Anybody else using a distributed array sub system?
I was just about to respond to zardozmike's forum post titled 'subwoofers' about suggestions for subs for Magnepan MGIII speakers but decided a new post might be more useful for him and others. I have Magnepan 2.7QR speakers and posted a similar question about a year ago. After reading his thread, I realized he was getting about the same responses I had received. All were very good responses but I thought a new thread detailing my effective solution may be more relevant and attract responses from other users of a distributed array sub system.
About a year ago I purchased the Audio Kinesis DEBRA (Distributed-Eq Bass Reflex Array) sub system from James Romeyn Music and Audio in Utah. Here's a link describing the system:
This system is expensive at $2,990 but well worth the investment. I rationalized the price by noting it's about the same as a pair of very good regular subs.
The performance of this system in my 23' x 14' living room is excellent. The bass can be fast, tight and tuneful for music or loud and impactful for music and home theater. The subs seem to disappear since there are no audible clues to their locations; the bass is very well integrated into the music and movies. From my personal experience, I'm not convinced of the reality of stereo bass but was willing to give it a try. I was originally thinking of buying 2 high quality subs such as Rhythmik, SVS, JL, Martin/Logan, Vandersteen or REL. I was skeptical of the DEBRA system at first but, after reading a lot of research about multiple sub systems on the internet, I decided to give it a try and I'm now very thankful that I did.
Because it is such an ideal system for me, and because I think it would work well in almost any room or system, I want to go into more detail about the system, its setup and the theory behind it. I have no affiliation with the company but will admit, after considerable phone and email time with the dealer, that I now consider James Romeyn a friend of mine but don't know if he feels likewise.
The system consists of the following:
A dedicated Dayton Audio mono class A/B amp rated at 950 watts @ 4 ohms with dual A&B spkr output terminals.
4 67lb. bass-reflex subs that measure a relatively small 23.75" H x 14.5" W x 10.375" D.
Each sub is ported on the bottom, supported by 3 spiked cones and contains a single 10" 4 ohm driver. The subs are designed to be facing, and within 2" of, the room walls.
The setup procedure is:
Sub#1 is hooked up and placed on its back (driver facing the ceiling) at the normal listening position. Music is played that has good and repetitive bass.
Walk around the edges of the room and determine exactly where the bass sounds best to you.
Attach the 3 spiked footers to Sub#1 and position it upright facing the nearest wall to the spot you determined the bass sounded best.
Sub#2 is hooked up and placed on its back at the primary listening position. With sub 1 & 2 playing, continue walking around the edges of your room and determine again where the bass sounds best to you.
Attach the 3 spiked footers to Sub#2 and position it upright facing the nearest wall to the spot you determined the bass sounded best.
Repeat this procedure for sub 3 & 4.
Small positioning adjustments may need to be made for each sub due to avoiding furniture and the WAF.
Once completed, final sub hook up is done in parallel:
Attach a single wire from the amp's speaker A's pos. output terminal and to Sub#1's pos. input terminal.
Attach a single wire from the amp's speaker A's neg. output terminal and to Sub#2's neg. input terminal.
Attach a single wire from Sub#1's neg. input terminal to Sub#2's pos. input terminal.
Attach Sub 3 & 4 using this parallel method on the amp's speaker B's output terminals.
I ordered single, high quality and low gauge speaker wire along with the sub system for a very reasonable price. Once the ideal locations for the subs was determined, I drilled holes in my room's floor to the crawl space below, and was able to hide the connecting wires.
I'm definitely not an expert on subs or room acoustics but, from my reading, here is how I understand the theory behind the distributed array sub systems:
The lower the frequency the longer the sound wave produced, or launched, into a room.
Since these waves can be even longer than the actual dimensions in many rooms, these low frequency waves bounce off room surfaces and the music may dictate subsequent bass waves being launched into this acoustic environment. These initial waves, their reflections and subsequent bass waves inevitably collide and cause 'standing waves'.
Areas in the room where sound waves meet can make the bass sound under emphasized, over emphasized or even totally missing (nulls caused by wave cancelation).
When one sub is launching low frequency waves from 1 specific location, areas in a specific room where bass response is not accurate will be numerous and predictable based on sub location and room dimensions.
Adding a 2nd sub to the room will decrease standing waves and increase bass accuracy and bass dispersion.
According to scientific studies I read, standing waves are reduced, and bass accuracy and dispersion increased, as more subs are used in a given room. Their experiments utilized more subs than anyone would even consider for home use. They basically concluded that the more subs in a room, the fewer standing waves are perceived and the better the bass quality and bass dispersion results.
However, they determined that most of the benefits are gained with the use of 4 subs, with only minimal and incremental gains in performance attained through additional subs. Due to practical room considerations, the researchers recommended 4 subs for an effective distributed array bass system.
So that's the equipment, set-up and the theory behind the DEBRA system and I can personally attest to its effectiveness in my room. I have 6 listening/viewing positions in my combination music and ht system in my living room. Bass response is equally good at all 6 positions without the use of acoustic devices (no absorbing or diffusing panels or bass traps) and without any electronic equalization (room analysis/correction equipment, software or eq). I should mention I've never had my system/room analyzed using a mike and software. From my purely subjective perspective, however, I'm confident the results would be good since I spent hours on the setup and critical listening from all six listening positions in my room. I would suggest this type of sub system as a viable alternative for anyone considering investing in one or more quality subs. The system is rated clean at 113 decibels at 20 hz. I've often heard and felt it go much lower. It feels and sounds clean and right but I can't verify the decibels or lack of distortion.
Sorry this turned out so long and windy,
Tim
Also, my system photos are old but I'll try to update them showing my current system (with the subs and new electronics) soon.
Or, for $2800 you can let the Audiokinesis Swarm 4-sub system do the heavy lifting. Absolute Sound review. http://www.audiokinesis.com/the-swarm-subwoofer-system-1.html. |
I can attest to the advantage of adding in some out-of-phase bass to smooth the bass curve. One thing I discovered when I set up my Maggie 1.7s is how the out-of-phase backwave took away that typical (and annoying) 100-200Hz in-room bass hump. Detractors often complain about Magneplanars’ "weak bass", and while lower reach is not a strong suit, the smoothness and quality of the bass beats most box speakers and also makes subwoofer integration easier. |
Noble100 wrote: johnnyb53,I didn't mention it in this thread before, but actually I also have a pair of small subwoofers to add some depth and slam to the Maggie 1.7s. The self-canceling nature of the 1.7s minimizes the upper bass hump that's so pervasive in room matching, and why many audiophiles have bass traps. Another advantage, however, is that it also makes it *easier* to match subs with Maggies. I have a pair of Mirage MM8s. These now-discontinued mini-subs were little gems--long-throw 8" drivers with twin passive radiators. The active driver occupied the entire sub enclosure except for the plate amp, which packed 1400 watts peak (340 rms) power. Controls were granular--continuous knobs for crossover (50-200 Hz), phase (0-180deg.) and volume. To dial in the phase, I put on "With a Little Help from My Friends" from the recent Beatles Mono reissue. I know the bass line from this song note for note and it dances frequently across that 50Hz crossover line. I played it one channel at a time and twisted the phase knob until it sounded right. Then I did the same thing with the other channel. At that point I had excellent-to-perfect (sounds perfect to me) integration between Maggie panels and subwoofers. You might say I dialed in perfect subwoofer integration with "A Little Help from My Friends." |
I forgot to mention that I was playing the recently released (Sept. 2014) Mono LP of Sergeant Pepper. Hearing the exact same bass line in each subwoofer was essential for this to work. One channel at a time, I turned the phase knob until the bass synced up between the 1.7 and the sub. Having a bass line that frequently crossed the 50Hz crossover point ensured that the quality and volume of bass would be seamless between the sub and panel. |
Noble100 said: In your case, I think the main advantages of using a distributed sub array instead of your dual MM8 subs would be even more consistent bass throughout your room and perhaps deeper bass extension that is more impactful and visceral.No argument here. If I had the space and funds I'd probably have a Swarm. However, these Mirage MM8s were a stone cold bargain for me. They retailed at $799 each and it showed--diecast frame long throw drivers and 1400 W peak each. I got them on closeout--when Klipsch or Audiovox started selling off and ransacking Mirage and its patents--for $250 ea. They are 9" cubes, sealed enclosures, with long throw 8" aluminum drivers that are flanked on the sides by same-size and materials (minus the motor) passive radiators. I have them turned backwards so the active drivers face the wall behind the Maggies with about 2" space to pressure-load the bass waves like a downfiring sub would. As it is, with the Maggies' dipole aspect canceling the 100-200 Hz in-room hump and the Mirage's 0-180 deg. continuous phase dial, I can get excellent and uniform integration, and together the pair is capable of adding a lot of thump. However, it doesn't go all that deep--probably around 36 Hz--and I'd love some subs that would take me cleanly and strongly into the 20's, but I have to stand pat and enjoy what I have for awhile. |
