Posted by Wayne Parham [ 66.137.59.19 ] on April 12, 2004 at 04:39:44:
In Reply to: Re: Implementation posted by Adrian Mack on April 12, 2004 at 04:08:16:
All graphs were done outdoors, and they all varied a little bit from sample to sample. I always take at least three measurements and look for consistency. But I've also always considered tests like this to be a bit ambiguous because it is really sort of a budget test. Please don't consider these datasets to be anything but tools to help explore the design.
The rear-facing midrange used in the 1980's seven π loudspeakers were JBL 2105's, which were also used as front-facing midrange drivers. They were a 5" cone midrange, and there were sets for the front and rear installed in that model. Two-way versions develop all midrange from the driver in back, so the addition of a forward-facing midhorn will cause the speaker to have front and rear midrange output unless the driver in back is crossed over lower.
A 1/4" or 3/8" mounting spacer ring is an excellent idea. The additional front chamber volume won't hurt and it will ensure that the cone can't strike the mounting plate. For those that have routers, it might be just as good to route out that much area around the driver on the plate, maybe even just at the edge and back towards the center for an inch or so. The only part that might strike at high excursions is the surround and maybe the edge of the cone.
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