Greets!
I don't do drawings even for myself, just some dims scribbled on whatever's close at hand, and I'm not familiar with what all is available to you or willing to spend a lot of time researching, so I just 'ran the numbers' using the SM-115K's published specs in a nominal 18 ft^3 MLTL tuned to 40 Hz:
L = 111.4"
base area = 486.57"^2
vent area = 128.68"^2
vent lenght = 0.75"
driver up from bottom = 41.12"
tapered pipe terminates to a point
This sims a ~98 dB/W/m eff. half space ~+/- 2 dB flat response with minimal stuffing, so down low this equates to ~101 dB/W/m plus any room gain. Not horn efficient, but good enough to achieve 'live' levels with all but the wimpiest of amps.
Normally I would just fold it in two, but if you plan to set your other horns on top, then it will require multiple folding. Put DIY adjustable spikes on the bottom to experiment with floor loading the vent if folding it in half or set it on the floor with the vent at the bottom front, side or rear to suit.
GM
I don't do drawings even for myself, just some dims scribbled on whatever's close at hand, and I'm not familiar with what all is available to you or willing to spend a lot of time researching, so I just 'ran the numbers' using the SM-115K's published specs in a nominal 18 ft^3 MLTL tuned to 40 Hz:
L = 111.4"
base area = 486.57"^2
vent area = 128.68"^2
vent lenght = 0.75"
driver up from bottom = 41.12"
tapered pipe terminates to a point
This sims a ~98 dB/W/m eff. half space ~+/- 2 dB flat response with minimal stuffing, so down low this equates to ~101 dB/W/m plus any room gain. Not horn efficient, but good enough to achieve 'live' levels with all but the wimpiest of amps.
Normally I would just fold it in two, but if you plan to set your other horns on top, then it will require multiple folding. Put DIY adjustable spikes on the bottom to experiment with floor loading the vent if folding it in half or set it on the floor with the vent at the bottom front, side or rear to suit.
GM