It is true that a narrower coverage angle yields a lower cutoff, this is clear from the waveguide equations ( i.e. a straight wall has a cutoff of 0 Hz.) And once this angle is set the impedance is fixed. But it does vary with angle if not length or mouth size. So I agree with you in general with this one caveat that wasn't clear from your description.
Yes, I hesitated whether I should mention it explicitly or not. I should have.
By a straight wall I meant "straight sided" (?) - e.g. all the common flat board horns, not a tube in particular.
So yes, the impedance is set by the wall angle, for a "conical" waveguide.
So what exactly makes e.g. an exponential profile different? Is it the continuously changing wavefront curvature what impedes the motion?
By a straight wall I meant "straight sided" (?) - e.g. all the common flat board horns, not a tube in particular.
So yes, the impedance is set by the wall angle, for a "conical" waveguide.
So what exactly makes e.g. an exponential profile different? Is it the continuously changing wavefront curvature what impedes the motion?
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Alright, can we exploit this somehow, with short exponential section at the throat and then nice profile after that to define the dispersion and rollback to smoothen things out? Or is this the sole purpose of OS profile, make the transition quickly to get the smooth impedance without reflections (and HOMs)? I remember mabat showed at some point that or example slight driver throat angle mismatch to the waveguide didn't matter much. Maybe we could get away with short section which sets the loading? I'm sorry I don't have too much knowledge on all this so it is just experimenting.
To continue the yesterday experiments here is the random-0 profile (k=2, 200mm depth) with pipe throat adapter added in 5mm, 25mm and 250mm in length. Even the very short 5mm added pipe changes the impedance, but not much of a change to the overall response except on very high frequencies. Longer pipe seems to introduce reflections (impedance wiggle).
This is conical throat extension with Throat.Ext.Length and Throat.Ext.Angle = 0 parameters. Can these define exponential expansion in ATH script somehow? It would be great if both impedance and pattern could be tuned separately. Complete control of the device would make everyone happy 🙂
Sorry to pollute your thread camplo, maybe my simulation posts should be moved to the ATH thread?
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1. GIF showing no throat adapter, 5mm and 25mm long straigt pipe.
2. mode lillustrating the 25mm pipe added
3. the 250mm pipe introduces crazy resonance, but the overall response is almost the same.
To continue the yesterday experiments here is the random-0 profile (k=2, 200mm depth) with pipe throat adapter added in 5mm, 25mm and 250mm in length. Even the very short 5mm added pipe changes the impedance, but not much of a change to the overall response except on very high frequencies. Longer pipe seems to introduce reflections (impedance wiggle).
This is conical throat extension with Throat.Ext.Length and Throat.Ext.Angle = 0 parameters. Can these define exponential expansion in ATH script somehow? It would be great if both impedance and pattern could be tuned separately. Complete control of the device would make everyone happy 🙂
Sorry to pollute your thread camplo, maybe my simulation posts should be moved to the ATH thread?
Attachments:
1. GIF showing no throat adapter, 5mm and 25mm long straigt pipe.
2. mode lillustrating the 25mm pipe added
3. the 250mm pipe introduces crazy resonance, but the overall response is almost the same.
Attachments
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Certainly, and thank you for your contributions in helping us understand the complexities.
My simplified take is mainly about picturing the realities in terms of horn size, weight, and shape, of whatever acoustic goals i have in mind. And finding a pragmatic way to assess the tradeoffs involved.
I totally forgot to add flare rate to mouth circumference and horn length, as one of what i like to think of, as simplified prime factors for lowest loading frequency.
Hi GM, i need some help understanding what you are saying...
I get that ≈89" diameter diaphragm will produce the same acoustic power at the geometric mean of the 20-120 Hz band, 49Hz;
as will the ≈2.783" diaphragm at the geo mean of the 120-20kHz band, 1550Hz.
The 5 octaves between the geometric means, gives a 4^5th displacement ratio, or 1024x area ratio. Which i get to tie with the diaphragm sizes.
Am i correct with you so far?
If so, it seems the acoustic power balance is for those two geometric means, and not for the full 20-20kHz spectrum.
The large 89" diaphragm can surely provide necessary displacement to 120Hz, but the small 2.8" diaphragm lacks sufficient displacement for anything below 1550Hz.
So I'm thinking i must be misunderstanding what you mean by 'acoustic power balanced 20-20 kHz!' That sounds like level acoustic output across the spectrum.??
Greets!
If I'm following, the ~ short answer is that this is strictly for driver sizing and once XO'd together it will sum as a ~ 632 Hz mean system and by my way of understanding all this [apm] will decay with increasing frequency at an acoustical power's 1/f.
In actual implementation, the 'sub' system would be scaled to the 'mains' system or some combination thereof to deal with the [extreme] overlap differential that we normally do, i.e. woofer + horn or in this extreme case the HF horn [line array, etc.] would need to load to ~ 49 Hz; which BTW it just 'dawned' on me that this is basically W.E.'s original wide range cinema system [15A horn + [4] big 15" - 18" woofer dipole bass array].
So once again, even at this extreme example the pioneers had already not just done it, but began with it due to time 'crunch' and worked backwards over time to 'shrink', fine tune it to the ever advancing performance requirements, 'bean counter's' 'demands'.
If I'm following, the ~ short answer is that this is strictly for driver sizing and once XO'd together it will sum as a ~ 632 Hz mean system and by my way of understanding all this [apm] will decay with increasing frequency at an acoustical power's 1/f.
In actual implementation, the 'sub' system would be scaled to the 'mains' system or some combination thereof to deal with the [extreme] overlap differential that we normally do, i.e. woofer + horn or in this extreme case the HF horn [line array, etc.] would need to load to ~ 49 Hz; which BTW it just 'dawned' on me that this is basically W.E.'s original wide range cinema system [15A horn + [4] big 15" - 18" woofer dipole bass array].
So once again, even at this extreme example the pioneers had already not just done it, but began with it due to time 'crunch' and worked backwards over time to 'shrink', fine tune it to the ever advancing performance requirements, 'bean counter's' 'demands'.
are you crazy!? I was just thinkin this tmuikku guy is really holding his weight with these great visuals! lol
I can reverse engineer pretty well from great visualizations. The thought I was having is how well the programing of this ath tool provides as a learning tool, inspiring some better usage of hornresp on my part. Thank you.
The highlighted area is what I would call the "root mode" or "fundamental" or "Tuning Note".....if you guys didn't already have a name for this portion of the response of a horn/waveguide.....your welcome
This is where the horn has max loading/resonance is it not?
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Well I would never use such a crap so I don't really need a name for it but I would think you could call it cutoff 🙂
I call it cutoff too but horn hornresp doesn't....go figure... I typed it but then redacted only to have you bring it up anyway lol...we need to be specific on how we each intend to define cutoff. Its an abstract noun though it can be defined by senses....it remains an idea first. I just gave my horn builder an ear full mainly because I am use to products lying about where "cutoff" is..... "product plays to 20hz".....10inch sub with 5mm xmax.. you don't say....I guess they aren't lying, rather, using a definition of cutoff, that differs from my own...
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BTW, if you took that device and scaled it 2:1 (i.e. made it twice as big, with 2" throat), the "cutoff" would be twice as low, i.e. around 400 Hz (let's say it's 800 Hz now). To make it 200 Hz you would have to either make it twice as big again, or make it even a more beaming monster...
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Just one more remark - the sharp peak in the impedance as presented here (which should mean there's a reflection somewhere), could be easily eliminated if one desired, that's pretty easy to do - it doesn't have to be like this.
(That peak will increase efficiency around that frequency, that's for sure. If it caused a local group delay rise in the response, which I can imagine it could, it would still be correctable with a simple EQ.)
(That peak will increase efficiency around that frequency, that's for sure. If it caused a local group delay rise in the response, which I can imagine it could, it would still be correctable with a simple EQ.)
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There was some ambiguity in what I wrote before, so let me write it again, hopefully a bit more precisely this time:
"Once you let the sound spread as spherical waves with a fixed center of radius, the loading is set. It doesn't matter how long or big you make the waveguide after the point where this happens. It will affect directivity etc., but not the impedance anymore. In OS waveguides (and the like) this transition from a flat to (nearly) spherical wavefront happens very quickly near the throat - that's why, for a given throat diameter and coverage angle, a 0.1 m (4") deep OS waveguide has virtually the same throat impedance as a 1 m (40") deep one (i.e. ten times longer with even a huge mouth). The whole length and mouth size is simply irrelevant for the "loading" in this case. And I suppose this holds for the flat board horns (DIY Synergy, etc.) as well - you simply won't increase loading by making the device bigger (in addition to what you already have)."
"Once you let the sound spread as spherical waves with a fixed center of radius, the loading is set. It doesn't matter how long or big you make the waveguide after the point where this happens. It will affect directivity etc., but not the impedance anymore. In OS waveguides (and the like) this transition from a flat to (nearly) spherical wavefront happens very quickly near the throat - that's why, for a given throat diameter and coverage angle, a 0.1 m (4") deep OS waveguide has virtually the same throat impedance as a 1 m (40") deep one (i.e. ten times longer with even a huge mouth). The whole length and mouth size is simply irrelevant for the "loading" in this case. And I suppose this holds for the flat board horns (DIY Synergy, etc.) as well - you simply won't increase loading by making the device bigger (in addition to what you already have)."
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What you can do, perhaps, is to add a secondary flare somewhere near the mouth, which would lead to a reflection and a resonance that would in turn increase the "loading" at some frequency, but that's about all you can do, IMO.
Yes, thanks. Since waveguides like OS or conicals expand very quickly at the throat, they do not load lower in frequency. That phenomenon and a definition of cutoff are explained very well in the paper familiar to many, that mountainmanbob linked earlier.
https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf
I think the idea of an exponential that transitions to an OS, like tmuikku is playing with, might provide some true loading a bit lower ?
In any case, i'm still in the mode of questioning the whole premise of trying to take CD's as low as possible. I guess it's just in the pursuit of a truer point source. Maybe CD's and horns will get there someday, sounding really good. The Axi and latest B&C seem to be trying with their horn combos, although I've found I don't like to use the B&C nearly as low as it's specs go.
Yes, there is no need to push to the limits, fine systems can be made without. I've got no time to pursue the experiments further and no absolute need either. Interesting problem/feature it still is, ability to tune both impedance and pattern independently to some extent, never thought it before. The info posted already should help when tuning ATH projects.
I think mabat has some interesting developments regarding the throat in the ATH thread, mainly HOMs and high frequency control in mind but never know if something comes up regarding the loading as well.
I think mabat has some interesting developments regarding the throat in the ATH thread, mainly HOMs and high frequency control in mind but never know if something comes up regarding the loading as well.
Well one idea is that we can create directivity down to a frequency we can't reach, with out using loading....Another idea, we can create higher directivity than a suitable mid woofer. Its not worth it if whats being directed isn't sounding good. Using the approach of keeping horn cutoff much lower than intended crossover, is it fool proof? Don't know....Marks experience with his horn, can't trust it without confirmed horn cutoff data.
To me, beaming is a sacrifice...maybe another of my "crazy theories" but doesn't the loading/beaming horn have a better Impulse response?
To me, beaming is a sacrifice...maybe another of my "crazy theories" but doesn't the loading/beaming horn have a better Impulse response?
subjective point. Who decides where the limits are and why....playing a Compression driver down to 800hz without loading is pushing it to the "limits" and it seems to work fine for many. Loading extends that limit...no big deal.
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Jeah you can push the limits of course, but there is no need to. I've got a philosophy for this too: mind the wavelength! 😀
It would be great if one driver could handle such wide bandwidth without issues but most of the time issues seem to appear just because of wavelengths being so different in size opposite ends of the bandwidth. One can use single fullrange driver sound system like many do. It lacks bass or the treble has problems and SPL capability is not very good. In a particular spot the sound is fine and this can be very enjoyable system, I've had one many years. But it is a dead end, can't get better performance from single driver because of wavelenghts. Can't get smooth 30-15kHz bandwidth and comfortably loud dynamic SPL, the simplified definition for good sound (nice wide bandwidth with enough SPL).
Modern software and construction techniques enable making impressive electromechanical products like the Axi driver or Purifi woofers for example. Still, either of these stellar products can't handle it all by them selves because the sound has varying physical size! In fact, I don't see any physical object ever capable of achieving perfect full range sound capability because any physical object would have a size, which relates to the size of sound and how the sound reacts with the object, and the size of sound varies by frequency! To overcome this physical property of sound we could inject it directly to the brain skipping the whole acoustic transmission with all its limitations.
From this simple fundamental thing we are working with, the sound and the physical size of it, we can now look at things from the perspective of wavelengths, the acoustics. We have suddenly realized that using multiple different size physical transducers and supporting structure for the different wavelengths can make us friends with the sound itself and not fighting against it wishing it worked out somehow when it doesn't. But, using many sound sources and having many different physical structures working in tandem in a listening environment to sum as good sound in the ear and then make the hearing system happy is not easy either and there is always many compromise.
For example a multiway point source sound system is very hard to pull off without issues because the varying sized transducers are on the way of each other and disturb the sound. We need to take every cheat we can come up with to try and circumvent the physical size limits to get better sounding systems. I like to think that a waveguide/horn is one cheat, it takes the very small transducer required to play the top octave well into bigger physical size (constant directivity). On the other end, we can cheat in the environment by using multiple woofers and statistics to average things out.
Alright thats about it, the philosophy in short. I think you are going to be fine with a device that beams given your application. Me on the other hand with my philosophies believe I should not sacrifice the top end for anything and it looks like I don't have to, just crossover to next physical size before the treble device gets into problems is enough to achieve a good system. There simply is no need to go any further, otherwise just use a fullrange driver which is very good and very simple solution with its limitations. If getting better treble means higher crossover, it doesn't matter, a free nugget since I'm gonna need to crossover to other physical objects that disturb the sound anyway no matter the crossover frequency.
But I am only a hobbyist and not university professor so there are huge gaps in the knowledge. Hearing system for example is a weird one and going for a low crossover could lead to better sounding system because of how hearing works I believe. But is it worth it if the treble was sacrificed on the same time? The system would still be one step away from being perfect.
Deep? No. Fundamental? yes. Mind the trade-offs 😉
It would be great if one driver could handle such wide bandwidth without issues but most of the time issues seem to appear just because of wavelengths being so different in size opposite ends of the bandwidth. One can use single fullrange driver sound system like many do. It lacks bass or the treble has problems and SPL capability is not very good. In a particular spot the sound is fine and this can be very enjoyable system, I've had one many years. But it is a dead end, can't get better performance from single driver because of wavelenghts. Can't get smooth 30-15kHz bandwidth and comfortably loud dynamic SPL, the simplified definition for good sound (nice wide bandwidth with enough SPL).
Modern software and construction techniques enable making impressive electromechanical products like the Axi driver or Purifi woofers for example. Still, either of these stellar products can't handle it all by them selves because the sound has varying physical size! In fact, I don't see any physical object ever capable of achieving perfect full range sound capability because any physical object would have a size, which relates to the size of sound and how the sound reacts with the object, and the size of sound varies by frequency! To overcome this physical property of sound we could inject it directly to the brain skipping the whole acoustic transmission with all its limitations.
From this simple fundamental thing we are working with, the sound and the physical size of it, we can now look at things from the perspective of wavelengths, the acoustics. We have suddenly realized that using multiple different size physical transducers and supporting structure for the different wavelengths can make us friends with the sound itself and not fighting against it wishing it worked out somehow when it doesn't. But, using many sound sources and having many different physical structures working in tandem in a listening environment to sum as good sound in the ear and then make the hearing system happy is not easy either and there is always many compromise.
For example a multiway point source sound system is very hard to pull off without issues because the varying sized transducers are on the way of each other and disturb the sound. We need to take every cheat we can come up with to try and circumvent the physical size limits to get better sounding systems. I like to think that a waveguide/horn is one cheat, it takes the very small transducer required to play the top octave well into bigger physical size (constant directivity). On the other end, we can cheat in the environment by using multiple woofers and statistics to average things out.
Alright thats about it, the philosophy in short. I think you are going to be fine with a device that beams given your application. Me on the other hand with my philosophies believe I should not sacrifice the top end for anything and it looks like I don't have to, just crossover to next physical size before the treble device gets into problems is enough to achieve a good system. There simply is no need to go any further, otherwise just use a fullrange driver which is very good and very simple solution with its limitations. If getting better treble means higher crossover, it doesn't matter, a free nugget since I'm gonna need to crossover to other physical objects that disturb the sound anyway no matter the crossover frequency.
But I am only a hobbyist and not university professor so there are huge gaps in the knowledge. Hearing system for example is a weird one and going for a low crossover could lead to better sounding system because of how hearing works I believe. But is it worth it if the treble was sacrificed on the same time? The system would still be one step away from being perfect.
Deep? No. Fundamental? yes. Mind the trade-offs 😉
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I guess you could say I am attempting to investigate, properly, the specs of this driver. Mark100 had an interesting philosophy towards amps that I've applied to horn.
So here I wouldn't use a horn smaller than what the Driver is specified for, which is to 300hz, which implies a 150hz horn or bigger to so properly, at least in a very strict approach....simply to know that I have the drivers full bandwidth available.
Always a trade off. Simply a matter of choosing which one you want to go with, no one is a loser.
There is something special about "full range", something particularly desirable about the coherency. This same attribute is selling the whole synergy/meh/unity approach no less. If one creates a midrange-hf single driver solution....Theres no particular reason why this solution would not have the same desirable attributes. How well this single wide band driver approach actually performs? I'm about to find out lol. I can only imagine that the future will provide even better options, in any direction a person might want to explore.
https://audioxpress.com/files/attachment/2705
So here I wouldn't use a horn smaller than what the Driver is specified for, which is to 300hz, which implies a 150hz horn or bigger to so properly, at least in a very strict approach....simply to know that I have the drivers full bandwidth available.
Always a trade off. Simply a matter of choosing which one you want to go with, no one is a loser.
There is something special about "full range", something particularly desirable about the coherency. This same attribute is selling the whole synergy/meh/unity approach no less. If one creates a midrange-hf single driver solution....Theres no particular reason why this solution would not have the same desirable attributes. How well this single wide band driver approach actually performs? I'm about to find out lol. I can only imagine that the future will provide even better options, in any direction a person might want to explore.
https://audioxpress.com/files/attachment/2705
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