Acoustic Horn Design – The Easy Way (Ath4)

[Dave Zan]

Better state post #... seem to send you to different places...

I linked to the specific post, exactly to avoid that problem.
Yes, it's a real nuisance when people don't use the specific post address (in the top R. of the post).
But to save the need to follow the link.

The better polar response is as expected, that's the whole point, of course.
Why was the frequency response worse?
Sources sum in a known way so it must be down to a disturbance in one or other of them.
I would expect neither the horn/WG nor the woofer response to be much disturbed unless the woofer was pushed quite far into mouth.
Which I assume you didn't do, based on other speakers of yours that I have seen.
But I haven't actually seen the NA12, can you post a picture?

Best wishes
David

 

[TNT]

OK - now that I clicked the link again I came to a post by you - first time not... strange...

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[Dave Zan]

If you put the cursor on the link then you can see the link address at the bottom of the screen.
When I do this it shows the address of my specific post, not the format where there is a page number count embedded in the address.
So I don't understand why you had a problem.
Anyway, I edited the post to include a quote of the relevant questions in case anyone else has problems.
I try not to clutter up the thread with duplicated text, just a link seems more polite, didn't know it could cause problems.

Best wishes
David

 

[AllenB]

It was a question for Dr Geddes, the link made that clear - Acoustic Horn Design – The Easy Way (Ath4)

Afaik, this link method should work for all member settings.

 

[gedlee]

But I haven't actually seen the NA12, can you post a picture?

Best wishes
David

Just go to the website link below and find all that I have on them.

 

[jtwrace]

GedLee LLC

 

[mabat]

The back side stays as you see it, it's really not critical. ...

Actually, the thin wall version is smoother (for me this is not really intuitive and I wonder if this is not just a simulation thing):

"Filled-back" (sand printed version with a thick wall):

 

[mabat]

Well, maybe it makes sense after all. In the case of the "hollow" roll back there's less of what the sound can reflect off, i.e. the thinner the wall the better.

 

[TNT]

Amazing that this shows Do you know what exactly is mixed with the sand? Some sort of epoxy?

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[Dave Zan]

GedLee LLC

Thank you.

...find all that I have on them.

I knew you had stopped manufacture of this speaker, didn't realise you still had the picture up.
This confirms that the woofer has only been nested very little into the WG, as expected based on your previous comments.
But that only makes me more curious as to why such small difference would make the frequency response worse.
Presumably either the woofer or WG frequency response must have altered.
Did you determine which was responsible?
Is diffraction from the woofer frame and surround detectable when it's recessed to match as neatly as shown in the picture?

Best wishes
David

 

[jzagaja]

Amazing that this shows Do you know what exactly is mixed with the sand? Some sort of epoxy?

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cyanoacrylate glue?

 

[jzagaja]

I have always been interested in porous boundaries as they would have a big effect on all but waves parallel to the surface (the zero mode). In this later case the effect would be smallish, but for HOMs it would be large.

Porous walls or internal volume or both? Why not print porous waveguide - will be slow but doable.

 

[mabat]

Do you know what exactly is mixed with the sand? Some sort of epoxy?

1) The binders for printing ifself: ExOne | Sand Casting Materials & Binders
2) Then it's possible to further impregante with epoxy, after the printing is done (they do it on demand).

 

[jzagaja]

Application: deeptime.limited

 

[TNT]

1) The binders for printing ifself: ExOne | Sand Casting Materials & Binders
2) Then it's possible to further impregante with epoxy, after the printing is done (they do it on demand).

Interesting - if I here you I would try to get equal formed samples using the different binders and listen to them while being struck. Silica i guess will ring as it is glass...

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[jcarothers]

Honestly, I wouldn't expect any of these to ring very much, if at all. Epoxy-saturated composites are pretty common for precision machinery bases, where they're used specifically to add mass and damp vibrations (for things like CMM measurement equip, optical test beds, etc).

 

[TNT]

Me neither but they might have a slightly different signature - why not choose the most neutral?

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[mabat]

Sure, let us know what you find

 

[TNT]

:-D

Which one will you choose?

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[mabat]

I don't care, really, haven't thought about that (yet). I'm more concerned about the binder, its health issues and (bad) smell. That still may be a weak point, even though the Deeptime (linked above) seems to stand well. Maybe the final coat can do a lot in this regard, I don't know.