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  • Adding tweeters - need advice

    After many weeks tending to other things and a visit from the local Rodgers tech - I am continuing on my Exeter 700.
    The instrument is connected to a Johannus pipe speaker top unit for the main manual output (pedal ch4 is on its own dedicated subwoofer).
    The Johannus speaker is basically 5 speaker cabinets connected together with ornamental wood slats on the facade to provide the impression of pipes.
    Inside - 4 of the five cabinets have 1 Fane 8" full range speaker and the remaining cabinet has a Fane 12" speaker.

    Problem - the speakers have no sparkle / brightness to them. For giggles I connected some Polk Rti A6's had around the house and the difference was dramatic.

    My intended solution - add tweeters to the Johannus unit. There are five additional mounting plates for adding additional speakers. Question is what kind?
    I have researched the forum and looked at Parts Express and MCM and the choices are mind boggling. Does anyone have suggestions as to which tweeters they might use in my situation?

    Thanks - Erik

  • #2
    I tend to recommend a phenolic ring tweeter, specifically this model: https://www.parts-express.com/grs-pr...8-ohm--270-252

    * It has a well behaved response curve that tapers off gently above about 15 kHz, which is a good situation for organ speakers. It won't get out of hand.


    * It's resonance is low enough that it is good down to about 2 kHz with a 12 dB/octave crossover--or OK above 4 kHz with a 6 dB per octave crossover

    * It's a rugged design that won't be prone to self destruction if it suffers a little abuse.

    Walker Technical Company used this type of tweeter in their speaker designs that were often used with Rodgers Organs of the late analog era, such as yours.

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    • #3
      What about piezoelectric tweeters? I probably do not have the ear to carefully evaluate them but I believe that one of their prime advantages is that they ignore bass and lower frequencies, hence no need for a crossover network (or even a capacitor) to block low frequencies.
      Roland Atelier AT-90s, AT-80s, AT-70, 30, and 15. Roland VR-760 combo
      Yamaha S-90, Kurzweil PC-3x, Casio Privia PX-330, Roland E-80, G-70, BK-5, Leslie 760, 820
      Moved on:
      Allen 3MT/Hauptwerk, Technics GA1, Yamaha HX1, AR80, numerous Hammonds, including 2 M's, an L, 2 A-100's, XP-2, XM-1/1c, & an XK-3. Roland Atelier AT-30, 60r, 80, & 20r(2 units), and a slew of Leslies (147, 142, 760, 900, 330).
      Korg Triton Le-61, Casio Privia PX-310 & 110, and Kurzweils: PC-2x, SP-88, Pro-III, K1000

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      • #4
        Any good speaker design with piezo tweeters (and that may be an oxymoron--"good" and "piezo") uses a crossover network because even though the tweeters do not respond significantly to bass frequencies, the bass could cause intermodulation distortion, and the level of the tweeter needs to be matched to the rest of the system. Their response is not usually very smooth.

        Most speaker builders stay away from piezo tweeters--the cost of building your own system is high enough that builders are looking for very good performance, and piezo's really don't offer that, and saving a few bucks on the tweeter is a small portion of the system cost.

        They are good for being cheap but nothing else.

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        • #5
          Toodles wrote:

          "Most speaker builders stay away from piezo tweeters--the cost of building your own system is high enough that builders are looking for very good performance, and piezo's really don't offer that, and saving a few bucks on the tweeter is a small portion of the system cost.

          They are good for being cheap but nothing else. "


          As a lifelong audiophile, I can only say that I agree with this 100%. Totally and absolutely. Toodle man speak truth.

          Tony
          Home: Johannus Opus 370

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          • #6
            Tony,

            Thanks for the affirmation!

            By the way, though the phenolic ring tweeter is "old fashioned" in its design, it was very popular in the 1960's and 1970's before the dome tweeter became the "default" approach to tweeter design. Its common use back then was because it performed quite well with no particularly pronounced faults.

            Domes are still popular for tweeters, and are fine drivers, but they are a little less rugged than the phenolic ring, and thus my recommendation for organ speakers where abuse is sometimes encountered with people connecting speakers and disconnecting them while under power.

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            • #7
              Erik - I bought 11 of the tweeters Sir Toodles mentioned above for my Allen, and they sound nice and bright in the reeds cabinet and blend in really well in the other cabinets, including the rotating one. They look good, too.
              -- I'm Lamar -- Allen TC-4 Classic -- 1899 Kimball, Rodgers W5000C, Conn 643, Hammond M3, L-102 - "Let no man belong to another who can belong to himself." (Alterius non sit qui suus esse potest​ -) ​Paracelsus

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              • #8
                By the time I got into audio in the early 80s done tweeters were already prevalent in high end speakers, so I was unfamiliar with them. Looks like they would be a decent replacement if keeping the old speakers.

                IMO if speakers need a lot of work then it might start to make sense replacing the speakers altogether with something more up-to-date. Even the cheapest speakers being produced today are mostly better than the state-of-the-art stuff from the late 70s. In my case there wasn't any external speakers with my organ so the choice was made easier!

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