Dual vs single sub

As I stated earlier I have 4 JL Audio F-113 Subs. The JL mic is placed at the listening position and I calibrate each sub individually. Then a little fine tuning with the DEQX for delay, gain, crossover, phase and crossover slope and then by ear.

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millercarbon,

     Yes, you'll be amazed just how well it works. Have you given any thought about positioning your 4 subs in your room? If not, I can detail the process I used that worked out very well.

Let me know,
    Tim  

The one sub I have now was a nightmare to place. Because: one! With one you can move it around forever and never find the right place. I know. I tried. With four though....

From what I read they seem to work best distributed asymmetrically around the room. I'm thinking one front wall near the left corner, one right wall near the front corner but further from the front than the left one is from the side. Asymmetrical. Then one along the left wall further back than the sweet spot but not far enough back to be the same distance from the back corner as the front right is from the front corner. More asymmetry. Finally the right back one same deal, maybe a little further back than the one on the left. More asymmetry, more modes, more better.

As cool as it would be to play 3D asymmetry I think putting one up on a stand near the ceiling is aesthetically speaking a bridge too far.

I don't mind wire on the floor which is good because drilling holes is for me a tunnel too far. 

millercarbon,

     From what I’ve read about DBA systems, I believe your asymmetrical sub positioning/distribution plan will create more complex patterns of modal behavior in your room, resulting in decorrelation due to the smaller and more numerous bass peaks and dips present, which will be perceived as smooth, natural and seemingly effortless in-room bass response that is capable of reproducing fast, solid and taut bass just as accurately as deeper, more sudden and more powerful bass.
While I think you should get good results from your planned asymmetrical approach, I think it’s important you know that I’ve never actually tried this configuration with my subs in my room.
Just in case you’d like an alternative positioning plan that I know works, here’s how I positioned mine:


I removed my main speakers from the room, hooked up sub#1 and placed it at my normal listening seat position on its back, with the driver faced upwards.

I played some music with good and repetitive bass at a moderate volume and, beginning at the front right corner of my 23’x16’ room, I walked slowly across my front 16’ wall listening for the exact spot where the bass sounded best to me (the most natural and pitch accurate without being exaggerated or attenuated). I took my time and walked from right to left numerous times to verify the best spot. Once verified, I placed sub#1 at this exact spot with the driver facing, and less than 2 inches away from, the front 16’ wall.

I hooked up sub#2 in-series to sub#1 and placed sub#2 at my normal listening seat position on its back, with the driver again faced upwards. At this point, sub#1 and #2 are both active.

I played some music with good and repetitive bass again at a moderate volume and, beginning at sub#1 (now located about 2’ away from the front-right corner of my room along the 16’ front wall), I walked slowly across the remaining space along the front 16’ wall to the left front corner then turned left and continued walking from front to back along the left 23’ side wall of my room, listening again for the exact spot where the bass sounded best to me. Once verified, I placed sub#2 at this exact spot with the driver facing, and less than 2 inches away from, the front 16’ wall.
This completed the placement of both subs connected in-series to the first of the Dayton amp’s two sets of speaker outputs.

I continued this sequential sub positioning procedure for sub#3 and sub#4, with first sub#3 placed face up at my normal listening position and finally sub#4 just positioned at the exact spot I determined the bass sounded best with the first 3 subs playing the same musical content that had good and repetitive bass. This resulted in sub#3 sounding best along my left 23’ wall about 2’ away from the rear-left corner and sub#4 sounding best along my right 23’ wall also about 2’ away from the rear-right corner. So, subs #3 and #4 are located directly across from each other along opposite and parallel 23’ walls.

The results of this procedure in my room were so good that I never bothered to do the final procedure step of checking if the system sounded better with the phase reversed on one of the 4 subs as Duke and James Romeyn suggest.
I’ve been enjoying the excellent bass of the Debra bass system for almost 4 years now and I still haven’t felt the need to complete this step. The reasons are that I really have a difficult time imagining how the bass this system reproduces could be improved upon for music or ht and I really don’t want to jinx anything. If it’s not broken, don’t try to fix it, right?
Hopefully, Duke or James will chime in on their recommended DBA system setup methods and tips, too.

I’m looking forward to hearing your thoughts on your new custom DBA system.

Tim

Audiokinesis, It always helps to know what ideal is to make the best compromise in any given situation. 4 subs at 4 foot intervals with the outer two in corners does not approximate a linear array. It is most definitely a linear array up to 125 Hz or so. If you review the acoustical properties of linear arrays you will note that they throw very little acoustic energy off their ends almost totally killing any refection off the side walls of the room. No other array does this in any dimension.  The best you can hope to do in any enclosed space approximating a livable room is to control primary reflections and since they have the most energy that represents 90% of the battle. Of course most people are stuck with a rear wall. My point is that all the room treatment in the world will not stop that reflection in the subwoofer region. The wavelengths are simply too long. Putting subs all over the room simply creates more primary reflections. For most people with normal rooms digital room control is the only way they stand a chance of getting flat bass at their listening position. The horizontal linear array minimizes the problem to a degree no other set up can and it increases efficiency at least 6 db requiring 1/4th the amplifier power which is critical with room control that frequently has to correct troughs of up to 10 db and more. This is why we need so much power when room correction is used particularly with small sealed woofers that have to force response below 40 Hz. The only other ways to achieve flat response at the listening position are to move the listening position to a point in the room where the bass is satisfactory or move the subwoofers around in the room in a trial and error way to accomplish same. Good luck.