MULTIPLE.HTM --- Part of Manual for Driver Parameter Calculator --- by
Claus Futtrup.
Created 8. March 2003, last revised 8. March 2003.
Ported to XHTML 1.0 on 2. October 2004. Last modified 25. October 2004.
When using multiple drivers of the same type, connected in series or parallel, the question often arise which paramter equivalents can be used for simulations.
Generally speaking drivers can be connected electrically in series or in parallel, but they can also be connected acoustically in series (one after the other as in an isobaric / compound cabinet) or parallel (ie. side-by-side in the box). If both sides are not specified, then confusion often appear.
Here is a schematic diagram, which shows what happens to loudspeaker parameters (an equivalent for multiple drivers) with multiplication factors:
+-------------------------------------------------------------------+ | | 1 driver | 2 units | 2 units | 2 units | 2 units | +-------------------------------------------------------------------+ | electrical | | series | parallel | series | parallel | | acoustical | | parallel | parallel | series | series | +-------------------------------------------------------------------+ | fres Hz | 1 | 1 | 1 | 1 | 1 | | Re ohm | 1 | 2 | 0,5 | 2 | 0,5 | | Sd cm2 | 1 | 2 | 2 | 1 | 1 | | Mms gram | 1 | 2 | 2 | 2 | 2 | | Cms mm/N | 1 | 0,5 | 0,5 | 0,5 | 0,5 | | Vas liter | 1 | 2 | 2 | 0,5 | 0,5 | | Rms N*s/m | 1 | 2 | 2 | 2 | 2 | | Bxl Tm | 1 | 2 | 1 | 2 | 1 | | Le mH | 1 | 2 | 0,5 | 2 | 0,5 | | Qm - | 1 | 1 | 1 | 1 | 1 | | Qe - | 1 | 1 | 1 | 1 | 1 | | Qt - | 1 | 1 | 1 | 1 | 1 | | SPL dB/V | 1 | 0 | +6 | -6 | 0 | | SPL dB/W | 1 | +3 | +3 | -3 | -3 | +-------------------------------------------------------------------+
This table can be expanded to include all the dependent parameters in DPC, if desired.
The units indicated in the leftmost column are obviously not a requirement. Any sets of units will work this way.
If you want to connect 4 drivers then all you have to do is multiply the situations above. Say, for example, that you want to connect 4 drivers in a "dual" isobaric design. The two drivers behind each other are connected in electrically and acoustically series, the two sets of drivers are then connected in electrically and acoustically parallel. Find the two colums and multiply the values (except the SPL value where the +6 and -6 dB must be added, so that this configuration has no change in sensitivity).