Vifa Tweeter difference

squamishdroc

Just wondering what is the difference between the Vifa XT25TG30 and the XT25BG60? They are pretty much the same price at Solen - looking to pair with some Rival woofers I bought.

dcibel

The BG60 has a double stacked magnet, and higher sensitivity as a result. I don't know for sure, but based on the impedance and Qms values, the BG60 might also have ferro fluid, where the TG30 might not.

JasonP

The official datasheet for the double magnet BG60 does not list any FF, but I can see how it looks like it has it.

Wolf

To my knowledge, the XT tweeters do not use FF. The BG60 has a double magnet assembly and is therefore a lower Q tweeter, and ipso-facto, the Fs will be lower in frequency as well as likely lower in magnitude. This is why the BG has a lower Zmax value over the TG.

More info:

There are some closeout OEM models like the Neo version, the different faces, and as such some are with FF. The standard range of OT19, XT19, XT25-TG30, BG60, BG50, SC50, SC90, et al to the nth degree... all have contained no FF.

PWRRYD

Would there be any advantages and/or disadvantages if someone added ferro fluid to a tweeter that never came with FF?  Is the gap geometry designed differently/specifically for a tweeter with FF?  I remember Pete S. one time claiming a tweeter with FF has less "detail" but I know there have been some very good tweeters that used it (i.e. Dynaudio D28/2).  Sorry if this is a thread derail Jason.

Wolf

I do know that Usher stopped using it in their tweeters because the HD was higher and they did not like it. There was a huge debacle around the first run of Gen1 RS28A tweeters because they had FF, and none after that did. PE even carried FF for the reason of adding it to rematch initial specs. AFAIK, they still do for adding to whatever tweeter.

Other than motor geometry, FF will increase HD from tweeter to tweeter by comparison. It will also damp the Fs, and allow a better heat dissipation from coil to motor. That said- it can also go bad and need removed and replaced.

A caveat though- you don't want to over do it if you add it. Add a drop at a time and allow them to spread through the gap evenly before adding the next. When gap is filled is just enough. Too much FF is a bad thing. Measurements can be your friend here.

I've never done it myself as I'd be afraid of screwing up a good tweeter. However, these are the steps to take if you want to add it to a tweeter.

There are also spider-less full-range widebanders that actually use FF as the rear suspension, as it will keep the VC former centered and not allow abrasion from the pole if used both inside and outside the former in the gap. I assume this is true in the tweeters as well, so a better physical alignment is indeed possible with its use being that domes have no rear suspensions.

Nicholas_23

How viscous FF ?

Wolf

Honestly, I don't know.

JasonP

I suppose I feel that the effect of FF is implementation dependent. Some of the best tweeters I've heard have had it, and suffer not for it (but I can't do a side-by-side comparison without it) the SEAS 27TBFC/G comes to mind as an outstanding tweeter with FF.