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  • Phenolic Ring Tweeter

    Posted by TVOR-Ceasar on August 22, 2023 at 3:48 am

    So years ago, back when all I had was a calculator, notebook and pencil, I had a friend who had a pair of old Bose 501 (first gen) speaker what had been in barn storage for 20+ years. He knew I was into the nuts and bolts of speakers and he asked if I could fix them up. I said I’d sure try. Measured the inside of the woofer box and size of the woofer, grabbed my MCM catalog and went to town. I settled on Pioneer drivers. The 10″ was a perfect match for the box, and I got the same size phenolic ring tweeters as was in them. The crossover was nicely situated, and I bought new, exact replacements. The Pioneer drivers were such a huge upgrade. He always remembered the bass was “floppy and soft. Now it was tight, strong and authoritative. The top end was quite spacious and very easy to listen to. https://www.hifiengine.com/manual_library/bose/501.shtml

    Now, those tweeters were just like the GRS tweeters at parts express https://www.parts-express.com/GRS-PRT-8-Phenolic-Ring-Tweeter-8-Ohm-270-252?quantity=1

    I think they’re pretty darn nice as they are. Take a look at them. The graph is a bit humped from 1k into 2, but the rest is actually quite fair. I’d use them again.

    TVOR-Ceasar replied 1 month ago 2 Members · 5 Replies
  • 5 Replies
  • Toids_DIY_Audio

    Administrator
    August 23, 2023 at 6:15 am

    That is pretty cool. I like that they even are marketing them as tweeters that are designed to fit into retro gear. It would be kind of neat to take an old set of speakers like the Bose and do some before and after tests with replacing the speakers. I bet you could really get those 901’s to sing. Like you already did.

    • TVOR-Ceasar

      Member
      August 23, 2023 at 1:55 pm

      If you look at the HiFiEngine link, they don’t show these, rather, they show standard paper tweeters. His set had the Phenolic ring tweeters from the factory, 1 on each front corner.
      Unfortunately, his woofer surrounds were completely gone, and the spider was so soft that the cones acted like they were on a light spring – “boing, boing, boing”. Real loose.

      IIRC, the 10″ woofer compartment was 1.3 CF sealed, and the upper part had a solid back (as shown) , but I think his tweeters were angled in so the sound bounced off the back and through the sides toward the front. plus, all they had for a crossover was just a single cap. I should still have my notebook with all that info in storage. I’ll dig it out soon. It was, after all, somewhere around 25-30 years ago.

  • TVOR-Ceasar

    Member
    September 3, 2023 at 1:23 am

    What’s scary is there’s a pair of 501’s on FB Marketplace, within 40 minutes of me for $200. If I had the room, maybe.

    They are original, except the woofers have been refoamed. Damn, I wish I had a place for them.

    In addition to the GRS tweeter, the GRS 10PR-8 woofer seems like it’d be just about perfect as a replacement. That means that full replacement of all drivers would be $112, plus whatever the caps come to. Say all in, $120. Add in some MDF, a bit of 1 to 1.5″ stock for the tweeter mounts, and some grill cloth. IIRC, the grillcloth was glued to a set of hardboard cutouts that used velcro to hold it onto the speaker.. so you could do a 501 gen 1 build for around $250 a pair, and most likely be a vast improvement.over the originals.

    Man, I really need to find my notes on the originals.

    • This reply was modified 3 weeks, 6 days ago by  TVOR-Ceasar. Reason: Spelling issues due to typing on phone rather than computer keyboard, most noticeably changed "u really need" to "I really need"
    • Toids_DIY_Audio

      Administrator
      September 4, 2023 at 3:46 am

      I beleive everything is backed up. I am just trying to figure out hwo to import them correctly. I’ve been really busy with both my birthday and anniversary. And we may have snuck away for a Gatlinburg vacation 😆 Suffice to say, I’ve been really busy.

      I always look at those older speakers and think, man I should pic them p. But I think you it the nail on the head, you never really know what someone has done to them. If they did anything, did they do it properly? It can be a tough call for sure.

      I think I need to design a pair of Golden Ear speakers. I have always wanted some, but don’t want to buy them….Or a definitive Tech style speaker…..You knwo, since we are talking aobut older speakers….Although< i guess Golden ear really isn’t that old.

    • TVOR-Ceasar

      Member
      September 4, 2023 at 4:27 am

      Sorry, I meant to say ” I really need to find my notes on the originals. “
      The I and U are right next to each other and I was on my Phone – tiny buttons n fat thumbs.

      We went away a few days early for my birthday (last Sunday in August) and “may have” gone to Springfield MA for a 2 day-er. 😁