Parallel drivers, how much BSC?

audiobomber · 15th May 2007, 02:17 PM

If you parallel two identical 8 ohm drivers, you get 6dB gain in SPL (+3dB due to mechanical efficiency, +3dB sensitivity increase due to 4-ohm electrical load). This effect is used to add BSC in an X.5-way speaker system.

What about if you parallel an 8-ohm and a 16-ohm speaker in a 1.5-way or 2.5-way system? How much BSC do you end up with? Your load becomes 5.3 ohms, so you don't get quite as much of an increase in electrical sensitivity, and you have double the cone area, but the 16-ohm driver is not being driven as hard, so the system loses some mechanical efficiency. So what's the net increase in SPL?

Some people say a full 6dB of BSC is too much. Wouldn't parallelling an 8-ohm and 16-ohm speaker in a .5-way system be ideal in some cases?

e.g. 1.5-way using CSS FR125S full-range and WR125ST for BSC.

Or a 2.5-way using tweeter, WR125S mid, WR125ST for BSC.

sreten · 15th May 2007, 02:30 PM

Hi,

Arrranging optimum excursion for both drivers is problematic.

It is possible to have less than 6dB baffle step with different drivers.
e.g. sealed bass/mid with a lower efficiency reflexed tuned bass driver,
aligned such that excursion limits are relatively co-incident, i.e the
bass only unit produces more low bass than the other.

Different impedance versions of the same driver .... I don't think so.

/sreten.

15th May 2007, 02:17 PM	#1
audiobomber diyAudio Member Join Date: Jul 2004 Location: Sudbury, Ontario Canada	Parallel drivers, how much BSC? If you parallel two identical 8 ohm drivers, you get 6dB gain in SPL (+3dB due to mechanical efficiency, +3dB sensitivity increase due to 4-ohm electrical load). This effect is used to add BSC in an X.5-way speaker system. What about if you parallel an 8-ohm and a 16-ohm speaker in a 1.5-way or 2.5-way system? How much BSC do you end up with? Your load becomes 5.3 ohms, so you don't get quite as much of an increase in electrical sensitivity, and you have double the cone area, but the 16-ohm driver is not being driven as hard, so the system loses some mechanical efficiency. So what's the net increase in SPL? Some people say a full 6dB of BSC is too much. Wouldn't parallelling an 8-ohm and 16-ohm speaker in a .5-way system be ideal in some cases? e.g. 1.5-way using CSS FR125S full-range and WR125ST for BSC. Or a 2.5-way using tweeter, WR125S mid, WR125ST for BSC. __________________ Dan

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15th May 2007, 02:30 PM	#2
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, Arrranging optimum excursion for both drivers is problematic. It is possible to have less than 6dB baffle step with different drivers. e.g. sealed bass/mid with a lower efficiency reflexed tuned bass driver, aligned such that excursion limits are relatively co-incident, i.e the bass only unit produces more low bass than the other. Different impedance versions of the same driver .... I don't think so. /sreten.

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