Subwoofers and Phase Question For You Sub Experts

Excuse me. Each tenth of a millisecond is equal to about 1 foot. 

Thank you very much, ctsooner. I am honored that Richard Vandersteen thinks the distributed multi-sub approach (which is actually Earl Geddes’ idea that I’m using with his permission) has merit. 

Duke

Um, the speed of sound in air at ground level is generally given to be approximately 1,200 feet per second.


https://en.wikipedia.org/wiki/Speed_of_sound

1 millisecond = 1/1000 of a second, so 1.2 feet per millisecond or 14.5".


So 1/10 of a millisecond would be about 1.45"

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