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It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
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From Minidsp to dsp408

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  • From Minidsp to dsp408


    Got the homework to a manageable point due to time off around the holiday and decided to play with the dsp408 for a while before heading to the lake for some fishing.



    For the most part, physically copied the filter slopes, timing, peq settings from the minidsp to the dsp408. It sounds different but the results are pretty darn close, at least for one on axis measurement. I'm thinking off axis should remain the same since the filter slopes are the same.


    The hum is bothersome. Probably a ground loop somewhere but have yet to figure it out. There was a little bit of hiss/tweety bird with my ear near the tweeter with the minidsp in the system, but the hum with the dspp408 in the system just too much.


    Notice how the treble is down about 4db in the first trace (light blue). To my ears it doesn't sound that dark but the room they reside in is about 24'x26' with a low and multi-angled ceiling, all sheetrock plus hardwood floor. A clap of the hands tells just how live and bright the room is.


    Light blue trace is the baseline minidsp that I've been listening to for time. The brunt orange and lime green are the newly constructed dsp408 filters. Huge room nodes around 140 and 40/50hz.

    Another thing that the minidsp does that I haven't figured out with the dsp408 is a subsonic filter. I like bass heavy music, deep synth dubstep type of music sometimes played at as loud as it will go levels. Having the ability to start a steep subsonic filter under 20hz. is a bonus with those ported rs225s. They make the awfullest sound when they unload and bottom.

    1/24th smoothing.
    Click image for larger version

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    http://techtalk.parts-express.com/fo...khanspires-but
    http://techtalk.parts-express.com/fo...pico-neo-build
    http://techtalk.parts-express.com/fo...ensation-build

  • #2
    The hum you're hearing is likely because you have inputs routed to outputs that aren't connected to anything. For example, if you only have a connection to IN1, but you have IN2 routed as well that isn't connected to anything, you might hear a hum. If you route IN3 and IN4 as well, the hum will increase in volume. The hum should go away if you disable these unused inputs. It also ought to go away if you disconnect the USB cable. Please let us know if this isn't the case.

    Sorry to say there is not a way to do subsonic filters in the way you would like. The only way I could think to do anything like this would be if you do a high-pass filter at 20 hz at 24dB/oct, and then try to mess with the EQ to get ~20hz bass back up where you want it to be. I'm not sure how well you could get this to work.

    Thanks for sharing your measurements. I wonder what the cause of the dip in the blue trace is.

    Parts Express Engineer

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    • #3
      Here are the settings. Six inputs and six outputs are in use.

      Click image for larger version

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      http://techtalk.parts-express.com/fo...khanspires-but
      http://techtalk.parts-express.com/fo...pico-neo-build
      http://techtalk.parts-express.com/fo...ensation-build

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