I am curious if there was any design work, or implementation of a DIY 15"-18" tapped horn subwoofer with a target of 20hz or below?
I am just curious as to the dimensions of such a beast.
I was thinking of a design using two large woofers at either end of a unfolded horn. Something like this;
I am just curious as to the dimensions of such a beast.
I was thinking of a design using two large woofers at either end of a unfolded horn. Something like this;
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Per my various HR sims, 16 Hz starts around 285 L and can top 1 k L net depending on driver specs.
If you have the space for it then a 5 meter long Tapped Pipe with two 18 inch drivers could be quite spectacular. You could always go for better suited driver like the B&C 18DS115, which is more expensive but will result in a smaller enclosure and better output.
The red curve is spl response 2.0 Volts into two 8 ohms driver in parallel. The mouths of the huge tapped pipe radiating into the corners of the room.
The green curve is simulated max spl based on 8 mm xmax and a 1000 watt amp.
This is a fun idea, so I simulated the mighty B&C 18DS115 in something quite similar. It is almost half the size, but with a much better maximum spl. I still used the same theoretical 1000 watt amp for max spl simulation. Blue and purple curves are the 18DS115-4 in series for a nominal 8 ohm load. Red and green is the same as in my previous post, which I kept for comparison.
A somewhat simpler to build design. It is just an idea. I would leave the magnets protruding into the closed entry part of the tapped pipes to avoid turbulence, since you will have very large air column amplitudes at these low frequencies.
This is DIYAudio not DIY Music😈 As said above the purpose is movie special effects.🙂
The physical reason is because I have a ~15.5' living room which I could make a cabinet which extends wall to wall.
My room is ~15.5' wide. For SAF I could make a "nice" cabinet which went wall to wall with a driver in each end. I was thinking a UM18-22 or Lavoce 18" drivers, but am open to any similarly priced drivers available in the US. For folks with true home theaters this might be an option under/behind the screen.
Since the woofers are near the corner boundaries, there would probably be a boost from this as well.
FWIW, I wouldn't use THs or the like if I really wanted to go down low. All the harmonic resonances caused by using the long paths required may end up producing undesirable effects that may not be addressable by low pass filtering.
Instead, I'd look at using a driver with low Fs and long Xmax in a passive radiator alignment. Like the Dayton Audio MX-15 in a 150L box tuned to ~20 Hz with two 15" PRs, for example. Or the Dayton Audio RSS460HO-4 in a similar sized box tuned to around 18 Hz with two 18" PRs.
Instead, I'd look at using a driver with low Fs and long Xmax in a passive radiator alignment. Like the Dayton Audio MX-15 in a 150L box tuned to ~20 Hz with two 15" PRs, for example. Or the Dayton Audio RSS460HO-4 in a similar sized box tuned to around 18 Hz with two 18" PRs.
One of my favorites! Went to all three nights of his 'You Had To Be There' concerts at the 'Fabulous' Fox Theater and as good as the live recorded Album was for the times, it was like comparing life to a bland painting! This was my daughter's first concert, so got a heck of a jump start to being a live performance junkie like her old man. 😉
Anyway folded in half leaving ~6" for building tolerance = ~30.5 ft, then speed of sound in feet/4 (because the pipe is a 1/4 WL resonator)/30.5 ft = a ~9.25 Hz TH. Obviously you don't have to tune it this low, just showing what's possible.
Anyway folded in half leaving ~6" for building tolerance = ~30.5 ft, then speed of sound in feet/4 (because the pipe is a 1/4 WL resonator)/30.5 ft = a ~9.25 Hz TH. Obviously you don't have to tune it this low, just showing what's possible.
I have considered multiple inexpensive woofers in various configurations as well. My thought was two towers of 8, 10"-12" subs in an opposed configuration. Four woofers on each side of each tower. Perhaps these;
https://www.parts-express.com/GRS-10SW-4-10-Poly-Cone-Subwoofer-4-Ohm-292-482
or
https://www.parts-express.com/GRS-12SW-4-12-Poly-Cone-Subwoofer-4-Ohm-292-484
But here I am helping to hijack my own topic.🤔