I'm still just learning about crossovers, but I have a few thoughts on this. Maybe someone who knows more will chime in. Here's my crude understanding:
First, you should note that the 052Ti isn't
necessarily capable of playing lower frequencies, even though in that particular speaker (the 4408), the crossover point (2,500 Hz) is lower than the 3,000 Hz point of the L46. All that means is, the designers of the 4408 decided to use a lower crossover point. They designed the crossover to start handing off the lower frequencies to the woofer at point X instead of point Y. That choice may have had more to do with the woofer's capabilities than the tweeter's.
In order to know which tweeter can actually play lower, you'd need to compare the specs for the individual tweeters, rather than just reviewing the crossover points for those two speakers. It is entirely possible that the 034 tweeter would be able to play those lower frequencies, too, and I bet it can.
The DC resistance figure (resistance with direct current) is a rough indicator of how the tweeters will behave in terms of impedance while playing alternating current at various frequencies. The AC impedance will vary with the frequency the tweeter sees, resulting in a curve. As I understand it, you would really need to compare the impedance curves and sensitivities of the two tweeters to predict how similarly they will behave, then run real-world testing in a given speaker with a given crossover to see how they act.
With those technicalities aside, the fact is that JBL has recommended the 052Ti as a drop-in replacement for the 034 (or at least that's what my link seems to say). If so, then I bet it's a decent match. The sensitivity and output levels may be slightly different. The impedance and frequency response curves may be a bit different too, but mainly I suspect the 052Ti will play flatter and to a higher frequency than the 034.
In sum, I bet it's an improvement. I think you will see better high-frequency extension, less distortion, better dispersion, flatter frequency response and impedance curves, and more power handling. Why? Because the 052Ti is the result of more design experience and revisions and more modern technology than the 034, and is generally considered to be a better driver.
I suspect the output level will be about the same. If not, you may need to muck slightly with the output using a different resistor in the crossover. The current resistor (see the
link above) is called R1, and it's 5.1 ohms. You could lower that resistance slightly for more output, or raise it slightly for less. That would be quite a simple job.
But again, I offer these thoughts based only on my fairly basic understanding of these things.
