JBL 2450, TD-4001, perhaps the DAS drivers mentioned? (I have no familiarity with the DAS drivers) In my long experience here Marco and Docali as well as a few others have considerable expertise in this area and based on my own experience with the A-290, TAD-4001, Radian NEO 950PB and JBL 2440/2441 I find them extremely credible, I would say the same for Profiguy as well.
I have made some expensive missteps which I have shared widely so that others may learn from my audio misfortunes. 😆 I am the OP and most of the story is here. I certainly don't recommend you follow in my footsteps, it is a very costly way to learn. The 745 Be is at least a good driver and there is a market for good used ones - the 950 is another matter, it has problems beyond the path length and exit angle. (There is a big step in the path..) Really don't buy a 950 even with a Be diaphragm - it will never rank as one of the greats, I am not convinced it is even good. I bought them on the recommendation (in print) of someone I once worked with and I will never do that again. (No doubt great in PA in line arrays and the like)
I have made some expensive missteps which I have shared widely so that others may learn from my audio misfortunes. 😆 I am the OP and most of the story is here. I certainly don't recommend you follow in my footsteps, it is a very costly way to learn. The 745 Be is at least a good driver and there is a market for good used ones - the 950 is another matter, it has problems beyond the path length and exit angle. (There is a big step in the path..) Really don't buy a 950 even with a Be diaphragm - it will never rank as one of the greats, I am not convinced it is even good. I bought them on the recommendation (in print) of someone I once worked with and I will never do that again. (No doubt great in PA in line arrays and the like)
You misunderstood that (or perhaps I wasn't clear enough). I meant, there are better alternative drivers to the Radian 745, to be used with the TH-4001 horn.
What I do not like with these Radian drivers is that the screws of the back cap at the same time align the diaphragm. So do not open the back if your are unsure to re-align the driver.
Personally, I prefer the 18sound ND3 series if it comes to to a 3in VC. I can recommend the nitride coated versions ND3N and ND3SN. Later on it is possible to upgrade to Be. These drivers are better than ND1480x because they have a better designed pp.
Personally I would also not use TH4001 and Yuichi anymore as it has been shown that these are obsolete designs. The mk3b2 surpass them.
But here my just 2 cents. I would not use fin horns anymore except you need such a broad dispersion. They cause more problems than they solve in a normal listening environment. And as it has been shown with my coherent fin horn, all traditional fin horns have issues as they are not iso phase after the fins.
When oltos mentioned it recently I began working on a way to show the effect of pinching an adapter. It's often said that a diffraction slot is problematic.
What is less often said is that a reduction in area preceding it causes reflected higher order modes.
In addition to this there can be axial reflections.
What is less often said is that a reduction in area preceding it causes reflected higher order modes.
In addition to this there can be axial reflections.
Unfortunately, Hyp/Ex is not a one parameter expansion per the Webster plane-wave approximation.
Do you feel continuation is a requirement, and does better loading just mean you need to stay away from cutoff?
What of the higher frequencies?
Do you feel continuation is a requirement, and does better loading just mean you need to stay away from cutoff?
What of the higher frequencies?
If or if not a function is one parameter wrt Webster eq. is irrelevant. You can do everything what you prefer and like.
What it means is that there will be a margin of error. This tends to be reconciled in diffraction. This is before considering the affects of asymmetry.
Stalling expansion rate in just one plane alone can have negative consequences, leading to impedance related reflections unless you significantly increase expansion rate simultaneously in the other planes to compensate. This is the case with many planar wave guides used in narrow vertical directivity designs ie. HF elements in line arrays.
In many high directivity applications, there is a distinct tendency for the transition point right at the WG entrance to produce an impedance related reflection. This will often lead to a resonance or at minimum a longer decay trail at a given frequency in the CSD. Any parallel walls inside the throat will be susceptible to standing wave resonances. At a minimum, compromises like this will lead to poor transient response, especially at higher compression ratios.
The A290 throat is designed to feed the individual horizontal sectors with a flat plane of pressure waves up until the adapter exit point, where it expands to follow the horn curvature.
I believe there is some amount of diffraction or drag involved in making the wave front at the WG entrance point expand and curve evenly to remain perpendicular to the outer main WG walls. Having the main WG profile split into separate smaller sectors solves several potential issues. It allows for a minimal vertical wall expansion rate without the risk of inducing reflections and improves HF dispersion uniformity. The necessary rapid shift in horizontal expansion rate is only made possible by the throat adapter profile. This is a rather complicated shape which appears to be a product of much trial and error when it was designed.
If the adapter doesn't line up just right at the WG entrance and retain the sidewall shape it will produce reflections and other artifacts. The adapters which came with my A290s didn't line up well with the WG entrance. There was at least a 1/16" mismatch in shape in both planes. Even if the driver exit angle were appropriately chosen, the adapter discrepancy would have significant hurt performance virtually everywhere in the curve. I confirmed this by using modeling clay to smooth out the transition, which improved performance everywhere, especially below mass rolloff. This was with a B&C DCX50 driver.
A chosen driver for this WG would have to be suitable for a slower expansion rate after the phase plug. A low exit angle would definitely be more suitable, rendering a shallow, shorter driver exit wall profile a poor choice.
A planar wave front is necessary with the A290 WG to get the best performance from it. The adapter mismatch is an additional issue which is much harder to solve, requiring a complete redesign of the adapter IMO. I would venture to bet a short 1.4 to 2" adapter with a decent, low exit angle driver would be more suitable for this WG. It would open up more choices for compatible drivers and the smaller WG throat would improve HF extension.
In many high directivity applications, there is a distinct tendency for the transition point right at the WG entrance to produce an impedance related reflection. This will often lead to a resonance or at minimum a longer decay trail at a given frequency in the CSD. Any parallel walls inside the throat will be susceptible to standing wave resonances. At a minimum, compromises like this will lead to poor transient response, especially at higher compression ratios.
The A290 throat is designed to feed the individual horizontal sectors with a flat plane of pressure waves up until the adapter exit point, where it expands to follow the horn curvature.
I believe there is some amount of diffraction or drag involved in making the wave front at the WG entrance point expand and curve evenly to remain perpendicular to the outer main WG walls. Having the main WG profile split into separate smaller sectors solves several potential issues. It allows for a minimal vertical wall expansion rate without the risk of inducing reflections and improves HF dispersion uniformity. The necessary rapid shift in horizontal expansion rate is only made possible by the throat adapter profile. This is a rather complicated shape which appears to be a product of much trial and error when it was designed.
If the adapter doesn't line up just right at the WG entrance and retain the sidewall shape it will produce reflections and other artifacts. The adapters which came with my A290s didn't line up well with the WG entrance. There was at least a 1/16" mismatch in shape in both planes. Even if the driver exit angle were appropriately chosen, the adapter discrepancy would have significant hurt performance virtually everywhere in the curve. I confirmed this by using modeling clay to smooth out the transition, which improved performance everywhere, especially below mass rolloff. This was with a B&C DCX50 driver.
A chosen driver for this WG would have to be suitable for a slower expansion rate after the phase plug. A low exit angle would definitely be more suitable, rendering a shallow, shorter driver exit wall profile a poor choice.
A planar wave front is necessary with the A290 WG to get the best performance from it. The adapter mismatch is an additional issue which is much harder to solve, requiring a complete redesign of the adapter IMO. I would venture to bet a short 1.4 to 2" adapter with a decent, low exit angle driver would be more suitable for this WG. It would open up more choices for compatible drivers and the smaller WG throat would improve HF extension.
As this changes the cross sectional shape, the wavefront stretching is likely to be felt by anything not too large to be controlled in directivity by it. This plays into my earlier comment on 1P behaviour, since even axisymmetric expansion will have increasing local effects at those frequencies.
FWIW, oblate spheroidal stalls it's expansion as it follows the wavefront.
An ideal plane wave tube shows no standing waves or transverse modes when guiding a plane wave.
If a driver is designed to present a plane wave, parallel walls would be an appropriate choice.
@AllenB The expansion rate I referred to was before the horn entrance, where the plane wave front is reshaped to suit the horn profile.
After that area, the system becomes less sensitive to any abnormalities. Same holds true for paralleled walls, when they usually are encountered in diffraction areas. As long as the wave front inside the given throat section remains uniform, it won't provoke standing waves or other reflections. Any disturbances in the uniform progression of pressure waves in that area, you'll encounter problems. Once the expansion in the horn occurs and as long as the wave front remains somewhat perpendicular with the outer WG wall, it won't be as sensitive to smaller discrepancies in WG geometry.
Usually the initial entrance angle to the WG will define the net radiation angle at the mouth. That is after the throat transition just before the WG entrance, after any initial diffraction points, but the whole beginning area of the entire WG including the driver exit area can become a combined system, producing other wanted and unwanted radiation features.
Drag can contribute to slowing or stalling the outer pressure gradients to create a wider radiation angle at the mouth, but it comes at the expense of increased HF rolloff and some minor combing effects. Its often used to lessen the WG's susceptibility to unwanted diffraction after the WG exit ie. at the enclosure baffle edges. It can be tamed with acoustic absorption (foam) at the WG mouth edges.
After that area, the system becomes less sensitive to any abnormalities. Same holds true for paralleled walls, when they usually are encountered in diffraction areas. As long as the wave front inside the given throat section remains uniform, it won't provoke standing waves or other reflections. Any disturbances in the uniform progression of pressure waves in that area, you'll encounter problems. Once the expansion in the horn occurs and as long as the wave front remains somewhat perpendicular with the outer WG wall, it won't be as sensitive to smaller discrepancies in WG geometry.
Usually the initial entrance angle to the WG will define the net radiation angle at the mouth. That is after the throat transition just before the WG entrance, after any initial diffraction points, but the whole beginning area of the entire WG including the driver exit area can become a combined system, producing other wanted and unwanted radiation features.
Drag can contribute to slowing or stalling the outer pressure gradients to create a wider radiation angle at the mouth, but it comes at the expense of increased HF rolloff and some minor combing effects. Its often used to lessen the WG's susceptibility to unwanted diffraction after the WG exit ie. at the enclosure baffle edges. It can be tamed with acoustic absorption (foam) at the WG mouth edges.
It is shown here that notwithstanding the vanes, the overall horizontal situation is conical like. The expansion will not do anything to turn a plane wave into a radial one before the vanes begin, other than what naturally develops over that small distance.
Unless you use a multicell adapter, you have to take it as a whole, even though the vanes cause the total included angle to be less.
I've drawn the horizontal expansion without the vanes, showing their combined effect.
The consensus here is that I cut my losses and try to sell the Radian 745Bes. I also have a pair of undrilled Azurahorn AH425s; perhaps I someone here would be interested in both.
https://www.usaudiomart.com/ In any case, if I'm lucky enough to sell them it will probably be at a big loss.
Docali recommends 18Sound's ND3 series but there is only one from those with the beryllium diaphragm. https://www.eighteensound.it/en/products/hf-driver/1-4/8/ND3BE Yes, or no??
Alternately, Marco recommends the JBL2450J 16 ohm. https://www.usspeaker.com/jbl 2450H-1.htm But the cost of a pair of those plus these Beryllium diaphragms are obscene.
https://radianaudio.com/products/1245-diaphragm
Since Docali's nor I believe Camplo's horns are available for purchase, that seems to leave only two: Troy Crowe's ES450 or his larger (and probably unaffordable) ES290s. They are finless, but as Camplo pointed out they are don't display a "You are There" sound.
That leaves the TH4001, which as Athos said is available with and without fins, but does the JBL2450J and/or the 18Sound ND3Be require fins?
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And since DIYed adapters are clearly verboten here, the JBL2450J/TH4001 "You are There" combo looks like
the one to beat. But fins or no fins for the 4001?
the one to beat. But fins or no fins for the 4001?
Hi, in my experience this perception highly depends on the room and positioning and all stuff, not just a horn. While the horn could ruin it, it's eventually feature of auditory system that makes perception happen so perhaps it just needs better positioning, better crossover, different room acoustics and so on. This stuff cannot be associated to any one particular thing in that sense, except to our auditory system. I mean, even if the horn was good, some other feature in the system, like bad positioning, could prevent this from happening.
I have no such horn, but with system I have I can swap between "you are there" and "they are here" perception just by changing listening distance a bit, the perception depends on which state your brain is at not about the playback equipment per se. It's difference whether brain pays attention to direct sound or not, see Griesinger Limit Of Localization Distance. Features of both perceptions depend on positioning and room acoustics, directivity of course.
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I can only proceed by what I've been told by Camplo and Pierre-and the latter definitely found a "They are Here" and "You are There" presentation from the JMLC AH425 and TH4001 horns, respectively, in the same room, and presumably using similar placement. And Camplo's evaluation of directivity plots for the Crowe ES450 essentially puts that horn in the "They are Here" camp. So, how could I go wrong with the 4001 horn?
But I need Marco or someone to advise me on a fin or finless version for a given driver.
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Hi, I don't know. The horn seems outdated design in sense that better measuring ones can be made just like that. Point is, while it is likely still good sounding one it's not only option in the world. It is a classic and good looking piece of kit so why not, lot's of nostalgia which also affects how sound is perceived, the feeling of the system. What kind of listening space you have? size and acoustics?
You could try and estimate whether the "you are there" perception happens in your place with system you are planning, and perhaps even guess how big of a listening triangle it could happen. The thing is, I speculate the "You are there" happens with almost any room and with almost any playback system, as long as speakers are not the worst implementation and room something sensible, like regular living room, and listening triangle is small enough compared to acoustics and speaker directivity so that loud early reflections do not ruin it.
What could ruin it, is the listening triangle gets so small that you speakers are too big and you'd be in nearfield of the speaker. But this is all speculation from reasoning on the stuff so not necessarily the truth for all situations, which is why I try and encourage people test and comment about this stuff. I have only one set of speakers and get "you are there" about 2m distance from ear to speaker, after which perception changes to "they are here". This is with cardioidish ~constant directivity system, DI goes from 6-10db from 300-20kHz and it's a regular livingroom with normal furnishing, without any special acoustic treatment. The max distance where this transition happens have been pretty much similar on all 5 regular living rooms I've had the speakers in, friends houses.
While change in perception could be from anything, Griesinger LLD describes the perception pretty much perfectly so I think it's that, brain switching state, and it's due to well enough preserved phase of the sound, which makes great enough signal to noise ratio as if the sound is close for brain to lock into an important sound. I do not know how far in your room your speakers could make it. Small bookshelves it would be smaller I bet, bigger higher DI system it's likely bit farther, just due to directivity and how early reflections contribute to the phenomenon. It is not phenomenon for speakers, but phenomenon of auditory system and happens with any sounds in any environment, brain locks on to important sounds that are close enough to you, which are either a friend talking to you or possible threat, like a wolf in the bush, and brain pays involuntary attention to these, heightens their presence in your perception because they are important for survival. Conversely, brain prevents your attention of sounds that are not important, that are far away or noisy, as they would prevent you focusing on the important stuff. You'd still perceive them of course, they just don't have any details or sharp localization and do not go directly into memory for example, are not enjoying that much resources of your auditory system.
If you have any speakers right now with you, try and get the you are there sound by making small listening triangle, and experiment with it.
You could try and estimate whether the "you are there" perception happens in your place with system you are planning, and perhaps even guess how big of a listening triangle it could happen. The thing is, I speculate the "You are there" happens with almost any room and with almost any playback system, as long as speakers are not the worst implementation and room something sensible, like regular living room, and listening triangle is small enough compared to acoustics and speaker directivity so that loud early reflections do not ruin it.
What could ruin it, is the listening triangle gets so small that you speakers are too big and you'd be in nearfield of the speaker. But this is all speculation from reasoning on the stuff so not necessarily the truth for all situations, which is why I try and encourage people test and comment about this stuff. I have only one set of speakers and get "you are there" about 2m distance from ear to speaker, after which perception changes to "they are here". This is with cardioidish ~constant directivity system, DI goes from 6-10db from 300-20kHz and it's a regular livingroom with normal furnishing, without any special acoustic treatment. The max distance where this transition happens have been pretty much similar on all 5 regular living rooms I've had the speakers in, friends houses.
While change in perception could be from anything, Griesinger LLD describes the perception pretty much perfectly so I think it's that, brain switching state, and it's due to well enough preserved phase of the sound, which makes great enough signal to noise ratio as if the sound is close for brain to lock into an important sound. I do not know how far in your room your speakers could make it. Small bookshelves it would be smaller I bet, bigger higher DI system it's likely bit farther, just due to directivity and how early reflections contribute to the phenomenon. It is not phenomenon for speakers, but phenomenon of auditory system and happens with any sounds in any environment, brain locks on to important sounds that are close enough to you, which are either a friend talking to you or possible threat, like a wolf in the bush, and brain pays involuntary attention to these, heightens their presence in your perception because they are important for survival. Conversely, brain prevents your attention of sounds that are not important, that are far away or noisy, as they would prevent you focusing on the important stuff. You'd still perceive them of course, they just don't have any details or sharp localization and do not go directly into memory for example, are not enjoying that much resources of your auditory system.
If you have any speakers right now with you, try and get the you are there sound by making small listening triangle, and experiment with it.
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Used 2450J drivers are widely available at affordable prices. Then you "just" have to splash for the Be diaphragms.
And, there's no such thing as a legit TH-4001 horn without fins. The latter are integral to the design, and required to achive the design expansion rate.
I personally prefer fin-less horns. But, properly designed ones! Not butchered TH-4001's!
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Also: Troy's horns are excellent, imho.
But, the ES450 is ACOUSTICALLY too small to be crossed over at 500 or even 600 Hz without issues (800 or 900Hz is more like it).
The ES290 is required if you target such a low crossover point.
A big part of the reason why Troy's horns are PHYSICALLY so large (compared to others with a similar cutoff) is that they sport a full mouth roll-back, to address and minimise edge diffraction. That is a good thing, but it makes, e.g., an ES290 significantly larger than an Arai A290, even though both are acoustically pretty much the same.
But, the ES450 is ACOUSTICALLY too small to be crossed over at 500 or even 600 Hz without issues (800 or 900Hz is more like it).
The ES290 is required if you target such a low crossover point.
A big part of the reason why Troy's horns are PHYSICALLY so large (compared to others with a similar cutoff) is that they sport a full mouth roll-back, to address and minimise edge diffraction. That is a good thing, but it makes, e.g., an ES290 significantly larger than an Arai A290, even though both are acoustically pretty much the same.