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Revisiting Jim Rogers JR149s

Discussion in 'classic' started by Tony L, Mar 21, 2013.

  1. kevinrt

    kevinrt pfm Member

    Thanks.
    Out of interest, what are the orange cylinders?

    Kevin
     
  2. Tony L

    Tony L Administrator

    Inductors, basically wire wound around a ferrite core. They don’t go out of spec so don’t worry about them.
     
  3. kevinrt

    kevinrt pfm Member

    OK. Thanks.
    Kevin
     
  4. kevinrt

    kevinrt pfm Member

    Here’s the other side of one crossover.Presumably they’re both the same.

    [​IMG]BB9F83A2-6315-4AEB-80B4-CD09246CF9EF by Kevin Thomas, on Flickr
     
  5. ToTo Man

    ToTo Man the band not the dog

    These are interesting. Gold logo bases but the decal with the specification on the underside is the older burgundy style which IIRC appeared on the Red logo version. The tropical fish capacitors are also intriguing, I haven't seen these used in JRs.
     
  6. Tony L

    Tony L Administrator

    Yes, I spotted those and was close to flagging them in the interesting eBay auctions room. They look like a very early gold-logo pair and again give some clues as to the ongoing development as they have the front-baffle deadsheet and foam, but have the original fuseless crossovers. The ‘tropical fish’ caps are interesting and I’ve seen those used before. They look totally stock to my eyes and in very nice condition. It would be interesting to know the resistor values and whether they match the schematic.
     
    ToTo Man likes this.
  7. TonyScarlett

    TonyScarlett pfm Member

    Just had a quick look. According to the schematic the resistor closest to to tweeter trimpot should be 4R7. Most JR149 crossovers I've seen pictured including the linked pair have 5R6 in this position. My current pair SN99** which are also the earlier fuseless type are one of the few I've seen that actually have the correct (according to the schematic) 4R7 resistor in this position. All the other resistors in the linked pair are correct (again, according to the schematic).
    TS
     
  8. Tony L

    Tony L Administrator

    The schematic may well not be correct. It is just something I found on the internet so may just represent one pair of JR149s. I have no connection to it.

    Anyone any guesses as to what that resistor value change would have subjectively?
     
  9. TonyScarlett

    TonyScarlett pfm Member

    Here is a pic of the crossover off my current JR149s before I replaced the caps & resistors. Interestingly the 4R7 resistor nearest the trimpot has a different colour body to the rest so whether it's original or not is anyones guess. I just replaced like for like with the values.
    [​IMG]
    Gone back over the pics of my first pair of JR149s, it had 5R6 resistors in that position.

    Thinking about it, one of the reasons these crossovers seem to have such a random selection of different brands & types of components could simply be because of the industrial strife happening in the 70's. Jim Rogers possibly just had to use whatever components he could get hold of to keep production going.

    TS
     
  10. S-Man

    S-Man Kinkless Tetrode Admirer

    Probably doesn't matter if it's 4R7 or 5R6. VR1 will most likely be able to compensate for either.
    I suspect they measured each speaker and adjusted the pot to accommodate resistor tolerances and tweeter sensitivity variations.

    Anyone know the value of VR1?
     
  11. Barry van O.

    Barry van O. Member

    I have somewhat of a luxury problem at the moment. In front of me are three sets of crossovers. All the values are the same it's the capacitors that are different. I've used Mundorf E-caps in one set, Expotus & Panasonic metallized polypropylene film capacitor in another set and Clarity Cap PWA's in the third set. I have to be honest but they all sound very similar. There's very little to no difference in sound quality. They're equally detailed, dynamic and easy to listen to. I've tried them all out for a few days and I don't really have a favorite. The Expotus & Panasonic metallized polypropylene film capacitors were hard to come by but look nice. Maybe the only reason not to use electrolytic caps is their shorter life span. If you listen to your speakers day in day out, you will need to replace them in 10 years. If you use your speakers a little less it can be double that.
    I'll leave in the crossovers with the Clarity Cap PWA's since they will add the most value to my current set.

    [​IMG]
     
    ToTo Man likes this.
  12. Tony L

    Tony L Administrator

    That’s an interesting observation, and might go some way to explain why quite large variations of setting are seen in the wild.
     
  13. S-Man

    S-Man Kinkless Tetrode Admirer

    I am guessing/extrapolating from Gale 401s.
     
  14. Barry van O.

    Barry van O. Member

    Short follow up: It's weird but after days of listening and comparing crossovers with different kinds of capacitors, I have to say that the electrolytic capacitors do indeed sound best with these speakers. It's not a huge difference but they just do.
     
    Tony L likes this.
  15. davidsrsb

    davidsrsb pfm Member

    It is possible that they are adding a little harmonic distortion at the turnover frequencies. More likely than ESR effects
     
  16. ToTo Man

    ToTo Man the band not the dog

    There was a bit of a mix up with the foams. They looked great, but were cut to a depth of 18mm instead of the 12mm I requested and therefore protruded out beyond the wooden end caps by about 6mm and made the speakers look a bit tubby!

    Original foam on the left, new 18mm foam on the right:
    [​IMG]

    New foams were cut, and this time all the specs are perfect, - I'm absolutely delighted with the way these look on the speakers. All I need to do now is get some replica "JRmkII" badges made, though I don't think I'd risk attaching these onto the foam, probably safer just to blu-tac them onto the front of the metal base.

    New 12mm foams:
    [​IMG]
     
  17. mandryka

    mandryka pfm Member

    [​IMG]

    Just a note to say that the brackets work really well in this position, presumably because the alcoves are giving them enough air behind. It’s a neat solution, I’m very pleased.
     
    ToTo Man, The Bish and TonyScarlett like this.
  18. ToTo Man

    ToTo Man the band not the dog

    Have you thought about adding a rug? It would really tie the room together. ;)
     
    mandryka likes this.
  19. Danny C

    Danny C New Member

    Hi all,

    First time poster here. Been following a bunch of these threads for a while, I'm found them very informative and enjoyable reads!

    I'm a proud owner of pair of JR149s. For a long time I've had them going into an A&R A60 with lovely results. Recently, I picked up a pair of Stirling LS3/5A V2s. I've run them into the A60 and am using my RME ADI-2 DAC as a preamp/DAC with Roon and stoked with the combination. I'm quite happy to leave that as a standalone system for my workspace - the sound is just bliss but aesthetically the 1cm timber on both the speakers and amp is quite nice on the eyes too!

    Now, I've found a well priced JR Super Woofer (doubling as a side table) with a EX1 Crossover unit and BA1 Power Amp. It doesn't come with the Low Pass Filter Amp which makes hooking it up to my A60 a little tricky (I think?). I tried to attach a link to a PDF for the Super Woofer brochure but perhaps my post count is too low, it's an easy Google though.

    So, my question is which amp/pre amp combo might work well with the EX1 Crossover unit. I'm thinking a Quad 303/33 combo but very open to ideas/suggestions.

    Many thanks!

    Danny
     
  20. TonyScarlett

    TonyScarlett pfm Member

    Hi Danny

    Welcome to PFM. I don't know anything about the JR super woofer so can't offer any advice there but I can tell you the Quad 33/303 sounds superb into Stirling V2s as that's what I'm using in my main system.
    Seems we have similar tastes in speakers, I also have JR149s in my 2nd system on the end of my Leak ST20.
    The A60 is about the only amp left on my bucket list.

    TS
     

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