Posted by martin seddon [ 203.24.100.133 ] on August 27, 2004 at 08:30:37:
Hi,
I recently built what I call a push-pull horn and would like to chip in with my own experiences.
It started out with a large fibre glass 160Hz front horn for a Lowther PM2a. Then I made an L shaped 2.2m 7000cm2 f/glass and ply horn for bass using a CA25FEY.
I had cross over difficulties I didnt know how to solve and eventually adapted the horn to back load the Lowther. This was done by breaking the top round fibreglass section over to mate with the mounting plate on the fronthorn. So there are only 2 x 90 degree bends (using reflector plates. The driver sits in the throat of the backhorn - with no throat chamber.
HornResponse predicted it would work down to 50Hz at c. 102 dB - and I think it may actually be true in practice - tho I havnt measured. It works much better than I expected - great bass integration. A <40Hz sub-woofer blends in well to get the rest.
I think there are some conclusions to be drawn contrary to normal belief:
Extended HF down the back horn is OK. The back horn throat chamber (LP acoustic filter)is best eliminated - this removes the nasty looking peaks (phase inversions?) shown by HornResponse - which even if well down, must surely be heard full level from the front.
Front horns definitely sound good on Lowthers - but it seems a shame to disdard the superb upper bass these drivers are made for (horn loaded). Push-pull is the way to go. IMHO.
best rgds to all,
martin seddon
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