Phase Plug design for MW65xx

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  • Gardenstater
    Gardenstater Posts: 4,455
    edited February 27
    F1nut wrote: »
    skipshot12 wrote: »
    Has anyone done the phase plug mod on the sda srs? Thats a lot of drivers.
    Would like to hear a pair with that mod…

    Skip

    It was done on the CRS+ with less than favorable results.

    DK supplied some spare MW6511s for Rob to mod; the SDA drivers. They weren't listened to and Sensitivity Testing wasn't done on them to compare to the 6511s that were in his CRS+. If you read through the thread again you'll see that the suspensions were sagging by around 1/8" which would put the voice coils badly off center in the gap.

    This needs to be revisited with Sensitivity testing comparing the outputs of the phase plugged drivers with the non phase plugged ones, including the MW6510s which Rob supplied.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
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  • xschop
    xschop Posts: 5,000
    edited February 28
    Gardenstater wrote: »
    F1nut wrote: »
    skipshot12 wrote: »
    Has anyone done the phase plug mod on the sda srs? Thats a lot of drivers.
    Would like to hear a pair with that mod…

    Skip

    It was done on the CRS+ with less than favorable results.

    DK supplied some spare MW6511s for Rob to mod; the SDA drivers. They weren't listened to and Sensitivity Testing wasn't done on them to compare to the 6511s that were in his CRS+. If you read through the thread again you'll see that the suspensions were sagging by around 1/8" which would put the voice coils badly off center in the gap.

    This needs to be revisited with Sensitivity testing comparing the outputs of the phase plugged drivers with the non phase plugged ones, including the MW6510s which Rob supplied.

    His 6511 SDA drivers were defective IMO. Actually never opened up ANY set of MW's that looked like that before. How does that NOT affect BL and driver sensitivity?
    Don't take experimental gene therapies from known eugenicists.
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  • xschop
    xschop Posts: 5,000
    skipshot12 wrote: »
    Has anyone done the phase plug mod on the sda srs? Thats a lot of drivers.
    Would like to hear a pair with that mod…

    Skip

    My offer still stands to plug every driver from @ptrooper's the Monoliths
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  • xschop
    xschop Posts: 5,000
    Another 6511 saved from the scrap heap with a new 3.6 ohm coils and base plate ID clearance....

    rgojnrvru5ra.jpg
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  • Gardenstater
    Gardenstater Posts: 4,455
    Did it have the sagging suspension like DKs or was it too mangled to tell?
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • xschop
    xschop Posts: 5,000
    edited March 21
    It was sagging, but not that bad. I heated the spider with hair dryer, let set upside-down while cooling. I'll get another 6511 eventually and A-B the 6502's (better suspensions) in 8TL-SDA circuits.

    The JBL 3.6 ohm coils are perfect replacements for 6502's and 6511's.
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  • xschop
    xschop Posts: 5,000
    edited April 7
    Thought I'd post this here since it was a phase-plugged 6502 that developed a large crack in the surround and creased the paper cone. These were in may FIL's billet 5Jr's. Luckily he didn't blow the voice coil. I decided to experiment with a replacement carbon fiber cone since it already had the butyl surround glued to it.

    I simply chiseled off the old rubber surround and cut the old cone out leaving just enough of it attached to the coil and the electrical leads remained attached. Saves a TON of time and work. Then I cut out the carbon fiber cone center to 1.5" and glued it right to the base of the old cone. The glue I used is Superglue Fix-All and flowed all the interfaces nicely front and back of the CF cone.

    Will let set a few hours and glue surround to basket then test on the 5Bs...

    10oglc73h9ux.jpg
    dfp3f4h8g1vw.jpg
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  • pitdogg2
    pitdogg2 Posts: 25,411
    That surround looks twice as big as the old, is it or is that a photo misnomer?
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  • Gardenstater
    Gardenstater Posts: 4,455
    Do you have a microgram balance? Just wondering about how the weights compare and also of course stiffness if you have any idea.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • xschop
    xschop Posts: 5,000
    edited April 7
    Just meaured a CF surround and the fold-over is 0.50' wide on the CF, as compared to 0.40" wide on the factory. Th CF surround does feel a little more weighty however.

    No uG balance here, but interestingly the CF cone and heavier surround feel about same weight as old one I cut out, so the CF cone itself must be lighter?. The CF is MUCH stiffer than the factory paper cone and was very hard to cut with a new scalpel. It did not fray as that was my worry cutting it.
    Later, I plan on building a set of omnidirectional drivers using these CF cones, so was good practice working with them....

    eoh55yw88mh9.jpg
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  • xschop
    xschop Posts: 5,000
    edited April 7
    Bottom/center dry. Now have the surround glued and weighted down...

    ko7sv8yhyp7m.jpg
    Post edited by xschop on
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  • xschop
    xschop Posts: 5,000
    edited April 7
    Cleaned up edges and used a 10mm leather punch for the bolt head clearances...

    8kctetq4nrcc.jpg


    Ill do a comparo after dinner...
    It is the phase-plug thread ya know...

    m18cqtgw8a2b.jpg

    n1kgxj6bb4qs.jpg

    qgk6ahccgrfv.jpg



    Post edited by xschop on
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  • xschop
    xschop Posts: 5,000
    Loctite already set, so gave them the same wintergreen oil solution as I do the factory surrounds...

    v1xzk6my6qrd.jpg

    Sad Old Red up first...


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  • xschop
    xschop Posts: 5,000
    Mick, Sade, and Sting all passed the the test with flying colors.
    I wouldn't hesitate to do this repair again. The cone holds it shape at very high volume, zero distortion and hard to tell a difference between the plugged 6502 with damped paper cone.
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  • xschop
    xschop Posts: 5,000
    Pet Shop Boys midrange was crystal clear with high volume accompanying bass...

    https://youtu.be/wz4pQGxK25Y?si=x2P2f6nYeGwTJ7UC
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  • Gardenstater
    Gardenstater Posts: 4,455
    Nicely done!!
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • xschop
    xschop Posts: 5,000
    Definitely keepers. Here's the carbon Wuhans I used...I'll be ordering a few more.
    Time to go listen to the SDA's.

    https://www.ebay.com/itm/193941704625?var=494136088548
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  • Gardenstater
    Gardenstater Posts: 4,455
    Recent Danny Richie video where he describes the midwoofers @6:25:

    "We did an 8 ohm and a 16 ohm version and the 8 ohm version you see here in the NX Studio Monitor, and we went all out with the design on it; polymer chassis, lightweight paper cone, copper shorting rings in the motor structure, all copper coated motor structure, I mean we did everything on this thing, venting through the front, solid aluminum pole piece copper coated *, the works, and the result was one of the best sounding woofers there is on the market to this day."

    * I looked the driver up on his website and, yes he did mean solid aluminum phase plug attached to pole piece
    https://gr-research.com/product/m-165nq/

    https://www.youtube.com/watch?v=7h72KXd8Q3c
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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