KLH Model 5 midrange production yr differences

[Brad1234]

Hi All, I am restoring my second pair of Model 5's and after finishing them, the mids sound a lot different from my older pair and have been trying to figure out why. The first pair I restored have lower numbered silver-colored sticker SN's and date stamped 1968, so I assume they are older than the second set I restored with higher #'s and paper sticker, let me know if that is wrong?
 

At first I thought the sound difference was the different inductors on the newer xovers making the mids in the newer restored pair sound much lower in frequency (new caps are exactly the same on both xovers). But I swapped the mids between older and newer restored pair and the mids still sounded lower in frequency in the older pair, so the sound difference is the actual mid speakers. The older mids are silver in color and date stamped 1968 on back. The newer, lower frequency sounding mids are goldish colored. Anybody know if this is a normal thing for the goldish colored mids to have a different sound over the silver ones?  I know this is a weird question, but just seeing if any of you KLH experts have noticed this too?  I included photos of the 2 different xover networks and the new (goldish) mid vs older (silver) mid speaker side by side. 

[Brad1234]

Update on this post, I think I figured out the issue I have been having with my Model 5's, it is my Marantz 2270 receiver, it needs a recap. The mids coming out of it are not sounding right. After switching receivers, the 2 pairs of Model 5's sound more similar to each other, but the new gold colored mids do have a slightly lower frequency response than the silver ones, but both sound good. 

[JKent]

Glad you figured it out. They should sound the same. KLH used this driver, called the "Twelve point five" (I don't know why) in MANY speakers. It was the full-range used in later Model EIght radios and all Model Twenty-Ones. It was the mid in the Fives and the Twelves (maybe that has something to do with the name) and was used full-range in various compact systems such as the Eleven (suitcase) and Eleven W. They were used in pairs for the Fourteen, Fifteen and Nineteen speakers. In short, there are thousands of them.

Maybe take a look at the Service Manual #60 in our library. It says all KLH woofers and the 12.5 drivers should have the skivvers (surrounds) re-doped whenever the speakers were presented for service.

Kent

PS: Here's the link http://www.classicspeakerpages.net/library/klh/other/klh_schematicsservice/klh_service_bulletin_60.pdf

PPS: Get some of Roy's sealant dope from Vintage-AR and apply it to the woofer surrounds. It makes a BIG difference on the Model Fives.

Edited January 17 by JKent
added PS and PPS

[Brad1234]

15 hours ago, JKent said:

Glad you figured it out. They should sound the same. KLH used this driver, called the "Twelve point five" (I don't know why) in MANY speakers. It was the full-range used in later Model EIght radios and all Model Twenty-Ones. It was the mid in the Fives and the Twelves (maybe that has something to do with the name) and was used full-range in various compact systems such as the Eleven (suitcase) and Eleven W. They were used in pairs for the Fourteen, Fifteen and Nineteen speakers. In short, there are thousands of them.

Maybe take a look at the Service Manual #60 in our library. It says all KLH woofers and the 12.5 drivers should have the skivvers (surrounds) re-doped whenever the speakers were presented for service.

Kent

PS: Here's the link http://www.classicspeakerpages.net/library/klh/other/klh_schematicsservice/klh_service_bulletin_60.pdf

PPS: Get some of Roy's sealant dope from Vintage-AR and apply it to the woofer surrounds. It makes a BIG difference on the Model Fives.

Thanks Jkent for the post!  I made sure to dope all of the drivers when restoring them with VintageAR sealant. They look so beautiful all shiny and freshly doped!  I did add a second layer to the mids just to see if it helped, I think it may have but hard to tell. When I push on one mid the other mid moves up, so they are pretty well sealed.
 

Question, how often do they need to be redoped?  My other Model 5's were doped about 8 months ago and their mids look a little dry, so I was going to add another coat to them too. The woofer looks ok though. Maybe that will help with the difference in sound between mids. 

[JKent]

Hey Brad

I think the new dope should last a long time, like decades, but Roy would be the one to answer that question with any authority. 

[RoyC]

On 1/17/2023 at 11:23 AM, Brad1234 said:

Question, how often do they need to be redoped?  My other Model 5's were doped about 8 months ago and their mids look a little dry, so I was going to add another coat to them too. The woofer looks ok though. Maybe that will help with the difference in sound between mids.

Previous sealant applications (including the original treatment) do not go away with time, and adding more can result in too much. If your woofer returns relatively slowly when gently pushed inward, it does not need more sealant. Appearance is not a good indicator of the need for additional sealant.

Roy