Wednesday, October 7, 2015

New Folded Bass Horn - Back Chamber From Recycled Technics SB 2745 Speaker

I have been putting off building a back chamber for the new folded bass horn.  I was recycling a pair of Technics SB 2745 speakers, removing the drivers and other hardware, when I realized that the dimensions of the particle board cabinet might be ideal for a back chamber for the new folded bass horn.  All I had to do is cut about 11 1/4 inches from the length dimension on the table saw.  Then I cut out a rectangle of 1/2 inch plywood to fit into the open end.  Here is the "Technics" back chamber installed over the eight inch driver on the new folded bass horn:

There is already a round cutout for a twelve-inch driver in the Technics box.  The box will work for any diameter bass driver up to 15 inches.  In the picture above, the modified Technics back chamber is resting on a couple of two inch maple blocks to raise it to a height centering it on the horn throat and driver.

One observation regarding the back chamber is that, apparently as a result of the high efficiency of this folded bass horn, very low power levels and cone excursions produce very loud sound levels in the room.  As a result of this high efficiency, there are extremely low back pressures in the back chamber at normal listening levels.

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