the same with the Right Speaker. 

And if your subs are behind the plane of your L & R....then yes you
will have a Phase issue.  How audible or Critical is your call.

OK, I think I understAND. I will check these out when I get home this afternoon.

[WGH]

I think any recording with well recorded bass with some space between the notes will work. Jazz bass player Ron Carter comes to mind.

[Mike-48]

To summarize mine & others' posts, there are three main ways to adjust phase of the subs relative to mains. I've tried all three. All need to be done one channel (R or L + associated sub) at a time.

• Play music and adjust by ear. Fun, but not always accurate, in my experience, because it requires you to judge evenness across the whole bass range, by ear. (I hate to say that, because you can never listen to too much of Ron Carter's playing, IMO.)
• Reverse wires so a main is out of phase, then while playing a tone at the crossover frequency, adjust phase for the null (as heard at the main listening position). Less fun, but more accurate. Issues: You need to have a tone available at that specific frequency. And unless your sub has remote control, you need to be in two places at once (at the sub to adjust phase, in the listening chair to hear the null).
• Run a sweep, put a mic at the main listening spot, and adjust phase for maximum response at the crossover frequency. Fine-tune that by adjusting slightly for smoothest overall response. This possibly is the most accurate method, but is it really better than #2? Mainly in that it lets you see the peaks and dips of 10-20 dB that occur when things are out of phase. Also, you can watch the sweep (on a laptop) while you twist the phase knob, without running back and forth. I'd say it's the most objective method of the three.

Whatever you do, have fun! Welcome to the wonderful world of sub optimization.

[MONKEYWICKEDMONKEY]

To summarize mine & others' posts, there are three main ways to adjust phase of the subs relative to mains. I've tried all three. All need to be done one channel (R or L + associated sub) at a time.

• Reverse wires so a main is out of phase, then while playing a tone at the crossover frequency, adjust phase for the null (as heard at the main listening position). Less fun, but more accurate. Issues: You need to have a tone available at that specific frequency. And unless your sub has remote control, you need to be in two places at once (at the sub to adjust phase, in the listening chair to hear the null).

So for my ignorance sake, tun off all speakers except the left, wire the left main out of phase, then turn on the left sub and do a test tone at (in this case) 36hz and dial the phase until they cancel correct?

   

• Run a sweep, put a mic at the main listening spot, and adjust phase for maximum response at the crossover frequency. Fine-tune that by adjusting slightly for smoothest overall response. This possibly is the most accurate method, but is it really better than #2? Mainly in that it lets you see the peaks and dips of 10-20 dB that occur when things are out of phase. Also, you can watch the sweep (on a laptop) while you twist the phase knob, without running back and forth. I'd say it's the most objective method of the three.

Also for my ignorance, watch the peaks at the crossover frequency (36hz) to get the highest peak at that frequency and then slight variations to make it smoother

[/list]Whatever you do, have fun! Welcome to the wonderful world of sub optimization.

I just want to be sure I completely understand.

[Mike-48]

Yes, you've got it right. Since bass response will vary around the room, the listening and/or measuring should always be done at the main listening chair.

Then, of course, do the same thing independently for the R channel + R sub.

[ooheadsoo]

I tried this before and the huge bump at 44 hz shook the room.  Only recently I started peeling back to the 30’s.

If you're not using EQ, then you have to find your happy balance (compromise) between overall level and the size of the peaks.  Measuring the mains by themselves is a must, so you know what the actual additive contribution of the subwoofers is.  The HT approach is to find the subwoofer settings that provide the maximum in phase contribution to the system, and then EQ down the peaks.  The "music" system approach is to just find the best compromise of overall level and minimizing objectionable peaks without EQ.  In a dedicated room, bass trapping is pretty normal practice irrespective of HT or music purposes.

There is one other thing that I've never heard anyone mention - there's a chance that you don't have a good placement option for a second subwoofer.  For example, I also have an open room, and I gave up running a second subwoofer in my system because the only spots I had available for the second sub resulted in destructive combing effects that I felt were clearly a net negative, no matter how I set the phase or crossover point.  The system simply sounded better with 1 subwoofer. 

Measure 1 sub at a time and measure the combined system results of each. 
Here are basic measurements I'd like to know if it were my system:

• mains alone (or single main speaker if you prefer)
• sub 1 alone
• sub 2 alone
• mains with sub 1
• mains with sub 2
• mains with sub 1 and sub 2

And you get to play with the crossover settings on each sub as you start to combine them with your mains.  This is just for 1 placement.  Aren't we having fun?  Tuning bass with subwoofers is a real riot 

[MONKEYWICKEDMONKEY]

Yes, you've got it right. Since bass response will vary around the room, the listening and/or measuring should always be done at the main listening chair.

Then, of course, do the same thing independently for the R channel + R sub.