SDA-2 Restoration / modification

I finally found the time to complete the repairs and modifications on my SDA-2 Polks.
I built new crossovers that combined the two crossovers in each speaker. Updated with new caps and resistors. Removed poly switches and replaced them with .5 ohm resistors. I removed all spade connectors and other bolt on / crimp on connections in the speakers and replaced all wire with high quality 12 gauge silver plated wire with teflon insulation for everything. All connections in the speaker are now soldered. Installed hurricane nuts for all of the drivers. Replaced all four cable connections on the back of each speaker. I still have to make some new speaker cables and interconnect cables.
My first impression is that there is a huge improvement in imaging. The SDA function seems to work very well now. I am sensitive to speakers with overly bright tweeters. I was worried that removing the poly switches would reduce the resistance in the tweeter circuit dramatically and cause them to be over powering. All the drivers have come alive and seem to be balanced nicely. The speakers are a little light on the bass but fare pretty well for their size. It is amazing how many spade connectors are in these speakers. Not only are these made out of poor quality, they don't make great connections. Plus the crimped wire connection on the spade is another bad connection. Removing these is a low cost modification that can make a noticeable difference. This combined with replacing the wire. I used almost 90 feet of wire inside these speakers. Thats a lot of wire in the audio circuit. It didn't cost that much to buy higher quality wire. You will notice the previous owner had replaced the veneer with curly maple. Looking forward to running them for a while and see how they sound. Note the placement of the speakers in the photo was only for testing them with another amp. I realize they are not supposed to be that far apart and not toed in.
Thank you all for your help!!!



  • NightfallNightfall Posts: 9,422
    I haven't heard the older models but I'm surprised you find them light in the bass department.
    afterburnt wrote: »
    They didn't speak a word of English, they were from South Carolina.

    Village Idiot of Club Polk
  • FestYboyFestYboy Posts: 3,858
    Not sure how my initial post didn'

    Anywho, placement closer to the back wall should improve the bass response. Also I recommend you place the inductors at 90° to each other.
  • Scott99Scott99 Posts: 33
    Don't get me wrong, they do pretty well in the bass department. I guess I am comparing them to my JBL 4435's which is not fair. They are more than twice the size, have two 15" drivers and a bi-radial horn.
  • Scott99Scott99 Posts: 33
    As I mentioned in my post.
    "Note the placement of the speakers in the photo was only for testing them with another amp. I realize they are not supposed to be that far apart and not toed in."

    They sound good at just under 8 feet apart with zero toe and about 1 foot from back wall.
    I will try them closer to the back wall.

  • agfrostagfrost Posts: 2,329
    You should put those JBL bookshelf speakers up on stands.


    Enjoy the music!
    SDA 2BTL * Musical Fidelity A5cr amp * Marantz DV-9500 * Modded Adcom GDA-600 DAC * Rythmik F8 (x2)
    Micro Seiki DQ-50 * A hodgepodge of cabling * Belkin PF60
    Preamp rotation: Krell KSL (SCompRacer recapped) * Manley Shrimp * PS Audio 5.0
  • You can start a business out of this experience. I would love to do this upgrade but at the moment don't have the time. If shipping wasn't so expensive I'd offer to pay you to make these upgrades to my pair. Can you share more on how you built your own crossovers?
  • mlistens03mlistens03 Posts: 2,759
    edited August 2018
    @VR3 does crossover work on these speakers, he has a website, I’ll find the link in a minute. I’ve never had anything done by him, but a ton of people here have. He does good work, with good quality parts. , .
  • F1nutF1nut Posts: 45,212
    I'm sorry I missed this until now. I have a few important suggestions. First, those inductors need to be perpendicular in relation to each other and the 2 larger ones should be standing on end. Next, spike the speakers and get some sort of carpet on the floor.
    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."

    President of Club Polk

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