LS 3/5 8 ohms speaker replacement

[CeruttiA]

I have a pair of 1990 s manufactured LS 3/5 ( 11 ohms) and am being offered 2 x 8 Ohms kef speakers ( sp 1063) to keep as a replacement .Would that work or would i need 11 Ohms replacements ?

Sorry - as always a GCSE electronics question !

[Hugh Robjohns]

The Internet is absolutely crammed full of information about the LS3/5A and every variation of drive unit and crossover.

The later 11 ohm version of the LS3/5A used Kef's revised B110 bass-mid driver known as the SP1228 which has a nominal 6 Ohms impedance.

The earlier 15 Ohm version of the LS3/5A used the 8 Ohm B110 SP1003, I believe.

So those 8 Ohm models aren't correct for your speakers. Moreover, they aren't strictly correct for the 15 Ohm models, either.

The B110 SP1063 was a less stringently specified version of the driver which was used in Kef Caprice and Corelli hifi speakers.... if my Google search mojo is working!

[James Perrett]

The specification of the version of the B110 used in the LS3/5a is very tightly controlled and any other version will not perform to the right specification. They won't necessarily sound bad - after all, Linn and Jim Rogers used less tightly specified drivers in the Kan and the JR149 - but they won't be LS3/5a's any longer.

Paul Whatton's website that I mentioned in your previous thread has all the information you need.

[Arpangel]

The B110 driver was essential to the sound of this speaker, change that, and you’ll loose that sound.
I’ve changed drivers on a number of classic speakers over the years, and they’ve never sounded the same again, re-coning, near substitutes, they never work.
It’s always best to have "one I prepared earlier" in the cupboard, buy non working ones that you can cannibalise.

[Hugh Robjohns]

The point is that there are lots of different 'B110' drivers, and the two different BBC LS3/5As were each designed with very specific variants in mind. Use anything else and, while it might sound fine to the causal listener, it won't meet the intended production specifications... which is kind of the whole point of the LS3/5A's status as a reference monitor!