Altec A7 Drivers and Horns

[Brian Johnson]

I have 2 pairs of A7-500 cabinets one pair has 416's with 8ohm coils...the other pair has 421-8H's.
2 811 horns
4 511 horns.
2 908-8A drivers
2 806A drivers with 8 ohm diaphragms
2 drivers that are almost identical to the 806's but a little over 1/2" longer that I assume are 802D's. They also have 8 ohm diaphragms.

What would be the best horn/driver combination to match with cabinets with the 416's?

What would be the best horn/driver combination to match with cabinets with the 421-8H's?

I will bi-amp one set and use N-500E Dividing Networks or make some Hiraga 8 ohm crossovers like the ones on Pete Riggles page.

My skills lay with hardware building and hope someone with the technical expertise can give me some ideas of what combinations should be best and hopefully explain
why in layman's terms. I will probably try different combinations but would like to start with what is technically the best.

Thanks for having such a great source of information available.

[Earl K]

What is it that you want to do with this stuff ( PA or HiFi )?

What you have there are some large Theatre style components ( that suffer from a real lack of bass response and UHF ).

Some users have coaxed reasonable LF from the cabinets by retuning them to 50hz and then backing the boxes into corners ( for LF reinforcement ).

Taming the excessive "midrange shout" from the horns is priority #1 in my mind .

To do this you must build up a midrange suppression ( EQ ) circuit like Altecs own 30923 circuit.



The best "HiFi" match would be the 416 woofer coupled to the 802 driver on the 511B horn.

Be aware that Altec's 811 & 511 horns ring like a bell ( when un-damped & un-secured ) excessively coloring the sound ( just the opposite of what is needed for HiFi listening ).

Here are the pics of 811 & 511's ringing ( in 2 CSD files made by Zilch some years back )




That ringing is a mere 10db lower than the fundamental ( meaning its half as loud and a significant contributor to the overall listening experience ) .

It's up to you to get the ringing down to something like 20- 30 db lower than the fundamental ( for clean HiFi reproduction ) .
You'll need to exercise your Google chops to scare up the various techniques necessary to achieve figures like I just mentioned.

Fully tricked out A7's ( or A500 ) can bring a lot of listening joy when fully modified into the land of HiFi >
though it's usually a journey best left to those with measuring capability and the insight into what the deficiencies of these large Threatre boxes actually are.

[Earl K]

Hi Brian,

You could do worse than to read all of the build threads from alancohen ( located over at HOSTBOARD.).

He has nicely documented his multiple journey's ( over a few years ) exploring all aspects of that Altec goodness .

I found his "search" was very interesting & enlightening .

I'm sure there are some nuggets of info in those threads that you will help you out.

[Brian Johnson]

Thanks for reply...I also have a pair of subs that have some JBL 2242H's in them. They came out of a venue in San Diego called 4th & B and I got them at an auction when they closed. They have been professionally rebuilt. I have the equipment to Tri-Amp them along with a pair of the A-7's. I'm probably just going to mix and match to see what they will do and since they take up a whole wall. I'll probably look for somebody to buy them that will put them to better use. I was doing a few small P.A. gigs over the past few years but I will be 65 this summer and don't have the same energy. Before I sell them I'd like to get them setup right to demonstrate to buyer. Plus I'm retired when not taking care of my 93 year old mom I like to tinker to keep my mind busy.

[Earl K]

Brian,

For selling purposes I would pair the 908 drivers ( on 511b Horns ) with the A7s holding the 421-8H woofers.

That combination would then have all the highest power-handling components grouped together ( and could then be marketed as such ).

I also think it would be worth your while to remove the back-caps on the 806 & 802 drivers ( take some pics of the exposed diaphragms ) so that they might also be identified.

Some Altec diaphragm models are somewhat more preferential/desirable than others ( for HiFi purposes ).