Big BenD Bass Horn: Belts and Braces - Appendix
This appendix will show measurement of the unbraced wall and final performance of the braced wall with everything in place. It will contain one figure for each measurement point, with a few exceptions, divided into sections for each part.
The bracing was applied at the end, after all other bracing, as the measurement at the back of the rear chamber was used as a level reference to keep all measurements comparable.
Not much was done here, so I suspect the reason for the difference in vibration comes from the way the horn parts were supported during the first measurements, compared to when the horn is upright.
The main objective here was to push the modes above the passband, and it does seem to have been fairly successful.
Mouth Bend (Inner)
Mouth Bend (Outer)
Mouth Bend (Side)
The measurements do not show much improvement over the "unbraced" condition. That is most likely because the bottom panel was braced from the start; the braces were used as a jig for the curved panel. But a few additional braces were added (RA), although they don't seem to have improved things. This may be due to the ground not being completely flat when these measurements were made. The WH measurements were made inside the garage, with the horn firmly placed on a flat concrete floor. It also seems that some vibrations were transferred from other panels, possibly through the cross brace, as some additional modes appear in the WH case, compared to R (unbraced mouth).
Here the lower bell mode(s) have been considerably reduced, especially by the addition of the extra side brace that turned the mouth side edges into 'C' beams.
Positions 61 and 63 are the right and left sides of the horizontal brace, 62 is the top part of the vertical brace, and 64 is the bottom part.