Enclosure design for dipole speaker

[clengman]

I've been reading up a lot lately about class D amps and thinking about building a small boombox. I'd like to try a magnet-to-magnet dipole design. I've been looking at the "HIFI speaker design tools" linked from the Madisound website and I'm starting to get a grasp on optimizing an enclosure. I'm going to play around some with winISD when I get home. (I'm on a mac at work so the mh-audio tools are the best I've been able to find, but still don't allow for as much customization as I think winISD does.) I think it'll help me out to see some frequency response plots using different drivers and enclosures of different sizes.

One thing I'm not getting is how to plan for the magnet-to-magnet dipole setup. Will I be in the right ballpark if I optimize for a single driver in its own box then just double everything? Or are there other things to consider? Can winISD model a system like this with two opposing drivers in a single enclosure?

 

[GM]

Mag-mag coupling [assuming no rear VC cooling vent] changes Qts a minor amount, though not enough to bother with, so designing for one and doubling Vb, vent design [if used] is fine or if you prefer a single large vent, then design using two drivers.

No, these simple programs can't accurately sim bi/di-poles, TLs, horns, OB, etc., but to design a sealed, vented cab only requires Fs, Vas, Qts.

GM

 

[clengman]

Thanks! Just what I needed. Before you mentioned it, I didn't even see that there was an option to add multiple drivers to the box.

I think I've got a plan now. I appreciate the help.

 

[Roo2]

Hi there, I'm looking to do the same thing with some old but unused Vifa drivers I purchased about 15 years ago… They all appear OK. I have four Vifa P13WG-00 8 ohm 5" woofers and two Vifa D25AG-35 tweeters. The woofer parameters I can find online are:
* Power handling: 40 watts RMS/55 watts max
* Voice coil diameter: 1"
* Voice coil inductance: .70 mH
* Nominal impedance: 8 ohms
* DC resistance: 5.5 ohms
* Frequency response: 60-5,000 Hz
* Magnet weight: 8.5 oz.
* Fs: 60 Hz
* SPL: 86 dB 1W/1m
* Vas: .35 cu. ft.
* Qms: 1.70
* Qes: .68
* Qts: .48
* Xmax: 3.0mm
I've sent an enquiry off to Tymphany (who bought Vifa) asking for a data sheet to confirm.
I'm keen on perhaps buying another two "similar" tweeters and building a portable speaker similar to but smaller than Saturnus' Boominator dipole design. I've just downloaded the Unibox spreadsheet.
I would really appreciate some advice to get me going (I'm definitely a newbie but have an engineering background so will probably get the basics).
1. Are these drivers suitable to consider for this kind of dipole speaker design?
2. I get the impression that I should be doing a vented enclosure for these drivers?
3. What would be a good box resonant frequency Fb to aim for?
Thanks!
Andrew,
Brisbane,
Australia.