How to get TSP for two drivers back to back in anti-phase (dipol)?

[schro20]

I am trying to model an open baffle driver where the driver for the model is actually physically a pair of drivers back to back run in anti-phase. For an example of the arrangement I am thinking of:

The pair of drivers then appears as a single driver (at least to a first approximation). What are the new T/S parameters for this driver given the old ones? Membrane area for example does not change. But one effectively gets double the coil and magnet.

So, what I am looking for is the set of T/S parameters I should use in an open baffle simulation for a driver which is actually made of two drivers back to back in an enclosure and run out of phase. I have the T/S parameters for the single driver.

Thanks

peter

 

[Don Hills]

It's basically an isobaric configuration.

Vas is halved, because Cms (mechanical compliance, or how easy it is to move the diaphragm) is halved. (Two suspensions to push, so twice as stiff.) All of the other parameters balance out - for example, the Cms halves but the moving mass doubles, so the resonant frequency does not change.

You do have to consider the effects of the voice coils, whether they are wired in series or parallel. If you change the voice coil resistances when you double the drivers, then that cancels out too. A single 8 ohm speaker equals 2x 4 ohm isobaric in series, or 2x 16 ohm isobaric in parallel.

But working from the parameters of a single driver, the following rules apply:

2 drivers mounted isobaric, wired in parallel:
Re = Re / 2
Le = Le / 2
Vas = Vas / 2

2 drivers mounted isobaric, wired in series:
Re = Re * 2
Le = Le * 2
Bl = Bl * 2
Vas = Vas / 2