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Revisiting Jim Rogers JR149s

Ditton 15s were about £100-110 IIRC and I think the later XR variant was out by that time. It was a hugely successful speaker, first introduced in the mid-60s, so tons of them about and typically highly discounted. The 149s and LS3/5As were certainly more niche market.

I remember Ditton 15s being absolutely everywhere, I knew at least three friend’s with family systems ending in them (usually a Japanese receiver and PL12D or Trio KD1033 upstream). I’d put money on them being the biggest selling UK speaker of all time. Surprisingly it is getting a lot harder to find a really nice pair of them second hand.

I've got a pair of these that I've worked on. I re-wired them, replaced the cap and some new binding posts. Great little speaker. One of my cabs could do with a veneer repair 8-(.


There’s also the physical space thing, if you went for typically pretentious boutique audiophile components you’d need a crossover box the size of the speakers! The thing that is so clever about both the JR149 and LS3/5A is they managed to get class-leading results (even now!) in a very compact form and at a sensible price. That’s proper engineering!

I’ll certainly be interested to hear how you get on if you do build modern crossovers, though what I learned from replacing the caps with “better” ones, plus a lot of experience with Tannoys (expensive third party and DIY) is a change very often isn’t an improvement! I’d certainly expect to pretty much start again from scratch as just throwing boutique components at Jim Rogers’ original design will almost certainly not work. He very clearly understood exactly what he was doing and factored-in the behaviour of the components he used.

After I’d acclimatised I was surprised just how bad the film caps sounded in comparison to Falcon’s electrolytics, they just lost the balance and coherence of the speaker despite initially fooling me with a perceived increase in clarity. I found just the same with the Tannoys, and after much experimenting/expense use untouched original crossovers there.

PS Whatever you do I strongly advise you keep a stock pair of crossovers as a benchmark. It is so, so easy to fall down a rabbit hole with no firm benchmark to AB against. If you do decide to go this route I do actually have the second pair of crossovers (the ones with film caps) I’d sell as I’m done experimenting now. My JR149s are actually finished! \o/

I couldn't agree with you more on the aesthetics and cleverness of the design of the 149. I don't intend to throw money into boutique components but I will probably need a XO box which is fine by me. I want to see what the speakers can do and I'm happy to have an additional box if this achieves my objective. There is no doubt that the 149 was a great piece of engineering. My 149's are in the low 2000's, so an early pair of Mk1's. The XO's are original with no components removed or changed.


Some pretty strong claims made there?, care to share with us exactly what compromises you consider JR made and what impact they make to the sound stock speakers and what changes you have made to improve on the original design?.

Alan

Hi, Alan. In a nut shell, no. I'm not designing the XO's and I never made a claim that I would be or had any knowledge of how the changes would affect the 149's. I've simply stated I think the design is flawed. Not a claims, merely observations.
 
My 149's are in the low 2000's, so an early pair of Mk1's. The XO's are original with no components removed or changed.

I’d start off by just recapping it like for like. Those old black caps with the red ends will be miles out of spec and in a remarkably inconsistent way (some go way down, some go way up), I measured all mine on the way out and none were even close to their rated values. That done it should give you a good indication as to how they are meant to sound as the resistors and inductors will still be fine.
 
Tony, I've already experimented with recapping in a previous pair. I used the Falcon recapping kit. It was ok but not a night and day difference. I too had some fun measuring the cap values when I removed them. Let's just say 30-40 years later they weren't quite upto spec!
 
I’d start off by just recapping it like for like. Those old black caps with the red ends will be miles out of spec and in a remarkably inconsistent way (some go way down, some go way up), I measured all mine on the way out and none were even close to their rated values. That done it should give you a good indication as to how they are meant to sound as the resistors and inductors will still be fine.
Long before the value changes, the ESR goes skywards, which will do strange things to the crossover, especially with the high baffle step correction in a JR149.
 
Long before the value changes, the ESR goes skywards, which will do strange things to the crossover, especially with the high baffle step correction in a JR149.
Could you explain more about the effect of ESR in crossovers? e.g. what happens when ESR rises, and likewise what happens when a standard ESR cap is replaced with a Low Loss version?

I'm currently facing the situation of replacing a standard 4uf ELCAP with either:
A) a standard 4.7uf ALCAP,
B) a parallel pair of Low Loss 2uf ALCAPs to give 4uf total,
C) a standard 4.7uf ALCAP + 30uf ALCAP wired in series to give 4uf total,
D) a 3.9uf Mundorf ECAP PLAIN (I don't know how this cap's ESR compares to that of a standard or Low Loss ALCAP?).

I understand that Option A) will lower the LPF crossover frequency from 5kHz to 4.25kHz but I don't know the ramifications of the three remaining options?
 
You can only see how sensitive a crossover is by modelling it with LTSpice or Simetrix and adding aseries resistor to the capacitor.
B) Is the probably best solution
You don't know if the original manufacturer selected parts, electrolytics have poor tolerance. KEF certainly did.
 
Hello,

I was wondering how the JR149 would compare to the Audiomaster MLS1. Audiomaster had a license to produce the ls3/5a and the MSL1 are apparently known to be a "cheaper" alternative. Anybody ever had to opportunity to listen to both?

I own a pair of (more recent) Mission 751, the Rogers were initially on my list but I had the 751 for a decent price, would they be an upgrade or similar?

Thank you
 
Here's a pic of the crossovers from the Mk2s I'm thinking of buying -- I just wanted to ask if anyone sees anything unexpected there, please let me know.

JR149-Crossover.jpg
 
Odd mismatch of capacitor brands left to right, but nothing surprises me after finding different resistor values in my pair!

PS I’d not worry about that as you’ll be recapping them as a matter of course given the age. Just make sure all four drivers are ok as best you can.
 
Do both of those PCB's appear to be missing a Cap next to the fuse?

Isn't it an inductor that's missing? There are usually four. Perhaps in this revision they've combined the two that were in series?

The layout is different too, on most the fuse and pot are adjacent.
 
Hello,

I was wondering how the JR149 would compare to the Audiomaster MLS1. Audiomaster had a license to produce the ls3/5a and the MSL1 are apparently known to be a "cheaper" alternative. Anybody ever had to opportunity to listen to both?

I own a pair of (more recent) Mission 751, the Rogers were initially on my list but I had the 751 for a decent price, would they be an upgrade or similar?

Thank you
Hello Rob, I used to have Audiomaster MLS1 and they are still in the family so I hear them. At the time I bought them
I chose them because they were the closest I could find to the Rogers LS3/5a at the time but half the price. I can't of been aware of or had chance to hear the JR149. Years later I bought a pair of Stirling LS3/5a V2 but about 2 years ago bought a pair of JR149' s after hearing some at a friends house and preferring them to my Stirling 3/5a and his Spendor 3/5a. He also has a pair of Audiomaster MLS1 and a pair of KEF LS50's and his JR149 , we have spent a lot of time listening to different combinations with different source components and different amps and both of us prefer by a large margin JR149 Mk1 over all of the rest. You really need to hear some and make up your own mind.
 
My pair of Mk2s arrived this morning and I've put them with the Radford, I'm not set up to do A/B comparisons yet -- I will hook up both speakers and a selector switch soon. But one first impression was striking -- this comment here is true

The basic characteristics of the MkI and MkII speakers are very similar. The only observation that notes the difference is that it takes more volume to get a pair of gold logo MkI to emit a sound than on the MkII speakers.

And this gives me the feeling that they're more of a room filling speaker, rather than a near-field one.

I'd also say that the bass is tauter -- but without being able to switch from one to the other I'm not totally sure.
 
"The basic characteristics of the MkI and MkII speakers are very similar. The only observation that notes the difference is that it takes more volume to get a pair of gold logo MkI to emit a sound than on the MkII speakers."
I chuckled at that quote. Either the author genuinely cannot hear a difference between the two models, is being evasive, or is too lazy to describe them. The differences are pretty evident to my ears so my money is on the latter two possibilities! ;)
 
My pair of Mk2s arrived this morning and I've put them with the Radford, I'm not set up to do A/B comparisons yet -- I will hook up both speakers and a selector switch soon. But one first impression was striking -- this comment here is true



And this gives me the feeling that they're more of a room filling speaker, rather than a near-field one.

I'd also say that the bass is tauter -- but without being able to switch from one to the other I'm not totally sure.

When you're switching between sets, make sure you keep conditions fair. i.e. same height and position in room.

If you're going to have both pairs set up in the room at the same time, stagger them to minimise room bias. i.e. position the mk1s outside left and inside right, and position the mk2s inside left and outside right.
 
I chuckled at that quote. Either the author genuinely cannot hear a difference between the two models, is being evasive, or is too lazy to describe them. The differences are pretty evident to my ears so my money is on the latter two possibilities! ;)


And do you think my comment about tauter bass is in line with what you hear? Or maybe, even, more over it.
 


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