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1936Re: [SpectrumLabUsers] Processing Live audio

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  • wolf_dl4yhf
    Apr 11, 2014
      Hi there,

      Am 11.04.2014 08:07, schrieb mosaicmerc@...:

      Hi all:
      1st post:
      I have a challenge to mic a PA system installed INSIDE of a caribbean steel drum instrument with the mic no more than 18" behind the speaker IN the base of the drum. I am using a KAM RT1 mic capsule into a NE5532 opa tone control preamp and then into a ClassD 40W amp driving an 8" mid woofer. Audio spectrum of interest is about 300Hz thru 6000Hz. Both the mic and the speaker enclosure are mounted via custom made spider mounts to isolate direct acoustic transfers. The drum 'skirt' is about 33" deep with the tenor pan at the top.

      All's well except that feedback is virtually unavoidable, even at low vol. levels. I am limited in mic location and speaker location, so the inverse square law can't help much. Freq. seems to be around 250 hz by ear. Fiddling with the tone controls helps a bit.

      I am hoping that the SL s'ware can allow me to view what the mic is seeing, realtime, during the feedback and perhaps optimize notch filter (s) to enable at least some reasonable amplification.

      I have access to both a vintage 2GB ram, P4 2.8GHz, Asus 800Sx mobo, XP SP3, PC and a more recent 16GB ram, FX6100 CPU, Win 7, SP1,  ASUS machine with realtek HD audio.

      I am hoping for advice on setting up SL to accept the audio from the preamp, process it and output to the ClassD amp to do 'live' compensation.

      There is one big issue I see, which may be a show stopper:
      The delays caused by the audio buffering, and -most important- the FFT size used by the FFT-based audio filter will introduce a delay of several dozen (or even a hundred) milliseconds between analog in- and output. That delay is (mostly) dictated by the maths, not by the CPU speed.

      A good starting point would be the preconfigured setting 'Sferics, Tweeks, Whistlers with filtered audio output'. It can be invoked through the 'Quick Settings' menu.

        Wolf .

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