@@MichaelBeeny Being of a similar age, I empathise entirely. But we are still kicking on, so that is at least one positive. And we can enjoy interests. (I tell you what, I would not like to be a young man today! The world is so confusing. The 60's and 70's were great and I am thankful to have been young then)
Nicely done Sir. I have a few videos up of these speakers as my mate has them. He refurbished his too, though I don't believe he did the crossovers. That sure go deep.
I had a pair of these for a few years, they are a very good speaker. My bass drivers had been re-foamed but I did loose a tweeter so replaced both with new units. I also replaced all the crossover capacitors. The parts were supplied by Falcon Acoustics in the UK.
I had the KEF Reference 3/two since new, with a similar configuration as these. I lived with them for a few years until I heard the Spendor and Rogers speakers.. This made me realize that, KEF had tried to 'kill two birds with one stone' i.e. voice them for both, High Fidelity audio as well as, Home Theater a new concept back then. That's when I sold them and got on to Rogers LS7t which by the way, use solid *cast* baskets in their bass drivers, and Titanium twitters. Since then, I have been enjoying Classical music as never before, and let H.T. look after itself! Thanks for a lovely demo and kudos for your effort to restore these "ol' boys".
I owned a pair of BC1s for a number of years. We also sold quite a few pairs in our retail shop. I must admit overall I preferred the Rogers. The BC!s bass unit had a habit if dropping the coil on the magnet. Spendor always blamed the customers, they never took responsibility that their product could possibly be at fault!
16:30 what is so extra special between this foam surrounds that costs 66$ versus a generic but good quality surrounds ? I have a logitech 623 2.1 computer speakers that has developed similar destruction of surround , so I am wondering if I should a) replace with a generic same size similar spec speaker or b) replace the surrounds and any other repairs to it .
I had a pair with the kube. While I do like a cap upgrade, I was very leery about the control rod between the woofers. I purchased a used pair in the midlands circa 2004. They were great.
I'd like to offer some additional insight on these speakers, if I may. The bass is produced by the two B200 drivers, each in their sealed enclosure, firing - in phase - against each other in a common cavity that has a large port to allow the output. This is called 4th order bandpass alignment and KEF made a paper about this years before these speakers were produced. The KEF 107 is a similar arrangement. The alignment creates a high pass filter that allows the drivers to operate in their designed frequency range. However, it's tricky to calculate and optimize and it also causes nasty peaks and dips in frequency response and impedance. Hence, the complex crossover to "conjugate" the drivers and create a flat resistive 4Ohm load. Part of the optimization is performed by the KUBE equalizer that needs to go between the preamp and power amp. The reason these (and the R107) use seemingly "weak" magnet drivers with paper cones is that the bandpass alignment hugely enhances the low frequency output and a powerful woofer is not required. And the paper cones help aleviate resonances that would be introduced by a stiffer material and surround, like bextrene and neoprene. Regarding the 3 hole (instead of 4) woofer basket design, it was not done for these loudspeakers but many B200 drivers switched to this arrangement. Even the latter B300 12'' woofers on the R105 had three screws and curved triangle shape. I'm guessing it was mostly a styling decision than functional. It also eliminated one fastener, so there could be some cost cutting involved (lol).
Did KEF know the problem with foam surrounds disintegrating after not very long really? I've known about that problem for years and even had such issues with very cheap drivers I made into a subwoofer many many years ago. Not good. I still use a couple of pairs of loudspeakers from that era , if not older, and I'd be really pissed if they'd disintegrated or the tweeters had seized up. Loudspeakers ought to last decades in my opinion as we're not all made of loads of disposable income.
As you also said Conor, the issues were well known. I still have no idea why Kef used paper and foam after using Bextrine and rubber since they started business. Very odd.
about the crossover circuitary shown at 07:0907:16 , would it be a worthwhile endeavour to use this design and make our own crossover board for other brands speakers or does this circuitry appear to be designed specifically for the drivers used in that speaker box ? i have come across some old acoustimass 5 bass units (and acoustimass 10 also) which are also passive speakers with bose crossover in them, I thought to buy them just for crossover sake but does something happen to crossover with age ?
A crossover is just resistors, caps and inductors. Old caps probably will need replacing. Any crossover should be designed with the drivers in mind. Only cheap speakers would use a generic, who care for the price type. Note this crossover is for all 4 ohm drivers. The bass are 8 ohms but in parallel so that adds up to 4 ohms.
Classic pair of speakers there, nice job Michael. And yes, that really is a complex crossover - I've never seen anything like it before, not even BBC ones.
One of the characteristics of that crossover was its near perfect 4 ohm impedance. Threw out the frequency range. Ahhh the BBC range, those were the days when the BBC engineering dept, led the world.
@@MichaelBeeny KEF called this type of crossover technique Conjugate Load Matching - its aim was to present the amplifier with an easily driven constant resistive load rather than a frequency dependent reactive (inductance and capacitance) load which some amplifiers would find difficult to drive. I also see from the circuit diagram at 7:14 is that 6 components are used to delay the signal to one of the midrange drivers to alter the directivity of the midrange pair so a seated listener would not experience a "midrange suckout" due to phase cancellation. These days you'd expect to have 6 crossover components on a pair of speakers 🙂..
1, you did a damn good job, respectably 2 foam surrounds are not a quality criterion, but sometimes a must for sound reasons, because rubber surrounds are too heavy, and the kick bass suffers if the membrane is too heavy, unfortunately a thicker magnet doesn't help either, That's the same disaster as with tweeters, if the membrane is too heavy, the sound is gone forever Fabric surrounds usually mean too little stroke, that's why you use foam rubber, that will continue to be the case in the future, that's why there are still special types today, e.g. at SB akustik or the Lowther, because the problem has been known for 4 decades, Manufacturers have sworn to rubber, to the chagrin of those who want good sounds, and closed speakers have also gotten a bad reputation The sound is still vague and spongy with the rubber beads, so they last longer and are also mostly quieter and less dynamic. I'm sticking to foam, but I'm going to give it a try and replace the beads after about 7-10 years Before they fall apart or wear out, there are enough services in Germany that make a living. You also have to change the tires on your car Formula 1 as well!!!
The purpose of the strut between the counterfiring bass units was to have the air displacement of a larger unit with no lateral or vertical vibration. My Reference Three/2's have the same system.
I am very impressed with this speaker's design. From the look of it, the bottom (LF) bass driver is loaded in a considerably smaller enclosure than the upper. Is this correct or am I missing something?
Both chambers are much the same size, the center chamber that both drivers feed into is a similar size as both chambers added together. I hope that makes sense?
The driver units are all right and there's no reason to make stiffer chassis in this case. Paper or softer plastic cones in combination with foam results in a very good dampening of the membrane edges, yes they don't last forever and it's not this critical for low frequency. The bar between them is for compensation of the moving forces right at the point they occure, this is a genius way to prevent resonances transfering to the enclosure and it works like a dream! There are not many speakers build like this (nubert did some in the 70s/80s with this technic, too). For refilling tweeters with new ferro, you need to know the damping of the liquid. If the wrong one is chosen, it results in a completely different behavior of the tweeter / crossover network. I measured 3-4 dB differences in amplitude at the crossover freqency when testing for fluids. Quality fluids are also hard to get and expensive, so a new driver is a good thing if available. Whatever, very nice speakers, indeed! The impedance correction is ideal for tube amps and for the digital era :)
My comments on the bass drivers were really a question. Why down grade a really very good B200 at all. The original had a stronger chassis, 4 mounting holes not 3. Rubber or PVC surround, Bextreen cone, not paper. Just seemed odd to have down a lower graded driver in a flag ship model. As for the tweeters, tampering with any tweeter is a hit and miss thing to do anyway. I think the outcome I choose in the end was probably the best option A near constant speaker impedance is good for any amplifier really. This offers a near perfect 4 ohm load. Not all amplifiers will like this quite low impedance.
@@MichaelBeeny You did a great job! I guess in the end it comes all down to costs, the heavier Bextrene cone needs a bigger magnet for the same TSPs for the vented box and so on. And as long the drivers are not visible and the sound is close, it's an easy decision for the management :)
Nice video about the internals and rebuild of this good old KEF speaker. I listened several KEF's and they are great for long listening but lack dynamic. The bextrene cones give a kind of softening effect, pleasing but hiding the edges in the music. I use harder poly cone's from Vifa and Dynaudio dome D54 which are far more revealing without fatigue. Foam surrounds are fragile and not long lasting, enough reason not to use them. I like the details of the video with cross over parts ect., tempo could be a bit up for my taste. Keep up the good work!
Compared to many of today's speakers, these do have a "laid back" kind of sound, quite a pleasant sound but do lack the dynamics of modern speakers for sure. Dare I say a more VALVE kind of sound.
I had a pair of the original 104abs for a while and they sounded fantastic. I restored the cabinets and crossovers and eventually gave them to a friend and they still sound great at his place! I've read the 104/2s are even more special. I have a pair of Seas tweeters in my Audio Physic Spark IIs that have ferrofluid in them. They are over 20 years old so I'm concerned I will have to replace it...
Good job taking on the refurbishment. The age of the electrolytic capacitors in the crossover mandate replacement, regardless of brief static measurements. ESR is a grossly misunderstood parameter that leads to out right wrong advice from UA-cam "experts". They fret over a small change in ESR ignoring +/- 10 to 20% capacitance tolerance. Good quality, not boutique expensive, poly caps will yield better sound quality and long life. Manufacturers choose electrolytic because they are cheap and compact in size, not because they contribute to sound quality. It was proven many many years ago that electrolytics should never be in a crossover due to high noise, wide tolerance, and low reliability. Unfortunately, manufacturers continue to cheap out because the majority of buyers will never know the difference.
That bass driver looks like the horror hidden from plain sight. It just goes to show one should always open the lid and have a peek before buying hifi.
@@MichaelBeeny What did you replace the foam with? Was the repair kit also foam? Foam surround is not exactly a deal breaker, more of a hassle actually as foam will always be available. Even if a kit with the right dimensions cannot be found, one can always cut the foam to the desired shape.
The midrange units have no metal basket frame , they are , including the magnet , bonded directly onto the MDF cabinet during assembly in the factory 😮. The black dense rubber in the slots is resonance reduction. I know this as I had reason to dismantle one to replace a dead b110 . But it's actually not possible . ( The speakers now are used with only 1 midrange active in each speaker and it's fine)
The tube or bar between the woofer magnets is to cancel out the opposite reaction forces in the magnets. When one cone accelerate upwards the other will accelerate downwards giving oposite reaction forces in the magnets. The reason for the foam surrounds and paper cones is because the bass system is a band pass kind which dictate for high compliance loudspeaker units. The cancellation you show should be better butt then you need to select the filter capacitors the way KEF did. The capacitors used by KEF are states 10% tolerance butt KEF selected batches of capacitors out within 1%. The man or woman that did the selection had 11 boxes in front labeld from -10 to +10 % in 1% steps. From one batch it was common that e.g. -4% the most available and then used for the crossover networks where de coils, winded by KEF in house, got more or less windings to match the -4% capacitance value. Believe it or not I have seen this with my own eyes when I visited KEF in Maidstone UK.
Hello Michael - I remember the 104/2's very well - a wonderful speaker. I listen to KEF Reference Three/2's all day long. I'm curious to see how you get on in this video - I can imagine one day having to do a "refresh" of my crossovers with nice new high quality components. The drive units are all OK as far as I know. They still impress, even though I bought them in London in 2000, just over 24 years ago. All the best, Rob in Switzerland
The tweeter go down slowly over the years as the fluid dries out, they lose their sparkle and output. The crossover holds up very well, it was debatable that the caps needed replacing. I did test a few and really, they were still near perfect. The bass units, what can I say, you did see them! lol
This is great! _ I did a pair of these for a friend a while back. btw Falcon acoustic UK are Kef experts; the proprietor having being a key figure at Kef. Tweets in good shape despite being an earlier model(xover in body) - did the ferrofluid. I did put some polycaps on the tweet (and the kef kit now does have a poly in it...) and a better mundorf electro on the 100uf mid. The bottom plate had to be destroyed off! Did my woofers have a rubber surround? I can only remember doing the 'donuts'.... Sonic result was 'Night and day'.
Wonderfully restored! Have always wanted to hear a system with the KEF 104s. I have a pair of the second gen Epos ES14 speakers by Robin Marshall that I have always loved, but the tweeters are woefully under performing (they are massively 'down' on volume even after trying new filter capacitor). I tried to find the Midwest Audio you mentioned that had direct replacement for your KEF, but I think I am finding the one you mentioned. Can you/anyone point me to them? Hoping they can replace/fix my Epos ES14 tweeters! Many thanks!
It's not really a port it is the ONLY exit for the bass. The 2 bass units are in airtight containers within the main cabinet. Only the 2 mid/bass drives on the front are in back sealed containers.
Great video Michael but you worry me a bit, I have a pair of Thiel CS2 I store in my basement for almost 20 years, I'm wondering if they need some work now......Oh bummer! (Bloody hell)
I don't know the CS2 at all. Why are you keeping them? If you're not going to use them, why not sell them and buy some that you will use? I think a look and a listen will at least answer your question. Possibly not in a good way.
@@MichaelBeeny For the same reason I still got many vintage parts and gears and so many tools...But it's another story :-) I will test them this winter and who knows maybe I will fall in love with them again!
i have 104/2 ,restored them myself ,best speaker ever ,the only speakers i can live with i had a new pair in 92 i think lol ,,they should start making them again..
@@MichaelBeeny From memory they were expensive but today you could add multiples of the inflation rate since and then some. Don't understand it; but, suppose, that's what getting old ends up being.
Wow. It's been about 35 years since I heard these speakers, and yet, they're exactly as I remember. A bit brittle and hard on top, with a bit of the bass suckout. I didn't sell Kefs specifically, but we often had the 104/2s in on trade. I did sell against Kef, which I didn't mind. It was when the Snell cave came out that I had trouble. Even being a B&W dealer, I went and got the CRTs for myself. But it was truly amazing how the memory of that sound immediately comes back to me. Thank you.
I'm almost convinced that this recording is made with "electric piano". Not a real one piano. Non of the electric pianos can imitate successfully the attack of the real !
Quit probably! I had to use copyright free music, that does limit my choice in content and audio quality. UA-cam compression does not help either. The sound of my master is a lot better than the You tubs presentation sadly. I always get asked for a demo, even though it really does not represent the sound I hear live.
If you don't like my channel, don't watch it. It's as simple as that. If you HAD watched the complete video, you would have seen I did include a circuit diagram, but you were too busy complaining.
@@MichaelBeeny Not at all Michael! Do not change anything! Your reaction was justified and well controlled... On that note, I wish you and your loved ones a merry Christmas.
If you don't give this video a "LIKE" I will have no choice but to send the "BOYS" round!!
Sure - I don't need to be told twice!
Great, they can help me with some furniture I need moving.
I can do that in addition to subscribing! Good luck 👍
@@BruceLimozaine-c4q Thank you, most appreciated.
Such an interesting narration. Who needs boring tutorials when you can enjoy stories like these! Thank you.
The repair of an old item is a noble act
I wish I could get a repair on myself. Sadly, I'm beyond repair. No parts available lol
@@MichaelBeeny Being of a similar age, I empathise entirely. But we are still kicking on, so that is at least one positive. And we can enjoy interests.
(I tell you what, I would not like to be a young man today! The world is so confusing. The 60's and 70's were great and I am thankful to have been young then)
Nicely done Sir.
I have a few videos up of these speakers as my mate has them. He refurbished his too, though I don't believe he did the crossovers. That sure go deep.
I had a pair of these for a few years, they are a very good speaker. My bass drivers had been re-foamed but I did loose a tweeter so replaced both with new units. I also replaced all the crossover capacitors. The parts were supplied by Falcon Acoustics in the UK.
I had the KEF Reference 3/two since new, with a similar configuration as these.
I lived with them for a few years until I heard the Spendor and Rogers speakers..
This made me realize that, KEF had tried to 'kill two birds with one stone' i.e. voice them for both, High Fidelity audio as well as, Home Theater a new concept back then.
That's when I sold them and got on to Rogers LS7t which by the way, use solid *cast* baskets in their bass drivers, and Titanium twitters.
Since then, I have been enjoying Classical music as never before, and let H.T. look after itself!
Thanks for a lovely demo and kudos for your effort to restore these "ol' boys".
I owned a pair of BC1s for a number of years. We also sold quite a few pairs in our retail shop. I must admit overall I preferred the Rogers. The BC!s bass unit had a habit if dropping the coil on the magnet. Spendor always blamed the customers, they never took responsibility that their product could possibly be at fault!
16:30 what is so extra special between this foam surrounds that costs 66$ versus a generic but good quality surrounds ?
I have a logitech 623 2.1 computer speakers that has developed similar destruction of surround , so I am wondering if I should a) replace with a generic same size similar spec speaker or b) replace the surrounds and any other repairs to it .
I guess the cost was the limited numbers sold and the cost of the molds and of course huge mark ups. Supply & demand, no choice.
I had a pair with the kube. While I do like a cap upgrade, I was very leery about the control rod between the woofers. I purchased a used pair in the midlands circa 2004. They were great.
Well done, on all levels, the restore and the video
I'd like to offer some additional insight on these speakers, if I may.
The bass is produced by the two B200 drivers, each in their sealed enclosure, firing - in phase - against each other in a common cavity that has a large port to allow the output. This is called 4th order bandpass alignment and KEF made a paper about this years before these speakers were produced. The KEF 107 is a similar arrangement. The alignment creates a high pass filter that allows the drivers to operate in their designed frequency range. However, it's tricky to calculate and optimize and it also causes nasty peaks and dips in frequency response and impedance. Hence, the complex crossover to "conjugate" the drivers and create a flat resistive 4Ohm load. Part of the optimization is performed by the KUBE equalizer that needs to go between the preamp and power amp.
The reason these (and the R107) use seemingly "weak" magnet drivers with paper cones is that the bandpass alignment hugely enhances the low frequency output and a powerful woofer is not required. And the paper cones help aleviate resonances that would be introduced by a stiffer material and surround, like bextrene and neoprene.
Regarding the 3 hole (instead of 4) woofer basket design, it was not done for these loudspeakers but many B200 drivers switched to this arrangement. Even the latter B300 12'' woofers on the R105 had three screws and curved triangle shape. I'm guessing it was mostly a styling decision than functional. It also eliminated one fastener, so there could be some cost cutting involved (lol).
Merry Christmas, Mr Beeny.
Fantastic job with the speakers, Michael. Thanks for the video.
Thank you kind Sir, most appreciated.
Did KEF know the problem with foam surrounds disintegrating after not very long really? I've known about that problem for years and even had such issues with very cheap drivers I made into a subwoofer many many years ago. Not good. I still use a couple of pairs of loudspeakers from that era , if not older, and I'd be really pissed if they'd disintegrated or the tweeters had seized up. Loudspeakers ought to last decades in my opinion as we're not all made of loads of disposable income.
As you also said Conor, the issues were well known. I still have no idea why Kef used paper and foam after using Bextrine and rubber since they started business. Very odd.
about the crossover circuitary shown at 07:09 07:16 , would it be a worthwhile endeavour to use this design and make our own crossover board for other brands speakers or does this circuitry appear to be designed specifically for the drivers used in that speaker box ?
i have come across some old acoustimass 5 bass units (and acoustimass 10 also) which are also passive speakers with bose crossover in them, I thought to buy them just for crossover sake but does something happen to crossover with age ?
A crossover is just resistors, caps and inductors. Old caps probably will need replacing. Any crossover should be designed with the drivers in mind. Only cheap speakers would use a generic, who care for the price type. Note this crossover is for all 4 ohm drivers. The bass are 8 ohms but in parallel so that adds up to 4 ohms.
Classic pair of speakers there, nice job Michael. And yes, that really is a complex crossover - I've never seen anything like it before, not even BBC ones.
One of the characteristics of that crossover was its near perfect 4 ohm impedance. Threw out the frequency range.
Ahhh the BBC range, those were the days when the BBC engineering dept, led the world.
@@MichaelBeeny KEF called this type of crossover technique Conjugate Load Matching - its aim was to present the amplifier with an easily driven constant resistive load rather than a frequency dependent reactive (inductance and capacitance) load which some amplifiers would find difficult to drive.
I also see from the circuit diagram at 7:14 is that 6 components are used to delay the signal to one of the midrange drivers to alter the directivity of the midrange pair so a seated listener would not experience a "midrange suckout" due to phase cancellation.
These days you'd expect to have 6 crossover components on a pair of speakers 🙂..
1, you did a damn good job, respectably 2 foam surrounds are not a quality criterion, but sometimes a must for sound reasons, because rubber surrounds are too heavy, and the kick bass suffers if the membrane is too heavy, unfortunately a thicker magnet doesn't help either, That's the same disaster as with tweeters, if the membrane is too heavy, the sound is gone forever Fabric surrounds usually mean too little stroke, that's why you use foam rubber, that will continue to be the case in the future, that's why there are still special types today, e.g. at SB akustik or the Lowther, because the problem has been known for 4 decades, Manufacturers have sworn to rubber, to the chagrin of those who want good sounds, and closed speakers have also gotten a bad reputation The sound is still vague and spongy with the rubber beads, so they last longer and are also mostly quieter and less dynamic. I'm sticking to foam, but I'm going to give it a try and replace the beads after about 7-10 years Before they fall apart or wear out, there are enough services in Germany that make a living. You also have to change the tires on your car Formula 1 as well!!!
These speakers may well be available for sale. ONLY IF YOU LIVE IN NEW ZEALAND, sorry.
Nice job on the speakers! I'm interested in them and live in Auckland.
The purpose of the strut between the counterfiring bass units was to have the air displacement of a larger unit with no lateral or vertical vibration. My Reference Three/2's have the same system.
Sounds so peaceful and lively.
Thank You for an interesting video
Thank you for watching, most appreciated.
I am very impressed with this speaker's design. From the look of it, the bottom (LF) bass driver is loaded in a considerably smaller enclosure than the upper. Is this correct or am I missing something?
Both chambers are much the same size, the center chamber that both drivers feed into is a similar size as both chambers added together. I hope that makes sense?
The driver units are all right and there's no reason to make stiffer chassis in this case. Paper or softer plastic cones in combination with foam results in a very good dampening of the membrane edges, yes they don't last forever and it's not this critical for low frequency. The bar between them is for compensation of the moving forces right at the point they occure, this is a genius way to prevent resonances transfering to the enclosure and it works like a dream! There are not many speakers build like this (nubert did some in the 70s/80s with this technic, too).
For refilling tweeters with new ferro, you need to know the damping of the liquid. If the wrong one is chosen, it results in a completely different behavior of the tweeter / crossover network. I measured 3-4 dB differences in amplitude at the crossover freqency when testing for fluids. Quality fluids are also hard to get and expensive, so a new driver is a good thing if available.
Whatever, very nice speakers, indeed! The impedance correction is ideal for tube amps and for the digital era :)
My comments on the bass drivers were really a question. Why down grade a really very good B200 at all. The original had a stronger chassis, 4 mounting holes not 3. Rubber or PVC surround, Bextreen cone, not paper. Just seemed odd to have down a lower graded driver in a flag ship model.
As for the tweeters, tampering with any tweeter is a hit and miss thing to do anyway. I think the outcome I choose in the end was probably the best option
A near constant speaker impedance is good for any amplifier really. This offers a near perfect 4 ohm load. Not all amplifiers will like this quite low impedance.
@@MichaelBeeny You did a great job!
I guess in the end it comes all down to costs, the heavier Bextrene cone needs a bigger magnet for the same TSPs for the vented box and so on. And as long the drivers are not visible and the sound is close, it's an easy decision for the management :)
Nice video about the internals and rebuild of this good old KEF speaker. I listened several KEF's and they are great for long listening but lack dynamic. The bextrene cones give a kind of softening effect, pleasing but hiding the edges in the music. I use harder poly cone's from Vifa and Dynaudio dome D54 which are far more revealing without fatigue. Foam surrounds are fragile and not long lasting, enough reason not to use them. I like the details of the video with cross over parts ect., tempo could be a bit up for my taste. Keep up the good work!
Compared to many of today's speakers, these do have a "laid back" kind of sound, quite a pleasant sound but do lack the dynamics of modern speakers for sure. Dare I say a more VALVE kind of sound.
I had a pair of the original 104abs for a while and they sounded fantastic. I restored the cabinets and crossovers and eventually gave them to a friend and they still sound great at his place! I've read the 104/2s are even more special. I have a pair of Seas tweeters in my Audio Physic Spark IIs that have ferrofluid in them. They are over 20 years old so I'm concerned I will have to replace it...
for me its very very very nice sound quality... the high mid and low blend together perfectly...
I bought a pair in 1987 sold them to brother in law about 5 yrs ago woofers still in good shape
Those speakers have a wonderful design.
That crossover itself needs a dedicated video! 😵💫
A little outside my pay grade, sadly.
Good job taking on the refurbishment. The age of the electrolytic capacitors in the crossover mandate replacement, regardless of brief static measurements. ESR is a grossly misunderstood parameter that leads to out right wrong advice from UA-cam "experts". They fret over a small change in ESR ignoring +/- 10 to 20% capacitance tolerance. Good quality, not boutique expensive, poly caps will yield better sound quality and long life. Manufacturers choose electrolytic because they are cheap and compact in size, not because they contribute to sound quality. It was proven many many years ago that electrolytics should never be in a crossover due to high noise, wide tolerance, and low reliability. Unfortunately, manufacturers continue to cheap out because the majority of buyers will never know the difference.
That bass driver looks like the horror hidden from plain sight. It just goes to show one should always open the lid and have a peek before buying hifi.
Good advice Stelios, a must if they have foam suspension.
@@MichaelBeeny What did you replace the foam with? Was the repair kit also foam? Foam surround is not exactly a deal breaker, more of a hassle actually as foam will always be available. Even if a kit with the right dimensions cannot be found, one can always cut the foam to the desired shape.
The midrange units have no metal basket frame , they are , including the magnet , bonded directly onto the MDF cabinet during assembly in the factory 😮. The black dense rubber in the slots is resonance reduction. I know this as I had reason to dismantle one to replace a dead b110 . But it's actually not possible . ( The speakers now are used with only 1 midrange active in each speaker and it's fine)
Wow. Who knew you would do this. I have 2 pairs of these. One needs a slight refurb then other needs a full refurb
Good luck Chris, you might well need it!
Great job Mister Beeny! It is a strange paradox to see crossovers so sophisticated and loudspeakers so poor quality...
The tube or bar between the woofer magnets is to cancel out the opposite reaction forces in the magnets. When one cone accelerate upwards the other will accelerate downwards giving oposite reaction forces in the magnets. The reason for the foam surrounds and paper cones is because the bass system is a band pass kind which dictate for high compliance loudspeaker units. The cancellation you show should be better butt then you need to select the filter capacitors the way KEF did. The capacitors used by KEF are states 10% tolerance butt KEF selected batches of capacitors out within 1%. The man or woman that did the selection had 11 boxes in front labeld from -10 to +10 % in 1% steps. From one batch it was common that e.g. -4% the most available and then used for the crossover networks where de coils, winded by KEF in house, got more or less windings to match the -4% capacitance value. Believe it or not I have seen this with my own eyes when I visited KEF in Maidstone UK.
Hello Michael - I remember the 104/2's very well - a wonderful speaker. I listen to KEF Reference Three/2's all day long.
I'm curious to see how you get on in this video - I can imagine one day having to do a "refresh" of my crossovers with nice new high quality components. The drive units are all OK as far as I know. They still impress, even though I bought them in London in 2000, just over 24 years ago. All the best, Rob in Switzerland
The tweeter go down slowly over the years as the fluid dries out, they lose their sparkle and output. The crossover holds up very well, it was debatable that the caps needed replacing. I did test a few and really, they were still near perfect. The bass units, what can I say, you did see them! lol
This is great! _ I did a pair of these for a friend a while back. btw Falcon acoustic UK are Kef experts; the proprietor having being a key figure at Kef. Tweets in good shape despite being an earlier model(xover in body) - did the ferrofluid. I did put some polycaps on the tweet (and the kef kit now does have a poly in it...) and a better mundorf electro on the 100uf mid. The bottom plate had to be destroyed off! Did my woofers have a rubber surround? I can only remember doing the 'donuts'.... Sonic result was 'Night and day'.
A ordered the caps from Falcon. Thankfully I managed to get the bottom cover off quite easily with a putty knife with no damage whatso ever.
Wonderfully restored! Have always wanted to hear a system with the KEF 104s. I have a pair of the second gen Epos ES14 speakers by Robin Marshall that I have always loved, but the tweeters are woefully under performing (they are massively 'down' on volume even after trying new filter capacitor). I tried to find the Midwest Audio you mentioned that had direct replacement for your KEF, but I think I am finding the one you mentioned. Can you/anyone point me to them? Hoping they can replace/fix my Epos ES14 tweeters! Many thanks!
Details as requested.
Midwest Speaker Repair
1901 Oakcrest Ave, Suite 1
Roseville, MN 55113
651-645-7385
www.midwestspeaker.com
if air tight driver cab why have front bass port?
It's not really a port it is the ONLY exit for the bass. The 2 bass units are in airtight containers within the main cabinet. Only the 2 mid/bass drives on the front are in back sealed containers.
Great video Michael but you worry me a bit, I have a pair of Thiel CS2 I store in my basement for almost 20 years, I'm wondering if they need some work now......Oh bummer! (Bloody hell)
I don't know the CS2 at all. Why are you keeping them? If you're not going to use them, why not sell them and buy some that you will use? I think a look and a listen will at least answer your question. Possibly not in a good way.
@@MichaelBeeny For the same reason I still got many vintage parts and gears and so many tools...But it's another story :-) I will test them this winter and who knows maybe I will fall in love with them again!
Some of the best speaker drivers available today from Scanspeak and Seas still use paper cones due to its rigidity and strength.
Sound lovely mate
i have 104/2 ,restored them myself ,best speaker ever ,the only speakers i can live with i had a new pair in 92 i think lol ,,they should start making them again..
I think these days they would be a very expensive loudspeaker. Also, Kef is not the company it was, completely different these days.
@@MichaelBeeny From memory they were expensive but today you could add multiples of the inflation rate since and then some. Don't understand it; but, suppose, that's what getting old ends up being.
Wow nice video sir 🎉🎉🎉🎉
Wow. It's been about 35 years since I heard these speakers, and yet, they're exactly as I remember. A bit brittle and hard on top, with a bit of the bass suckout. I didn't sell Kefs specifically, but we often had the 104/2s in on trade. I did sell against Kef, which I didn't mind. It was when the Snell cave came out that I had trouble. Even being a B&W dealer, I went and got the CRTs for myself. But it was truly amazing how the memory of that sound immediately comes back to me. Thank you.
12:55 Tweeter coils can be rewound.
Very true, but the cost of postage and labour, new fluid, not worth the effort. These were also badly corroded.
@@MichaelBeeny Nowadays replacement is often cheaper than repair. The originals can be kept as a backup as one never knows.
I got a PAIR if someone wants them contact me... I live in Ft. Lauderdale,FL they are original and will need to be refurbished....
Try the car stereo market for 4 ohm stuff. Idk, I'm just a dog.
Hummm, car stuff is best left in the car. Ask the dog lol
Very Nice!
you can buy replacement tweeters new from usa
I did buy replacement tweeter from America, at least I thought I did??
I gave it a like cos I’m scared.
i used american copy t33 tweeters they just dropped in ,midwests they sound better anyway ..
That's exactly what I did use in the end, not cheap but good.
I'm almost convinced that this recording is made with "electric piano". Not a real one piano. Non of the electric pianos can imitate successfully the attack of the real !
Quit probably! I had to use copyright free music, that does limit my choice in content and audio quality. UA-cam compression does not help either. The sound of my master is a lot better than the You tubs presentation sadly. I always get asked for a demo, even though it really does not represent the sound I hear live.
Useless blah. Useless details. Schematic please.
If you don't like my channel, don't watch it. It's as simple as that.
If you HAD watched the complete video, you would have seen I did include a circuit diagram, but you were too busy complaining.
@StephCno1961 WOW! Seriously sir? Please do all gentlemen here a favor......Have a great session.
@@fredcailloux2526 Maybe I was a little bit over the top. Happy Christmas to you Fred and all my viewers. You are all very appreciated.
@@MichaelBeeny Not at all Michael! Do not change anything! Your reaction was justified and well controlled... On that note, I wish you and your loved ones a merry Christmas.