aer md 3B and hedlund (Drive Units)

by unknown, Wednesday, February 21, 2007, 13:50 (6245 days ago) @ zsolt

Hi Zsolt

I ran Hornet Hedlunds with EAR Mk1s for a while, so the following may help.

Very early Hornet Hedlunds had a deeply recessed cut out in the front panel for the driver, and this restricted clearance with the rear sloping panel at the back of the compression chamber as Bert described.

Later Hedlunds like mine set the drivers in by only about 8mm which was plenty to install the EAR Mk1s and also my later Lowther DX4s without problem.

If you are building from new and have deep (large) drivers then you could fit the drivers flush on the front panel or even construct it slightly forward to give the drivers the clearance they need. All this will of course give more volume to the compression chambers.

In my case the EAR Mk1s needed more compression chamber volume than the standard horn. To achieve this I cut out three 2inch holes into the normally sealed chamber that sits below the compression chamber. This worked perfectly.
When I changed to DX4s I glued 3 cut out circles of wood back into the holes and the chamber was restored to normal.

Hope this helps.

Chris

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