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View Full Version : frequency range question about 811b horn & 808-8B 1.75" Comp



I_B
01-23-2012, 05:42 AM
Sorry for newbie question.

What sort of frequency will the combination (811b horn & 808-8B 1.75") Comp play upto where one would benefit from adding a tweeter?

What is the upper limit I should bare in mind when researching tweeters to go over this combo?

I have just bought 811b horn & 808-8B 1.75" Comp - I have a few week wait before I can get my hand on them and feeling impatient.

I have seen a number of pictures of tweeters over the horn and was left wondering.

Thank you!

rudy sesztak
01-23-2012, 01:09 PM
The Altec 808 drivers have a Symbiotik voice coil diaphragm assembly, that handle more power, but have dull high end. They start to roll-off at 8-10k. Try to find used Jbl 077's or 2405's- RUDY

louped garouv
01-23-2012, 01:32 PM
just be sure your drivers do in fact have the high powered versioned diaphragms...

you can basically change some stuff around to make that 808-8B the same spec as 802-8G,
if my understanding is correct...

basically it involves:
alum diaphragm in place of higher power rated diaphragm
removal of loading cap if present (and changing of screws to accomodate depth changes)
addition of felt to the back cap



some additional discussion here:
http://www.audioheritage.org/vbulletin/showthread.php?20866-808-8b

also, play around with the crossover point -- some folks feel that the 811 horn should be crossed at 1200Hz or higher -- to sound less 'honky' or 'horny'

herki the cat
01-23-2012, 03:07 PM
Sorry for newbie question.

What sort of frequency will the combination (811b horn & 808-8B 1.75") Comp play upto where one would benefit from adding a tweeter?

What is the upper limit I should bare in mind when researching tweeters to go over this combo?

I have just bought 811b horn & 808-8B 1.75" Comp - I have a few week wait before I can get my hand on them and feeling impatient.

I have seen a number of pictures of tweeters over the horn and was left wondering.

Thank you!

:dont-know:,What is [1.75" Comp?]...BTW, 811 B horn is well known to be excellent crossed over around 1,000Hz, instead of 800 Hz, for "No Honk performance." I think this was the case in the Altec type 16 system. herki[Quote/]

Mr. Widget
01-23-2012, 04:57 PM
:dont-know:,What is [1.75" Comp?]...That's the diaphragm size.

I agree with you about 1-1.2Khz as the low end for that horn. The 511B is better if you want to go down to 800Hz.


Widget

I_B
01-24-2012, 03:05 AM
The comp is the 808-8B.

It is taken from the Altec 1233 PA system.

I intend on crossing the 811b and 808-8b at 1.2khz.

Altec Best
01-25-2012, 12:37 PM
I intend on crossing the 811b and 808-8b at 1.2khz.


Yeah like a model 19 crossover (1200 Hz). If those drivers still have the symbiotiks ? I would change them out to an all Aluminum diaphragm. 34647 from Great Plains Audio.You can swap out the Frams for $90 a piece, a whole lot cheaper that having to buy new drivers.They will then extend the HF.