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  1. #1

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    Default SRS upgrade questions (and more..)

    I have just a few mods left on my SRS, and I've been through dozens of threads looking for some key information. As always, I would be very appreciative of any information to help 'fill in the blanks'!

    1) There are 3 inductors that I want to replace in the HF section of the x'over. From the schematics they are listed as two 0.4mH and one 0.7mH. On the 1.2 TL's that DK upgraded he used a 0.75mH inductor of 26 AWG and unwound it to get the 0.75mH. He states that the measured DCR of the upgraded 0.7mH inductors is 1.72 and 1.75 ohm (respectively for R and L channel). I assume that 1) the 0.4mH inductors on the SRS and TL's are the same (22 AWG) and 2) that the 0.4mH 26 AWG inductors on the SRS and TL's are the same. Is this correct?

    2) DK noted that Polk recommended that the inductance and DCR on replaced inductors should be kept the same, with the exception of the large LF inductor (the 16mH inductor on both the TL and SRS, etc.). However, in looking at the SRS schematics it seems to me (I am NOT an electrical engineer ) that the two 2.75mH inductors in the LF section are also part of the circuit along with the 16mH inductor. If this is the case, lowering the DCR on these inductors may also contribute to the improved 'punch' of the bass. If I am incorrect in this assessment, then I hope to get direction on the upgraded inductor AWG that will get me close to the correct DCR.

    3) Lastly, and I think I have read something about this in the forum but again I cannot find it, from what I understand the dimensional array basically emits the opposite waveform at a precise time delay to cancel the interaural cross talk. Yet all 4 dimensional , all 4 stereo drivers, and the PR are in the same cabinet. As the PR is used in place of a bass driver, it is being ‘driven’ by the other drivers in the cabinet. I know that the passive radiator and it’s components are selected to work with the drivers. However, it seems to me (an electronic neophyte) that the stereo and dimensional drivers in being slightly out of phase would ‘muddy’ the effect produced by the passive radiator. Is this thinking correct, and if so, has anyone tried gluing MDF into the cabinet to section off the dimensional drivers? New project anyone?

  2. #2

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    Default

    Quote Originally Posted by dcoil View Post
    I have just a few mods left on my SRS, and I've been through dozens of threads looking for some key information. As always, I would be very appreciative of any information to help 'fill in the blanks'!

    1) There are 3 inductors that I want to replace in the HF section of the x'over. From the schematics they are listed as two 0.4mH and one 0.7mH. On the 1.2 TL's that DK upgraded he used a 0.75mH inductor of 26 AWG and unwound it to get the 0.75mH. He states that the measured DCR of the upgraded 0.7mH inductors is 1.72 and 1.75 ohm (respectively for R and L channel). I assume that 1) the 0.4mH inductors on the SRS and TL's are the same (22 AWG) and 2) that the 0.4mH 26 AWG inductors on the SRS and TL's are the same. Is this correct?

    2) DK noted that Polk recommended that the inductance and DCR on replaced inductors should be kept the same, with the exception of the large LF inductor (the 16mH inductor on both the TL and SRS, etc.). However, in looking at the SRS schematics it seems to me (I am NOT an electrical engineer ) that the two 2.75mH inductors in the LF section are also part of the circuit along with the 16mH inductor. If this is the case, lowering the DCR on these inductors may also contribute to the improved 'punch' of the bass. If I am incorrect in this assessment, then I hope to get direction on the upgraded inductor AWG that will get me close to the correct DCR.
    See posts 1, 13 and 15 of this thread:

    Further-Improvements-to-the-SDA-SRS-Custom-PCB-and-SDA-Inductor

    Quote Originally Posted by dcoil View Post
    3) Lastly, and I think I have read something about this in the forum but again I cannot find it, from what I understand the dimensional array basically emits the opposite waveform at a precise time delay to cancel the interaural cross talk. Yet all 4 dimensional , all 4 stereo drivers, and the PR are in the same cabinet. As the PR is used in place of a bass driver, it is being ‘driven’ by the other drivers in the cabinet. I know that the passive radiator and it’s components are selected to work with the drivers. However, it seems to me (an electronic neophyte) that the stereo and dimensional drivers in being slightly out of phase would ‘muddy’ the effect produced by the passive radiator. Is this thinking correct, and if so, has anyone tried gluing MDF into the cabinet to section off the dimensional drivers? New project anyone?
    The dimensional signal output level is half that of the stereo driver level and only covers the range of 200 to 1000 Hz. The four drivers work together at frequencies below 200 Hz. The passive radiator kicks in below 100 Hz, which is the region where all drivers are working together.

    Isolating the drivers would only produce detrimental effects since the passive radiator must be coupled to the drivers by internal air pressure (the "fluid coupling" mentioned in the SDA sales brochures).
    Last edited by DarqueKnight; 04-25-2013 at 11:20 PM.
    "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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    "Knowledge, without understanding, is a path to failure."~DK

  3. #3

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    Thanks DK for the thread link! I don't know how I overlooked this one. And I appreciate the explanation on the output and limited frequencies of the dimensional drivers. Good to know that in addition to the other mods I'm working on, I don't have to start cutting, fitting and gluing MDF into the cabinet...

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