Bonding (a couple of pins set and strapped clamped) the 1/8th in ply (3ply BB) to the front curved edge worked out - and fairly easily. I initially thought I had done a solid job cutting and sanding- but I could feel a couple of small imperfections. Absent a CNC machine, I’m happy with this as a guide for the side pieces. (the dark line between the ⅛ in and the board is the pencil line)
I built a test 'box' for the coax to run some initial comps for different open back-ish configurations. I won't be doing a full open baffle as this unit will sit on top of the woofer box, and being a low-ish floor stander I kept a top on as well. I ran the tests with the mid driver (compression driver not connected). Hard to see, but the baffle angles upward 10 degrees.
The box internals were lined with felt, and each configuration (A,B, C, and D) has at a minimum the baffle, top, and bottom. Not so unexpected, the more open the higher the fs, although each fairly close. The Qts went down (not sure if that makes any difference for this build). I used DATS for the impedance measurements. OK not really free-air in these 'boxes', but I wanted to see what the differences would be.
Additionally, I measured frequency at 18inches inline with the ctr of the coax. (Again, only the mid is being driven). Not surprising the low end falls off sooner as the open back 'box' becomes more open. I hadn't expected the peak rising before the fall. A real issue shows up with configure C which is a box without the back creating ripple-wave (dip). Configure A seems easy to work with (my goal was to have the mid play down through 360-380Hz before beginning its rolloff. D may be workable, I just may need to adjust my goal upward a tad, as a HP will manage the rise ~500hz and it doesn't exhibit the ripple issue of the configure C.
I went back to take a look at a vented design I had used awhile back with an Audio Nirvana 6.5in. Similar to config A, but just extended to create a ~tapered vent.
I tried to duplicate my previous measurements (not exact, but close) and the yellow line is shown with the previous config A and B measurements. Clearly extended through what now is a vent more so than opening. Measures Fs 87.2 and Qts 0.6555.
So, where I'm looking to cross down to woofer I may have some options. I'm leaning towards a non-port option.
Edit: I listened to music with a 1st order HP 190 (tgt down -0dB 380Hz upwards) which may benefit from a shelf to further limit the low energy to the mid. Image w and w/o LP.
Comments
Bonding (a couple of pins set and strapped clamped) the 1/8th in ply (3ply BB) to the front curved edge worked out - and fairly easily. I initially thought I had done a solid job cutting and sanding- but I could feel a couple of small imperfections. Absent a CNC machine, I’m happy with this as a guide for the side pieces. (the dark line between the ⅛ in and the board is the pencil line)
I built a test 'box' for the coax to run some initial comps for different open back-ish configurations. I won't be doing a full open baffle as this unit will sit on top of the woofer box, and being a low-ish floor stander I kept a top on as well. I ran the tests with the mid driver (compression driver not connected). Hard to see, but the baffle angles upward 10 degrees.
The box internals were lined with felt, and each configuration (A,B, C, and D) has at a minimum the baffle, top, and bottom. Not so unexpected, the more open the higher the fs, although each fairly close. The Qts went down (not sure if that makes any difference for this build). I used DATS for the impedance measurements. OK not really free-air in these 'boxes', but I wanted to see what the differences would be.
Additionally, I measured frequency at 18inches inline with the ctr of the coax. (Again, only the mid is being driven). Not surprising the low end falls off sooner as the open back 'box' becomes more open. I hadn't expected the peak rising before the fall. A real issue shows up with configure C which is a box without the back creating ripple-wave (dip). Configure A seems easy to work with (my goal was to have the mid play down through 360-380Hz before beginning its rolloff. D may be workable, I just may need to adjust my goal upward a tad, as a HP will manage the rise ~500hz and it doesn't exhibit the ripple issue of the configure C.
Purple squiggle for the win?
I went back to take a look at a vented design I had used awhile back with an Audio Nirvana 6.5in. Similar to config A, but just extended to create a ~tapered vent.
I tried to duplicate my previous measurements (not exact, but close) and the yellow line is shown with the previous config A and B measurements. Clearly extended through what now is a vent more so than opening. Measures Fs 87.2 and Qts 0.6555.
So, where I'm looking to cross down to woofer I may have some options. I'm leaning towards a non-port option.
Edit: I listened to music with a 1st order HP 190 (tgt down -0dB 380Hz upwards) which may benefit from a shelf to further limit the low energy to the mid. Image w and w/o LP.
