Quick and dirty first impression of the 4343:
The presentation is different from the Tekton Double Impact.
The DI is more laidback whereas the JBL 4343 sounds more direct and immediate, imparting to it a sense of greater presence than the Tekton.
Result: more immediacy, more presence, more palpability.
To break it down, the quality and quantity of bass from the 15 inch driver of the JBL is several notches (or at least an order of magnitude) above the Tekton's. And that's saying something because before tonight the bass from the Tekton Double Impact was the best I've ever heard.
The mids and highs too have a different presentation from the Tekton's mids and highs. The tonal quality and the texture of voices and instruments of the JBL seemed more real to my ears (yes, tone is a very subjective thing to speak about, but suffice to say that it really sounded really good to my ears).
The highs are way more pronounced on the JBL than the Tekton. Overall, the presentation of the JBL is brighter. The upside of this is the JBL is way more resolving than the Tekton. Both Prem and myself heard several completely new details on tracks we've used as test tracks for a long time now. The downside is several LPs we've used as test records now show up their weaknesses. The speakers are rather ruthless in exposing the weak links in the chain. For example, the 16 gauge speaker cable didn't make the cut with this speakers. It took the 12 gauge to make it sing.
The attack of the JBL on leading edges is instantaneous without being hard edged. It gives it tremendous sense of immediacy. In that sense, it is much closer to the Rethm Sadhaana than the Tekton was to the Sadhaana.
The Tekton Double Impact Special Edition speaker is an amazing modern speaker packed to the gills with clever innovations at real-world prices, but the JBL 4343 which was designed and manufactured about four decades ago made it sound almost broken. It's hard to say if much progress has been made in speaker technology. It's yet another blind buy by Prem that has turned out to be a winner. Kudos and respect to you, Prem.