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Designing an open back midrange speaker

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  • PWR RYD
    replied
    For midrange duty there is no need for high Qts or even 0.6 - 0.8 as suggested.

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  • hitsware2
    replied
    Same driver requirements as O.B. ( high Qts (as noted) )
    If the length of the pipe becomes ~> than the diameter ,
    or the proportion deeper than a square ( for a box )
    then pipe resonances start to manifest.
    The diameter + the depth becomes the 1/2 wave cancellation
    dimension .

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  • Chris Roemer
    replied
    Ideally to run a driver w/out a box behind it, I think you pick one w/a Qts near 0.70 (maybe in the .6-.8 range).

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  • a4eaudio
    started a topic Designing an open back midrange speaker

    Designing an open back midrange speaker

    I am considering attempting to design an open-back midrange speaker. This would have a tunnel through the cabinet that is open on the back, not just an open-baffle.

    I have searched the Internet quite a bit before posting, but if there are any good resources that you know of, feel free to point me in that direction. I have found very little on designing an open-back midrange speaker, most of what comes up are opinions on open vs sealed. I am aware of the Finalists and Statements that are open-back speakers, but there are no detailed descriptions of how the cabinet and crossover decisions were determined.

    So to start:
    1. Are there certain T/S parameters that suggest a driver is a good or bad candidate for an open-back design?
    2. How is the optimal tunnel width determined (assuming a circular pipe) - use something like 1" larger than the driver diameter or rely on trial and error? (For example, I know the Statement IIs use a 5" tunnel for a 4" driver and the Finalists use a 6" tunnel for a 5" driver.)
    3. How is the optimal tunnel depth determined? This would be tough to do based on trial and error as I need to build the cabinets before measuring. The Statement IIs are 16.5" deep and the Finalists are 15.5". If I just used 16" and figure out step 4 below, will the crossover take care of the details or does this need to be figured out more precisely beforehand?
    4. Is there a specific way to measure the frequency response and then use the FRD files in simulation software (PCD) in the normal fashion? Or (i) is it going to be much more trial and error in a real room environment to pick up the rear reflections; or (2) some kind of mathematical transformation of the measured FRD? (I read John K's method for measuring for dipole speaker design, but that doesn't seem to apply exactly to an open-back midrange design. Although admittedly it could apply, as I didn't understand all of the details.)
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