Hello all,
I'm fairly new to this forum and have been studying several threads for a while now. I've finally plucked courage to share my first software guided build so you all can run a critique that will enable me do better next time. I have built a pair of floor standing passive 12 inch Subwoofers as well as the surround speakers that go with it (5.2). I desired to experience frequencies around 20Hz and below but with as little box volume and floor space as possible. I chose the 12 inch Epik sentinel Subwoofer drivers (not Epic!) because it seemed to my untrained mind to be built for as low a frequency output as possible in the smallest enclosure (not to mention that it was going for a bargain price). Here are the T/S parameters
After spending some time on WinISD, it seemed to me that I could get away with a 3cuft enclosure which with a 4th order LR crossover at 80Hz appeared to give me a fairly flat 3dB FR range from 18 to 85Hz when tuned to 19.5Hz.
Ports:
Dual 3.375" diameter ports seemed ok to me. Larger (4") ports would have been better airspeedwise but would have resulted in longer ports with audible resonance and a larger box than I intended. I reckoned that with 600 watts ceiling on power (since I was not planning for high SPL but a bit of a subsonic experience which I've never had) I might make do with this port size.
SPL:
The driver has a fairly low efficiency which is worsened by its highest output being at upper subwoofer frequencies (125Hz) which will mostly be cut off by the crossover.
Group Delay:
This appeared to get worse as one tuned higher (i.e 20Hz and above) for the same enclosure volume. On the other hand tuning lower seemed to reduce SPL.
Port Air Speed:
WinISD's port speed at 600 watts looked rather high but I figured that the maximum possible flaring I could achieve at the ends of the ports should shave off up to 8m/s of air speed. Core compression however may be a serious issue from 400 watts on. I couldn't think of any other way round this since I was reluctant to put more than 12.5Hz of 2nd order highpass on it for fear of limiting subsonic performance. In the process of wood work, I discovered that the maximum flaring looked really good and so was adopted as design aesthetics.
Wood Work:
I worked with a Carpenter on this project (not being hands-on myself) but I designed and directed every stage of the work. This is because skilled workmanship and necessary tools are hard to come by in my zone and I needed to maintain quality and find ways around unavailable tools. The boxes were made based on WinISD plans long before the drivers were shipped in. It was left to see whether the performance would match up with the simulation. Flush mounting was a huge challenge because it was done after the fact as the external driver diameter was not known at the time of cutting out the driver seating (a substitute driver was being used in the box while Epik driver shipping was delayed).
Please pardon the quality of workmanship (and planning too).
.