Yes, seems a rather impossibly large cutout for the size of enclosure. Maybe I should have called them “Shoehorns” (foreshadowing?).
I plan to try out a design philosophy that I’ve had at the back of my head for years. One that seeks to maintain sensitivity by baking BSC into the design. It employs a combination of 1) selecting a woofer with a natural response rise towards the LF region. 2) Use a large baffle to reduce the baffle step frequency range. 3) Employ a high Q enclosure alignment to boost the region below where the rising woofer response tops out and begins to fall off.
Obviously I’m a bit limited on the baffle size though.
Definitely interested in trying that sometime. Though I’d need to figure out if I can model it with the tools I use. And if it is feasible to use lower cost capacitors. I don’t have a stack of large value poly caps to draw from.
Harrrrumf! I was going to suggest a few of these in parallel to hit your goal capacitance… but it seems all the large size NPE caps at PE are out of stock
I got some npe 100uFs form Madisound and PE and Madisound’s M.D.L. npe caps measured closer to spec and were a little cheaper. No idea if that holds true for all values, but I had 4 MDLs and 4 PEs to compare.
I’ve used series run DC polarized caps back to back too. Daryl over on PETT back in the day swore by the old blue Sprague canister caps from old servers, PCs, etc; ran negative to negative in series. Remember that halves the value, but yields higher voltage capability. Apex Jr has great prices for 1000uF polarized caps.
If it makes you feel better you can parallel a poly for part of the value. Since most applications like this take 200uF or more depending on cutoff and impedance load, there is room for adding to make value.
You don’t have to get something like these film 600uF monsters:
And in this enclosure it would get a QTS of around 1.186. F3 just under 50hz (.5ohm coil dcr added, note .5db increments) Though the F3 may actually end up in the mid 50s if the Q bump becomes the true response knee:
For the current price It ain’t playing around. I’m pretty sure I measured 6.5" Dia on the magnet. It might be bit of a handfull to cross in a 2-way and get sounding OK, judging by the response plot and resonances seen in the impedance plot. But I’m game to give it a try.
The baffle step midway point should be somewhere between 250-350hz just based on baffle dimensions. Not factoring in any other… additions. So hopefully that is low enough for this all to play a notable roll in.
(foreshadowing?).
