Announcement

Collapse
No announcement yet.

Shahinian obelisk rebuild project

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Shahinian obelisk rebuild project

    Today I got a pair of used cabinets with crossovers of Shahinian Obelisk speakers that I would like to rebuild with new drivers, passive radiators, and crossovers.

    Click image for larger version

Name:	obelisk-cab-back-w640.jpg
Views:	1
Size:	30.9 KB
ID:	871434 Click image for larger version

Name:	obelisk-cab-front-w640.jpg
Views:	1
Size:	31.2 KB
ID:	871435

    I thought the obelisks were an interesting speaker back in the 80s but much too expensive for me back then. Shahinian has gone through several revs through the years with differing woofers/passive radiators, tweeters and mid-domes on top in 3 way versions of the obelisk.

    This is a very old version which had 3 tweeters, an 8" woofer and a 10" passive radiator on the back.
    Newer versions added a driver or two on the back face of the pyramid top which this doesn't have.

    Internally there's a board diagonally across dividing the box into a transmission line that folds
    at the pyramid top.

    The internal cross over is very simple with a fuse, one 6.8uf film capacitor and an inductor which doesn't
    seem to have any obvious markings on it. The three tweeters were connected in parallel.

    I would be interested in opinions of what to stuff in these. I have no problems soldering, etc, but am a little woodworking challenged, though I can probably ask someone local for assistance if necessary.

  • #2
    Those are very interesting. They break many of the common rules of speaker building. Based on the crossover being just a fuse, it is seems that they built a pretty box and threw drivers in it and just adjusted the tweeter level to balance out the woofer.

    Going from an 8" woofer to a tweeter would normally say you want a tweeter with a very low crossover and wideband woofer. You'd also want to minimize the woofer to tweeter distance - which you can't do. The three tweeters on top may cause some comb filtering and just weird effects. But, maybe in a omni-layout it won't be so bad.

    So, I guess the questions are:

    1) what are your expectations? Do you just want to reuse a cool looking box with some new drivers and a crossover that generally gets the levels correct and sounds good enough but not as good as many of the published designs? Or are you looking for a world class speaker with ultimate drivers and crossover?

    2) what is your budget? Are you looking at Dayton RS level drivers or Scan Speak Drivers?

    3) do you want to reuse the box exactly as is? do you want to re-use all three tweeters? or are you considering just one? are you going to re-veneer?

    4) Do you need drop in replacement size drivers? If so, what are the opening sizes. That metric versus english thing might come in to play when talking generically about 8" woofers.

    Seems like an interesting project.
    - Ryan

    CJD Ochocinco! ND140/BC25SC06 MTM & TM
    CJD Khanspires - A Dayton RS28/RS150/RS225 WMTMW
    CJD Khancenter - A Dayton RS28/RS150/RS180 WTMW Center

    Comment


    • #3
      I'm sorry if I didn't state it clearly The original crossover is a first order crossover.
      one inductor to the woofer. one fuse and one capacitor to the tweeters.

      From what I've read newer obelisks went with a three-way design and more complex crossover.
      Here's a photo I found on the net..
      Click image for larger version

Name:	newer-obelisks-w640.jpg
Views:	1
Size:	25.2 KB
ID:	859743

      I'll have to measure the holes to verify things will fit or that I'm able tweak the cabinets to fit things.
      I'm haven't yet received the grills, so that's another part of the project.

      I'm considering the 8" SB acoustics aluminum woofer that Jon mentioned in the '8" woofer crossed over to a 28mm tweeter' thread or siimilar drivers as used in past two ways. HiVi m8a, Dayton RS225. It looks like there are screws holding the pyramid baffles in place, so I might be able to try multiple configurations of upper drivers if I can fashion new ones. If not I'd probably use three 4-ohm tweeters connected in series, or cut a fourth hole for another tweeter and series/parallel connect 8ohm units to keep the impedance up.

      If I go with a three-way, I'd probably get the Dayton RS-52ANs and try the Dueland crossover approach Jon has in 'Proposal for a compact three way' thread.

      Comment


      • #4
        correction

        I unscrewed the crossover and tweeter baffle off one to take a closer look.
        I was mistaken, the crossover hard wired the woofer (except the fuse on the negative input terminal for all the drivers). It is a second order network to the tweeter.

        The capacitor measured about 7uF
        My multifunction meter meter couldn't measure the inductor's value.

        I took some pictures after I put new batteries into my camera.
        Click image for larger version

Name:	obelisk-baffle-w640.jpg
Views:	1
Size:	44.4 KB
ID:	859744Click image for larger version

Name:	obelisk-xover-w640.jpg
Views:	1
Size:	61.0 KB
ID:	859745
        Click image for larger version

Name:	obelisk-bottom-w640.jpg
Views:	1
Size:	28.3 KB
ID:	859746Click image for larger version

Name:	obelisk-topless-w640.jpg
Views:	1
Size:	29.4 KB
ID:	859747

        Comment


        • #5
          I measured the driver cut outs today.

          tweeters -- 87mm inner cutout, 117mm outer diameter
          woofer -- 180mm inner cutout, 223mm outer diameter
          passive radiator -- 221mm inner cutout, 250mm outer diameter

          It seems that I'll have to enlarge the passive radiator and woofer cut outs.

          A quick look over available drivers has ScanSpeak passive radiator 23W/0-00 as closest fit but slightly too big
          Dayton RS225-8 woofer is also slightly too big for the woofer hole.

          Comment


          • #6
            EB15, as a Shahinian Arc owner I'd love to find out how you finished this project up. And specifically interested to see what 8 inch woofer you used. Recent research indicates the current OEM passive radiator is now the SEAS Prestige SP26R (H9946) 10" Passive Radiator.

            Comment


            • #7
              Sorry, it remains an unfinished project. I never went further with the obelisks.
              I can't believe its been so long, with me always thinking I'll get to them in a month or so.

              Comment

              Working...
              X