Buying tips: LS3/5A

Buying tips: LS3/5A

Postby mozilla » Fri Jan 13, 2006 5:12 pm

Some people have emailed me offline especially about the differences between the 15-ohm and 11-ohm versions.

I am starting this thread with a visual guide to identifying the 15ohm and 11ohm versions. Please chime in with your other tips and experiences so we can compile a knowlegebase on this topic.

First off, there are the 15ohm and 11ohm versions. These are not the ratings of the main B110 driver but a combination of the T27 tweeter, xover and B110.

There are so-called Rogers pseudo-15ohmers. These have been documented to start at serial no. 321xxx. Earlier serial numbers by Rogers are REAL 15ohmers. Those after this cutoff are actually 11 ohm units but mislabelled as 15ohms. The common belief is that Rogers had excess 15ohm labels and just pasted them on the new production (at the time) 11 ohmers.

Aside from the serial number, how would one identify a 15ohm unit vs an 11ohm unit? I compiled the image below to show the differences:

Image

I'll add other photos, especially of the xovers later on. Feel free to contribute.
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Postby KD » Fri Jan 13, 2006 5:32 pm

White belly = 15 ohms, right? The pics both say 11 ohms. :(
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Postby BlackRock » Fri Jan 13, 2006 5:57 pm

Hi Mozilla,
Thanks for posting! It will really help alot for people like me who are newbies with the Ls3/5a! :)
Will there really be a big difference in sound between the 15ohm and 11ohm Ls3/5a?
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Postby mozilla » Mon Jan 16, 2006 12:20 pm

KD wrote:White belly = 15 ohms, right? The pics both say 11 ohms. :(


Sorry for the typo. 15ohms has been corrected. The 15o is CIA's and the 11o is mine.

Pls refresh your browsers.
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Postby mozilla » Mon Jan 16, 2006 12:24 pm

Here is what a 15ohm xover looks like with the auto transformers. It ishows crossover model FL6/23 manufactured by Chartwell. All 15ohm LS3/5A's up to 1987 used this crossover.
Image

After this date, licensed manufacturers designed their own pcb layouts tho the xover circuit remained the same. So just by looking at your xover you will be able to roughly tell whether it is before or after 1987.

Paul Whatton has documented that KEF manufactured the 11ohm xovers ,FL6/38, after 1987. Paul says that "this was because when a speaker fell out side specification there had been disagreements between KEF and the licensees each blaming the other for the problems! With KEF supplying both drive units and crossover this source of conflict was resolved. "

All 15ohm LS3/5A's pre-1987 were using KEF B110A/SP1003 and KEF T27/SP1032 driver types with the FL6/23 crossover shown above.

Later LS3/5a drivers were the B110C/SP1228 and KEF T27/SP1032 with the later crossover FL6/38/SP2195 which uses no auto transformer.

SP2195 Crossover - Here is the 11ohm xover w/o the auto transformers:
Image
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Postby mozilla » Mon Jan 16, 2006 1:25 pm

More 15ohm xovers. Despite the difference in layout from the FL6/23 of Chartwell, all have the auto transformers

CIA's Rogers 15ohm xover:
Image

KD's Spendor 15ohm xover:
Image
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Postby ichabod » Mon Jan 16, 2006 1:40 pm

soundwise, you can search the past post for some of the "heard of" differences. Gordon Holt had a series in Stereophile through the years on the LS, from its beginnings (the 15 ohm) through the 11 ohmers with some other gents like Atkinson reviewing the same speakers. This is a "must read" article(s) if you really wanna invest your money on the LS and have the opportunity to buy a 15 ohm version (cia must sell his?) which will more often cost more. The first shoot-out by KK will also be a good read for those who can't avoid being picky about which LS would sound better as BR had asked.

If I recall, it was Paul Whatton who suggested that cabinet workmanship (lacqured ones and those exotic wood finish used) seem to play a bit of role to the sound of the LS. The heavier cabs (akin to the BBC originals with screwed in backs) seem to make them sound "better." How much better? Check on the standing (ratings) of each brand name from that KK shootout.

The LS forum as well had a discussion about the 15 x'over, notably favoring the earlier its design now I believe being used by Cicable X'overs for the LS (x'over) upgrade by Derek Hughes, former owner Spendor, who is second largest manufacturer to Rogers of the LS 3/5A.

HK tubeheads seem to favor the 15 ohm version due to its easier load with set amps. But I think one should be careful enough to take all things (pertaining to the LS sound), what underlying differences may come to play with different amplifications taken in. Example: set amps vs. pp. Type of music one plays through the LS. Remember the KK shootout results gave the 11 ohm Harbeth the highest rating with the Chartwell 15 ohmer (2nd place) I believe with a slightly far score, to be followed by the lacquered Rogers, 3rd, and the 4th placer spendor 15 ohms by a .5 score difference. KK considered them both as 3rd placers respectively. Overall, the 11 ohmers had more wins.
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