Have Babied these formula 4's for 36 yrs. Sent for a few replacement biconex horns on ebay. One straight from a later model formula 4 and 2 from a formula 6. Tested these and checked them out against my originals. Bought mine in 1978 a B Series production number. The phenolic diaphragms visually very different. Mine were a very opaque orange color. The later models are more of a darker copper color. You can clearly see the strands embedded in both. My originals still sounded good, but heavy movie soundtracks were giving them a run for their money. I still had the crisp treble, but not much body through the upper mids. The replacements have LOADS of upper mid. I had to roll the L-pad back...(lessens the upper mids in the horn..doesn't touch the super-tweeter).. Another interesting find....I played my mp3 player into a driver with the horn sitting upwards, but not screwed on. I slowly rotated the horn about 30 deg. and the tone completely changed to the brighter side. It's interesting...when you look at the backs of these drivers there are alternate punch spots to drill alternate holes and mount the horn in that angle. Makes me wonder if they didn't flip the position when they wanted the driver to act more as a tweeter or more as a mid....:scratch2:
And let me clear up one last thing....I'm reading all kinds of info that the super-tweeter is barely audible.... Run Thor in DTS HD Master at 68 - 70 db...I assure you it's providing all the sizzle it's supposed to crossing over at 17k....what the hell...??? It was never meant to behave the way tweeters normally behave in other speakers...lol....so leave it alone already....
If you are a BIC Venturi fan....try to buy a set of horns from a formula 6...with one of them not being replaced. Or wait diligently for 2 formula 1,2,3,4's whatever...listen to them with different horns and try to find 2 that sound as similar as you can. So all in all there are different diaphragms in earlier and later biconex horn drivers, and there is no guarantee that they will always sound the same. Amen.:thmbsp:
And let me clear up one last thing....I'm reading all kinds of info that the super-tweeter is barely audible.... Run Thor in DTS HD Master at 68 - 70 db...I assure you it's providing all the sizzle it's supposed to crossing over at 17k....what the hell...??? It was never meant to behave the way tweeters normally behave in other speakers...lol....so leave it alone already....
If you are a BIC Venturi fan....try to buy a set of horns from a formula 6...with one of them not being replaced. Or wait diligently for 2 formula 1,2,3,4's whatever...listen to them with different horns and try to find 2 that sound as similar as you can. So all in all there are different diaphragms in earlier and later biconex horn drivers, and there is no guarantee that they will always sound the same. Amen.:thmbsp: