Another low frequency, very high quality sound reinforcement option, particularly for European DIYers, has always been Tannoy. Tannoy doesn't list their raw drivers on the website (www.tannoy.com), but does list the part numbers of drivers used in their sound reinforcement products. All of these drivers are available from a licensed Tannoy professional dealer or directly from Tannoy. Check the B475 or B950 Tannoy subwoofers, and compare against a JBL SR4718 and SR4719 for a quick guesstimate on tuning for the drivers in a comparably sized enclosure. The driver tuning seems to be a fair bit lower (maybe as much as 9-10 Hz), at the expense of some power handling. I don't know how the two would compare at the lower midrange and higher, but we are talking about low frequency augmentation speaker. Also, from the price of finished Tannoy subs, ~1100 US$, I suspect the prices may be more competitive than TAD. Just another option to consider.

Disclaimer: I have not yet heard the Tannoy B475 or B950 subwoofers, but have heard the T12, I12, D900, D700, D500, Saturn 10, and Saturn 8. They are all killer. I purchased the T12 used for sound reinforcement work. So yes, I am blissfully biased.

Cheers Wayne!

P.S. Thank you for all the information you continue to provide for free. I am looking forward to seeing your final copy of the crossover paper. Someday, when I can afford to build up my shop tool set, I am going to be another speaker cutting fool.

John