Revisiting Jim Rogers JR149s

[Tony L]

I presume you're measuring this from the back of the end cap, Tony, not from the front baffle?

Yes, the space behind the cabinet.

Interesting graph. It certainly highlights my setup, whilst sounding astonishingly clear and lacking in room effects, does suffer a lot from a lack of bass reinforcement. The speakers roll off in the bass much as they do in the anechoic measurements I’ve seen.

One thing I touched on in the LS3/5A thread and I think inadvertently tried was the theory formed by some LS3/5A fans (I linked to an interesting blog) that in typically sized rectangular rooms such as those most of us have placing the speakers on the wide dimension (i.e. firing across the narrow) and positioned about 1 metre away from the wall puts the speaker on a 40Hz node, which with a tiny well behaved infinite baffle speaker of limited extension actually boosts it below the roll off. The LS3/5A better able to pull this trick off than many as it has a lift at about 110Hz so doesn’t sound at all lean out away from a wall (as 149s tend to IME). I was certainly quite shocked by how much bass they had downstairs just plonked in front of the Tannoys and listened to from my normal sofa which is close to the rear wall. I didn’t keep them in that system long, I just wanted a quick indication of what the 124/Verdier/303 would sound like through them (which was very, very good!).

PS Can you do a ‘psy’ of that plot? It looks very good indeed to my eyes. Maybe not the ‘target’ downward tilt the measurement crowd seem to aim for, but very flat for 1/12 smoothing. Bet it sounds very decent.

 

[ToTo Man]

Yes, the space behind the cabinet.

Interesting graph. It certainly highlights my setup, whilst sounding astonishingly clear and lacking in room effects, does suffer a lot from a lack of bass reinforcement. The speakers roll off in the bass much as they do in the anechoic measurements I’ve seen.

One thing I touched on in the LS3/5A thread and I think inadvertently tried was the theory formed by some LS3/5A fans (I linked to an interesting blog) that in typically sized rectangular rooms such as those most of us have placing the speakers on the wide dimension (i.e. firing across the narrow) and positioned about 1 metre away from the wall puts the speaker on a 40Hz node, which with a tiny well behaved infinite baffle speaker of limited extension actually boosts it below the roll off. The LS3/5A better able to pull this trick off than many as it has a lift at about 110Hz so doesn’t sound at all lean out away from a wall (as 149s tend to IME). I was certainly quite shocked by how much bass they had downstairs just plonked in front of the Tannoys and listened to from my normal sofa which is close to the rear wall. I didn’t keep them in that system long, I just wanted a quick indication of what the 124/Verdier/303 would sound like through them (which was very, very good!).

PS Can you do a ‘psy’ of that plot? It looks very good indeed to my eyes. Maybe not the ‘target’ downward tilt the measurement crowd seem to aim for, but very flat for 1/12 smoothing. Bet it sounds very decent.

Psy smoothing as requested:

They do sound very good, they certainly don't sound tonally imbalanced despite the lack of downward tilt (I think I must subconsciously adjust my expectations when I listen to pint-sized speakers, - if my Tannoys or Celestions produced such a flat response I'd be craving more bass but with small speakers I don't seem to be as bothered).

If I''m being hypercritical I find these JR149 mk1's slightly 'hard' or 'nasal' sounding in the upper mids / lower treble and lacking just a little in the way of openness/sparkle/air in the upper registers. The latter is interesting as the graphs don't show them to be lacking much if any in this area! I suspect it might be the relative forwardness between 1kHz and 4kHz that's giving me the impression of a slightly opaque top end, as I quickly tried pulling down the midrange by a couple of dBs and this subjectively seems to have ameliorated some vocal colouration and allows the upper frequencies to come through with a little more sweetness and extension.

 

[ToTo Man]

Just to take things to the extreme and illustrate the impact of listening distance from the rear wall on the JR's tonal balance, I took a measurement with the mic in the middle of the room (190cm from the rear wall) and another very close (40cm) to the rear wall. It makes for an interesting comparison with the 100cm rear wall measurement:

 

[Tony L]

That makes the point very well.

 

[ToTo Man]

I figured I might as well measure my other pair of JR149 mk1 since I'm currently in 'JR mode'. This pair also has gold logo bases, dedshete around the T27 and beige foam below the lip of the top end cap.

I didn't warm to this pair quite as much as my other pair and I think the FR might explain why. The upper mids are slightly more elevated and the top octave is a little more rolled off, the combination of which takes the tonal balance further away from my ideal for music (they are however perfect for TV where a little bit of additional vocal presence is very welcome). It doesn't look like much in the graph but the ear is most sensitive around 3kHz-4kHz so even small changes are audible. This pair also appears to have a smidgen less bass extension, but not enough to notice (not to my ears anyway).

I should note that all my JRs are still in original condition, i.e. original drivers and crossover components, so there may be gains to had from updating the resistors and caps, though I do remain a little skeptical of the latter as a pair of 149s I recapped with ALCAPs almost 10 years ago (and no longer own) sounded the same to my ears before and after. However, I suppose I ought to replace the ELCAPs as a safety precaution more than anything else. I also don't think I've had these two pairs upside down with the covers removed to compare component values on each board; I guess this would be prudent in light of Tony finding mismatched resistor values in his pair.

I'd like to fit LS3/5A tweeter grilles on the T27s in a pair of my JR149s as I'm curious how this will affect the MF/HF balance, but I don't want to disrupt the staples holding the grilles in place (last time I removed a set of JR149 mesh grilles I had to reattach them with masking tape as the staples would no longer hold the grilles firmly enough in place). Performing this test on my MCR2A instead whose T27 is easier to access should however give an indication of the likely effect on the JR149. I still have a strong suspicion that the T27 grille is at least partly responsible for the LS3/5A having more HF energy than the JR149 as shown in Tony's measurement.

 

[ToTo Man]

@mandryka, curious for an update on your thoughts on your mk2 JR149s? Having listened to (one of my pairs of) mk1 for the past couple of weeks I've just swapped in (one of my pairs of) mk2 and the differences are pretty interesting.

The two most obvious differences that are immediately noticeable to me are:
- mk2 provides noticeably more treble detail. Cymbal brushwork and ambient reverb tails etc are clearer and more airy. The mk1 sounds a little dry/dead in the top end by comparison.
- mk2 midband sounds slightly thinner/recessed. Vocals, electric guitars and piano don't sound as pushed forward in the soundstage as in the mk1.
The combination of the above produces a soundstage with more depth and spaciousness in the mk2.

Interestingly, my subjective observations don't entirely tally with the FR measurements. While the mk2 clearly has more HF energy than the mk1, the mk2 is equally as forward as the mk1 in the upper mids, perhaps even a little more so than the mk1, yet it sounds the opposite.

(Note: The mk2 has slightly higher sensitivity than the mk1, I wasn't sure of the best frequency to align the graphs so I chose 42Hz, this required lowering the level of the mk2 by -1dB).

I believe my subjective impressions can be explained by the "masking effect", where an elevation in one area of the frequency response impedes the brain's ability to resolve frequencies above this if they are at a lower level. I appear to be particularly sensitive to this, which is why I often resort to using EQ with my speakers and headphones. In the case of my mk1 JR149s, lowering the slight bump around 3.5kHz allows me to hear more detail and sweetness in the upper registers. Since the mk2 is already +2 or +3 dB louder in the upper frequencies, this is presumably why I don't notice the bump in the upper mids.

My other pair of mk2 JR149s (the pair I found boxed in NOS condition), has less treble output than the pair of mk2 measured in the above graph, so I wonder if a previous owner has increased the level of the HF trimpots on the crossovers? Or perhaps the ESR of the caps in my NOS pair has increased due to the speakers sitting unused for so many years before I bought them? I can't be @rsed fetching the NOS pair from their box just now to check the trimpot settings, but here's a measurement of all three pairs of mk2 I took in 2017, it clearly shows that my NOS pair has around -2dB less HF energy than the other two pairs, which might actually be preferable for a more balanced tonality.

 

[Tony L]

The MkI vs. II plot is fascinating. The bass drivers looks identical, the dips and peaks clearly being the room or mic position. Things only seem to start to separate from about 1.5kHz up, and some of that looks like a relative tweeter level thing. The interesting thing to me is the differences in plot, the most significant being a peak at around 2.6kHz on the Mk II that clearly doesn’t exist on the MkI. Given that being there I’m surprised subjectively you find the IIs more recessed/less forward. Looking at that plot I’d be inclined to knock the Mk II tweeter down a notch assuming it has a level pot the same as the MkI. On paper at least it looks like the MkI is closer to a ‘target response’ curve, though as ever I’d do the final deciding by ear. Regardless I’m surprised by how close they look!

PS I don’t understand why the spike I mention doesn’t seem to be there on the second multiple MkII plot? My saying that just moving the mic a couple of inches makes a crazy amount of difference. I’m still far from convinced typical in-room measurement has much value beyond helping find a listening position. I’m not convinced it is much help when tweaking, restoring etc.

 

[ToTo Man]

The MkI vs. II plot is fascinating. The bass drivers looks identical, the dips and peaks clearly being the room or mic position. Things only seem to start to separate from about 1.5kHz up, and some of that looks like a relative tweeter level thing. The interesting thing to me is the differences in plot, the most significant being a peak at around 2.6kHz on the Mk II that clearly doesn’t exist on the MkI. Given that being there I’m surprised subjectively you find the IIs more recessed/less forward. Looking at that plot I’d be inclined to knock the Mk II tweeter down a notch assuming it has a level pot the same as the MkI. On paper at least it looks like the MkI is closer to a ‘target response’ curve, though as ever I’d do the final deciding by ear. Regardless I’m surprised by how close they look!

PS I don’t understand why the spike I mention doesn’t seem to be there on the second multiple MkII plot? My saying that just moving the mic a couple of inches makes a crazy amount of difference. I’m still far from convinced typical in-room measurement has much value beyond helping find a listening position. I’m not convinced it is much help when tweaking, restoring etc.

The 2nd plot in post #986 (multiple mk2s) was a nearfield measurement taken from 1m away on tweeter axis (88cm high) with no objects in the vicinity to cause reflections.

This more recent nearfield measurement from post #970 also shows no peak at 2.6kHz.

The first plot in post #986 is with the mic raised to listening height (104cm) and the speakers moved into listening position (located to the sides of my subwoofers with my hifi rack in between and protruding out in front of the speakers, so opportunity for reflection off the top surface of the subs and also the sides of the hifi rack). I would however have expected these reflections to affect the mk1 and mk2 equally given the driver alignment in the cabs is near enough identical.

I've just experimented with a quick EQ shelf filter to bring everything above 2kHz down by approx -1.5dB and I reckon it's an improvement so I'll have a play with the trimpots at some point to see if I can replicate this new target curve.

 

[mandryka]

The most I can say is that I’m really impressed by the Mk 2s at the moment, the Mk 1s aren’t being used. I don’t feel they are a near field primarily speaker like the Mk1. At some point I plan on comparing the Mk1s with my Spendor SP 1, it’s not obvious to me which would win that competition, I’m inclined to think the Rogers, despite their small size.

 

[ToTo Man]

I should state for completeness that all of the measurements I've uploaded from post #970 onwards have been with the ribbed foam grilles removed, as it's much easier to align the drivers with the mic if I can actually see them!

However, on the multiple mk2 plot in post #986, my NOS pair were measured with the foam grilles on, because they are not easily removable (they aren't joined at the back like the mk1, they slip on and off like a sock) and I didn't want to risk stretching them (it's a miracle they're still in as new condition after 40 years!). Fortunately these grilles still have their original JR149mk2 badges attached, which makes it easy to see when they're on-axis.

I measured the acoustic transparency of the mk1 ribbed foam grilles a few years ago in this 1 metre nearfield measurement and found them to be essentially transparent, absorbing less than 1dB of HF, which would only account for a fraction of the difference in HF level between my NOS pair and other two pairs of mk2.

 

[Tony L]

I’ve never been able to hear the grilles. Not even as a teenager with my first pair. A real contrast to the usual framed cloth grilles which were very audible at that age!

 

[ToTo Man]

I’ve never been able to hear the grilles. Not even as a teenager with my first pair. A real contrast to the usual framed cloth grilles which were very audible at that age!

I used to be able to hear the grilles when I had 149s and 150s either side of my computer monitor in my early 20s (living the dream I was! ), but I wouldn't feel so confident partaking in a blind A/B test now! It still amazes me how an unassuming rectangle of ribbed foam can transform the 149 & 150 from somewhat of an aesthetic ugly duckling into one of the coolest loudspeakers designs ever. Flat foam just doesn't do them anywhere near the same level of justice...

 

[Tony L]

Agreed. The sculpted grilles are essential and for me they remain one of the best loudspeaker designs aesthetically, up there with Gale 401s, Klisch La Scalas etc. I still can’t understand why no one has brought the JR concept back, it is so clever from so many perspectives (low mass, inert, good dispersion, good internal damping etc) and wasn’t expensive to make. I guess the nearest are things like Genelecs, Neumanns etc which use very cleverly designed cast metal cabs.

 

[Graham H]

I believe my subjective impressions can be explained by the "masking effect", where an elevation in one area of the frequency response impedes the brain's ability to resolve frequencies above this if they are at a lower level. I appear to be particularly sensitive to this

If I understand you correctly I think you have eloquently nailed something in that comment, mirroring my own experience with Falcon LS3/5as. Subtle details lower in the mix or acoustic space appear effortlessly and cohesively.

 

[ToTo Man]

The HF trim pot on the mk2 appears to effect a greater change in tweeter output level than the mk1. When I measured the mk1 trimpot the maximum amount of adjustment was 3dB (or +/ 1.5dB). The mk2 trimpot provides an adjustment of almost 5dB (or +/-2.5dB).

This first plot was taken with the speaker upside down for easy access to the crossover. All the other plots were taken with the speakers the correct way up!

Adjusting the left speaker's trim pot was a doddle but the right speaker's pot was a bit erratic and I could hear/feel a 'crunching' noise from this pot as I adjusted it (not through the speakers but from the pot itself), perhaps some corrosion or debris, so I should probably clean/lubricate it. What contact cleaner is more appropriate on a pot like this, DeOxit D5 or Faderlube F5?

I adjusted the left speaker first by ear from the listening seat and then set both speakers up for a nearfield measurement so I could match the tweeter level of the right speaker as much possible. I'll live with this setting for a few days before tweaking it further if needed, but I suspect I'll leave it where it is and instead use EQ to shave off a little more upper mid range as I'm not sure I'd want to roll off the output above 10kHz any more than it is (I am partial to a bit of 'air'!).

I thought it would also be interesting to compare mk2 to mk1 now that the mk2's tweeter output level trimpot has been lowered. As you can see, the FR of both models are now uncannily alike!

 

[ToTo Man]

I'm currently in discussion with Graham Hartle regarding having foams made for my JR149 mk2s. I'm in a dilemma whether to replicate the unique mk2 foam design or to go with the classic mk1 design, which the JR150 also uses. Replicating the mk2 design would be more period correct, while reverting to the mk1 design would streamline the appearance of my JR collection. The mk2 design is going to cost more but I'll get a discount if I order more than one set due to economies of scale, however my decision to go for the mk1 or mk2 design is ultimately going to come down to aesthetics and I'm currently still undecided. Which would you go for?

I unboxed my NOS mk2s this morning to take measurements and photos of the foams for Graham and was saddened to see they have begun to rot, despite my keeping the speakers in plastic bags inside their box inside the darkness of my wardrobe. Damn you ozone!!!...

EDIT - If anyone is interested in having mk2 foams made then please let me know ASAP as there may be a further discount if the order quantity is increased.

 

[Tony L]

You should definitely go original spec!

Seeing a good picture of the original grille is interesting as they look to have a bevel top and bottom on the bars. I’ve always had a nagging doubt that my original red-logo MkIs had that too and that I didn’t recreate it with my grilles. It is also interesting that those are obviously grey, not black, and again I’ve had some doubts there too. I like mine and won’t replace them, but interesting to see a good picture of an original spec.

You are lucky having something to work with as you can count ‘bars’, take measurements etc. I had to work from vintage pictures and do my own math. I think I got the right number of bars (an odd number to align one over the tweeter/logo as in original pics), but I think they should have that bevel too.

 

[mandryka]

I'm currently in discussion with Graham Hartle regarding having foams made for my JR149 mk2s. I'm in a dilemma whether to replicate the unique mk2 foam design or to go with the classic mk1 design, which the JR150 also uses. Replicating the mk2 design would be more period correct, while reverting to the mk1 design would streamline the appearance of my JR collection. The mk2 design is going to cost more but I'll get a discount if I order more than one set due to economies of scale, however my decision to go for the mk1 or mk2 design is ultimately going to come down to aesthetics and I'm currently still undecided. Which would you go for?

I unboxed my NOS mk2s this morning to take measurements and photos of the foams for Graham and was saddened to see they have begun to rot, despite my keeping the speakers in plastic bags inside their box inside the darkness of my wardrobe. Damn you ozone!!!...

EDIT - If anyone is interested in having mk2 foams made then please let me know ASAP as there may be a further discount if the order quantity is increased.

I didn’t realise the Mk 2 originals were ribbed, mine aren’t. I must say, I don’t like the ribbed foam, I like my foam smooth and tight.

 

[ToTo Man]

You should definitely go original spec!

Seeing a good picture of the original grille is interesting as they look to have a bevel top and bottom on the bars. I’ve always had a nagging doubt that my original red-logo MkIs had that too and that I didn’t recreate it with my grilles. It is also interesting that those are obviously grey, not black, and again I’ve had some doubts there too. I like mine and won’t replace them, but interesting to see a good picture of an original spec.

You are lucky having something to work with as you can count ‘bars’, take measurements etc. I had to work from vintage pictures and do my own math. I think I got the right number of bars (an odd number to align one over the tweeter/logo as in original pics), but I think they should have that bevel too.

The mk2 foams are in fact black (or as close to black as my eyes can tell). I increased the exposure in the above image to make the sculpting more visible. This is how the (original) mk2 foam looks vs Graham's replica mk1 foam:

Measuring them has been a challenge.

According to this website, the mk1 grilles are 313mm tall and the mk2 grilles are 333mm tall. My mk1 grilles vary between 312-313mm and are a perfectly snug vertical fit. The flat foams that are on my other mk2s (not pictured) vary between 332mm and 335mm and I can see a gap in places around the top rim. I was therefore going to request 335mm instead of 333mm but my dad suggested 334mm as a compromise as he doesn't fancy trimming them down if they arrive too tall.

I cannot find info on length but my two pairs of mk1 grilles vary between 638-645mm. The flat foams on my mk2 are 680mm but there is a gap of a few mm's where the two ends meet which disappears if you pull the foam tighter. I reckon 685mm would give me enough safety margin, any longer and I'd probably need to trim it.

My stock mk2 grilles have 27 'bars' and 27 'spaces'. As best as I can measure, the bars are 15-17mm wide (each one varies) and the 'spaces' are 9-10mm wide (again each one varies). Here are some permutations:
- 27 x 17mm bars + 27 x 10mm spaces = total length 729mm,
- 27 x 17mm bars + 27 x 9mm spaces = total length 702mm,
- 27 x 16mm bars + 27 x 10mm spaces = total length 702mm,
- 27 x 16mm bars + 27 x 9mm spaces = total length 675mm.

The replica mk1 foams have 33mm wide 'bars' and 10mm wide 'spaces'. Also, I thought the mk1 foams were 10mm thick but they're actually 12mm thick (12mm at the 'bar' sections and 6mm at the 'space' sections).

Regarding the chamfer on the edges on the mk2 foam, I'm not sure if Graham would have the equipment do this or if I even have the heart to ask about as it does seem an incredibly finicky detail, nice as it is...

 

[ToTo Man]

I didn’t realise the Mk 2 originals were ribbed, mine aren’t. I must say, I don’t like the ribbed foam, I like my foam smooth and tight.

It's all a matter of taste, but smooth foam on a JR just looks insipid to me.

FWIW - You can make the ribbed foam as tight as you wish by drawing it in at the back in exactly the same way as the smooth variety.