Dusty,
One aspect of horn termination generally overlooked in simulation is the room corner expansion rate.
David McBean wrote in this thread:
https://www.diyaudio.com/community/threads/multiple-cabinet-combined-response.204472/page-2
"The area expansion rate of a corner is the same as that of a triangular 90° conical horn. It is also the same as that of an axisymmetric (circular cross-section) conical horn having an included angle of 82.8°, assuming isophase wavefronts."
Wayne Parham wrote:
"The expansion from the room's corner is only somewhat "conical" until it reaches the ceiling, in which case it begins to become more of a parabolic expansion. Then by the time expansion reaches the opposite wall, it closes up completely. So indoors spaces are always constrained more than the major fractional radiating spaces we commonly talk about, i.e. half-space, quarter-space, and eighth-space."
Since you want the room to be an extension of the horn, thought these details will be of use in modeling.
Art
Wood chips won't act as a diaphragmatic absorber, since they are not a diaphragm.
Best case examples for them seems to be similar, but a bit less low frequency absorption than fiberglass or synthetic fibers.
Cost is good..
Baranek's Law reigns supreme - if you did indeed build such a monstrosity it would have to sound "good".
I had to look that one up: https://leachlegacy.ece.gatech.edu/beraneklaw.html
Apparently DIY ones own design for an enclosure guarantees it to sound better. For the builder.
Beranek's Law dates from 1954. Thats also the date on the cartoon above. I suspect Beranek got inspired by the cartoon.
Beranek's Law
It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.
Dustman's Law, eliminate all potential sources of distortion, it will have to sound good.
My only audio related cartoon I clipped out, still have and for a long time my goal or at least mimic it with multiple subs, which I ultimately did well enough to suit me.........
So there I was on my porch, thinking more about this project, and I got to wondering what would cause more distortion; a horn that is the room, but in it's path other fairly large horns to cover the other frequencies; or, a smaller horn/mouth radiating into a small room without anything in it's path(the projector screen being above the horn mouth with the other horns behind it) which would introduce a discontinuity and bring room modes into play.
My other concern with the horn-is-the-room idea is vibration of the projector screen from the sub horn passing right through it.
My other concern with the horn-is-the-room idea is vibration of the projector screen from the sub horn passing right through it.
Just scroll down a bit.. This is one way to have a "horn" room.
https://www.whatsbestforum.com/thre...hey-sound-and-issues-with-sonics.25071/page-2
Joe
https://www.whatsbestforum.com/thre...hey-sound-and-issues-with-sonics.25071/page-2
Joe
Nice find. That looks like it was inspired by the room in the south of France - minus the door between the horns.
That link is nothing but HORN PORN! Pure art in those designs. And, no 50 hertz B S. SUBwoofers playing to 20 hertz.
I decided to fire up my old copy of CARACAD room design software and have a go at a whole room horn. The preliminary results are promising.
CARA does not do horns, but I can sort of draw a horn shaped room by hand. My first drawings are crude, but show some idea of room reflections in a box room vs a horn room. So far I've just drawn 3/4 of a conical horn (flat top) and run reflection simulations in that shape vs a box room.
The room is worst case scenario for reflections being made of hard surfaces like brick and concrete, no absorption at all. Of course in a box room of 12x5.6x3 meters there are reflections galore that bounce from surface to surface and ring for a very long time. Even when the wall behind the listener is removed, reflections abound and rebound. But with a basic horn (no back wall) reflections are vastly reduced, with only a very low level bounce back from what might be the horn mouth.
Of course we all know that rooms with non parallel walls kill off, or at least scatter, reflections. And a room in the shape of a horn is almost all non-parallel walls.
The problem, of course, is the wall behind the listener, as mentioned in the OP. it needs to absorb bass in a major way. For simulation I simply eliminated the wall so that it could not reflect. But I have not yet found a sound absorbing materiel that does much in the bass. Even suspended chipboard, which should be 50% absorptive in the bass doesn't do much. The back wall still reflects.
At first glance the idea looks like it will work well, as long as you can find a way to kill the bass reflections at the mouth of the horn - the back wall. I looked at data for wood chips, but could not find much charted below 200Hz.
CARA does not do horns, but I can sort of draw a horn shaped room by hand. My first drawings are crude, but show some idea of room reflections in a box room vs a horn room. So far I've just drawn 3/4 of a conical horn (flat top) and run reflection simulations in that shape vs a box room.
The room is worst case scenario for reflections being made of hard surfaces like brick and concrete, no absorption at all. Of course in a box room of 12x5.6x3 meters there are reflections galore that bounce from surface to surface and ring for a very long time. Even when the wall behind the listener is removed, reflections abound and rebound. But with a basic horn (no back wall) reflections are vastly reduced, with only a very low level bounce back from what might be the horn mouth.
Of course we all know that rooms with non parallel walls kill off, or at least scatter, reflections. And a room in the shape of a horn is almost all non-parallel walls.
The problem, of course, is the wall behind the listener, as mentioned in the OP. it needs to absorb bass in a major way. For simulation I simply eliminated the wall so that it could not reflect. But I have not yet found a sound absorbing materiel that does much in the bass. Even suspended chipboard, which should be 50% absorptive in the bass doesn't do much. The back wall still reflects.
At first glance the idea looks like it will work well, as long as you can find a way to kill the bass reflections at the mouth of the horn - the back wall. I looked at data for wood chips, but could not find much charted below 200Hz.
Some further simulations had me wondering what could be done to absorb bass at the back wall. Perhaps the recycled denim insulation from Bonded Logic might work, its -19 is given as 97% absorptive at 125 Hz. It's not specified below 125 so I just took a wold guess and tapered it down to 2% at 5Hz.
Hanging thee curtains of this cotton insulation in front of the rear wall does a lot to reduce reflection, even down low. CARA's analysis says the room is over damped, very dead, but the Dirac simulation still shows some reflections coming off the rear wall and back into the horn. That said, decay is much faster and cleaner than a box shaped room. The horn shape doesn't allow the long reverb times that a normal box shaped room does.
Very heavy curtains and/or insulation in layers ought to kill much of the back wave, even down low.
Hanging thee curtains of this cotton insulation in front of the rear wall does a lot to reduce reflection, even down low. CARA's analysis says the room is over damped, very dead, but the Dirac simulation still shows some reflections coming off the rear wall and back into the horn. That said, decay is much faster and cleaner than a box shaped room. The horn shape doesn't allow the long reverb times that a normal box shaped room does.
Very heavy curtains and/or insulation in layers ought to kill much of the back wave, even down low.
......and as I've pointed out one way or another in various earlier postings; why regardless of the BW or alignment type, critically damping the speaker system is the goal, i.e. basically a PWT in concept, so for a such a huge horn within a horn we wind up with a huge room packed with some form of damping material(s) and/or end wall size diaphragmatic absorbers be them layers of super heavy drapes and/or solid panels or a combination thereof; ergo now just a matter of how much of what materials, construction is required to basically reactance annul such a system to offset its low end losses due to the mass quantities of damping required, which is way above my materials background, math skills 
, so 'color' me done.
Good luck! 🙂
, so 'color' me done.Good luck! 🙂
Yes, the whole thing would be a big challenge to design and tweak, but the results could be worth it. You'd have to be prepared to do a good bit of planning and then more work after building to get it right. I'd likely make the rear wall curved, and experiment with damping and diffusion.
What the sims don't tell me is how much apparent depth the sound would have. Having worked in three or four listening spaces where thee was 8-10 meters behind the speakers, that would be my preference - for sure. Depth in that space and be tremendous and highly realistic if it's in the recording. That's what floats my sonic boat. If the room has 10 meters to spare, I want that room behind the speakers. Would a giant bass horn provide that sense of depth? I do not know.
What the sims don't tell me is how much apparent depth the sound would have. Having worked in three or four listening spaces where thee was 8-10 meters behind the speakers, that would be my preference - for sure. Depth in that space and be tremendous and highly realistic if it's in the recording. That's what floats my sonic boat. If the room has 10 meters to spare, I want that room behind the speakers. Would a giant bass horn provide that sense of depth? I do not know.
Thanks for doing that Pano. Very interesting. The idea seems to have merit. Seems like 48 inches of Rockwool floor to ceiling brought out 3 feet from the back wall, with a curtain to hide it should absorb most everything. Does the software allow such a thing to be simulated?