Study of a Dipole/Cardioid Bass Horn

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I'm not sure if the inner flare is the same between the two JBL drivers.

I think I have read somewhere that the inner horn expand from 1,5" to 2" between it's distance.

With eye I would estimate that the phase plud ends/inner horn starts quite near where the top plate starts. Thus the inner horn might be around 59mm long in 2446.

The angle can be calculated from that. It is around 11,5deg, if the inner horn is 38mm at the start 50mm at the end, and 59mm long.
Legis,

I think you are correct, it looks like the 2441 also goes from 1.5" to 2", but the throat looks like it is around 79mm, another 20mm longer than the 2446.

Art
 
Taken to the extreme you just use a flat diaphragm at the throat of the waveguide, and skip the compression driver altogether.

I'm strongly considering that for my next project, not 100% sure if it will work, because a CD allows for a lower xover than a 1" flat tweeter

Didn't notice this before. Why do you/would you want to use a non-comp HF driver? What comps have you used before?
 
Hi Legis,

I don't know if any of this will help, so just take it as techno musing (not music). 🙂

I started looking at using 11 degrees in AutoCAD. Then I looked @ the respective square areas in 1" steps from the driver mouth. Your areas would be rectangular, but the same method should tell you where the horn cross-section matches the driver throat angle extension cross-section. For example I found, that w/ a 1"Dia. mouth/14 degree throat angle driver you get from the 1"Dia. circle to a 1" square mouth in about 1/2" distance; so the mounting plate can also become the shape transition.

Regards,
 

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Hi Legis,

I'm still thinking about the driver to horn adaptor problem. I'll attach a sketch of what might be about correct.

Regards,

That looks really good transition to me, thanks! My horn adaptor is 30mm thick total (2x15mm). I have used a router to round the adaptor's exit to the horn (maybe the last 5mm or so). I have thought to make the whole adaptor with a small opening angle, close to 11deg (what the 2446 has) vertically and maybe slightly higher angle horizontally.
 
Managed to do a small flare to the adapter also, it was very good addition. This is how the throat is looking before I start finalize them by adding very small layers of wood filler and sanding it down to smooth surface. I'm very happy how they look and feel (very damped because of the thick layer of wood filler) and have no doubt the throat will sound very good.😉 The geometry does not show good until I have painted them I quess.

An externally hosted image should be here but it was not working when we last tested it.
 
Some progress. Heavy brass spikes (Eden Sound Bearpaw Sr.) and rosewood "pucks". Something less ugly to damp the mouth of tapped horns/pipes would be good.🙄

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 
I would be inclined to pick a newer driver with a smaller throat.

I want the best dynamics, very good/unchanging clarity at high SPL and cross low, 4" phragm comps are natural option. With Truextent Be phragms the get even better.

I previously had BMS 4550 and before that Beyma CP380M. I wouldn't pick a non-metal dome comp anymore.
 
"4" phragm comps are natural option. "

So use a JBL with a 4" dome and a 1.5" exit.

2447, 2451 2452, 2453, etc.

I propably will get some other 4" comps at some point. However this is not the first priority as I believe the 2446 will be very good with Truextents based on some experiences I have read. Some say 2445/2446 is their favourite driver shell/chassis with those 'phragms, exceeding the SQ of TAD TD4001.
 
Things are progressing. The throats are 99% complete, just minor smoothing if left to be done. The inside edges of the 15" injection ports have been slightly rounded (more on the apex side) and the 15" adapter edges have also been rouded with wood filler and sand paper to reduce all possible "two parallel wall action" to minimum inside the whole thing.

Synergy_prepaint_zpsf36d45c4.jpg
 
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Some more (all of it) painting done, I'm quite satisfied for the result. Both tapped horns are also painted and ready to rock. I think I can put them back together tomorrow, if I manage, the paint should be hardened enough. I have to think some temporal stands for the synergies.

I'm quite interested to see hear what all the smoothing and rounding has done to the sound. 🙂

(pardon for the mess)

synergyX2_zpsb2b00ab4.jpg


redhorn_zpsc0a79299.jpg


Throat #1 and #2:

redhorn2_zpsa3381d0b.jpg
 
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