Isn't a HE12 just a Eminence 12" woofer, with like the APT20 or 50 tweeter? I'm pretty sure I think.....
And Dan like did some modifications to the tweeter or some such, I dunno. I know he has a sorta complex crossover network, which I think is designed with constant impedance in mind. I think, (again) it consists of a bunch of parallel/series notch filters?

It seems a lot of these coaxial ceiling/sound reinforcement type drivers from various manufacturers, have rather compromised passive crossover networks.

Say for example, the B&C Italian coaxials. The 12CXT and 12CXB calls for the same model of crossover network. The 12CXT uses a dome tweeter, and 12CXB uses a radial horn tweeter made out of aluminum, with a mylar diaphragm. But they use the same type network?

I dunno why the B&C website is down, or I would post the filtered response graphs of the differences. (I'll post them when and if the site comes up.)

The 12CXT has a fairly decent response in the upper midrange and top-end, where as the 12CXB horn tweeter looks like a roller coaster.
The tweeter is more sensitive, IIRC.....
I've heard both the 12CXT and 12CXB, and the 12CXT did have a smoother response.

Basically, the filtered response with the 12CXB has four +10db peaks between 1-18kHz roughly, from what I recall.
I'm listening nearfield, and the sensitive tweeters compounded by those swings makes things rather hot unless padded a bit.
And even attenuated, they still have that hot bite about them.

More or less, I got burned out on those rough sounding little bastards.

Currently, I have the B&C 12" coax's in my four foot cabinets ported tuned to 49-50Hz, with the tweeters disabled. I'm using a Klipsch Cornwall K600 horn with the K51V driver, parked on top of the cabinets.
I'm using Crite's CT125 tweeter, a APT 20 or 50 driver with the Klipsch looking type of diffraction horn.

The cut off for the woofer is 600Hz, the midhorn cuts off at 4500Hz,  to the tweeter. The Cornwall balancing networks were easy to modify, a whole 5 minutes with some clip-leads and a screwdriver.

I added another 22uF to the stock 20uF for the woofer lowpass on the Cornwall network. It seemed to tighten up the bass, with a little more fullness. The stock cap was a Aerovox 20uF oil, kinda sloppy in sound. I'm using a couple metal polyprops in parallel for 42uF now.

The klipsch Cornwall and LaScala are a bit too much speaker when it comes to nearfield listening in a smaller room.
Though LaScala with a low watt triode amp at low listening levels can sound pretty damn impressive with respect to imaging.

This combination works well with nearfield. The stereo imaging is better, you can crank them up more without things coming unglued, the bass is tight and digs down lower than the tuning indicates.
And they sound good and boogie with a old SS integrated amp. The Klipsch speakers are particular about amplifiers, with tube amps sounding better, rounding off the roughness I suppose......

But they won't image as well as using the B&C drivers as a coaxial.

I'll be following along to see what sort of research/ideas you come up with with regard to the HE12 crossover network.
If anything, maybe I can probably cobble up the HE12 network to use with the 12CXB, or figure out how to compensate for those nasty swings in the upper response.

The big three-way idea sounds interesting.......Is the application sort of sound reinforcement with emphasis on sound quality?

Mike

From what I've read, (on the net, so who knows.....) that the tweeter for the Adire used a different coupler. But this was in reference to HE10.

The Beta 12 is probably up there around 98db sensitivity, I would guess. Maybe the tweeter is close enough in sensitivity in relation with the woofer, to not really require attenuation.

The B&C 12CXB woofer claims 98db, and 104.5db for the tweeter!
No wonder they seem hot nearfield.

Here's the PDF files for the B&C 12CXB, and 12CXT.
You can see the 12CXB tweeter has way more sharper peaks and nulls.

http://www.bcspeakers.com/download/prodotti/PDF/more/153.pdf

http://www.bcspeakers.com/PDF/PRD/12CXT.pdf

Here's the schematic for the XO2 crossover network for both 12CXB and 12CXT. I don't notice any sort of padding on the tweeter, unless it's the 1 ohm resistor in parallel with 20-21 mH inductor.

http://homepage.mac.com/planet10/forum/BnC-XO2-map.gif

Mike.

Thanks. I always think of the padding resistor in parallel at the tweeter. I didn't pay attention to series input resistor..Doh!

Wouldn't lowering the resistance of the series input resistor throw off the crossover center point with a possible change in impedance?

I probably should google search series parallel notch filters in relation to coaxial speakers drivers.

I was listening to the speaker set-up I pictured in other post with my 2A3 amp tonight.
I didn't think it was going to sound as good as it did. That made me happy.
I've been thinking of trying a tapped autoformer for a passive volume control. I don't really need a linestage. Intact audio has a reasonable priced option to try.

I bought a 100K 24 step attenuator once off eBay for 50 bucks from
China.
It used Holco 1 watt resistors. I liked it better than the common potentiometer.
 
My bitch was that 4 or 5  steps broke before they made. I guess I could have fixed the coupling with a cap or something, but it just seemed to defeat the purpose of a stepped attenuator in the first place.
I ended up getting dumb and tore it apart. The little switching arms or whatever were real delicate, and then it got trashed in re-assembly.

I guess the idea of being able to stack the core of the Intact audio autoformer for matching impedance seems novel.
It would mostly be used for tube amps direct from the CD player.

Another idea that I would like to try, is a DAC with a volume control. Be it stepped attenuator or whatever.

The one audio friend Bob up north was using a Benchmark DAC on a visit once. I really liked that DAC, it had a volume control.
But they are way too expensive for me........

I've pondered quite a bit over getting this Behringer SRC2496 for use as a DAC, and possibly another stepped attenuator.

http://www.behringerdownload.de/SRC2496/SRC2496_ENG_Rev_C.pdf