Revisiting Jim Rogers JR149s

[ToTo Man]

I spent the evening taking nearfield measurements of my JR149 mk1 vs mk2, as I was curious about their different voicings. Two pairs of each were measured, to broaden the sample and increase the robustness of the results. (In case you missed it, that was my pathetic attempt at disguising the fact that I own too many speakers! ) . I'll upload the results tomorrow, but to whet the appetite of those who cannot wait, the mk2 is measurably brighter through the upper mids and treble and doesn't have the "BBC-style" presence region dip that the mk1 has. Remarkably, the bass and lower mid response is virtually identical between the two models.

 

[Tony L]

Interesting. You must own a sizeable percentage of the surviving MkIIs!

PS Pop some pics up of the collection!

 

[davidsrsb]

Any chance of measuring the impedance. This often gives clues about the tweeter tweaks

 

[Tony L]

The impedance of the MkIs is included in the Gramophone measurements I posted back in post #122. A lovely tube-friendly 8 Ohms and above very like the LS3/5A. I certainly prefer mine on the Leak’s 16 Ohm tap, which makes sense looking at the plot. The label on the bottom of the 149 says ‘8-15 Ohms’.

 

[ToTo Man]

You want graphs?....... you got 'em!

Disclaimer: All measurements taken at a distance of 1 metre and with the speakers sat atop the same Atacama SE24 24-inch sand-filled metal stand. The mic and speaker stand was kept in the exact same position for all measurements. This meant the mic was on-axis with the JR149 mk2 tweeter but 1.25cm higher than the JR149 mk1 tweeter.

N.B. For some reason the graphs aren't displaying full-size, so if you want to see them full-size you'll have to right-click and choose 'Open in new window'.

A nice easy one to begin with, for all those wondering what impact the "acoustically transparent" foam grille has on the JR149mk1's response. Conclusion: they're not 100% transparent, but pretty close.

Next up is the response of my two pairs of JR149 mk1:

And now the two pairs of JR149 mk2:

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And finally, a comparison of the JR149mk1 vs JR149mk2. The first graph shows the responses without compensating for the slight efficiency difference between the two models, the second graph is my attempt to "level match" by aligning the bass responses:

 

[Tony L]

Interesting stuff. I’ll just repost a 1m tweeter axis plot of one of mine as I’m curious as to the bass differences in room (both ours differ hugely from the Gramophone anechoic response):

How far from a back wall are yours? Mine is about 8” or so.

 

[Tony L]

It is interesting. Some basic trends are clearly there betwen both yours and mine in the mid and upwards, and these correspond fairly well to the Gramophone measurement. Though the bass dips and troughs, whilst kind of similar, does not correspond, so I assume that is our room specific cancellations and the Gramophone measurement is right there.

 

[Robert]

Quite a marked change from the upper mids on upwards, 3-5dB.
The Mk2 looks objectively superior but I suspect many will prefer the balance of the Mk1 in the context of small 'speaker lacking LF gravitas and reach.

 

[ToTo Man]

Interesting stuff. I’ll just repost a 1m tweeter axis plot of one of mine as I’m curious as to the bass differences in room (both ours differ hugely from the Gramophone anechoic response):

How far from a back wall are yours? Mine is about 8” or so.

It is interesting. Some basic trends are clearly there betwen both yours and mine in the mid and upwards, and these correspond fairly well to the Gramophone measurement. Though the bass dips and troughs, whilst kind of similar, does not correspond, so I assume that is our room specific cancellations and the Gramophone measurement is right there.

For measurement purposes I have the Atacama stand positioned in front of one of my GIK Side Reflection Panels and the distance from the front of the stand/speaker to the wall is about 20 inches. The dips we both have in the upper bass are presumably floor bounce cancellations, and the improved extension vs the anechoic measurements is presumably room gain and mode reinforcement (the dimensions of my room 4.2m x 3.8m x 3.25m create axial modes at 41Hz, 45Hz and 53Hz).

BTW - Could the Gramophone measurements be wrong? The LF response printed by Jim on the bases of his speakers is 55Hz @ -4dB, whereas the Gramophone response looks to be 80Hz @ -5dB.

 

[Tony L]

I suspect the disparity in LF reach between Jim’s and Gramophone’s measurement is purely lack of room reinforcement. The 149 is a close to wall speaker, what was called a bookshelf speaker in its day, i.e. the exact opposite of an anechoic chamber! It is the smoothness of the response that interested me. To my ears the 149s have very nice even bass within their obvious volume envelope, though some CDs can sound rather lean and I assume that is just down to the key or EQ hitting a null in my room (I listen in the middle of the room so get no rear wall reinforcement etc).

 

[h.g.]

Quite a marked change from the upper mids on upwards, 3-5dB.
The Mk2 looks objectively superior but I suspect many will prefer the balance of the Mk1 in the context of small 'speaker lacking LF gravitas and reach.

I suspect it is likely to depend on the off-axis response as well. An on-axis dip to counter the tweeter spraying sound in all directions may lead the Mk1 to sound better balanced.

 

[Tony L]

I certainly prefer the Mk I firing behind my listening position rather than on-axis. I have a little toe-in, but not much. I also prefer to be below the teeeter (I prefer my beanbag to a seat), but I do with most flat-baffle speakers, I guess it is time alignment and I’m effectively tilting them a bit by listening low.

 

[ToTo Man]

Quite a marked change from the upper mids on upwards, 3-5dB.
The Mk2 looks objectively superior but I suspect many will prefer the balance of the Mk1 in the context of small 'speaker lacking LF gravitas and reach.

The mk2 does sound cleaner, clearer and less coloured to my ears, although I imagine some might find the balance subjectively 'lean'. I'm really surprised how closely matched they are up to 1.5kHz as subjectively I'd have said the two models sounded different in the lower mids too, but this is obviously my ears being fooled by the mk2's brighter response above 2kHz.

 

[Tony L]

Response plots only measure quantity, not quality!

 

[davidsrsb]

The 100-200Hz area will be very dependent on stand height, room etc.
The 4kHz zone is the interesting change, which will make the MKII sound more exciting, but emphasize sibilants and bad miking.
All the curves are very good and still respectable today.

 

[Tony L]

Small speaker voicing is very easy to get wrong IMO given the inherent response and dynamic limitations, i.e. you have to compensate both for limited bass and low volume. In this context the ‘BBC dip’ is a very useful thing and avoids thinness. ProAc are masters of this and tend to have a slightly scooped mid that helps make them sound far bigger than they are.

 

[Lee T]

I have finally managed to get hold of a pair for £258 (damn fine condition too) gold logo serial number 21939
Can be found here http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=272860959276
Should arrive tomorrow

My question is, what is the best way to go about getting the best from these, equipment, cabling etc..

Are they an easy load for example,
I play mainly at medium levels, to give an example, my Nait 3 never goes past 8 oclock, it's well loud enough at this level in my small room with modern recordings, older recordings tend to need a little more.

 

[Tony L]

Look like a nice tidy pair. Cabling has to be thin and bare-wire as it needs to go through the narrow gap at the rear of the base and screws directly to the crossover. The fanciest cable I’ve found that fits is Chord Rumour, though I’m not convinced I like it any better than 1.5mm VanDamme that also fits. Your stands should be fine but I’d ditch the cones as the thin alloy bases are not like normal speakers. You also don’t want to dent them, which is quite easy. I just use felt pads on mine, I replaced the tired originals with fresh ones and stuck a few on my stands too to make sure I don’t scratch the bases. Be aware they need some wall reinforcement and will sound overly thin pulled out into free-space. They are easy to drive so the Nait should be up to the job. If you have a look at the promo shot of Jim Rogers at work a NAP120 is visible on his workbench, so they should be fairly Naim-friendly. I’ve never tried as I’ve never owned Naim and 149s at the same time! If they have been sitting for a long time do let them wake up for a couple of weeks before forming too much of an opinion as the electolytic caps etc are ancient and will take a good while to even partly reform. Falcon sell a like-for-like replacement capacitor kit which is worth doing if you are competent with a soldering iron.

 

[ToTo Man]

I've never heard a pair of authentic and original LS3/5As, but based purely on the frequency response plots, is it reasonable to suggest that the JR149 mk2 is voiced more closely to the LS3/5A than the JR149 mk1 is? This seems to be the subjective conclusion of the 1981 HiFi News review at least which A/B/C'd all three models.

 

[Radfordman]

I have 15 Ohm Chartwell LS3/5a and JR149 that use the B110 and T27.

From memory, and it's a long time ago I did the comparison, JR149 goes down lower than LS3/5a, but possibly the midrange of the LS3/5a is a little less coloured.