Posted by Steve Inman on October 26, 2001 at 10:38:02:
In Reply to: subwoofers and upright vs bell front posted by Philip Jensen on October 26, 2001 at 09:48:34:
Interesting post. I think there are multiple things going on here. When the subwoofer is aimed up, the carpet in the typical room won't swallow up as much of the sound. This phenomenon is why speaker stands became popular a while back -- move the woofer up in the air and away from the carpet. So the issue of up vs. out may deal with how much of the sound makes it to your ear, and how much is absorbed by your carpet. Aiming the subwoofer up in the corner will help improve things here.
Next is omni vs. uni-directional sound. Low frequencies are omni-directional -- they leave the sound source and tend to go in all directions. High frequencies are much more directional -- they go where you aim them. So if you put your subwoofer in the corner, you are reflecting some of the sound that would normally go back behind the speaker OUTWARD to the listener, as it reflects off the walls in the corner. This also enhances the result.
The tuba analogy is hard to figure out, because with a stereo system, you have just separated the different frequencies into different speakers. The subwoofer ONLY has low frequencies. With a tuba, you've got all frequencies coming out of the same "speaker". So when you aim the bell up vs. out, you can't optimize things, because all frequencies go the same direction. Bell up, would conceal the high frequencies from the audience (uni-directional sound), resulting in a more mellow sound, and also be quieter because the "speaker" is aiming away from the audience. Bell forward will increase both the volume of the fundamental the audience hears as well as the high frequency content that they hear. Although in all cases, not all of the lower frequency sound reaches the audience because this is omni-directional. But more of it will if you use a bell front tuba / sousaphone.
I think your suggestions regarding the sounds heard by the audience are accurate. Also, I agree we should try to increase the humor content of playing trumpets and trombones by asking these folks to lie on their backs while they play (especially funny images come from trombone players trying this -- maybe we could tie little flags or pompons on their slides . . . .)!!
Steve Inman
amateur tubist, amateur acoustics guy
Kokomo, IN