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Martin Logan / Jonathan Foulkes - SL3XC

This design arose out of my desire to have a center channel that could keep up with the Monoliths. While bass is well handled by the IB sub, the mid-bass region as well as midrange and highs, all suffered from power compression issues with prior factory designs. Basically, I needed a center that could play cleanly across the full spectrum at  and beyond 105dB SPL.

Since creating that level of output cleanly requires significant size, I am fortunate to be able to accommodate a large center behind my perforated, acoustically transparent screen.

I go into detailed design goals and parameters as well as full detailed description of the build process (with tons of pictures and measurements) on this thread over at the Martin Logan Club.

The result is an astoundingly coherent front soundstage. The blend of L/R with the new center is perfect. And its ability to play loud and clean is downright amazing.
If anything, it has better mid-bass performance than the Monoliths.

The specifications are:

  • System Frequency Response
    77 - 24,000 Hz +/-3dB
  • Electrostatic Frequency Response
    125-24,000 Hz +/- 2dB
  • Line Array Frequency Response
    77-2,000Hz +/- 3dB
  • Crossover Frequency - Using DBX DriveRack 4800
    ESL to Line array: 420 Hz at 24 dB per octave
    Line Array to Sub: 80 Hz at 24 dB per octave
  • Dispersion
    Horizontal: 30 degrees
    Vertical: 4' Line Source
  • Sensitivity
    88dB/1 watt/meter
  • Power handling
  • Supplied Amplifier Power
    ESL             - 800 watts
    Line Array   - 200 watts
  • Jonathan's recommended amplifier
    Sunfire Amplifier
  • Impedance
    ESL - nominal 4 ohms; minimum 2 ohms - Direct drive
    Line Array - 11 ohms
  • Weight
    154 lbs

3qtr View of SL3XC

This is an older pic of when I just set the speaker up. The entire wall behind them is now covered with RealTraps MiniTrap HF treatments to mitigate the rear wave.


ML Logo 


Installed on IB