Ejvic,
This can be reverse engineered and a decent dome can definitely be found. I would need to see the crossover. I've done some looking for you... this is a guessing game.
Hales are 88db 4 ohm speakers, I cannot find a spec sheet on its original tweeter anywhere, one forum said that it had a very low fs... (around 500). Most domes of that era had a slight to relative high end rise...
So here you go, basically, if the crossover does not have any pad on the tweeter, meaning the original tweeter was 88 db 4 ohm, Parts Express has The Dayton RS28F-4 (silk dome mid 500's FS) slightest high end rise, should be a drop in.. don't know about fitting in the cabinet. This is built for Dayton by Usher and is one of the better Dayton tweeters....
If you can take a look at the crossover and get resistor values on a pad, if there even are any, we can get very close, but my guess is that a Vifa of this era should not be more than 91 to 92 sensitivity... Madisound has a SB Acoustics SB25AC-C000-4. This dome has similar characteristics, but is 91+ sensitivity 4 ohm, but has a 700FS. I have not found crossover points or slopes.
These are both budget domes at around $50 each, Let me know where the budget is and I can take another look, but seeing that the vifa that you dropped in there is around 87.5 sensitivity with a higher fs and is 6 ohms, I would think that the Dayton would be a very good alternative.
I hope this helps, Tim
