That simulation looks fine already, quick glance I don't see narrowing? DI is smooth, xo is likely about 1-2kHz and there the response wiggle is due to xo mostly I think. Above that, 3kHz, 5kHz.. just use EQ to flatten your listening axis as the DI is smooth. The wiggles seem to be about 1db, so already pretty dang good.
Here is education from hobbyist: Sound interacts strongly with physical objects whose size is similar to wavelength. If object is much smaller than wavelength and the sound just goes around without much effect. If it's much bigger and sound just reflects back. In between, sound goes also around (this is diffraction), and while doing that might emit the backwave. Thus, if you measure ideal sound and there is physical object in the way, you could look at the measurement and roughly estimate size of the object looking at wiggles at various frequencies.
For example, If you have an apple, which is roughly 3kHz in diameter, about 10cm, it would be big for 3kHz wavelength and higher and makes diffraction and reflection happen, but for example 300Hz is already roughly 1m in wavelength, and an apple would show no effect in your measurement plot at this long wavelengths, it would be "invisible".
So, if your waist banding was about at 1kHz, which has 34cm wavelength, I'm sure the physical feature that causes it is about that size, definitely bigger than about 10cm, and smaller than 60cm, very likely some dimension of your device. Specialty of diffraction backwave is that it's opposite phase, so makes quite unique pattern on polar graphs easy to identify, and easy to reason where it likely occurs.
Anyway, realizing that frequency (wavelength) is related to physical size you may reason with your object (speaker) and measurement data. If you want some narrowing or widening or any other acoustic feature you see on your polar map to go up in frequency, you must shrink physical size of the thing that is responsible for the "feature". If you want the feature to lower frequency, make your object bigger. If there is problem with your waveguide response at 10kHz, it's likely curvature where your waveguide cross section is something around 10kHz in size that makes it, and so on.
If you start thinking with wavelength you'll notice all speakers are roughly midrange in size, so are humans, your television, head, your phone, your sofa, path length difference through early reflections, and so on. 20Hz is about 17m long, while 20kHz is 1.7cm long, so every object inside your room, and your room itself, will have influence on the sound roughly at frequency whose wavelength is about the size of the object, all within bandwidth of audible sound.
Well, heavily simplified, but hopefully gets your imagination rolling, have fun!🙂
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Mitigation of midrange narrowing was first addressed by Keele by adding a second flare to the last third of the horn. This tapered the horn mouth velocity profile in a way that counteracted the beaming.
The dips/plateaus also move closer to on-axis as ka increases.
“If we could smooth out ripply polar curves, we might be able to reduce, or eliminate, the midrange narrowing.”
- Paraphrased and quoted form High-Quality Horn Loudspeaker Systems, Kolbrek & Dunker, 15.4.4, page 577.
It seems that midrange narrowing – waistbanding - has more to do with horn shape than it has to do with round overs.
I profess NO expertise and have far more questions than answers.
The dips/plateaus also move closer to on-axis as ka increases.
“If we could smooth out ripply polar curves, we might be able to reduce, or eliminate, the midrange narrowing.”
- Paraphrased and quoted form High-Quality Horn Loudspeaker Systems, Kolbrek & Dunker, 15.4.4, page 577.
It seems that midrange narrowing – waistbanding - has more to do with horn shape than it has to do with round overs.
I profess NO expertise and have far more questions than answers.
Hi, same thing, any part of horn shape makes diffraction, like the mouth. The mouth and outside of the object is all part of same continuum from diaphragm to all the way 180deg around the device I'd say, beyond that diffracted sound has attenuated so much it likely has not much effect. You can see interference ripple of a ideal transducer on a sphere that sound diffracts all around, but it's so low in amplitude likely has no audible effect. Sound doesn't know when waveguide ends and box starts. So, if features in graphs look exactly like diffraction then to me it's diffraction, which can happen any part of the device (curvature) until rolled over (around) enough.
Rationale is, that waveguide is just a physical object like anything else, so same acoustics apply there as outside the device or with any other object. So, if measurement plot of a waveguide shows same features as would edge diffraction with flat baffle, then it very likely is due to same acoustic phenomenon, like diffraction. It is very unlikely there is some other "property of sound" that is similar to diffraction, but not diffraction, and magically only appears with waveguide in front of the mic 😉
You start to see this after simulating "enough" 🙂
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Thanks to a kind forum member, I had the chance to read the page. However, in the last paragraph of the section, Kolbrek tells the reader more advanced methods are needed, and I assume he is then going to deliver them in the next sections. Yes, something with ka=x.
Yes you are right, @tmuikku, the width of a box that is created around a 10-12 inch woofer easily approaches 34 cm, the 1 kHz region. This is actually the thing that I thought was responsible, the baffle width.
Yes you are right, @tmuikku, the width of a box that is created around a 10-12 inch woofer easily approaches 34 cm, the 1 kHz region. This is actually the thing that I thought was responsible, the baffle width.
^ if you want to remove effect of diffraction backwave at 1kHz, you'd need about that big roundover, radius in order of 1kHz. But, also less is fine, any roundover that starts immediately beside the "transducer" is fine, and gets better the more closely your object resembles a sphere. If your transducer is 34cm in diameter, and your box is 34cm wide, you could fit only 0mm roundover (yeah, none) and it's about as good as 44cm wide box with 5cm roundovers measured with height of main diffraction hump. If your box is about 1m wide with 34cm roundovers, you have significantly reduced diffraction, there is no diffraction hump.
The wider the "box", iow. the bigger the object, the lower in frequecy the narrowing gets and you'd need ever bigger roundover to mitigate. This is the trick, use any roundover, as long as it starts immediately beside the transducer. Well, of course there is some wiggle room to it, things don't change much if you have 1cm of flat baffle around your 34cm diameter transducer, but this is the simplified framework to think about it. The better your object approximates a sphere, the less there is backwave with diffraction. The immediate surrounding of transducer being the most important region, because intensity drops with distance, and diffraction, so while back side of your box also diffracts, it's effect is already reduced into listening window because less sound got to the back edge, than to the front edge before it.
The wider the "box", iow. the bigger the object, the lower in frequecy the narrowing gets and you'd need ever bigger roundover to mitigate. This is the trick, use any roundover, as long as it starts immediately beside the transducer. Well, of course there is some wiggle room to it, things don't change much if you have 1cm of flat baffle around your 34cm diameter transducer, but this is the simplified framework to think about it. The better your object approximates a sphere, the less there is backwave with diffraction. The immediate surrounding of transducer being the most important region, because intensity drops with distance, and diffraction, so while back side of your box also diffracts, it's effect is already reduced into listening window because less sound got to the back edge, than to the front edge before it.
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I don't understand why you keep repeating this. I don't even know what it's supposed to mean, sorry. (Among all those other things.)
Now this is finally getting interesting. Would you mind to elaborate? What is it exactly, that "OS cannot do" and the X-Shape can? I still didn't get it. My "X-Shape" is constructed only with OSSE...
I got some pretty good overall results with an "OS" recently and would like to know what I'm missing, not using a Tritonia (or JBL) variation instead: http://www.at-horns.eu/exar-story.html
BTW, what does the K&D book has to say about this? 🙂😉 (I don't have it so I don't know.)
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Loading capacities comparing to regular OS (nothing exotic a basic one but with full return of course) and staying CD on both axes without mid-range narrowing & beaming and push control higher (not necessary a CD control for some reasons).
X-Shape is born because members of the french 5 (6 since some month) want "everything" and cut very low, some of them are top noch pure Acoustician.
Very exigent and aware of Floyd E. Toole psycko-acoustics studies and room acoustics simulation, DI, etc...
As I said before I don't know how Tritonia is done and what is it precisely, even in JBL line up there is 3 or 4 way to do this kind of horn that cohabit, if you can have the same with your way, it's a great news.
There is other things specially in this kind of form, that JBL miss too, after all you said about me I thinks you will understand that I keep it for me 😉
X-Shape is born because members of the french 5 (6 since some month) want "everything" and cut very low, some of them are top noch pure Acoustician.
Very exigent and aware of Floyd E. Toole psycko-acoustics studies and room acoustics simulation, DI, etc...
As I said before I don't know how Tritonia is done and what is it precisely, even in JBL line up there is 3 or 4 way to do this kind of horn that cohabit, if you can have the same with your way, it's a great news.
There is other things specially in this kind of form, that JBL miss too, after all you said about me I thinks you will understand that I keep it for me 😉
About M2 style ?
The book said nothing, Kolbrek said to me that he would like to study it if he have the opportunity to do but I thinks he have other things to do now.
There is no book about this kind of horn and even more in some book there is "simplification" about loading in horn and throat to mouth conversion that can bring you on the wrong way due to over simplification.
The devil is in the details but the very good point with Kolbrek is that when he simplify, it still true (it's strange what I said but I don't find another way to said it)
The book said nothing, Kolbrek said to me that he would like to study it if he have the opportunity to do but I thinks he have other things to do now.
There is no book about this kind of horn and even more in some book there is "simplification" about loading in horn and throat to mouth conversion that can bring you on the wrong way due to over simplification.
The devil is in the details but the very good point with Kolbrek is that when he simplify, it still true (it's strange what I said but I don't find another way to said it)
The "loading capacities" of the X-Shape are improved only by means of the throat reflection, we are beginning to understand that now. Not as well as with a dedicated extension (http://www.at-horns.eu/exar-story.html) but I give you that it probably does something.
(Which is basically a R-OSSE waveguide with a conical duct attached.)
No, about the EXAR style: http://www.at-horns.eu/exar.html
(Which is basically a R-OSSE waveguide with a conical duct attached.)
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By the way, has anyone met psychoacoustic studies which examined the problem of how people perceive horns with different directivities (narrow vs wide beamwidth, constant directivity vs. narroved etc. ) ?
That's fine, I abandoned that kind of design quite some time ago, as you can see 😉
There's always much more pleasure in spending time on the best one...
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Floyd E. Toole psycko-acoustics studies, there is book and it's not something news in fact.
Absolutely not the case 😉
About EXAR, mmh I don't remember, it's more related to compression driver phase plug with path and all of this but you already know it so...
Look last Dario Cinanni work may be
I think that to show that you actually know what you're talking about, you would have to provide your explanation, if you have some.
Let's be honest, those are the best devices you ever saw - I know it's a pain, the more so as it was almost an accident, but face the reality 😉
They are better than any "X-Shape". I can say it, as I made those as well.
That's why I asked what can an X-Shape offer that those can't. Seems there's no such thing, right. Just to be clear on that.
I give you a part of the answer, you cannot ask me for help and insulting me or/and my product at the same time.
I have respect for your works but why you suddenly want to create a competition between X-Shape and EXAR ?
I just discover that you put a name on it (EXAR), last time I just see a pdf, the first one I guess, years ago. So great evolution I guess.
If both perform well there is no problem at all and it's great for both of us and I don't have an EXAR in my hand or to put in my FEA system.
I have respect for your works but why you suddenly want to create a competition between X-Shape and EXAR ?
I just discover that you put a name on it (EXAR), last time I just see a pdf, the first one I guess, years ago. So great evolution I guess.
If both perform well there is no problem at all and it's great for both of us and I don't have an EXAR in my hand or to put in my FEA system.
As far as I know, Floyd Toole performed general studies on directivity rather that performed deeper investigation of different horns.