The Tale Of 5 Tweeters - SDA Tweeter Replacement Guide

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Comments

  • DarqueKnightDarqueKnight Posts: 6,510
    edited August 2018
    mhardy6647 wrote: »
    Do you have any reference tweeters that are different than this cadre to test?

    I have tested several copies of each tweeter, including brand new copies of the RD0194 and RD0198, and the 5 kHz dip still appears.
    mhardy6647 wrote: »
    I wonder if 5-ish kHz dip is endemic to these tweeters or an artifact of the test.

    I wondered about that. Moving the microphone closer or farther away did not get rid of the 5 kHz dip. The FR plot below is of my SDA SRS 1.2TLs in the same room. There is a small dip in the response at 5 kHz, but nothing close to what is shown in the tweeter response plots.

    vu6tdoje77l1.jpg
    Figure 19. Room response of SDA SRS 1.2TLs in tweeter testing room.

    The SDA CRS+s in my office at work do show a dip at 3.5 kHz and at 5 kHz.

    pcq2hqv5px2x.jpg
    Figure 20. Room response of SDA CRS+s in office at work.

    I did a search on "tweeter dip at 5 kHz" and found that some speakers have a dip at 5 kHz to improve the smoothness and midrange "presence" of the speaker.

    @KennethSwauger would you ask Stu if these tweeters are supposed to have a dip at 5 kHz?
    "So hot it burns Mice!"~DK
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
    "Knowledge, without understanding, is a path to failure."~DK
    "Those who irrationally rail against something or someone that is no threat to them, actually desire (or desire to be like) the thing or person they are railing against."~DK
  • DarqueKnightDarqueKnight Posts: 6,510
    Near Field Measurements Redone - 5 kHz Dip Gone!

    After further study and experimentation, the previous near-field frequency response measurements were redone. The previous measurements were taken at a distance of 9 inches. The new measurements were taken at a distance of 2 inches, with the microphone pointing at the exact center of the tweeter dome.

    The following quote is taken from a white paper by Jeff Bagby, "How to Achieve Accurate In-Room Quasi-Anechoic Free-Field Frequency Response Measurements Down to 10 Hz":

    "To begin with we need to understand what a far-field response really is. To be in the far-field is not as far as you may think. You are effectively in the far-field when your microphone is at a distance that is 3-5 times the radiating diameter of the driver."

    Therefore, for a near field measurement for a 1" tweeter, the microphone should have been no further than 3 to 5 inches away. At the prior 9 inch microphone distance, room effects were coming into play.

    Also from Bagby, "...the usable upper limit of the near field response is defined as
    Fmax = 4311/ radiating diameter (in inches). Below this frequency the near-field response will be accurate and free of room and cabinet diffraction effects, above this frequency the near-field data is less reliable and less accurate."

    Another rule for near-field measurement is that the microphone needs to be spaced from the center of the driver approximately 0.10 times the effective radiating radius of the driver. In the case of a 1" tweeter, this distance would have been 1/20th (0.05"). This was impractical in my case due to reflections from the tripod holding the microphone. A distance of 2 inches from the center of the tweeter domes resulted in smooth response curves without any dips due to room effects.

    SDA Tweeter Frequency Response Measurements - Two Inch Distance

    brcju26nuqbb.jpg
    Figure 21. SL1000 frequency response.

    cp9se4gtvpus.jpg
    Figure 22. SL2000 frequency response.

    cei3g9y04ekk.jpg
    Figure 23. SL2500 frequency response.

    t9vs3zrtw649.jpg
    Figure 24. SL3000 frequency response.

    o67psath9xat.jpg
    Figure 25. RD0194 frequency response.

    tadaoplqydbf.jpg
    Figure 26. RD0198 frequency response.

    ms13ibtdu6cq.jpg
    Figure 27. Composite plot of all six tweeters. Black line: RD0194. Red line: RD0198. Light blue line: SL1000. Green line: SL2000. Purple line: SL2500. Dark blue line: SL3000.

    hmrgj4vm2yt3.jpg
    Figure 28. Comparison of RD0194 and SL2000 frequency response.

    newhd2c9c4oh.jpg
    Figure 29. Comparison of RD0194 and SL1000 frequency response.

    64eo8qhpqq27.jpg
    Figure 30. Comparison of RD0198 and SL2500 frequency response.

    2o46ozckl5q9.jpg
    Figure 31. Comparison of RD0198 and SL3000 frequency response.

    SDA Tweeter Harmonic Distortion Analysis - Two Inch Distance

    In order of least harmonic distortion to most, the tweeters are: RD0198, RD0194, SL3000, SL1000, SL2500, SL2000.

    The legend for the harmonic distortion plots is as follows:

    Black line at top - frequency response.
    Dark blue line second from top - summation of 2nd - 5th harmonics.
    Light blue line - 5th harmonic.
    Green line - 4th harmonic.
    Purple line - 3rd harmonic.
    Red line - 2nd harmonic.

    ao1jorgh1cwo.jpg
    Figure 32. SL1000 harmonic distortion analysis.

    c8n0n51i4ghs.jpg
    Figure 33. SL2000 harmonic distortion analysis.

    7u1djacwamks.jpg
    Figure 34. SL2500 harmonic distortion analysis.

    c8g0cerh2cpt.jpg
    Figure 35. SL3000 harmonic distortion analysis.

    4jibxdzfmp8c.jpg
    Figure 36. RD0194 harmonic distortion analysis.

    wfojef0u16nl.jpg
    Figure 37. RD0198 harmonic distortion analysis.

    References

    1. Jeff Bagby, "How to Achieve Accurate In-Room Quasi-Anechoic Free-Field Frequency Response Measurements Down to 10 Hz", white paper, January 3, 2014, presented at Loudspeaker Design Workshop”, Kokomo, IN, December 14, 2013.

    2. Christopher J. Struck, Steve F. Temme, " Simulated Free Field Measurements", Journal of the Audio Engineering Society, Vol. 42, No.6, June 1994.

    3. Michael LaLena, "Speaker Testing and Analysis", https://www.diyaudioandvideo.com/Tutorial/SpeakerResponseTesting/
    "So hot it burns Mice!"~DK
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
    "Knowledge, without understanding, is a path to failure."~DK
    "Those who irrationally rail against something or someone that is no threat to them, actually desire (or desire to be like) the thing or person they are railing against."~DK
  • westmassguywestmassguy Posts: 6,346
    Nice work Ray.
    Home Theater/2 Channel:
    Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
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  • DarqueKnightDarqueKnight Posts: 6,510
    edited August 2018
    SDA Tweeter Rankings

    Throughout the years it has been said that the SL2000 was the worst performing/worst sounding of the SDA tweeters. The quantitative measurements and physical inspections done in this study seem to support that. The SL2000 rated at the bottom in terms of build quality, balanced frequency response, and harmonic distortion among the six tweeters tested.

    Build Quality

    1. RD0198
    2. RD0194
    3. SL3000
    4. SL2500
    5. SL1000
    6. SL2000

    Frequency Response

    1. RD0198
    2. RD0194
    3. SL3000
    4. SL2500
    5. SL1000
    6. SL2000

    Harmonic Distortion

    1. RD0198
    2. RD0194
    3. SL3000
    4. SL1000
    5. SL2500
    6. SL2000
    "So hot it burns Mice!"~DK
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
    "Knowledge, without understanding, is a path to failure."~DK
    "Those who irrationally rail against something or someone that is no threat to them, actually desire (or desire to be like) the thing or person they are railing against."~DK
  • K_MK_M Posts: 1,315
    SDA Tweeter Rankings

    Throughout the years it has been said that the SL2000 was the worst performing/worst sounding of the SDA tweeters. The quantitative measurements and physical inspections done in this study seem to support that. The SL2000 rated at the bottom in terms of build quality, balanced frequency response, and harmonic distortion among the six tweeters tested.

    Build Quality

    1. RD0198
    2. RD0194
    3. SL3000
    4. SL2500
    5. SL1000
    6. SL2000

    Frequency Response

    1. RD0198
    2. RD0194
    3. SL3000
    4. SL2500
    5. SL1000
    6. SL2000

    Harmonic Distortion

    1. RD0198
    2. RD0194
    3. SL3000
    4. SL1000
    5. SL2500
    6. SL2000

    Sounds about right.
    By the way, did you ever get around to doing the Frequency Response of the MW mentioned earlier??
    Lsi15, Lsi9, LsiC,Rta11t,M5jr+,M4,SDA 3.1TL, SDA SRS 2.3TL, Rti6....Still listing stuff, a work in progress.
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  • DarqueKnightDarqueKnight Posts: 6,510
    No.
    "So hot it burns Mice!"~DK
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
    "Knowledge, without understanding, is a path to failure."~DK
    "Those who irrationally rail against something or someone that is no threat to them, actually desire (or desire to be like) the thing or person they are railing against."~DK
  • K_MK_M Posts: 1,315
    edited January 19
    Tony M wrote: »

    I said I've heard over the years there was a rise in amplitude around the 5khz. region.
    Is my memory wrong about the all the discussions about why the SL2000 sounds so bad most of the time?

    The 5Khz region is where I was concentrating my curiosity at in the graphs. As you can see and.

    Prior to your comment, I had never heard any mention of an amplitude rise in the 5 kHz region. All the discussions I know about were concerning the 5 dB rise in the 13 kHz region.

    With the tweeters mounted in "Free Space" with no speaker baffle, you are seeing the effects of Baffle edge diffraction taking place at a higher frequency, than when mounted in the speaker.

    http://www.linkwitzlab.com/diffraction.htm
    http://ampslab.com/blog/2017/09/06/dome-tweeters/

    The small dimensions of the face plate create a ripple effect when frequencies are a wavelength of the dimensions radiating from the tweeter dome.

    In this case, it is approximately 4.5" wide, and there for a null around approximetly 5000hz and a resultant rise at about 10khz and about 2.5 khz.

    Since the height dimension is smaller, diffraction will occur at a different frequency and help mask some of the ripple of up and down levels with rising frequency.

    Lsi15, Lsi9, LsiC,Rta11t,M5jr+,M4,SDA 3.1TL, SDA SRS 2.3TL, Rti6....Still listing stuff, a work in progress.
    B+W-Sold
    Epos-Now gone
    Infinity-Sold
    Advent-Now gone
    Yamaha A-S801
    Yamaha RX-V377
    Yamaha RX-A860
    Yamaha RX-A3060
    Harman Kardon Hk-350i
    Harman Kardon Hk-........
    Harman Kardon PM-665
    Harman Kardon HK-775
    Pioneer.......Stereo Receiver

  • sevendogsbsdsevendogsbsd Posts: 3
    Thank you for this article. After 31 years, I updated my SDA2A's SL2000 tweeters to the RDO194-1 from Midwest Speaker Repair. I did not do any before and after critical listening but I swear they sound like a new pair of speakers. I had thought about buying new speakers and that perhaps mine were just old but this simple and inexpensive update brought them back to life. Thanks!
    Polk Audio SDA-2A, Carver M1.0, Carver C2, Sony CD player.
  • geppy1geppy1 Posts: 2,697
    Great stuff I never really had much of a problem with the SL 1000
  • gp4jesusgp4jesus Posts: 1,224
    edited June 24
    Do my eyes deceive me or does the RD0 194 frame separate cleanly from the tweeter allowing mounting in a RD0 690(RTi A series) frame?

    Thnx Tony
    Samsung 60" UN60ES6100 LED
    Outlaw Audio 976 Pre/Pro
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    Canare 14 ga - LCR tweeters inside; CC outside
    BJC 10 ga - LCR mids, inside & out
    8 ga Powerline - LR woofers, inside & out

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  • DarqueKnightDarqueKnight Posts: 6,510
    The RD0194 tweeter can be taken out of its frame. I do not know it can be mounted in an RD0690 frame, or if doing so would compromise the 194's performance.
    "So hot it burns Mice!"~DK
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
    "Knowledge, without understanding, is a path to failure."~DK
    "Those who irrationally rail against something or someone that is no threat to them, actually desire (or desire to be like) the thing or person they are railing against."~DK
  • gp4jesusgp4jesus Posts: 1,224
    edited June 25
    1000 thanks for your thorough research.
    The RD0194 tweeter can be taken out of its frame.
    Great! Thnx for the quick reply.
    I do not know it can be mounted in an RD0690 frame...
    likely. Several years ago someone on this forum successfully replaced a ‘690* w/an aftermarket ring tweeter** similar to a Polk 700 series speaker - LOVED the results!
    * RTi A9s
    ** XO upgrades didn’t “do it” for him
    ...or if doing so would compromise the 194's performance.
    possibly - thanks for the cautionary advice.

    Tony
    Samsung 60" UN60ES6100 LED
    Outlaw Audio 976 Pre/Pro
    Samsung BDP, DirecTV Rcvr, Xbox 360, Dennon LDP, Phillips CD chgr

    Canare 14 ga - LCR tweeters inside; CC outside
    BJC 10 ga - LCR mids, inside & out
    8 ga Powerline - LR woofers, inside & out

    LR: tri-amped RTi A7. Woofers, Rotel 98X amp; M & T, P'sound HCA-1000
    CC: Rotel RB985 -> tri-amped CSi A6
    5 Audio Pro Subs: 1 B1.39: 1 Evidence at each corner
    Surrounds: Hafler XL280 -> AR 12 ga -> RTi A3*
    Power Conditioning & Distribution:
    3 dedicated 20A feeds; APC H15; 4 Furman Miniport 20s
    *Bi-amped by years end
  • gp4jesusgp4jesus Posts: 1,224
    194s in any RTi A series speaker is a nice idea and will remain just that - 194s are anything BUT a drop in.

    A comparison of your 194 photos to a 690’s physical etc, measurements demands MAJOR surgery to the closure primarily due to ~twice the magnet diameter* among other things - *sigh*
    * 690 series ~1”

    Thanks DK

    Tony
    Samsung 60" UN60ES6100 LED
    Outlaw Audio 976 Pre/Pro
    Samsung BDP, DirecTV Rcvr, Xbox 360, Dennon LDP, Phillips CD chgr

    Canare 14 ga - LCR tweeters inside; CC outside
    BJC 10 ga - LCR mids, inside & out
    8 ga Powerline - LR woofers, inside & out

    LR: tri-amped RTi A7. Woofers, Rotel 98X amp; M & T, P'sound HCA-1000
    CC: Rotel RB985 -> tri-amped CSi A6
    5 Audio Pro Subs: 1 B1.39: 1 Evidence at each corner
    Surrounds: Hafler XL280 -> AR 12 ga -> RTi A3*
    Power Conditioning & Distribution:
    3 dedicated 20A feeds; APC H15; 4 Furman Miniport 20s
    *Bi-amped by years end
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