Subwoofers and Phase Question For You Sub Experts

Hello Duke,

Thanks for clarifying the awards your AK Swarm system has received, all well deserved. If you don’t mind, it seems like a few things need clarifying about attaining good bass response performance using subs.

The first issue concerns the timing of the bass reaching our ears at the listening position. Mijostyn stated:"Ideally the sound from the sub should reach the listening position at exactly the same time and at exactly the same phase angle as the woofers in the satellite speakers."
It seems to me that some people are stating false information because they’re assuming that bass soundwaves behave and are perceived by us exactly the same as midrange and treble soundwaves in any given room, specifically as it relates to timing and arrival times. It’s my understanding that bass soundwaves behave differently than mid/treble soundwaves in any given room and that we perceive them differently, too. For phase, I understand I can optimize this by adjusting the continuously variable phase control on the amp as well as sequentially inverting the phase on each sub to determine whether or not the inversion of one specific sub’s phase improves overall bass performance. Would you mind clarifying?

The second issue concerns the use of bass room treatments and room correction software/hardware. I currently use the AK Debra 4-sub DBA system in my room without the use of bass room treatments or room correction and I consider the bass performance near state of the art both for 2-ch music and HT surround sound.
However, I recently had my room analyzed by GIK and they recommended that I place stacked versions of their bass traps (called TriTraps) in all 4 corners of my room along with 2 bass trapping 5.25" thick panels (called 244 panels) along both the front and rear short walls in my room. Their remaining suggestions were an even distribution in the room of absorbing and diffusing acoustic panels for the midrange and treble from my main speakers.
The total assortment of recommended room treatments is about $2,500 and I was initially going to not include any bass treatments to save money but also not to negatively effect the already very good bass performance in my room.
I’ve since reconsidered and decided to include all of the bass room treatments on my order. My current understanding is that these bass room treatments will only have positive effects on my perception of the bass response performance in my room, with no negative effects. I still have no desire to utilize room correction of any type but am under the impression that room correction is also completely optional and will have no negative effects on the bass performance of 4-sub DBA systems. Do you agree with this?

Thanks,
Tim

Hi Rooze,
Rather than challenge other's assertions I will describe what has worked well for me in my room(s) and cars with various subwoofers over the years for getting the best integration.  
It really starts with the subwoofer- design, performance and controls.  
I have had the best results with sealed subwoofers that are designed to be corner loaded to yield their flattest response.  A sub that is easier to integrate will have a wide flat response when positioned properly.  
My last in home subwoofers were JL audio and they are sealed design with a very flat useable response.  These two aspects make them more musical rather than having peaks in the response that prevent them from disappearing.  
With a sealed design and a flat response the next thing is a continuously variable phase control- 0 to 360 on the dial. This is a requirement- more later.  I have never been able to satisfactorily integrate a subwoofer that only had a 0-180 deg. switch.  
When you have these fundamentals I had no need for DSP or room correction of any kind.  I have tuned subs with these assumptions with DSP and switching on the correction did not improve the sound.  
Tuning- get an app or RTA software and a microphone for a laptop for example.  Get a CD with full spectrum pink noise (the sheffield labs "my disk" for example.  
Now play the pink noise through your speakers (no subs) at moderate / high volume and measure their response from you listening seat.  
Note the frequency where the bass response drops off and is ~ 3db less than the midrange frequencies- e.g. 65 Hz.  
Place your subs at the room positions where they sound the best and most even at your spot.  
Turn on one sub at first and set the crossover for your measured frequency- e.g. 65hz.  
Turn the sub up higher than normal and take a system measurement with the pink noise track again.  
Look for the behavior at the crossover- peaks and valleys.  Back off on the crossover until you see a "valley" in the response, then slowly bring it back up again until the response is smooth. 
Then adjust the level until that is smooth. 
Here comes the fun part and the secret sauce for perfect integration. 
Play some music (loudly) with extended bass beats.  I use gnarls barkley "gone daddy gone" or new order "blue monday" 
Set the continuous phase to "0" and listen, take notes about the bass beats- tight, blurry, weak? etc.  now rotate the phase dial ~ 45 degrees, sit back and take more notes.  listen to where the bass is clearest and tightest.  You are trying to "time" the sub to your main speaker at the crossover frequency.  Once your notes say you have the best position - e.g. -45 degrees, from there rotate it 1/16 turn in either direction and see if it can sound any better.  
Once you have it dialed in the sub and mains are in perfect sync at the crossover frequency.  bass will be tight and powerful and there will be no muffling or cancelling.  It will sound impactful without effort.  Take note and log of all the settings. 
Now add in the second sub - you are now going to integrate the second sub into your "integrated system".  Repeat the same procedures changing only the settings on the second sub. 
Practice, be patient, take notes and have fun!  Once you nail this you will have the best sounding subs you can have !   

Tried the "swarm" approach and moved four subs into the room but unfortunately found out that they all have about the same tops and dips wherever placed (+/- 20 db from 25 to 100 Hz). So not much of an improvement. Room eq necessary.

" Tried the "swarm" approach and moved four subs into the room but unfortunately found out that they all have about the same tops and dips wherever placed (+/- 20 db from 25 to 100 Hz). "

Did each sub have the same in-room frequency response curve regardless of where you placed it, or did each one have a different frequency response curve but with the same amount of variation? (+/- 20 dB... that’s a lot of variation.... I don't recall ever measuring worse than +/- 10.)

Did you measure with all four playing at the same time?

Can you tell us about your room and approximately where the subs were placed within it?

Thanks!

Duke

noble100:

 The truth is that the 4-sub Distributed Bass Array (DBA) Concept actually works like a proverbial charm! There are no ifs ands or buts, no maybes, no under the right conditions, no excuses, no fear and loathing, no terms, no conditions, no stipulations, no hidden clauses, no fine print, no oils and no qualifiers whatsoever.  
      It's the cat's pajamas, the bee's knees, good as gold, tits, right as rain and too legit to quit. I believe it's the gold standard of sub systems that all others should be judged against.  
    Based on the 4-sub DBA's near state of the art bass quality, I actually continue to be amazed that it isn't more widely known, accepted and utilized, especially by fellow Audiogon members who are typically keenly aware and accepting of high quality audio related concepts, technology and methods they can utilize to increase the performance of their systems.  

Ain't it the truth.

I struggled for so many years looking at so many different things all of them ultimately running into the same fundamentally immutable physics problem. Well the thing is it really is a fundamentally immutable physics problem. So whattre you gonna do? Give up! And I did. Gave up all hope.

For years.

And yes of course I know all about all the wonderful different subs, including the magical REL, and EQ, and bass traps, and all that jazz.

What part of fundamentally immutable physics do these people not get?

I had come to view the situation as so hopeless that when first reading about this, right about a year ago now, I assumed it had to be just one more dead end. But you never know. So I read. And read. And read some more. Dang. This just might work. So I read a ton more. Read Toole, et al, read every post by Audiokinesis, read all the reviews, read the threads. 

All the physics, all the psycho-acoustics, the measurements, every single bit, it all made sense. Solid, compelling, logical sense.

So I decided to go for it. DIY. Might as well. And Duke is all thanking me for the leap of faith.

The what??!? So of course I had to tell Duke faith had nothing to do with it. No sane sensible man of science could look at this and come to any other conclusion than its gonna work. Just as surely as no other solution can possibly work, this solution cannot possibly fail to work. The laws of physics would have to be re-written. Something that is not happening any time soon.

That said, still it is hard to fathom just how well it does work. Last night listening to the 20th Anniversary 45 of Jennifer Warnes Famous Blue Raincoat it was absolutely freaking amazing the way the drums are no longer this thud thud thud that moves a bit left or right but actual 3D drums with skin and case and body and its not a dull thud but a clean impact that reverberates across the skin so that you feel and hear every up and down movement of the skin, and its not one sound or even one event its the wave moving out across the skin from where it was hit and then reverberating up and down and this is something you can see with your ears, its right there in the room which is completely mind blowing because as much as you know there are 5 subs plus the two speakers there is no sense of that, none whatsoever, its all just one seamless presentation, the drum and the skin and the room, the all-enveloping room that has erased the room you were in so completely its not the performers being there in your room its you being in theirs. And that's just the one whack. I could go on like this paragraph after paragraph on literally every track of every recording on the shelf.

The DBA approach is so superior to everything else that this one thing has transformed my system from where the bass was easily the worst weakest lamest thing about it to one where its the strongest most astounding aspect- and we're talking not because anything else is lacking but because the bass is just that crazy good. And not just because of any one thing like impact or extension or articulation or any of that but all of it together. We're talking play an absolutely average ordinary record and watch your guest move forward to the edge of the chair lean in fascinated and exclaim, "The bass!" 

And yet, as surprising as all that is its nothing compared to how stunned I am to stop and think this isn't some brand new thing just discovered last week. It wasn't even new when I first heard about it a year ago. Its like 20, 30 years, something like that, depending on how you want to count. From the PhD thesis or the commercial use or whatever. Not here to split hairs. We have people for that. All they do. Forest for the trees. 
 
Forest for the trees!

Everyone should be doing this. Or at the very least, everyone who has not tried it should maybe hold off until they do. Or if not that then at least take into consideration one or two of the dozens of compelling lines of evidence and reasoning behind this before spouting the usual irrelevant nonsense.

But no. Forest for the trees. Boggles the mind.