Just to clarify, when I said that I understand completely... what I meant was that I understand that I'm moving into territory where the results are not likely to be good. I was not claiming to understand how object-based audio processing works. I definitely do not understand that. But am trying to learn.
This all makes sense and is what I was thinking. Start with a microphone and measure output and distances. Then the system like, say DIRAC, then adjusts frequency response, phase, and delay time for all of the speakers to make them work well together. Maybe it's not that simple? Or not that sophisticated?
At any rate, designing a speaker for directivity still sounds like a fun challenge.
Highly debatable (not about the carcinogen nature of loosened glassfiber but the efficiency of 'Auralex foam designed specifically for this').
Anyway,
You want to put Dirac in line with athmos processing? It could work but i would not be too sure ( i'm not into multichanel even if i know coarsely how this kind of dsp treatments are implemented). I would first study this: aren't athmos decoder integrated thingy? Like 5.1 receiver from the past century?. It could widely complicate things if that is the case.
Otherwise, for loudspeakers it seems to be a case for fractal array approach.
Look for member's Bbutterfield approach, it could be interesting.
Or Folgott approach: https://www.diyaudio.com/community/...directivity-and-horbach-keele-filters.284117/
It's surely a challenge and it could be fun. Or not. 😉
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i know it is against DIY ethos to use things that are designed by some corporation and marked up to what the market will bear
a DIYer wants to use commonly available low cost materials ( like plywood or fiberglass ) and design them into something of value himself
and without a doubt many things can work effectively to absorb sound, such as old pillows for example. if space and aesthetics are not an issue you can just use a little bit more of a slightly less absorbent material for same effect.
you could also build a speaker cabinet out of anything - you could use concrete for example - certainly it would be a lot more cool than buying a prefabricated speaker enclosure or flat pack kit from PE.
but personally i don't feel like i must personally design EVERY aspect of my setup. even top companies like Porsche and BMW don't design most of what is in their cars - they buy those things from suppliers. for example Mercedes says their C63 E-Performance uses technology they developed for Formula 1 because it has an electric turbo just like Formula 1 ... except they buy that Electric Turbo from Garrett ... and the top Bugatti buys the engine from Cosworth ... and all BMWs buy their transmissions from ZF and so on ... and that is FINE. the designer has an OVERALL VISION for the final product - no shame in subcontracting parts of the design out.
Auralex designed a foam product for sound absorption and marked it up pretty hard. Actually i would not recommend using it inside speakers as i have because it is a very stiff and dense foam - almost like styrofoam or a pool noodle - it isn't the loose kind of fluffy material we normally think of as foam. it could affect box tuning and maybe even cause an increase in distortion. It is really meant to be placed on the walls and i think it is well designed for that - comes in many shapes and colors.
can you build something with same performance for less money ? of course. do you HAVE TO do that in order to call yourself a DIYer ? i don't think so.
i like Auralex product and don't think there is anything wrong with a company charging a premium for something they designed that works well.
there are many different kids of foam you know. i actually made my own mattress out of Latex foam, which is also quite expensive but also like Auralex you will definitely feel the difference from regular foam. one thing they both have in common is they're heavy. but latex foam is really supple while auralex is really hard. i would say latex is heavier of the two though.
i don't think there is any shame in using the correct and best material for every application.
and here is another example. when my grandma was 98 the year before she died she was having a lot of accidents of every imaginable kind like knocking over drinks and so on and the carpet in her room was totally ruined with stains. i decided to replace it with some kind of surface that was washable and using the logic of @krivium i found what i thought was the highest performing material at lowest cost which was a puzzle mat tile for warehouses and garage floors ... it was rated for things like rolling traffic from casters etc. that every residential and even commercial vinyl product specifically said would void the warranty so i knew that material was TOUGH ! it was also a single layer of material all the way through and considerably thick whereas all other materials only had a paper thin decorative layer on top of a cheap substrate.
the company was not far from me here in New Jersey and i drove to their show room there ... when i entered they were installing some kind of epoxy flooring in part of the showroom and there was a horrible smell because of it ... i looked at the materials they had and they seemed perfect - very thick, strong, flexible - impossible to break interlocking system. it was the most bomb proof flooring product i have ever seen. i was impressed, so i took samples of different colors home with me ...
i was almost ready to order the flooring when i realized something ... the samples SMELLED ... and those samples were only like 2 inches in size - imagine having the entire floor emitting that smell. i then went on google and sure enough - many people reported the same smell - one customer waited a year for the smell to go away before giving up and ripping up the flooring because it was giving him headaches ... and he had it installed IN THE GARAGE. i almost installed that material in a bedroom !
after reading that i drove to a regular residential flooring store and installed a regular boring LVP floor that was not special in any way.
you want to be smart but you don't want to be too smart for your own good. it is possible to get too creative. there may be reasons why a certain material is better suited for a certain application that may not be immediately obvious.
even using Auralex inside a speaker box as i said in retrospect was a bad idea. i later learned that a material like that ( any effective foam ) can actually cause a measurable increase in distortion when used inside a subwoofer box because it is not necessarily linear and to use any more damping that is strictly necessary to control issues inside the box is thus counterproductive.
but to control sound reflections - it's great.
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Here is a short answer ( you've got a detailed one in PM Dissident Sound) as i don't want to go too much off topic:
You raised a very valid concern about potential health hazard about fiberglass.
Let's see what Auralex say about their own foam::
https://auralex.com/prop-65-1/
'WARNING: This product can expose you to chemicals including tris (1,3-dichloro-2-propyl) phosphate, which is known to the State of California to cause cancer. For more information go to www.p65warnings.ca.gov'
Then there is other potential health hazard: flammability behavior. In this case Auralex foam is not too bad regarding the material family, it is classed in my country as flammable retardant which means it won't burst in flame in second, it can even receive a chemical treatment to be even better. Not bad as other materials in this family will just burst into fire if you approach a lighter's flame.
Overall not bad but... it doesn't take into account another hazard which is the fumes/smoke. From test i've done with Auralex foam based products i wouldn't allow it close to me anywhere because of the fume they made during those tests. It not worst than other materials in this family but still.
Maybe things have changed since ( it was 20years ago) but i would not count on this as in my country they are still banned for any venue which host crowd ( called ERP rules in France).
In fact only Melamine is ok because like the mineral wools it is non inflamable, no flame, no lethal fumes/smoke.
Then there is the question about use of this kind of material in a sub: when you've got real efficiency above 250hz then it is questionable to use such material.
Depend where you xover. Filling can have a positive effect if your sub is sealed ( and then fiberglass shouldn't be a hazard in this case), not if BR. So here again you have to evaluate needs and define what is best to you.
Overall we mostly agree there is no ideal material but one is not really better than another... make your choice, pick your poison...
You raised a very valid concern about potential health hazard about fiberglass.
Let's see what Auralex say about their own foam::
https://auralex.com/prop-65-1/
'WARNING: This product can expose you to chemicals including tris (1,3-dichloro-2-propyl) phosphate, which is known to the State of California to cause cancer. For more information go to www.p65warnings.ca.gov'
Then there is other potential health hazard: flammability behavior. In this case Auralex foam is not too bad regarding the material family, it is classed in my country as flammable retardant which means it won't burst in flame in second, it can even receive a chemical treatment to be even better. Not bad as other materials in this family will just burst into fire if you approach a lighter's flame.
Overall not bad but... it doesn't take into account another hazard which is the fumes/smoke. From test i've done with Auralex foam based products i wouldn't allow it close to me anywhere because of the fume they made during those tests. It not worst than other materials in this family but still.
Maybe things have changed since ( it was 20years ago) but i would not count on this as in my country they are still banned for any venue which host crowd ( called ERP rules in France).
In fact only Melamine is ok because like the mineral wools it is non inflamable, no flame, no lethal fumes/smoke.
Then there is the question about use of this kind of material in a sub: when you've got real efficiency above 250hz then it is questionable to use such material.
Depend where you xover. Filling can have a positive effect if your sub is sealed ( and then fiberglass shouldn't be a hazard in this case), not if BR. So here again you have to evaluate needs and define what is best to you.
Overall we mostly agree there is no ideal material but one is not really better than another... make your choice, pick your poison...
A while ago was experimenting with increasing dispersion from a full range driver; some of my experiments had the opposite affect, so this is what I would try to see if it would "beam" - a full range driver with the wizzer cone removed, a piece of wood in front with an annular slot to beam the sound. If that didn't work, I'd try 6 small edge driven inverted dome drivers, like those used in AUDIOCORE computer speakers, as whilst sounding very good for the price, they do tend to beam, and 6 in arranged in a circle would beam even better. I think there would be a problem with high frequencies beaming to the celling, causing a time delay, but lower frequencies coming directly from the speaker.
I like this as a project. I've had it as a thought experiment myself, maybe a project to undertake for a friend who wanted Atmos, but not holes in their celling. Or even myself if it works well! 🙂
It might be beneficial to keep in mind that our ears are not great at vertical localization, especially at lower frequencies, so you could have the design intent to have the ceiling bounce speakers more as effects channels then full-range channels. Thinking of it that way, you could also high pass them at 500Hz or higher. That would have the benefit of a smaller speaker; a 10" horn, for example, can have tight beamwidth down to 1kHz, but not 200Hz. A CAD layout would be very helpful to determine what the beamwidth and angles would need to be.
Personally, I wouldn't dismiss that option out of hand. The ceiling bounce effect should be improved with less "direct" sound, and an ultrasonic array could be very good at that. But that's some supposition on my part, it would need to be tested.
From what I've seen, Dirac plus Atmos should be OK. Basically, get an Atmos system. Then use Dirac to smooth things out. We'll see. First I need some speakers for the Atmos. Making those will be the fun part. The rest is just spending money. 😀
Can't find the Bbutterfield approach. That Folgott speaker is interesting. It does have some directionality. And an unconventional arrangement of drivers. Although not much explanation as to how that arrangement came about or how it works. I'd like to learn more, but don't see much info.
Oh and I'm going to avoid the topic of sound absorbing materials for the moment. Should the project call for it, I'll investigate more later. For now, I'll hope that it's not relevant for this project. 😀
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That's an excellent suggestion. No idea if it will work. But it's a perfect thing to try in a simulator. Just see what happens. Plus the Folgott arrangement mentioned above. Basically, what I should do is fire up the simulator and try all sorts of things. 2x2, 4x4, Folgott, circle of 6, etc. Come up with other arrangements. See what looks good and try new ideas from there. I have not yet had a chance to get a simulator working. The job has been very long days this week and I'm about to start some work travel. But these are excellent ideas for me to play around with when I'm back. I'm looking forward to trying that. 😀
Thanks! It's noice to see a little enthusiasm for a project around here. 😀
For ultrasonics, don't they need all sorts of electronics to function, beyond the DIY scope? And maybe they can't play below some really high frequencies? Maybe not. I can look into it more.
Yeah, there are some contradictions here. Once the wavelengths get long, you lose directivity. Which is often a good thing, but not in this case. As I'm looking around at different full range driver options, from the drivers on their own, it's difficult to get much directivity even below, say, 2,500 Hz. So there will need to be some other design aspect to get directivity as low as possible. Or maybe it's not going to work. Don't know yet. If you, say, only target directivity at 2,500 Hz and above, it'll be pretty easy. But then the speakers are missing out on a lot of info. We'll see if something decent can be designed. The simulations that I want to do on different driver arrangements and sizes should be interesting to see what might have promise.
The 7-driver array in that thread looks interesting (ignoring the central tweeter). If you use the same distance ratios and keep the spacing pretty tight, with 2-inch speakers you get a decent portion of the performance of a square array using 16 drivers. The 7-driver version starts narrowing off axis at a slightly higher frequency, has more high frequency roll-off there, less directivity at compound angles, and some asymmetry in different axes, but the overall performance looks good for so few drivers.
www.diyaudio.com/community/threads/pseudo-coaxial-with-narrow-directivity-and-horbach-keele-filters.284117/post-4555895
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Really? I gave enough info for a search 😉
Search for Fractal Array by member Bbutterfield. It's not very detailed but he gave tracks to follow iirc.
Here again really? 😉
It's in the link i gave... 'the whole story here ( but in german)' he says, nevertheless it's here:
http://hannover-hardcore.de/infinity_classics/!!!/Dokumentation Quasikoax Prototyp.pdf
It's not really different from Bbutterfield approach iirc discussion we had in private some years ago. The thing is it use Horbach-Keele filters which had been developped to help with vertical directivity management in vertically aligned drivers pairs. Except both Folgott and Bbutterfield used them in vertical/horizontal alignements/layout with more or less random driver alignement. What Mattstat commented about and simulated.
This Horbach-Keele filters are FIR and as such induce latency and some fixed relationship in center to center distance of drivers for a given coverage angle.
Take a look at DB Keele site the AES presentation of the approach ( there is two parts) is availlable in the whitepapers, it's detailed including a 'regular' design example.
There is not many options for high directivity i can think about: either from the driver ( eg ribbon are extremely directive in vertical plan), from the layout ( but might need 'special' filters) or waveguide/horns. Or a mix of those.
It's not very difficult to achieve for mid/high, it's much more a challenge for low/low mid freq as Hornbach Keele paper present ( for control to circa 100hz you would need something like 1,6m ctc distance which makes for huge box if implemented for both horizontal and vertical).
If using horns/waveguide, MEH should be considered too imho, but size will be huge too.
I think you get the issue regarding using ceiling as reflector: the low/low mid might arrive 'too soon' to your hears. A FIR filter profile could counteract this but it might not be easy to target.
It's fine with me, the reason i pmed my detailed answer not to derail your thread.
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Yes, I found some interesting things. Most notably this interesting read:
You are in there. 😀 Not exactly what I’m after, but definitely interesting and relevant. Basically how polar plots change for linear arrays. There are a lot of insights, it goes in a different direction, and I’ve not yet digested it all. This quote jumped out at me:
“I've noticed with arrays in general, that the more drivers you use, the less sever the peaks and the dips are. If you have two drivers in an array you're going to get a really strong null at 30 degrees off axis. (https://www.diyaudio.com/community/threads/what-causes-off-axis-nulls.342494/) Add two more drivers, and the depth of the null is reduced. Add four more, it's even less of an issue. Etc etc.”
Ah, OK. Did you see the .pdf file within that link “Manipulating Directivity?” It’s excellent. And has some of the very basic, general info that I’ve been after. The Horbach-Keele filters are even mentioned.
I still need to think things through more. But the file implies that we could get enhanced directivity by using drivers with as large of diameters as practical (such that you still get high frequency output). mattstat mentioned this earlier. Then add a waveguide or horn for further directivity. Then, from other sources, make an array of these multiple large, horned/waveguide drivers. Finding large, full range drivers with waveguides/horns may be challenging. But it's maybe an interesting direction to think about.
Very interesting! Maybe it’s something like I mentioned earlier where you try to get the distance between drivers to be different. To spread things out. Much like how in a 2 way MT design you offset the teeter from the center line and have the distance from the tweeter to the left, right, and top all be different.
Also interesting is how different speaker array types are looking. It’s not a direct comparison, but taking two of your simulations…
16 x 2” divers, the peak at ~4,500 Hz is down ~20 dB from the top:
But in the case of 4 x 4” drivers the peak at ~4,500 Hz is only down ~10 dB from the top:
I really need to get a simulation system running so that I can start comparing all sorts of arrangements.
Anyways, some themes are starting to emerge to increase directivity- arrays, larger drivers, full range, horns/waveguides. Tentatively.
I’ve been reading more about how to get directional sound. A very interesting topic! Having arrays of drivers with canelletions and such is one way to go, but there will still be some sound spilling out here and there. What looks to be more promising, at least for now, is the use of parabolic reflectors. Lots of info out there.
The basic idea is to get a parabolic reflector. Put a speaker(s) in the middle, pointed at the reflector, and then the sound reflects out in a cylinder. The sound will stay directional at frequencies down until the radius hits the frequency length.
OK, how can we build a prototype for testing? Look around for a good reflector. Lots are available, such as for lamps. But you don’t know how parabolic those shades and photo reflectors really are. Plus many are crazy expensive. I found two sources that look promising. One is for these plastic reflectors, which seem to really be true parabolas:
https://www.wildtronics.com/parabolicdish.html
$85, plastic, durable, has a hole in the middle for poking a driver through, 22” diameter. They say exactly where the focus point is. A little large, but seems to be a good option for playing around to test the concept. Would keep sound directional down to about 1,100 Hz, which seems about as good as we’re going to do.
And these optical parabolas:
https://www.edmundoptics.com/f/larg...gvq2HIEJ5JXoiroIl6V73mzYRij7MRM9SEFX9M0-dYglk
12”, 18”, and 24”. $65-$125. I like the 18” size, but the hole in the middle is only 1.125” diameter, which might be tricky for what I have in mind. But it’s an option.
How to build a prototype? You could suspend one full range driver in the middle, pointing at the bottom of the dish. But there is a hole there where you will lose sound. Plus it might be tricky to hang an entire “cabinet” for the driver in the middle of the dish. This cabinet would need volume for bass output. I realize that bass is not a priority here. But we probably don’t want to try playing a driver hanging in free air. So instead, I’m thinking about the following…
Get a 5 way PVC coupling like this:
Put 4 full range drivers on the 4 openings. In the middle 5th position put a piece of long PVC pipe. The long pipe will both be a place to go through the hole in the dish to hold the 4 drivers at the focus point and also to provide volume for the drivers. Tune the length of the PVC to whatever volume you want. (Maybe add an adapter and move to larger diameter PVC pipe below the dish if more volume and less length is needed.)
Find 4 full range drivers with round flanges to seal onto the PVC. Pick drivers with sizes matched to fit the available PVC sizes.
Try to sand down the 4 PVC openings to add an angle such that the drivers point at the dish at something approaching the correct angle for a proper reflection outward. I’m guessing that making the angle in the PVC at the correct angle would mean that the rear of the drivers will bump into the inside of the PVC. So just try to add as much angle as possible. Or add a 30° or 45° elbow to each of the 4 openings? This angle aspect need some more thinking. Actually, having the drivers just stay 90° from the long pipe might be the correct reflection angle. So no sanding or funny angles needed.
The general idea might look like this simple drawing:
Not sure how I’ll hold it all up yet. Ideally, I can have it arranged horizontally, to test the directionality of the sound by walking past it, back and forth. Then put it vertically, like in the drawing, to test it bouncing off the ceiling.
A couple of drivers that look appealing from an initial round of seeing what is out there:
Tectonic TEBM35C10-4. It’s about 2” in size, $8
https://www.parts-express.com/Tectonic-TEBM35C10-4-BMR-2-Full-Range-Speaker-4-Ohm-297-216?quantity=1
Peerless by Tymphany NE85W-04. It’s about 2.5”, $50 (But was $33 a few days ago.)
https://www.parts-express.com/Peerless-NE85W-04-2-1-2-Full-Range-Woofer-264-1052?quantity=1
I don’t know if this is silly or not. But it sure sounds to me like something fun to try out.
😀
The basic idea is to get a parabolic reflector. Put a speaker(s) in the middle, pointed at the reflector, and then the sound reflects out in a cylinder. The sound will stay directional at frequencies down until the radius hits the frequency length.
OK, how can we build a prototype for testing? Look around for a good reflector. Lots are available, such as for lamps. But you don’t know how parabolic those shades and photo reflectors really are. Plus many are crazy expensive. I found two sources that look promising. One is for these plastic reflectors, which seem to really be true parabolas:
https://www.wildtronics.com/parabolicdish.html
$85, plastic, durable, has a hole in the middle for poking a driver through, 22” diameter. They say exactly where the focus point is. A little large, but seems to be a good option for playing around to test the concept. Would keep sound directional down to about 1,100 Hz, which seems about as good as we’re going to do.
And these optical parabolas:
https://www.edmundoptics.com/f/larg...gvq2HIEJ5JXoiroIl6V73mzYRij7MRM9SEFX9M0-dYglk
12”, 18”, and 24”. $65-$125. I like the 18” size, but the hole in the middle is only 1.125” diameter, which might be tricky for what I have in mind. But it’s an option.
How to build a prototype? You could suspend one full range driver in the middle, pointing at the bottom of the dish. But there is a hole there where you will lose sound. Plus it might be tricky to hang an entire “cabinet” for the driver in the middle of the dish. This cabinet would need volume for bass output. I realize that bass is not a priority here. But we probably don’t want to try playing a driver hanging in free air. So instead, I’m thinking about the following…
Get a 5 way PVC coupling like this:
Put 4 full range drivers on the 4 openings. In the middle 5th position put a piece of long PVC pipe. The long pipe will both be a place to go through the hole in the dish to hold the 4 drivers at the focus point and also to provide volume for the drivers. Tune the length of the PVC to whatever volume you want. (Maybe add an adapter and move to larger diameter PVC pipe below the dish if more volume and less length is needed.)
Find 4 full range drivers with round flanges to seal onto the PVC. Pick drivers with sizes matched to fit the available PVC sizes.
Try to sand down the 4 PVC openings to add an angle such that the drivers point at the dish at something approaching the correct angle for a proper reflection outward. I’m guessing that making the angle in the PVC at the correct angle would mean that the rear of the drivers will bump into the inside of the PVC. So just try to add as much angle as possible. Or add a 30° or 45° elbow to each of the 4 openings? This angle aspect need some more thinking. Actually, having the drivers just stay 90° from the long pipe might be the correct reflection angle. So no sanding or funny angles needed.
The general idea might look like this simple drawing:
Not sure how I’ll hold it all up yet. Ideally, I can have it arranged horizontally, to test the directionality of the sound by walking past it, back and forth. Then put it vertically, like in the drawing, to test it bouncing off the ceiling.
A couple of drivers that look appealing from an initial round of seeing what is out there:
Tectonic TEBM35C10-4. It’s about 2” in size, $8
https://www.parts-express.com/Tectonic-TEBM35C10-4-BMR-2-Full-Range-Speaker-4-Ohm-297-216?quantity=1
Peerless by Tymphany NE85W-04. It’s about 2.5”, $50 (But was $33 a few days ago.)
https://www.parts-express.com/Peerless-NE85W-04-2-1-2-Full-Range-Woofer-264-1052?quantity=1
I don’t know if this is silly or not. But it sure sounds to me like something fun to try out.
😀
Reflector can definitely works. After all ther is 'canon' microphone so what exist in one side of transducers exist in the opposite too...
But the question remain the same: down to which frequency?
You could ask Art ( Weltersys) he played with very narrow dispersion in the past ( including his 'jericho' horns and some toys to tricks people at halloween iirc).
But the question remain the same: down to which frequency?
You could ask Art ( Weltersys) he played with very narrow dispersion in the past ( including his 'jericho' horns and some toys to tricks people at halloween iirc).
Right. Parabolic reflectors are used for microphones. It should work for speakers, too, which are just the reverse of the microphone. And has been shown to do so, by people including Art/Weltersys, as I have read. So the idea is not new. Maybe it has not been used in this context that I am after, a ceiling reflection. At least not that I have seen yet. Could be a fun experiment.
For the lower limit of frequency, it will just be the radius of the reflector and what frequency that distance correlates to. So for a 22" parabolic reflector, an 11" radius correlates to about ~1,100 Hz. Everything above that will be directional. Below that and it will not be directional. A bigger (or smaller) reflector will be directional to lower (or higher) frequencies.
For the lower limit of frequency, it will just be the radius of the reflector and what frequency that distance correlates to. So for a 22" parabolic reflector, an 11" radius correlates to about ~1,100 Hz. Everything above that will be directional. Below that and it will not be directional. A bigger (or smaller) reflector will be directional to lower (or higher) frequencies.
The speaker's polar pattern determines the near field response, most of it's radiated sound will bypass the reflector dish. If using a very narrow horn source directed at the dish, the near field sound will be minimized to the extent of the horn's directivity, but the -6dB near field spill will be louder than the reflected ceiling sound. The Haas effect will place much of the perceived location at the point of first arrival.
I used a six foot diameter dish driven by a 13 x13 degree conical horn, and later copied it's profile to a 45" x 45" (truck box integer) reflector. Reflecting off a wall about 20 feet away, the high frequencies appeared to be coming from it.
That said, the same could be said using the Maltese horn by it self.
22" is far too small a diameter to be of use for the effect you are trying to achieve.
You could fill the hole with absorptive material, the speaker pointing at the dish blocks (and reflects...) the center parabolic reflections anyway.
4" will be slightly more directional than a 3.5":
Below ~2kHz, the 4" drivers would be near omnidirectional, most of their sound would spill out of the dish.
The center to center distance between the drivers will cause lots of comb filtering across the reflected image, reducing the realism of ambient effects.
The smaller the driver, the higher in frequency it will "go omni".
I had lots of fun with my 1999 parabolic and 2013 HyperboLine ™ Projector tests, learned a lot, and walked many miles doing them.
Only used the parabolic projector on one gig for announcements, reflecting off the roof of a very long tent.
For your application, the used of combined ultrasonic sound as used by Akoustic Arts, Holosonics, or similar products is more effective in restricting dispersion than even a six foot diameter dish.
https://www.akoustic-arts.com/produ...nics-ultrasonic-audio-waves-system-panphonics
That said, ultrasonic range is limited compared to parabolic or hyperbolic reflectors due to high frequency air absorption, the ultrasonic devices have more distortion than conventional drivers, and I am concerned about the long term effect of the high SPL ultrasonic sound used in these devices on hearing.
Art
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