KLH 12 Recap Help

[awat]

Hello Klh Yogis,

I picked up a pair of KLH 12’s and I’m ready to recap them. I’ve recapped 5’s, 6’s, and 17’s so I’m pretty okay with the process.

Does anyone know the Caps that I’ll need, and any other information to help make these sing? At the moment they sound like crap - and it’s driving me nuts.

(I’ll be replacing the soundless tweeters with my back up/water-damaged 5’s. So glad I have that handy and that they’re the same parts.)

I can’t wait to hear them play loudly and beautifully. I’ll be driving them with a B&K AVR507.

Thanks for the help as always!

Adam

 

[audiojones]

Sooo, you’ve got the contour boxes with them, right? There’s a lot going on inside there, most folks say replace the resistors too. Don’t try to drive them without the contour boxes, there is no crossover in the cabinet like other KLH speakers and you’ll be sending full range power to whichever driver you hook up to. It’s all in the contour box. Often wondered if you could just use a pair of Model Five crossovers if you had Twelves without the boxes. Lotsa dual value caps in there, all the same crummy low quality ones that fail in all KLH speakers from the era.

Before and after photo of rebuilt contour box by JKent at Classic Speaker Pages:

 

[awat]

Sooo, you’ve got the contour boxes with them, right? There’s a lot going on inside there, most folks say replace the resistors too. Don’t try to drive them without the contour boxes, there is no crossover in the cabinet like other KLH speakers and you’ll be sending full range power to whichever driver you hook up to. It’s all in the contour box. Often wondered if you could just use a pair of Model Five crossovers if you had Twelves without the boxes. Lotsa dual value caps in there, all the same crummy low quality ones that fail in all KLH speakers from the era.

Before and after photo of rebuilt contour box by JKent at Classic Speaker Pages:
View attachment 2159565

Hi!

Thanks for the reply. I do have the contour boxes. Cool, I didn’t know everything was in there. What do I need to change out? Here’s a pic of one speaker: thank you!!!

Sooo, you’ve got the contour boxes with them, right? There’s a lot going on inside there, most folks say replace the resistors too. Don’t try to drive them without the contour boxes, there is no crossover in the cabinet like other KLH speakers and you’ll be sending full range power to whichever driver you hook up to. It’s all in the contour box. Often wondered if you could just use a pair of Model Five crossovers if you had Twelves without the boxes. Lotsa dual value caps in there, all the same crummy low quality ones that fail in all KLH speakers from the era.

Before and after photo of rebuilt contour box by JKent at Classic Speaker Pages:
View attachment 2159565

It looks like you replaced a whole lot in there. A bit intimidating, but I think I can make sense of it.

 

[audiojones]

Those aren’t mine, they are from JKent over at the Classic Speaker Pages website. Yes, looks like he replaced all of the resistors as well as the caps, did a really nice job too. I’d imagine it’s pretty much the same process as recapping any speaker with a “busy” crossover network, just take a good close look at the values of each component, write it all down and check your list against the actual components a few times before ordering. Size can be an issue here, so if there are any large value caps you might have to go with standard ‘lytics for them. I would replace everything else with good film caps (I’ve used regular old Dayton film caps in my KLH Fives, AR3a’s, AR5’s, AR2ax’s and pretty much everything else with great results).

Watch out for the dual capacitors (two individual capacitors in one housing) as there are a lot of them in there. One wire is common, one wire is value A and the other wire is value B. If it says 2+2uf that just means both values are 2uf. If it has two different values then the value of each lead is stamped on the capacitor where the lead connects to the body, same as in the Model Five.

I can’t recall what the recommended replacement for the stock sandcast resistors was, I’m not even sure I’d bother with them unless they are open or way out of spec. There may be a good reason for replacing them but I’m not sure what that is.

 

[Dswankey]

@RossW still is an active member maybe he'll pop in and share some advice

https://audiokarma.org/forums/index.php?threads/klh-model-12-recap.289132/

 

[RossW]

Ooh, another set of Model 12, there have been a few sets showing up lately.

I don't have a cap list, you'll need to read the labels off of what is in there. I believe most of them are dual-section caps, and they are probably all bad. It can be challenging to fit film caps for some of the larger values (I had to cut out some of the plywood), but even cheap bipolar electrolytic caps will be miles ahead of what was in there originally.

People like to crap on the square wirewound resistors, but they're reasonably reliable and I'm not convinced that new ones are actually higher quality. I'd check them for the sake of completeness, but unless they're off by more than 10% or so I'd leave them be.

Make sure you give the controls a good cleaning as well!

As far as the tweeter, the Model 5 is close, but not an exact replacement. If you're replacing both you'll probably never notice the difference, given how delicate KLH tweeters are (and how bad the caps tend to be) I'll bet most Model 12 don't have true M12 tweeters any more.

 

[awat]

Those aren’t mine, they are from JKent over at the Classic Speaker Pages website. Yes, looks like he replaced all of the resistors as well as the caps, did a really nice job too. I’d imagine it’s pretty much the same process as recapping any speaker with a “busy” crossover network, just take a good close look at the values of each component, write it all down and check your list against the actual components a few times before ordering. Size can be an issue here, so if there are any large value caps you might have to go with standard ‘lytics for them. I would replace everything else with good film caps (I’ve used regular old Dayton film caps in my KLH Fives, AR3a’s, AR5’s, AR2ax’s and pretty much everything else with great results).

Watch out for the dual capacitors (two individual capacitors in one housing) as there are a lot of them in there. One wire is common, one wire is value A and the other wire is value B. If it says 2+2uf that just means both values are 2uf. If it has two different values then the value of each lead is stamped on the capacitor where the lead connects to the body, same as in the Model Five.

I can’t recall what the recommended replacement for the stock sandcast resistors was, I’m not even sure I’d bother with them unless they are open or way out of spec. There may be a good reason for replacing them but I’m not sure what that is.

Thank you! I think I can crack this.

 

[awat]

Ooh, another set of Model 12, there have been a few sets showing up lately.

I don't have a cap list, you'll need to read the labels off of what is in there. I believe most of them are dual-section caps, and they are probably all bad. It can be challenging to fit film caps for some of the larger values (I had to cut out some of the plywood), but even cheap bipolar electrolytic caps will be miles ahead of what was in there originally.

People like to crap on the square wirewound resistors, but they're reasonably reliable and I'm not convinced that new ones are actually higher quality. I'd check them for the sake of completeness, but unless they're off by more than 10% or so I'd leave them be.

Make sure you give the controls a good cleaning as well!

As far as the tweeter, the Model 5 is close, but not an exact replacement. If you're replacing both you'll probably never notice the difference, given how delicate KLH tweeters are (and how bad the caps tend to be) I'll bet most Model 12 don't have true M12 tweeters any more.

Thank you so much for the insight. Whew...excited. I’ll most likely use the tweeters from my backup 5’s (so relieved that o don’t have to find new/used ones).

AudioKarma is something special. Thanks everyone. And please, any more insights you may have, please pass along.

Adam

 

[45rpmspinner]

Nice coincidence.
I was looking for something else and realized I have a caps list for Model 12s.
It's probably cribbed from another AKer. If so, my apologies to the original poster.
If it were me, I'd probably just use it to confirm what I see in the boxes.
2-50uf
1-3uf
3-4uf
1-16uf
That's per box.

As RossW mentions, 50uf film caps will be large [and possibly expensive].
One option is to parallel two smaller value [and smaller in size] film caps, or even a non polar electrolytic and a film, to get the 50uf value.

 

[awat]

Nice coincidence.
I was looking for something else and realized I have a caps list for Model 12s.
It's probably cribbed from another AKer. If so, my apologies to the original poster.
If it were me, I'd probably just use it to confirm what I see in the boxes.
2-50uf
1-3uf
3-4uf
1-16uf
That's per box.

As RossW mentions, 50uf film caps will be large [and possibly expensive].
One option is to parallel two smaller value [and smaller in size] film caps, or even a non polar electrolytic and a film, to get the 50uf value.

Thank you so much. O, the worry I had. I’ll be putting in an order right away. Thank you again!!!