Help with Alnico Mid-Range?

02County

AK Member
Hi - Looking for some help with something. I am feeling my way through speaker stuff so please bear with me - recently purchased some Knight speakers with what I think are EV speakers and drivers. Each has a woofer and tweeter that seem to work okay. When i put a multimeter against the terminals on both sets of tweeters and woofers, I get a strong signal.

But on both of the mid range, I get nothing from the terminals. Both Mid range speakers are covered by a heavy, 2.25 inch cast iron cover held in with four bolts. They have a number - EIA? - that starts either 825 or 1825. Haven't done anything beyond testing and measuring. Oh and one of the mid range cast-iron caps is covered in some yellowish corrosion, as are the L-pads on the crossover on that same speaker. Im about to order some deoxit -

Any help on identifying these things or guidance would be greatly appreciated. Thanks -
 

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Your photo is an OEM version of an EV T-35 diffraction horn tweeter.

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The magnet cover isn't cast iron, FWIW.
 
Hi Mhardy - Was hoping you would comment, you've been really helpful with this stuff. So that's a tweeter? Okay, do you know what the smaller driver is in this photo? It'd be at the top of the cabinet feeding the large cream-colored horn -

And is it normal that I can't get a response from the multimeter when I test the terminals?

What is the metal? Sorry for all the questions -
 
The "large cream colored horn" is most likely a midrange horn.
The smaller driver is the EV tweeter. The magnet cover is probably aluminum or perhaps steel (I am not sure if it is or isn't magnetic) -- the plating may be cadmium; the white dust may be cadmium oxide. I am just not sure!
The basket of the woofer is partially visible.

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If I had to guess, the MR horn and driver is probably similar to this one from an EV Four -- although this MR horn was plastic rather than metal.

EV4horn2 by mhardy6647, on Flickr

The MR horn and driver might be OEM versions of the 6HD or 8HD horn and the T10A or T25A driver, instead. You can find info on these at:
http://www.electrovoice.com/downloads.php?fam=236&title=Horn&d=1 (down at the bottom right) under "Engineering Data Sheets"
 

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Awesome, Thanks for the info. My attempt at posting a photo didnt seem to work so I'll try again - I think you might be right, the driver looks similar and the number serious on the horn is the same except the last seven digits are 3618 708 - the first digits are the same.

Lots to work with here - very much appreciated!
 
I think I've seen at least 3 pairs of these Knight-branded EV's on AK just this week. Those are a good score to find cheap. Those old alnico EV drivers are a find indeed.
 
... of course, I/we never answered your question! :p
The voice coils should show DC continuity (not infinite resistance) - I'd recommend disconnecting the crossover networks before measuring across each driver, just to be sure you're measuring the right thing. The DC resistance for each voice coil will likely be several Ohms. The other, easy way to check a driver is with a small battery (e.g., a C-cell, 1.5 volts) and a couple of clip leads. The driver will 'click' when the VC is energized with DC. Low voltage DC for a short time (momentary contact) won't hurt the driver.

Yes, that is an EV midrange horn and AlNiCo magnet compression driver. Your Knight speakers are similar to the original version of the EV Four -- however the Four, for whatever reason, used a cone tweeter instead of a horn. What you've got is essentially an EV/Knight version of the Klipsch Heresy (and they may well sound better than the Heresy of that era, as well).

FWIW, here's the innards of an EV Four -- although this one has a cheap replacement MR horn and driver (but that's another story...).

EV4innards by mhardy6647, on Flickr
 
Great. Thanks - Ill try the battery w/leads trick tonight. Very much appreciated! And stoked to hear that these things were a good buy!
 
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