WTB a good 25 mm voice coil dome tweeter?

[diyiggy]

Hi,

Refurbishing an old Kef tweeter, I'm looking for a 4 ohms textile tweeter 1" tweeter dome ! No screw but adhesive double tape method.
Good power handling needeed. (200 watts)

Any idea of a place to shop please ? I assume the Qtm and the Xmax has to see with the dome/suround/plate assembly.

Voice coil is 4 ohms and exactly 25 mm diameter. 27 mm textile dome, 30 mm with suround shaped from the fabric.
I thought about some brands, as Audax, Morel, but has mostly no idea and where to look for to have some choice... Better to buy a new tweeter with close spec. or better to change the dome to keep the spec of the motor ?


Many thanks,

 

[hifijim]

what kind of sensitivity do you need? If you need a minimum 88 dB/2.83 V, you have a lot of choices... if you need 92 dB/2.83 V, your choices get more limited...

This is only the first question to be answered in finding a replacement tweeter...

 

[Galu]

This KEF history article may identify the tweeter and help pick a replacement.

https://us.kef.com/pub/media/pdf/A_History_of_Kef_Drive_Units_issue_3.pdf

Wilmslow Audio offer some suggestions when it comes to replacing KEF T27 and T33 tweeters.

 

[xrk971]

RST28A-4? Measurements look very nice. 92.5dB.

https://www.parts-express.com/pedocs/specs/275-131--dayton-audio-rst28a-4-specification-sheet.pdf

Or for textile, the RST28F-4. 93dB and measures very well too. I have tested this one - sounds great. Extreme value.

https://www.parts-express.com/pedocs/specs/275-141--dayton-audio-rst28f-4-specification-sheet.pdf

 

[diyiggy]

Thanks guys for chiming in,

93 db, T33 tweeter ! voice coil material looks like aluminiumI assume a 92 dB will do...

My concern is I would like to keep the power handling and don't know if it has to see with the voice coil construction, idem for the resonant frequency !
I thought about Audax voice coil spare part but the model of tweeter it refers to is 80W.

So main problem is to find a 27 dome,voice coil 25 mm spare part to keep the motor : bad idea as I don't want to mess with filter reworking : Fs has to see with the voice coil/dome & surround or the main motor, gap and construction ?


I know there are candidate as the good Dayton above, the rare Morel 298-04, or the Audax TW025A2 4 ohms ! But the T33 has a 1.6 Tesla engine... can handle 200 W !



Nothing left at Falcon Acoustic GB.

 

[diyiggy]

I also lurked for a Seas No Ferro 900 : but it's a 6 ohms 92 db : but think it can handle 200 W ! So after some conversion : gives a 93,5 4 ohms equivalent spl ?

 

[markbakk]

I guess you're looking for a VCA (voice coil assembly) are you? Scanspeak/Peerless/Vifa used to have them, inner diameter 25,8mm though. Checked eBay?

 

[diyiggy]

I'm afraid by Ebay, no quality guarantee for spare parts often but offical shops there...

 

[Dave R]

Perhaps this option -
Morel MDT29-4 (4 ohm) Textile dome tweeter

 

[diyiggy]

yup that's the one I think about when I write 298-4 😉


A lttke coplicate those days to ship from US to CE... can be veeeeeery long fr such things here !

 

[diyiggy]

I am beginning to think at a 40 euros old second hand Kef monitors just to keep the voice coil/dome...don't want to hassle with filters...

 

[diyiggy]

Does anyone now what is the Fs origin of a dome tweeter please ? Is it only dues to the dome/voice coil material and dome surround ? I.e. mechanical origin or electrical as well due to the motor/magnet main tweeter ?

 

[Lojzek]

What is exactly wrong with your t33 tweeter?

 

[diyiggy]

wire of the VC broke, no posibilit to unwind (soldered where it is broken)


think about this VC : Diaphragm Audax TW025A10, 4 ohm : the Audax tweeter that uses it is 94 db, so assume it has a good power handling ? And it is impregnated dome....

 

[Lojzek]

Then your best bet is to search for a second hand unit of the same brand and model.

 

[diyiggy]

thanks, so the Fs is about and spl curve is about the vc/dome ?


I assume the coating when light is agging too ?


Well who knows, by chance I may find one ane day.

 

[JMFahey]

I am beginning to think at a 40 euros old second hand Kef monitors just to keep the voice coil/dome...don't want to hassle with filters...

Best option.

Unless a factory issued replacement diaphragm or a serious GUARANTEED replacement and aftermarket spare will not be tyhe same.

You can repair woofers, no big deal, but tweeter voice coils are too short, plates too thin ,a 10th of a millimeter misplacement will start affecting sound; 0.5mm error will make it UNUSABLE and anything but an original o0r specific copy won´t guarantee that, even less a generic replacement you may find.

Much less risky replacing full tweeter with a similar one.

Of course, best is an old second handone.

Power handling will certainly same as before or better, simply because of advances in adhesives.

Absolute worst case, replace both tweeters, for symmetry, imaging, etc. and keep the surviving one as a backup.

 

[diyiggy]

🙂 I note the serious GUARANTEED (ahaha, I'm not an Ebay guy too much as well)


Thanks you JMFahey, I believe as Lojzek pointed out : my Indiana Jones journey is beginning to find an unit!