In all seriousness as has been pointed out this has turned into a bigger project than originally envisaged, there are so many options to explore and several that I quite like.
Perhaps what I could do is offer some options and ideas based on my favs, probably by next April

While we are doing the equations and all that, I have been refreshed on the subject of loudspeaker dynamic range and the variation of distortion with level .

The new Wilson Audio MAXX III , in review , is providing some further teaching on the subjective benefit of large radiation areas and low distortion , provided of course that the device works satisfactorily as a whole.

Premature compression and distortion in smaller speakers is a way of life, and those that legitimately use them are so adapted and forgiving.

My reference speaker is not so small , has an 11 inch nominal bass unit and runs 87dbW, but you can get it to limit and indeed its purest sounding cruising level is perhaps 5dB below the maximum possible.

Nevertheless going to the 150 litre bass bin , 11 inch and 13 inch bass units in parallel and the power shared twin mid units, at 91 dB sensitivity, of the MAXX III is a refreshing experience, seemingly unlimited maximum level, and very little change in innate timbre with level, only what goes on in your ears. It readily delivers those high levels where the ear shows a shift in perceived pitch, yet remains subjectively unforced. Measurement shows very low distortion over the frequency range.

Its great when you can get it , and may help to inform those thinking of building a speaker. Do not neglect issues of sensitivity, power handling , distortion , they may count more for realism and listening satisfaction than the result of a slavish attention to a nominally smooth frequency responses.

Martin C

This has always been my approach to speaker design. The largest sub I have built so far was ~ 250 Litres, used a 21" bass unit and 16Hz was a doddle

In the course of my reading, I came across an excellent paper in two parts by U. Horbach and D.B. Keele (aren't all Keele papers excellent?), which can be downloaded from Keele's own website in PDF format:
http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(2007-09%20AES%20Preprint)-%20Linear%20Phase%20Digital%20Crossover%20Flters%20Part%201.pdf
http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(2007-09%20AES%20Preprint)-%20Linear%20Phase%20Digital%20Crossover%20Flters%20Part%202.pdf

I'm not going to go into the particulars of the digital crossovering they propose, but focus on one aspect of the paper, which is particularly enlightening.
They are investigating the concept of a columnar speaker with very tightly controlled vertical directivity, what they call "constant beamwidth".
In essence they are taking the basic "D'Appolito" configuration (one tweeter between two mids, or MTM) to its extreme by adding woofers and subs on each end (say an "SWMTMWS" scheme).

They base their discussion on this invaluable table:

which portrays various patterns of directivity exhibited by two idealized point sources separated in space by varying fractions of their working wavelength.

By splitting up the audio band into smallish segments (each allocated to a suitable driver pair) and calculating the required distance for each driver pair, they aim to produce a speaker that emits a finite cylindrical wavefront approximately as tall as the speaker itself, and minimize boundary interactions with the floor and ceiling:

I recall seeing several speakers with similar layout of late, although I don't know to what extent they are actually based on Horbach and Keele's work.

This layout also reminds me somewhat of the concept behind Quad's concentric stators, except squished from sideways.

Yes particularly the bigger models that Duntech made the Soveriegn 2001 and the later Dunlavy designs fromthe same designer, particularly the Reference VI which used 2x15" 2x8" 2x5" 2x 1 1/4" and a 3/4" tweeters.

Here are some more loudspeakers using the TAD drivers but with a very conventional looking cabinet..........

http://www.swissaes.org/nl/aes_newsletter_80.pdf

Been asked about wide dispersion pattern tweeters, is there a soft dome equivalent of this unit?

http://www.seas.no/index...7tbcdgb-dxt&catid=45

http://www.seas.no/image...dfdatasheet/dxt_seas.pdf

Hi,

The Volt and ATC units are very expensive. Any reason for using these? They are sealed units, whereas others are generally open.

Regards,

Shadders.