Distributed Bass Array Speaker Placement
I recently moved to a new house with a large basement room with the dimensions of 18’ x 28’ x 8.5’. Mains are Wilson-Benesch Vectors placed a good distance from the side and front walls. They are crossed over to a 4-speaker distributed bass array with a JL Audio CR-1. Low pass and high pass are both at 80Hz with a 4th order slope. There is no option for delaying either the mains or the subs. More details are available on my Audiogon system page.
My research (https://www.audioholics.com/subwoofer-setup/multiple-subwoofer-setup-calibration-1) indicates that a good arrangement is to place each subwoofer in a corner or at ¼ of the room width on the front and back walls. I am concerned that this placement could make the time delay between the mains and subwoofers output audible. My question is will placing the subs ¼ of the room length on the side walls provide most of if not the same outcome as placing them on the front and back walls or in the corners? This would be my preference since it will make the subs pretty close to equidistant from the main listening position. Or something entirely different?
I do not wish to employ DSP. Been there, done that with my Devialet 400 and my goal here is to go pure analog. It sounds pretty amazing now and is certainly superior to what I had before.
Went to Harman.com and looked at Mr. Welti's work. I tried putting all four subwoofers in the corners and found that it had a nasty resonance. Went to another suggested layout with subwoofers on the front and rear walls and moved in a quarter of the width of the room from the side walls. Sounds great, measures essentially flat to 20Hz. Thank you, Duke. |
Your speakers appear to be well engineered. Personally, I'd lose the CR-1 and run them full range and find a sub or DSP that can daisy chain and manage the crossover within the subs. I don't think there are any two DSP programs alike. You may be selling potential subwoofer DSP short. What subwoofers will you be using? |
Arrival times are not critical in the bass region, at least not within the range of delays arising from the subwoofers being different distances from the listening position. The ear’s time-domain resolution is poor at low frequencies. We cannot even detect the PRESENCE of bass energy from less than one wavelength, so arrival time differences that amount to small fractions of a wavelength at bass frequencies are inconsequential. From my "Swarm setup guidelines" e-mail that I send out to customers: 1. Todd Welti symmetrical: First the Welti Mancave... each sub has its own corner, and is placed 1/4 of a wall length out into the room relative to each of the two walls that meet in that corner. This usually puts the subs in competition with other items on the room for prime real estate, hence the "Mancave" designation. Now the Welti Practical... one sub up against each of the four walls, at the midpoint of each wall.
2. Earl Geddes asymmetrical: Place one sub in a corner (preferably a front corner), one sub somewhere along each of the two far walls (the walls "opposite" that corner), and the fourth sub somewhere else but not too close to any of the other three. Bonus points if you can elevate one of the subs, and extra bonus points if you can elevate it above the centerline of the room, to get some distribution in the vertical plane as well.
3. Golden Ratio: One sub goes in a front corner. The second sub goes .38 times the long wall length away from a corner. The third sub goes .24 times the long wall length away from a corner. The fourth sub goes .15 times the long wall length away from a corner. You want to end up with at least one sub somewhere along each of the two walls that are opposite that first corner (the one with the sub in it), and you want the subs to end up spread apart instead of clustered together. (For my fellow geeks, 1 - .62 = .38; .38 x .62 = .24; and .24 x .62 = .15)
4. The Crawl. Put one sub in the listening chair and then crawl around the room while playing music with good bass content. Where it sounds the smoothest, place one sub there (leave the first sub in your chair for now). Now playing the same music through both subs, adjust the volume as needed, and repeat the crawl. Do this until you have identified the four best-sounding locations.
6. Live and let live: Find four scattered locations where you can get away with placing a small subwoofer without your spouse initiating divorce proceedings. Put them there.
7. Don’t be afraid to get creative. One of my customers places a Swarm module behind his main listening chair, on an Auralex isolation pad, facing up at the ceiling.
Once your subs are positioned, I suggest first adjusting the Gain, then the crossover Frequency, then the Phase of the subs. The Gain control makes the most audible difference, next is Frequency, and finally Phase. You might want to cycle through these steps several time to fine-tune the settings. May the audio gods smile upon you for your financial sacrifice of buying four subwoofers! Duke |
I’d ask @audiokinesis in on this as he’s pretty much the authority on a DBA array. |
I have Romeyn's DBA and appreciate what you suggest. To rephrase my question, how important is time delay in the placement of a subwoofer system? Many suggest it's very important and many of these same folks use DSP to accomplish it. I cannot do that. I appreciate your pragmatic approach to the matter. I am still curious as to the answer to my question.
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I have a DBA from James Romeyn, which is based on the Audiokinesis Swarm system. Basically, you can do it (it’s a free country) but it will not be optimized. Since you have the four subs I highly recommend you find a way to do it right. You will be very happy you put the time and effort into it. If you Google either James Romeyn or Audiokinesis then you’ll find a manual way to do this. It’s a detailed step-by-step process. The other way is to use software to analyze the acoustics of your room and then guide the optimal placement of the subs. A final option is to work with someone like J. R. Bosclair (Wallytools) either in-person or remotely. He is awesome to work with. (I recommend giving him a call.) Don’t just place them where you *think* they should go. Take the next step. It will totally be worth it. Good luck.
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