Altec A7 horn

They arrived. The big, black enclosure in the overhead pic is an Altec A7 combination horn/bass reflex enclosure. It's being driven by a 15 inch Electro Voice EVM-15L series ll driver. I'm operating this horn in the 80hz to 400hz range. The blue tractrix horn sitting on top of the A7 carries all the upper frequencies above 400hz, while the tapped subwoofer (to the extreme right) carries everything from 80hz down.


This dusty old horn (and its left channel mate) was a gift from musician and fellow DIYer, Brian Kramer. He's trading these big bad boys to me in exchange for a pair of wedges (monitors) that he and his band can use--I also promised to assist him with his upcoming F5 amplifier project.


I've been extremely surprised by the quality of sound coming from the A7 enclosure. I would never have guessed that a short throw horn would be capable of such powerful dynamics. The best part is that they're very, very smooth. If you have a large room, a large system, and you're seeking decent bass/mid-bass/upper bass, then you must give this old classic due consideration.

I simulated the bass reflex response using WinISD. Notice that the Electro Voice EVM-15L driver is very efficient in this enclosure. What the graph doesn't depict is the fact that the horn adds additional efficiency to compensate for the bass suck-out and therefore matches the 60hz peak leaving the frequency response flat--and very efficient.

Hey Diyers, here's the A7 plans:

I modified these drawing to allow them to fit on this page and still be large enough to read. I also added an additional horn flair stiffener (dead center in the horizontal plane). I can't remember where I picked these drawing up, but wish to thank the author, whoever you are.


Honestly, I don't see how it can get any easier to get that sweet, smooth bass than to fabricate a pair of these horns.


Good luck and happy listening...