Acoustic Horn Design – The Easy Way (Ath4)

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#12,525
Yeah, especially in the smaller studio monitors, that's almost a standard now. Maybe still not so much in home hi-fi, but that was always all over the place...

- I just wanted to see what beamwidth I'm able to get with an "ordinary" waveguide, as the Purify Audio guys showed +-70deg up to 20kHz recently, which is really not common...
 
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#12,526
Any idea what I may be doing wrong? I'm using the latest build for ATH. I'm literally running the exact code included in the following post: 9,879

However, for me, the LF driver is not showing up in ABEC (See picture below) ? Is there something I need to enable to view in ABEC?

Apologies for the newbie questions I'll be (*have been) asking. I left this thread a while ago and its exploded since then 🙂 (in a good way, of course). So many new features.

My near-term goal is to simulate a waveguide for the Peerless DA25TX with an 8" driver (like the Dayton Audio RS225-8).

The following is the code I'm starting with. Please note - there are many features I don't understand:

; ATH-DOME Template
; -------------------------------------------------------

; Peerless DA25TX00-08

OSSE = {
r0 = 16
a0 = 40
k = 0.7
a = 55
L = 26
s = 1.27
n = 2.15
q = 0.996
}

Source.Contours = {
dome WG0 26 5.6 3 1.5 4 1
}

Source.Velocity = 2 ; axial motion

Mesh.Enclosure = {
Spacing = 90,70,90,350
Depth = 200
EdgeRadius = 35 ; 25
EdgeType = 1
FrontResolution = 8,8,16,16
BackResolution = 20,20,20,20

LFSource.Below = {
Spacing = 10
Radius = 82
DrivingWeight = 1
SID = 1
}
}

Mesh.VerticalOffset = 80

Mesh.Quadrants = 14 ; =14 for 1/2 symmetry

Mesh.LengthSegments = 24
Mesh.AngularSegments = 64
Mesh.ThroatResolution = 3
Mesh.MouthResolution = 9
Mesh.SubdomainSlices =

Mesh.ZMapPoints = 0.3,0.2,0.7,0.9

;Mesh.InterfaceResolution = 6
;Mesh.RearResolution = 20

; -------------------------------------------------------

ABEC.SimType = 2
ABEC.MeshFrequency = 1000 ; [Hz]
ABEC.NumFrequencies = 40
ABEC.f1 = 1500 ; [Hz]
ABEC.f2 = 20000 ; [Hz]

ABEC.Polars:SPL = {
MapAngleRange = 0,90,10
Distance = 2 ; [m]
NormAngle = 0
}

; -------------------------------------------------------

Report = {
Title = "ATH-DOME"
NormAngle = 10
Width = 1400
Height = 900
}

Output.STL = 0
Output.ABECProject = 1
 

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#12,528
mabat said:
Change "Below" to "B". That's my bad, I don't know why I changed that.
Click to expand...

And that did it! Thank you, @mabat! Can I ask a few questions (pertaining to code I could find in the manual):

1) What does "SID = 1" mean under LFSource?

2) For dome geometry, what do numbers represent?
For example dome WG0 26 5.6 3 1.5 4 1 <<-- so 26mm is the dome diameter?, 5.6mm is the dome height? 3mm is the surround width? and I have no clue what 1.3 4 1 represents. I'm not even sure I got the first three numbers right. I figured the 26mm + 2 x 3mm surround width = 32mm overall diameter, and thus I selected waveguide mouth radius to be 16mm.

3) What does "Mesh.InterfaceResolution =" represent?

4) What does "Mesh.VerticalOffset =" represent?

I tried to look up some of the items above in the manual, but I realize (and understand) that the application is developing at a faster speed and that obviously poses a challenge to keep updating the manual
 
#12,531
That can be difficult 🙂
I'm still trying to find out the actual shape of the surround of T34B (concave/convex) and there's so much conflicting information that I think I will have to buy me a pair to check it myself...

- Fortunately it seems that the surround itself doesn't make a night and day difference. It's really the dome shape that has a profound effect at HFs.
 
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#12,534
fluid said:
The simulation conditions seem to matter much more than I found previously.
Click to expand...
Yes, that's why I haven't shared an IB script at all - it's really not much helpful with these designs.

Free-standing axisymmetric (R-OSSE) can be pretty close to a rounded enclosure though - it can save quite a lot of time during iterations. Baffle-mounted version (OSSE) can then be derived from that.
 
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#12,539
Apologies if this has been asked before and/or if the answer is obvious, but cannot easily find answer to following (and it is not obvious to me):

  • A concave shaped horn (like JBL's have) helps with increasing sound pressure for certain frequencies and helps with making directivity more constant - correct? Most waveguides (shallow or deep) seem to use the concave shape.
  • What is the effect of a convex shaped waveguide vs a concave one? For example Neumann's KH420 seems to use convex shaped waveguides for tweeter and mid domes. How does this effect pressure and / or directivity?
 
#12,540
I think all waveguides and horns are actually convex (concave would be e.g. a parabolic shape - a disaster as a horn). Maybe you mean something else, but I don't see what it is... Can you show an example of what you mean exactly?

- BTW, I think this pretty much makes all the smaller tweeters obsolete...
Why would anyone use a smaller tweeter now? Certainly not for a wider radiation pattern any more. A smoother response/even higher breakup perhaps, but these 34mm tweeters are already so good that I doubt that it would have a merit.
 
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