advertisement


Getting to know LS3/5As

So you had the X/O totally rebuilt?

Yes, this pair of JR149s are beautifully cosmetically, but were sadly way off spec, I think they’d been stored somewhere slightly damp. It was a very long journey getting them the way I wanted them. The crossovers were very interesting in that a couple of resistors didn’t match left/right, so I assume a construction error back when they were made (the serials match, so they are a pair, I’ve even got the box, or most of it anyway). I used Falcon’s matched Alcaps and Kiwame carbon comp resistors.

The JR149s look excellent, esp with those grilles. What’s the theory on why they are so much better value than LS3/5a and go for much less second hand?

I guess the lack of the BBC connection, plus they are very, very hard to find in nice condition. I think the cylindrical construction did them no favours as most look like they’ve rolled around and picked up all manner of chips and scratches. I’m very obsessive about condition and I ended up monitoring eBay listings for 5 or 6 years before seeing a pair I liked the look of! One would think the rarity of genuinely tidy pair, let alone anything even approaching mint & boxed has kept the real collectors away. I have a feeling far fewer people have even heard of them, let alone heard them, so again off the radar to a large degree. I have a real soft spot for them as they were the first hi-fi speaker I ever owned back in 1978 (an aunty died and left me a few £hundred in a will so I had enough to buy a nice second hand system aged 15, the rest being a GL75 and 33/FM3/303).
 
My pair of 149’s were in superb condition as the original owner had them on an L shaped wall bracket upside down. The cabinet was held by the silver screw that holds the base on as he had extended the centre rod.
The wood grain finish looked really awful though, almost like there were two different pieces of wood joined together. I had an opportunity to get them painted black and they look great. Not used them for years though!
 
JR149 finish was very hit & miss, I think they were built down to a price or maybe a bit ‘made in a garden shed’ (as was so much of what came in the next decade!). I don’t think the veneers were ever book-matched or paired, you just got two of the specified finish. My first ‘red logo’ pair back in the ‘70s were lovely as I recall, either walnut or mahogany, something quite dark with a bit of a sunburst to a black edge. My current pair are teak and in very nice condition, close enough, but certainly not from consecutive pieces the way the LS3/5As or Spendors are. I’ve seen examples where people have replaced the JR149 top and bottom caps with beautiful oiled solid wood and they can really look superb, better than any originals as the grain matches top and edge rather than the rather naff strip of veneer. Definitely a great route to restore a tatty pair.

PS I like teak. No where near enough of it in this century IMO. I guess a CITES environmental thing. I’ve got a wonderful ‘60s or ‘70s teak standard lamp! Proper ‘Danish mid-century modern’. It would look great next to the JR149s...
 
@Tony L How did the speakers do with The Fall's 'Frenz experiment'?

That’s an old photo, it sold ages ago (this is upstairs in the Record Shop). I’m CD/SACD only in this system. I have tried a good bit of indie/alt type stuff, e.g. both the LS3/5As and JR149 sound superb with the recent The Ascension album by Sufjan Stevens visible in the first pic on the thread. That’s got a substantial electronica aspect to it, very full range, so not an easy job for a little 11cm woofer!
 
Well, when I bought my Chartwell's in 1978 I could not for my life guess that 42 years on people would still be obsesive about them!!!!
 
JR149 finish was very hit & miss, I think they were built down to a price or maybe a bit ‘made in a garden shed’ (as was so much of what came in the next decade!). I don’t think the veneers were ever book-matched or paired, you just got two of the specified finish. My first ‘red logo’ pair back in the ‘70s were lovely as I recall, either walnut or mahogany, something quite dark with a bit of a sunburst to a black edge. My current pair are teak and in very nice condition, close enough, but certainly not from consecutive pieces the way the LS3/5As or Spendors are. I’ve seen examples where people have replaced the JR149 top and bottom caps with beautiful oiled solid wood and they can really look superb, better than any originals as the grain matches top and edge rather than the rather naff strip of veneer. Definitely a great route to restore a tatty pair.

PS I like teak. No where near enough of it in this century IMO. I guess a CITES environmental thing. I’ve got a wonderful ‘60s or ‘70s teak standard lamp! Proper ‘Danish mid-century modern’. It would look great next to the JR149s...

I must admit to being a walnut fan. Atc, Linn and Rega being some stand out veneers I’ve seen. I did visit someone with silver JR149’s once and was surprised to find the top cap aluminium!
 
I don't see any evidence of the design or construction changing, but I wouldn't doubt that they've become better at making B110s that consistently meet LS3/5A spec.

One thing I’d love to establish is what exactly is ‘LS3/5A spec’ when it comes to B110s? I assume Falcon are producing at that side of the bell-curve.

Malcom Jones’ background is in electronics and adhesives. When Falcon decided to reintroduce the LS3/5a Jerry and Malcom went to the trouble of tracking down the recipe of the adhesive used for the original B110 as used by the BBC when developing the LS3/5a. Apparently adhesive types significantly alter the response of the B110, and the adhesive recipe or type was possibly changed by KEF over the course of its production.

It’s interesting to note that the five .5db taps for the HF crossover network were introduced by the BBC designers to accommodate variations in drive unit spec to ensure integration, so consistency was obviously an issue from the get go.

I think this attention to detail by Falcon is one of the many reasons why the Falcon LS3/5a is special.
 
I must admit to being a walnut fan. Atc, Linn and Rega being some stand out veneers I’ve seen. I did visit someone with silver JR149’s once and was surprised to find the top cap aluminium!
Do you know if it was solid aluminium or just an aluminium lid over chipboard?
 
One thing I’d love to establish is what exactly is ‘LS3/5A spec’ when it comes to B110s?

According to the German article given to me by CPG of this manor, the BBC versions were selected examples where the (1 to 1.5kHz) resonance was as tame as possible (via Google translate).
 
According to the German article given to me by CPG of this manor, the BBC versions were selected examples where the (1 to 1.5kHz) resonance was as tame as possible (via Google translate).

Interesting, that makes sense. Here are the supplied response plots for the pair of Falcon B110s in my JR149s:

47580455331_4ee6b00738_b.jpg


I’ve no idea how these match to the generic Kef spec. My gut feeling is that they have done a remarkably good job recreating these drivers, my only slight doubt is I think there might be an bit of a treble spike right at the very top of their T27 range (about 16kHz IIRC) that shows on the Stereophile LS3/5A measurements and also on my own of my JR149s and doesn’t seem to exist on Kef equipped versions. I will eventually get around to measuring these LS3/5As and will be curious to see how similar they are to my JR149s. This treble aspect is sadly none of my concern as my ears are gone by then (I’m good to 12kHz or so)! The Falcon T27s didn’t come with a dedicated plot though are sold as matched pairs. Subjectively they seem very good indeed.
 
Do you know if it was solid aluminium or just an aluminium lid over chipboard?

Best way to describe it was like a slightly thicker round biscuit tin lid. It looked like the foam grill could be taller and push underneath the top edge. The grills were long gone so not sure how they would gave sat.
I remember checking out my pair when I got home and they actually didn’t look or feel as high a quality as my wood ones for some reason.
 
My stepdad used a pair of LS3/5as in his car in the late 70s/early 80s! I'd forgotten about this until he mentioned it last time I spoke to him. I've no idea what happened to them after that.
 
My stepdad used a pair of LS3/5as in his car in the late 70s/early 80s! I'd forgotten about this until he mentioned it last time I spoke to him. I've no idea what happened to them after that.

I once heard a story that Linn Kans were originally developed as one offs for in car use by someone at Linn. I’ve no idea if that’s true.
 
I once heard a story that Linn Kans were originally developed as one offs for in car use by someone at Linn. I’ve no idea if that’s true.

Not recomended. B110's Bextrenes cones (same material as plastic model kits) doesn't stand heat well. Rear parcel shelf = oven when the sun is shining.
 
Certainly correct with the BBC or ITV but Kef decided to be different with their Raymond Cooke examples. They used MDF for cabinets instead of Baltic Birch Ply and they did sound a little different. I never came across any in studios though.

I have heard the same for late Spendor versions which started to use MDF. There is a video of an LS3/5a club meet-up where Andy Whittle makes this point.

Funnily enough I was having a PM chat with Tony last week and mentioned that my time with a pair of 11 Ohm Spendors in the 90s was not at all good - musically deadpan with ill-defined, bloated bass.

That is interesting, I didn’t realise that. No ply cab = not an LS3/5A IMHO. The BBC cabinet research was totally obsessive and even specified beach battens etc. It is a very, very rigid specification, deviate from it at all and what’s left may be a very nice little speaker, but it isn’t an LS3/5A. Here is the BBC LS3/5A white paper in .pdf form, it is a fascinating read.

I bet the MDF versions still 'measured' within spec though, even if they sounded slightly different - which highlights the danger of the arguments posed by some of our friends on the Klipsch thread :)
 
Then again, I'm not convinced the LS3/5a cabinet classifies as 'thin-wall'.
The research into the benefits (and problems) of thin-wall cabinets was very much aligned to the much larger BBC designs using larger panels.
In that context it makes sense since you have large panels with a relatively low resonant frequency, further mass damped to pull that resonance out of the midband.
The 3/5a is quite different - it's tiny, with small cabinet wall dimensions. What's more it is extensively braced by the beach batons and inset front and rear baffle. In this context, 9mm or 12mm birch ply is a thick-wall cabinet!

The requirement for its use was likely a hangover from earlier research. I don't think MDF was around in the 60s, and the alternative (particle board) not easy to work with.

Heresy I know, but seems logical to me.

Kessler had a pair of black Raymond Cooke LS3/5a in a large grouping of different models (10-12) and the listening panel ranked them all fairly closely - the KEF sitting in the middle of the pack alongside Chartwell and Rodgers and ranking within half a point. Make of that what you will.

I suspect we need to put aside some of the mystery shrouded stories and take these things for what they are.
 
FWIW I suspect much of the secret sauce in the cabinet on this one is the screwed-on baffle. My theory, which I’ve held for many years now, is that (and screwed-on back panels) is the key to most of the BBC cabs sounding so good (Lockwoods etc too). Basically it stops them behaving like a pair of congas, bongos or guitar soundbox. A ‘broken bell’ approach to killing/dissipating resonance. The alternative approach of just throwing high mass and bracing at things tends to sound very wrong to my ears, I can’t think of any speakers of that cabinet design I actually like enough to want to own. I think part of the reason the JR149 sounds so good is it is actually very low mass, very thin wall, and has ‘breaks’ in the cabinet. Light, rigid, doesn’t ring, doesn’t store energy. A very clever cab!

PS Further to our PMs (which was before I read the blog linked in the first post) I suspect some of the LS3/5A secret is just how well that upper bass lift and very deliberately plonking them on the room node in a typical small room works.
 
FWIW I suspect much of the secret sauce in the cabinet on this one is the screwed-on baffle. My theory, which I’ve held for many years now, is that (and screwed-on back panels) is the key to most of the BBC cabs sounding so good (Lockwoods etc too). Basically it stops them behaving like a pair of congas, bongos or guitar soundbox. A ‘broken bell’ approach to killing/dissipating resonance. The alternative approach of just throwing high mass and bracing at things tends to sound very wrong to my ears, I can’t think of any speakers of that cabinet design I actually like enough to want to own!

PS Further to our PMs (which was before I read the blog linked in the first post) I suspect some of the LS3/5A secret is just how well that upper bass lift and very deliberately plonking them on the room node in a typical small room works.

Agreed - the lossy effect of screwing the boards together, the cracked bell effect.
I was thinking about this the other day. when I built my AR4x inspired design I used 15mm birch ply and that was bloody heavy, stiff cabinet.
A tiny 3/5a in 12mm birch is also going to be an incredibly stiff little box.

Something also worth noting with small stand mounts is the floor cancellation when they are placed on stands typically 24" high.
This can make them sound a bit thin in the lower mids to upper bass, then you get the typical bass port woof at the bottom.
The rich balance of the 3/5a probably helps srestore some of this lost body while not over exciting room modes.
 
I have heard the same for late Spendor versions which started to use MDF. There is a video of an LS3/5a club meet-up where Andy Whittle makes this point.

Funnily enough I was having a PM chat with Tony last week and mentioned that my time with a pair of 11 Ohm Spendors in the 90s was not at all good - musically deadpan with ill-defined, bloated bass.

This fits precisely with my experience of 1986 Spendors. I’d heard that MDF was used in their construction, can’t remember whether it was battens, front baffle or both.
 


advertisement


Back
Top