811 Fins

[SOOTSHE]

I removed them on my 19's. I like the results. I sit nearfield, and it removed the sensitivity of the sweet spot. It's bigger, not so sensitive to head movement.
Think of it this way, the center vane is right in line with the center of the driver.
In a theatre....these are theater horns....no issue because the sound will recombine. Sit close and it's a different story.

I also remove the bug screens, a mod that others here poo poo. Huge diff in my experience.

I have a picture tutorial on how to do it if you like. It involves a sawsall, a die grinder, bondo, sanding and paint.

I also damp the horn dead with latex paint and sand....thanks Jim Dickenson.

Ron

Thanks to all those that responded....some great info there. I think I'll just go with the latex paint & sand & a sand bag in the the top bell.

[Old Guy]

Hi Old Guy, thanks for your reinforcement of my 811 fin theories. Just a tiny comment... Jim Lansing did seem to like multicellular horns, as they were the only type he used. The last one he designed was the H-1000 which was used with the 175 driver in his postwar 1200Hz. crossover two way Lansing Sound systems:

http://www.lansingheritage.org/image...1948/page7.jpg

Jim died in late 1949 and within a year or so William Thomas had secured the services of Bart Locanthi, who designed the small potato masher "Koustical" horn (later 175DLH) and the large masher theatre horn for the 375. The folded and flat plate lense horns came soon after. His work was based on that of Kock and Harvey of Bell Labs who had published a paper on acoustical lenses in 1949. Mr. Locanthi's wife was an optics engineer, and likely provided guidance as well.

As I have heard the story, JBL added the Vitavox-built multicellulars to the line in the 1970s so their dealers could bid on contracts that were written to virtually specify Altec equipment. These horns were sourced through Dukane (I think), who also marketed these horns under their name.

Ahh.

An ex JBL employee had me convinced he had turned against them.

Your last paragraph coincides with what I got from guys at DuKane.

[Cal Weldon]

I think I'll just go with the latex paint & sand & a sand bag in the the top bell.

My new favourite is the wax in the top lip. Add some wicks and you have double the fun, not to mention the romance of having speakers with built in candles. Ooh la la how can she resist?

[GM]

Hi GM, your post sent me scurrying for Abraham Cohen's book "Hi Fi Loudspeakers and Enclosures", always a good thing. For those who haven't read this book, try to find one at abebooks.com or somewhere, as it is essential reading.

Were you referring to the picture of the Altec 3000 tweeter and illustration of the pattern? I may be all wet, but it seems to me that at least on a radial midrange horn like the 811, the dispersion pattern has pretty much been determined by the time the sound energy reaches the fins. Being a radial horn with two straight sides, the horizontal pattern would be largely that of a conical horn with its excellent directivity.

Greets!

Agreed, a bit dated in some ways, but its info has withstood the test of time and helps one to cut through marketing BS.

Right you are, but what do you get from a conic expansion? An on-axis hole in its HF response, but this isn't the case with the sectoral horns due to all the reflections at the mouth just as RonSSS noted. Hopefully, we can all agree that one must be on axis to them to hear the highest frequencies.

That said, it is subtle in a typical HIFI/HT app unless considerable CD horn EQ is used to flatten its response out to > 15 kHz and of course older and/or long term abused ears such as mine aren't going to notice it much, if at all. I could when I was younger, though I didn't realize how much they added until I cut out the vane welds and bridged the gap with a GE silicone gasketing product. Ditto adding damping to the sides of the horn. This widened the 'sweet spot' a bit at the expense of some top end 'air' and why historically I've nixed the tweak unless a super tweeter system is added.

Consider too that a horn's response changes somewhat at high SPLs same as a point source driver, so for the cinema app that the sectoral horns were designed for, the vanes are a must for firing through a screen due to an on axis flattening of its response and why I've periodically suggested making grills from screen scrap as I did for my previous system as an acoustic solution to an acoustic problem. Of course this requires more power for a given average SPL and especially transient peak SPL, so not for flea power systems.

GM

[Derry]

I like the wax pour I did on all the bells,, wife says I should have used scented wax,,


Derry

[GM]

Thanks to all those that responded....some great info there. I think I'll just go with the latex paint & sand & a sand bag in the the top bell.

FWIW, if I were only going to do one major tweak it would be to cut the welds out of the vanes and fill the gap with rubber wedges as Altec did in the 500 'C'? variant which was also Aquaplas coated (your sand coating will do similar) or some other damping that sounds best overall, though you want to do the experimenting after EQing the system as flat as practical out to at least 15 kHz. A lot of its ringing is due to the coupling of the two bells combined with the warping that occurs in the welding process and as I previously noted, it mutes (smooths out) the on axis response a bit, though not as much as removing them does. When mounted externally, using a baffle rather than just a mounting strip helps too.

GM

[GM]

My new favourite is the wax in the top lip. Add some wicks and you have double the fun, not to mention the romance of having speakers with built in candles. Ooh la la how can she resist?

Yeah, with each bell partitioned and having a different scented wax in each it could be a Deja Vu 'Summer of Love' experience for the youngsters among us, especially those conceived during that time!

GM

[Derry]

you can actually hear the sound changing as the wax burns off and the ringing returns,,:laffingassoff:

Derry

[Altec Best]

Yeah, with each bell partitioned and having a different scented wax in each it could be a Deja Vu 'Summer of Love' experience for the youngsters among us, especially those conceived during that time!

GM

Like church Bells at a wedding after all those conceived children.

[Audio_by_Goodwill]

I like the wax pour I did on all the bells,, wife says I should have used scented wax,

I hate those scented candles....... can't stand the things. My sister has been known to use them and she can't smell anything at all!!! I do not understand why women like them so much.