February 14, 2016

30 Hz horn sub continues

Exposed edges of the formply are painted with Duratex and pilot holes are pre drilled. Chamfer bit to recess the heads:

This is the end panel near the mouth. Thickened on the far end. A little strip of MDF is also added where the internal divider meets the end. This ensures the divider will remain in the correct position.

 End panel attached to the sides. A little newspaper catches any glue ooze.

Next the other end panel is attached. Screws here clamp the panels together as the glue sets, however, clamping is used (not shown) and some care is needed to ensure the panels don't move. Tightening up the clamps and screwing both cause the panels to move. The trick is to adjust as you go, screwing the panels in with a clamp in place.

 The bottom panel comes next.

 Bottom panel now on:

Internal divider:

This is screwed in on the end near the mouth, and clamped on the other. The final side follows.

The braces are attached after all four sides. The taper allows them to slide in. If the angles are correct, this will work with ease. 

Notice how opposing sides are clamped? The panels can have a bow in them and this can create problems with the bracing. At this point, you have to ensure the width is correct so that when the last side goes on, these panels have not bulged out, especially when the bracing pieces have been done.

Completed box now standing:


Here you can see the raw unfiltered response and the response with DSP (crossover filters and 2 PEQ).

As expected we see ringing above the passband, common with all "small" low tuned bass horns. Subjectively it sounds quite tight and clean in the 30 - 80 Hz range with test tones. Yes - you can actually gain a basic appreciation quickly of the sound of a sub from test tones. 

This sub is 450 x 450 x 1800mm.

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