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Tweeters: Planar Magnetic/Planar Ribbon, Folded Ribbon/AMT, RAAL ribbon?

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  • Tweeters: Planar Magnetic/Planar Ribbon, Folded Ribbon/AMT, RAAL ribbon?

    What are the general characteristics/differences between the planar magnetic style tweeters ARX use as opposed to the Folded Ribbon/AMT style that martin logan, ADAM and Emotiva's Airmotiv use?
    About the same sound? any primary tradeoffs/drawbacks between the two?


    I'm looking to replace my 11yo Klipsch Promedia computer speakers that are starting to die....
    and my ARX A1B/A2rxc theater setup has kind of gotten me hooked on the neutral/transparent sound.
    Wondering if my ARX A1Bs would be serviceable for near-field listening as computer speakers and should just save for upgrading my LR Mains to the A5s when they come back in stock.. otherwise the computer/monitor speakers I've found that have ribbons are Airmotiv 4S/5s and Adam F5.

  • #2
    The direct answer to the question is that they're fairly close. Everybody has their preferences but in reality there's no dramatic difference in the class, device size for device size.

    There are three basic forms: True ribbon, Heil air motion transformer, and planar.

    The true ribbon is an expensive, potentially problematic, and frequently very high fidelity device. The true ribbon type suspends a metal foil between two powerful (large, heavy) magnets and passes a signal current through it.

    Being solid foil, the driver's impedance is very low and the circuit requires a matching electrical transformer. Connected directly the amplifier would see the ribbon diaphragm as a short or even as a fuse. Magnetics costs skyrocket and limit practical use.

    Heils are the folded types. They use a field of smaller magnets and an accordian-like motion of the radiating diaphragm. Voice coil length is increased while width is decreased so overall impedance rises and the amplifier connects directly. Drivers can be made quite small, and the speakers they go in can be manufactured inexpensively. Speaker designs more readily accept a tweeter with the more typical response and behavior profile.

    Planars are most like Heils. They've been around for about a half century and by now come in limitless forms between an inch and as much as six feet in length. They have the same approximate family of advantages as the Heils.

    Like all drivers, however, tweeters should be selected for the way they fit the design, and not because they're assumed to automatically improve any speaker they're used in. Exotic, unusual, and electrically, mechanically, or acoustically cumbersome drivers can easily overwhelm designs that would otherwise succeed. For this reason the flat tweeters whose responses replace those of domes are probably the most useful. Depending on their length, true ribbons can also have dispersion and in-use design problems for the overall loudspeaker - they dominate a speaker they're used in and may force how that speaker engineering works and sounds.

    The biggest advantages for consumer class products are that these devices are typically at least three to four times the acoustical size of a conventional 1" dome. This size correlates to a fairly proportional reduction in distortion. Heils and planars also present nearly resistive loads to amplifiers, which is a significant advantage.

    No one driver or driver type can transform an average loudspeaker into a great one. This point tends to get lost in the din, but it's an important one. All drivers must have some synergy if the entire design is to sound balanced.

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    • #3
      Thank you for taking the time to elaborate with concise objective information on the physical characteristics between them. It helps clarify the traits and applications and has greatly increased my perspective on how I evaluate the various products on the market.

      Having gone from Klipsch Promedia to nice IEM monitors to Athena, B&W, DefTech.. then after being a lurker on avsforum observing your posts, and deciding to take a chance on your Acculine for a clients setup. and finally getting myself some of your ARXs. It's been a continous learning experience.

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      • #4
        Just curious, what is the tweeter crossover frequency for the CHANE A1RX-C?
        Thanks!

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        • #5
          Originally posted by haulin79 View Post
          Just curious, what is the tweeter crossover frequency for the CHANE A1RX-C?
          Thanks!
          In the low 2kHz's, or where the overall design most benefits placing the crossover. Roughly where we'd also put a good dome crossover.

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