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Thread: JR 149 Monacor 135TC @15 ohm vs Kef SP1033 B110

  1. #1
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Default JR 149 Monacor 135TC @15 ohm vs Kef SP1033 B110

    IMG_0724.jpg
    I am presently comparing JR149 - one with a Monacor 135TC and another with original B110 a SP1033 type.

    The Monacor has been wired for 15 ohm using both of its available voice coils.

    Firstly this is a very easy conversion, the only requirement being to use 4 of the self tapper type screws rather than the threaded types. With JR149 two of the screws
    are the threaded and two are the self tappers. Speaker drivers fit perfectly. Soldering is easy, I just arranged a link for the two coils of the Monacor to be in series using insulated wire

    Now to the sound: The Monacor 135 TC using both coils at 15 ohm has pretty well identical output to the 7.3 ohm Kef B110 SP1033 , you would be very hard pressed to say
    one speaker was louder than the other. Which is the better speaker ?. The Monacor shows itself to be the superior speaker... but its close. You seem to get more
    information about the music from the Monacor, The deep bass ( not that 149's do very low bass ) is pretty well identical.

    So the Monacor 135 TC wired for 15 ohms is more than a viable alternative for the Kef B110 in a JR149, it is highly recommended ..as an improvement.

  2. #2
    Join Date: Feb 2008

    Location: Middlesex, UK

    Posts: 4,481
    I'm Alex.

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    Thanks, a very useful bit of info. There was a guy on ebay selling and recommending these units for the 149.
    Spendorman

  3. #3
    Join Date: Feb 2008

    Location: Middlesex, UK

    Posts: 4,481
    I'm Alex.

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    Henrys-Superstore, wonder if this is the old Henry's Radio that used to be in London. Just read listing fully, it is!

    https://www.ebay.co.uk/itm/MONACOR-S...pid=1573962085
    Spendorman

  4. #4
    Join Date: Feb 2015

    Location: Glasgow

    Posts: 109
    I'm Richard.

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    This is uncanny!... This morning I fetched from my cupboard, amongst other drivers, a pair of KEF B110 SP1003 and four Monacor SP-135TC with voice coils wired together to give 16 ohms.

    I bought the Monacors several years ago to replace the four Audax HD13 drivers in one of my pairs of JR150 but have not yet attempted to fit them as apparently there is some jiggery pokery required with standoffs to fit the driver proud of the baffle as its basket is fractionally larger than that of the Audax HB13.

    I took measurements of all drivers this afternoon. The measurements were done in free-space with no baffle or enclosure so are of limited use, but may be of some value nevertheless. I took them at a distance of 1m and off-axis by about 0.4m (it's been a long-time since I did geometry, is that an 18 degree angle?). I measured off-axis because I was measuring tweeters as well and those exhibited a sharp dip at 6kHz when measured on-axis.

    I'm surprised you don't notice a difference in volume level between the B110 SP1003 and 16 ohm Monacor SP135TC because, according to my free space measurements, there's an efficiency difference between the two drivers that amounts to 3dB below 1kHz and 8dB above 1.5kHz?! I also understand that the JR149 has an "anti-quack" notch filter to tame the B110's response at the upper end of its operating range, which I suspect will produce sub-optimal results when used with the SP135TC unit. I'd be very interested to see measurements, if you have taken any? Also, may I ask why you decided to use the SP135TC in 16 ohm configuration in the JR149, wouldn't 8 ohm be more appropriate?









    Last edited by ToTo Man; 09-06-2019 at 10:43.
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  5. #5
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

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    Quote Originally Posted by ToTo Man View Post
    This is uncanny!... This morning I fetched from my cupboard, amongst other drivers, a pair of KEF B110 SP1003 and four Monacor SP-135TC with voice coils wired together to give 16 ohms.

    I bought the Monacors several years ago to replace the four Audax HD13 drivers in one of my pairs of JR150 but have not yet attempted to fit them as apparently there is some jiggery pokery required with standoffs to fit the driver proud of the baffle as its basket is fractionally larger than that of the Audax HB13.

    I took measurements of all drivers this afternoon. The measurements were done in free-space with no baffle or enclosure so are of limited use, but may be of some value nevertheless. I took them at a distance of 1m and off-axis by about 0.4m (it's been a long-time since I did trig so I'll leave it to someone else to calculate the angle from that! I measured off-axis because I was measuring tweeters as well and those exhibited a sharp dip at 6kHz when measured on-axis.

    I'm surprised you don't notice a difference in volume level between the B110 SP1003 and 16 ohm Monacor SP135TC because, according to my free space measurements, there's an efficiency difference between the two drivers that amounts to 3dB below 1kHz and 8dB above 1.5kHz?! I also understand that the JR149 has an "anti-quack" notch filter to tame the B110's response at the upper end of its operating range, which I suspect will produce sub-optimal results when used with the SP135TC unit. I'd be very interested to see measurements, if you have taken any? Also, may I ask why you decided to use the SP135TC in 16 ohm configuration in the JR149, wouldn't 8 ohm be more appropriate?









    The difference will be in free space vs mounted, suggesting the Monacor has better overall efficiency, particularly when in a cabinet, Its 15 ohms connection
    brings its higher initial efficiency into line with the B110 at 7.3 ohms. when mounted in the JR149 cabinet. Unfortunately I cannot supply measurements.
    I can say though when mounted in the JR149 cabinet at 15 ohms connection, there is to my hearing no channel balance issue. The Monacor sounding
    more life like and as music should be, than the B110. Your free space measurements back this up, showing the Monacor is much smoother.

    Regarding 15 ohms it appears I have stumbled on the ideal JR149 recipe. It suggests to me the switch to the B110 @8 ohms by Jim Rogers may have been one based
    on availability of 15 ohm drivers, that were perhaps being reserved or licensed to LS 3/5a production, so therefore unavailable for his production line.

    The crossover I am using in both JR149 speakers is the final production type using the squarish circuit board.

  6. #6
    Join Date: Feb 2015

    Location: Glasgow

    Posts: 109
    I'm Richard.

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    Quote Originally Posted by Light Dependant Resistor View Post
    The difference will be in free space vs mounted, suggesting the Monacor has better overall efficiency, particularly when in a cabinet, Its 15 ohms connection
    brings its higher initial efficiency into line with the B110 at 7.3 ohms. when mounted in the JR149 cabinet. Unfortunately I cannot supply measurements.
    I can say though when mounted in the JR149 cabinet at 15 ohms connection, there is to my hearing no channel balance issue. The Monacor sounding
    more life like and as music should be, than the B110. Your free space measurements back this up, showing the Monacor is much smoother.

    Regarding 15 ohms it appears I have stumbled on the ideal JR149 recipe. It suggests to me the switch to the B110 @8 ohms by Jim Rogers may have been one based
    on availability of 15 ohm drivers, that were perhaps being reserved or licensed to LS 3/5a production, so therefore unavailable for his production line.

    The crossover I am using in both JR149 speakers is the final production type using the squarish circuit board.
    I'm not sure where you sourced your crossovers from, but I am not aware of any JR149s that left the factory with this crossover version. There was however a chap on eBay selling a version of these boards, claiming it replicated Jim's final design. I bought a pair of these and, while my ears were initially fooled into thinking the more prominent midrange sound they produced was an 'improvement', I eventually realised it wasn't and reverted back to the original round crossovers. Years later when I was able to measure the acoustic differences between the two crossovers, it became evident that the square version was not designed properly, not least because it did not contain any baffle step correction to preserve the low frequencies! You can see the difference between the two designs in the following graphs.

    Original round crossovers:


    Square 'Type24' crossovers:
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  7. #7
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

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    Quote Originally Posted by ToTo Man View Post
    I'm not sure where you sourced your crossovers from, but I am not aware of any JR149s that left the factory with this crossover version. There was however a chap on eBay selling a version of these boards, claiming it replicated Jim's final design. I bought a pair of these and, while my ears were initially fooled into thinking the more prominent midrange sound they produced was an 'improvement', I eventually realised it wasn't and reverted back to the original round crossovers. Years later when I was able to measure the acoustic differences between the two crossovers, it became evident that the square version was not designed properly, not least because it did not contain any baffle step correction to preserve the low frequencies! You can see the difference between the two designs in the following graphs.

    Original round crossovers:


    Square 'Type24' crossovers:
    The Type 24 crossover was the last crossover for the JR149 released in 1991 as detailed here http://www.mcmullon.com/icollect/hi_.../jr_review.htm
    Whilst your after market crossover from ebay might measure that way, the Type 24 was supplied for a limited time - possibly months, as their final official crossover network.
    I have one of the serial numbers on mine, which is 6087

  8. #8
    Join Date: Jan 2008

    Location: Witney Oxon

    Posts: 893
    I'm Martyn.

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    All interesting stuff, but the crossovers will need some changes to accommodate the Monacor drivers.
    Doug Stirling, of Stirling Broadcast, told me about some of the changes to be made to a LS3/5a crossover
    when substituting Monacors for B110s.
    I’m aware the JR149 crossover isn’t as complicated as the ‘3/5a, so less change may well be required.
    Good to know, though, that people have been successful with this driver change.

  9. #9
    Join Date: Feb 2015

    Location: Glasgow

    Posts: 109
    I'm Richard.

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    Quote Originally Posted by Light Dependant Resistor View Post
    The Type 24 crossover was the last crossover for the JR149 released in 1991 as detailed here http://www.mcmullon.com/icollect/hi_.../jr_review.htm
    Whilst your after market crossover from ebay might measure that way, the Type 24 was supplied for a limited time - possibly months, as their final official crossover network.
    I have one of the serial numbers on mine, which is 6087
    It would be great if you could upload a pic of your final production crossover as I've never seen one before. The JR149 enthusiasts over on pfm may even be able to reverse engineer it and determine how it differs from the design of the more common round version.
    Main System: Mac Mini > Schiit Yggdrasil 2 OG > Yamaha A-S3000 > Celestion Ditton 66
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  10. #10
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

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    Quote Originally Posted by ToTo Man View Post
    It would be great if you could upload a pic of your final production crossover as I've never seen one before. The JR149 enthusiasts over on pfm may even be able to reverse engineer it and determine how it differs from the design of the more common round version.
    Here it is. I can draw a schematic for it, although difficult to exactly determine inductor values, but might be able to manually calculate.
    Attached Images Attached Images

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