Turning normal speakers into SDA’s

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  • FTGVFTGV Posts: 3,651
    xschop wrote: »
    Crosstalk cancellation is the crux of SDA.
    Exactly. Its' nothing mystical or magic. SDA's are simply a two way loudspeaker with some extra drivers strategically placed and wired to reproduce a difference signal. Think the old Halfer circuit but used at the front of the stage instead of as ambient rear surrounds.
  • delkaldelkal Posts: 568
    edited September 2018

    The more I think about your approach the more I see advantages to the Active vs Passive SDA setup. Yes you would need a separate integrated amp but that is no different than having a separate sub. And the ability to adjust the volume and tone would be great for tweaking to get it perfect.

    This seems too simple (or its a Eureka moment)....But instead of taking the signal from the amp speaker output (and reducing it with a voltage reducer) does anyone see why you can't do this directly from the positive preamp outs? I would toss my sub to the curb if I could hook up a couple bookshelf speakers and a spare amp to get some kind of SDA effect.


    Just one question though (to anyone). Unless I am misunderstanding (which is highly likely) with this setup it seems like both dimensional speakers signal and phase is the same (mono) on both right and left dimensional speakers. Is this how it works on the original SDAs? Or is the phase different between the right and left channels?

    Post edited by KennethSwauger on
  • I wonder how many of the nay sayers have heard what the op is proposing doing? Or how many have heard stacked sda's that I was advised against?? I say give it a shot and you just may learn something and have fun in the process. I'm betting the "experiment" will also make you appreciate your CRS's a LOT more. It's also not a bad idea to have a reference point of how bad something can sound.
  • Viking64Viking64 Posts: 4,237
    I just turned my SDAs into normal speakers. B)

    uh8n6ykcrxq9.jpg
  • BlueFoxBlueFox Posts: 12,032
    I sold my SDAs. :)

    Bud - Silicon Valley

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  • Viking64 wrote: »
    I just turned my SDAs into normal speakers. B)

    uh8n6ykcrxq9.jpg

    Cool beans B) ; I use something a little less dramatic like disconnecting my neutrik when it's needed
  • Viking64Viking64 Posts: 4,237
    Cool beans B) ; I use something a little less dramatic like disconnecting my neutrik when it's needed

    I tried doing that, but I couldn't figure out how to unplug those pesky things.

    I guess Grandpa's rusty jack-knife through the dimensional drivers would have done just as well, but it's in my tackle box and the pugs took it fishing last week and somehow it fell out of the boat and is now sitting at the bottom of Lake Champlain.

    All other sharp objects have been removed from my "grab area" ever since...."the incident". :p
  • stretchlstretchl Posts: 1,295
    mhardy6647 wrote: »
    The winning aphorism was:
    If you eat a live toad for breakfast, nothing worse will happen for the rest of the day,

    Words to live by.

    When he would hear someone complaining about how hard they're job is, or what a crappy day they'd had at work, my dad would say, "Beats diggin' ditches," which he did for years for Cincinnati Gas and Electric back in the late 1940's. I think about that once in a while when I'm complaining about my job, which in actuality is about as good as it gets and better than I deserve.

    “Anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.'
    - Isaac Asimov

    Hi-Fi
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  • stretchlstretchl Posts: 1,295
    @mlistens03 - This is from an interview with Steve Jobs. After he got fired from Apple Computer. But before he changed the world forever with the iPhone.


    “Anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.'
    - Isaac Asimov

    Hi-Fi
    Apple Lossless --> Squeezebox Touch --> Joule Electra LA-100 Mark iii --> Yaqin MC-10t --> LSiM-705's
    Cabling by Groneberg
    Visuals
    http://StretchPhotography.com
    http://Vimeo.com/channels/stretchphoto
  • mhardy6647mhardy6647 Posts: 22,977
    This is interesting stuff -- Personally I am fascinated by analog solutions to brute force problems (e.g., analog, B&W compatible color television, or analog, mono-compatible FM multiplex stereo). The signal processing and manipulation (not to mention the phase linearity, timing and bandwidth requirements) are impressive.

    I say this as a prologue to a random thought: I'd have to think, in this day and age, that the signal manipulation required for the "SDA effect" would be far easier to implement in the digital domain. Indeed, my impression was that the proliferation of soundbars on the market today would do something along these lines(?).

    And I say that as a prologue to an on-topic (sort of) comment. There's a countermelody to this thread referencing the "Hafler circuit", but I am not sure some of you would know what that is! David Hafler (of Acrosound, Dynaco, and Hafler fame) developed a really simple :) method for ambience recovery, which he ultimately called "Dynaquad", that presaged the quad frenzy of the early 1970s. Ken described it well, but I thought it would be interesting for folks who want to experiment with similar techniques to see the "Dynaquad" circuit.

    px60dvix27eu.png

    The Dynaco "Quadaptor" used a unique (AFAIK) triple gang rheostat to adjust signal levels.

    I've (ahem) actually got a Dynaco QD-1 "Quadaptor" a-sittin' on a shelf (imagine that?!). :)

    Other companies (e.g., Radio Shack, Lafayett, Electrovoice, etc.) sold variants of this basic Hafler design, and, in fact, Dolby "ProLogic" used the same basic approach as Hafler's, with the addition of "logic steering" to enhance the 'rear channel' effects (whatever that might mean in a practical sense!).

    http://audiokarma.org/forums/index.php?threads/dynaco-quadaptor-vs-realistic-quatravox.635021/
    https://midimagic.sgc-hosting.com/quadmuse.htm

  • delkaldelkal Posts: 568
    Hey guys. I have SDA! After reading Ken's posts on active dimensional SDA and looking at the schematics for the original blade blade SDAs I hooked up something that works! I now have an accessory bookshelf system that gives the SDA effect.

    Not wanting to mess up anything valuable I searched my basement and found a $30 yard sale AV receiver and some $10 goodwill Polk bookshelf speakers. I also found 20 feet of no name wire (starting to turn green too). Looking at the Polk schematics the dimensional speakers are only fed from the positive outputs on your amp. So I put a single wire from the right positive amp output to the right speaker positive (and the same for the left positive to left speaker positive). To complete the circuit you have to mimic what the SDA interconnect does. To do that you take a separate 2 strand piece of speaker wire and connect one end to one speaker with the correct polarity. Then the other end to the other speaker with reversed polarity. It is very important you get the interconnect connected right. If you connect both ends the way you normally connect a speaker you will have a short! One end MUST be connected in reverse polarity. Check the DC resistance before hooking it to your amp! It should not be close to zero ohms.

    When I hooked the speakers up this way I checked DC resistance (at the leads that go to the amp) and it only read about 2.8 Ohms. Half of what a single speakers was. My cheap amp couldn't take that low of an impedance so I hooked one 1 ohm resistor (10 watts) on each side between the amp out and the speaker (to the single amp out wire connect one end to the resistor, then connect the resistor to the speaker positive).

    To test, when you play this alone everything sounds spacey. There is no imaging and you can't tell where the sounds are coming from. Also the vocals and anything centered are barely audible.

    My CD player has 2 outputs so I connected one to my regular setup and one to the new "SDA" setup. I started listening to Abbey Road with the "SDA" volume off and it sounded like it always does. But when I turned up the volume of the SDA setup it was WOW, My room instantly opened up It was like I was in a cavern and its the first time I clearly head front to back depth 3-D with my system. I could also hear sounds coming from outside of where the speakers were placed.

    Don't believe the people that say it will not work or will sound awful. The components I used were some of the cheapest mid/lo-fi imaginable but I kept wanting to keep it on. Every time I tuned it off my system sounded flat in comparison


    Now for a BIG disclaimer.
    My knowledge of schematics are rudimentary at best.
    My writeup might have something unclear or ambiguous. Try and understand the concept for a reality check.
    If you set up the interconnect wrong you will short your amp.
    You will be running speakers in parallel giving half the impedance. Some amps can't take that so I had to put resistors on mine. Check for heat.
    I wouldn't try this with anything expensive. Actually you should only try this with disposable components you were going to throw away but kept it in your basement instead.

    But it works.

  • stretchlstretchl Posts: 1,295
    Can someone point me a post somewhere that will give me an idea of what the deal was with the SDA line? I've heard of it but I'm not familiar with what all the fuss is about. Thanks.
    “Anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.'
    - Isaac Asimov

    Hi-Fi
    Apple Lossless --> Squeezebox Touch --> Joule Electra LA-100 Mark iii --> Yaqin MC-10t --> LSiM-705's
    Cabling by Groneberg
    Visuals
    http://StretchPhotography.com
    http://Vimeo.com/channels/stretchphoto
  • aprazer402aprazer402 Posts: 1,453
    This thread --> http://forum.polkaudio.com/discussion/136502/sda-handbook/p1 See it's last post for the link to the SDA Handbook written by the forum's DarqueKnight which is an excellent place to start. Direct link also available here: http://vr3mods.com/LCSDAUpgrade.php Lots to read.
  • pitdogg2pitdogg2 Posts: 14,309
    edited September 2018
    stretchl wrote: »
    Can someone point me a post somewhere that will give me an idea of what the deal was with the SDA line? I've heard of it but I'm not familiar with what all the fuss is about. Thanks.

    Dude you're a professor in college, yet the internet escapes you. Jeesh lol

    http://www.academia.edu/629629/SDA_Surround_Technology_White_Paper
  • stretchlstretchl Posts: 1,295
    Touché. ;)
    “Anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.'
    - Isaac Asimov

    Hi-Fi
    Apple Lossless --> Squeezebox Touch --> Joule Electra LA-100 Mark iii --> Yaqin MC-10t --> LSiM-705's
    Cabling by Groneberg
    Visuals
    http://StretchPhotography.com
    http://Vimeo.com/channels/stretchphoto
  • FTGVFTGV Posts: 3,651
    edited September 2018
    delkal wrote: »
    Don't believe the people that say it will not work or will sound awful.
    Some are of the impression that if it does not have an SDA badge on it it can't possibly work. In actuality the concept is quite simple and easy to replicate as you have found with your experiment. Your just using four enclosures instead of two. As Ken points out the use of separate speakers and amp give you the benefit of experimenting with different dimensional driver spacing and control over their levels. My experimenting was similar to yours though I used a midrange driver bandwidth limited from 350-2k hz. In later generations of SDA 's Polk found it benificial to limit the dimensional signal range to approx 150 -2k or so. You might try disconnecting the tweeters in your extra speakers.

  • mlistens03mlistens03 Posts: 2,632
    Delkal,
    Great to hear that it worked! I’m gonna give it a go tomorrow after school. We have yet to make it to the HobbyTown to pick up resistors. We were literally sitting in the parking lot, when we got invited to lunch and we left. :confused: I don’t know why I couldn’t have just run in, but parents sometimes have reasons for things beyond my reach. Oh well.
    Not Tom or Trey or Jim just Micah
    KEF Q150s, NAD 1155 preamp and 4155 tuner courtesy of DaddyJT, NAD C352 playing power amp, BJC Belden cables, Technics SL3200, Marantz CD6004 courtesy of Clipdat, Salamander Archetype rack, Millenium Falcon :)
    I've always thought the goal of high-end audio was not to have your neighbors bang on the wall and say, 'Turn that darn music down' but to have your neighbors bang on the wall and say, 'Tell your friends to go home and you can practice later this week'.

    Resident Child of Club Polk
  • mhardy6647mhardy6647 Posts: 22,977
    Hobby Town sells resistors?!
  • mlistens03mlistens03 Posts: 2,632
    mhardy6647 wrote: »
    Hobby Town sells resistors?!

    Yes, I believe they bought RadioShack or something, and now RadioShack parts are sold in HobbyTown.
    Not Tom or Trey or Jim just Micah
    KEF Q150s, NAD 1155 preamp and 4155 tuner courtesy of DaddyJT, NAD C352 playing power amp, BJC Belden cables, Technics SL3200, Marantz CD6004 courtesy of Clipdat, Salamander Archetype rack, Millenium Falcon :)
    I've always thought the goal of high-end audio was not to have your neighbors bang on the wall and say, 'Turn that darn music down' but to have your neighbors bang on the wall and say, 'Tell your friends to go home and you can practice later this week'.

    Resident Child of Club Polk
  • mlistens03mlistens03 Posts: 2,632
    stretchl wrote: »
    Can someone point me a post somewhere that will give me an idea of what the deal was with the SDA line? I've heard of it but I'm not familiar with what all the fuss is about. Thanks.
    Mind boggling sound stage. Do some Googling, and you can find info on them. Then get your ears on a set of SDA’s. They are awesome.
    FTGV wrote: »
    delkal wrote: »
    Don't believe the people that say it will not work or will sound awful.
    Some are of the impression that if it does not have an SDA badge on it it can't possibly work. In actuality the concept is quite simple and easy to replicate as you have found with your experiment. Your just using four enclosures instead of two. As Ken points out the use of separate speakers and amp give you the benefit of experimenting with different dimensional driver spacing and control over their levels. My experimenting was similar to yours though I used a midrange driver bandwidth limited from 350-2k hz. In later generations of SDA 's Polk found it benificial to limit the dimensional signal range to approx 150 -2k or so. You might try disconnecting the tweeters in your extra speakers.

    Thanks for the tips!
    Not Tom or Trey or Jim just Micah
    KEF Q150s, NAD 1155 preamp and 4155 tuner courtesy of DaddyJT, NAD C352 playing power amp, BJC Belden cables, Technics SL3200, Marantz CD6004 courtesy of Clipdat, Salamander Archetype rack, Millenium Falcon :)
    I've always thought the goal of high-end audio was not to have your neighbors bang on the wall and say, 'Turn that darn music down' but to have your neighbors bang on the wall and say, 'Tell your friends to go home and you can practice later this week'.

    Resident Child of Club Polk
  • delkaldelkal Posts: 568
    edited September 2018
    FTGV wrote: »
    delkal wrote: »
    Don't believe the people that say it will not work or will sound awful.
    Some are of the impression that if it does not have an SDA badge on it it can't possibly work. In actuality the concept is quite simple and easy to replicate as you have found with your experiment. Your just using four enclosures instead of two. As Ken points out the use of separate speakers and amp give you the benefit of experimenting with different dimensional driver spacing and control over their levels. My experimenting was similar to yours though I used a midrange driver bandwidth limited from 350-2k hz. In later generations of SDA 's Polk found it benificial to limit the dimensional signal range to approx 150 -2k or so. You might try disconnecting the tweeters in your extra speakers.

    I set this up just to experiment some but I was amazed at the difference this crude setup made as soon as I turned it on. It was far from subtle and instantly recognizable . As you turn the volume up on the SDA amp and you can hear your room getting bigger. Never heard anything like it before and the ability to dial in the amount of SDA is nice too.

    I used Polk M10 bookshelf speakers so it does have a limited base response. In my limited listening time I did start hearing a lot of mid-higher pitched sounds I never noticed before on the far edges of the room. It didn't sound too bright to me but I don't hear treble the way I used to.

    Someone with better ears should try it.
  • stretchlstretchl Posts: 1,295
    Why is polk no longer making them?
    “Anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.'
    - Isaac Asimov

    Hi-Fi
    Apple Lossless --> Squeezebox Touch --> Joule Electra LA-100 Mark iii --> Yaqin MC-10t --> LSiM-705's
    Cabling by Groneberg
    Visuals
    http://StretchPhotography.com
    http://Vimeo.com/channels/stretchphoto
  • DSkipDSkip Posts: 16,115
    Wide baffle speakers don't sell anymore, especially to the masses.
  • mlistens03mlistens03 Posts: 2,632
    edited September 2018
    stretchl wrote: »
    Why is polk no longer making them?

    Well, you’d have to ask someone more knowledgeable for a definitive answer, but I’d guess because they’d have no where to sell them except the big box stores, as most Hi-Fi shops wouldn’t sell speakers with the Polk badge on them, except for an enlightened few. And you can imagine how terrible it would go for them to Ben sold by they people at big box stores who know nothing and would sell them with non common ground amplifiers. They may have also been expensive to manufacture.
    Not Tom or Trey or Jim just Micah
    KEF Q150s, NAD 1155 preamp and 4155 tuner courtesy of DaddyJT, NAD C352 playing power amp, BJC Belden cables, Technics SL3200, Marantz CD6004 courtesy of Clipdat, Salamander Archetype rack, Millenium Falcon :)
    I've always thought the goal of high-end audio was not to have your neighbors bang on the wall and say, 'Turn that darn music down' but to have your neighbors bang on the wall and say, 'Tell your friends to go home and you can practice later this week'.

    Resident Child of Club Polk
  • mlistens03mlistens03 Posts: 2,632
    DSkip wrote: »
    Wide baffle speakers don't sell anymore, especially to the masses.

    This as well.
    Not Tom or Trey or Jim just Micah
    KEF Q150s, NAD 1155 preamp and 4155 tuner courtesy of DaddyJT, NAD C352 playing power amp, BJC Belden cables, Technics SL3200, Marantz CD6004 courtesy of Clipdat, Salamander Archetype rack, Millenium Falcon :)
    I've always thought the goal of high-end audio was not to have your neighbors bang on the wall and say, 'Turn that darn music down' but to have your neighbors bang on the wall and say, 'Tell your friends to go home and you can practice later this week'.

    Resident Child of Club Polk
  • mhardy6647mhardy6647 Posts: 22,977
    edited September 2018
    I think Polk stopped making & selling the SDA loudspeakers before the thin towers became the big thing (ca. 1991, interpolating from www.polksda.com)


    8d5ttswwkaja.png
    source: https://polksda.com/pdfs/1991SRSAd.pdf
  • mhardy6647mhardy6647 Posts: 22,977
    FWIW, based on information from Google, the last (?) test of an SDA model, at least from Stereo Review, appears to have been November 1988.
    https://www.americanradiohistory.com/Archive-HiFI-Stereo/80s/HiFi-Stereo-Review-1988-11.pdf

    51sndb862b5i.png
  • mlistens03mlistens03 Posts: 2,632
    edited September 2018
    What is up with the top and bottom drivers on the left side in that pic Doc? They seem different from the rest of them all... is that normal?
    Not Tom or Trey or Jim just Micah
    KEF Q150s, NAD 1155 preamp and 4155 tuner courtesy of DaddyJT, NAD C352 playing power amp, BJC Belden cables, Technics SL3200, Marantz CD6004 courtesy of Clipdat, Salamander Archetype rack, Millenium Falcon :)
    I've always thought the goal of high-end audio was not to have your neighbors bang on the wall and say, 'Turn that darn music down' but to have your neighbors bang on the wall and say, 'Tell your friends to go home and you can practice later this week'.

    Resident Child of Club Polk
  • delkaldelkal Posts: 568
    mlistens03 wrote: »
    Delkal,
    Great to hear that it worked! I’m gonna give it a go tomorrow after school. We have yet to make it to the HobbyTown to pick up resistors. We were literally sitting in the parking lot, when we got invited to lunch and we left. :confused: I don’t know why I couldn’t have just run in, but parents sometimes have reasons for things beyond my reach. Oh well.

    Check the DC resistance of your speakers first so you can get an idea what resistors to use. The Polk M10 bookshelf speakers I used are rated as 8 ohms but the DC resistance was closer to 4.5ohms. I know this is normal but when I wired them with the interconnect the DC resistance dropped below 3 and I started to worry. I would guess two 8 ohm speakers wired with the interconnect is the equivalent of a 4 ohm load. My amp needs a 6 ohm minimum so I added a one ohm 10 watt resistor on each input to make up for this.

    I played the system for a while at moderate to loud volumes and the amp and the resistors stayed cool. But when you wire two speakers in parallel you get lower impedance and that might be a concern. Just be aware.
  • mlistens03mlistens03 Posts: 2,632
    delkal wrote: »
    mlistens03 wrote: »
    Delkal,
    Great to hear that it worked! I’m gonna give it a go tomorrow after school. We have yet to make it to the HobbyTown to pick up resistors. We were literally sitting in the parking lot, when we got invited to lunch and we left. :confused: I don’t know why I couldn’t have just run in, but parents sometimes have reasons for things beyond my reach. Oh well.

    Check the DC resistance of your speakers first so you can get an idea what resistors to use. The Polk M10 bookshelf speakers I used are rated as 8 ohms but the DC resistance was closer to 4.5ohms. I know this is normal but when I wired them with the interconnect the DC resistance dropped below 3 and I started to worry. I would guess two 8 ohm speakers wired with the interconnect is the equivalent of a 4 ohm load. My amp needs a 6 ohm minimum so I added a one ohm 10 watt resistor on each input to make up for this.

    I played the system for a while at moderate to loud volumes and the amp and the resistors stayed cool. But when you wire two speakers in parallel you get lower impedance and that might be a concern. Just be aware.

    I will certainly be careful.
    I’m going to use a set of Boston Acoustics CR-75 speaker’s, which IIRC don’t drop below 6 ohms at any point in their frequency response. I don’t think 3 ohms will be an issue for most amplifiers, especially at the levels I listen at (usually less than 90 DB, so under a watt.)
    Not Tom or Trey or Jim just Micah
    KEF Q150s, NAD 1155 preamp and 4155 tuner courtesy of DaddyJT, NAD C352 playing power amp, BJC Belden cables, Technics SL3200, Marantz CD6004 courtesy of Clipdat, Salamander Archetype rack, Millenium Falcon :)
    I've always thought the goal of high-end audio was not to have your neighbors bang on the wall and say, 'Turn that darn music down' but to have your neighbors bang on the wall and say, 'Tell your friends to go home and you can practice later this week'.

    Resident Child of Club Polk
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