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

🤣

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.

Side panels are just clamped in place at the moment, and bracing is not fully complete yet. From a quick and dirty estimate, cone excursion minima is in the 17-18 hz range. Edit: quick impedance measurement taken, tuning looks to be 17.6 hz.

Ports are complete, PL max is curing, and 4 out of 6 pieces of wood are glued together, I had a good friend and AES fellow come by and help out.

This is a shot of the inside of the elbow before the other lengths were added. A few coats of Duratex with sanding in between make the surface fairly smooth.

Thanks! 'Respiro Del Diavolo' is the name I am kicking around for these. 😀

One port out of 4 ready, second one is almost complete.

Starting work on a pair of subwoofers utilizing the 8 ohm version of the DS115. Ports are sonotube, and to make them fit in the enclosure, they will have a 90 degree bend. The external dimensions of the enclosure will be 49 inches tall, 36 inches wide by 24 inches deep. Dual 9.25 inch sonotube ports will eat up about 4 cubic feet of room in the box, driver is .53 cubic feet. Bracing will be fit around the ports and the driver. External cabinet volume is 24.5 cubic feet, or 693.76 liters. Time is sparse to work on these, so they likely will not be operational until the new year.

Can anyone link a video of the sound? My hypothesis is that the shorting ring or rings are loose, and moving in response to forces generated by the coil. I should check my recently purchased 21DS115 for extraneous noises before building a cabinet.

Interesting read, thanks. I have read a few articles from John Allen over the years, though I had not read the "Missing" article before. I concur that distortion makes a source seem louder than it actually is, and that people need to use their ears and not their eyes listening to sound.

For the moment I will just replace it with another. I have a bunch of filters loaded in a DCX 2496, but work has been crazy, lots of overtime and not enough free time to swap it in with a QSC. Fast and easy to flash another Nu3000DSP. Crown should have taken notes from Berhinger on the user friendliness of the DSP.