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T-35 diaphram-How to match 16 ohm to 8 ohm version.

DaWoofer

DaWoofer

Super Member
I bought a replacement diaphragm for my T-35. It is apparently a 16 ohm. The only version available cause there wasn't a selection for 8 or 16. It seems that my original was 8 ohm because this new one is less dynamic or lets say lower in volume on the cymbals in music. These are in a 78 or 79 Heresys with the E-network crossover. Is there any way to rectfy this situation by changing the componants in the crossover. I would love to bring the dbs up in the replacement diaphragm. Any input is highly welcomed.
 
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Well, I peeked inside the Heresy again. There sure aint much you can do to that crossover as there is few parts in there. I wired the diaphram and I think polarity wise I could of reversed the polarity. That will be my first attemp to correct this problem. Lets hope its that simple.
 
Well, I switched tweeter from one cabinet to the other. Its in the crossover on the cabinet. The tweeter that was low sounds bright in the other cabinet. I guess its time for that crossover upgrade. Any Klipsch fans have a preference in brands for these big caps? Opinions and experience in this upgrade is welcomed from all you wise people. And I know this is one place where I've always got great advice and I highly regaurd it as such!
 
DaWoofer said:
Well, I peeked inside the Heresy again. There sure aint much you can do to that crossover as there is few parts in there. I wired the diaphram and I think polarity wise I could of reversed the polarity. That will be my first attemp to correct this problem. Lets hope its that simple.
Click to expand...

The red mark on the diaphragm is installed to line up with the notch in the magnet assembly. The lead closest to the red mark is positive.

Bob Crites
 
Not likely that a bad cap would cause the voice coil to fail. Usually bad caps just attenuate the highs. The diaphragms fail for any number of reasons including most often just old age. There is often no way to identify the cause of a diaphragm going bad.

Bob Crites
 
By the way, I switched the polarity on that tweeter before I switched the two and it made no noticable difference in output. Would the bad cap cause the output to be lower in that tweeter?
 
That is most often what we see as caps go bad in a crossover. They increase in ESR which makes them look like a resistor and a capacitor in the circuit. That increase in ESR attenuates the signal to the driver.

Of course normally I see the caps age about equally between the two crossovers and it is not as noticable as your experience. You should also check the connections on the crossover and loosen and retighten all the screws on the crossover terminal stirp in case you have developed a bit of corrosion on one of the terminals.

Bob Crites
 
DaWoofer said:
By the way, I switched the polarity on that tweeter before I switched the two and it made no noticable difference in output. Would the bad cap cause the output to be lower in that tweeter?
Click to expand...

By the way, you set the polarity on those tweeters by the way you install the diaphragm regardless of the way the body might be marked. The red mark has to go lined up with the notch in the magnet assembly. It indicates the place that the voice coil winding is wider because it is where the wound wire travels back up the side of the voice coil. The notch in the magnet assembly allows clearance for this thicker place on the voice coil. You will have a "rub" if you don't install it properly.

Bob
 
Dawoofer,

The E network has a 2 uF cap connected right to the tweeter. In theory, you can impedance-scale a filter by 2 dividing the caps by 2 and doubling the inductors. Since there are no inductors, all you need to do is put a 1 uF in place of the 2 uF that's there for a 16 Ohm tweeter. This will hold the crossover at the same place. You will also need to move the other side of the new 1 uF cap up one tap on the transformer, from 3 to 4. This should let you use a 16 Ohm tweeter at the same level. Try it. I would like to know if this solves the problem.

Al K.
 
Al,

Read what he said up above.

"Well, I switched tweeter from one cabinet to the other. Its in the crossover on the cabinet. The tweeter that was low sounds bright in the other cabinet. I guess its time for that crossover upgrade. Any Klipsch fans have a preference in brands for these big caps? Opinions and experience in this upgrade is welcomed from all you wise people. And I know this is one place where I've always got great advice and I highly regaurd it as such!"
 
Bob,

Ok.. I just got to thinking about the possibilites of using a 16 Ohm tweeter and investigated the idea. I agree he needs a cap fix. The right tweeter always helps too!

Al k.
 
Al,

I think he probably has an 8 ohm. He was wondering if he might have gotten a 16 ohm instead of an 8 ohm diaphragm installed. That is unlikely because the 16 ohm ones are really rare (unless he got it from me). And I don't remember selling him one.

Bob
 
Bob,

Yep.. I haven't heard of a 16 Ohm version in a long time. I just got a brain-blocking flash about the 16 Ohm possibility and jumped into tinking about the possibility and forgot about the original question!

Al k.
 
Bob Crites,

I am new to the forum and found this thread in search of information to replace the open 16 ohm phenolic diaphram in a vintage chrome EV T-35. I have only been able to find 8 ohm diaphrams, and I would prefer to go with the original impedance if possible and affordable. It is a very nice heavy piece of art and and history and sounds pretty darn good too! I have taken the driver carefully apart but have not removed the open VC/diaphram assembly yet. I cannot tell what the centering mechanism is so I am reluctant to remove the diaphram, although it may become aparent once I do. Still being cautious. Any input will be greatly appreciated.

Chris Bolkan
 
Chris,

I can supply the 16 ohm diaphragms to you.

The difficulty of diaphragm installation depends on how old the tweeter is. The very early ones had a sort of "diaphragm sandwich" of thick gaskets that center the diaphragm. To replace the diaphragm in one of those, you have to carefully separate out the old gaskets and remove the old diaphragm. Then you have to glue in a new diaphragm centered very precisely so the voice coil ends up in the center of the magnet gap. This is very difficult.

Newer tweeters (after sometime in the mid 60s) the front of the tweeter (the diaphragm housing) has a machined groove in it that centers the diaphragm and only a single gasket on the magnet side. That type is much easier to rebuld.

One option for the older type of T-35 that used the "diaphragm sandwich" is to replace the front of the tweeter, with a new plastic front that has the newer type centering groove. That makes the tweeter look different (black plastic diaphragm mount rathe than metal) but it probably works better than it ever did before.

Bob Crites
bobcrites@mac.com
 
Hi Bob,

Thanks for the reply!

Yeah that is what I was afraid of. The tweeter is an early EV T-35, 3 piece all metal, all chrome, except the magnet which is painted a sort of factory off red color with a nice label on the back. It has sandwitch gaskets alright, and I can't see how they effectively center the diaphram to be honest with you. I am very mechanically and electrically inclined, but seeing what I saw when I opened it up concerned me. I figured they must have had some way to do it in a repeatable fashion when it was manufactured. Probably some sort of assembly fixture or jig.

I would like to keep the original configuration because it is in mint physical condition and I am sure has some vintage value and appeal simply for what it is. The label states 16 ohm which is the only reason I care about the coil impedance. I might have a go at it if the diaphrams aren't too expensive. I only need one if I can get it right the first time! Please let me know if you think it is a waste of time to try.

You can email me off line with the price and I'll see if I am willing to make the gamble I can succeed. Also let me know if you have a jig or something made up to assist in the placement and how much you would charge to install it. It seems such a shame to scrap this beautiful little tweeter if I can avoid it. I don't know if it died of old age or what, but I did NOT have protective back to back Zeners across the voicecoil. I will from now on if I can fix it.

Email addy below.

Chris Bolkan
Luv2Boat@clearwire.net
 
Chris,

Yes, I figure the factory had a jig to do the diaphragm centering. The jig would be rather like the magnet assembly of the tweeter. Where the four screw holes are would be dowel pins exactly the size of the screw holes in the gasket. Then the diameter of the outer circumference of the magnet gap would be decreased to exactly the size of the outer diameter of the voice coil.

Then you could just put it together. The first gasket would go on over the dowel pins. Then the diaphragm would be placed in position and glued to the first gasket. Next the second gasket would be placed over the dowel pins and glued in place.

After the glue dried. you could pick up the complete "diaphragm sandwich" and install it in any of the tweeters.

Problem is that the jig would cost a couple of hundred to have it made and the new gaskets would cost a few hundred to have the die made to stamp them. I have been arguing with myself for years about whether or not having those things made would ever pay off. I even ordered the gaskets once to get the process started but that gasket place after a few months decided they could not make the die for them and in the mean time lost my set of gaskets I sent them. I might try it again with another gasket company if I can ever get another good set of the gaskets to send in.

In theory, at least, if I had the jig and the new gaskets, I could build up a diaphragm and gasket combination already centered properly and sell it as an easy (relatively) to install pack.

That woud take care of the 16 ohm T-35s. Then of course there is the 16 ohm T-350 that would require another jig and different gaskets.

Bob Crites
 
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