Subwoofer setting

Before auditioning different lo-freq cut-off points (I recommend the 50Hz also) you should find a reasonably intelligent location for the sub. . . . . .
Assuming you have only one sub (best IMO, as long as you can keep the x-over point below 100Hz) AND assuming the sub has no phase adjustment, the best method is to place the sub at your listening position, and then listen to program material from different locations in the room to find the best "final resting place" for the sub ;-) Try listening from these positions:

>Each corner of the room
>Smack between the main speakers
>Different positions along the four walls, but particularly the one behind the speakers.
>Right behind the listening position

One of them should provide the strongest and most seamless response in your room. Place the sub there.
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Nsgarch - regarding your suggestion, I've seen this recommended before in print but they never say whether to place the sub on the floor at your listening position or up at ear level. By the same token, do you crawl around the room down low while listening for the best bass or walk around upright? Advise? -jz

JZ -- Good question. Low bass disperses in all directions pretty quickly, so as long as the room is bigger than say 200 sq. ft., you can just set the sub on the floor at your LP, and you can stand normally when listening at different locations. When you are listening at a position near a wall (or in a corner) stay about 2 feet from the wall or corner to avoid the natural bass reinforcement that occurs when the wave hits the wall and reverses direction.

Again, I don't guarantee this method if your sub will be producing frequencies much over 80 - 100 Hz, but it's still worth a try.

Something many people don't realize is that for a 20Hz wave to form in the air, the largest dimension of the room must be at least 27.5 feet. This can be measured from a ceiling corner to the diagonally opposite floor corner. It's derived by dividing the speed of sound in the air (approx. 1100 ft/sec) by the freq. (20) which yields the full wavelength in the air for a 20Hz note (55 feet) and then you divide that by 2 (since a half-wave will do ;-) which gives you 27.5 feet. All dimensions increase a bit as you go higher than sea level ;-)) The moral of this story is: Even if your sub is making very low frequencies, your room might be too small to allow them to happen ;-)

"...for a 20Hz wave to form in the air, the largest dimension of the room must be at least 27.5 feet."
I've seen this argument before and also seen it refuted.
How do you explain the stomach-churning bass able to be produced in some car installations?