History on ohm A's and F's.

Dale Harder recones original Ohm speakers and builds his own, improved versions of both A and F models. He can be reached at:

dale@hhr-lasers.com or 440-888-2163 in Parma, Ohio

The operating principle of the DDD driver, as used in the German Physiks HRS 120 (10-inch acoustic suspension woofer below 240Hz):

"The lower frequency end of its operating range can be described with Thiele/Small resonant parameters, while in the next frequency band up to the coincidence frequency 'it works like a pistonic driver'. Next, there’s an overlapping band where pistonic movement is 'progressively replaced by bending waves until all the radiation is generated purely by bending movement in the cone'."

Hi-Fi World review here.