Acoustic Horn Design – The Easy Way (Ath4)

[mabat]

Regarding the T34-A; an (unmodified) OS-throat is probably not the best interface for the concave surround. It's basically a cavity that's extended axially by the OS-profile and likely the cause of sub-optimal performance in the treble range.

This doesn't follow from the data.

Convex surround:

Concave surround:

It's just that the OS profile doesn't fit to the source shape and velocity.

 

[mabat]

Could you also plzze plzze try to sim the Peerless 830970?

Platon Measurements

I can model anything defined by a source definition script. If you (or anyone else) provide this I can try it. The problem is that the real diaphragm may not be moving as a rigid body - then the simulation won't be correct. With the tweeters above, this simple assumption (used throughout ABEC) is fulfilled to a large degree, at least in the audio band. I'd be not so sure with a bigger driver.

 

[mabat]

The T34B + OS throat again - these are the raw polars (were normalized on the previous pictures) and acoustic impedances of the dome and the surround individually.

 

[mabat]

And this is for the conical throat -

 

[mabat]

Now it starts making more sense - this is still a conical throat, only narrower than before (this is ~60 deg, the previous was ~100). So it is not the OS profile per se but a non-matching profile in general.

 

[mabat]

Oh sh*t! Accidentally I had the radial velocity set, i.e. this was not a simulation of a dome tweeter but a pulsating source... It's no wonder it was so nice when matched. Sorry for that

 

[Ro808]

This doesn't follow from the data.

Convex surround: ...

Concave surround: ...


It's just that the OS profile doesn't fit to the source shape and velocity.

Yes, either convex or concave - depending on the size and shape of the surround, an OS throat is not ideal for the wavefront emitted from the "average dome tweeter". However, this doesn't imply that an OS throat cannot work with all dome tweeters.

 

[Twellmann]

Hey Mabat, are you permitted to share the BlieSMa dimensions?

 

[mislaaav]

Guys! Can someone translate from post 922's ath pre 4.5 coding to 4.5 Acoustic Horn Design – The Easy Way (Ath4)

Mine convert ended twice the size or so, also would someone post some complete cfg's to get a quicker feeling for things! Thanks

 

[mabat]

I thought that the attached file was among the demo scripts but now I see it isn't. That's the JBL style waveguide for 4.5 , I hope (can't check right now).

Twellmann, sorry I don't have the permission.

 

[mabat]

.. this was not a simulation of a dome tweeter but a pulsating source...

So here is the correct simulation, i.e. with axial motion of the diaphragm (normalized at 30 deg):

A pulsating source remains the holy grail

 

[danibosn]

Fluid



thank you very much. Now I can compare my designs


danibosn

 

[454Casull]

I'll also try to cover the surround with the waveguide somehow but I'm afraid that will not improve things that much. So far I haven't tried to model any ring radiators.

The Vifa/Peerless plastic-tip ring radiators are said to be quite well performing in waveguides. I'd be very interested to see how they work.

Keep up the awesome work!

 

[augerpro]

Anyone know an easy way to measure the radius of these domes?

 

[Twellmann]

Goose down calipers

 

[bmc0]

Marcel, have you tried reducing the throat radius so it covers part of the surround? I tried this years ago for an old speaker project and saw some improvement. The tweeter I used had a convex surround, so I did something like this (apologies for the crappy drawing):

 

[mabat]

Anyone know an easy way to measure the radius of these domes?

You mean the radius of the sphere? Measure the radius and height of the cap and calculate the rest: R_sphere = (r^2 + h^2) / 2h
If I wanted to be sure, I would draw the contour in a CAD, print it in scale, cut it and try if it fits.

 

[mabat]

Marcel, have you tried reducing the throat radius so it covers part of the surround?

Not yet but the tool now allows that quite easily so I will probably leave that for others who want to play with it. I'm almost finished with the user guide so this new version should be released soon.

 

[mabat]

Finished the User Guide for 4.6, so before I prepare the package for downloading, you can at least skim through the PDF: Ath 4.6.0 - User Guide

 

[tmuikku]

Impressive work mabat!