Altec drivers for 511B horns?

[RobWells]

Thanks for the more detailed reply GM, unfortunately the link you posted didn't work for me.

I think for my app (home cinema) the higher power handling versions would be better with my beymas cutting in around 5kHz to avoid the harsh top end.

Cheers,
Rob.

[Pano]

Aloha GM.

Thanks for the graphs. That 511 graph by Danley caught my eye because of the kink in the plot that is noted as 20" Baffle. With my 811s rear mounted flush on a 24" baffle there is a mighty kink at 900Hz. Peak-Dip-Peak. Fairly narrow.

That's one of the things that wrapping towels around the mouth edge helped, eliminated, actually. And it took towels top and bottom to cure it. So my guess is there is something going on between the concave outside horn shape and the baffle.

The graph is posted below. No, the response is not that flat, it was normalized to the FR with 2 towels. You will see the results with 1 and none, also. (ignore the low end, that's room noise)

[GM]

Originally posted by GM
Greets!

More good info I forgot to post: http://web.archive.org/web/200411110...com/altec.html

GM

Oops! this was the main page, I meant this one which just worked for me: http://web.archive.org/web/200411110...s/smallVOT.pdf

[GM]

Originally posted by panomaniac
Aloha GM.

Thanks for the graphs.

So my guess is there is something going on between the concave outside horn shape and the baffle.

Greets!

You're welcome!

Yes, there's standing waves between these huge protrusions and any acoustic or hard boundary. I like Lee T. Neidow's trail pad foam horn extension variant to control both horn and direct radiator off-axis response. Zero SAF, but he's like me and doesn't give a toot. NHT uses (used?) a foam strip variant on one side of their tweeters, mids of some models: http://nhthifi.com/2006/images/about/33lg.jpg

GM

[RobWells]

Downloading now GM.

While I've got peoples attention here, my 511's have had the centre brace removed but I've read thats a good thing. I've just got to grind out the remnants of the welds and fill / sand. The previous owner also removed the 'rubber gunk someone had put between the vanes' Is there a special type of hard setting rubber etc or can I use bathroom sealant to put it back in.?

Cheers,
Rob

[tgarson]

That brace placed stress on the top and bottom of the horn to prevent the metal from "ringing like a bell". Whoever removed them did you no favor. Whoever said it is an improvement is tone deaf.

Assuming you are not an artist with a MIG welder, and you want to restore the beneficial effect of that brace, cut a piece of 1/4" steel rod that is about 3/32" longer than the distance between the top and bottom at the center of the location of the original brace. Grind each end to a SLIGHTLY rounded point. Drill a 1/8" hole (with a long bit) all the way straight through the horn at that point. Wedge the piece of rod into those holes. It should not be easy to do and should be tight when seated. You should be able to hear a huge difference in the resonant tone of the horn ( tapping it lightly with a small hammer) after replacing the brace. When done, seal around the holes with some JB Weld, or equivalent epoxy.

We used to add braces like that to the big aluminum radial horns from Altec and JBL, as a matter of course.

[tgarson]

My plane wave tube doesn't lie. The 802 was the finest small driver that Altec ever produced and maybe the best 1" driver ever built by anyone. (all aluminum (not symbiotic) diaghram)

Yes it 's power curve is not as "flat" as the later 900 series, which used the "tangerine" diaghram. But, the 802s smoothness of power response and phase response is almost textbook. A simple R/C equalizer is all that is required to make an 802s top end sing sweet and strong with less shrillness than a 902 on a modern horn. Since a 511B horn is designed to beam the high end and spread the midrange, you definitely do not want to load a 902 on one, if you value a balanced sound. It will be BRITE!

The "tangerine" by the way, is a travesty. It achieves its flatness by using progressive phase cancellation to reduce midrange efficiency. The driver isn't brighter, it just has wimpier mids than an 800 type with the tradition annular ring sectoral horn phase plug design.

I'm sure the boys who developed all that stuff at Bell and Westinghouse rolled over in their graves when Altec introduced the "tangerine".