Ukko Kari

The resistance of the heating elements will change from the beginning to the test to the end of the test if you do not immerse them in water. This will change the results of the calculation of power into the load slightly.

When I have had the time to do some serious listening after integrating with my other ~17 hz tuned subwoofers, the experience is quite visceral. Even at low output levels, there is a sense of weight that is hard to describe.

Moving up and down stairs to roundover, sand, fill any tear out, sand and paint was a bit of a chore, requiring assistance of a hand cart, ratchet straps and a strong volunteer. Also, the number of good weather days were limited, coupled with working away from home a lot meant that I could not spend as much time working on these as I would have liked at a time. Second one is partially assembled.

Before adding a subwoofer, if you add baffle size with foldable / detachable wings and top / bottom panels you will increase forward directivity which is useful. Of course, this comes with the caveat that it will make the monitors heavier, not to mention easier to tip over if the wind whips up. This moves the baffle step frequency lower, and may require a bit of tailoring with eq. Wings could be made from dollar store / craft store foam poster boards or 1" xps foam board, assuming you do some rudimentary bracing. Considering you are using a car for transport and are short on space a pair of larger boxes instead of 3+ boxes may make more sense. Perhaps a pair of decent commercial passive speakers like the Behringer B215XL. Cheap, relatively robust. https://www.musiciansfriend.com/pro-audio/behringer-b215xl-15-1000w-passive-pa-speaker/580026000000000?rNtt=passive speaker&index=2

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Awesome work as always Josh, refreshing to see out of the box thinking.

If the holes for the magnets are drilled into the rear of the baffle that will reduce the amount of finishing work needed, compared to drilling the front side of the baffle.

Common pvc pipe can be molded with heat to form flares like this: https://www.subwoofer-builder.com/port-flares.htm The most correct answer without any conjecture or rule of thumb is to calculate how far the slug or slugs of air needs to move back and forth to produce the same sound pressure level at tuning. One can do that even with a program like winISD, using the port area as driver Sd.

Almost 2 months away from home, with little time to work on these boxes. One box is completely assembled and flush trimmed, needs roundovers and Duratex.

A better option than a simple 90 degree short radius elbow fitting would be a sweep elbow. Here is a table on the frictional losses of different pipe diameters and the types of fittings. http://media.wattswater.com/orion-hp-frictionloss.pdf 4" long radius sweep elbows are utilized in electrical service installations, you may be able to source something locally. If you are on Mac or Linux, you could use Wine to install WinISD, if you desire. Regarding port length, this depends on how close in proximity the port inlet and outlet are to boundaries, this can change the actual installed length for the desired tuning, and if an inner flange or torus is used on the end of the pipe.

Not much of an update, since I haven't had a chance to work on this box or it's mate, but here's a few more pictures. There was a small error in the angle of the slices cut with a homemade large miter box and a handsaw, which were edge sanded before gluing, which resulted in a greater than 90 degree angle. The bottom and top of the enclosure need bracing, which will be tied into the front and back, and a few side to side braces will be installed around the driver beside the port before gluing up the last side.

Stuffed one port with a pillow, but I find it hard to nail down tuning exactly with the inexpensive homemade jig, though it looks close to 14 hz, which will drop some when the cabinet is standing upright, and the ports are closer to the floor.

I will be building a pair, have some materials on hand for the second one now, but have to go out of the city for work so it will be some time before I complete both of them. I can certainly stuff one port and check the tuning.

Added a screen shot of the impedance simulation for 16.5 cu ft net, 17.6 hz tuning.