LS35a Experts

[bcherry]

I have a pair of Rogers 15ohm LS35a with haven't been played for many years. Yesterday I hooked them up in my home system and 1 voicecoil is rubbing. Turned them upside down and they were OK for a while then started rubbing again so the surrounds and spider have deteriorated. I also have in hand a pair of new original KEF110 drivers but I've been told they are not a drop in replacement as Rogers would dope the 110's to tune them for use in the LS35a.
Does anyone know if that is true? Has anyone everyone just replaced the original drivers with standard KEF110?
thanks
Brian

[Inductor]

The original KEF110 (reference?) should be a 15ohm for the LS35a you mention.
I'm not Kef/pro but look here for various models: museum worthy KEF speakers?

[planet10]

Originally Posted by Inductor

The original KEF110 (reference?) should be a 15ohm for the LS35a you mention.

Nope. It was the standard 8 ohm B110 SP1003.

Part of the disrepency is that the 15 ohm LS3/5A isn't really 15 ohms, and the rest is the XO.

They ar ematched, but i've never seen extra doping on them.

dave

[Charles Darwin]

The LS3/5 was a BBC design.
To be allowed to use the LS3/5 designation none of the manufacturers (Rogers, Spendor,Harbeth et al) were allowed to deviate from the BBC spec at all.
Hence it would have been illegal for Rogers to use extra doping.

[Inductor]

Originally Posted by bcherry

I have a pair of Rogers 15ohm LS35a...

Brian, I must admit that, if your reference is incorrect, you might need a KEF type B110 unit (SP1003) with nominal impedance of 8 Ohms (Rdc=7,1 Ohm), Fs: 35Hz with limits being 33 and 40Hz. Your reference for this speaker, is then (should be), a nominal impedance value of (modulus) 12 ohms. (as in "The design of the miniature monitoring loudspeaker type LS3/5A", 1976).

[bcherry]

Originally Posted by Inductor

Brian, I must admit that, if your reference is incorrect....

This is what I have. There is so much info on the LS35a, not always in agreement so finding it difficult to know what to do with these. Some say it is a common problem, caused by magnetic speaker stand, the amplifier mismatched etc. Thanks for the comments so far. I'll need to check if the B110 I have are the ones mentioned above.

Does the attached pic of the nameplate on the back help?

[planet10]

Brian,

Same label as on the pair i am restoring.

dave

[ultrakaz]

dave and bcherry,

Any general comments on the sound of the LS35a version you have versus "modern" speakers, while they were working?

And dave, how does it compare to your single driver "onken" style FE127E speakers

I haven't heard a pair for many years, but the pair I heard sounded subdued and undynamic (dead). Probably, the components dried up, so I did not know what the attraction was all about.

[bcherry]

Originally Posted by ultrakaz

dave and bcherry,
Any general comments on the sound of the LS35a version you have versus "modern" speakers, while they were working?

Immediately reminds of the 'voice of the BBC' and 6 o'clock news sounds from when I was growing up on the BC coast. Sound is always pleasant and imaging is very good. For a small speaker it does a particularly good job of hiding the fact that there is no real bass.
It also has the attributes of a sealed box design -- meaty transient attack and smooth response.

However having been so long away to open baffles, compression horns and ribbons, and field coils etc, it does sound subdued. There is just too much missing for even a second system for me. My wife likes the LS35a but when I replaced them with a corian cabinet speaker of not much bigger size and with a ribbon tweeter, she went "wow," especially on some massed African vocals.

Brian

[tomtt]

Originally Posted by planet10

and the rest is the XO.

dave

and what an xo it is -








from here
Rogers Speakers - BBC LS5/9