Revisiting Jim Rogers JR149s

[Tony L]

The linked ‘review’ suggests something was very wrong with the MkIs if one of a pair was silent then woke up abruptly to match the other. That can only be a fault condition. That said the perceived differences in efficiency is very interesting. I’ve still not found a measurement or spec for the MkI I fully understand. All I can say for sure is mine are observably louder than the Spendor S3/5R, which don’t seem entirely honest about their sensitivity (IIRC Stereophile observed the R2s as being less sensitive than their spec, and I’m sure the Rs are too). My best guess is the MkI 149 is about 83db. That would make some sense if the Mk2 is 84.5db. That is certainly enough to hear.

 

[ToTo Man]

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

Yes, I do find the mk2's bass sounds more authoritative and agile. Subjectively it also sounds like it extends deeper, but once the mk2 is level matched with the mk2, you're only talking a gain of about 1dB or so, which is pretty marginal. The biggest differences I hear is in the midrange and treble. The mk2's presentation sounds more neutral, less coloured and more resolving to my ears, but perhaps not quite as endearing as the mk1. Bear in mind though that I still have original B110 and T27 units in my mk1s, however I've had five pairs of over the years which is a fairly decent sample size (and FYI all five pairs sounded different to each other, some significantly so, even after recapping which made sod all difference to my ears!). On the other hand, the three pairs of mk2s I've had all sound and measure incredibly close to each other, - make of that what you will.

 

[ToTo Man]

The linked ‘review’ suggests something was very wrong with the MkIs if one of a pair was silent then woke up abruptly to match the other. That can only be a fault condition. That said the perceived differences in efficiency is very interesting. I’ve still not found a measurement or spec for the MkI I fully understand. All I can say for sure is mine are observably louder than the Spendor S3/5R, which don’t seem entirely honest about their sensitivity (IIRC Stereophile observed the R2s as being less sensitive than their spec, and I’m sure the Rs are too). My best guess is the MkI 149 is about 83db. That would make some sense if the Mk2 is 84.5db. That is certainly enough to hear.

My nearfield response measurements of mk1 & mk2 before and after level-matching suggests the mk2 is indeed 1dB to 1.5dB more efficient up to around 1.5kHz, but its sensitivity above 1.5kHz is probably more like 3dB to 4dB higher. These are nearfield measurements taken on-axis with tweeter though so the sensitivities may well converge more at the listening position.

EDIT - For fairness I should probably upload graphs of the mk2 against all of the mk1s I've measured, as I can't say which mk1 is the most "representative" example of a mk1. I'll upload more graphs later.

 

[mandryka]

Yes, I do find the mk2's bass sounds more authoritative and agile. Subjectively it also sounds like it extends deeper, but once the mk2 is level matched with the mk2, you're only talking a gain of about 1dB or so, which is pretty marginal. The biggest differences I hear is in the midrange and treble. The mk2's presentation sounds more neutral, less coloured and more resolving to my ears, but perhaps not quite as endearing as the mk1. Bear in mind though that I still have original B110 and T27 units in my mk1s, however I've had five pairs of over the years which is a fairly decent sample size (and FYI all five pairs sounded different to each other, some significantly so, even after recapping which made sod all difference to my ears!). On the other hand, the three pairs of mk2s I've had have all sounded and measured incredibly close to each other, - make of that what you will.

I’m not going to read this so that you don’t hypnotise me when I set up an A/B comparison

Listening to them now, a string quartet, they sound very lively with the Radford.

 

[ToTo Man]

@mandryka, I also highly recommend replacing the fuses in the mk2s as the existing ones will probably have tarnished ends. The fuses in one of my mk2s were so tarnished I kept getting dropouts in one speaker! If you haven't spare fuses just wrap a bit of foil around the existing ones as a short-term fix.

 

[ToTo Man]

Sadly I only have measurements of two pairs of mk1 and three pairs of mk2 taken on the same day in the same location. The other mk1s were measured previously so aren't strictly comparable, and I no longer own those so can't remeasure.

It seems I need to eat my hat regarding my previous comments about all three pairs of mk2 measuring identically. Two pairs do, but the third pair, which is my treasured NOS find, has less mid & treble output than the other two pairs. I wonder if this might be something as simple as the trimpot being set higher on the other two pairs? I shall need to investigate.

And here's measurements of two pairs of mk1 I no longer own. You can see Pair C (blue) has too much output between 2kHz-3.5kHz and then takes a sudden step down above 3.5kHz. I recapped this pair and also messed about with the HF trimpot but neither of these helped smooth this area out. Pair D (red) has a freakishly abnormal frequency response with a broad hump in the B110's upper operating area. All of the crossover components looked present and correct with no visible signs of tampering so I don't know what the cause was and I didn't keep the speakers long enough to investigate further.

 

[mandryka]

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!

Yes, you were right.

I just wonder whether he designed the Mk 1 for near field listening and the Mk 2 to fill a domestic living room with sound. I’m very glad to have both. What I would say is that the Mk 1s have a special endearing sound quality - I think you said cute midrange in another post. The Mk 2s are more neutral but when you switch, you miss that cuteness, the charm.

I think the imaging in the MK2 is really impressive. It was already exceptional in the MK1 but I think in the Mk 2s there is almost the same sense of “no box” that you have with ESLs. And the image seems deeper to me too.

I’ve used the Mk 2s to replace Spendor SP1s, and what it has made me see is just how much of an interior design imposition a pair of 2 cubic feet boxes are. That matters to me.

I think I’m going to set myself a little project of exploring what modern small speakers, actives and small speakers with small subs, can do. If I could get rid of my ESLs and Gradients and Krell and replace them with a some little boxes which would do the job as well, I’d be very happy. And just maybe it would be worth spending time and money to make it happen.

I’ve been trying them out with a Rotel power amp - I can’t wait to explore what the Radford and the Krell does with the Mk 2. But you know, amps are heavy - I have to be in the mood.

Thanks for the tip about the changing the fuse by the way. I shall get them thoroughly serviced soon. They’re special!

Anyway I’m very glad to have the JR149s, both of them.

 

[ToTo Man]

Yes, you were right.

I just wonder whether he designed the Mk 1 for near field listening and the Mk 2 to fill a domestic living room with sound. I’m very glad to have both. What I would say is that the Mk 1s have a special endearing sound quality - I think you said cute midrange in another post. The Mk 2s are more neutral but when you switch, you miss that cuteness, the charm.

I think the imaging in the MK2 is really impressive. It was already exceptional in the MK1 but I think in the Mk 2s there is almost the same sense of “no box” that you have with ESLs. And the image seems deeper to me too.

I’ve used the Mk 2s to replace Spendor SP1s, and what it has made me see is just how much of an interior design imposition a pair of 2 cubic feet boxes are. That matters to me.

I think I’m going to set myself a little project of exploring what modern small speakers, actives and small speakers with small subs, can do. If I could get rid of my ESLs and Gradients and Krell and replace them with a some little boxes which would do the job as well, I’d be very happy. And just maybe it would be worth spending time and money to make it happen.

I’ve been trying them out with a Rotel power amp - I can’t wait to explore what the Radford and the Krell does with the Mk 2. But you know, amps are heavy - I have to be in the mood.

Thanks for the tip about the changing the fuse by the way. I shall get them thoroughly serviced soon. They’re special!

Anyway I’m very glad to have the JR149s, both of them.

I'm pleased I'm no longer alone in my appreciation of the mk2! They're a speaker very much worth owning IMO so enjoy them!

Regarding your desire to banish the big boxes, - small monitors and subs can do wonderful things. I briefly tried my Tannoy Autograph Minis with my XXLS400 subs and, even without taking the time to dial things in properly, it put an instant grin on my face to hear the Minis suddenly producing full-range sound! What the combination cannot do, however, is produce that impactful and effortless shifting of air in the upper-bass region, which is usually above the subs' crossover frequency. If this is a quality that's important to you then I suspect you might find downsizing too much of a compromise, but no harm in trying it to find out.

 

[Barry van O.]

Hi everybody. I'm Dutch and English is not my native tongue. So forgive me if things are spelled incorrectly. I hope you can help me out. I recently came across a pair of JR 149 MKI's with black acryl tops and red logos. I've owned plenty of vintage Kef speakers using the B110 and T27 (and even and build a few LS3/5a's using Falcon crossovers in the past) so I was curious to hear the JR149's. They sound a bit harsh and bright at times and they have some very odd crossovers that look different from what I've seen here. I tried to include a photo of the crossovers but my post keeps getting blocked for some reason. Any idea how I can fix that and get some feedback on the crossovers?

 

[Tony L]

My apologies, there is a spam filter that prevents links for a users’ first three posts, it is sadly necessary as the site is under constant attack from spam-bots etc and it prevents some remarkably ugly content ever getting viewed.

Can you describe the crossovers you have, e.g. are they round or square? Also the JR149 does like to be fairly close to a wall, it is not as free-space friendly as a LS3/5A by any extent as it lacks the upper-bass bump. May also be worth looking at your tweeter level controls (assuming your crossover has them), someone may have been in there fiddling. On a normal crossover it makes sense to set both to the middle point and then trim from there, I find I like a little cut, which IIRC is actually clockwise rather than anti-clockwise, so a bit counter-intuitive.

 

[davidsrsb]

Do the tweeters look in good condition. You can tests a tweeter safely out of circuit by connecting a single AA battery both ways across the terminals and look for even movement, in and out.

 

[Barry van O.]

No worries and thanks for clearing that up.

 

[Barry van O.]

Both the T27 tweeters and b110 woofers are in good condition. I'll try placing the speakers closer to the walls.

 

[ToTo Man]

Hi everybody. I'm Dutch and English is not my native tongue. So forgive me if things are spelled incorrectly. I hope you can help me out. I recently came across a pair of JR 149 MKI's with black acryl tops and red logos. I've owned plenty of vintage Kef speakers using the B110 and T27 (and even and build a few LS3/5a's using Falcon crossovers in the past) so I was curious to hear the JR149's. They sound a bit harsh and bright at times and they have some very odd crossovers that look different from what I've seen here. I tried to include a photo of the crossovers but my post keeps getting blocked for some reason. Any idea how I can fix that and get some feedback on the crossovers?

Are these the crossovers you have?

 

[Barry van O.]

 

[ToTo Man]

Ok, you have the original crossover but it looks like someone has replaced the electrolytic capacitors with polys, which is probably responsible for the brighter sound you hear. Turning the HF trimpot anti-clockwise may help to restore a more natural balance between bass and treble, see if that helps?

EDIT - These are Red Logo 149s aren't they? The caps may well be original then, I've seen pictures of red logo 149s with poly caps, but those are bigger in physical size and stronger yellow colour than I remember.

 

[Tony L]

Interesting. Certainly the correct boards for an early (pre-fuse) pair, but I’ve never personally seen the yellow capacitors before, but Jim Rogers definitely changed type many times. I’ve seen all kinds of stuff used so I’d not like to say if they were original or not. I just don’t know. The think that confuses me is the markings, e.g. what does 335k mean? That sounds more like marking for a resistor than a cap which would be in F, uF, pF etc. I’m not electronics trained though.

Any sign of re-work on the underside of the board? You can usually tell if anyone has been in.

FWIW I rebuilt one set of boards with poly-caps and decided I really didn’t like the presentation, so went back to electrolytics, so it may well be worth recapping them with the Falcon Elcap kit (which is what mine have).

 

[Barry van O.]

Thanks for the replies. I thought they might be the original crossovers but the yellow capacitors got me confused. I'm not electronics trained either but I've fixed many crossovers over the years and I'm fairly sure 335K stands for 3,35μF. That would also make sense because 3,3 μF elcaps have been used in the MKI crossovers.
I'm going to replace these yellow caps with Clarity Cap PWA capacitors. Those are relatively small and smooth sounding. I've used them in a set of early Kef Chorals and they sound great bringing more detail and space to the sound. If that doesn't work I might try Mundorf Ecaps.

 

[Tony L]

Personally I’d do them first with the bog-standard Falcon Elcap kit (link) as they sound exactly how a JR149 should sound to my ears. Only then see if you can improve things. As mentioned upthread I bought a second set of boards off eBay and recapped them with M-Cap film caps and after confusing myself for a bit came down very firmly in favour of the bog-standard electrolytics. Initially the film caps sound cleaner and more detailed, but the coherence, body and natural warmth is just gone. It turns a truly beautifully balanced, neutral and musical speaker into something over-analytical and sterile. I had a far easier job here than you will too as it was so easy to swap over the crossovers (mine have the plug connector). It was one of those changes that initially you think ‘oh, that’s better’, but then after a week realise you just don’t want to listen to the system anymore as it just isn’t enjoyable. So many ‘hi-fi’ “upgrades” are like this IMO. The really good kit never draws attention to itself.

 

[Barry van O.]

I agree with you there. I've noticed that all the resistors on my crossovers seem to be original but have different values from other early ones so I'm guessing the crossovers were tweaked for filmcapacitors way back when they were originally build. I've ordered the Clarity Cap PWA's a week ago and they came in yesterday so I'm gonna give them a try and let you know how it works out. If it doesn't work out I'll try either the Falcon Elcaps or the new Mundorf Ecaps at 50volt. I'll post some photos of of the soldering results.