Acoustic Horn Design – The Easy Way (Ath4)

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#6,881
From what I can see, the old config files no longer work in ATH 4.7.1?

The new config files features this format:

ABEC.Polars:SPL = {
MapAngleRange = 0,90,19
NormAngle = 10 ; [deg]
Distance = 3 ; [m]
Offset = 95 ; [mm]
}

But there's no apparrent way to generate polars on the X and the Y axis?

When I include a stanza like this, it doesn't work. (It used to.)

ABEC.Polars.Dist = 2 ; [m]
ABEC.Polars.Step = 7.5 ; [deg]
ABEC.Polars.Points = 8
ABEC.Polars.Horizontal = 1
ABEC.Polars.Vertical = 1
ABEC.Polars.Diagonal = 0
ABEC.Polars.DiagonalInclination = 0.0
 
#6,882
mabat said:
Remember this was a coaxial compression driver. This is about as good as it gets for that kind of device. ...
Click to expand...
I think this was how the simulation worked out -
 

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#6,883
Patrick Bateman said:
...

But there's no apparrent way to generate polars on the X and the Y axis?
Click to expand...
Yes, sorry about that. You have to set an inclination angle for anything else than the horizontal. It's missing in the manual:

ABEC.Polars:SPL_V = {
MapAngleRange = 0,90,19
NormAngle = 10 ; [deg]
Distance = 3 ; [m]
Offset = 95 ; [mm]
Inclination = 90 ; [deg]
}
 
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#6,886
gedlee said:
I don't believe that this is correct.

If there is a reflection at the mouth that causes a standing wave inside of the device, then these resonances will be as constant throughout the sound field as a resonance in the driver itself.
Click to expand...

Dear Mr. Geddes, the horn previously didn't had the rollback on the mouth. With this version I had the problem with a reflection (i guess it was a reflection) on the axis up to about 20 degrees. From 20 degrees and more it comes to a peak. So the gain on axis and 30 degrees out of axis were nearly the same. And I also had the problem with the box behind the horn. The rollback version is much more tolerant of what is behind the horn. I have to say, that the horn without the rollback was a 90 degrees design. First i tried to eliminate the reflexion with different damping materials on the mouth and also on the cab behind. The result was clearly bether but not to handle for professional use.
 
#6,887
tmuikku said:
isitone, Very nice! did you turn it manually with some jig/template? I mean it is pretty accurate work, the measurements are really good.

May I ask how many hours of work went into it and how much experience is needed to achieve such piece? One of my relatives has suitable lathe but I don't have very high hopes turning one yet since I don't have experience and the owner is not into audio nor precision 😀 It could be nice if you gave a quick summary what it takes to turn such horn at home? Thanks!
Click to expand...

Dear Mr. tmuikku, yes, I have a template for the profile. In my first profession i was carpenter and i have e little bit the feeling for woodworking. But if you watch some videos how to work it with a lathe you will find the way fast and easy. I will you give the courage to try it.
 
#6,888
The ripples / resonances are likely - at least to some extent, inherent to the DCX464's design, probably due to interference from the HF diaphragm and the exit channel.
The ripples (> 8k) are at least present in the plots I've seen from the DCX464.
Perhaps Mark(100) has some measurement data for comparison.
 
#6,890
Ro808 said:
The ripples / resonances are likely - at least to some extent, inherent to the DCX464's design, probably due to interference from the HF diaphragm and the exit channel.
The ripples (> 8k) are at least present in the plots I've seen from the DCX464.
Perhaps Mark(100) has some measurement data for comparison.
Click to expand...

Hi Ro,

I posted this some time ago in the dcx464 thread...so nothing new.
When i saw the lack of coherence in it at above 16kHz, I thought i'd grab some new outdoor measurements this morning as there is no wind today...but not to be...boats, waves on shore etc....coherence fell everywhere.

Anyway, it's the dcx464 on xt1464 which is the best behaved horn i have.


Hey, a question for all:

How do you like to see polars in these type mag vs freg graphs?

Do you EQ on-axis (or whatever near to on-axis angle is chosen to tune to), and then measure polars?
This is what I like and is in graph below.

Or do you measure raw and show raw?
I use this for choosing xover points, but find it too difficult to judge horn performance, trying to see if ripples are uniform across angles.

Or do you prefer to measure raw, then show normalized to on-axis?
(Have to admit, this is my least favorite to see)

Thanks ! mark

464 on 1464 horiz 10 degree incre.JPG

.
 
#6,893
mark100 said:
Anyway, it's the dcx464 on xt1464 which is the best behaved horn i have.
Click to expand...


That's as good as it gets.

Vance Dickason's HF waterfall with the prototype La Tromba horn and the DCX with the ME464 for comparison (mind the 10 dB increments):
 

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#6,895
Well, the resonance in the HF unit at 5,5k seem to be coming back as the first bigger wiggle (dip!) in the combined FR at just 5,5k. Buts thats really not at the XO point (?). I'm sure the XO have the same problems as any xovered system - and then maybe some as it seem that the mid and hf membranes are physically connected somehow?

My question was around the penalty of a xo vs. more EQ to the top? Given one wanted to get the same BW from a single and a 2 way CD?

//
 
#6,896
TNT said:
I'm sure the XO have the same problems as any xovered system
Click to expand...
At least the lobing is gone, so that's definitely one problem less.

My question was around the penalty of a xo vs. more EQ to the top? Given one wanted to get the same BW from a single and a 2 way CD?
Click to expand...
That's too general question. Personally, I chose HF1440 over DCX464 for the money but that doesn't mean anything. The coaxials seem to get better and better.
 
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