What process did you use to integrate multiple subwoofers for 2 channel listening?

@golfnutz Updated -- https://systems.audiogon.com/systems/9064/edit

You're right!

Thanks. I have 3 subs. @millercarbon, I'm not sure what mistake you're trying to disabuse me of, but all I mean by integrate is make them sound good. Some of the technique won't just be listening but much will. From listening to moving/changing to measuring back to listening. 

you can set the crossover to about 80 and then adjust the volume levels.

That's a helpful bit.


@nonoise  Thanks for the reference.
@mmcely Thanks for sharing your technique concisely. I'll try it.

Just after I posted this, I found this very helpful and detailed discussion: https://www.thehifipodcast.net/episodes/episode-24-how-to-integrate-subwoofer

The problem I’m not able to solve, and perhaps the room’s physics make it impossible, is a +5db or more bass hump from about 73-92 hz. This is evident in REW and it’s also easily noticed with music. A tubby zone. The idea that one more sub would solve this is implausible. It will take a systematic approach to moving the subs and adjusting various things, and I'd bet a few hundred $$s that that fails too. But at least I'd know I had hit the limits of this room. Thanks for any approaches. I’ll ask over at the REW forum, too.

@golfnutz Great tip. I’ll head over to AVS and look for Enrico’s tips. I’ve been playing with a lot of parameters but not the filters as much. I thought those might be later factors — too complicating, early on.

@djones I’m not running any software that applies EQ. I was hoping to avoid adding that to the signal chain.

@whart — it may be that DSP is a necessary step. Thanks for your detailed process. There’s a lot for me to try in there. And yes, listening will be the final test, and at many points along the way.

@fittebd — thanks. Will check it out.

@jrpned Thanks for the white paper.

@miller the hump is one main problem. You are saying that (a) I don’t know my own goals or mind, (b) don’t know how to use words and (c) don’t pay attention. I think the final answer is actually not listed — that you don’t really want to help. You want to find clever ways to poke at me. I’d prefer for you to simply stop posting on my threads. The whole tone of conversations without you are more amiable and relaxing.  Absence makes the heart grow fonder. I think I'd like you more if you were not around. 

@mapmapn, I’ll take a look at audiokinesis. Thank you. I realize that putting them in various places may be key. I worked all day at that — and didn’t get rid of several troublesome areas.

@erik_squires I have a lot of GIK stuff, as well as Real Traps. I found I had deadened the room too much in the 1-4k range and so had backed off. Some of the traps have limp membranes so perhaps some rearranging could help so I can do as you suggest without killing the "air" of the room.

@hleeid I'm convinced I'll do a DBA, I just can't do it yet. I'm in a temporary room and will probably be able to move to another but not for 5 years. This makes a DBA impossible. I'm doing my best to optimize with 3 subs. If that is still 1 card short of a full deck (i.e., crazy) then I'll realize that and in 5 years will be able to correct the issue by selling the subs used and going for an array. Given the wide range of controls on these Rythmiks, I'm hoping I can do pretty well until I get an array.

@jmalen123 and @powemi2 Thanks for the suggestion process for the low pass.
@mapman, thanks for the Ohm stuff. I'll take a look.

FWIW, here's what I was able to accomplish after 6 hours yesterday:

5db null at 33 hz
6db peak at 77 hz
5db null at 155hz
5db null at 174hz
9db null at 208hz
10db peak at running from 379-594 hz

I put the graph on my system page: https://systems.audiogon.com/systems/9064/edit

Thanks to all for your useful posts. I appreciate them.

@golfnutz Good point — it seems like you’re suggesting start with one — using Enrico — then go to two, then three. I have the tools needed to do what you suggest. Comparing to the naked speakers is a good idea. This is what I’ve done in the past. (I have been doing REW sweeps since July of last year, including with moving the sub. At one point, I had the sub 4 feet off the ground to check for vertical effects.) I like your SPL graph. As for shaking the house, isn’t that our duty as manly-men-with-subs? ;-)

@mijostyn  I do really want to do this right. Because I just bought all my tube gear and powered subs, I will probably wait before buying a digital preamp with digital bass management capability and then selling off my active subs for passive subs. I see that if you’re right about this, I’m going about it the wrong way. But for right now, I’m looking for solutions to what I currently have. Down the road, perhaps I’ll change everything out for something you’re describing.

@mapman Mini DSP would be a decent experiment. I just have to absorb the idea of adding it to the signal path. It’s a question of which is worse — adding another thing or some bad curve sections.

@powemi I have a DAC I really like (MHDT Orchid) with a good tube and really nice upgrades by Grannyring. I really incline, as you say, toward trying to learn my room and my system. I want things to fit together organically, and I honestly enjoy moving a panel or twisting a knob and noting the change. I get in a headzone of iterative trials — I can go for hours, and all the while, I’m learning how physical space, quantification, and acoustic experience align. I would worry that a DSP would shortcut me out of this process. Still, I’m losing hair and if I pull too much more out…well…

@tvad Thanks tvad. I don’t know why Duke would want to advise me when I’m not buying anything. He’s got to be busy enough.

@tvad Thanks. I didn't know I could do that. Makes sense. I was under the impression that MC invented the DBA and Duke just happened to be selling it. His system page puzzled me because it seemed like I should be seeing Duke's stuff in his room but then I realized he made it himself.

@hshifi Thanks for your input. I'll try the crawl again but with three subs, I better get my knee pads. Another vote for DSP -- thanks! As for bass traps or diffusers, I have many -- 4 Mondo Bass Traps, 2 GIK corner traps, 2 GIK Q7 diffusers, 4 GIK HF limited bass traps, 2 DIY absorbers 4" thick, 2 ATS bass traps, 4 ATS absorbers. I've also made several more pillows (e.g. a giant dog pillow stuffed with R38). I've moved everything around everywhere and measured all the while. Dozens of hours or more. I've moved huge amounts of furniture and even brought in more bookshelves for more diffusion. Plus, so homemade deflectors home made from wood boards to tweak reflections.
Hiring someone may be the way to go. I understand how multiple subs are supposed to work and how bass waves move in the room. It's now a question of discovering what's efficacious, given all the factors.

@powemi Good point. I will use my ears. I'm developing a sympathy between measurement and listening. The reason I am mentioning the bass hump is that I can defnitely hear it. The problem with using one's ears for a deep null is that one may not realize very easily that there is missing information, because we tend to fill in the blanks with our brains.

@mapman -- exactly. It's the complexity that makes a sub crawl or just using my ears hard to fathom.

@audiokinesis Thank you for your questions. A few answers:

* I do not know if the bass bumpage is throughout the room. After a LOT of work yesterday, I got it down to about a pretty narrow peak which is +4db between 79hz and 93 hz with a +6.5db peak at 88 or so. In exchange for all my work knocking down a pretty big peak between 50hz and 80 hz, I wound up with continued/more nulls at 33.5 (-6.5db), 127 (-8db), 208 (-11db), 244 (-11db). These are now my major problems to figure out without retarding the bass progress I made.

* My front ported Salk SS 6M speakers are listed as rolling off at 35hz.

* These Rythmik F12SE subs have a wide range of controls, including variable phase, crossover, gain, low pass switch (50hz/24 vs. AVR12/80hz/24), a "Rumble filter,", Extension filtering switches for Frequence (14, 20, 28hz) and Damping (low, mid, hi). Details about these switches are here: https://www.rythmikaudio.com/download/PEQ3_sealed_quickguide.pdf

* I have a lot of freedom in this room. I did extensive listening, measuring, moving of speakers, etc. in the room and I think LP and Speakers are close to optimized but I’m open to revisiting.

Again, thank you for the questions. I feel like I made progress yesterday - I moved everything, turned and changed dials and knobs, moved treatments around, the works. I was systematic and cautious, changing one thing at a time. I listened at the end of the day and it sounded very satisfying. It’s now those big nulls which are leftover problems I feel compelled to solve.

Any suggestions you make will be experimented with ASAP. I'm a dog on a hunt.

@audiorusty So I have a DBA? I was confused because the first post to my thread from went to great lengths to dismiss "integration" and then lecture about DBA’s implying that 4 subs or more were best. I’m not sure if he was defining a DBA as "at least 4" or what, but I don’t care. I’d rather not hear more of that.
So, yes: I have three, they are assymetrical. I will try plugging the port. They’re rated down to 35hz.
The REL has a passive radiator. I'll try muffling it.

@golfnutz I’ll do that sweep. If you want to message me, I can share via email with you. Thank you very much!

@mapman

@hilde45 did I read correctly that your subs go down to 35hz and your mains also not much different in terms of low end extension?

Subs go lower than 35 hz. The mains are listed at 35 hz. I do not know their roll off slope. In the past, the addition of a single REL to these speakers always helped noticeably. Not dramatically, but noticeably.

You may be right that there’s not much to get from a 3 sub array. I’m definitely trying to test this out in the 30 day trial period for the subs.

To volume match, I need to see how I can get just the subs to play without turning off the tube amps.

No turntable.

If your mains are truly somewhat responsive into the 30s hz, benefits of using a sub at all is marginal to start with. The control flexibility of even one in your case (rhythmik) would help.

This is what Jim Salk said. BUT, I did notice a difference with the RELs. Let me add a report of the latest scan I did (I'm doing them right now):
I increased the bass about +5-6 db from 20-60hz, from nulls to small peaks (up to +3.5db) or so. This is just the latest scan and as you can imagine, pulling all those dips to the flat line or a little above is very hear-able.

Now if you are crossing over the mains at a higher frequency and offloading the low end below to the subs, then we are talking. That would have benefit of offloading work from you main amps which should be a good thing if done right.

I do not have the technology right now to do that.

@audiokinesis 

Thank you, thank you! for your help. I'm saving this email and printing it out.

Here's the result of my work before your advice, over the course of the day. It's the top slide on my system page: https://systems.audiogon.com/systems/9064/edit

Might it be a floor-to-ceiling mode? Do you have a lower than normal ceiling?

Oh definitely. 6.5' ceilings. I told this to Dennis Foley and he said, bluntly, "Get another room." Sigh.

Thanks for the compliment on the Salks! When I did extensive speaker placement analysis (with the help of brownsfan) I found that 6'4" from front wall was optimal. Today, I've added a few inches more and had some luck with that. But the bass hump ain't moving much. A little but not enough. Nulls still painfully deep.

I'll try that overlap cancellation thing. Had not considered it. The Rythmiks use a line-in RCA so not sure how to manage that with them. The Rel seems easy enough.

I'll try stuffing some foam in those beautiful front ports.

I am a bit daunted by the idea of wiring a capicitor but it is probably easier than I imaging. I'll save this email for future reference.

Good to know that 3 gets me in the ballpark. I was under the impression that the idea was "Get 4 or go home."

I'll try to elevate one of the subs....closer to the ceiling. If you know a good orthopedist, that might come in handy.

There is one sub presently closer to me than the speakers. I'll try to roll off the top ends lower and steeper on that one.

I'm glad you mentioned deliberate phase variation between the subs; I was worried about keeping them symmetrical, but since the room is going to be different where each is, that assumption doesn't really make sense.

@djones51 In the image I posted yesterday -- which I didn’t label specifically enough -- the orange "morning" line is speakers only.

Improvement from "Morning scan, without subs" to "Afternoon scan, with subs" mitigates the dip significantly at various points, e.g. pulling up a null by 10 db at 129 hz, by 8 db at 241hz. At other points, the later scan makes some things worse, but overall, the subs were helping.

Morning scan, there's another big dip between 2khz and 10khz. Afternoon scan mitigates that by a very large amount (varying, but up to 7 db mitigation).

@mapman -- I'm not against it, absolutely, but want to see if I can make a casserole with what I have and with the skills I have. I've spent a fair amount to have more than decent cables and DAC, so to add something into that mix is not necessarily about "polluting" the signal so much as adding an element that will change the character in unintended ways, even as it may be correcting other outcomes. But I hear you. Not ruling it out.

@tvad  That's a good object lesson. And I'm not aiming for Howard Hughes levels of cleanliness in line response. My issue is that I can hear the bump that I see measured. I tested that out last night -- I found a track of acoustic bass on a Chesky recording that goes up and down the scale, knew instantaneously where the muddy/tubby section was, measured the frequency of those notes on an analyzer and then compared to my REW graph. Exact match. If I can at least manage a couple unwieldy peaks, I will not have lifeless music, but I will eliminate flaws which my ears can hear. That's the goal.

That said, we all remember Hawthorne's short story, "The Birthmark," where his otherwise beautiful and kind wife has a birthmark which the protagonist insists on removing? Spoiler alert: the process kills her.

@mapman 

It helped that that room is thin dense carpet pad over solid concrete foundation. No floor resonance issues there like I have upstairs to deal with. If you have those, tackle those directly with isolation pads or equivalent under speakers.

I'm on concrete, too. 2/4 walls are brick. Not a symmetrical room but not much resonance.

@gosta  The guys on the hifi podcast just described a guy who spent 150k on a room for listening using treatments, and other tools and it still has problems. 

Been testing all day, off the computer. I've definitely improved things a lot with systematic adding in of each sub and then doubling the amount of treatment at ceiling first reflection points. I'm now dialing in a variety of room treatments. Be back when I can.

Update. After a lot of work yesterday, I’ve made good progress. I have no peaks over 4 db, and 4 nulls that are -5-6db and one big narrow one that is -8 db.

Scan results are on my system page:

https://systems.audiogon.com/systems/9064/edit

Basics of what I did:

• Started with a baseline scan. No subs.
• Assuming positions I had worked out before were adequate....
• Added 1 sub (REL). Adjusted in minute increments to (a) gain, (b) crossover, (c) phase -180 or 0.
• Added subs 2 and 3 (Rythmik). Adjusted in minute increments to (a) gain, (b) crossover, (c) phase, (d) various filter adjustments on sub
• Once those measurements were all optimized I adjusted:
• Front wall treatments, adding, subtracting, and moving.
• Side and other area treatments, same.
• Ceiling treatments -- doubled and adjusted position of existing treatments.

REW notes: Besides using REW to play sweeps and analyze the curves I tried something new (for me).

• I looked at the graph to identify the frequency where a peak or deep null was.
• Then, I’d play a constant tone and move a single treatment, facing the laptop screen display of the SPL meter, keeping an eye on the tone and an SPL graph next to it.
• When the the SPL graph showed a real decrease in a peak (or rise in a null), I’d leave the treatment there and then go back and do a sweep.
• Then, I’d repeat it and either shift treatment position or add more treatment there or nearby.

By doing this for the most problematic peaks and nulls, I was able to try new and more asymmetric combinations of treatment positions to really address the curve. In other words, I finally discarded my visual bias.

@golfnutz Happily.

Working very well in my room:

1 REL Sub (further away)
Phase: 180
Crossover: 100
Volume: 7 p.m. (3 tics)

2 Rythmik F12SE Subs (both behind and to the outside of each main, but not exactly equally):

Both set at:

Phase: 180
Crossover: 40
Volume: 7 p.m. (3 tics)
LFE Pass filter: 50hz
Rumble filter: Off
Extension Filter Freq: 20
Extension Filter Damping: Mid

@mapman

You have to jump ship on the measurements at some point.

I’m not sure if you’re giving me this piece of advice, because I mentioned (I thought), I’m going back and forth, measurements to listening to measurements, etc. Better measurements reveal themselves in a listening experience that reveals more than I was hearing before and it has raised my standards, both as a listener and in terms of what I knew my room was capable of. It’s easier to give me advice if I’m a "measurementalist" but there’s no way that impression could be fairly assigned to what I’ve been saying. Listening is the final test, because after all, I didn't buy a hifi rig so I could run sweeps!

Are these devotions from ruler flat response something you are hearing that affects your listening pleasure or is it something an electronic piece of equipment is telling you is not correct?

@arrowheadrss Not sure where I expressed a fixation on ruler flat response. That’s not realistic and I know it’s not desirable. I’m treating the measurements as one might treat a BMI reading. If it says you’re obese, well, who knows if that’s the right word, but it’s safe to think that dropping a few pounds is to your benefit.

These are  great suggestions and I really appreciate them. 
For the moment one thing is absolutely certain : with 6 1/2 foot ceilings there is no way that I am going to get a great result even with the technology you are mentioning. At this point my best option is to try to learn how to optimize my room with what I have. Because even if I have a more sophisticated tool it is only going to drive me toward recognizing a foregone conclusion, namely that I have the limitations that I’m already close to confirming, I believe. When I am able to move rooms, hopefully in a year or so, these tools may be much more appropriate.

@djones51 @soundsspectacular 

Yes, I listen nearly near field. I bought speakers based on how they sounded in this space. My stands are at 20" (not the usual, higher 24 or 27") and I sit a bit lower, too. I have carpet and ceiling absorption, too.

QUESTION: Bit of a side question -- At present, I have my REL hooked up to BOTH mono block amps' speaker terminals -- left and right. This has worked really well in providing left/right sides to my single REL.

However, now I have 3 subs -- two Rythmiks which hook up the the L/R on the PRE-amp, and the REL, still hooked up as it was.

So --  one Rythmik to Left Preamp RCA, one Rythmik to Right Preamp RCA, one REL to BOTH R&L Amps speaker terminals.

QUESTION: The REL has forced me to keep my monoblocks about 3 inches apart. Can I now just have the REL connected to one monoblock rather than two? I know that technically the answer is yes, because that's the design in the first place. But the other factor is that now two subs will be connected to one channel (say, Left) and only 1 sub will be connected to the Right channel. Make any difference?

@mapman  Interesting. I just listened to a couple of podcasts with Duncan/Darren and they are sub integration fanatics. They said that no full range speaker, even the Wilsons, are immune from some benefit from at least one sub.

Yes, I've moved them all over the place, etc. Bought sliders. Best. Tweak. Ever.

Thanks, Steve. That sounds like a great result!

@hleeid Thanks for your post. I tried some elevation but didn't help. Turned out that a different bit of advice from Duke was key -- partly plugging the ports on my stand mount speakers.

I'm happy to report that I now have no more than +/- 6 db peaks or nulls on my system and much less than that in the bass regions, most of the time. The combination of 3 sub placements, room treatments, and port plugging has dialed the room in to what I think are the best limits for this space. 6.5' ceilings made this a major project, but I have learned a lot. The bass is very accurate and full now.