Electro-Voice Interface 1 Series II

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Hi all,

I picked up a pair of Electro-Voice Interface 1 Series II speakers today. However, they sure don't look like Interface 1's:

According to the images I can find on the Internet, they look just like an Interface 2 or 3, but here's the back of the speaker:

Huh. I have a minor mystery on my hands. Anybody have any input they can provide?

Also, does anybody have a story behind the foam on the tweeters? I'll take photos of the other speaker as soon as I can - tonight is busy as heck - because that speaker still has some of the foam on it. Is this replaceable and/or needed?

Thanks for your contributions!

[Steve F]

Hi all,

I picked up a pair of Electro-Voice Interface 1 Series II speakers today. However, they sure don't look like Interface 1's:

According to the images I can find on the Internet, they look just like an Interface 2 or 3, but here's the back of the speaker:

Huh. I have a minor mystery on my hands. Anybody have any input they can provide?

Also, does anybody have a story behind the foam on the tweeters? I'll take photos of the other speaker as soon as I can - tonight is busy as heck - because that speaker still has some of the foam on it. Is this replaceable and/or needed?

Thanks for your contributions!

They Look like Interface I's as I remember them. I seem to recall the 2 as a much bigger speaker.

Yes, I know the tweeter story quite well, and I thought it was extremely clever on E-V's part:

The IF-I is a 2-way speaker--woofer, PR (a "vent") and tweeter.

2-way tweeters are usually compromises if they cross over at a low enough frequency to relieve the woofer from severe beaming. If the tweeter crosses over at, say, 1000Hz, instead of the typical 2-way tweeter x-over of 3khz or so, then the tweeter will have to be large enough to be able to respond down at so low a frequency.

But a large tweeter will itself start to get severely beamy by around 7kHz, and that's no good either. A large tweeter solves the 8" woofer beamy problem, but introduces the tweeter beaming problem.

Yet the mfgr doesn't want the expense, mfg complication, etc. of a 3-way speaker.

What to do?

EV did this: The foam around their 2" (I think) tweeter had a 3/4" circular hole cut in the center. EV claimed that the foam was acoustically transparent at the low end of the tweeter's operating range but became progressively more and more acoustically opaque with increasing frequency. Thus at the very highest frequencies, the tweeter had an effective radiating diameter of only 3/4"--providing very wide dispersion at the top end, but retaining the advantages of a larger tweeter's ability to respond and handle power in the lower frequencies.

Very clever engineering. I don't know if any independent test reports ever verified the foam's claims one way or the other, but the idea and its marketing presentation were great.

Steve F.

[hatchiebird]

The speakers shown are interface II's. I have a pair that I bought in 1980 that I recently refurbished. I used 1/2 inch foam for the tweeter.