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JR150 Restoration Thread

Discussion in 'classic' started by ToTo Man, Jul 31, 2016.

  1. Tony L

    Tony L Administrator

    They look within typical tolerances to me. The 2db bump at about 1.3K is the only minor issue, and I'm sure I have similar even with my rebuilt 149s and modern pair-matched drivers.
     
  2. ToTo Man

    ToTo Man the band not the dog

    Yes I'm very happy with the matching of the bass drivers, perhaps I'll leave 'em in until the 'clacking' becomes an annoyance.

    BTW - I've just updated my original post with some distortion measurements. The suspected 'bad' original tweeter I replaced shows increased distortion particularly across the 2kHz-4kHz dip.
     
  3. Tony L

    Tony L Administrator

    Definitely check for air-leaks (no, I don't know how either) as I suspect a significant leak could alter the behaviour sufficiently that the driver bottoms. Check any gaskets haven't turned to dust. I was pleased when my new Falcon units came with gaskets as the existing ones were flat as a flat thing.
     
  4. davidsrsb

    davidsrsb pfm Member

    The old review clearly shows a droop in the 3~4 kHz area, so that is the way they were voiced.

    Rising treble on a tweeter means that it is beaming. Not as bad as it sounds as the off axis output falls away, meaning that the in room average is flat. Just aim the speakers down the room, rather than at the listening hot spot.

    Distortion at the low end of a tweeter output can just be a bad design (small linear excursion) or sticking problems. This can be ferrofluid or foreign bodies in the coil gap like dust and glue residue.
    Many tweeter can be carefully opened to get at the coil and inspect the gap
     
  5. ToTo Man

    ToTo Man the band not the dog

    I measured my other pair of JR150 loudspeakers tonight to obtain a 'Reference' of sorts for the pair I am restoring. Apart from a couple of fairly small divergences at ~1kHz and ~4.5kHz they are a pretty good match:
    [​IMG]

    The 'Reference' pair of JR150s vs the 'Project' pair of JR150s before any restoration:
    [​IMG]

    The 'Reference' pair of JR150s vs the 'Bad' JR150 from the 'Project' pair after replacing the tweeter:
    [​IMG]
     
  6. santodx5

    santodx5 New Member

    Halo ToTo Man,

    I tried to private message you but your inbox is full.

    I found this thread about JR150, I hope you can help me. I just got a pair of JR150 from ebay.

    Here is what the description about the product:

    RARE, FAR SUPERIOR MODEL TO JR149. 8 OHMS. MISSING GRILLES. AUDAX TREBLE UNITS ARE IN EXCELLENT CONDITION BUT BASS SURROUNDS SHOULD BE REPLACED.

    These are our conversation about the product:

    Halo, what do you mean bass driver is tired? No sound? Can you be more specific? is it only in 1 of the speaker or both of them?

    I MEAN THE RUBBER SURROUNDS ARE TIRED AND NEED REPLACING. THE SOUND IS NOT PURE AT LOW VOLUME.

    I MEAN THAT THE RUBBER SURROUNDING THE CONES HAS LOST SOME ELASTICITY SO THAT THERE IS SOME RUBBING THAT IS EVIDENT AT LOW VOLUMES. "

    Did I buy unrepairable unit? You mention in the thread that the surround and cone is one unit. Does it means I cant replace it? Hows your repair going? Who told you the manaco will be a good replacement for the Audax? I may need to repair mine I hope you can help me with the information I need.

    Thank you
     
  7. PigletsDad

    PigletsDad pfm Member

    These will be taken at different angles, to show directional effects.

    Rising one will be straight on, and the other two probably at say 30 degrees and 60 degrees.

    Probably means you don't want them pointing absolutely straight at you, but instead listen a bit off axis.

    This is normal for a 1inch tweeter - at 20kHz it is nearly two wavelengths across, so starts give a narrow beam. But I haven't been able to hear even 15KHz for 30 years, so it doesn't matter much.
     
  8. Tony L

    Tony L Administrator

    To my ears JR149s sound a lot better firing wide of the listening seat rather than at the listener. I sit very close, so mine are toed-in, but not by very much. If I was listening further away I doubt I'd toe them in at all. This is actually born out by measurements both in the original Gramophone review and ones I've done myself.
     
  9. davidsrsb

    davidsrsb pfm Member

    Looking again at this speaker, the tweeter is a long way from the mid-bass units. Vertical combing must be an issue, the JR149 drivers are much closer. It would have been better as a MTM instead of TMM
     
  10. ToTo Man

    ToTo Man the band not the dog

    I'm sorry I'm not an expert on these loudspeakers so I can't comment on the condition of your bass units. They might be repairable, it depends on if you can find a good technician to do the repair, and at what price. I have not installed the Monacor units yet, but I'll let you know when I make progress with this.
     
  11. santodx5

    santodx5 New Member

    Can you pm me your email so we can communicate better in the future bout this? I have technician ready to fix it
     
  12. ToTo Man

    ToTo Man the band not the dog

    All of the measurements I've posted on this thread have been with the JR150s placed on Atacama SE12 stands and with my mic at its usual height of 104cm. This combination places the tweeters quite a bit lower than the mic.

    So today I replaced the stands with Atacama SE24 which places the tweeter at exactly the same height as the mic, and I repeated the farfield measurement on my fully original and functional 'Reference' pair of JR150s to see how the mid/treble balance changes:

    [​IMG]

    I also did a farfield measurement with the tweeter pointed straight ahead instead of at the mic, plus a nearfield measurement
    with the tweeter pointed directly at the mic:

    [​IMG]
     
  13. Richard Williams

    Richard Williams New Member

    Hi everyone, is there any update on how the Monacor bass units performed in terms of your impression as oppose to how they measure?

    It’s my dads 60th soon and I have bought him some JR150’s that I’m restoring (making new wooden tops/bottoms and reforming). Sadly although I didn’t notice the first time I plugged them in, with another CD it has become apparent that I have the dreaded scraping type sound from one driver. :( Subjectively the tweeters seem fine, and the overall balance is fine fortunately.
     
  14. Tony L

    Tony L Administrator

    Have you tried rotating the driver? May well be cone-sag.
     
  15. Richard Williams

    Richard Williams New Member

    I have rotated the driver and it’s the same so far 24hrs later, I will double check though with the same source material later.

    I do find if I apply light pressure with my finger to the side of the cone that you think would deflect it to counter any sag that the noise goes away. If I do the same on the opposite side the noise is still present.

    I have ordered the Monacor units (this birthday present is adding up my £££’s!) that I will try for now, and I will see what I can do to repair/revive the Audax units later on. Maybe I’ll make a baffle to hold them up to wait for the sag to drop out!
     
  16. Tony L

    Tony L Administrator

    It sounds like it has sagged. Chances are if you are patient it will return to where it should be in time!
     
    Richard Williams likes this.
  17. Arkless Electronics

    Arkless Electronics Trade: Arkless

    Surprised to hear that they didn't use B110's like the 149... yer learn something every day :)
     
  18. Tony L

    Tony L Administrator

    The MkII JR149, which are allegedly very good (I’ve never heard a pair), used Focal drivers IIRC. Hard to find a good working pair as not many were sold and the drivers seem to have more issues with age than the Kefs.
     
    Arkless Electronics likes this.
  19. ToTo Man

    ToTo Man the band not the dog

    Admittedly only a small sample, but I've got three pairs of JR149 mk2's and none of the six Focal bass drivers exhibit any problems and they all match very closely sonically, so 0% failure rate. The Audax bass drivers used in the JR150 are another matter, they do not seem to age well, especially if they've had a hard life. I have two pairs of JR150's, on one pair all four Audax bass drivers are fine but other pair two of the four drivers make a "clacking" sound when driven to moderate levels. I bought three used replacement drivers on eBay and two of these also make a "clacking" sound, so a 36% failure rate. I'm not certain what causes the problem but I suspect it's due to the surround losing its stiffness/tension and no longer being able to fully support the cone's movement.
     
  20. Tony L

    Tony L Administrator

    That’s interesting and good to know regarding the 149 MkII. I’d be tempted to try them now if a near mint pair show up.
     

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