The Ribbon / Dipole Cones Speaker Project

Rob passed away in the summer of 2009, so this project will, sadly, not be completed. Both the Wisdom/B-G drivers and the Lambda woofers are for sale. Reach me through my contact page.

Ribbon Drivers:

Bohlender-Grabener RD-75


 The midrange/tweeters are a special Wisdom Audio version of the stock Bohlender-Grabener RD-75 planar magnetic drivers (150hz-18kHz, though most DIY builders find they sound better if only run down into the 300z-600z range).

See more on these drivers   PDF B-G Ribbons Info file


A stock Bohlender-Grabener RD-75 driver, available from Parts Express, girl not included...  ==>


The web's most extensive discussion of all things dipole is from Siegfried Linkwitz, retired HP engineer and co-inventor of the nearly ubiquitous Linkwitz-Reilly 4th order crossovers.

Dipole Woofers:

Lambda Motor diagram


Four  Lambda Acoustic 15" woofers (per side) designed for dipole use (flat to 2kHz, Qts of 0.94).

Still need to build custom steel tube frames and MDF baffle boards.


Why are the Lambda Acoustics drivers are so special ? Visit the extraordinarily comprehensive Loudspeaker Driver Selection Guide (LDSG)


Drawing of the Lambda loudspeaker motor  ==>


The active digital crossover/EQ/time delay unit is a BSS MiniDrive FDS336

More info on this extraordinarily flexible "speaker management device".

BSS MiniDrive FDS336

Other products, which do essentially the same thing, are available from dBx, Rane, Bohringer, XTA and Ashley, amongst others.


Other Audio Projects:

DIY Dipole speaker project


A similar project from Cicago's Kurt Chang. This uses a stock RD-75 driver with four 18" JBL woofers.  ==>


Photo gallery of other speakers, both commercial and DIY, using the Bohlender-Grabener drivers.



Rob Gold's 'Red Wing' Teres Turntable

Email Rob