KEF T33 tweeter replacement for 104/2

centaurus3200

Well-Known Member
i did a search and found some good info, but am curious if anyone has any updates on their findings.

as many KEF owners with ferro-fluid cooled tweeters know, the gel hardens over 20 years and basically renders the tweeters useless. i recently traded my Bozak 302A Urbans for a pair of 104/2. should have hooked the KEFs up while the guy was here, but such is life. he's really nice and offered to give me cash to buy the KEF recommended replacements.

but, I've heard KEF's replacements are both overpriced ($160/pair) and don't even sound that great. as you know, the 104/2 has the tweeter mounted flush behind the mid/tweeter baffle. i do not want to alter the outside of the baffle, but have no problem tweaking it from inside to mount a suitable, if not better replacement. i mean $160 buys you some pretty fricken nice tweeters ;-)

so, what have you guys tried successfully? the tweeter is 1.25", but i can go smaller if necessary. i believe they are 4 ohm. overall sensitivity is rated at 92db at a 4ohm load.

specs: http://www.kef.com/history/1980/model104_2.asp

thanks,
Robby
 
One of the speaker companies in GB for a while was showing a Peerless tweeter as a screw-in replacement for the T33. For the life of me, I can't find that link now. I'll keep on looking.

Solen in Canada at the time had them for about $US 30-35 each.

T-33A's come up every now and then on that auction site......

I'll post again if I can find the replacement.
 
thanks you for your efforts!

does anything from madisound.com ring a bell?

Robby

kdlsoft said:
One of the speaker companies in GB for a while was showing a Peerless tweeter as a screw-in replacement for the T33. For the life of me, I can't find that link now. I'll keep on looking.

Solen in Canada at the time had them for about $US 30-35 each.

T-33A's come up every now and then on that auction site......

I'll post again if I can find the replacement.
 
Shot a fast email to sales@wilmslowaudio.com (www.wilmslow-audio.co.uk) about the T33 replacement and got this reply:

"Robert
The replacement unit was a Peerless 811528 which has now been discontinued.
We have only one remaining unit in stock, the price would be £30 plus p&p Regards Terry"

Solen in Canada HAD them, don't know if they do now or who else might.

Solen part number 94DT2608 "international pricelist" $US 16.38. Don't know what their stock level may be (if any).

Bob
 
Terry suggested to me the following last night...

Robert
The unit that we have successfully used in the 104/2 is a Morel MDT29
at £26 each. This unit will operate with the front faceplate removed and will fit
into the same position as the original.
Regards
Terry

Madisound has them. is he just scrambling to think of something that will work or has he tried. odd being he never mentioned the morel in your email to him?

worth a shot though if you all think it will work. Morel makes some really nice drivers. what do you think would sound better in the 104/2? could just buy both and try them with alligator clips. return the morels if i decide on the peerless. how would both of these comapre to the T33 or KEF's replacement? i could buy a T33, but they are probably all shot now because of the hardened cooling gel.

Robby
 
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Another crazy idea. Why not clean the ferrofluid off with a solvent and use it without...? Dome tweeter diaphrams generally self center after the magnet is unscrewed.
 
i'm definitely gonna give it a try, but i think i will buy some suitable aftermarket tweeters from morel regardless. i've heard from people that have tried to clean out the tweeter, that it helps a lot, but still doesn't get them to have "like-new" output.

Robby

Nakdoc said:
Another crazy idea. Why not clean the ferrofluid off with a solvent and use it without...? Dome tweeter diaphrams generally self center after the magnet is unscrewed.
 
The fluid supposedly improves the efficiency a bit. There used to be a source for ferrofluid. In the Manchester NH airport there is a ferrofluid exhibit placed there by the company that makes the stuff. Why not ask them?
 
it's done, i've made my choice and im sticking to it ;-)

Well, after some research, i tend to agree that both the T33 was never that great and that the KEF replacement is both overpriced and underwhelming. so, i bought a pair of Morel MDT30 tweeters. hopefully they will mate well. wimslow audio uses the MDT29, but the folks at madisound said the 30 will fit the same and sound even better.

yeah, i read lilke 7 reviews on the 107 and 107/2 on stereophile online and all said that the tweeter detracted from an otherwise incredible loudspeaker.

besides, madisound has a great return policy, so worth a shot.

Robby
 
if they sound decent, just use them. it was quite obvious on mine that there was little output coming from them. the ferro-fluid hardens over time and kills the tweeter output. this condition worsens if they have been blasted on many occasions.

i bought some Morel MDT30 but they have a rear chamber and did not fit. i sent them back and have some MDT29 on route. the MDT29 has been tried many times by terry at wimslow audio in the UK with great success. he even says they sound much better than the T33.

the morels are 8ohms at 89 db. the T33b is 92 db at 4 ohms. when the KEF group questioned terry, he said he did not have much faith in KEF's sensitivity measurments. plus, from my knowledge, 89db at 8 ohms is equivelelnt to 92db at 4 ohms. terry stands by the morels.

Robby
 
I think Parts Express had ferrofluid.

If the T33b is 92 db at 4 ohms, 1 watt, that is 2 volts.

If the Morel is 89 db SPL, 8 ohms, that is for 1 watt. One watt into 8 ohms is 2.83 v.

If you put 2 volts into an 8 ohm load, it would produce only 1/2 watt. Half power into the Morel would then produce 86 db. So, the T33b would make 6 db more sound for the same voltage input.

For a 4 ohm driver to have the same output at 2.83 v as an 8 ohm driver, the 4 ohm driver's SPL should be 3 db less than the 8 ohm driver's SPL.
 
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we'll see. i'll trust terry. i have no choice. from my experience on the KEF forums, the T33b are not repairable. any attempt to clean out the hardened ferro-fluid and put new fluid in has resulted in better performance, but still not original output.

i thought that an 8 ohm speaker that is 89 dB/watt efficient also has a sensitivity of 89 dB/2.83 volts. But a 4 ohm speaker that is 89 dB efficient will have a sensitivity of 92 dB, because 2.83 volts into a 4 ohm load is 2 watts instead of 1 watt. 2.83 volts is the constant, not the variable.

so, true the t33b would be 92 db sensitive, but at 2 watts at 2.83 volts. the MDT29 would be 89 db efficient, but at 1 watt for 2.83 volts. so, they would be 3 db down, but require half the power, therefore be the same sensitivity. i have the spec sheet on the T33b. it's rated at 92db at 4 ohms. so, you are saying i'd need an 8 ohm speaker that is 98db at 8ohms? that's not going to happen.

but, hearing is believing. there are not many 4 ohm tweeters that will work because you have to remove the flange to fit behind the baffle in thw mid/tweeter enclosure in the 104/2. if the tweeters sound soft, then i'll have to revise the crossover. i'm pretty sure the MDT29 is the only tweeter that will fit with out any modifications to the enclosure. the only 4 ohm tweeter is KEF's suggested replacement which is like $240. they sound really hot and sibilant in 104/2 from what i hear.

again, i am not sayng you are wrong. in fact, i'm probably wrong. but either the morels sound acceptable or i'm selling the 104/2. life's too short to endlessly fart around when i have other speakers to listen too. i do find it totally absurd that KEF has left their loyal customers with true classic KEF gear hanging.

Robby
 
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16 ohm speakers are rated at 4 v (1 watt). Are you sure the KEF's are rated at 2.83 v? Or are they rated at 2 v? makes a difference.
 
their specs from various speakers on KEF's history section all seem to be 2.83 volt for their 4 ohm speakers. the specs for the 104/2 just say 92db. nothing else.

you know more about this than i, but being the other drivers are 4 ohm and the crossover is conjugate loaded. the tweeter will still be 8 ohm even on the 4 ohm tap. not sure what this means for their response though. for reference, i am using mcintosh MC60s tube amps. so, i can run the speakers on the 4 or 8 ohm tap. the back of the speakers say 100 watts at 8 ohms or 200 watts at 4 ohms. weird being if they are 4 ohm speakers, they should run on 4 ohms only, right? not that it would hurt the speakers on the 8 ohm tap.

an audioaslym member does use and enjoy morel MDT30 (90db) on his 4 ohm KEF C80. which are also conjugate loaded. teh C80 are 89db though at 4 ohms. which might make sense because when he pulled the dead T33 tweeters, his were rated at 6 ohms.

bah, my head hurts. i'll let you know how they sound with the MDT29. if they suck, i have 3 choices. keep searching, mod the x-over (which i don't know how to do) or just sell the fricken things ;-)

can you find a suitable tweeter? i don't think anybody makes a 4 ohm tweeter with a removable front flange.

Robby
 
Well,

i finally got some time to rig in the morel MDT29 tweeters last night. keep in mind that i have never heard stock 104/2. so, i just compared to my KEF Calinda.

well, there's a very good reason why terry only recommends the mdt29. it's literally the only thing that would fit. and it doesn't really fit. let me explain.

the T33 tweeter fits right between the two B110 midrange enclosures. it's held in place by a wooden plate on a track and a pressure bolt. anything with a magnet structure wider than 68mm will not fit as it has to wedged between the two enclosures. the height can not be taller than something like 26mm.

as it stands, the morel is 1mm too high, so the back of the magnet hits the metal thread on the wooden plate. so, i slid the plate over until the thread hit the magnet. used mounting double stick tape (heavy duty and thick). the tweeter won't budge.

i used alligator clips to listen. i can't solder, because once i do, i can not return the tweeters if i decide i don't like them.

so, now for the listening...

it was quickly apparent that my McIntosh MC60 tube amps did not have enough current to maintain decent dampening of the woofers on the 4 ohm tap. coupled with the fact that the 8ohm morels would be 3db down on the 4ohm tap, i quickly hooked the speakers up on the 8 ohm tap. ahhh, much better!

the morels are very smooth. a bit compressed sounding, but i think they will open up once they get broken in. they are not as bright nor as forward as the T27 in my Calindas. but the morels are extended and blend nicely with the B110 mids. are they a match made in heaven? no, mainly because the morels are 89db at 8ohm. i believe they are fairly closely matched to the other drivers, but they could stand another 1-2 db of sensitivity. still, compared to the comments ive heard for KEF's recommended replacement tweeter, the morels are 60% cheaper and much smoother.

so, where does that leave me? i have to listen more, but i am thinking of trying some 4 ohm 93.5db sensitive Vifa DX25TG05. i'm waiting to hear from madisound what the width is. it is not specified in the spec sheet. if it's more than 68mm, NO tweeter will fit. then i will just live with the morels. but the vifa DX25TG05 specs sound very close to the T33B.

other issues i noticed is that one of the mids distorts a little. not in a blown way, but in a voice coil rubbing way. it's minor. don't you KEF guys turn the drivers upside down to recenter the VC?

see ya,
Robby
 
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