Acoustic Horn Design – The Easy Way (Ath4)

[mabat]

I haven't figured out how to attach the short adapter yet

You need four threaded rods or long bolts, going through the whole adapter, to attach the driver.

 

[olegtern]

You need four threaded rods or long bolts, going through the whole adapter, to attach the driver.

Thnx, already bought them 15 minutes ago))

there must be a leakage somewhere.

Hmm, ok, I’ll try to look for, although doubt.

 

[mabat]

Just trying to explain what we see, because it's really strange...

 

[olegtern]

Just trying to explain what we see, because it's really strange...

Sure, I'm wondering what's going too🙂

I put a layer of double-sided tape between the long adapter and the horn, on the driver's side there is a small layer of sealing rubber - it can be considered airtight. The curve has not changed.

 

[mabat]

Does the long adapter hold water (I mean literally)? 🙂

 

[jzagaja]

Do you know dfm-2535r00-08 throat angle? In Exar documentation 6deg was used (full angle) - this result 57mm adapter length for A520G2. After changing to 3deg half angle length is 108mm.

 

[mabat]

I don't know the exact value but it can be like 15° full angle. Certainly more than 6°.
The T520-25-STD-1 should be definitely a good-enough match. But so is the 6° in the original EXAR 400-25, so what do we know...

 

[jzagaja]

I just fear I've lost loading so better keep 6deg full angle and 108mm long adapter.

 

[mabat]

Yes, it will decrease considerably with a wide-open throat.

 

[DCDK]

and because it is unachievable with a big woofer and horn, this rule can be omitted alltogether.

@DCDK, there was a long discussion over this, started by Vituixcad creator Kimmo Saunisto. He suggested to use a center to center distance of 1.1-1.3 lambda of the crossover frequency. This results in quite a spread. The ratio behind this is the following: below the downward directed vertical null of the two-way system, the lobe again begins to sum positively. Due to this, the dip in the power response that is usually resulting from the two-way crossover is mitigated. From my own experiments, I never was quite sure if I could sense, in some cases, that i.e. bass notes where coming from the woofer and the voices from the horn. In any case, the tallness of the image improved. I suggest that you use simulation data in VCad and build a cheap prototype to confirm whether your design choice actually works perceptually.

I found Kimmo's post about the center-to-center distance of 1.0-1.4 times the XO wavelength here (with a 1.2x example further down the page):

https://www.diyaudio.com/forums/software-tools/307910-vituixcad-post6541438.html

For my design, the center-to-center distance should be 66 cm, which is easily achievable. I'll try to simulate the setup in VituixCAD before ordering the drivers.

 

[olegtern]

Does the long adapter hold water (I mean literally)? 🙂

Ok, I tried it - the adapter doesn't leak, literally! 🙂

I'm still not promising that I've done everything perfectly (I sometimes go back to check if I've locked the door when I leave the house)), but I've tried everything and it doesn't seem to be my fault, but that's how it works with my driver. I guess I'll have to wait for someone else to test it.

 

[GQZ]

View attachment 1314126

Hello everyone,

Was wondering if anyone could share a link for generating the above graph, tks. I know VitrixCAD2 can plot it but was wondering if there are other alternatives.

Much appreciate

GQZ

 

[mabat]

For this particular graph, polar data are extracted from ABEC output, processed by Ath and corresponding plain-text files generated for gnuplot.
This is all done automatically with the latest Ath version (includes a gnuplot script) - to run ath.exe you would need a key file that's included in the Cults packages for A520G2/A400G2, but you can use the provided gnuplot script right away.

 

[GQZ]

Thank you Mabat, I will give it a try =)

 

[TNT]

provided gnuplot script

Where can I find this?

//

 

[mabat]

the latest Ath version (includes a gnuplot script)

Then in an Ath script set:

Report = {
  ...
  PolarDataV = <your_vertical_polar_data>  ;  "SPL" by default for an axisymmetric horn
  GnuplotCode = cea-std.gpl
}

I only think that full 0 - 180 deg polars must be calculated for this to work, 10deg step should be enough, I keep 5 by default. Basically, all the polars that are required by the CEA2034 must be directly available:

ABEC.Polars:SPL = {
  MapAngleRange = 0,180,37   ; start_angle, end_angle, no. of polars
  ...
}

I'm not sure if this works with the older version(s) of Ath. At some point I added this but don't remember when. It's nothing that would be impossible to live without but people seem to like it 🙂

 

[mabat]

BTW, I sent Oleg another 36mm EXT adapter for the A520G2, closer to a straight tube. I'm really curious how it turns out.
- If anyone wanted to participate in the development efforts of these things at this point (adapters for particular drivers, etc.), you are of course invited.

 

[mabat]

Culmination of a several-years work, EXAR 520G2 on its way.
Still the same throat adapters (T520*) used. Six and nine-petal versions will be made I think.

With the standard 1.4" throat:

 

[TNT]

Can we hope to see real measurements of the A520/rosso-std combo? Would be very interesting 🙂 .

//

 

[mabat]

I only today assembled the A520G2.
And even though I already know exactly what to do, it's still a bit of a challenge.
But it doesn't take long once you start. You simply finish the circle and let it dry.