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.
5. Stonehenge: This one is a bit of a compromise because the spacing isn’t as great. It works well if we are restricted to one end of the room. Arrange the subs in a wide semi-circle, with the mains usually "inside" the semi-circle. You can use symmetry or asymmetry. I have a customer with Maggies who is using this sort of configuration, and his room is asymmetrical so what looks like symmetry really isn’t.
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
