I personally would try and find another good T27 and use that. By changing the tweeter, you are going to change the sound of this great loudspeaker. You said "what happens to my head after a week of Google". Been there, done that, you mind races with all the possibilities. Keep it simple, go with what the factory installed.
If you feel the crossover is going bad, then try replacing the capacitors in it. You can get replacements from Parts Express, Erse Audio, Madisound, places like that.
Of course, I might not be the one to comment on keeping it original, since I'm rebuilding and modifying a set of JBL L100s.
http://www.diyaudio.com/forums/multi-way/182612-jbl-l100-restoration-upgrade.html
But my plan is to build a switchable crossover, so I can go back to the original sound if I desire.
Lee.
If you feel the crossover is going bad, then try replacing the capacitors in it. You can get replacements from Parts Express, Erse Audio, Madisound, places like that.
Of course, I might not be the one to comment on keeping it original, since I'm rebuilding and modifying a set of JBL L100s.
http://www.diyaudio.com/forums/multi-way/182612-jbl-l100-restoration-upgrade.html
But my plan is to build a switchable crossover, so I can go back to the original sound if I desire.
Lee.
Hello Lee
Thanks for the suggestion. Nice work on the JBL L100. Good job and great pictures!
I have heard the JBL L100 (with super tweeters); it sounds fabulous.
With regards to the KEF104aB, if there are adequate supply of KEF T27A, I would gladly go for them. However, due to their fame and shortages, prices are getting ridiculous. I rebuilt the KEF 104 in 2003/04 period, and it was already very difficult to get a decent pair of KEF T27A at a sensible price. Recently, some offered me the T27A pair in the region of US$250-300. I would rather buy the Hiquphon OWI really for that sort of cost.
The T27A slowly deteriorate over time. I have a working pair of KEF104 and KEF LS3/5A. My 25 year old KEF LS3/5A sounds more dull than newer pairs of LS3/5 or equivalent, so I may be driven into T27A hunt again. With so many pairs of old LS 3/5 around, the T27A will become more and more difficult to source. It would be prudent to start looking for a decent replacement. I have heard many speakers, and unfortunately, I have yet found a pair that would make me part with the 104.
There are difficulties in retaining the original sound of the T27A with modern equivalents. Better technology does not necessary mean better sound. I have already heard the LS 3/5a using the Morel MDT29 as replacement. It may not be easy for many to spot the 'difference' (especially after some whisky 😎). Anyway, I always have a pair of 'standard' 104 to fall back on. Apart from the tweeter change on the 104aB project, the speaker cabinet may take another few more weeks to restore.
Jonathan
Thanks for the suggestion. Nice work on the JBL L100. Good job and great pictures!
I have heard the JBL L100 (with super tweeters); it sounds fabulous.
With regards to the KEF104aB, if there are adequate supply of KEF T27A, I would gladly go for them. However, due to their fame and shortages, prices are getting ridiculous. I rebuilt the KEF 104 in 2003/04 period, and it was already very difficult to get a decent pair of KEF T27A at a sensible price. Recently, some offered me the T27A pair in the region of US$250-300. I would rather buy the Hiquphon OWI really for that sort of cost.
The T27A slowly deteriorate over time. I have a working pair of KEF104 and KEF LS3/5A. My 25 year old KEF LS3/5A sounds more dull than newer pairs of LS3/5 or equivalent, so I may be driven into T27A hunt again. With so many pairs of old LS 3/5 around, the T27A will become more and more difficult to source. It would be prudent to start looking for a decent replacement. I have heard many speakers, and unfortunately, I have yet found a pair that would make me part with the 104.
There are difficulties in retaining the original sound of the T27A with modern equivalents. Better technology does not necessary mean better sound. I have already heard the LS 3/5a using the Morel MDT29 as replacement. It may not be easy for many to spot the 'difference' (especially after some whisky 😎). Anyway, I always have a pair of 'standard' 104 to fall back on. Apart from the tweeter change on the 104aB project, the speaker cabinet may take another few more weeks to restore.
Jonathan
Thank you!
Wow! Have you tried looking on eBay UK? I look around on there a lot, but I have an advantage in that I used to live there, so I can get stuff sent to my family.
Not the Eton tweeter, plus possible repairs
Hi Jonathan,
as you are in USA, look at:
Home Page | The Classic Speaker Pages
In the Links there are a few repairers listed, and they seem to mostly work on vintage USA designs, but other repairers are mentioned in some threads in the Discussions.
There may be some-one who can do the necessary surgery to cut out the worn portion and re-join the almost surely mostly good portion of the voice-coil wire of that T27.
Believe it or not, such things are done ! ... I just don't remember who does them.
Despite some similarities that Eton tweeter is not sufficiently similar to a T27 to enable easy substitution.
The give-away is visible in the Impedance Plot.
See that chair shape from about 1kHz to about 2kHz.
In it is the flat region between 1.3 and 1.7 kHz at about 12 ohms.
This region is very different to a T27's impedance, which has a peak at about 1.1kHz, but then smoothly falls and has no flat-chair area.
The 12 ohm flat area of the Eton would require different crossover components to allow the Eton to cross at 3kHz, because the Octave below the crossover point does add to form the final response.
The Usher 9950C-15 is very like the T27 in its impedance shape, and only a resistor is need to get the magnitude optimum for the crossover components.
Also, the Eton is higher Sensitivity in part of its frequency range - see the Frequency Response plot.
I would use a ScanSpeak 950000 in preference to the Eton, but I suppose the Scan is above your budget, and really its Sensitivity is higher than optimum for use with a B200, unless one wants to drive it very hard.
Kef T27 is NOT 80dB Sensitivity, that 80dB is result of a particular type of specified test.
T27 is between 84 - 86dB Sensitivity, varying across its bandwidth.
Unless another brand/Company have something, it seems the Usher C-15 is the one to use.
I have to go now, I'll comment on other new points when I have time available.
Hi Jonathan,
as you are in USA, look at:
Home Page | The Classic Speaker Pages
In the Links there are a few repairers listed, and they seem to mostly work on vintage USA designs, but other repairers are mentioned in some threads in the Discussions.
There may be some-one who can do the necessary surgery to cut out the worn portion and re-join the almost surely mostly good portion of the voice-coil wire of that T27.
Believe it or not, such things are done ! ... I just don't remember who does them.
Despite some similarities that Eton tweeter is not sufficiently similar to a T27 to enable easy substitution.
The give-away is visible in the Impedance Plot.
See that chair shape from about 1kHz to about 2kHz.
In it is the flat region between 1.3 and 1.7 kHz at about 12 ohms.
This region is very different to a T27's impedance, which has a peak at about 1.1kHz, but then smoothly falls and has no flat-chair area.
The 12 ohm flat area of the Eton would require different crossover components to allow the Eton to cross at 3kHz, because the Octave below the crossover point does add to form the final response.
The Usher 9950C-15 is very like the T27 in its impedance shape, and only a resistor is need to get the magnitude optimum for the crossover components.
Also, the Eton is higher Sensitivity in part of its frequency range - see the Frequency Response plot.
I would use a ScanSpeak 950000 in preference to the Eton, but I suppose the Scan is above your budget, and really its Sensitivity is higher than optimum for use with a B200, unless one wants to drive it very hard.
Kef T27 is NOT 80dB Sensitivity, that 80dB is result of a particular type of specified test.
T27 is between 84 - 86dB Sensitivity, varying across its bandwidth.
Unless another brand/Company have something, it seems the Usher C-15 is the one to use.
I have to go now, I'll comment on other new points when I have time available.
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Hello Allan,
Thanks for the detailed examination of the Eton/KEF impedance vs F plots.
With regards to the sensitivity plot, it could be by dissipated power or by applied rms voltage. Whatever it is, two different designs/make will certainly have a different response curve/sound. Strictly from a measured characteristics point of view, it is not possible to find an 'analog' of the T27 as you mentioned before.
I have no intention to repair the damaged T27. I have heard repaired units before (fixed by bridging wire(s)), it will sound different. The compliance maybe changed. Sometimes, it can sound broken. The damaged T27 I have shows a visible reduction in wire diameter on the (+), so its a goner.
Still no sight of a decent replacement pair of T27. Not sure I really want something that was EOL so many years ago. And at what price?
The Usher 9950C-15 sounds 'good'. I no longer own any SPL measuring tools, so I have to rely on listening tests if I were to use it. I appreciate your recommendation, as I do not want to end up changing tweeters after tweeters.
The carpenter has got back to me about the cabinets. Part of them were damaged because of exposure to humidity. The chip board has bulged out at certain sections. The corners were dented, bits and pieces were falling off. As such, he patched up the corners, fixed the rotten portions with fillers and sanded the sides even. He will be putting on real wood veneer and to apply a layer of lacquer on the insider of the cabinet. I know this is a time consuming dirty job; not many wants to do it.
I listened to the KEF 104 reference last night. The last track of Compact Jazz Stan Getz by Stan: Girl from Ipanema was hauntingly real.
To be honest, I am tempted to try out the Hiquphon OW1 for this project. Would they be the ultimate combination when used with Clarity caps? They are not as expensive as I thought. I used to think there were at US$220+ each. That price tag actually refers to a pair of OW1. And that is half of what many other tweeters are asking for really.
Hiquphon OWI (OW1) dome tweeter features
Thanks for the advises and time. Cheers.
Jonathan
Thanks for the detailed examination of the Eton/KEF impedance vs F plots.
With regards to the sensitivity plot, it could be by dissipated power or by applied rms voltage. Whatever it is, two different designs/make will certainly have a different response curve/sound. Strictly from a measured characteristics point of view, it is not possible to find an 'analog' of the T27 as you mentioned before.
I have no intention to repair the damaged T27. I have heard repaired units before (fixed by bridging wire(s)), it will sound different. The compliance maybe changed. Sometimes, it can sound broken. The damaged T27 I have shows a visible reduction in wire diameter on the (+), so its a goner.
Still no sight of a decent replacement pair of T27. Not sure I really want something that was EOL so many years ago. And at what price?
The Usher 9950C-15 sounds 'good'. I no longer own any SPL measuring tools, so I have to rely on listening tests if I were to use it. I appreciate your recommendation, as I do not want to end up changing tweeters after tweeters.
The carpenter has got back to me about the cabinets. Part of them were damaged because of exposure to humidity. The chip board has bulged out at certain sections. The corners were dented, bits and pieces were falling off. As such, he patched up the corners, fixed the rotten portions with fillers and sanded the sides even. He will be putting on real wood veneer and to apply a layer of lacquer on the insider of the cabinet. I know this is a time consuming dirty job; not many wants to do it.
I listened to the KEF 104 reference last night. The last track of Compact Jazz Stan Getz by Stan: Girl from Ipanema was hauntingly real.
To be honest, I am tempted to try out the Hiquphon OW1 for this project. Would they be the ultimate combination when used with Clarity caps? They are not as expensive as I thought. I used to think there were at US$220+ each. That price tag actually refers to a pair of OW1. And that is half of what many other tweeters are asking for really.
Hiquphon OWI (OW1) dome tweeter features
Thanks for the advises and time. Cheers.
Jonathan
Attachments
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Hiquphon versus Usher
Hi Jonathan,
If you can afford them, then I recommend buying the Hiquphon OW1 as "matched pair", because they are a long-known, proven very good quality tweeter, and a simple variation of the 104 crossover can be used,
as it could also be for the Usher 9950C-15 which the only reservation I have about is that I have not heard them, and they have not been available for as long as the H'phon, BUT the very well-known designer, Joseph D'Appolito, has used that Usher tweeter, {and other Usher drivers}, in his designs, of which some have been very well reviewed.
He can use any brand of drivers he wants to, and I doubt he'd put his name to designs that used drivers that were not good, thus I am reasonably confident the 9950C-15 will be a good tweeter ... but as good as the OW1 ?
... well, it may approach it, but at the higher price and long experience designing tweeters of the H'phon designer, I think OW1 would be better.
The final success or otherwise will be how much tweaking of the crossover you are willing to do if the initial version is not quite what you like best.
Changes may only have to be to resistors.
I'll explain more after you decide a tweeter, though for now what level of treble output do you want ?
The original has about -1dB treble versus mids from the B200, if I'm remembering correctly ... though if you set that mids' knob for full out-put
there will be much higher mids than treble.
With the new tweeter, do you want equal treble to the flattest setting of the mids' knob, or slightly less treble as was the original ?
Also, do you listen vertically on-axis to the B200, or on-axis to the tweeter, or vertically where ?
For the smaller diameter H'phon, you can cut a ring from soft felt of suitable thickness to fill in the gap around the flange,
and that will have audible benefit ... I'll explain more about this if you buy the H'phon.
To find suitable felt, research Saddle Felt and Industrial Felt.
there are 4 or 5 different soft --> medium --> hard grades of felt.
Hard will not absorb sound, but OK if it does not protrude above edge of the flange, though Soft is better,
and if protrudes a little above the edge of the flange it will absorb sufficient sound to improve imaging, etc ...
ClarityCaps will be good with either tweeter.
OW1 should reveal any advantages of better caps if you ever decide to upgrade further, and likely the 9950C-15 will also but perhaps not to same degree ... though all this depends on how far you want to go with capacitors.
Deciding which setting of that 3-position mids' control, and then replacing the old inductor with one to equal your chosen setting
-{or a half-way between settings' estimate if you cannot decide on one}- may give more cost-effective audible result than expensive capacitors.
P.S. - I have that T27 data sheet you posted.
Hi Jonathan,
If you can afford them, then I recommend buying the Hiquphon OW1 as "matched pair", because they are a long-known, proven very good quality tweeter, and a simple variation of the 104 crossover can be used,
as it could also be for the Usher 9950C-15 which the only reservation I have about is that I have not heard them, and they have not been available for as long as the H'phon, BUT the very well-known designer, Joseph D'Appolito, has used that Usher tweeter, {and other Usher drivers}, in his designs, of which some have been very well reviewed.
He can use any brand of drivers he wants to, and I doubt he'd put his name to designs that used drivers that were not good, thus I am reasonably confident the 9950C-15 will be a good tweeter ... but as good as the OW1 ?
... well, it may approach it, but at the higher price and long experience designing tweeters of the H'phon designer, I think OW1 would be better.
The final success or otherwise will be how much tweaking of the crossover you are willing to do if the initial version is not quite what you like best.
Changes may only have to be to resistors.
I'll explain more after you decide a tweeter, though for now what level of treble output do you want ?
The original has about -1dB treble versus mids from the B200, if I'm remembering correctly ... though if you set that mids' knob for full out-put
there will be much higher mids than treble.
With the new tweeter, do you want equal treble to the flattest setting of the mids' knob, or slightly less treble as was the original ?
Also, do you listen vertically on-axis to the B200, or on-axis to the tweeter, or vertically where ?
For the smaller diameter H'phon, you can cut a ring from soft felt of suitable thickness to fill in the gap around the flange,
and that will have audible benefit ... I'll explain more about this if you buy the H'phon.
To find suitable felt, research Saddle Felt and Industrial Felt.
there are 4 or 5 different soft --> medium --> hard grades of felt.
Hard will not absorb sound, but OK if it does not protrude above edge of the flange, though Soft is better,
and if protrudes a little above the edge of the flange it will absorb sufficient sound to improve imaging, etc ...
ClarityCaps will be good with either tweeter.
OW1 should reveal any advantages of better caps if you ever decide to upgrade further, and likely the 9950C-15 will also but perhaps not to same degree ... though all this depends on how far you want to go with capacitors.
Deciding which setting of that 3-position mids' control, and then replacing the old inductor with one to equal your chosen setting
-{or a half-way between settings' estimate if you cannot decide on one}- may give more cost-effective audible result than expensive capacitors.
P.S. - I have that T27 data sheet you posted.
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KEF 104aB characteristics
Hello Allan,
Pleasure to read your reply.
I had the KEF104aB partnered with the Onkyo Integra A722 many years ago. The source was a Diatone turntable/Ortofon VMS20E with Ortofon MC76. The sound of LP was very refined and civilized. It sounded almosy like attending live concerts. Listening to Baroque chamber music was very enjoyable and every little detail was well presented by the KEF104. When playing music by Wagner, Shostakovich the KEF104 was obviously inadequate. For such programs the KEF 105.4 driven by Krell would be more suitable. So now you know what I like to listen to.
I am too old and knackered these days to play LP. So I am using SACD/DAC. I no longer hear/feel the extended highs anymore. (well, not because of my age).
I have contacted Hiquphon and had a short/brief but interesting conversion with Mr. Wrønding. The KEFT27A is electrically very close to the OW1, except the Hiquphon has a much smaller flange. (T27A ø108/ø75mm relative to OW1 ø94/ø68mm). I wouldn't quote everything he said, but I understand that the Hiquphon may sound slightly more forward than the T27A. Then I remember I did own a pair of Linn Kan (black) many years ago which was using the Hiquphon. So I did spent some time listening to Hiquphon. I am ordering a pair (the non-ferro fluid version, which I was told has more transparency). He also hinted that the crossover may require minimal, or no change at all.
I usually listen to the KEF104aB with the knob set to the middle position. I place the speakers on stands. The tweeters are about 6 inches above my ears. The speakers are about 8-9 feet apart toed in, focusing about 6 inches behind my head. Using this setup I get a near life like sound stage for female vocals, as if the singer is standing right in front of me singing. The room acoustics play a part as well. Its an old wooden house with lots of curtains and carpet.
I may make a MDF template to hold the Hiquphon. I intend to bore the 108mm hole on the speaker cabinet thru, flush mount the new MDF template, forever getting rid of the T27a. Well, the main reason for doing so is because KEF uses 3 tapping screws to hold the tweeter. The chip board is disintegrating after all these years, and I am not sure if the tweeter will stay on axis. Starting afresh with a new holder maybe better.
How about using the felt from the KEF LS3/5a?
So I am now all set, getting ready for the crossover change. Again, what do you think about adding a 10ohms/4.7u Zobel to the B200?
Cheers.
Jonathan
Hello Allan,
Pleasure to read your reply.
I had the KEF104aB partnered with the Onkyo Integra A722 many years ago. The source was a Diatone turntable/Ortofon VMS20E with Ortofon MC76. The sound of LP was very refined and civilized. It sounded almosy like attending live concerts. Listening to Baroque chamber music was very enjoyable and every little detail was well presented by the KEF104. When playing music by Wagner, Shostakovich the KEF104 was obviously inadequate. For such programs the KEF 105.4 driven by Krell would be more suitable. So now you know what I like to listen to.
I am too old and knackered these days to play LP. So I am using SACD/DAC. I no longer hear/feel the extended highs anymore. (well, not because of my age).
I have contacted Hiquphon and had a short/brief but interesting conversion with Mr. Wrønding. The KEFT27A is electrically very close to the OW1, except the Hiquphon has a much smaller flange. (T27A ø108/ø75mm relative to OW1 ø94/ø68mm). I wouldn't quote everything he said, but I understand that the Hiquphon may sound slightly more forward than the T27A. Then I remember I did own a pair of Linn Kan (black) many years ago which was using the Hiquphon. So I did spent some time listening to Hiquphon. I am ordering a pair (the non-ferro fluid version, which I was told has more transparency). He also hinted that the crossover may require minimal, or no change at all.
I usually listen to the KEF104aB with the knob set to the middle position. I place the speakers on stands. The tweeters are about 6 inches above my ears. The speakers are about 8-9 feet apart toed in, focusing about 6 inches behind my head. Using this setup I get a near life like sound stage for female vocals, as if the singer is standing right in front of me singing. The room acoustics play a part as well. Its an old wooden house with lots of curtains and carpet.
I may make a MDF template to hold the Hiquphon. I intend to bore the 108mm hole on the speaker cabinet thru, flush mount the new MDF template, forever getting rid of the T27a. Well, the main reason for doing so is because KEF uses 3 tapping screws to hold the tweeter. The chip board is disintegrating after all these years, and I am not sure if the tweeter will stay on axis. Starting afresh with a new holder maybe better.
How about using the felt from the KEF LS3/5a?
So I am now all set, getting ready for the crossover change. Again, what do you think about adding a 10ohms/4.7u Zobel to the B200?
Cheers.
Jonathan
OW1 tweeter
Hi Jonathan,
yes, do order the non-ferrofluid version of the OW1.
I have no difficulty agreeing with Mr W. there.
Ferrofluid causes Inertia around the voice-coil, thus reduces the Transient Response.
Ferrofluid is really only of benefit if one has to drive a tweeter very hard,
and/or has to cross over a bit too low in Frequency or with a too low slope roll-off filter for the tweeter to be able to cope with the additional magnitude of excursion of its voice-coil as result of either.
I'll be back with replies about your other points as soon as I have time available.
Do you own KEF 105.4 also ?
Hi Jonathan,
yes, do order the non-ferrofluid version of the OW1.
I have no difficulty agreeing with Mr W. there.
Ferrofluid causes Inertia around the voice-coil, thus reduces the Transient Response.
Ferrofluid is really only of benefit if one has to drive a tweeter very hard,
and/or has to cross over a bit too low in Frequency or with a too low slope roll-off filter for the tweeter to be able to cope with the additional magnitude of excursion of its voice-coil as result of either.
I'll be back with replies about your other points as soon as I have time available.
Do you own KEF 105.4 also ?
Hello Allan,
I was back from a business trip and could not wait to put on the OWI (used units).
To be honest, I was kinda surprised by the result. It wasn't what I was looking for. 😱
The soft dome sounds so different from a hard dome unit.
I had also bought a pair of T27A circa 1975. Maybe still stick with T27 ...
There are certainly more work to be done. But I don't have the time at the moment. I will be back on business trips again for the next few weeks. 🙁
I don't own the KEF 105.4 , but I own the KEF 105.2, which seriously need to be revived. The bass driver's a gonner.
I was back from a business trip and could not wait to put on the OWI (used units).
To be honest, I was kinda surprised by the result. It wasn't what I was looking for. 😱
The soft dome sounds so different from a hard dome unit.
I had also bought a pair of T27A circa 1975. Maybe still stick with T27 ...
There are certainly more work to be done. But I don't have the time at the moment. I will be back on business trips again for the next few weeks. 🙁
I don't own the KEF 105.4 , but I own the KEF 105.2, which seriously need to be revived. The bass driver's a gonner.
OW1 not with Kef's crossover
Hi Jonathan,
Hiquphon OW1 will not work well with either the Kef 104 or 104aB crossovers, because:
its middle of bandwidth Impedance is a bit lower than a T27,
and its Fs is lower in both Frequency and Magnitude,
thus it will need some changes to the crossover or you will be losing a significant amount of signal in the 3kHz <--> 6kHz region at least,
and maybe broader band loss than that, but with a little louder in the higher treble region.
The aB crossover was specifically tuned to the 1100 Hz Fs of T27A/SP1032 version, and with respect to the magnitude of the Impedance maximum there.
This crossover will only work with a tweeter that has its Fs close to 1100 Hz {1.1kHz} and with a similar Q of Impedance and SPL magnitude there.
The earlier 104 crossover did not ideally match the SP1032, but was likely the closest Kef could get to ideal then at reasonable cost with the limited options of readily available capacitor magnitudes then.
It seems to have been developed from the very similar crossover Kef used for their earlier 900 Hz Fs T27 type 6535.
OW1 has a lower Q of Impedance and SPL magnitude at its specified 850Hz Fs, and as such it does not need a tuned notch in an aB style crossover for the 3kHz crossing.
A simpler crossover of:
Capacitor - Inductor - Capacitor { 3rd Order filter as in original 104}
plus two resistors in L-pad format around the tweeter to get its midband impedance to a suitable magnitude for your Tube amp, and it SPL to match the B200, is sufficient.
I'll post values for all those components if you want to proceed with OW1.
If you convert the crossover, it would be a good idea to add the aB version's resistor of 10 ohms in parallel with the .6mH inductor in the bass/mid filter, because that was part of Kef's revision to get the crossover point to be exactly 3kHz.
The actual crossover point seems to have been a little lower than 3kHz in the original 104, and with not as smooth response through the overlap region where both drivers contribute as was achieved with the aB revision.
If you have sufficient number of T27A now, may as well stay with that.
Are all your T27s the A/SP1032 version ?
or do you have some of 6535 ?
6535 is visually different - it has a very short horn type flare around the dome, and no SP**** number on the back.
There are new unused original T27A in original packaging box available from a Canadian seller for USD$99 + Shipping if you want to pay that.
Alternately, if you want a new model of hard dome you could try Visaton's Ceramic dome tweeter,
though it has a smaller and different shaped chassis than a T27A.
I have heard this Visaton ceramic in two very well designed l'speakers.
The sound is very clear, but these used modern, fast sounding carbon coated paper coned, Scanpeak bass/mid drivers.
With the older B200 bextrene cones the fast response ceramic dome may cause an audible discrepancy you might not like.
I will be experimenting with different tweeters for B200 myself later this year ... when I eventually get time to ...
as I now have two working B200, and four 104 cabinets with good condition ABRs,
though only two working T27A and I'm not sure how close to a pair those T27s sound.
Your OW1 are from your Linn Kan if I have understood correctly .. ?
I have forgotten the sequence of tweeters in the various Kan models.
The original Kan had either T27A or a Scanspeak .. ?
or the second version had the Scanspeak or the Hiquphon .. ?
or possibly a third version had the Hiquphon prior to discontinuation of Kan ..?
A different type of Kan was introduced a few years later, and with reported very different sound to that of the earlier series of models
- of which I heard and liked two pairs, and one more-so than the other, though I forget the tweeters in either.
I have never heard the re-introduced Kan.
Kef 105.4 had a simpler crossover to 105.2, and a reported more transparent sound as result.
Both used the same drivers, thus if you can get your bass drivers repaired or replaced it would likely be worth re-conditioning the crossover to .4 specification.
The KEF LS3/5A you refer to as owning, are these the "Reference 101" or the "CS1A" ?
Hi Jonathan,
Hiquphon OW1 will not work well with either the Kef 104 or 104aB crossovers, because:
its middle of bandwidth Impedance is a bit lower than a T27,
and its Fs is lower in both Frequency and Magnitude,
thus it will need some changes to the crossover or you will be losing a significant amount of signal in the 3kHz <--> 6kHz region at least,
and maybe broader band loss than that, but with a little louder in the higher treble region.
The aB crossover was specifically tuned to the 1100 Hz Fs of T27A/SP1032 version, and with respect to the magnitude of the Impedance maximum there.
This crossover will only work with a tweeter that has its Fs close to 1100 Hz {1.1kHz} and with a similar Q of Impedance and SPL magnitude there.
The earlier 104 crossover did not ideally match the SP1032, but was likely the closest Kef could get to ideal then at reasonable cost with the limited options of readily available capacitor magnitudes then.
It seems to have been developed from the very similar crossover Kef used for their earlier 900 Hz Fs T27 type 6535.
OW1 has a lower Q of Impedance and SPL magnitude at its specified 850Hz Fs, and as such it does not need a tuned notch in an aB style crossover for the 3kHz crossing.
A simpler crossover of:
Capacitor - Inductor - Capacitor { 3rd Order filter as in original 104}
plus two resistors in L-pad format around the tweeter to get its midband impedance to a suitable magnitude for your Tube amp, and it SPL to match the B200, is sufficient.
I'll post values for all those components if you want to proceed with OW1.
If you convert the crossover, it would be a good idea to add the aB version's resistor of 10 ohms in parallel with the .6mH inductor in the bass/mid filter, because that was part of Kef's revision to get the crossover point to be exactly 3kHz.
The actual crossover point seems to have been a little lower than 3kHz in the original 104, and with not as smooth response through the overlap region where both drivers contribute as was achieved with the aB revision.
If you have sufficient number of T27A now, may as well stay with that.
Are all your T27s the A/SP1032 version ?
or do you have some of 6535 ?
6535 is visually different - it has a very short horn type flare around the dome, and no SP**** number on the back.
There are new unused original T27A in original packaging box available from a Canadian seller for USD$99 + Shipping if you want to pay that.
Alternately, if you want a new model of hard dome you could try Visaton's Ceramic dome tweeter,
though it has a smaller and different shaped chassis than a T27A.
I have heard this Visaton ceramic in two very well designed l'speakers.
The sound is very clear, but these used modern, fast sounding carbon coated paper coned, Scanpeak bass/mid drivers.
With the older B200 bextrene cones the fast response ceramic dome may cause an audible discrepancy you might not like.
I will be experimenting with different tweeters for B200 myself later this year ... when I eventually get time to ...
as I now have two working B200, and four 104 cabinets with good condition ABRs,
though only two working T27A and I'm not sure how close to a pair those T27s sound.
Your OW1 are from your Linn Kan if I have understood correctly .. ?
I have forgotten the sequence of tweeters in the various Kan models.
The original Kan had either T27A or a Scanspeak .. ?
or the second version had the Scanspeak or the Hiquphon .. ?
or possibly a third version had the Hiquphon prior to discontinuation of Kan ..?
A different type of Kan was introduced a few years later, and with reported very different sound to that of the earlier series of models
- of which I heard and liked two pairs, and one more-so than the other, though I forget the tweeters in either.
I have never heard the re-introduced Kan.
Kef 105.4 had a simpler crossover to 105.2, and a reported more transparent sound as result.
Both used the same drivers, thus if you can get your bass drivers repaired or replaced it would likely be worth re-conditioning the crossover to .4 specification.
The KEF LS3/5A you refer to as owning, are these the "Reference 101" or the "CS1A" ?
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KEF 104 tweeter replacement
Hello Allan
I never expected a dead T27A to pull me back into KEF 104's history, and development into the 104aB, and subsequent speaker designs. I own several KEF speakers of the 70s for over 25 years. Nevertheless, it has been a very enjoyable re-leaning experience.
Many modern speaker designs still continue the fundamentals of KEF 104 type C-R-C third order cross over. With an R-R dividing net work and possibly impedance compensation Zobel net work as addition. Also. most of modern crossover uses poly caps than non polar electrolytics.
Certainly the Hiquphon was not working with the correct crossover. What struck me was the sound of soft dome fabric tweeters as opposed to hard dome ¾ inch tweeters. Their sound characteristics are basically different by nature. While the fabric type is smooth like silk, they lack the metallic bite and brilliance like those of hard dome tweeters. There is nothing wrong with the Hiquphon OW1. I am sure it can be a superb upgrade. But I still am looking for a close resemblance of the T27A. The T27A makes the 104 magical.
These Hiquphon were bough as used units when I was traveling in Japan recently. They were taken from old Linn speakers, so I presume it was from the old Kans. The seller wasn’t very clear in his descriptions, and I did not understand many things he said. Anyway, I can always use them again in a separate project.
I have sold my old Linn speakers many years ago. I remember I preferred the LS3/5a or KEF 101 than the Linn, so I sold it for a good price. Yes, the Kans had a series of different tweeters. I wonder how they managed to keep the flavor consistent.
When I was in Japan I heard a pair of knock off KEF LS3/5a from China. The shocking thing was it was able to achieve about 90% of the sound of a real pair of Rogers LS3/5 (side by side), BUT with only 1/10 the price of the Rogers. I arranged a pair to ship back to US, and need to spend some time studying it. I have the KEF LS3/5a with the falcon crossover installed. I have the technical data sheet of the CS1A. Yes, the CS1A, 101 and LS3/5 all sound very different.
One car audio fanatic suggested to me the use of the Seas prestige series 22TAF/G H1283 as T27A replacement. It has a 3/4inch metallic dome, and also exhibits a 1.2 kHz free air resonance like the T27. Faceplate is at 98mm, close to the 108mm T27. Frequency response is well up to 30 kHz. The sensitivity can be a little high, but can be attenuated by a series resistor. The sensitivity was measured by a 2.83V input. I may get a pair and try them out.
http://www.europe-audio.com/document.asp?document_id=1700&link=datasheets\seas\h1283.pdf
All of my T27A are either of 1975 vintage or latter from KEF constructor kits. There are still a good number floating around from the dreadful Epay site. I do not favour the 6535 because of their age, and also those I found in the market now usually may have some flaws one way or another.
I find the 104 cabinets shabby. The veneer can be tarty after being exposed to moisture. I spent more time trying to restore the wood work, than working on the electrical aspects.
KEF105.2
Sometime in the 80s, I surgically removed the big caps in the 105.2. I thought they were for DC blocking and would rob away the details of the speakers. I think I made a mistake as those caps were there not just for protection; they also were bass boost for the bass units. So I listened to a pair of lame 105.2 all my life. WTF . I also removed the S Stop circuit as I did not like the ‘devil’s eyes’ flashing at times.
Yes, it will be good to restore to 105.4. But I remember the 105.4 were using 2 x 8 inch woofers?
It will be good if you can share the crossover details using the OWI.
What about the original aB crossover?
Thanks and regards.
Jonathan
Hello Allan
I never expected a dead T27A to pull me back into KEF 104's history, and development into the 104aB, and subsequent speaker designs. I own several KEF speakers of the 70s for over 25 years. Nevertheless, it has been a very enjoyable re-leaning experience.
Many modern speaker designs still continue the fundamentals of KEF 104 type C-R-C third order cross over. With an R-R dividing net work and possibly impedance compensation Zobel net work as addition. Also. most of modern crossover uses poly caps than non polar electrolytics.
Certainly the Hiquphon was not working with the correct crossover. What struck me was the sound of soft dome fabric tweeters as opposed to hard dome ¾ inch tweeters. Their sound characteristics are basically different by nature. While the fabric type is smooth like silk, they lack the metallic bite and brilliance like those of hard dome tweeters. There is nothing wrong with the Hiquphon OW1. I am sure it can be a superb upgrade. But I still am looking for a close resemblance of the T27A. The T27A makes the 104 magical.
These Hiquphon were bough as used units when I was traveling in Japan recently. They were taken from old Linn speakers, so I presume it was from the old Kans. The seller wasn’t very clear in his descriptions, and I did not understand many things he said. Anyway, I can always use them again in a separate project.
I have sold my old Linn speakers many years ago. I remember I preferred the LS3/5a or KEF 101 than the Linn, so I sold it for a good price. Yes, the Kans had a series of different tweeters. I wonder how they managed to keep the flavor consistent.
When I was in Japan I heard a pair of knock off KEF LS3/5a from China. The shocking thing was it was able to achieve about 90% of the sound of a real pair of Rogers LS3/5 (side by side), BUT with only 1/10 the price of the Rogers. I arranged a pair to ship back to US, and need to spend some time studying it. I have the KEF LS3/5a with the falcon crossover installed. I have the technical data sheet of the CS1A. Yes, the CS1A, 101 and LS3/5 all sound very different.
One car audio fanatic suggested to me the use of the Seas prestige series 22TAF/G H1283 as T27A replacement. It has a 3/4inch metallic dome, and also exhibits a 1.2 kHz free air resonance like the T27. Faceplate is at 98mm, close to the 108mm T27. Frequency response is well up to 30 kHz. The sensitivity can be a little high, but can be attenuated by a series resistor. The sensitivity was measured by a 2.83V input. I may get a pair and try them out.
http://www.europe-audio.com/document.asp?document_id=1700&link=datasheets\seas\h1283.pdf
All of my T27A are either of 1975 vintage or latter from KEF constructor kits. There are still a good number floating around from the dreadful Epay site. I do not favour the 6535 because of their age, and also those I found in the market now usually may have some flaws one way or another.
I find the 104 cabinets shabby. The veneer can be tarty after being exposed to moisture. I spent more time trying to restore the wood work, than working on the electrical aspects.
KEF105.2
Sometime in the 80s, I surgically removed the big caps in the 105.2. I thought they were for DC blocking and would rob away the details of the speakers. I think I made a mistake as those caps were there not just for protection; they also were bass boost for the bass units. So I listened to a pair of lame 105.2 all my life. WTF . I also removed the S Stop circuit as I did not like the ‘devil’s eyes’ flashing at times.
Yes, it will be good to restore to 105.4. But I remember the 105.4 were using 2 x 8 inch woofers?
It will be good if you can share the crossover details using the OWI.
What about the original aB crossover?
Thanks and regards.
Jonathan
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OK back again! 😱
Thanks Allan for your amazing post. People pay good money for that quality of advice! So here I am about a year and a half later up and working on this one again. I was searching around looking to confirm my readings of the crossover and found this post. And I thought dam this is exactly what I need to read, then I realized that it was a thread that I had started. You know you spend a lot of time on the Internet when..
OK so I have come to the conclusion that there is no way in hell I am going to build my own crossover from scratch no matter how much and how generous the help. So I have decided to buy an active crossover and a pair of amps and go with that. At the moment the temporary setup is an ART SLA2 and Alesis RA150 coupled with the DBX Driverack PX. I have been going over crossover settings and tweaking away. It feels pretty close at this point. The system is going to get changed up in about two weeks. I plan on buying another RA150 to replace the SLA2 and the Driverack PX will be replaced with a Behringer Ultradrive Pro.
I have to say that on first impressions this rig is sounding pretty dam good.
That is all for now but Ill keep updating this thread along to way with any helpful information I might come up with.
Thanks Allan for your amazing post. People pay good money for that quality of advice! So here I am about a year and a half later up and working on this one again. I was searching around looking to confirm my readings of the crossover and found this post. And I thought dam this is exactly what I need to read, then I realized that it was a thread that I had started. You know you spend a lot of time on the Internet when..
OK so I have come to the conclusion that there is no way in hell I am going to build my own crossover from scratch no matter how much and how generous the help. So I have decided to buy an active crossover and a pair of amps and go with that. At the moment the temporary setup is an ART SLA2 and Alesis RA150 coupled with the DBX Driverack PX. I have been going over crossover settings and tweaking away. It feels pretty close at this point. The system is going to get changed up in about two weeks. I plan on buying another RA150 to replace the SLA2 and the Driverack PX will be replaced with a Behringer Ultradrive Pro.
I have to say that on first impressions this rig is sounding pretty dam good.
That is all for now but Ill keep updating this thread along to way with any helpful information I might come up with.
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