Take the Eighteensound ND4015BE review from voice coil mag as an excellent example.
1,5" exit compression driver, 4"dia. BE diaphragm.
Mated to the XR2064 2" horn.
Noted in the article the ND4015 2" version was tested, which does not exist and never did.
What exists is a couple optional external throat adapters, that was not designed to fit the ND4015.
It is very easy to see the issue resulting from the mismatch between throat adapter and driver from 10K and up.
https://en.toutlehautparleur.com/adaptor-for-compression-driver-1-5-inch-to-2-0-inch.html
Compare that to Docali's review" found here:
https://sphericalhorns.net/2023/07/15/drba-test-bench-eighteen-sound-nd4015be/
So Voice coil mag. should be taken with a grain of salt at times.
Not sure what Vance Dickason is up to, clearly there is huge room for improvement in some of his testing and declarations of what he does.
The Yuichi initial expansion is very similar to the Smith DSH ("distributed source horn"), an approximation of an exponential expansion.
The Yuichi used a hypex (hyperbolic-exponential) in the throat, very little difference.
Putting a 60 degree angle exit driver on a horn designed for drivers using ~1/3 that angle both increases the Fc and causes a throat reflection, bad for response.
The Radian spec sheet says as much:
Doing the opposite, long "old school" ~15 degree driver exit coupled to a wider throat expansion does not make such gross problems appear in the response, especially if the transition area is smooth.
Perhaps something like OS.
There may be a good bit of finger wagging at horns or drivers for their faults, when in fact they are simply not well matched to the device they are used with.
OS is not a smooth continuation to a cone. Cone has zero curvature, whereas OS has the highest curvature right at its start.
For a driver like the 2" Radian above, it should be the best simply to start the horn/waveguide at the exit of the phase plug and continue with a smooth curve from there, all the way to mouth. Or, make an intentional curvature change and add a resonance that helps to increase the efficiency.
For a driver like the 2" Radian above, it should be the best simply to start the horn/waveguide at the exit of the phase plug and continue with a smooth curve from there, all the way to mouth. Or, make an intentional curvature change and add a resonance that helps to increase the efficiency.
A "fast expanding" waveguide as Mabat described
In other words, don't use the Radian 760NeoPB on any typical exponential-type horn, which have a low expansion rate commensurate with a low Fc.
And it's recommended "minimum crossover frequency of 800Hz using a 24dB/octave crossover, higher with lower filter rates" is another indication that it is not designed for horns like the 290Hz Fc Yuichi.
Conical is the perfect continuation of spherical of the same angle.
The graph you mention shows a plane wave into conical.. These days we would use OS instead. In between, as you model OS with intermediate angles of driving wavefront, it becomes closer to conical.
Are you not using horn theory to describe something that was designed using waveguide theory? ..and do you see both happening and where is the split?
- Lifted from this thread Radian 950 throat, Is This Right???Berd said:
Allow me to circle back to this fact.
I'm pretty confident that "kevinkr" would still be using his Radian 950's along with his Yuichi's if his Radian 950's were of the original design type.
FWIW, the designer of that driver is a member here ( though hasn't been around for a number of years ). Seems he did the design work about 25 years ago.
It's pretty clear to me that Radian has been changing up ( cheapening ) their product line ( all the while denying it ).
That's really the "Ground-Zero" of Kevin getting hosed and then wondering about his un-expected results.
I describe the reality: https://www.diyaudio.com/community/...-design-the-easy-way-ath4.338806/post-6248583
A suitable device for a wide-open conical exit would be (e.g.) one of my profiles with k=0, basically a conical throat with a very smoothly rising curvature:
https://www.desmos.com/calculator/jju41ayesq
Yes, it's the 950 factory throat adapter.
It's a 951 with a adapter mounted to it.
Means one can produce 1 driver, fit a adapter, then you have 2 'separate' products while having to manufacture 1, and a adapter. Makes for easy profit.
Radian cutting corners is nothing new, you will find posts on lack of internal fit/finish and assembly around the web.
Like they're 5 slit phasing plug, has not always been very well made and finished.
It is also one of the only "premium priced" compression drivers that does not have any form of copper in the gap.
Visible from the impedance traces.
Lets you get away with a less powerful magnet etc.
Does make sense in the form of saving money on manufacturing, and boosting profits.
Not really makes sense on a "premium" BE diaphragm driver supposed to cover the top octave.