2 way with WG and 10" aluminum drivers

[Nemophyle]

ok so this is an idea i had in my head for a pretty long time. I studied the problems and compromises i should make in order to achieve that, and i think it's not impossible

i want to take one of theses as a woofer, possibly one of the scanspeak revelator, as i assume they are the lowest compression/distortion 10" alu drivers one could find

Scanspeak 25W8567-SE

Revelator 26W/4867T00

Seas excel W26FX

Seas aluminium 10"

and couple it with a very good tweeter, possibly the accuton c-23, or the seas excel.

as you guessed, the aim is a tweeter that can go low without strain. If you have other alternative i'm open to it.
i would put that tweeter in a oblate spherical waveguide ( according to Dr.Geddes theory) of 10" or 12" diameter, with 90° angle coverage, in order to have a good gain down to 800-900 hz. I could possibly do the waveguide even larger ( 15") if necessary.

i'm not worried about the inherent size of the woofer for a two way, as the aim is sort of constant directivity, beaming of the woofer is wanted.

as i would cross over at 800-1000hz ,(with a computer and some FIR filter i conceived, with very steep slopes) i'm much more worried about inherent limitations of the drivers

what do you think ? am i totally crazy, or is there something worth the effort in my project ?

thanks !

[Nemophyle]

for example, i know that even if i cut the woofer at 1000hz 96db/octaves ( i can do higher) so that the breakup is totally out of the band, there could be manifestations of the breakup in form of odd order distortions down in the spectrum. I know ome very experienced people contributing to this forum works with metal cones and low crossover points, so please enlighten me

[noah katz]

If you're willing to spend for an Accuton, why not do it right and get a high quality compression driver like the BMS 4552ND.

With that steep a XO you could probably use the Eighteensound XT1086 waveguide.

Here's some info on that exact combo

http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=98095&highlight=eighteensound&session=

The 1086 is 60x80, so to match directivity at XO you'd need a bigger woofer and/or higher XO.

Check 18Sound's woofers also, high quality and efficiency.

[Nemophyle]

hello noah

well first will a compression driver get distortion numbers as low as do drivers like the accuton or , let's say, the new scanspeak, or even good seas tweeters ? it is a real question, i know nothing about compression drivers.

second, i really want to use an aluminium cone driver, not a paper or poly cone driver, and it is difficult to sort out bigger aluminium drivers that have decent extension and breakups not to early in the passband

third, i prefer to do my waveguide by myself (for diy reasons you know ), and more importantly, i don't want a directivity as narrow as the one of the horn you quoted, 90° being the max i want,but i'm also considering a 100°, for directivity matching to a 10" woofer.

what i'm digging for is more along the lines of theses : SP tech timepiece 2.1

but with a bigger woofer and waveguide

what do you think ?

[Jonasz]

Why not go with the W26 Excel and the Crescendo? The Crescendos sloping respons below 2k should be compensated by the big waveguide, right? Compared to the SS 6600, the Crescendo have lower 3rd order distorsion and faster decay. It builds on the Millennium but with a bigger radiating area, I don't think you can go wrong with that one.

Test SS6600: http://www.diymobileaudio.com/forum/...ead.php?t=4110

Test Crescendo: http://www.diymobileaudio.com/forum/...ead.php?t=2758

[noah katz]

Nemo,

OK, but you might have trouble finding an aluminum cone that's big and wont't have breakups in the passband.

You might check TC Sounds new pro drivers.

A 1" compression driver has a 1.7" diaphragm, and will excurse less than a 1" for the same output.

I don't know if the distortion is more or less than domes; BMS has distortion curves on their site if you want to try and compare them.

Good luck.

[dwk]

It's pretty tough to compare distortion of compression drivers and normal domes. Compression driver figures are almost always at 1W and 10W, which is ~112dB or ~122 dB. Even if you had numbers at comparable levels for domes, IMHO it's pretty irrelevent. I'd love to see numbers for a compression driver at the more normal 95dB or so - well under 0.1W input. I *thought* someone posted some numbers here in a waveguide thread for a BMS driver at normal levels, but I could be mis-remembering. Guess I should search.
*edit*
Here it is:

http://www.htguide.com/forum/showpost.php4?p=260054&postcount=12

2nd order isn't particularly special, but higher orders are pretty much non-existent. It sure looks pretty comparable to high-end domes.

On the aluminum driver, hard to say. 1kHz is pushing it, but with a steep filter it may work. I have some Seas L26's that I'm trying to find time to integrate into my system. I'm only targeting using them up to 250 or so, but I could test them out higher to see how distortion looks. Not sure when I'll get to it, though.