Opinion: has anyone ever used the Audax PR 17 OMO in a midrange horn?

[zobsky]

I own a pair of these drivers and was thinking of front-horn (conical) loading them between approx. 300 - 3000 KHz. Does anyone have any opinions on this idea?

Judging by some crude cardboard experiments I tried (crude is a understatement), it was the most natural of the drivers I tried (PR 17OMO, Tangband W8-1772, Fostex FE-166E), though obviously limited in top end extension.

https://www.madisound.com/store/prod...products_id=90

[zobsky]

The abomination . The final build will be a multi sided (6 - 8) conical horn.

[Brett]

It could work OK. Adrian Mack did a conical based around the Eminence A6 some years ago but the Geocities page is long gone. It did 300-2k.

Some discussion about similar stuff in this old thread, which also has a link to Adrian's page - maybe you can find it in the wayback machine.

You could also do an OS without a lot if extra effort and round would be possible using a laminate of sheets, cut with a router and a 45* bit.

[zobsky]

What's wrong with my sim?

From first principles:
Let's assume a Fc = 250 Hz conical
for 4 pi loading, (free space),
speed of sound = 340 m/s
wavelength at cutoff , w = c / Fc = 1.36 m = perimeter of horn mouth
Radius of mouth rm= w / (2 * pi ) = 0.21 m
Therefore, mouth area Am = pi * rm^2 = 0.1386 m2
Assuming Horn length Hl= w/2, Hl = 0.68 m

Substituting these into horn resp, and using a throat aread = Sd, I get awful results, even after tweaking things around. The sim shown has a throat chamber, but there's little difference with / without it.

What gives ?

Driver specs:
Impedance 8 ohm
Resonance 117Hz
Power 100W
Sensitivity 100dB
Re 6.2 ohm
Le 0.73mH
BL 8.24
X-max 0.5mm
Cms 0.2 mm/N
Qms 3.16
Qes 0.61
Qts 0.51
Mms 9.17g
Sd 139 cm2
Vas 5.52 liters
Magnet weight 31 oz
Speaker weight 5.5 lbs

[CLS]

I've read somewhere that this driver is not very suitable for horn loaded. It seems it likes big mouth. About half an hour of fiddling:

[tinitus]

0.5mm xmax isnt much at 200hz, considering its only a 6"
well, maybe ok at normal SPL

might work better with 500hz xo

[bjorno]

Originally Posted by CLS

I've read somewhere that this driver is not very suitable for horn loaded. It seems it likes big mouth. About half an hour of fiddling:

Hi, Took 30 seconds of fiddling by making the (wave-guide) horn length to ~w/4...I suggest to XO at ~400Hz...

b

[zobsky]

Originally Posted by bjorno

Hi, Took 30 seconds of fiddling by making the (wave-guide) horn length to ~w/4...I suggest to XO at ~400Hz...

b

Yes, .but in reality, .. you achieved that mainly by whittling down the cone mass to nothing. Not practical

[zobsky]

Originally Posted by CLS

I've read somewhere that this driver is not very suitable for horn loaded. It seems it likes big mouth. About half an hour of fiddling:

Yes, I arrived at the same results earlier this week using a large mouth. With that aspect ratio, I'd guess the main benefit would be a a little directivity benefit. It's almost like a shallow waveguide / OB hybrid.

[zobsky]

For what it's worth, one of the reasons I was interested in trying out a conical horn is that the below mentioned router bits should make construction much easier. I picked up some clones of the following bits off ebay last week.

Multi Sided Glue Joint Router Bits

The technique can be applied to tapered boxes ie. conical horns too, as described in
http://mlcswoodworking.com/orderstat...ed-planter.pdf