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KLH 12's - another hole in my KLH collection filled . .

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Hello to all, I've been reading the posts on the model twelves, I know it has been a while since anyone was here but I'm finally out of the hospital to ask any/all of you if anyone can help me. I lost my hands and was severly burned in a work accident in 1997, I haven't lost my love of music or the old school stereo equipment and the great quality sound they still have, my problem/blessing is that I now have 4 KLH Model 12 speakers and 6 crossover boxes, I live in Colorado Springs and I just left the local high end stereo shop where the guy couldn't fix my Marantz 150 tuner so I took the boxes and the new caps to him and he told me it was all " hard wiring and labor intensive " in other words he is too lazy to deal with it unless its a pcb replacement, my question I'm putting out is....can anyone help me re-cap these or does anyone know someone who would be willing to help me out, my sons are in California and Oregon and they helped me get all the drivers squared away but they can't break free again til late summer to help with these crossovers, I'm very willing to pay for the time spent working on them, I will be watching to see if anyone responds, Thanks, Robert :rolleyes:

Hi Robert;

Sorry about your accident.

Kent has previosly posted his before and after cap mods to his own KLH Twelve Contour Control boxes.

Quality workmanship can be seen in his work.

Thank goodness no one needs to haul all 4 speaker enclosures around, Heh?

Kent, on the inner mounting plywood board, at the top at about 1:00 o'clock is a penciled serial number, 3 or 4 digits, please, Kent, list if doing the mods, please.

Also Robert, please provide Kent with the speaker enclosure serial numbers off the rear of the enclosures.

This is just to determine the number of KLH Twelves manufactured and possibly even a date from the caps or resistors or drivers.

There is virtually no information about production numbers or mods from most manufacturers.

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Dan, I'll get the numbers to you one way or another, as you know they're big and heavy so I'll see if I can tip them forward and then have my caregiver read them, hopefully they are there!!! One pair came from AudioClassics, the others I found separately, one from Buffalo and one from Detroit. The latter 2 I'd be surprized if they were there, anyway, give me a little time and I'll see what's there, Take care, Rob

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Hi Vern, I can still relay these numbers to Kent but since you wanted them I'll post here, As mentioned before I have 4 Model 12's, The ones I bought as a pair are 003708 and 003711, of the other two only one has the sticker and it is 00475, I looked again to make sure of that and that one only has 5 digits instead of 6 , Also I have the back plates that came from a pair that the cab's were real bad and the woofers were missing so the guy just sold me the rest including boxes for $100 and those numbers are 004422 and 004426. I have been reading around and I see people saying that they have seen Model 12's with square magnet woofers that were original, I have never seen that myself only the double ring round magnets, in fact in 1975 I was in Cleveland Ohio visiting and I went to the local KLH repair facility to buy some Model 5 woofers for a homebuilt system and the guy at the counter said " why not buy the 12 woofers for $48, $8.00 more than the 5 woofer and the 12 woofer had a double ring round magnet, (6 woofer was $32), I bought a pair and put them in my Model 23's and they rocked the house for many years powered by my Dynaco SCA80-Q I built in 1973, the 23 woofers went to the project, I am amazed how few KLH Research and Development employees are around to comment on any of these posts/subjects, I do indeed wish they would speak up more and give us more knowledge of the operations in the original KLH R&D, Rob

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Hi Vern, I can still relay these numbers to Kent but since you wanted them I'll post here, As mentioned before I have 4 Model 12's, The ones I bought as a pair are 003708 and 003711, of the other two only one has the sticker and it is 00475, I looked again to make sure of that and that one only has 5 digits instead of 6 , Also I have the back plates that came from a pair that the cab's were real bad and the woofers were missing so the guy just sold me the rest including boxes for $100 and those numbers are 004422 and 004426. I have been reading around and I see people saying that they have seen Model 12's with square magnet woofers that were original, I have never seen that myself only the double ring round magnets, in fact in 1975 I was in Cleveland Ohio visiting and I went to the local KLH repair facility to buy some Model 5 woofers for a homebuilt system and the guy at the counter said " why not buy the 12 woofers for $48, $8.00 more than the 5 woofer and the 12 woofer had a double ring round magnet, (6 woofer was $32), I bought a pair and put them in my Model 23's and they rocked the house for many years powered by my Dynaco SCA80-Q I built in 1973, the 23 woofers went to the project, I am amazed how few KLH Research and Development employees are around to comment on any of these posts/subjects, I do indeed wish they would speak up more and give us more knowledge of the operations in the original KLH R&D, Rob

Hi Bob;

Thanks for posting the serial numbers.

Other than the former serviceman from KLH, we have mainly Andy and Kent who contributes to the KLH data.

It appears now that at least 5,000 KLH Twelves were made, assuming that they used consecutive serial numbers.

If Kent can confirm that these same numbers are also inside your crossover cases written in pencil we can start some sort of historical data.

I am assuming that they serial numbered the crossovers to match their speaker enclosure.

The former employee mentioned that the woofers were modified after they were found to bottom out and a bump was stamped on the back of the magnet for these later units.

The KLH Fives, Twenty-Three's, and Twelves used the same woofers, usually marked 23 - 25 gram's on the cones.

Perhaps over time, when a driver is removed from any of the enclosures, dates can then be posted as well.

I am assuming that they clearly rubber stamped the dates on all their drivers.

It will be a long slow process.

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Vern, Trying to do a history on the original KLH you'd think you were doing a study on a company in eastern Russia in 1900, I wanted to add that when I bought those Model 12 woofers the guy did produce the Model 6 woofer for comparison, same basket ,same cone, same surround, different magnet and likely different voice coil. When we had the 12's apart last fall I remember the stampings that showed 1968 and 1969, I don't remember the dates, also on the 12's I bought as a pair there were stampings on all of the mids and tweeters that said M-12 TEST. I wonder if we'll ever know anymore about the 2 tweeters KLH mentioned in their brochures, the 1 5/8 inch and the 1 3/4 inch, maybe it's my eyes but I 've never been able to see the size difference in the cones, Thanks for the reply Vern, Kent will be receiving all of my crossover boxes today, Rob

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Vern, Trying to do a history on the original KLH you'd think you were doing a study on a company in eastern Russia in 1900, I wanted to add that when I bought those Model 12 woofers the guy did produce the Model 6 woofer for comparison, same basket ,same cone, same surround, different magnet and likely different voice coil. When we had the 12's apart last fall I remember the stampings that showed 1968 and 1969, I don't remember the dates, also on the 12's I bought as a pair there were stampings on all of the mids and tweeters that said M-12 TEST. I wonder if we'll ever know anymore about the 2 tweeters KLH mentioned in their brochures, the 1 5/8 inch and the 1 3/4 inch, maybe it's my eyes but I 've never been able to see the size difference in the cones, Thanks for the reply Vern, Kent will be receiving all of my crossover boxes today, Rob

Hi Rob;

Your first sentence pretty well sums up most classic manufacturers as well as KLH, Rob.

At first I thought it was a sarcastic comment but I will accept it as not being sarcastic.

You are incorrect about all of the woofers, though.

They all look alike YES, are physically alike, NO.

They used different weight cones between the various models.

The Sixes used 18 - 20 gram cones.

The Seveteen, Twenty and Thirty-Three another un-listed weight as of now.

The M-12 test and 23 - 25 gram cone markings, usually marked on the cone front, sometimes marked on the rear of the cone, are pretty certain to be just for the KLH Twelve.

They probably were interchangeable downward for the KLH Fives, Twenty-Threes and possibly others as well, in a pinch.

Perhaps more information will be forthcoming in the future from a newer member.

There was at least 4 or more different magnet systems as well.

The voice coil size differences, I am not aware of, no data, yet.

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Hi Vern, I guess I was being sarcastic because of my own frustration at times about the lack of info. but you opened my eyes to the fact that I/we are dealing with the 1968 information level in 2008, information flows at such an enormus rate now and companies like to boast about their products and how they come to be, this forum would probably have many more members if KLH R&D was a current company with many more eyes watching it , there are just a few of us here dealing with 40+ year old products. The M12 TEST stamping is on the back of the magnet on the mids and tweeters right next to the date, I only mentioned it because it's the first time I've ever seen that on any model, Take care, Rob

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Hi Vern, I guess I was being sarcastic because of my own frustration at times about the lack of info. but you opened my eyes to the fact that I/we are dealing with the 1968 information level in 2008, information flows at such an enormus rate now and companies like to boast about their products and how they come to be, this forum would probably have many more members if KLH R&D was a current company with many more eyes watching it , there are just a few of us here dealing with 40+ year old products. The M12 TEST stamping is on the back of the magnet on the mids and tweeters right next to the date, I only mentioned it because it's the first time I've ever seen that on any model, Take care, Rob

Hi Rob;

I never worked for a speaker manufacturer, I do not know exactly what they do when they re-design or discontinue a product.

They may have just torn up the old drawings and started over again.

Here, locally, when Heathkit shut down, all onhand manuals, for just one example, were dumpstered.

A former employee salvaged all that were available and is still hoarding them.

All Heathkit branches and the factory may have done the same thing or not.

Anyways, historical documents were destroyed.

Too bad this type information was not sent to a museum of sorts.

Due to a communication problem, my big bros set outside his house a carton of accummulated hifi data, including AR-LST, AR-10 pi and AR-3A improved blueprints, just for me.

I did not find them and all the data went to the dump, forever.

KLHMark brought the KLH pair of driver sheets to the table last year, thank you, Mark.

As a side note, try finding a factory original introduction sheet to the KLH Twelve.

So far no factory documents have surfaced, but may still do so in the future.

Try finding an original Heathkit original AS-2 owners manual.

I'm working on this one.

Photo copies are being sold on ebay but the originals are as scarce as hen's teeth.

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Rob's KLH Model Twelve Crossover Rebuild

Here are the three pair of crossovers. A little shabby

post-101828-1207804716.jpg

All electrolytic caps were removed. There were several dual-value caps. KLH apparently used whatever they got the best deal on.

post-101828-1207804737.jpg

If your speakers are smokin' -- that's a bad thing. 5 ohm 5 watt wirewound resistor was cracked in half, the plywood base was charred! The other crossover from this pair also had a cooked 5 ohm resistor. ROCK ON! B)

post-101828-1207804691.jpg

All new mylar film caps, except the 50uF value (no room!), which is made up of a 10uF mylar and a 40uF NPE. The 16uF value is made up of 10 + 5 + 1, and the 4uFs are 3 + 1. Those are the values we had to work with. Originally we had "bundles" for the 50uF value, consisting of 33uF NPE, 10uF mylar, 7uF mylar. Too big-- the nice external xover cabinets have limited headroom.

btw--I gave the wrong parts list in an earlier post (those dual value caps threw me off) :P The correct caps for each crossover are:

2) 50uF

1) 16uF

3) 4uF

1) 3uF

post-101828-1207804791.jpg

Some of the screw holes were stripped—these were filled with toothpicks and later re-drilled. Some of the plywood was split so it was glued back together

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Some of the cabinets were “sprung” so they had to be pulled together to put the screws in.

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Finished!

post-101828-1207804817.jpg post-101828-1207804802.jpg

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Rob's KLH Model Twelve Crossover Rebuild

All new mylar film caps, except the 50uF value (no room!), which is made up of a 10uF mylar and a 40uF NPE. The 16uF value is made up of 10 + 5 + 1, and the 4uFs are 3 + 1. Those are the values we had to work with. Originally we had "bundles" for the 50uF value, consisting of 33uF NPE, 10uF mylar, 7uF mylar. Too big-- the nice external xover cabinets have limited headroom.

btw--I gave the wrong parts list in an earlier post (those dual value caps threw me off) :blink: The correct caps for each crossover are:

2) 50uF

1) 16uF

3) 4uF

1) 3uF

post-101828-1207804791.jpg

Hi Kent;

Great job you did again.

Thanks for the update on the cap values as well.

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Hey guys, I'm getting ready to start buying parts for the recap on my KLH 12 Contour boxes, I only have one box right now but am going to go ahead and order enough for two, using JKent's parts list.

This discussion is a little old, does anyone have any updates or advice before I get started? Is it advisable to go ahead and recap the 12's also, my guess is yes, any advice on that subject would be welcome also.

Big shout out to RoyC for his help with my AR2ax rebuild, they sound great, that boy is a national treasure, maybe we should erect a monument ;)

thanks

okies

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Hey guys, I'm getting ready to start buying parts for the recap on my KLH 12 Contour boxes, I only have one box right now but am going to go ahead and order enough for two, using JKent's parts list.

This discussion is a little old, does anyone have any updates or advice before I get started? Is it advisable to go ahead and recap the 12's also, my guess is yes, any advice on that subject would be welcome also.

Big shout out to RoyC for his help with my AR2ax rebuild, they sound great, that boy is a national treasure, maybe we should erect a monument :)

thanks

okies

Hi Steve!

Thanks for the compliment....but I'm probably more of a relic than any kind of treasure! ;) Anyway, always glad to help out. It's one of those things that makes a hobby worthwhile.

KLH caps were generally crappy, so there is every reason to undertake that task without delay. Examine the switches, which appear to be similar to the KLH 5 switches, and use a liberal amount of Deoxit on them. I'm still having some problems with the switches in a pair of 5's, and I have run across similar switches in KLH 23's that could not be adequately cleaned. The lesser KLH models, like the 17 and 20, actually have simpler, more reliable switches.

Roy

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One thing worth mentioning again--be sure to examine all of the resistors for scorching or cracking, and replace as needed. If I were doing this again I would probably just replace all of the 5w resistors with 10w. YMMV.

Kent

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Hi to all, I was going to write Kent a while back about something that happened with my set up. I have a McIntosh system with a C-42 solid state preamp running a pair of Mac MC-275 power amps which we just re-tubed 10 months ago. The tube amps are driving a pair of KLH 5's and a pair of KLH-12's that Kent was nice enough to help me completely rebuild the crossovers in, the system just sings...... but one day I noticed all of the low bass was gone but if I ran just one amp-speaker combo the bass was fully back but as soon as both amps and all speakers were on the bass went away again, all the tubes tested fine, the preamp tested good, we swapped out all of the signal cables with known good ones, NO DIFFERENCE. I have an extra pair of Model 12 crossovers that Kent also rebult so we put those in place and it cured the problem, I now have full range throughout the system. I ask all of you in this forum, what do you think?? I can't believe that the transformers would be the culprit because the 12's worked great when they were the only ones on. All I know is that the system works great again and the original crossover boxes are sitting on a shelf for now

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Hi to all, I was going to write Kent a while back about something that happened with my set up. I have a McIntosh system with a C-42 solid state preamp running a pair of Mac MC-275 power amps which we just re-tubed 10 months ago. The tube amps are driving a pair of KLH 5's and a pair of KLH-12's that Kent was nice enough to help me completely rebuild the crossovers in, the system just sings...... but one day I noticed all of the low bass was gone but if I ran just one amp-speaker combo the bass was fully back but as soon as both amps and all speakers were on the bass went away again, all the tubes tested fine, the preamp tested good, we swapped out all of the signal cables with known good ones, NO DIFFERENCE. I have an extra pair of Model 12 crossovers that Kent also rebult so we put those in place and it cured the problem, I now have full range throughout the system. I ask all of you in this forum, what do you think?? I can't believe that the transformers would be the culprit because the 12's worked great when they were the only ones on. All I know is that the system works great again and the original crossover boxes are sitting on a shelf for now

It sounds like your woofers may have been connected out phase with each other (connected in opposite polarity), and canceling each other out.....if not at the cabinet terminals, then internally at the crossover. If you are sure you had your speakers connected properly (+ to + and - to -), I would check the crossover you removed for proper polarity.

Roy

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It sounds like your woofers may have been connected out phase with each other (connected in opposite polarity), and canceling each other out.....if not at the cabinet terminals, then internally at the crossover. If you are sure you had your speakers connected properly (+ to + and - to -), I would check the crossover you removed for proper polarity.

Roy

Hi again and thanks for the quick reply Roy......I do know about the phasing and my sons and I (I lost my hands in an accident) have got everything marked with tape markers as to their polarity not to mention the wire itself has ridges on one wire and we use that as positive. I totally agree with your statement as in the past I've seen peoples systems all messed up polarity-wise, we check with a dry cell battery connected to the back of the speaker to make sure the woofer pushes out when properly connected to the battery, and I still after all of these years watch if the woofers push outward when the amps energize, not very easily done with tube amps but it is perceptible and I do this after every wiring change. It still leaves me with "what happened ?" I talked to 2 different guys at McIntosh tech support and one offered that he thought it was one or more of the driver tubes, in these amps they use 12AX7's and 12AT7's, the other tech said he suspected an AC power supply problem, i.e. lack of , well the system has 3 dedicated circuits feeding it, 2-20A and 1-15A and all three are covered by whole house GFI and direct connected APC line conditioners which one tech thought wasn't needed, I explained to him that here in Colorado Springs cloud to ground lightning is a big concern for electronics owners, CG lightning strikes per sq. mi. are only bested by central Florida and Northern Texas. We haven't tested to see if the line conditioners are able to put out their rated amperage which are matched to the amperage capacity of the three dedicated circuits being used, we have tested voltage and all three are straight up 120 volts. It still comes back to the simple changing of the contour boxes making all the difference. As I said before Kent did all of the work on all of my KLH crossovers and he used poly film caps and replaced the ceramic resistors ect ect. (Kent please correct me if I'm wrong here) Anyway I'm kinda baffled but the system works great now and I knew once I typed it out it would be long winded but I wanted to put it out there incase anybody else has a similar experience. Frankly I might be selling off my Model 12's eventually because frankly I'm dissapointed in them, my Model 5's have stronger deeper bass than any of the 3 pairs of Model 12's here, the 5's are right there bass-wise with my AR3a's. I still think somthing went duff with one of the transformers in those contour boxes, I'll be sending them back to Kent someday, hopefully soon if my life would just slow down for a few minutes and get them out of here. I think Kent probably thinks I'm crazy but I still want to use ClarityCap SA caps in the Model Twelve boxes just like we did in the Model 5 crossovers because it made the 5's sound VERY VERY GOOD, the problem is obvious though because they'd have to be mounted externally because of size. ANY suggestions here are appreiciated, if I could really soup-up a pair of Model 12's I might hang on to a pair, okay I'm done :blink:

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Hi Rob

Of course my 1st thought is "your incompetent technician screwed up one contour box" but you said it used to work, then stopped, so maybe something did blow out. Since you have at least 3 pair of boxes, I guess you're OK for now. Actually, I did not replace the resistors (see the photo in post #34). Only replaced ones that were obviously scorched. Probably should have just replaced them all, like I did in your Fives but the common wisdom is "wire wound resistors don't go bad." Guess if you've SEEN some scorched 5-watt resistors your opinion should change!

Putting the Clarity Caps in the Twelves will be a challenge but it could be fun too. It may just be a matter of "raising the roof" on the boxes--making them taller. A little carpentry job.

You might also consider firing that bum tech. The way I hear it, he's a retired psychologist with absolutely no credentials in electronics 

Kent

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Hi Rob

Of course my 1st thought is "your incompetent technician screwed up one contour box" but you said it used to work, then stopped, so maybe something did blow out. Since you have at least 3 pair of boxes, I guess you're OK for now. Actually, I did not replace the resistors (see the photo in post #34). Only replaced ones that were obviously scorched. Probably should have just replaced them all, like I did in your Fives but the common wisdom is "wire wound resistors don't go bad." Guess if you've SEEN some scorched 5-watt resistors your opinion should change!

Putting the Clarity Caps in the Twelves will be a challenge but it could be fun too. It may just be a matter of "raising the roof" on the boxes--making them taller. A little carpentry job.

You might also consider firing that bum tech. The way I hear it, he's a retired psychologist with absolutely no credentials in electronics :blink:

Kent

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Hi, Yeah the system works fine. When I mentioned "souping up" a pair of model 12's I wanted to clairify that I was speaking only about the contour boxes, the drivers will always stay stock. So we'll see what comes with this project as we are people who enjoy tinkering with stuff. To end this post I will throw it out there if anyone has experience wiith the damping of the woofer in KLH speakers, did KLH use enough or just the right amount of fiberglass? Over and out...Rob

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" FINISHED " OR IS HE JUST GETTING WARMED UP :D:D:D , ROB

Apparently just getting warmed up.

If you go back to post #34 you can see Rob's three pair of Model Twelve contour boxes, with a mix of no-name film caps and some NPEs for the 50uF caps.

Here is the re-do of pair #2. Rob wanted all high-quality film caps. The selection was based on two considerations: Quality and physical size.

Here's what we used in each box:

1) 2.7uF Auricap (original value 3uF)

3) 4uF Auricaps

1) 15uF Clarity Cap PX (original value 16uF)

2) 50uF Dayton film & foil polypro

Also replaced all the resistors with new Mills 12w non-inductive resistors.

Fitting the 50uF Daytons was the biggest challenge. Thought I'd have to "raise the roof" of the contour box or put the caps outboard, but by cutting away part of the 1/2" plywood base inside the box, it provided just enough room. Also had to shift some of the inductors and tie points slightly.

Photos below show the contour box before the "first" recap, the plywood base notched to accept the Daytons, and the finished contour box.

One finished, one to go.

Kent

post-101828-1282167013.jpg

post-101828-1282167047.jpg

post-101828-1282167429.jpg

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Finished!

Here is a shot of the insides, labeled. The 6 screw holes on the lid were filled with epoxy and reinforced with small strips of scrap wood, then redrilled. The Velcro strips on the bottoms had to be removed to remove the plywood, so new Velcro was installed. Also added an extra strip across the top (these hang on the back of each speaker) to help support the added weight.

The Clarity cap in the center was originally installed with a cable tie but the mounting block added too much height, so now it is stuck on with double-sided foam tape.

I have never put much stock in esoteric caps--no golden ears here--but my Twelves with these upgraded xo boxes sound great! Hard to do a real A/B comparison, but subjectively I think they sound better than they did with the mylar caps, and they also seem to sound better than my AR2ax + VMPS sub setup. YMMV.

Switches were sprayed with De-Oxit and the screw terminals in the back got a little dielectric grease.

Will send these back to Rob (if I can part with them wink.gif )

Kent

edit: the 2.7uF is mislabeled as 3.7

post-101828-1282836547.jpg

post-101828-1282836569.jpg

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sure Steve. I'll send an email.

Kent

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It's been quite a while since this thread has been active, but I thought I'd chip in with the serial numbers on the pair of Twelves I recently picked up: they are 5227 and 5235, higher than the previous ones mentioned here. I haven't taken drivers out yet to look for date stamps. 

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