Jump to content

k77f in k77d


rickysa
 Share

Recommended Posts

I have had my '09 khorns for a number of years and bought slightly used in the same year.  When I set them up, I was disappointed with the sound ("muddy", maybe) and rarely used them.   When recently setting them back up, I found out the tweeters were "blown"...no current passing across (infinite ohms).  I removed them, opened them and found a k77f faceplate (gotta learn how to resize images to post the pics).  Not unhappy with Klipsch at all, I'm guessing they are the same, just a different manufacturer? 

McIntosh MC 2500 amp and C34V pre-amp.

 

 

 

k77f (Medium).JPG

7E265CC1-97A1-4514-B26F-12BABCB6280C (Medium).jpeg

11430D7E-6B88-4DCC-9C8B-FA1987C0EB85 (Medium).jpeg

Edited by rickysa
Link to comment
Share on other sites

You can resize using MS Paint.  That is, if you're equipped for Windows.

 

Yes, the tweeter motors are the same but I'll leave a full explanation to others here who are more informed.  

 

I don't quite understand the issue with continuity.  Are you saying that testing at the terminals of the K-77's the voice coils are open?  The tweeters (all tweeters) are the most delicate of all the drivers.  The diaphragm and windings must be very light in mass and thus very thin wires are used.  They can only stand, at best, five watts continuous power.  

 

OTOH, there is no reason for them (both?) to fail while they're sitting in storage and not being played.  I expect there is more to the story.

 

WMcD

Link to comment
Share on other sites

You can also resize using the program in my signature.  Have been using it for years.  I take it that you measured across the terminals with the drivers disconnected from the crossover?  Make sure you have good continuity with your meter before measurement.  Sorry if this is obvious to you....

Link to comment
Share on other sites

Yes, but it is unlikely.  Most likely someone has been listening at extreme power levels, or introduced loud pops like dropped/skated needles or even fast forwarded CDs with the volume too high.  Something that sent too much power to the drivers. 

 

Which crossover  do you have.  AK-4s are complex and may require professional help testing them. 

13 hours ago, rickysa said:

can a bad crossover cook diaphragms?   repaired all the tweeters, now my k55x is dead one one speaker (tweeter still 3.5 ohms, mid range 3.5 Mohms)

 

 

Link to comment
Share on other sites

On 6/4/2019 at 8:47 AM, rickysa said:

I (gotta learn how to resize images to post the pics). 

 

k77f (Medium).JPG

7E265CC1-97A1-4514-B26F-12BABCB6280C (Medium).jpeg

200

 

I can't help you with the blown tweets and mid (that really sucks!) because it is above my pay grade but I can help you with the picture size.

 

You can use @jimjimbo's resizer and then upload photos.

 

Since your pics were already in there, I quoted your post to get access to them.  Now that I could see your pics, I double-clicked and could input values to resize them.  In the above pics I used 400 for the top one, and 300 on the bottom just to demonstrate what it looks like.  I like to use 400 pixels.

 

Link to comment
Share on other sites

Thanks for adding the early history before they were adopted into a good home.  Often speaker with problems get sold off.

 

Failures of Klipsch crossovers are quite rare although sometimes suspected.  OTOH if the K-77 is not properly hooked up to the crossover board so it has the benefit of the high pass filtering it is likely to blow because mid and bass freqs might be getting into it.  

 

The K-55 mid is a lot more robust and failures are rare.  K-33 woofers are even more robust but with 100 watt amps, bass control knobs, and loudness switches (which boost bass) there can be problems.

 

So, what to do.  (Some pedantry follows.  It is mostly common sense.  What I'm suggesting is probably more than is necessary but it is good practice to get to a point where you know everything is in good order rather than go poking around little-by-little.  This is particularly so if you can't have confidence in the initial condition.)

 

Please record the present status of things and make notes.  My rule is that my smart self today has to take notes to explain things to my stupid self tomorrow.  The main purpose here is to know where you're starting. Things may have been messed up by the previous owner and it is good to know that.

 

Take pictures of both crossover board connections, i.e. the collection of three pair of wires which go to the woofer, mid, and tweeter  (the fourth is to the amplifier of course).  We here would like to see the model number marked there, which is something like AK-3.  Trace the wires to the drivers, though you don't have to go into the woofer box.  You'll see the terminals are marked at a plate at the side of the plyboard crossover board.  Check which wires go where including the white with a red stipe.  Once you get the model number of the cross over board you can find the schematic in the technical section of the forum or someone will put it up here.

 

Now that we know where we're at . . . disconnect the wires from the screw down terminals on the crossover board and test for continuity.  [Edit: meaning measure with your ohm meter between the white and white - red wire  to each driver.  I'm not talking about the screws on the crossover board to which they were attached.]  The woofer will be a bit under 4 ohms and the other two up about 10 ohms. (ballpark).  If one is "open" check again at the terminals of the driver.  If open the diaphragm will have to be replaced.  While we're here, use a pencil eraser to buff the u-shaped spade lugs which go under the screws on the crossover.  I think it is not worth backing out the screws and buffing the metal underneath -- at least unless you see a corrosion problem.  

 

Put the wires back as they should be (rather than were) and snug down the screws.  Lack of good electrical contact at the screw down is very often the cause of unexplained, mysterious problems. Backing the screw off and snugging it down often cures things.

 

Do check the drivers for acoustic output with an improvised stethoscope, a paper towel roller.  Test one box at a time by disconnecting the amp connection or using the balance control.  

 

Let us know.

 

A final matter.  Depending on the circuit, running the crossover with no driver or an open driver attached can cause big problems.  Essentially, a second order high pass or second order low pass filter without a driver resistance attached turns into an LC series filter across the amp.  This creates a short circuit at the electrical resonance frequency.

 

WMcD

 

 

b

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...