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Old 6th June 2015, 12:30 AM   #1
seadoo is offline seadoo  United States
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Default kef 104/2

I just bought a used set and the original tweeters had been changed out to the Morel MDT29 4 ohm tweeters. This seems to be a common replacement but I was hoping to find something better. The Morels sound "forward" if that is the correct term. I am trying Kef T33 SP1197 at the moment. They us a smaller magnet so a thin spacer behind them is required to mount them. They sound more neutral than the Morels but I'm going to have to listen to them for awhile before I know if I'm going to stick with them. Has anybody found a better match for 104/2's.
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Old 6th June 2015, 01:26 AM   #2
system7 is offline system7  United Kingdom
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The Kef T33 SP1197 is the original 4 ohm tweeter, AFAIK.
Explore KEF - Reference Series Model 104/2 - KEF United Kingdom

The Morel MDT29 4 ohm is a suitable replacement by all accounts:
https://www.youtube.com/watch?v=YlZuaTBnzLQ

The Morel has a removeable front faceplate that makes this doable, but as you say, the spacing needs some bodging.

Nevertheless some sensitivity adjustment is often needed. You could either put an ohm or more in front of the tweeter filter to take the Morel down at the top end, or fit about 1 ohm/10ohm attenuator to generally reduce output if it sounds forward. We are talking a couple of dB here. I've used this tweeter in 8 ohm version so I know what it sounds like. Taking out the 10uF in the tweeter filter out would reduce the very top output a bit too.

Getting tweeter level right is one of the more critical adjustments. Often a single dB will make or break. Soft domes are soft domes IMO. They all sound much the same. I see a reasonable stab at one of KEF's 4 ohm filter below. Not sure how the Martin Colloms quoted R104II schematic relates to your model, but the 3rd order tweeter filter is as expected for 4 ohms.
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Last edited by system7; 6th June 2015 at 01:32 AM.
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Old 6th June 2015, 01:50 AM   #3
seadoo is offline seadoo  United States
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The sp1191 is the original and the sp1197 has a smaller magnet. I might try to adjust the level of the morel down a couple db.
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Old 6th June 2015, 02:02 AM   #4
system7 is offline system7  United Kingdom
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I don't know how well I can describe this, but you could listen to the Morel 30 degrees off axis, and if it then sounds reasonable, that suggests it's the very top around 10kHz that needs taming. A zobel around 6 ohms and 2uF might do that as an alternative to taking out the 10uf. You could even remove the 10uf and add the zobel for a serious impact on the very top end without mucking up impedance.
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If it's still forward around 3kHz, the whole thing needs attenuating. Presumably the T33 SP1197 is just quieter than the SP1191. But it would be worth measuring its DC resistance.

I certainly hate an overly bright speaker. But there is always the issue of whether the speaker is designed to be toed in to the listener or pointed straight ahead for best result, because top end dispersion inevitably falls off off-axis.
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Last edited by system7; 6th June 2015 at 02:24 AM.
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Old 6th June 2015, 05:43 PM   #5
Eldam is offline Eldam  France
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I don't know if this tip is important for the acurate tonal balance :the Kef 104/2 were optimized for a front wall at around 60 cm of the speakers (never knew if it was from the rear side or the front side !).

Mine (first mono wired model) sound good and not shiny with the original tweeter. It rocks, but not in all rooms... I find them to be a snapy and dynamic speaker despite its poor 50 Hz at -2 db and its mat treble... mid-bass is very pleasant.... hum off topic but just to say you don't need climbing treble for a snapy mid-bass with this speaker !

Last edited by Eldam; 6th June 2015 at 05:48 PM.
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Old 6th June 2015, 06:15 PM   #6
seadoo is offline seadoo  United States
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I tried using the morel in one speaker and the Kef sp1197 in the other and did some listening tests. I'm going to remove the morel and install the other sp1197. The morel just doesn't match as good as the sp1197 to the midrange units. I have them about 2' from the back wall and about 6' from the side walls. The room is about 16' X 20'. I've tried two different amps with the same results. A Yamaha A-1020 and a Dynaco st-70.
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