M11T Mod Question

MrGeology
MrGeology Posts: 83
in Vintage Speakers
My friend picked up a pair of M11T's and asked me to go through them.
Already have all the Sonicaps and the crossover stuff to do the TL mod.
Have the RD0-198's and bezels from @xschop .
Hurricane nuts throughout (of course).

Picked up Sonic Barrier 3/4" 3-Layer to go behind the 6510's.

Question is what dimensions should the Sonic Barrier be cut to, and how much of the original Dacron should be removed to compensate for it?

Thanks.
"One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States
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Comments

  • Toolfan66
    Toolfan66 Posts: 17,221
    Don’t remove any Dacron, and between a 4” X 4” - 5” X 5” Square behind each driver is plenty. I don’t remember where cabinet bracing is in the 11T’s, so it may very a little for your application..
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  • Gardenstater
    Gardenstater Posts: 4,458
    edited March 23
    It needs to be cut into the shape of a 4 leafed clover and have an area of 25 sq. in. and align the petals of the shamrock with the windows of the Midwoofer.

    Ha. Just kidding. Sort of. I think experimentation is definitely warranted.

    The volume taken up by the foam underneath the vinyl layer would tend to offset the effect of the absorptive foam above, with respect to effective cabinet volume.
    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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  • joebass3
    joebass3 Posts: 283
    I used a 4x4 square behind the drivers in my Monitor 7's and 10's but opted for the 1-1/4" thick Sonic Barrier.
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  • Gardenstater
    Gardenstater Posts: 4,458
    edited March 24
    I used 6" x 6" BH5 (which is thicker than 3/4") in my 7Bs and there is definitely not any life sucked out of the music. Bass is very impactful still. Midrange vocal clarity was improved noticeably, as in hearing the vocalist take a breath etc.. I aligned it with the sides parallel to the cabinet but contemplated doing it 45deg to that.

    I didn't remove any dacron. BH5 is neutral in its effect upon effective cabinet volume because of the volume underneath the vinyl. I wouldn't remove any Dacron in your case either.

    Another factor, that doesn't exist in your case, is that BH5 has the panel vibration dampening base layer.

    "If" what Danny Richie says is true, namely that the floating vinyl layer with foam underneath it can mass load the driver cones which would introduce distortion potentially, then there would be very negative effects resulting in using too much of the stuff that has that vinyl layer.
    Post edited by Gardenstater on
    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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  • Gardenstater
    Gardenstater Posts: 4,458
    edited March 24
    The RTA 11t has very close to twice the internal enclosure volume of my 7Bs. Mr. Spock says 99.4% more. It also has a deeper enclosure at 14-3/8" vs. only 9-1/4".

    Any internal bracing would throw off Spock's calculation.
    Post edited by Gardenstater on
    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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  • F1nut
    F1nut Posts: 50,495
    A 3x3 or 4x4 inch square of the original BH5 is way more than enough behind a Polk mid-driver.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • MrGeology
    MrGeology Posts: 83
    Thanks everyone.
    Since we don't have BH5 will try going with ~ 5x5 squares of the 3/4 Sonic Barrier behind the drivers.
    With the dacron in there (the way it was originally) the Sonic Barrier will not be directly exposed to the drivers (dacron will cover the Sonic Barrier), which I am only guessing is fine as no one has addressed this issue.
    "One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
    -James K. Polk, 11th President of the United States
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  • bcwsrt
    bcwsrt Posts: 1,876
    That’s been discussed. Yes, the dacron goes back in its original place.

    If the Sonic Barrier is anywhere near as potent as BH5, 5x5 squares seems like a lot.

    Brian

    One-owner Polk Audio RTA 15TL speakers refreshed w/ Sonicap, Vishay/Mills and Cardas components by "pitdogg2," "xschop" billet tweeter plates and BH5 | Stereo REL Acoustics T/5x subwoofers w/ Bassline Blue cables | Rogue Audio Cronus Magnum III integrated tube amp | Technics SL-1210G turntable w/ Ortofon 2M Black LVB 250 MM cart | Sony CDP-508ESD CD player (as a transport) | LampizatOr Baltic 4 tube DAC | Nordost & DH Labs cables/interconnects | APC H15 Power Conditioner | GIK Acoustics room treatments | Degritter RCM
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  • Toolfan66
    Toolfan66 Posts: 17,221
    bcwsrt wrote: »
    That’s been discussed. Yes, the dacron goes back in its original place.

    If the Sonic Barrier is anywhere near as potent as BH5, 5x5 squares seems like a lot.

    Sonic Barrier is not like the original BH5, 5 x 5 squares will be fine IMO, I definitely wouldn't go above that..
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  • Toolfan66
    Toolfan66 Posts: 17,221
    MrGeology wrote: »
    Thanks everyone.
    Since we don't have BH5 will try going with ~ 5x5 squares of the 3/4 Sonic Barrier behind the drivers.
    With the dacron in there (the way it was originally) the Sonic Barrier will not be directly exposed to the drivers (dacron will cover the Sonic Barrier), which I am only guessing is fine as no one has addressed this issue.

    Correct, it will cover the SB, and no issues..
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  • MrGeology
    MrGeology Posts: 83
    bcwsrt wrote: »
    That’s been discussed.
    The issue I stated had not been discussed.

    Toolfan66 wrote: »
    Correct, it will cover the SB, and no issues..
    Until here.
    "One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
    -James K. Polk, 11th President of the United States
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