2.5way with GPA 414-8C?

[nullspace]

Hi All,

I'm thinking about a next speaker project, and was wondering what the community thought of a 2.5way with GPA 414-8C & GPA 902-8A w/ Bill Woods' small 1000Hz conical horn (AH!1000).

My preliminary thoughts are of having the one 414 in a sealed box ~50litres and the .5 one in a BR ~110litres tuned low, around Fs. Crossover is obviously TBD, but I suspect that the crossover from the horn to the upper 414 will be around 1-1.2kHz and the first-order filter for the lower 414 will largely be room-dependent.

Some of the particulars... Amp output impedence is 2.5-2.6ohms. And here are the t/s #s Steve @ GPA sent me:
RE 5.80 Ω (23◦ C)
FS 26.6 Hz
QTS 0.21
QMS 5.84
QES 0.21
SD 81.71 in.2 (0.053 m2)
XMAX 0.15 in. (4 mm)
VD 12.26 in.3 (0.2 l)
VAS 10.49 ft.3 (297.0 l)
ηo 2.52 %

Any comments or suggestions? Any pitfalls to be aware of? This would be my first 'boxed' speaker, so any and all thoughts are welcome. And thanks in advance for the help.

Regards,
John

[hmolwitz]

Good Stuff, there is a long session with Zilch and Skywave-Rider on Lansing Heritage on a 9844-8b, I think they were fairly successful.
[ame=http://audioheritage.org/vbulletin/showthread.php?t=18913]Altec 9844-8B - Lansing Heritage Forums[/ame]
Best informed posting anyway
Harry

[Earl K]

- Sounds like a nice project . IMO, the 2.5 concept is a good idea for HiFi .

- I had occasion to professionaly use some 414-16Bs before Christmas last year ( 9844As at an old theatre install ) and found that they lived up to their high billing . Even the 806/811 combo was a pleasant surprise ( even if somewhat ragged in FR )

- I'd want to hear my 902-8As properly Eqed ( passively ) on those "AH" conicals before I handed over that much cash ( or at least have a mit-full of sterling references from satisfied customers / who are removed at least an arms' length from the gang at Oswalds' Mill ) .

>< cheers

[nullspace]

Thanks for the comments guys.

- I had seen that thread, but never read all the way through. Seems like the 2.5way worked out for Skywave, but I would've thought that the 9844 layout would be sub-optimal for that configuration. I thought that the reason Altec used two drivers in parallel is so directivity would match the 811's. With just one, I would've thought the possibly abrupt change in directivity would be an issue. I didn't see any off-axis measurements in the thread, so who knows...

- The AH conicals I already have. Currently, I'm using them with Beyma CP380M's. I have to say, I really like them. I've gotten to hear a couple of setups with conical horns (never the Cogent stuff, though, unfortunately) and I've enjoyed them all and would recommend them pretty much without reservation. In fact, I also have a pair of 'remagged' 802-8D's already but wanted to check out the current production GPA stuff just to see what's what.

Regards,
John

[DonM]

Thanks for the comments guys.

- I had seen that thread, but never read all the way through. Seems like the 2.5way worked out for Skywave, but I would've thought that the 9844 layout would be sub-optimal for that configuration. I thought that the reason Altec used two drivers in parallel is so directivity would match the 811's. With just one, I would've thought the possibly abrupt change in directivity would be an issue. I didn't see any off-axis measurements in the thread, so who knows...

- The AH conicals I already have. Currently, I'm using them with Beyma CP380M's. I have to say, I really like them. I've gotten to hear a couple of setups with conical horns (never the Cogent stuff, though, unfortunately) and I've enjoyed them all and would recommend them pretty much without reservation. In fact, I also have a pair of 'remagged' 802-8D's already but wanted to check out the current production GPA stuff just to see what's what.

Regards,
John

I believe that Lynn Olson has selected the alnico version of the GPA 414's in his project referred to as "Beyond the Ariel". These would match up well with your Beyma CP380M's with a 1200 hz crossover.

Regards,

Don

[nullspace]

Thanks Don. I meant to ask Bill when I had him on the phone a couple of weeks ago whether the AlNiCo and ferrite share the t/s #s, but forgot.

Regards,
John