Horn Design - Sanity Check

[deiksac]

I am about to build a midbass PA horn - the intended frequency rande is about 150-500 Hz and have two rather exotic 15" drivers from Meyer Sound. Had not seen anything like this - see T/S parameters:
Diameter 15"
Fs 142 Hz
Re 3,06 ohm
Res 4,23 ohm
Qms 0,87
Qes 0,63
Qts 0,37
L1 0,31 mH
L2 1,06 mH
RMSE-free 0,41 Ohm
RMSE-load 0,2 ohm
Vas 11,94
Mms 107,55 g
Cms 12 um/N
BL 21,57 T-m
Splref 99,2 dB
Sd 855 cm2

The throat area according to the formula at the
Single Driver website result in some 115 cm2 which feels rather small to the 850 cm2 Sd - What do you think?

The final enclosure will be pretty huge - 102 cm (W) x 51 cm (H) front area since two midtop turbosound enclosures will be sitting atop this one. Another question stems here - the mouth area corresponding to the 150 Hz Cutoff is pretty large - half size horn would need (again according to the formula on the abovementioned page) to be some 2 m2 whereas I only have about 0,5 m2 available

[BHTX]

Originally posted by deiksac
Fs 142 Hz

142 Hz?? Very unlikely. More like 42 Hz maybe.

[deiksac]

not at all, exactly as I have written, measured on MLSSA

[MaVo]

you could use hornresp. the function "system design, with driver" will design a horn for you. after that, you can play with the numbers.

[BHTX]

Originally posted by deiksac
not at all, exactly as I have written, measured on MLSSA

Ah..apologies then. And you're right, I've never seen anything like that either! Only suggestion I have is what MaVo said. Unfortunately, I don't possess much knowledge about horns at all. Hopefully you'll be able to figure something out. Must be pretty exotic indeed. Goodluck.

[deiksac]

:-) sofar I did not become any smarter so I decided to go experiMENTAL
since the saw guys at my plywood distributor are selling me their cutoffs (oops - 6 sqm of 22 or 26 mm mdf, 2 sqm of 4 mm plywood plus some smaller pieces for rack and other speakers for some 50 USD) I will just play and see what will be the result :-)
the prototypes will be 102x51x74 cm big, horn lenght some 54 cm

forgot to add that these speakers should handle some 1200W each

[Frode]

As I've said before, I'm no expert. But here's a couple of screenshots from Hornresp.

Frode

[deiksac]

Thanks Frode, seems promising

[GM]

Originally posted by deiksac

The throat area........What do you think?

Greets!

Yes, the small throats the various formulas predict will require a phase plug to work well out to 500 Hz, which in turn will require a larger throat to accomdate it, ergo a larger mouth than the flare frequency implies. For a prosound app, will it actually have true half space loading? Horns with this high a cut-off usually are in closer to full space. Anyway, this horn's HF corner is ~450.8 Hz, so the throat starts rapidly constricting above this point.

As Frode showed, you can manipulate the design to hit a target mouth area and using Prof. Leach's math yields a slightly larger throat, lower 'M' for a little less distortion at high power, but I don't see it being this smooth nor handling much power for long due to the high compression ratio (CR).

Really, if this driver has the typical stepped HF BW of a horn driver, then we can truncate it with a larger throat, making it shorter and maybe have no need for a phase plug.

BTW, for my records, which model is this and is there any plots available?

GM

[GM]

plot: