Installation of the K-77, T-35 Diaphragm Kit

This kit is the only diaphragm with good performance I have been able to find to use in the Klipsch K-77M, K-77, and EV-T35 tweeters.  This is a high quality product developed for Klipsch and now that the OEM diaphragms are no longer in production, these are good replacements.

These are pretty easy to install and here I will provide a few pictures and instruction for installing them.

First, here are some instructions for the K-77M square magnet tweeters.  Same as the EV T-35 square magnet tweeters.

Take out the four screws from the back of the magnet assembly.


Separate the horn from the diaphragm mount.  You may need to tap it gently to get it to break loose.


Gently pry around the diaphragms housing to remove it from the top round plate of the magnet assembly.  Be gentle with this and try to get it to move up evenly all the way around.  If you mess up doing this step, the top round plate may come off of the magnet assembly. If that happens the pole piece will break loose and move to the magnet closing up the voice coil gap.  The tweeter could still be repaired, but how to do that repair is difficult and not really something I can describe well enough to get you through that repair.  I should also tell you at this point, sometimes that slipped pole piece has already happened and is the reason the tweeter is not working in the first place.  If that is the case, you did nothing wrong in the disassembly, you have just discovered the reason it was not working.

Anyway, let's proceed with how it should work.


Next, run something like a business card around the magnet gap to make sure it is clean.


The new diaphragm kit.  The black plastic housing may be a bit hard to get out of the protective plastic container.  Seems a bit of prying with something like a knife blade works best.  Holding on to the plastic while pushing on the back with thumbs work also, but tends to launch the new delicate diaphragm across the room.


If the old gasket and screen are stuck to the horn, peal them off.


This picture is an attempt to show you the tiny transit wire that runs up the side of the voice coil.  It is not all that easy to see, and was sure hard to take a picture of.  Anyway, the tiny vertical mark on the voice coil we can see in this picture is what I am talking about when I mention the transit wire.  This wire adds some thickness to the voice coil, so the magnet assembly has a notch (seen in the second picture below) that should match up with the transit wire to allow the extra clearance for the transit wire.


Place the gasket and screen in position on the new diaphragms assembly.


Fit the horn into the recess in the new diaphragm assembly.


Put the screws back in place through the magnet assembly and insert the magnet assembly in position on top of the new diaphragm assembly and horn.  Make sure the transit wire (discussed earlier) lines up with the notch in the magnet assembly.


Tighten the screws a little at a time in a criss cross fashion to gently pull the magnet assembly all the way down into the diaphragm assembly.  Try to have the two assemblies stay straight during this process.  You are inserting the voice coil into the magnet gap during this time and there is very little clearance.  Everything needs to stay straight.


If you have a meter, this is a good time to check the DCR of the new diaphragm's voice coil.  Should read around 6 ohms.


Most of the above will apply also to the K-77 or T-35 round magnet (alnico) tweeters with a few differences.


You may not be able to get the screen that is on the horn off.  So, if that is the case, just re-use the old screen and the new gasket.


Reassembly is like described above.


The old metal diaphragm housing likely had the wires soldered on to the terminals.  Those terminals were specifically made to have wires soldered to them.  I suggest that after the metal housing has been replaced with the new plastic housing, you should put some 1/4 inch slip on terminals on the wires to connect to the new terminals on the plastic housing.  The wires could be soldered to the new terminals, but it is very easy to  overheat the plastic during soldering and that would likely damage the new diaphragm assembly.


B & K Sound, 1925 East Gum Log Rd. Russellville, AR, 72802 phone-479-967-1542