Fixing a DT250-250

Discussion in 'Modifications and Tweaks' started by spoony, Jun 28, 2016.

  1. spoony

    spoony Spooky

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    Thanks to our forum member @Psalmanazar I recently got my hands on an unbalanced DT250-250 for free and attempted to find a simple fix to its problems, here's the stock measurements (solid plate coupler, no compensation):

    dt250-stock.png

    It sounded bad.
    Here's what I came up with:

    Fix the channel imbalance

    Materials:
    • Electrical tape
    • Flat head jeweler screwdriver
    • 1-2mm thick foamie / craft foam
    • Scissors
    1. Disassemble the cable connector on the left cup.
    2. Cut a small piece of foamie (~1" side square) and stick it through the connector pins, then trim the excess material around the connector like this:
      IMG_20160628_193054.jpg
    3. Cut a small piece of electrical tape and place it over the connector screw opening on the cup like this (no need to poke the hole, you can do that with the screw while reassembling):
      IMG_20160628_193208.jpg
    4. Reassemble the cable connector:
      IMG_20160628_193338.jpg
    Here's the resulting FR:
    dt250-balanced.png

    Much better, channels are balanced but kinda lean sounding, I wasn't entirely happy with the result.

    Fix the frequency response

    Materials:
    • ~1mm thick rubberized microfiber cloth for cleaning glass (I used this).
      Note: ~1mm felts or foams should work as well, no guarantees on the resulting bass elevation, though.
    • Compass
    • Ruler
    • Scissors
    • Tape
    1. Remove the earpad assembly from both cups by pulling along the edge firmly, it should look like this:
      IMG_20160628_194126.jpg
      (Notice the depressed ridge where the stock foam sits, you will use this a template to make a sealing gasket out of a cloth/felt ring)
    2. Measure the inner and outer diameter of said ridge and trace a template using your compass tool on the piece of cloth / felt / whatever. Cut said template, it should look somewhat close to this:
      IMG_20160628_194054.jpg
    3. Mount the ring over the backside of the assembly like this:
      IMG_20160628_194219.jpg
    4. Place the foam over the gasket:
      IMG_20160628_194236.jpg
    5. Do the same for the other cup and carefully reassemble, making sure that neither the gasket or foam gets displaced during the installation.
    Here's the resulting FR:
    dt250-fixed.png

    Balanced and full sounding
     
    Last edited: Jun 29, 2016
  2. spoony

    spoony Spooky

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    Going by the FR alone it would seem that the pair should sound sorta bassy and midrangy like the M50x does, but that's not the case, the seal around the head is not as tight as this rig and this driver is very sensitive to coupling / pressurization, here's a take with my ear-mounted rig that better reflects what I'm hearing:

    DT250-250 Fixed (ear).png

    Pay no mind to the dip at 6 KHz, it's a measurement artifact.

    There are several ways to achieve a lower/greater bass boost, you can use more permeable materials instead of the microfiber cloth to lower the boost, or make an incomplete (not a whole ring) gasket to let some of the pressure escape in a controlled fashion, or use a better sealing material like closed-cell foam or rubber to have a greater boost.

    Happy modding.
     
    Last edited: Jun 29, 2016
    nehcrow, SpaceLaser, Riotvan and 2 others like this.
  3. numbercube

    numbercube Acquaintance

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  4. spoony

    spoony Spooky

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    I'm glad it's working out.
     
  5. JayNYC

    JayNYC Rando

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    @spoony this is a fascinating discovery. can you help explain WHY the foam+electape mod fixes a channel balance issue? From what I can tell, it makes the cable sit a little further away in the pin holes and removes a tiny amount of play between the cable connector and the frame.
     
  6. spoony

    spoony Spooky

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    The connector play allows more airflow between the pins into the cup chamber, it acts as a port reinforcing the lower frequencies. The foam is a lid or gasket to this 'port'.
     

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