Plans for: Acoustic 370 dual-folded-horn Bass, Woofer or Sub Cabinet. Extension cabinet made for Acoustic 360 & 370. Acoustic 360 had power amp mounted in a different cabinet while Acoustic 370 was fully piggy back and thus this cabinet it's main or extension cabinet. Cabinet had 18" Gauss 4882 Speaker. This cabinet was probably Acoustic's standard dual-folded-horn cabinet for various 15" & 18" Speakers. |
Graphic Views of Dual Folded Horns: |
The graphic image on the right is colored to show the 2 folded horn routes (green and orange) that are fed by the same speaker. The speaker / driver baffle faces rearword into the cabinet, feeding the 2 folded horns. The baffle enclosure is not vented and thus not tuned. The 2 folded horn routes are identical mirror images of each other, and are not isolated at the speaker source, and therefore maintain the same acoustic pressure and phasing in each horn. The folded horns are of course tuned. Thus the acoustic output exits the horns rejoined in phase and waveform. The dark blue area is dead air and purely incidental to it's closed panels in the folded horn structure. The 1/2" setback of the driver baffle from the cabinet face is to accomodate a grill or cap on the front of the cabinet if desired (keeps varmits out of the cabinet). The cabinet works sitting in both a vertical and horizontal position. The resonant frequency of the Gauss 4882 speaker original to this cabinet is 30 Hz and thus works as a woofer or sub-woofer, although the Gauss 18" speaker model 4883 is specifically designed as a sub woofer with a resonance of 20 Hz. |
The cabinet plans provided below are taken directly from 2 identical Acoustic 370 cabinets that I removed the speakers and hardware from and discarded the cabinets because I no longer play gigs as a profession / living and these monsters take up way too much of my space. The cabinet is quite simple in structure, but acute attention must be paid to exacting measurement so that the tuned dual folded horns will remain tuned. I highly suggest using Concrete Form plywood ....or at least Exterior ACX Treated plywood for durability and longevity. Face the 'A" side of ACX to the outside of the cabinet for ease of aesthetics. The knot holes in ACX will face the inside and can be filled smoothe with epoxy liquid or epoxy putty, by applying either with the knotted side of the plywood facing up on a horizontal surface / bench / sawhorses. Fill the knot holes flush with the top and cap the epoxy with a piece of wax paper several inches larger than the knot hole. When the expoxy sets firm, lightly rub the wax paper down onto the epoxy; The wax paper will act as an easy release mold and the epoxy filler will be flush and smoothe as a baby's butt requiring no more sanding than is normal for painting plywood. I also highly recommed using experior "drywall" type screws (they make them for plywood) as well as a high quality wood glue such as Franklin's exterior white glue. 1" squared (lumber size) strips of wood can be glued and screwed as extra block "gussets" along the interior joints for added strength and durability (pilot hole the screw holes to prevent splitting the gusset strips). It will not effect the tuning of the cabinet any more than the rather wide range of margins of specs for any number of speakers the cabinets were built to accomodate. Using 1" 45 degree corner gusset molding instead of squared strips will also work as glued-in joint gussets and will effect the cabinet tuning even less, if a person desires added gusset strength to the joints as well as maintaining as close to the folded horn / cabinet specs as feasible. (Don't penetrate 45 degree molding with screws or the molding WILL split regardless of pilot holes being drilled). All measurements on the cabinet are symetrical left to right and top to bottom. |
The Acoustic cabinet is constructed of 3/4" shop grade plywood, except for the two 3/8" plywood trapezoidal side panels of the speaker baffle. See *1 in the plans. |
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