effect on box volume of series vs parallel connection of speakers?

[wintermute]

Hi,

I have been playing around with a prototype design for my Morel MTM project.... some details here http://www.diyaudio.com/forums/showthread.php?postid=563594#post563594

each mid bass is in it's own sealed enclosure (box is partitioned).... what I had done was to model a single driver (average t/s params of all four drivers) in unibox, and then made two cavities of the size I came up with (plus a bit)

I had been testing with the drivers in parallel, but wondered about connecting them in series.

I decided for whatever reason to use unibox to model two drivers in parallel and found that it gave a volume bigger than double that for one driver... then I tried in series and it gave me a volume slightly less than double that of a single driver.

unibox standard design comes up with the following:

1 midbass 6L
2 midbass series 10.7L
2 midbass parallel 15L

now to confuse me even more a guy yesterday on the ESP forum told me that it should be the series configuration that needs a bigger box volume.

so I guess to get to the point....

a. is unibox giving correct info when using the parallel/serial feature?
b. if a is correct, then should i be making bigger boxes for my parallel configuration, even though I have the drivers in separate enclosures??

winisd pro and speaker workshop both simply double the volume for one driver....

Tony.

 

[MJK]

Hi Tony,

For two drivers in a single box, the box volume needs to be double the volume for a single driver. The series or parallel connections does not impact box volume only SPL output. I have a short write-up for modeling two drivers in a single box on my site :

http://www.quarter-wave.com/General/Two_Drivers.pdf

The three examples demonstrate the system response for one and two drivers.

Hope that helps,

 

[wintermute]

Thanks Martin

nice to get a very authoritative answer I can rest easy now that I haven't botched it up!

I downloaded the lite version of mathcad to play with your worksheets, but only for the TL stuff..... maybe I should have a look at the other ones too.

I'm interested though as to why unibox is giving different volumes for series and parallel connections... I guess I'd have to ask the author that question!

I think I just found out what was causing it!! I had a series resistance of .5 Ohms in the model, if I remove it both series and parallel connections come up with the same volume.... I think I had put it in as a guess as to what the series resistance of my crossover would be.

edit : my stupid mistake I had it in the field for Series resistance due to amplifier output impedance and speaker cabling..... not .5 Ohms!!! putting it into the correct field means no change for series/parallel

Tony.

edit: well I have botched my prototype a bit, since the volume is about a litre more than it should be but..... at least that is curable and it is only a prototype