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I picked up a pair of old beat up EV monitors, and in them were a pair of EV 1829 compression drivers. They appear to have 1 1/4 inch ID outputs (1 3/8 threaded OD), with an additional 1 1/4" threaded output on the back as well. As received the rear output was plugged with foam and a red plastic cap, similar to as shown in the pictures on the auction site.
A little research shows these drivers were designed for reentrant or diffraction horns, and are sometimes used as replacements on Leslies. In their intended horns the claimed FR can be 140hz to 11,000hz.
Does anyone have experience with these? If attempting a hi-fi application should they be run with the back capped?
Thanks,
Gary
Follow Ups:
I've seen them really dirty looking and still function - EV's CDP (Compound Diffraction Projector) horn must go back over 60 years and is still in production. I think they were in EV's "Georgian" (?)BTW, Eminence's coaxial line with horn uses a horn almost identical to that on the CDP
Eminence 12cx
Karlson Evangelist
Edits: 12/09/15 12/09/15 12/09/15
Gary,
Yes, the cap is required if not using a horn on it. If the foam is not in good condition replace it with felt, without foam or felt the back wave will reflect back into the diaphragm and response will not be as smooth.
Brought back memories of Freedom Electronix (minneapolis) monitors from around 1974...
In acoustic lab work there is occasionally a need for a driver which produces no back wave, requiring an anechoic termination. Basically a muffler with flat response.
The most outrageous of these were brutally simple - a very long tube, which would transmit an acoustic wave without generating reflections. The air friction at the tube surface gradually attenuates the traveling wave until there's nothing meaningful to reflect at the final end. I seem to recall lengths of 100 feet, but that's a dim memory.
"The best cheap 1" horn is probably the Community SRH 90.I made a system using this horn with an EV 1829 paging horn driver and it was +/- 1dB from 500hz ~ 6.3khz,add a tweeter and you are done."
EQ was used in the network.
I have the rectangular paging horns that these are used in.
One side of the driver runs the large bell horn, the other side
has a small horn on it, facing forward. Neat design I thought!.Rather than foam, I'd stick a cotton ball in the plastic cap
and you're good to go. Foam can crumble.
Edits: 12/08/15
why not try it with dipole horns? I would think a very tight set of polar's on the front horn and a wide set of angles on the rear horn, give you that very cool spatial quality people love about dipole planer loudspeakers. By the way Karlson K-Tubes would be worth trying for this since they are 1/4 wave resonant devices you will end up with very compact units, but you won't be able to control the polar patterns as tightly as you could do with horns. Have fun. Best regards moray james.
moray james
A few decades ago I saw a system-of-the-month article in Stereo Review where this guy had moved into a large loft space. He had some unremembered large floor standing box speakers which were intended to be mounted near a wall, however they were going to have to be placed away from any walls in the loft. So he bought another pair, placed them back to back and reverse wired them, and he discussed how he felt this was better than original pair. I was'nt happy with the very narrow sweet spot I had with my EV horn rig at that time, so inspired by the article I got some Motorola peizos out of the junk box and gator clipped them in as rear firing tweeters to compliment the T350 front tweeters. And there was an improvement. Next came some better T35's swapped in for the rear firing tweeters. Next came rear firing mid horns and compression drivers, and this was better still. The 1829/1828 drivers would allow just one driver in this position however. Next came extra woofers driving rear firing mid bass horns to compliment the front bass horns. Even better still. At his point I'm reminded of a Bermuda Triangle legend where a lost pilot supposedly radio'd "Don't come after me! They look like theyre from outer space!".
Paul
I do have some home made k-tubes I could stick on them...Oh, hey, another nice surprise: The horns are University 8HDs. Unassuming looking but good down to 800Hz!
Edits: 12/10/15
B
If you're going to use the 8HD's as the front firing horn, try them with the long mouth dimension in the vertical position. While it may seen counter-intutive, they are diffraction horns and will have a broader coverage horizontally set up this way. I was ignorant of this and I had used them with the long dimension horizontal because they fit that way in my rig, and I never did care much for them. Freddy is the go-to-man for K-tubes. I tried some cardboard mock ups once, but found them rather beamy. They could work in the rear firing position.
Let us know how it goes
Paul
Quick update: Tried the drivers and (vertical) horns together using a passive crossover at about 1,100 Hz ('cause that is what I had handy). Sounded pretty good in the midrange but grainy up top. I'd like to try them down to about 800 Hz, then crossed to another driver above 3K or so, but don't have a crossover that will do that. I am getting closer to being able to tri-amp but not quite there yet.
Haven't tried the K-tubes on the back yet but will report back.
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