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Thread: System Test - Merry Ocarina Tony Hart / Vision On

  1. #11
    Join Date: Jan 2013

    Location: Bristol

    Posts: 6,843
    I'm Justin.

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    Looking at the TFFT I posted above it is easy to see the bulk of the energy is between 170-500Hz when the y-axis scale is measured.

    So I did a slow sweep pure tone input into the Apogees. At high volume, the long thin ribbon which handles mid-range and HF freaks out around 380Hz. Look the wavelength up for that frequency and it coincides with the length of the ribbon from the bottom clamp to a pivot about 90cm up that is made of foam. From this pivot the ribbon angles back (and the magnet angle with it) until it hits the top clamp.

    So basically when the ribbon sees a wavelength corresponding to its real physical length it freaks out at high volume. This will happen with any genuine ribbon I would imagine. Fortunately it is very narrow band, and the Ocarina track is the only one I have ever come across with enough energy and simplicity of tone (i.e. there isn't too much else going on) to make it noticeable at high volume.

    Placing a digital notch filter using JRiver's PEQ at 380Hz +/- 20Hz and a few DB down makes no audible difference when playing real music and calms the ribbon down. Realistically it isn't worth applying. Lest you are into Ocarinas at volume that is. In which case don't by a pair of Apogees!!!

    Do high volume frequency sweeps with most speakers and you will find anomalies/resonances. All speakers sin in one way or another and this is one minor flaw with the Apogee/ribbon approach. Experimenting with ribbon tension and pivot material may well be able to help minimise it. The ribbon tension in my current pair is the same as the previous pair and also equal to that used originally by Apogee. Set it too high and the ribbon movement gets restricted by the tension.
    Last edited by User211; 02-09-2015 at 15:36.

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