Hookup advice for vintage Electro-Voice model EV-Four HORN MID/TWEETER to add to RW3

[Eric Mack]

I recently posted that I had found a design from Lee Sundstrum to improve midrange response by adding a tweeter horn to a Rodgers RW3 Speaker cabinet. The resulting discussion went in several directions, from re-purposing the RW3 as a subwoofer, to adding a new midrange and tweeter for better response. (I plan to pursue some of these options soon, Including attempting to build a Walker T3 cabinet using parts from an M10, but that is a different matter.)

Anyway, at the time of my post about Lee Sundstrum, I happened to find this EV-4 Horn (4"x10'') on eBay for $25 so I purchased it to experiment with. It arrived today.

For testing, I will use the horn outside of the RW3. Electrically, can I simply remove the existing JBL 075 bullet tweeter and install this in its place using the same crossover capacitor? Or, should I do something different?

Seller's notes: “Model: Electro-Voice E-V Four; Used in good working condition. Pulled from Vintage Allied/Knight Speaker”
eBay Link

[toodles]

No, you shouldn't just replace the bullet tweeter and install this is its place with the same crossover. The bullet is for fequency ranges of 2.5 kHz to about 15 kHz; this unit is probably good for about 500 or 800 Hz to about 4.5 kHz, though I couldn't find specs on this particular driver.

You should measure the resistance of this driver to estimate its impedance--a simple volt-ohmeter will work. It's probably either an 8 or 16 Ohm coil. An 8 Ohm coil will measure 5 to 8 Ohms, and a 16 Ohm coil will measure maybe 12 to 16 Ohms.

Then use a crossover calculator to find out what crossover will work for that Ohmage (use 8 or 16 in the calculator) at, say, 500 Hz.

[Eric Mack]

Thanks for the reminder, toodles. I was asking from an electrical perspective and had not considered the frequency aspects of this. I'll do some research to see what I can learn about the speakers cabinet that came from.

Update: Found brochure

[toodles]

You could always copy the midrange section of that EV crossover.

[Eric Mack]

Looks like you responded while I was updating my response.

toodles, I had forgotten that the horn device is actually the midrange! I was thinking of it as the tweeter, but now I remember you explaining that. The horn is: EV-4 horn midrange, 4"x10.5" opening, model # 14-1825-3618, Alinco Magnet Driver, 8 Ohms

I went searching. I could not find the specifications of the EV-4 midrange horn, but I did find a scan of the brochure for the EV “FOUR” speaker cabinet it came from that explains the mix and crossover. (Attached) I also found the spec for the ElectroVoice TC35 tweeter they used, though I will use the tweeters given to me from an HC-12.

The speaker brochure shows they used a 3-way crossover at 800 Hz & 3500 Hz, 60 Watts

So, I assume that means the designer felt this midrange would be optimal to cover 800-3500 hz, which fits nicely inside of your guess of 800-4500hz.

It appears, as best as I can tell, the actual model family of the horn is EV 1824. The horn is 8 Ohms.

I will take your advice and run it through a crossover program and see what it says. Then, I will compare that to what the brochure shows.

I'm enjoying learning. I ad no idea what this adventure would entail but it's been a fun journey

Thank you!

Eric


Additional information - no need to read, just keeping the research in one place for now.
I see the following component values for the 3-way crossover from the speaker brochure:
Capacitors: 0.50 uF, (2@) 1.0 uF, 4.0 uF (I could use a .47uF in place the the .50 uF)
Resistors: 5.6 ohm, 10 ohm, 47 ohm
Inductors: 0.56 mh

Not that it is relevant to my application, but perhaps useful to someone else, I found a forum post that said the following items were inside the ElectroVoice EV “Four” Cabinet:
Bass drivers, 12" with model # 810-3963 on the frame and 75421 on the cone.
EV-4 horn midrange, 4"x10.5" opening, model # 14-1825-3618, Alinco Magnet Driver, 8 Ohms
Tweeter, 5, model # 1824-3967 (Looks like they use a 10 ohm resistor to reduce power to the tweeter)