Subwoofers and Phase Question For You Sub Experts

The speed of sound is actually closer to 1100 ft/sec than 1200 ft/sec at standard temperature pressure at sea level. Which brings me to my Pop Quiz. For a free prize explain why placing bowls of very cold water out in front of the speakers on the floor improves the sound from the listening position. First correct answer wins a set of 3 brand new Flying Saucers on Afterburners for Windows. 🛸 🛸 🛸

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