TD15M woofer with Geddes 12" waveguide

[drchait]

I have to choose between the acoustic Elegance TD12M

AE Speakers --- Superb Quality, Unforgettable Performance, Definitely.

and the TD15M.

AE Speakers --- Superb Quality, Unforgettable Performance, Definitely.

For a dipole speaker I am designing. The woofer needs only go down to 300Hz. I would rather use the TD15M if I can get it to work. It has 3db more headroom a curve linear cone and from the forums I have read it has "superior midrange sound".
I am looking at using the TD12M or the TD15M with a 12 inch diameter Autotech OSWG Geddes type waveguide crossed over about 1300Hz.

DIY Sound Group

The Geddes wave guide must be crossed over above 1200 Hz according to the literature. In the Geddes literature you are supposed to use the same size waveguide as the woofer dimensions to obtain a constant directivity system. I have read that the TD15M has wider dispersion from 1000Hz to 2000Hz than normal 15 inch woofers because of its phase plug, and has good off axis response up to 2K. Can I get the constant directivity that I am after with the TD15M and a 12 inch wave guide, or will I have to use the TD12M. I am also concerned that the driver to driver distance will be larger than 1 wavelength at crossover with the 15 inch driver. I know the emerald physics dipoles used a 12" waveguide with a 15" woofer and it was a pretty succesful design. Anyone who is familiar with AE speakers or can just give an opinion is extremely appreciated.

Thanks

John

 

[dabbler]

What is your main design goal here? If it is achieving constant directivity then you are on the right track. But if you are going for the best sound quality then you need to re-think it, in my opinion.

I'll be controversial and say that the TD12M will not sound great playing up that high, nor will any other 12 inch woofer. This is from my listening experience only, others will have a different opinion. I would personally look into a high efficiency 8inch mid that should easily get down to 300hz and play more cleanly up to the crossover point.

If on the other hand you are mainly looking for a home theatre speaker then a large woofer as mid should be fine. I havent heard the TD15M but apparently it beats the 12 for midrange performance. You could also look into the Altec woofers made by Great Plains Audio. A lower cross over point can be had by using the 15" SEOS waveguide being developed by some of the guys at the AVS forum:

Hey guys...we need a little rallying here... - Page 31 - AVS Forum

 

[ScottG]

I can see Earl cringing on this one..

 

[Sveinung]

I am using a TD12X up to about 1400hz in a two way, it works really good. The sound quality of these drivers are amazing, also in the midrange. I think the TD15M is the best driver for the task.