KLF-20 tweeter (K-79-K) suddenly dead after working on the speaker. Replace diaphragm?

[adam2434]

So, I’ve been working on a pair of newly-acquired KLF-20 (reinforced all interior cabinet joints with heavy construction adhesive, added front-to-back braces, replaced electrolytic cap in woofer circuit) and got the speakers put back together yesterday.

 

Fired them up yesterday and one tweeter is completely dead.  I removed the dead tweeter and tested it by itself with a 7000 Hz test tone and there is zero output.  I don’t know how a tweeter could die from simply removing it and reinstalling it in the cabinet.  I’m a bit dumfounded on this. 

 

How could this happen?

 

So, I guess the diaphragm went bad somehow and I’ll replace the diaphragms in both tweeters so they match.

 

Simply Speakers has fabric and titanium replacement diaphragms for the K-79-K tweeter (links below).

 

https://www.amazon.com/Klipsch-Replacement-Titanium-Speaker-Diaphragm/dp/B00DX7DXHE

 

https://www.amazon.com/Klipsch-Tweeter-Diaphragm-127103-others/dp/B00DX7DSFQ/ref=pd_lpo_2?pd_rd_i=B00DX7DSFQ&psc=1

 

I think Crites also has a titanium diaphragm that works in the K-79-K tweeter.

 

Any advantages to any of these diaphragm options?

 

Also, I am curious in general about how a replacement diaphragm could change the frequency response or sensitivity of the tweeter vs. the original diaphragm.  I mean the replacement diaphragms are different materials and the domes are probably different weights vs. the original. 

 

Wouldn’t this impact how the tweeter functions in terms of frequency response and sensitivity?

[OO1]

Klipsch sell the Factory klipsch Titanium diaphragm.  same diaphragm used in Pro speakers with 2x the power rating 

▶️  https://support.klipsch.com/hc/en-us   

 

recheck your tweeter , take the diaphragm out , clean the VC area of the driver  or blow compressed air in the VC  gap ,  and  check the DCR of of both diaphragms   , if it's open , you'll see it right away , if it's not , then , the diaphragm is ok 

[adam2434]

I did not take the tweeter apart, but the bad one has no resistance value across the terminals.

 

The working tweeter measures around 9 Ohms across the terminals.

[Woofers and Tweeters]

2 hours ago, adam2434 said:

Any advantages to any of these diaphragm options?

Just a couple of weeks ago, I replaced the stock diaphragms in a pair of K792 (K79) in a pair of KP362. At the same time, I replaces a pair of tweeter in a second pair of KP362 with Dave A's L-MAHL. I did this so I could AB the two sets. This isn't the first time I have ABed the L-MAHL to other tweeters and have always liked the L-MAHL a lot better and this time I had the same results. 

[adam2434]

20 hours ago, RandyH said:

Klipsch sell the Factory klipsch Titanium diaphragm.  same diaphragm used in Pro speakers with 2x the power rating 

▶️  https://support.klipsch.com/hc/en-us   

 

 

So, Klipsch sells a replacement diaphragm that works specifically with the K-79-K tweeter in the KLF-20?

 

If so, happen to know the part number for that?

 

I also sent Crites an email with some questions on their titanium diaphragm - waiting to hear back from them.

[Dave A]

It can be easy at times to break that tiny little lead wire from the spade end connection. You pull and wiggle to get the lead off and can break that wire if the spade end swivels to much. Some of those rivets are not done real well. Bending the leads getting them in and out can also do this so be careful when you fiddle with these.

 

  The Ti diaphragm will not sound the same as the OEM phenolic one did. Simply Speakers sells a phenolic diaphragm for these. Klipsch Replacement Speaker Diaphragm K75, K76, K78, K79, 127103, D-417  Klipsch may also sell the phenolic ones too and I have never checked to see.

[adam2434]

1 hour ago, Dave A said:

It can be easy at times to break that tiny little lead wire from the spade end connection. You pull and wiggle to get the lead off and can break that wire if the spade end swivels to much. Some of those rivets are not done real well. Bending the leads getting them in and out can also do this so be careful when you fiddle with these.

 

  The Ti diaphragm will not sound the same as the OEM phenolic one did. Simply Speakers sells a phenolic diaphragm for these. Klipsch Replacement Speaker Diaphragm K75, K76, K78, K79, 127103, D-417  Klipsch may also sell the phenolic ones too and I have never checked to see.

 

Interesting - I looked at the wires and solder on the spades under magnification and I can't see any break in the wires or anything else amiss.  The spades are solidly mounted too - don't move if I try to wiggle them.  I could try to reflow the solder on the spades for kicks - can't hurt anything since the tweeter is dead anyway.

 

I've read that the stock tweeter diaphragm on the KLF-20 is a shiny black polymer dome.  That Simply Speakers diaphragm has a treated fabric dome per their description.  They are cheap enough that I can easily give those a try, but I am also open to other options like a Klipsch or Crites diaphragm.

 

[Dave A]

I thought the K-79 was supposed to be phenolic and in looking at a set of K-79's I have in the shop it looks like the Simply Speakers material. Phenolic by definition is cloth impregneted with synthetic resin. I have cut some a half inch thick in the shop but the same material in one layer of fine cotton cloth would be the same just thinner. I assumed since you mentioned the K-79 that is what the KLF-20 uses.

 

 I see just now in further search though that the K-79 in the Chorus is listed as phenolic and the KLF-20 which also has the K-79 has polymer. So for what it is worth regarding polymer vs Ti I prefer the polymer in 1" diaphragms and find the Ti to be tinny and a bit harsh to my ears. I have no knowledge as to why they used two different materials here on the Klipsch diaphragms.

[adam2434]

Well son of a gun - I think I fixed the bad tweeter!

 

I reflowed the solder and added a bit more to the spade tabs, and the bad tweeter works now.

 

Both tweeters measure exactly the same (9.1 Ohms) across the terminals, using my cheap multi-meter.

 

For further confirmation, I ran test tones from 5,000 to 12,000 Hz with both tweeters in the exact same place relative to my Radio Shack digital SPL meter.  There are some significant differences between the tweeters, but I don't know is this is typical or indicates an issue with one of the tweeters.  The results are below. 

 

Any thoughts on this?

 

Frequency     Good Tweeter SPL (dB)     Bad/fixed Tweeter SPL (dB)

5,000 Hz                    84                                81

6,000 Hz                    85                                85

7,000 Hz                    85                                84

8,000 Hz                   81                                 79

9,000 Hz                   79                                79

10,000 Hz                 75                                 75

11,000 Hz                  69                                68

12,000 Hz                  67                                67

[OO1]

Klipsch introduced The  2nd gen  polymer diaphragms  for their  Factory tweeters with the advent of  Ferro-fluid  which allowed for cooling of the VC , better sonics and enhanced durability ,. 

[OO1]

klipsch  k-79 tweeters /diaphragms are proprietary --

[OO1]

3 hours ago, adam2434 said:

  There are some significant differences between the tweeters, but I don't know is this is typical or indicates an issue with one of the tweeters

no worries 

[Dave A]

3 hours ago, adam2434 said:

Any thoughts on this?

Yes, put it back in and run them. Save your money if you liked how they sounded to begin with.

[OO1]

yep-

[adam2434]

3 hours ago, Dave A said:

Yes, put it back in and run them. Save your money if you liked how they sounded to begin with.

 

Yeah, already did that and they sound fine.  

 

Honestly, I did not listen to them very much before I started working on them (I just got them a couple weeks ago).  Basically, I just wanted to get them in good shape and ready for another 25 years of service for when I give them to our son for his man cave someday.

 

Thanks for the "lead" on the potential lead issue.  That led me to the idea of resoldering the spade tabs, which apparently fixed the issue.

[Rolox]

On 4/2/2022 at 5:23 PM, adam2434 said:

So, I’ve been working on a pair of newly-acquired KLF-20 (reinforced all interior cabinet joints with heavy construction adhesive, added front-to-back braces, replaced electrolytic cap in woofer circuit) and got the speakers put back together yesterday.

 

Fired them up yesterday and one tweeter is completely dead.  I removed the dead tweeter and tested it by itself with a 7000 Hz test tone and there is zero output.  I don’t know how a tweeter could die from simply removing it and reinstalling it in the cabinet.  I’m a bit dumfounded on this. 

 

How could this happen?

 

So, I guess the diaphragm went bad somehow and I’ll replace the diaphragms in both tweeters so they match.

 

Simply Speakers has fabric and titanium replacement diaphragms for the K-79-K tweeter (links below).

 

https://www.amazon.com/Klipsch-Replacement-Titanium-Speaker-Diaphragm/dp/B00DX7DXHE

 

https://www.amazon.com/Klipsch-Tweeter-Diaphragm-127103-others/dp/B00DX7DSFQ/ref=pd_lpo_2?pd_rd_i=B00DX7DSFQ&psc=1

 

I think Crites also has a titanium diaphragm that works in the K-79-K tweeter.

 

Any advantages to any of these diaphragm options?

 

Also, I am curious in general about how a replacement diaphragm could change the frequency response or sensitivity of the tweeter vs. the original diaphragm.  I mean the replacement diaphragms are different materials and the domes are probably different weights vs. the original. 

 

Wouldn’t this impact how the tweeter functions in terms of frequency response and sensitivity?

Happened to me once with a Beyma CP25. Took all drivers out to repaint the box, put the drivers back in, one of the tweeters was dead. Had to order some replacement diaphragm. Still a mystery to me!