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  1. #1

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    Default SDA Driver Seals: Original Foam vs. Mortite vs. Armaflex Foam

    Introduction

    Armacell Armaflex pipe insulation tape was compared to original SDA foam seals and Mortite seals in three pairs of SDA CRS+ loudspeakers. Armaflex was compared to Mortite in SDA SRS 1.2TL's and SDA SRS's. Armaflex is composed of 1/8th inch thick by 2" wide elastomeric synthetic foam rubber. All SDA loudspeakers tested have tweeters, drivers and passive radiators secured with steel rings.


    Figure 1. Mortite, original SDA foam seals and Armaflex pipe insulation tape.


    Figure 2. Original SDA foam rubber gaskets that were replaced with Mortite. I usually keep original parts...just in case.

    Results varied among the three types of SDA's. In the CRS+'s, there was no audible or tactile difference between speakers equipped with Armaflex or Mortite. Both Mortite and Armaflex outperformed the original seals in the areas of overall clarity, detail, bass articulation and tactile sensation. There was no change in spatial information.

    Others have found the original seals/steel ring combination to sound superior to the Mortite/steel ring combination. Those reports can be read at these links:

    Mortite, Rings and Gaskets

    Jesse's Right About Mortite

    Based on results from the CRS+ trials, original seals were not evaluated in the SRS's and 1.2TL's. In the SRS's, Armaflex provided more overall clarity, detail, bass articulation and tactile sensation. There was no change in spatial information.

    In the 1.2TL's, Armaflex provided more overall clarity, detail, bass articulation, image weight and tactile sensation. There were improvements in spatial information ranging from subtle to substantial, depending on the recording.

    Installation Procedure

    I used a 1/2" wide chisel to scrape Mortite off the driver and passive radiator rims. For most of the tweeters, I could simply peel off the Mortite. I occasionally had to use a small flat blade screwdriver on some tweeters. If you decide to remove Mortite from your driver rims, take care not to hold the drivers by the magnet. You don't want to risk shifting the magnet assembly. I held my drivers by the basket spokes.


    Figure 3. Mortite came off easily with a nice sharp chisel.


    Figure 4. Mortited parts ready for stripping and application of Armaflex strips.

    Marks 1/2" apart were made on the Amaflex's backing at regular intervals. Ink and pencil marks did not easily adhere to Armaflex's yellow wax paper backing, therefore a fine point ink pen was used to punch holes and then the pen and straight edge (24" drafting T-square and 48" carpenter's level) were used to scribe cutting guide lines. The tweeters' silk domes were protected while face down by placing the tweeters on a roll of electrical tape.


    Figure 5. Completed Armaflex installation on CRS+ drivers, passive radiator and tweeter.

    Audio Evaluations - Methodology

    Listening evaluations were done with familiar, well-recorded CD's and SACD's. Detailed listening notes were taken and the placement and quality of sound images were marked on a chart. Measurements for frequency response, harmonic distortion and bass decay were taken with Dayton Audio OmniMic software running on a laptop computer. The OmniMic microphone was placed at the listening position at ear height. The home's central air conditioning units were turned off during listening and measurement sessions.

    The color coded lines on the harmonic distortion plots represent the following:

    Black - frequency response.
    Dark blue - sum of 2nd-5th harmonics.
    Red - 2nd harmonic.
    Purple - 3rd harmonic.
    Green - 4th harmonic.
    Light blue - 5th harmonic.

    You may find it easier to discern differences in the plots if you save them to your computer and flip through them. Reasonable targets for frequency response in residential music rooms are +/- 10 dB from 10 to 200 Hz and +/- 5 dB from 200 to 20 kHz.

    Audio Evaluations - SDA CRS+


    Figure 6. Two identical pairs of CRS+'s were evaluated in the home theater system.

    The teak finished CRS+'s evaluated in the home theater system have been extensively modified as described here:

    CRS+ (1989 Version) PCB, Xover and SDA Inductor Upgrade

    Driver and Passive Radiator Rings for the CRS+


    Figure 7. The SRS's were moved out of the room and each CRS+ was set up on a pair of Metal Technology TMT-30 30" stands.

    One pair of CRS+'s was marked with blue tape and designated the "control" pair. It had Mortite seals throughout the trials. The other pair was "variable" and had its seals changed from Mortite to original foam to Armaflex.

    I could discern no audible or tactile differences between the Mortited control CRS+ and the Mortited variable CRS+, although there were minor differences in the frequency response and harmonic distortion plots.


    Figure 8. Frequency response of control teak CRS+ pair with Mortite.


    Figure 9. Frequency response of variable teak CRS+ pair with Mortite.


    Figure 10. Harmonic distortion of control teak CRS+ pair with Mortite.


    Figure 11. Harmonic distortion of variable teak CRS+ pair with Mortite.

    Figures 12 through 15 show the frequency response and harmonic distortion plots for the variable teak CRS+'s with the original foam seals and with Armaflex seals. Installing the original seals resulted in diminished clarity and detail and blurred bass. For example, on Jakiem Joyner's "Stay with me tonight" track ("babySOUL" CD) The distinct locations, as well as the note articulations, of the electric bass and kick drum became blurred. The congas on the left became muted and their reverberant envelope was significantly diminished. The string overtones and decay of acoustic guitar notes at the center right were muted. The echoes of acoustic guitar notes coming from the left and right speaker were muted. Tactile sensation and image placement remained the same as with Mortite.

    Replacing the original seals with Armaflex restored the "life" to the sound. I could discern no audible or tactile difference between the control CRS+'s with Mortite and the variable CRS+'s with Armaflex.


    Figure 12. Frequency response of variable teak CRS+ pair with original foam seals.


    Figure 13. Frequency response of variable teak CRS+ pair with Armaflex seals.


    Figure 14. Harmonic distortion of variable teak CRS+ pair with original seals.


    Figure 15. Harmonic distortion of variable teak CRS+ pair with Armaflex seals.

    Audio Evaluations - SDA SRS (Signature Reference System)

    The SRS's in my home theater system have bee extensively modified as described here:

    Further Improvements to the SRS...


    Figure 16. SRS's in home theater system.

    In the SRS's, the Armaflex seals provided more overall clarity, detail, bass articulation and tactile sensation. There was no change in spatial information.


    Figure 17. Frequency response of SRS's with Mortite seals.


    Figure 18. Frequency response of SRS's with Armaflex seals.


    Figure 19. Harmonic distortion of SRS's with Mortite seals.


    Figure 20. Harmonic distortion of SRS's with Armaflex seals.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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  2. #2

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    Default Armaflex Results With SDA SRS 1.2TL

    Audio Evaluations - SDA SRS (Signature Reference System) 1.2TL

    The SRS 1.2TL's in my two channel audio system have been extensively modified as described here:

    Improvements to the SDA SRS 1.2TL


    Figure 21. SDA SRS 1.2TL's in two channel audio system.

    In the 1.2TL's, Armaflex provided more overall clarity, detail, bass articulation, image weight and tactile sensation. There were improvements in spatial information ranging from subtle to substantial, depending on the recording.


    Figure 22. Frequency response of SDA SRS 1.2TL's with Mortite seals.


    Figure 23. Frequency response of SDA SRS 1.2TL's with Armaflex seals.


    Figure 24. Harmonic distortion of SDA SRS 1.2TL's with Mortite seals.


    Figure 25. Harmonic distortion of SDA SRS 1.2TL's with Armaflex seals.

    One of the better examples of improvements in spatial rendering is shown in figures 26 and 27. The sound stage charts show image placements for the primary instruments and the first four electric piano notes with Mortite and with Armaflex seals (the song is "blue" from Boney James' "Backbone").


    Figure 26. SDA SRS 1.2TL image placement example with Mortite seals.


    Figure 27. Such Good Sound! SDA SRS 1.2TL image placement example with Armaflex seals.

    The placement of note 2 in figure 27 is five feet in front of the speaker plane and just behind the left rear corner of the chair on the right in figure 21.

    Summary of Results



    Cabinet Pressure Testing

    To test for air-tightness, the passive radiators of each speaker was pushed in and the time counted for the mid-woofers to come to rest. The CRS+'s took 2 seconds whether the seal was original foam, Mortite or Armaflex. The SRS's and 1.2TL's took 3 seconds with either Mortite or Armaflex. An SDA SRS 2.3TL owner reported a float-down time of 5 seconds: Link.

    Associated Equipment

    A list of electronics used in the home theater and two channel systems can be found here.

    A list of electronics used in the office system can be found here.

    Acknowledgments

    Thanks to Nooshinjohn for recommending Armaflex. Thanks to the Ringmaster (TOOLFORLIFEFAN) for the wonderful steel rings.

    Parting Shot

    Question: Why are you always doing stuff to your speakers?
    Answer: Why are you always buying shoes and handbags you don't need?




    ------------------------------------------------------------------------------------------
    Did you really answer like that or did you just bite your tongue and think it?

    I actually said it. It was the mildest of three responses that came to mind.~DK
    Last edited by Kenneth Swauger; 08-20-2011 at 07:36 AM.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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  3. #3

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    I tip my hat to you sir.


    Thanks for the excellent review. Can I surmise from this that Armacell gets the nod over mortite for most situations? Which material did you find easier to work with?
    Last edited by nooshinjohn; 08-19-2011 at 01:38 AM.
    HT Setup... Pioneer Elite SC-37, Polk Audio SDA-SRS 1.2TL's , Oppo BDP 93
    Two Channel... Carver Statement 450~1 Vacuum Tube Monoblocks, Dodd Mid-line Tube Linestage with Psvane 12Ax7 tubes, Pioneer Pdd 9Mk II SACD Player, Yamaha PX-3 Turntable with Sumiko BPS EvoIII, Polk Audio SDA-SRS 1.2TLs.


    "The problems we face today exist because the people who work for a living are outnumbered by those who vote for a living." Brad Shurett

  4. #4

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    Buy stock in Armaflex tomorrow as sales will be up.
    '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 turd by the clean end."

  5. #5

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    Holy $h!t.

    I got nothin'.
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.

  6. #6

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    Very impressive -
    Pioneer Elite SC-35, Polk RTA (Real Time Array) 12's,
    Polk Monitor 40 surrounds, Polk CSiA4 Center,
    Polk PSW125, Sharp LC-46D62U,
    Panasonic DMP-BD85, Harmony One,
    iMac streaming an Apple TVII, or Squeezebox Touch
    Bedroom Rig~Sony STRDG-920, Polk Monitor 60 fronts, Polk RM6750 Satellites and Sub, Panasonic DMP-BD85
    Rabbit Hole Rig~Yamaha CA1010, Yamaha CT1010, Polk SDA 2A's, Teac A1500 R2R

  7. #7

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    Quote Originally Posted by nooshinjohn View Post
    Can I surmise from this that Armacell gets the nod over mortite for most situations?
    Armacell gets the nod over Mortite for ringed SDA's. Prior to installing rings in my SDA's, Mortite was far superior.

    I suspect that for larger ringed SDA's, the ring/Mortite combination causes overdamping.

    Quote Originally Posted by nooshinjohn View Post
    Which material did you find easier to work with?
    Amacell is just peel, cut and stick. Mortite is peel, and press and press and press and press. Armacell is much easier on your fingers. Armacell is also much easier to work with when it comes to removing drivers. Mortite didn't stick to the MDF cabinets of my 1.2TL's and SRS's. It did stick to the crackly, crumbly particle board cabinets of my CRS+'s.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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  8. #8

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    Thumbs up

    Nice review! I also applied it to the crossover plates including underneath the large inductor. There is a definite improvement in sound quality. +1 on using Armacell.

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    Wonderful job Sir, I tip my cap to you.

    I have had Amacell in my SDA2's for years. Never liked the idea of mortite and could not get the original gasket material, So Amacell was the closest thing I could find.

    For those that have not used Amacell before the only thing I would suggest is to make sure the backs of the Drivers are as clean as they can be. As Amacell is peel and stick it prefers an absolutely clean surface. Alcohol wipes or Rubbing alcohol with cotton balls did the best job.
    Quote Originally Posted by Timothy Smith View Post
    WOW!

    That's like working your way through Katie Perry in order to get to Rosie O'Donnell.

  10. #10

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    Quote Originally Posted by michaeljhsda2 View Post
    Nice review! I also applied it to the crossover plates including underneath the large inductor. There is a definite improvement in sound quality. +1 on using Armacell.
    The original foam seals around the crossover openings in my 1.2TL's were in good shape, but I replaced them this morning to see if there would be any sonic or air-tightness improvement. There wasn't. I didn't discern any difference in sound. When I did the passive push test, I still had a float down time of 3 seconds.

    I might have heard a difference or improvement if I didn't already have some vibration abatement applied (Dynamat Xtreme, double layer braced crossover circuit board, and tied-down and glued-down components.

    I am going to replace the crossover plate seals in my SRS's this evening.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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  11. #11
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    As always, DK, you have provided a well written, well documented experiment into how we can improve our music systems. Thank you very much!
    For several years I have used a liquid ceramic coating paint as a damping compound. I've coated tonearms with it and found very good response. It is a blend of magnesium, aluminum, muscovite, mica, barium and titanium and is called flexible borosilicate ceramic. It used to be sold by Michael Percy under the name "Acoustical Magic".
    I wonder how it would compare?
    Also, have you ever considered replacing the internal material with virgin long hair wool? I can remember Bud Fried recommending it? Uncombed, right off the sheep and into the speaker. Extremely random and much less "tuned" than the synthetic stuff.
    Just a thought...
    Cheers, Ken

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    Quote Originally Posted by Kenneth Swauger View Post
    For several years I have used a liquid ceramic coating paint as a damping compound. I've coated tonearms with it and found very good response. It is a blend of magnesium, aluminum, muscovite, mica, barium and titanium and is called flexible borosilicate ceramic. It used to be sold by Michael Percy under the name "Acoustical Magic". I wonder how it would compare?
    Are you suggesting this for basket damping or for coating the driver rim as a sealing gasket or used for both?

    Is Michael Percy still in business? If so, is he still a one man operation? I ordered some parts from him years ago (around 2001) and it took a day less than forever to receive them. Nice guy however...if you can catch him.

    Quote Originally Posted by Kenneth Swauger View Post
    Also, have you ever considered replacing the internal material with virgin long hair wool? I can remember Bud Fried recommending it? Uncombed, right off the sheep and into the speaker. Extremely random and much less "tuned" than the synthetic stuff.
    Thanks for the tip. I hadn't heard of this but it makes sense. I'll look into it.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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    I would consider it for the inside walls of the enclosure and baskets and tweeter front plates. I don't believe it will work as a gasket. The idea is that the thick paint contains millions of microscopic ceramic particles that are held in suspension. The compound never really "dries" this combined with the flexible texture of the compound converts sound energy to small amounts of heat. The original stuff is probably no longer available, but two products called: Tempcoat and Acoustic-Coat #150 might be similar. There are references to it being used by people who build recording studios.
    When I first got the Acoustic Magic paint, I took a 10" circular saw blade and hung it by a string. With a heavy screw driver I hit it and made it "ring like a bell", then I coated half of the blade, both sides, with the paint and let it dry. When I struck the blade it was dead, real dead, like it was made from lead instead of hardened steel.
    Probably a person could get fairly inventive and take normal Latex paint and add very finely ground, powdered silicates to make a similar product.
    Have fun...!
    ps I'd be willing to provide a small sample of the original stuff if someone wanted to experiment.
    Last edited by Kenneth Swauger; 08-19-2011 at 03:18 PM.

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    Great write up, and impressive data!

    I just received Larry's rings for my fathers 1.2TL's so it looks like I will be experimenting with Amacell this time around.

    Thank you DK for the extensive research and results.

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    Quote Originally Posted by Kenneth Swauger View Post
    ...ps I'd be willing to provide a small sample of the original stuff if someone wanted to experiment.

    I am up for that. I still need to do the XO's on my 2.3TL's, and would be happy to try this on the baskets.
    HT Setup... Pioneer Elite SC-37, Polk Audio SDA-SRS 1.2TL's , Oppo BDP 93
    Two Channel... Carver Statement 450~1 Vacuum Tube Monoblocks, Dodd Mid-line Tube Linestage with Psvane 12Ax7 tubes, Pioneer Pdd 9Mk II SACD Player, Yamaha PX-3 Turntable with Sumiko BPS EvoIII, Polk Audio SDA-SRS 1.2TLs.


    "The problems we face today exist because the people who work for a living are outnumbered by those who vote for a living." Brad Shurett

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    Quote Originally Posted by nooshinjohn View Post
    I am up for that. I still need to do the XO's on my 2.3TL's, and would be happy to try this on the baskets.
    I would be interested in how this compares to Dynamat Xtreme on driver baskets.

    Quote Originally Posted by Kenneth Swauger View Post
    I would consider it for the inside walls of the enclosure and baskets and tweeter front plates. I don't believe it will work as a gasket.
    That's a great suggestion. I hadn't considered treating my tweeter plates. However, I did notice an improvement after installing Larry's tweeter brackets. I am going to submit an inquiry to Polk's engineering department asking if there would be any problems with coating the front (or rear) of the tweeter plates with a sound absorbing paint.

    I thought about applying Dynamat to the rear of the tweeter plates, but Dynamat is too thick.

    Now that I'm thinking more about it, I should have made Armaflex gaskets to cover the entire rear of the tweeter plate just as the original gaskets did. I can use one of the original gaskets as a template.

    Quote Originally Posted by Kenneth Swauger View Post
    The idea is that the thick paint contains millions of microscopic ceramic particles that are held in suspension. The compound never really "dries" this combined with the flexible texture of the compound converts sound energy to small amounts of heat.
    Since Acoustic Magic Paint never completely dries, how easy would it be to remove from driver baskets?

    Quote Originally Posted by Kenneth Swauger View Post
    The original stuff is probably no longer available, but two products called: Tempcoat and Acoustic-Coat #150 might be similar. There are references to it being used by people who build recording studios.
    Acousti-Coat #150 seems to be the closest product to Acoustic Magic Paint. I could not find AMP available anywhere.

    Quote Originally Posted by Kenneth Swauger View Post
    I'd be willing to provide a small sample of the original stuff if someone wanted to experiment.
    How big is a small sample?
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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    Quote Originally Posted by DarqueKnight View Post
    Now that I'm thinking more about it, I should have made Armaflex gaskets to cover the entire rear of the tweeter plate just as the original gaskets did. I can use one of the original gaskets as a template.
    I had to do this because one of the tweeter gaskets was missing. It works just fine but I like the original gasket better.

  18. #18
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    The AMP looks is a flat white in color with a sort of "sparkle" finish. In fact when I did my Maplenoll tone arm I dipped it in the paint so it would coat inside and out and called the arm "frosty the tonearm". I've never tried to remove it, so I can't speak about how easy it might be. I don't believe any of the minerals held in suspension would cause a problem with any magnetic fields, tweeters etc. I wonder how easy it is to find powdered muskovite, comrade?
    Let me see how much of the stuff is left, I think it's on a shelf near the box of tubes?
    Michael P might still have some?

  19. #19

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    Quote Originally Posted by Kenneth Swauger View Post
    Let me see how much of the stuff is left, I think it's on a shelf near the box of tubes? Michael P might still have some?
    I'll check Michael P's current catalog.

    Quote Originally Posted by DarqueKnight View Post
    Now that I'm thinking more about it, I should have made Armaflex gaskets to cover the entire rear of the tweeter plate just as the original gaskets did. I can use one of the original gaskets as a template.
    Quote Originally Posted by michaeljhsda2 View Post
    I had to do this because one of the tweeter gaskets was missing. It works just fine but I like the original gasket better.
    The homemade gaskets work very well.

    I made four full-size gaskets and installed them in the right side 1.2TL. I did not remove the prior rim-only gaskets since they were difficult to remove and even a double layer of the Armaflex's super soft foam compresses easily.

    The right side sounded noticeably louder and I heard more overtones and weight on guitar and piano notes...but I thought it was just my mind playing tricks on me...you know, just another manifestation of placebo effect and wishful thinking. I didn't want to believe that putting an extra wee bit of foam behind tiny little tweeters would make an audible difference. The OmniMic's microphone was consulted since it is totally objective (unlike human ears) and it is immune to audiophile delusions.

    Frequency response and harmonic distortion plots for the SDA 1.2TL with rim-only and with rim-only plus full-size Armaflex tweeter gaskets are shown below.

    The color coded lines on the harmonic distortion plots represent the following:

    Black - frequency response.
    Dark blue - sum of 2nd-5th harmonics.
    Red - 2nd harmonic.
    Purple - 3rd harmonic.
    Green - 4th harmonic.
    Light blue - 5th harmonic.

    It is easier to discern differences in the plots if you save them to your computer and flip through them. Reasonable targets for frequency response in residential music rooms are +/- 10 dB from 10 to 200 Hz and +/- 5 dB from 200 to 20 kHz.


    Figure 28. Frequency response of SDA SRS 1.2TL's with Armaflex rim-only tweeter seals.


    Figure 29. Frequency response of SDA SRS 1.2TL's with Armaflex rim-only plus full-size tweeter seals.

    Figure 29 shows improved (smoother, flatter) response in the 2 kHz to 15 kHz region, with high frequencies beginning to roll off at 15 kHz rather than the previous 13 kHz.


    Figure 30. Harmonic distortion of SDA SRS 1.2TL's with Armaflex rim-only tweeter seals.


    Figure 31. Harmonic distortion of SDA SRS 1.2TL's with Armaflex rim-only plus full-size tweeter seals.

    Figure 30 shows a small decrease in overall harmonic distortion (dark blue line) with moderate decreases in some distortion products at certain frequencies.

    I have 14 more tweeter gaskets to cut.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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    Thanks for all of this DK. Glad I already bought Armacell. And I know I've been very pleased with the results in my CRS+s. Guess I should do the rest of my speakers next.
    Are you part of the dirty digital peasants or a member of the great Analog Master Race?

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    Thanks great info as usual. You are a fantastic asset to this forum.
    engtaz

    I love how music can brighten up a bad day.

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    Default As usual great work DK!

    Looks like I've got another project for my 1.2TL's :tongue:

    Great write up too! For those of us who have just enough knowledge to be dangerous you always provide a wealth of information with your projects/write-ups. My speaks are already leagues better than when I bought them, and I'm guessing I haven't reached the limits yet!

    I plan to remove the mortite and install the armaflex when the Solen Inductors arrive, which should be next week.

    Can't wait
    "Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills, polyswitches removed, Lg Solen inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR BP's, upgraded IC Cable, Black Hole Damping Sheet strips installed on back wall behind MW's & Tweeters, interior of cabinets sealed, AI-1 interface with 1000VA A-L transformer

  23. #23

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    Quote Originally Posted by drumminman View Post
    I plan to remove the mortite and install the armaflex when the Solen Inductors arrive, which should be next week.
    Do you have or are you planning to install retaining rings for your drivers? If you don't have or are not planning to get rings, you may want to compare Mortite and Armaflex. Keep in mind that, if you are going to compare Mortite and Armaflex, Mortite can easily be scraped off. Armaflex disintegrates upon removal leaving a sticky residue (along with reinforcing fibers) that must be removed with mineral spirits.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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    Don't have the rings but I did install 8-32 Hurricane nuts, which should have a similar effect to the rings, re: it allows enough torqueing to firmly fix the drivers to the front baffle. I'm guessing I'll hear a similiar effect with the armaflex.

    Correction: I meant 2.3TL's.
    "Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills, polyswitches removed, Lg Solen inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR BP's, upgraded IC Cable, Black Hole Damping Sheet strips installed on back wall behind MW's & Tweeters, interior of cabinets sealed, AI-1 interface with 1000VA A-L transformer

  25. #25

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    Default SDA SRS's and SDA CRS+'s with Full-Size Armacell Gaskets

    Frequency response and harmonic distortion plots for the SDA SRS and SDA CRS+ with rim-only and with full-size Armaflex tweeter gaskets are shown below.

    The color coded lines on the harmonic distortion plots represent the following:

    Black - frequency response.
    Dark blue - sum of 2nd-5th harmonics.
    Red - 2nd harmonic.
    Purple - 3rd harmonic.
    Green - 4th harmonic.
    Light blue - 5th harmonic.

    It is easier to discern differences in the plots if you save them to your computer and flip through them.

    SDA SRS


    Figure 32. Frequency response of SRS's with Armaflex rim-only tweeter seals.


    Figure 33. Frequency response of SRS's with Armaflex full-size tweeter seals.


    Figure 34. Harmonic distortion of SRS's with Armaflex rim-only tweeter seals.


    Figure 35. Harmonic distortion of SRS's with Armaflex full-size tweeter seals.

    Similar to results with the SDA SRS 1.2TL's, the SDA SRS's with a full-size Armaflex tweeter gasket displayed a smoother response from 2 to 15 kHz without the steep drop off at 13 kHz that occurred with the rim-only Armaflex gasket. Harmonic distortion was also slightly lower with the Armacell full-size gasket.

    SDA CRS+

    These plots are from the "variable" CRS+ pair. Figure 39 shows that putting a full-size Armaflex gasket behind the tweeters significantly improved response in the 2 kHz to 20 kHz region. Harmonic distortion (figure 43) was slightly improved with the full-size Armaflex tweeter gasket. There were moderate improvements in clarity and detail and small improvements in image weight and tactile sensation with the full-size Armaflex tweeter gasket.


    Figure 36. Frequency response of variable CRS+ pair with original foam seals.


    Figure 37. Frequency response of variable CRS+ pair with Mortite seals.


    Figure 38. Frequency response of variable CRS+ pair with Armaflex seals (Armaflex around tweeter rims only).


    Figure 39. Frequency response of variable CRS+ pair with Armaflex seals (full-size Armaflex tweeter seals).



    Figure 40. Harmonic distortion of variable CRS+ pair with original foam seals.


    Figure 41. Harmonic distortion of variable CRS+ pair with Mortite seals.


    Figure 42. Harmonic distortion of variable CRS+ pair with Armaflex seals (Armaflex around tweeter rims only).


    Figure 43. Harmonic distortion of variable CRS+ pair with Armaflex seals (full-size Armaflex tweeter seals).




    Figure 44. Armaflex tweeter gaskets: Clockwise from top left - on RD0198 prior to installation, original foam gasket,
    on RD0194 after installation showing how much the Armaflex compresses, Armaflex gasket parts, Armaflex parts fitted
    together.


    SDA tweeters are 3-3/8" wide and Armaflex tape is 2" wide, hence the split gaskets. I used the original foam gasket to make a cardboard template (without the screw holes). I traced around the template with a fine point Sharpie. The Sharpie didn't write very well on the Armaflex's wax paper backing, but it wrote well enough to guide my scissors.

    Armaflex does come in sheets, but it is difficult to find. In the future, when I'm more dedicated to audio, I'll track down some 1/8" sheet Armaflex to have on hand if I need to replace a tweeter gasket.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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    Excellent information - inspirational work.

    I must ask - are you using wall braces for your 1.2TL's, and if not, are you plugging that hole with anything?

    Burson HA-160D > Adcom GFA-5802 > Polk SDA-SRS 1.2tl w/ Mye Sound Spikes, Mills/Sonicap XO, Larry's Rings, Dynamat Extreme, Cardas CCGR Binding Posts and Jumpers, Custom 10ga interconnect, Custom Gaskets, RDO-198

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    No braces or spikes. The speakers rest on the original feet which are covered with Teflon caps. I am always moving the speakers around due to tweaking, so bolting them to the wall or spiking them would be inconvenient.

    The hole is plugged with the original bolt.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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    Great work. I think this highlights a basic problem with the vintage Polk tweeters and their replacements - The flimsy plastic mounting bracket. The full armaflex gaskets appear to be dampening the flimsy mounting plates.

    When I removed my tweeters, to install RDO-194's, I noticed that the original gaskets had shrunk and were not keeping the cabinets airtight, so I made an 1/8" wide perimeter gasket out of armaflex. Even a gasket this narrow causes the mounting bracket to flex upward, on the long ends when tightened. Tapping on the bracket, with the plastic handle of a screw driver, revealed that it is really live and resonant, so I placed three 3/8" diameter balls of mortite under each end of the bracket, for a total of six, in the hollow areas underneath the bracket. With the mortite dampeners, the brackets are now very dead when tapped. The dampened tweeters seem much smoother sounding, especially at louder volume.

    This brings up a couple of questions: the plastic bracket, on the RDO-194, appears that it could be removed from tweeter, it you took the screws out, unlike the original SL series units, which had the wire leads siliconed to the bracket. Has anyone tried to remove the bracket from a RDO-194/198? Has anyone pondered replacing the plastic brackets with something more substantial, maybe machined from aluminum or steel?

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    Quote Originally Posted by qwertycus View Post
    Has anyone tried to remove the bracket from a RDO-194/198?
    The plastic brackets of the RD0194/198, and the SL3000, can be removed.

    Quote Originally Posted by qwertycus View Post
    Has anyone pondered replacing the plastic brackets with something more substantial, maybe machined from aluminum or steel?
    This would be a good question for Polk's engineering department. Sometimes a fine line must be walked between canceling detrimental resonances and over damping.

    Does anyone know of any dynamic tweeter designs that use metal brackets/faceplates? I can't think of any.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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    Quote Originally Posted by qwertycus View Post
    replacing the plastic brackets with something more substantial, maybe machined from aluminum or steel?
    Looks like a job for SUPERLARRY! (aka Toolforlifefan):tongue:


    Put me down for six in natural brushed aluminum.
    HT Setup... Pioneer Elite SC-37, Polk Audio SDA-SRS 1.2TL's , Oppo BDP 93
    Two Channel... Carver Statement 450~1 Vacuum Tube Monoblocks, Dodd Mid-line Tube Linestage with Psvane 12Ax7 tubes, Pioneer Pdd 9Mk II SACD Player, Yamaha PX-3 Turntable with Sumiko BPS EvoIII, Polk Audio SDA-SRS 1.2TLs.


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