Replacing speakers in Lat-1's

There are a few manufacturers that allow upgrades in consumer audio - although it is not al that common in speakers. Merlin speakers comes to mind. ATC also, if you bought an ATC 100 in the early 90's, it would have an older design woofer and an older type tweeter - it would also have a first generation amplifier pack. ATC sells kits to upgrade front baffle to fit a newer tweeter, while the woofer is a simple replacement (with the old one sent back for refurb) and the amp pack is also a replacement pack that just pops in. They also sell recone kits because the drivers are simply too expensive to toss in the garbage if they get blown up from abuse. The reason they can do this is that ATC make almost all the parts in house (just outsource the cabinet work) and they haven't substantially changed the major aspects of the design so improvements can be retrofitted in much the same way you still see Boeing 737 aircraft flying around after all these years (after all acoustic and aeronautical physics doesn't change all that fast so the designs progress but do not change that often.). The only way this works is if you have a design that continues to sell after many years. It also means your target market are customers who tend to keep gear longer and expect it to be reliable and easy to maintain.

What is your system by the way????

Nothing fancy, but I like it. I've got a pair of Spendor SP1/2Es driven by an Image 65i tube amp. Source is a Squeezebox through a Lavry DA-10 DAC.

Spendor makes their own mid/bass units in house and use a fairly high crossover point to the tweeter. There would be no practical substitute for the mid-woofer and they are already using Scanspeak for the tweeters. Use any other drivers in that speaker and you've completely defeated the purpose of buying a Spendor. You're in the same boat with any high quality design.

Since you have a Krell system I doubt you can improve your speakers other than changing them for LAT1000 ...
However DIY people with some knowledge of loudspeaker design and the help of of a measurement system can modify these speakers to sweet other amplification systems (eg. tube amplifiers) and their taste.
Can you imagine a tri-amplified LAT1 without passive crossover using an active crossover?

There sounding better. OOOps there brand new. Need to be broken in along with the new tweeters.

the answer is- Yes you can improove.and a lot. but-
1)I would strongly recomend not to change xover unless you want to fine tune speakers a litle. you can change tweeter to 70000 series ring radiator you will get better dynamic ,more imediacy insound(just measure/calculate krell xover voltage divider or serial resistor to ensure the same eficienty with THE SAME voltage divider values)

bass drivers also can be changed to better ones (22W) bass will be fuller and more punchy not hard sounding .

what you can not change its midrange.yoiu can but its likely 99% that it will sound worse. even the same drivers with 1mm shorter coil will have diferent response and will kill krells enginiers sound conseption.

as for my self I am using aluminium enclosures also and they deserves very best drivers, better thant theese in krell Lat1 IMHO