Today I have installed the Audax TW025A2 tweeter and is has a better connection with the mid driver. I have compared the two by switching in mono from the speaker with the Audax and the other one with the T33, The Audax sounds better, more relaxed and detailed.
I have routed the back of the Mid/High unit so that the Audax have a flat surface where it can be mounted on.
The Audax have the screw heads sticking out so the have to be adjusted that the head is flat.
some insulation tape on the surround and the tweeter fits nice flush as the T33 is mounted. No gap like other replacement tweeters have.
Also the mounting plate will slide over the Tweeter without further modification.
I have routed the back of the Mid/High unit so that the Audax have a flat surface where it can be mounted on.
The Audax have the screw heads sticking out so the have to be adjusted that the head is flat.
some insulation tape on the surround and the tweeter fits nice flush as the T33 is mounted. No gap like other replacement tweeters have.
Also the mounting plate will slide over the Tweeter without further modification.
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better to remove the screw and use glue or blue tack between the cone structure and the magnet core to save you few millimeters with the enter of the kef tweeter small cone 3 cm iirc.
What also you experiment is the old T33 as being old. Do not forget to adapt the 7.5 uF cap value to the impedance of the Audax around 3 Khz.
Is it not a good speaker , Worth all your effort, took me sometimes to refurbish one which was in good condition, the filter is not easy (most being the bass notch capacitances values where Falcon Acoustic can not help really with their kit made only on the filter datasheet
What also you experiment is the old T33 as being old. Do not forget to adapt the 7.5 uF cap value to the impedance of the Audax around 3 Khz.
Is it not a good speaker , Worth all your effort, took me sometimes to refurbish one which was in good condition, the filter is not easy (most being the bass notch capacitances values where Falcon Acoustic can not help really with their kit made only on the filter datasheet
The audax has the same electrical specifications and at this moment there is no need to change the filter.
The difference in sound is close only at the cross-over frequency i hear that the audax is the better speaker here.
The details and overal performance with the audax is more plassend to listen to. I do not trust the current microfoon I have, I see if i can borrow another so I can compare the two and see if the filter needs some adjustments.
The difference in sound is close only at the cross-over frequency i hear that the audax is the better speaker here.
The details and overal performance with the audax is more plassend to listen to. I do not trust the current microfoon I have, I see if i can borrow another so I can compare the two and see if the filter needs some adjustments.
I don't see anything usefull in the first picture about a precise impedance around the frequency of the interest, the scale is not precise enough if the numbers are at rigt of the picture. The second picture is the same I have, I kept around 3.25 ohms around 3K.
It will be usefull to find the Audax's around that to adapt the filter. If close enough, can be made by listening. Alas we both know all the work needed to acess to the filter in this loudspeaker. Be prudent with Falcon Acoustic aproximation as the filter of this loudspeaker was made with a huge precision and matched.
Good luck. Don't bother if you find it good enough in your whole setup, trust your ears
It will be usefull to find the Audax's around that to adapt the filter. If close enough, can be made by listening. Alas we both know all the work needed to acess to the filter in this loudspeaker
. Be prudent with Falcon Acoustic aproximation as the filter of this loudspeaker was made with a huge precision and matched.Good luck. Don't bother if you find it good enough in your whole setup, trust your ears
Did you finally measure the impedance of the new Audax raw ?
Strange how high are the ESR of the LL caps ! As if they suffer more than others !
C2 C3 C6 C7 are all 100 uF marked on the 104.2 I refurbished. The 112 uF marking is odd. While they sorted out the values for the same whole result... maybe they were both 106 in real when fresh on mine... I don't know
The values iirc was more around 103 uF but the huge difference with fresh caps was certainly the better ESR as the sound changed for the best after...
There is chance the 16 uF cap is the double of the first 7.5 in real life (4th order).
Finding these values at listening was important in mine for the equilibrium hence my advice to find the impedance of the Audax if you can measure it at the said frequency or to find it with try & error.
Strange how high are the ESR of the LL caps ! As if they suffer more than others !
C2 C3 C6 C7 are all 100 uF marked on the 104.2 I refurbished. The 112 uF marking is odd. While they sorted out the values for the same whole result... maybe they were both 106 in real when fresh on mine... I don't know
The values iirc was more around 103 uF but the huge difference with fresh caps was certainly the better ESR as the sound changed for the best after...
There is chance the 16 uF cap is the double of the first 7.5 in real life (4th order).
Finding these values at listening was important in mine for the equilibrium hence my advice to find the impedance of the Audax if you can measure it at the said frequency or to find it with try & error.
We have done some measurements on the Kef 104/2, The T33 and the Audax tweeter.
The total story is here in dutch, i will post the highlights here below.
Restauratie KEF Reference 104/2 - Pagina 17 - forum.zelfbouwaudio.nl
The measurements have been performed by Pappaleo.
At first the Impedance response Green T33 Yellow The Audax
The second is the frequency response close range
Yellow the Audax red the T33
The next measurement is the total speaker measured outside to avoid reflections
Red T33 Yellow Audax.
You can see that the audax have some more output.
i will adjust the audax with 2.5dB so it will be more in line with the total output.
The measurement is done without the cover.
The total story is here in dutch, i will post the highlights here below.
Restauratie KEF Reference 104/2 - Pagina 17 - forum.zelfbouwaudio.nl
The measurements have been performed by Pappaleo.
At first the Impedance response Green T33 Yellow The Audax
The second is the frequency response close range
Yellow the Audax red the T33
The next measurement is the total speaker measured outside to avoid reflections
Red T33 Yellow Audax.
You can see that the audax have some more output.
i will adjust the audax with 2.5dB so it will be more in line with the total output.
The measurement is done without the cover.
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Thanks for sharing.
That's what I thought it was not a drop in but for the body size. And also th short horn load of the front baffle is making the exercice difficult. there was a synergy between it and the T33 made in the development design for sure, also a little for time aligmement perhaps.
When refurbished fine, the Kef 104/2 disseaper easily from the soundstage.
I believe you are near the end of that good road.
That's what I thought it was not a drop in but for the body size. And also th short horn load of the front baffle is making the exercice difficult. there was a synergy between it and the T33 made in the development design for sure, also a little for time aligmement perhaps.
When refurbished fine, the Kef 104/2 disseaper easily from the soundstage.
I believe you are near the end of that good road
.
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attached measured response of both tweets with ff removed (green, black) and with ff (red). does not look like what it should be
The red graph shows the behaviour of a jammed VC or dried FF but a much too high viscosity of the FF behaves the same. The measurement from KEF and your black and cyan (green-ish) measurement differs in 3 things:
1. the grid of your response is 5dB/line while the KEF datasheet is 10dB/line, which flattens the curve. The KEF is also smoothed.
2. In comparison it shows quite the same characteristics, the peak on the top end is higher on your measurement, that's likely because of a difference in measurement enviroment and tolerance on the mic, preamp, missing or just generic calibration file. Maybe you've used a class-D amp for measuring, which would explain the moderately rised peaks too.
On the datasheet the peak is ~5dB, in your measurement it's 6-7dB, that's well in the normal tolerances. It doesn't matter much because off axis it very quickly drops in level and in that range the human ear isn't very sensitive to linearity and the difference is likely just tolerance or just different measurement enviroment and chain.
3. The lower spl below 3kHz is largely because KEF measured the tweeters in a large standard baffle while you measured them either in the box, in the unit baffle or completely without baffle. With a large baffle the reflection on the edge of the baffle boosts the lower frequencies, the baffle step frequency goes up with smaller baffles. A high viscosity of the ferrofluid could cause that too but will change after the speaker played for a while (warming up the oil).
What's not okay is the impulse response. For a high quality soft dome tweeter that's a pretty bad response. You should measure the spectrum decay and distortion, from that response there will be extremely likely serious ridges in both. It will also show on the impedance response if you can't do the distortion measurement.
Reasons are probably a decentered or rubbing VC, too high viscosity of the FF or some dirt in the gap. To verify that remove the FF and measure again.
At that age it's also possible (though not likely) the VC/dome glue seam came partly off, you can maybe see that from the side with a lamp from the back of it.
BTW: Without the FF the tweeter will show a better resolution but the impedance response will be different and the crossover has to be changed.