Loudspeaker Designs and Articles for the DIY Enthusiast
|A high sensitivity / high SPL
design offered for PA, Music
and Home Theater
Again considering portability issues of a mobile system, the test enclosures were built of void free ¾” birch plywood. Each pair of series woofers exist in their
own sealed chamber with additional bracing to push the cabinet resonance higher in frequency. Even with the bracing, these enclosures are quite lively at
high SPL’s, and I suspect additional resolution and slightly better imaging could be provided by MDF construction, with its attendant weight penalty. A
separate recess for the crossover is built into the upper back of the cabinet makes for ease of access and installation. While the tweeter probably could get
by without being flush mounted, the woofers close proximity to the tweeter mandated their flush mounting, so all drivers were flush mounted.
I've also shown a version of the design for PA or center channel use. This merely flips the top and middle 2 sub enclosures around to put the tweeter in the
middle. I did not build this version, but I can see no reason it would require any crossover changes to implement.
Tips and Tricks:
The woofers come with 8 holes for a reason. Use them. 4 screws will not cut it, as I found out during harmonic distortion measurements. The front baffle
thickness shown is 3/4". Optionally, I'd suggest adding another 1/2" or more to the thickness, as we are dealing with a lot of inertia here. Tightly affix all the
components and wiring or make sure they won't vibrate against any internal surface. These speakers will rattle the windows when cranked, and anything
else not tied down, as I found out. You high SPL junkies may find speaker spikes to be a good choice on carpet to keep them from 'walking'.
Because of the designed high Qts, the speakers are heavily stuffed. The enclosure as drawn is divided up into 3 sub enclosures. Start out with 1 lb. of
stuffing in each. It's OK to drill holes between the sub enclosures to run the wiring, as they all will see the same pressure. The top enclosure may look
smaller, but it is the same volume. If you don't want to fuss with the windowpane braces, it is perfectly all right to make them solid, so each woofer gets its
The aperiodic 'vents' are not rocket science, nor is 3/8" necessarily the best size for your application. If you make six sub enclosures instead of 3, try using
a 5/16" hole in each one to start. I made no attempt to 'make a hole' in the stuffing for the vent. More stuffing may require a larger vent, so don't be afraid to
experiment with both.