rexhunt Posted February 9, 2013 Report Share Posted February 9, 2013 Hi, I'm new to the site but I have been lurking since I picked up a pair of large Advents at a garage sale last Summer. I recently came across a pair of KLH model 24 speakers at a thrift shop for $5. When I got them home, I hooked them up next to my wife's Boston HD8s which are similar. They both worked and the bass was fine but the highs left a lot to be desired. The tweeters were working so I started doing some searches here and on AudioKarma. It looked like I probably needed to replace the caps in the crossover.I found a great thread showing the crossover with the inductor, resistor, 8, and 16mfd caps. Well, I removed the woofer on one and checked out the crossover and it had only the inductor and a single cap. These speakers have the screw terminals which it seems was standard on the stand-alone versions rather than the RCA jack found on the speakers that came with the system 24.My question is, is the 4 component crossover designed to match the system? Is there an advantage to using the more complicated circuit on the stand-alone or should I just replace the single cap?Thanks,Rex Quote Link to comment Share on other sites More sharing options...
JKent Posted February 9, 2013 Report Share Posted February 9, 2013 Nice find!First of all--that capacitor absolutely must be replaced. It's PVC and they always leak (or worse--I had one explode!)Your photo is a little unclear but what's throwing you off is--that's a double cap. A common lead comes out of one end and there will be two leads coming out of the other. The cap itself will be marked with the 2 values. Just replace it with an 8uF and a 16uF. I used Caeli caps from Madisound in mine. They are inexpensive and the ESR is close to the originals.Kent Quote Link to comment Share on other sites More sharing options...
rexhunt Posted February 9, 2013 Author Report Share Posted February 9, 2013 Nice find!First of all--that capacitor absolutely must be replaced. It's PVC and they always leak (or worse--I had one explode!)Your photo is a little unclear but what's throwing you off is--that's a double cap. A common lead comes out of one end and there will be two leads coming out of the other. The cap itself will be marked with the 2 values. Just replace it with an 8uF and a 16uF. I used Caeli caps from Madisound in mine. They are inexpensive and the ESR is close to the originals.KentThanks Kent, that is exactly what I was expecting based on your previous posts, but it is a single 4 ufd cap and no resistor. I found a thread on AudioKarma with the same thing.Rex Quote Link to comment Share on other sites More sharing options...
JKent Posted February 9, 2013 Report Share Posted February 9, 2013 btw, welcome RexI'm stumped. The only thing I can think of is this: KLH made both a Model Twenty-Four and a Model Twenty-Four Series II. Mine were the Series II. Maybe they changed the design. There are other members here with M-24 experience, so maybe you'll get another answer. Think if these were mine I'd just replace the 4uF and see how they sound. You could always go with the more complex xo later.Kent Quote Link to comment Share on other sites More sharing options...
RoyC Posted February 9, 2013 Report Share Posted February 9, 2013 Coincidentally, I've just been given a pair of KLH 24's to check out for Ebay's "Vintage AR". The crossover cap in each cabinet is a dual 2uf npe wired in parallel to produce a total of 4uf. They are not out of spec by much, but I will replace them with single 4uf film caps. See photo of crossover with original cap...Roy Quote Link to comment Share on other sites More sharing options...
rexhunt Posted February 9, 2013 Author Report Share Posted February 9, 2013 Coincidentally, I've just been given a pair of KLH 24's to check out for Ebay's "Vintage AR". The crossover cap in each cabinet is a dual 2uf npe wired in parallel to produce a total of 4uf. They are not out of spec by much, but I will replace them with single 4uf film caps. See photo of crossover with original cap...RoyWell, I'm just going to replace the 4uf caps and go from there. Roy, did you find a date on the woofer? Mine were from Feb. 1969.Rex Quote Link to comment Share on other sites More sharing options...
RoyC Posted February 9, 2013 Report Share Posted February 9, 2013 Well, I'm just going to replace the 4uf caps and go from there. Roy, did you find a date on the woofer? Mine were from Feb. 1969.RexNo dates on the woofers. The serial numbers on the rear of the cabinets are 020872 and 020873.Roy Quote Link to comment Share on other sites More sharing options...
rexhunt Posted February 9, 2013 Author Report Share Posted February 9, 2013 No dates on the woofers. The serial numbers on the rear of the cabinets are 020872 and 020873.RoyMine are 114266 and 114267. The numbers must be some sort of code rather than sequential - that would have been over 93,000 speakers made between ours which is highly doubtful.Rex Quote Link to comment Share on other sites More sharing options...
RoyC Posted February 9, 2013 Report Share Posted February 9, 2013 Mine are 114266 and 114267. The numbers must be some sort of code rather than sequential - that would have been over 93,000 speakers made between ours which is highly doubtful.RexI'm pretty sure KLH speakers were sequential for each model.AR speakers of that era certainly were. The poorest selling model, the AR-5, sold around 50,000, which was reflected by the serial numbers. Other AR models, such as the AR-4x, sold around 400,000, with cabinet serial numbers showing same.Roy Quote Link to comment Share on other sites More sharing options...
rexhunt Posted February 9, 2013 Author Report Share Posted February 9, 2013 I'm pretty sure KLH speakers were sequential for each model.AR speakers of that era certainly were. The poorest selling model, the AR-5, sold around 50,000, which was reflected by the serial numbers. Other AR models, such as the AR-4x, sold around 400,000, with cabinet serial numbers showing same.RoyWow, that's a lot of speakers. Going by the 2 year model life, I didn't think they would have made that many.So, I wonder how many had the simple circuit compared to the one mentioned most on this site?Rex Quote Link to comment Share on other sites More sharing options...
RoyC Posted February 9, 2013 Report Share Posted February 9, 2013 Wow, that's a lot of speakers. Going by the 2 year model life, I didn't think they would have made that many.So, I wonder how many had the simple circuit compared to the one mentioned most on this site?RexDon't know for sure about KLH, but AR and KLH owned the lions share of the speaker business in those days.I think Kent has it figured out. It is possible the serial number sequence differs between the two versions.Do you have a schematic for the other crossover?Roy Quote Link to comment Share on other sites More sharing options...
JKent Posted February 9, 2013 Report Share Posted February 9, 2013 Hi RexJust did a cursory search and I see you and Roy have discussed this on AK. It seems the 24 had the single 4uF and the 24/II had the 8uF and 16uF. There is no switch on the back (as there was on the similar 17 and 20). AK member Boto wrote "8uf... is the ... value of the tweeter cap in mine. The 16uf across the woofer may have been a later mod to the crossover that wasn't in yours. No harm in adding it in. It should help sharpen the slope of the roll-off of the woofer."Sounds like an explanation.Don't think we ever figured out the inductor values in the 2 versions.Kent Quote Link to comment Share on other sites More sharing options...
RoyC Posted February 10, 2013 Report Share Posted February 10, 2013 Hi RexJust did a cursory search and I see you and Roy have discussed this on AK. It seems the 24 had the single 4uF and the 24/II had the 8uF and 16uF. There is no switch on the back (as there was on the similar 17 and 20). AK member Boto wrote "8uf... is the ... value of the tweeter cap in mine. The 16uf across the woofer may have been a later mod to the crossover that wasn't in yours. No harm in adding it in. It should help sharpen the slope of the roll-off of the woofer."Sounds like an explanation.Don't think we ever figured out the inductor values in the 2 versions.KentI did find an AK thread and a schematic. Along with the larger 8uf cap, it also shows a 3 ohm resistor on the tweeter not found in the simple crossover version. The added 16uf cap is in series with a parallel woofer inductor. I would go one way or the other, but would not combine the two crossover versions.Roy Quote Link to comment Share on other sites More sharing options...
rexhunt Posted February 16, 2013 Author Report Share Posted February 16, 2013 Just to let you all know, I replaced the 4mfd capacitors with new Erse caps and the 24s sound much better. A very tight sound with plenty of bass and much nicer highs than before. I know it's apples and oranges, but I was A/B-ing them with my large Advents and while the Advents had the much deeper bass, the KLHs had better mid and highs. I bought caps for the Advents as well to reach the minimum order and just got done with them. Now the highs and mids are where they should be. Those little KLH 24s really are amazing little speakers - with a total investment of around $15 I'm one happy camper!!Rex Quote Link to comment Share on other sites More sharing options...
RoyC Posted February 17, 2013 Report Share Posted February 17, 2013 Just to let you all know, I replaced the 4mfd capacitors with new Erse caps and the 24s sound much better. A very tight sound with plenty of bass and much nicer highs than before. I know it's apples and oranges, but I was A/B-ing them with my large Advents and while the Advents had the much deeper bass, the KLHs had better mid and highs. I bought caps for the Advents as well to reach the minimum order and just got done with them. Now the highs and mids are where they should be. Those little KLH 24s really are amazing little speakers - with a total investment of around $15 I'm one happy camper!!RexHi Rex,I also thought the 24's sounded quite good.Interestingly, I just re-capped a pair of KLH 20's and found a similar situation. These had a single 8uf cap as the entire crossover, yet others I've worked on have had the 8uf cap as well as an additional 2X2uf cap.Roy Quote Link to comment Share on other sites More sharing options...
dabraham Posted May 15, 2021 Report Share Posted May 15, 2021 I realize this thread is quite old, but thought I would add some info uncovered while working on a pair of older KLH Twenty-Four. Serial numbers: 015708 and 015757. These would certainly be the early series (normal 8-32 posts) but maybe towards the end before the change to series II. The date is covered by the XO on one and is smudged on the other -- looks like Oct 24, 1968 (??). There are no resisters and only the double cap -- 2x2 uf and different than RoyC's above (a larger Red cap -- Planit brand 2x2uf 50v). [So replacing with a 4uf and done, right?] The cool thing to have uncovered is the inducer value -- handwritten on the side is what appears to be M-24 and on the other side it is stamped 24. Does this mean .24mH? Is it worth replacing? Looks just like RoyC's above. Dan Quote Link to comment Share on other sites More sharing options...
dabraham Posted May 15, 2021 Report Share Posted May 15, 2021 OR is that just a label for the parts bin as Model-24?? Quote Link to comment Share on other sites More sharing options...
dabraham Posted May 15, 2021 Report Share Posted May 15, 2021 OK, found the tread with the same single Planit capacitor (red) and no resistor:https://community.classicspeakerpages.net/topic/8734-klh-24-capicitors-confusion/ Given the variations on the KLH 24 crossovers, is it best to replace with the 4uf OR "upgrade" the crossover to the later version with the 8uf/16uf and add the resistor? Or better to stick with what was "stock" for the particular variation? Dan Quote Link to comment Share on other sites More sharing options...
RoyC Posted May 16, 2021 Report Share Posted May 16, 2021 10 hours ago, dabraham said: OK, found the tread with the same single Planit capacitor (red) and no resistor:https://community.classicspeakerpages.net/topic/8734-klh-24-capicitors-confusion/ Given the variations on the KLH 24 crossovers, is it best to replace with the 4uf OR "upgrade" the crossover to the later version with the 8uf/16uf and add the resistor? Or better to stick with what was "stock" for the particular variation? Dan M-24 probably just means Model 24, Dan. The inductors measured 1.60mh in cabinets (serial numbers 053924, 053925, 089657 and 089668) I recently worked on. They all had the single 4uf capacitor, and I replaced them in kind. Roy Quote Link to comment Share on other sites More sharing options...
dabraham Posted May 16, 2021 Report Share Posted May 16, 2021 Hi Roy -- many thanks. Will stick to the straight single 4uf each. Saves some effort as well. Was the date clear on either of your pairs? Curious to know if mine are 1968, '66 or maybe '65? Stamp too blurred to know for sure. That pics is about as good as I can do but still can't make it out. Dan Quote Link to comment Share on other sites More sharing options...
RoyC Posted May 17, 2021 Report Share Posted May 17, 2021 7 hours ago, dabraham said: Hi Roy -- many thanks. Will stick to the straight single 4uf each. Saves some effort as well. Was the date clear on either of your pairs? Curious to know if mine are 1968, '66 or maybe '65? Stamp too blurred to know for sure. That pics is about as good as I can do but still can't make it out. Dan I briefly looked at a couple of the woofers, and the dates were very smeared...perhaps '66. Roy Quote Link to comment Share on other sites More sharing options...
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