SDA design question

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Comments

  • F1nutF1nut Posts: 37,528
    edited June 16
    SDA's are designed to be close to the rear wall to begin with. Generally, 5 to 6 inches gives the best results. Considering good speaker cables and a good interconnect cable I don't see how much closer one could get them unless you're using zip cord and the stock IC, but the bass gets boomy when too close.
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  • xschopxschop Posts: 532
    edited June 16
    No turbulence or "chuffing" here. If Mr Polk revisits the CRS+, he should use his Power Ports. More bass output per power input than the passive is what I'm discovering.

    Another reason I did this is because I can and have substituted the mw6511 with a mw6502 and a quick port swap. It digs even deeper and I have a few spares.

    I have also answered another unknown for myself. The tweeter at 3' oclock of the stereo driver still has same SDA effect as it does in factory triangle configuration. A bit wider I might add.

  • pitdogg2pitdogg2 Posts: 6,785
    Tweeter SDA effect?
    What am i missing here there is no tweeter SDA effect in the single tweeter species.
  • xschopxschop Posts: 532
    Exactly what I wasn't sure of, Pitt. WMG says crossover is 2K. of stereo driver and tweeter. I haven't ran across any info of where the SDA driver slopes off in it's higher Hz region or meshes with the opposite side tweeter's lower region.
  • pitdogg2pitdogg2 Posts: 6,785
    pretty sure the SDA driver stays below the tweeter or right up to it.
  • xschopxschop Posts: 532
    edited June 16
    If indeed the case, it's indicative of the various driver layouts between different models.
    Although I'm not installing the SL5000, it does allow closer proximity to the stereo driver, sounds better (to my ears) than the RD-0194. However the SL needs a 2.5k crossover for optimization.
  • westmassguywestmassguy Posts: 5,583
    Both the Dimensional and Stereo woofers have 2nd order low-pass filters. This applies to all generations
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  • Toolfan66Toolfan66 Posts: 13,077
    I'm usually all about one trying things, but I'm not getting this one at all...
    Liquor in the front Polks in the rear....
  • xschopxschop Posts: 532
    edited June 18
    I've been listening to as many genres of music with the tweeter at 3 o'clock, 1 o'clock, and 11 o'clock (same as factory but closer to stereo driver). 1 and 3 sound identical in wider soundstage, whereas 11 seems to narrow it back down.
    I'm having a fellow visit next weekend that's getting a set also and he'll weigh in on the matter. Im sure he'll bring his Floyd collection.

    As for the Power Ports they are staying put. I had to dial back from flat almost a quarter turn on bass control even before Cap replacement. I also installed a 2.0 ohm Mills resistor in place of the 2.7 ohm factory ceramic resistor to bring everything into balance since the low end is so pronounced...

    kkkc995c2w7o.jpg

    I'll also be moving crossovers and inductors externally and will solder new leads in at inputs and tweeter terminals.

    cd14ti6dcf55.jpg




  • F1nutF1nut Posts: 37,528
    As for the Power Ports they are staying put. I had to dial back from flat almost a quarter turn on bass control even before Cap replacement. I also installed a 2.0 ohm Mills resistor in place of the 2.7 ohm factory ceramic resistor to bring everything into balance since the low end is so pronounced...

    No offense, but that should tell you your idea wasn't a good one.
    Political Correctness'.........defined

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  • xschopxschop Posts: 532
    Maybe in your book, but in mine it elucidates the fact that it takes more power to run a passive radiator.
    After the cap install the mids also kicked in.
    Happy Fathers Day.
  • F1nutF1nut Posts: 37,528
    That's because the drivers are in harmony with the PR. They need each other to function properly. Without the back pressure from the PR the driver movement is looser than it should be, so it will take less power to move them, but on the other hand more power will cause them to over extend.
    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."


  • GatecrasherGatecrasher Posts: 1,596
    Just out of curiosity F1 I was wondering if you use SDAs? I can tell you have in the past but was wondering what you are currently using in your system. I just learned yesterday that you have some kind of a high-powered amp with like 500 watts per channel but other than that I don't know anything about your system.

    Can you describe it? I'm curious (in a good way). I've been on this forum for like seven years now and never really have seen you post much about your audio setup.
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  • FTGVFTGV Posts: 3,506
    edited June 18
    xschop wrote: »
    ... but in mine it elucidates the fact that it takes more power to run a passive radiator.
    A PR is not inherently less efficient than a port. My guess is that you may be using too short of a port thus pushing its tuning frequency higher than optimum and a higher frequency than what the PR is tuned to. The result would cause a bass boost (deviation from flat)around the tuning frequency that would give the impression of deeper and more powerfull bass.While the bass may sound louder it would in fact be less extended. For best results you will need to find out what frequency the PR is tuned to. Then adjust your port length to tune it to that same frequency. Otherwise you are comparing apples and oranges. The tuning frequency of a PR is adjusted by adding or removing mass(weight) to it. Of course the tuning frequency of the mass of air in a port is tuned by adjusting it's diameter and length. Internal cabinet volume and driver characteristics(Q,Fs and compliance) are all inter-related with the tuning frequency.

    Post edited by FTGV on
  • F1nutF1nut Posts: 37,528
    Just out of curiosity F1 I was wondering if you use SDAs? I can tell you have in the past but was wondering what you are currently using in your system. I just learned yesterday that you have some kind of a high-powered amp with like 500 watts per channel but other than that I don't know anything about your system.

    Can you describe it? I'm curious (in a good way). I've been on this forum for like seven years now and never really have seen you post much about your audio setup.

    Here's a pic.....

    6ql5vic0me9k.jpg
    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."


  • GatecrasherGatecrasher Posts: 1,596
    edited June 18
    You really get 500 watts per channel with .007% THD out of that?

    What cables do you use with it? They don't look like they have to be very long.
    POLK AUDIO SRT
    (Signature Reference Theater)

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    SRT 10.2 SYSTEM
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    (2) SRT Center Speakers
    (2) SRT Control Centers w/Remote
    (4) f/x1000 Surrounds
    (2) PSW650 Subs
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  • F1nutF1nut Posts: 37,528
    MIT cables, if course.
    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."


  • pitdogg2pitdogg2 Posts: 6,785
    You should hear that thing with bass boost engaged... talk about pools of great bass extensions
  • xschopxschop Posts: 532
    In response to FTGV, you are correct in your analogy of a standard port. In my application I am using Polk's Power Port which has different design parameters than a standard tube port. It uses shorter and smaller diameter tubes to achieve the same tuning freq. as a standard port while eliminating the turbulence and port noise that robs power.
  • K_MK_M Posts: 824
    xschop wrote: »
    In response to FTGV, you are correct in your analogy of a standard port. In my application I am using Polk's Power Port which has different design parameters than a standard tube port. It uses shorter and smaller diameter tubes to achieve the same tuning freq. as a standard port while eliminating the turbulence and port noise that robs power.

    Could you perhaps provide some photos as to how you are implementing these changes?
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  • xschopxschop Posts: 532
    edited June 19
    My test mules are mounted directly to the walls burning in the new caps. Try that with a factory set CRS+ and see how you like the bass response.

    5kr1hplefm6p.jpg

    oyilz49h6hdn.jpg

    The curve in the bracket allows clearance for the factory inductor coil leads. I dont think Ill be installing the Erse inductor since it increases bass according to WMG...

    jyqkpvgrr1ay.jpg



    Post edited by xschop on
  • xschopxschop Posts: 532
    Still exercising the caps at moderate volume and the mids are sounding gorgeous.. I ran across a calculator on another forum I want to see if my WAG comes close to the calculator.
    With the mw6511 I am using a 3.75" length x 2.2" I.D tube flared with 1/2" radius.
    To get the same tune from the substituted mw6502 Im using a length of 4.25"

    http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/53166-power-port-design-calculator.html
  • heiney9heiney9 Posts: 23,372
    SDA's had among the lowest bass distortion ever measured by Hirsch Labs, not to mention they have a very flat, extended response.

    Sounds to me like you mucked up a very good to excellent balance. SDA's had a certain balance, a part of what made them so easy to listen to. No doubt that balance has been upset, for good or bad depending on the user.

    Glad they are floating your boat, but this certainly should not be a common thing to do.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • heiney9heiney9 Posts: 23,372
    A steel plate to cover the PR opening? I would think there would be some resonance noise/distortion not only by the way it's fastened to the cabinet but the steel has different deflection characteristics than the cabinet. I would think this might cause some issues.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • xschopxschop Posts: 532
    Mighty assumptive Heiny, 1" HDF just like the rest of the enclosure.
    Ill be making slightly longer aluminum brackets when I go to mount in living room. And thru drilling to make them mount easier/quickly.

    The RD0194 sounds pretty good brightened up a touch to me.
  • heiney9heiney9 Posts: 23,372
    xschop wrote: »
    Mighty assumptive Heiny, 1" HDF just like the rest of the enclosure.
    Ill be making slightly longer aluminum brackets when I go to mount in living room. And thru drilling to make them mount easier/quickly.

    The RD0194 sounds pretty good brightened up a touch to me.

    Yeah, my bad. I swore I read you said you covered it with a steel plate, but I looked and you did not. So no sound issue there.

    H9

    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • xschopxschop Posts: 532
    After the polyswitch eviction that was creating a nasty distortion, I installed 1.2 ohm Mills resistors in their place and we are back to a good balance with crystal clear highs. I believe we'll be clocking the left channel tweeter at 2 o'clock and the right channel tweeter at 10 o'clock. This gives the best imaging sound as the tweets are as close to the stereo MWs as possible, (Much like a TMM with an offset tweeter).In the factory triangle config. my friend and I both agreed that the sound has too much of an 'airyness' about it.
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