ToneTubby 12" AlNiCo OB + Beyma CP380M Horn Project

[nullspace]

Hi All --

This project began some time ago, using a different drivers. You can find a post about it here. Since then, I moved away from using vintage drivers and am now working with current production, specifically the ToneTubbys and Beyma compression driver.

Here is the long version; it's worth a look for the crossover schematic and the suite of measurements (such as they are). The recap is that I put together 2x ToneTubby 12" AlNiCo on an open baffle plus the Beyma CP380M 1" compression driver on the AH!1000 50deg conical horn. The speaker covers from ~100-120hz and up with some pretty high efficiency; my measuring setup isn't calibrated but I'm guessing upwards of 98db/W. It's set up as a 2.5way, with the horn driver crossing to the upper TT12 at 1.2khz and the lower TT12 lowpassed at 270hz, compensating for baffle rolloff.

I'm sure there's a ton of stuff I missed when putting together the crossover, but all in all it's not too bad and I'm very happy with the sound. Very dynamic, nice tonality, and not at all forward or shouty in and of themselves (crappy recordings are another thing, however). I like the Beyma drivers quite a bit; they seem to do very little wrong and blend well tonally with the ToneTubbys.

I still need to work on the (sub)woofers. As expected, the mains rolloff around 100-120hz. I have something in place now, but it's not worth discussing. I have a quartet of OB15 from the nice fellows at AE, and I'm looking forward to getting baffles made and the active filtering built up. I already have the boards back from ExpressPCB and components have arrived from Mouser.

I don't want to drone on, repeating verbatim what's on my website, so feel free to check out the long and short of it there and ask any questions you might have. Citiques and suggestions for improvement are most welcome. Of course, thanks are due for some help along the way --in particular, Duke w/ Audiokinesis spoke with me at length at RMAF and we've traded an email or two since then. There's been several good threads here at diyAudio: Geddes et al on Measuring Loudspeakers, Large midrange for OB??? Scott G?, and, obviously, Beyond the Ariel stand out.
Regards,
John

[CLS]

The baffle is so beautifully made!

And the response of Beyma+conical horn looks pretty "CD" to me Very uniform off-axis.

How does it sound?

Before heading to make the subs, please go see the wonderful thread by Mr. Graham Maynard here: 'T'-bass drive for OB LF drivers.

The T-bass circuit is definitely worth a try. You'll love your OB even more.

[nullspace]

Thanks for the kind words.

I'm pretty happy with them. Very nice dynamics, both micro- and macro-. Nicely articulate, but still with a pretty relaxed feeling to them. I really like the tonality, but I wonder if others might find them a bit warm. I spend a lot of time tapping my toes...

We'll see how the (sub)woofers work out.

Regards,
John

[tinitus]

Finally we get to see them OBs with TT alnicos, and that with a very nice horn

[nullspace]

Hi All,

Just to wrap up, I finally got the AE OB15 plus active filtering up and running. The stereo (sub)woofer controller consists of volume control -> open baffle compensation -> 2nd order lowpass -> 2nd order highpass at ~28Hz with variable Q -> phase correction. It took me about half an hour on Saturday to dial in the woofers. Crossover to the mains turns out to be ~120Hz, and the woofers are pretty flat to 30Hz - except for a 8dB suckout between 40 & 50Hz. Here's a picture of everything piled into my living room:



Also, I've posted an update at my site; you can check it out here.

Regards,
John

[Lynn Olson]

Congratulations!!! Thanks for all the measurements and boldly going where few commercial manufacturers have gone before. I imagine the sound is plenty dynamic and has the hallmark OB spaciousness.

[nullspace]

Thanks Lynn. I think they turned out well, and I'm enjoying listening to them a great deal.

Also, thanks for pointing out the ToneTubbys -- it's a real gem.

Regards,
John