Originally Posted by Flt Simulation
This may be kind of a silly question, but do you think a 2-channel home audio system really benefits much by also having a powered subwoofer?
Yes except perhaps with with a couple of long-throw 10" (or larger) drivers per side with dipole or cardioid bass which give you four bass sources with varying position (from the radiation pattern, not the pair of drivers which just get you enough headroom) that are more likely to interact positively with your room than two with conventional speakers or perhaps one sub-woofer.
I realize that a sub is needed in a home theator system to bring out all the explosions and various sound effects in these HD movies, but how about a sub with a 2-channel music only system? .... no movies, no tv
You have two big problems
1. The placement most conducive to good timbre, driver integration, and imaging is probably not the best place for modal interactions.
10X the bass energy at 70Hz due to your height mode is _not_ natural sounding.
Another of the bass issues is the SBIR null. You'll get a null around where the front wall to driver spacing is 1/4 wave length which is 70Hz for 4' of separation. Crossing to the sub-woofer (spaced closer) at a higher frequency avoids this issue. Unfortunately this isn't enough to compensate for a height mode problem.
2. Many (if not most) consumer speakers lack the linear excursion to reproduce acoustic music at subjectively realistic (but substantially lower when measured - perhaps 1/10th the power which I say having told friends that trumpets are _not_ appropriate for indoor Christmas carols) levels without unacceptable distortion.
Maximum excursion limited SPL from a monopole operating into free space at 1 meter is
102.4 + 40 log(f) + 20log(displacement) with displacement in m^3 and f frequency in Hz
102.4 + 40 log(f) 20log(travel) + 20 log(area) with travel in meters an area in meters^2 if you prefer.
Output at the maximum linear excursion into full space for various representative drivers at three feet is as follows at 120, 80, 40, and 20Hz. Many drivers have less excursion and lower output. Subtract 3-5dB for living room dimensions and more for a larger space for the SPL at your listening position.
You can add 6dB for a floor mounted woofer (as in many 3-ways), 6dB if there are a pair of bass drivers, and 6dB at the cross-over point to a sub-woofer.
Size Driver Sd (cm^2) x xmax (mm) 120Hz 80Hz 40Hz 20Hz
4 1/2" Seas W12CY001 50 x 3 89dB 82dB 70dB 58dB
5 1/4" Peerless 830873 88 x 3.5 95dB 88dB 76dB 64dB
6 1/4" Seas L16RN-SL 104 x 6 101dB 94dB 82dB 70dB
7" Seas W18EX001 126 x 5 102dB 95dB 83dB 71dB
8.5" Seas W22EX001 220 x 5 106dB 99dB 87dB 75dB
10" Peerless 830452 352 x 12.5 118dB 111dB 99dB 87dB
12" Peerless 830500 483 x 12.5 121dB 114dB 102dB 90dB
Where jazz sounds good at 85dBC average and good recordings have 20dB of dynamic range you're hitting 105-107dB a meter from each speaker. Feeding _Take Five_ through 60Hz second order Butterworth IIR filters I noted right channel low frequency peaks 10dB down from that; although that's still 30X what you can squeeze out of a 6" driver at 40Hz.
Sub ... good idea ... waste of money?
Fine idea, although it can't have a non-flat response which sounds impressive in the show-room, port noise which draws attention to it, a shallow cross-over or level mismatch with the same problem, etc.
More than one is a better idea where there are intelligent options for placement and integration.Edited by Drew Eckhardt - 11/16/12 at 12:48pm