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Heresy Tweeter BLOWN


imurelvis

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You probably don't need a whole new unit, just the diaphragm that includes the voice coil. It's a relatively easy soldering job. I did it many times decades ago when I fried the T-35s in 4 SK-horns (not to mention my hearing) with 600 watts of SS power in a mobile disco.

Go to the web address below and order a pair so that your speakers will match. Save the old good one for a spare.

http://www.simplyspeakers.com/12diaphragms.htm

ELECTRO VOICE 89486A DIAPHRAGM-ST-350, T-35, T-350

8 OHM

BEST SELLER! $29.00 $24.00

If you want to replace the whole unit, go to eBay and be prepared to pay more than $100.

Good luck

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  • 5 months later...

Ok... I might have a similar problem... I have a set of Cornwalls that sounded dull tonight, so I checked up close... and surely enough... one tweeter wasnt working. 8.gif It seemed to have stopped working with a very low signal, does this sometimes happen? Age? Bad x-over? Or some kind of spike?

1) I opened the rear, and disconnected the tweeter... and tested its resistance, and I got infinity.

2) I noticed that if I check the x-over, I get 4ohms at the woofer, 1ohm at the mid, and 1ohm at the tweeter... obviously if the tweeter was connected, I would have gotten the 1ohm too... right?

3) Now I wasnt sure if I should check it connected or not so I also tested it with a AAA battery to see if it had any reaction... and nothing. (woofer and mid made sounds)

4) Figuring that it was blown, I opened the unit to see if I could see anything unusual and it doesnt look dead, but should it show?

5) I noticed that the front horn, which came off when I unscrewed the back, was originally glued the diaphragm plate with a little bit of glue. Does this matter if it isnt attached by anything other than the screws? 15.gif

Ive got the K-77-M (with the square magnet), so should I just order the piece for the EV T-35 from Simply Speakers?

thanks guys...

Rob

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I had a pair of tweeter diaphrams replaced by Simply Speakers in Florida. They did both tweeters for $80 including testing and shipping.

I have built amps, speakers, pre-amps, but when I took one look at the flimsy little wires on the diaphram, I decided to let someone who has done this before do it for me. The few extra bucks was worth the chance that I'd ruin one.

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I agree with Cut-Throat.

Simply Speakers will test them both and repair them only if they require it.

They only work on K-77 tweeters not K-77-M.

The easiest way to test them is remove them from your speakers and hook them up too an amp. MAKE SURE THE VOLUME IS TURNED ALL THE WAY DOWN. Increase the volume alittle. They either sound good or not.

My test resulted in one was dead and the other one sounded scratchy.

Another nice thing about getting the originals fixed is if you ever sell them they have the correct part and part number in the speakers.

Danny

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Ok, I called www.simplyspeakers.com and ordered the 89486A DIAPHRAGM-(EV-350) K-77 Klipsch K-77 Diaphragm 8 OHM at $24.00 + shipping... Very friendly service... they said that it is quite common that they stop functioning due to "fatigue" and "age". I was worried about the fact that it seemed to have died with a relatively low signal... 12.gif

Although getting them refurbished was tempting, I didn't want to hassle with shipping the units from Canada... and he assured me it was an easy solder. I'm gonna give it a try, and post up on how it went.

I feel better knowing 1.gif Thanks guys...

Rob

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I repeat. It is a simple repair. In the old days, a call to EV in Buchanan, Michigan would cause fresh diaphragms (and voice coils) to arrive within days. Ev would then send a bill for about $11.00 each, if memory serves. Too bad those days are gone forever.

I bet that I repaired a dozen with no failures. Lest you think that the T-35s or the repairs were unduly fragile, understand that the same tweeters ('81 Heresys)that are at this minute playing jazz from a tube amp with ~11 watts/channel were never meant to withstand Disco, Boston, Foghat, Stones, etc. fed by 600 watts (300/channel into 4 ohms) of solid state power.

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To test a voice coil for continuiuty, you could use a digital multimeter or ...... you could take a penny, a nickle and some newsprint. Soak the newsprint in saliva and then sandwich the damp paper between the coins. The micro battery that you have created will produce a scratching sound from a tweeter (or woofer or squawker) when one lead is touched to penny and the other lead is touched to the nickle. This trick (taught to me by my grandfather)comes in handy when you want to verfiy that used speakers at garage sales, etc. do not have open voice coils.

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It is not that bad a project, assuming you can solder. I did it once.

It may be helpful to use a little nail polish to mark the orientation of the magnet, the intemediate structure, and the horn before you take it apart. Just so that things don't get turned 180 degrees. I noted some residue of paste which might work best if the reassembly is like the original.

Also, make notes on the stack up of any screen and cardboard rings. What goes where in which order. I always think I'll remember what I'm doing. Then there is a phone call or interuption and I don't remember.

There is the problem of making sure the plus end of the voice coil on the diaphragm gets connected to the correct terminal. It is mostly a matter of observing the orientation of the old one and the new one. There is a little red dot of paint on both, probably.

The voice coil is delicate. It is a cylinder of coiled wire. You'll be careful, I know.

To double check on the marking on the diaphragm and voice coil I took a very close look at the physical geometry of the winding. I don't recall specifics. However, you can see that one end comes off the side of the coil nearest the diaphragm.

I've not had to do it twice. If I have to do it again, I'll take pictures. We need a repair corner on this forum so our members are not first time tinkerers without the benefit of other's experience.

Gil

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I haven't yet received the replacement diaphragm but when it arrives, I'll do my best to document its replacement and post it online. When I disassembled the tweeter, it looked simple enough... just have to be careful not to damage the new one.

I'll keep you guys updated on my progress... 2.gif

Later...

Rob

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if you look carefully, I think you'll notice that the old diaphragm leads are very small and it's hard to see how to solder down in the recess where the terminals are. I was able to see on one of mine that originally there was a hole through the rivet that holds the spade terminal. the leads from the diaphragm were threaded through this hole and soldered from the outside. What I did was carefully drill a new hole wide enough for the lead of the new diaphragm which are flat like a ribbon instead of a tiny round wire. the center of the rivet is filled with solder which is very soft and easy to drill. On one of mine one of the rivets was a little loose, I noticed that on the other there was some epoxy so I bought some two-part epoxy and glued it after the soldering was done. Very easy deal and took longer to write than to do. Mine seem to sound fine, I paid about $40 for two diaphragms on ebay.

Does anybody else have a hard time typing the word "diaphragms"? 3.gif

Tom

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"Lest you think that the T-35s ...were unduly fragile (and) were never meant to withstand Disco, Boston, Foghat, Stones, etc. fed by 600 watts (300/channel into 4 ohms) of solid state power."

54 pcs of EV T35, 320 pcs JBL LE5-2 midrange, etc, fed by 26,400W of power via the 44 pcs 300W/ch into 8 ohms MC2300 SS McIntosh power amps.

http://website.lineone.net/~hintez/sound2.jpg

This was 1974, later more MC2300s were added.

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