In Thailand it's hard to find good drivers at reasonable price -the scan distributor has the 4 ohm 18W revelators at a bearable cost - looking at tweeters that can cross low, not much choice .. either the well reviewed RS28F or larger format Wavecor's.
Question is, will these fairly cheap tweets do the revelator's justice?
Question is, will these fairly cheap tweets do the revelator's justice?
It's not the tweeters, it's the designer that's the weakest link. In fact it's hard to find a tweeter that would be so bad that you couldn't make good use out of it. No reputable manufacturer can afford to produce really rubbish units. If you care to look at Vifa XT 25 range of tweeters, you will realize sooner or later that these are fairly close specwise to expensive SS ring radiators, without the fancy aluminum appearance. I think Zaph has said that too.
If I remember, Zaph tested the "normal" XT25. The larger, dual magnet variant, the XT25BG has a lower resonance and therefore lower crossover point. You can get the Vifa/Peerless XT25BG fairly cheaply too. 
It is a remarkably good tweeter. I own them AND the SS 18W and they would be ideal together.
I haven't put those two together, they are in different speakers. The SS 18W is with an AMT, and the XT25 is with a Peeerless mid-woofer, but listening to them side by side, I am telling you, the XT25, especially the BG, is amazing if you don't mind a slightly narrow dispersion profile.
It is a remarkably good tweeter. I own them AND the SS 18W and they would be ideal together. I haven't put those two together, they are in different speakers.
The SS 18W is with an AMT, and the XT25 is with a Peeerless mid-woofer, but listening to them side by side, I am telling you, the XT25, especially the BG, is amazing if you don't mind a slightly narrow dispersion profile.
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Another option if the SB Acoustics drivers are reasonably priced in Thailand: the SB29RDCN is a small format tweeter than can be crossed pretty low. Zaph had a contest and posted winners for LR2 @ 2KHz, LR4 @ 1.6 KHz and LR6 @ 1.1 KHz! Here's the link: Zaph|Audio - Design Contest Results. Crossover schematics are posted.
Troels was very impressed with the distortion of SB tweeters, particularly the SB26ADC: SBAcoustics-tweeters
I don't know if the SB26ADC is in the same league for non-linear distortion as the SB29RDC, RS28F and Usher 9950-20 (same driver as RS28F but without the mesh grille I believe). Troels measurements only have a noise floor of about -40dB and only the 2nd and 3rd harmonics. What is happening at the higher harmonics (5th order) is of interest as this will be far more objectionable imo. Zaph tested the SB26STAC which i believe is the same driver with a different dome material. From his tests the SB26 has the SB29 beat for 2nd harmonic, but the SB29 is the winner everywhere else.
http://www.zaphaudio.com/temp/SB-Acoustics-SB26STAC-C000-4-HD-sample2.gif
http://www.zaphaudio.com/tweetermishmash/SBAcoustics_SB29RDC-HD.gif
http://www.zaphaudio.com/tweetermishmash/Dayton_RS28A4-HD.gif
I would be weary that you'd want to cross the SB26ADC lower than about 2.5K LR4 if you are trying to build to world-class distortion standards. Then again it could be that Zaphs samples were both defective as there is some funny business going on around 2K in his measurements and he shows that at least one of his samples had a rub/buzz issue.
SB29RDC will do 1.5K LR4 with ease. The 2nd harmonic will go way down with the attenuation from the crossover and you are left with very nice non-linear performance. You can see this from Zaphs contest results (http://www.zaphaudio.com/contest.html) albeit with the smaller neo version of the SB29.
RS28/9950 will do around 1.8K LR4 in my opinion. The RS28/9950 has flatter frequency response than the SB29 but the SB29 edges it out in non-linear distortion. Your call.
http://www.zaphaudio.com/temp/SB-Acoustics-SB26STAC-C000-4-HD-sample2.gif
http://www.zaphaudio.com/tweetermishmash/SBAcoustics_SB29RDC-HD.gif
http://www.zaphaudio.com/tweetermishmash/Dayton_RS28A4-HD.gif
I would be weary that you'd want to cross the SB26ADC lower than about 2.5K LR4 if you are trying to build to world-class distortion standards. Then again it could be that Zaphs samples were both defective as there is some funny business going on around 2K in his measurements and he shows that at least one of his samples had a rub/buzz issue.
SB29RDC will do 1.5K LR4 with ease. The 2nd harmonic will go way down with the attenuation from the crossover and you are left with very nice non-linear performance. You can see this from Zaphs contest results (http://www.zaphaudio.com/contest.html) albeit with the smaller neo version of the SB29.
RS28/9950 will do around 1.8K LR4 in my opinion. The RS28/9950 has flatter frequency response than the SB29 but the SB29 edges it out in non-linear distortion. Your call.
On the samples of the XT25TG30 and XT25SC90 I've got the 2nd harmonic is perhaps about 5dB lower than in Zaphs measurements. I would be happy to cross the full size XT25s at 1.5K LR4 and the neo version around 2K. I've crossed the neo version as low as 1.6K LR4 and the 2nd harmonic from the tweeter was only becoming an obvious hump in the system distortion north of 100dB @ 1meter so it depends how loud you need them to go.
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RS28 will match Revelators in technical terms reasonably. Sonically? I suspect so, they're good units, although I prefer the aluminium dome version myself.
With that said, if necessary, I'd hang fire a month or so, save a bit of extra cash & buy a pair of Satori TW29Rs, which are probably the best soft-dome (well, hybrid dome) tweeters I've ever heard; I'd take them over the Scan 7100 or Seas Crescendo (both of which I rate) despite only costing about half as much.
With that said, if necessary, I'd hang fire a month or so, save a bit of extra cash & buy a pair of Satori TW29Rs, which are probably the best soft-dome (well, hybrid dome) tweeters I've ever heard; I'd take them over the Scan 7100 or Seas Crescendo (both of which I rate) despite only costing about half as much.
I recently used the rs28f in a 2way with the Eclipse w6520r from Meniscus. Xover point came in at an incredible 1.5k 2nd order electrical. Distortion measurements were far below audible and there is no hint of strain. The build received quite a few positive reviews when i displayed them at the recent InDIYana annual event. Meniscus will actually be making them available in kit form soon.
The SB Acoustics SB26stac is also a stellar performer. I also used it with the w6520r crossed at 1.8k in series network. Again, distortion is very low and that tweeter can take a beating! We accidentally threw full power from a crown xls2000 into it. Enough to see the tweeters excursion! They are still here playing along with no damage.
The SB Acoustics SB26stac is also a stellar performer. I also used it with the w6520r crossed at 1.8k in series network. Again, distortion is very low and that tweeter can take a beating! We accidentally threw full power from a crown xls2000 into it. Enough to see the tweeters excursion! They are still here playing along with no damage.
I've used the RS28F and the Vifa XT25 ring radiator tweeter in variants of my 'Intimates' speakers. Visit Parts Express Tech Talk forum and do a search on 'Intimates' and you will see the whole story that started with SS domes, then the Vifa25 and finally the Mundorf AMT.
I have used the RS28F in other designs and as another has posted, it is an easy tweeter to work with.
I have used the RS28F in other designs and as another has posted, it is an easy tweeter to work with.
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