(kicad_sch
  (version 20231120)
  (generator "eeschema")
  (generator_version "8.0")
  (uuid "b2c3d4e5-f6a7-8901-bcde-f12345678901")
  (paper "A3")
  (title_block
    (title "Active Crossover — Midrange Channel (LR4 Bandpass)")
    (date "2026-08-28")
    (rev "1.0")
    (company "DIY Active Speaker Project")
    (comment 1 "HPF@300Hz x2 + LPF@3000Hz x2 — Sallen-Key unity-gain OPA2134")
    (comment 2 "Copy this hierarchical sheet for Woofer (LP only) and Tweeter (HP only)")
  )

  (lib_symbols
    (symbol "Device:R"
      (pin_names (offset 0))
      (exclude_from_sim no) (in_bom yes) (on_board yes)
      (property "Reference" "R" (at 2.032 0 90) (effects (font (size 1.27 1.27))))
      (property "Value" "R" (at 0 0 90) (effects (font (size 1.27 1.27))))
      (symbol "R_0_1"
        (rectangle (start -1.016 -2.54) (end 1.016 2.54)
          (stroke (width 0.254) (type default)) (fill (type none))))
      (symbol "R_1_1"
        (pin passive line (at 0 3.81 270) (length 1.27)
          (name "~" (effects (font (size 1.27 1.27))))
          (number "1" (effects (font (size 1.27 1.27)))))
        (pin passive line (at 0 -3.81 90) (length 1.27)
          (name "~" (effects (font (size 1.27 1.27))))
          (number "2" (effects (font (size 1.27 1.27)))))
      )
    )
    (symbol "Device:C"
      (pin_names (offset 0.254))
      (exclude_from_sim no) (in_bom yes) (on_board yes)
      (property "Reference" "C" (at 0.635 2.54 0) (effects (font (size 1.27 1.27))))
      (property "Value" "C" (at 0.635 -2.54 0) (effects (font (size 1.27 1.27))))
      (symbol "C_0_1"
        (polyline (pts (xy -2.032 -0.762) (xy 2.032 -0.762))
          (stroke (width 0.508) (type default)) (fill (type none)))
        (polyline (pts (xy -2.032 0.762) (xy 2.032 0.762))
          (stroke (width 0.508) (type default)) (fill (type none))))
      (symbol "C_1_1"
        (pin passive line (at 0 3.81 270) (length 2.794)
          (name "~" (effects (font (size 1.27 1.27))))
          (number "1" (effects (font (size 1.27 1.27)))))
        (pin passive line (at 0 -3.81 90) (length 2.794)
          (name "~" (effects (font (size 1.27 1.27))))
          (number "2" (effects (font (size 1.27 1.27)))))
      )
    )
    (symbol "Amplifier_Operational:OPA2134"
      (pin_names (offset 0.254))
      (exclude_from_sim no) (in_bom yes) (on_board yes)
      (property "Reference" "U" (at 0 5.08 0) (effects (font (size 1.27 1.27))))
      (property "Value" "OPA2134" (at 0 -5.08 0) (effects (font (size 1.27 1.27))))
      (property "Footprint" "Package_SO:SOIC-8_3.9x4.9mm_P1.27mm" (at 0 0 0)
        (effects (font (size 1.27 1.27)) hide))
      (property "Datasheet" "https://www.ti.com/lit/ds/symlink/opa2134.pdf" (at 0 0 0)
        (effects (font (size 1.27 1.27)) hide))
      (symbol "OPA2134_0_1"
        (polyline (pts (xy -5.08 5.08) (xy 5.08 0) (xy -5.08 -5.08) (xy -5.08 5.08))
          (stroke (width 0.254) (type default)) (fill (type background))))
      (symbol "OPA2134_1_1"
        (pin input line (at -7.62 2.54 0) (length 2.54)
          (name "+" (effects (font (size 1.27 1.27))))
          (number "3" (effects (font (size 1.27 1.27)))))
        (pin input line (at -7.62 -2.54 0) (length 2.54)
          (name "-" (effects (font (size 1.27 1.27))))
          (number "2" (effects (font (size 1.27 1.27)))))
        (pin output line (at 7.62 0 180) (length 2.54)
          (name "~" (effects (font (size 1.27 1.27))))
          (number "1" (effects (font (size 1.27 1.27)))))
        (pin power_in line (at 0 7.62 270) (length 2.54)
          (name "V+" (effects (font (size 1.27 1.27))))
          (number "8" (effects (font (size 1.27 1.27)))))
        (pin power_in line (at 0 -7.62 90) (length 2.54)
          (name "V-" (effects (font (size 1.27 1.27))))
          (number "4" (effects (font (size 1.27 1.27)))))
      )
    )
    (symbol "power:GND"
      (power)
      (pin_names (offset 0))
      (exclude_from_sim no) (in_bom yes) (on_board yes)
      (property "Reference" "#PWR" (at 0 -6.35 0) (effects (font (size 1.27 1.27)) hide))
      (property "Value" "GND" (at 0 -3.81 0) (effects (font (size 1.27 1.27))))
      (symbol "GND_0_1"
        (polyline (pts (xy 0 0) (xy 0 -1.27) (xy 1.27 -1.27) (xy 0 -2.54) (xy -1.27 -1.27) (xy 0 -1.27))
          (stroke (width 0) (type default)) (fill (type none))))
      (symbol "GND_1_1"
        (pin power_in line (at 0 0 270) (length 0) hide
          (name "~" (effects (font (size 1.27 1.27))))
          (number "1" (effects (font (size 1.27 1.27)))))
      )
    )
    (symbol "power:+15V"
      (power)
      (pin_names (offset 0))
      (exclude_from_sim no) (in_bom yes) (on_board yes)
      (property "Reference" "#PWR" (at 0 -3.81 0) (effects (font (size 1.27 1.27)) hide))
      (property "Value" "+15V" (at 0 3.556 0) (effects (font (size 1.27 1.27))))
      (symbol "+15V_0_1"
        (polyline (pts (xy -0.762 1.27) (xy 0 2.54) (xy 0.762 1.27))
          (stroke (width 0) (type default)) (fill (type none)))
        (polyline (pts (xy 0 0) (xy 0 2.54))
          (stroke (width 0) (type default)) (fill (type none))))
      (symbol "+15V_1_1"
        (pin power_in line (at 0 0 90) (length 0) hide
          (name "~" (effects (font (size 1.27 1.27))))
          (number "1" (effects (font (size 1.27 1.27)))))
      )
    )
    (symbol "power:-15V"
      (power)
      (pin_names (offset 0))
      (exclude_from_sim no) (in_bom yes) (on_board yes)
      (property "Reference" "#PWR" (at 0 3.81 0) (effects (font (size 1.27 1.27)) hide))
      (property "Value" "-15V" (at 0 -3.81 0) (effects (font (size 1.27 1.27))))
      (symbol "-15V_0_1"
        (circle (center 0 0.635) (radius 0.127)
          (stroke (width 0) (type default)) (fill (type outline)))
        (polyline (pts (xy 0 1.27) (xy 0 0))
          (stroke (width 0) (type default)) (fill (type none))))
      (symbol "-15V_1_1"
        (pin power_in line (at 0 0 270) (length 0) hide
          (name "~" (effects (font (size 1.27 1.27))))
          (number "1" (effects (font (size 1.27 1.27)))))
      )
    )
  )

  (text "ROOT SHEET: Midrange LR4 bandpass. Hierarchical sheets below are copy-templates."
    (exclude_from_sim no) (at 25.4 25.4 0)
    (effects (font (size 1.27 1.27)) (justify left bottom))
    (uuid "troot1"))
  (text "WHY cascaded identical stages: two Butterworth Q=0.707 → Linkwitz-Riley 24 dB/oct."
    (exclude_from_sim no) (at 25.4 27.94 0)
    (effects (font (size 1.27 1.27)) (justify left bottom))
    (uuid "troot2"))
  (text "VERIFY: OPA2134 pinout (DIP-8 vs SOIC-8) and max supply ±18V before PCB."
    (exclude_from_sim no) (at 25.4 30.48 0)
    (effects (font (size 1.27 1.27)) (justify left bottom))
    (uuid "troot3"))

  (sheet (at 30.48 45.72) (size 40.64 25.4)
    (stroke (width 0.1524) (type solid))
    (fill (color 0 0 0 0.0))
    (uuid "sheet_hp1")
    (property "Sheetname" "HP1_300Hz" (at 30.48 44.45 0)
      (effects (font (size 1.27 1.27)) (justify left bottom)))
    (property "Sheetfile" "sk_highpass_stage.kicad_sch" (at 30.48 72.39 0)
      (effects (font (size 1.27 1.27)) (justify left top)))
    (pin "IN" input (at 30.48 50.8 180)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "shp1_in"))
    (pin "OUT" output (at 71.12 50.8 0)
      (effects (font (size 1.27 1.27)) (justify left))
      (uuid "shp1_out"))
    (pin "+15V" input (at 45.72 45.72 90)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "shp1_vp"))
    (pin "-15V" input (at 55.88 71.12 270)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "shp1_vn"))
    (pin "GND" input (at 50.8 71.12 270)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "shp1_gnd"))
  )

  (sheet (at 86.36 45.72) (size 40.64 25.4)
    (stroke (width 0.1524) (type solid))
    (fill (color 0 0 0 0.0))
    (uuid "sheet_hp2")
    (property "Sheetname" "HP2_300Hz" (at 86.36 44.45 0)
      (effects (font (size 1.27 1.27)) (justify left bottom)))
    (property "Sheetfile" "sk_highpass_stage.kicad_sch" (at 86.36 72.39 0)
      (effects (font (size 1.27 1.27)) (justify left top)))
    (pin "IN" input (at 86.36 50.8 180)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "shp2_in"))
    (pin "OUT" output (at 127 50.8 0)
      (effects (font (size 1.27 1.27)) (justify left))
      (uuid "shp2_out"))
    (pin "+15V" input (at 101.6 45.72 90)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "shp2_vp"))
    (pin "-15V" input (at 111.76 71.12 270)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "shp2_vn"))
    (pin "GND" input (at 106.68 71.12 270)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "shp2_gnd"))
  )

  (sheet (at 142.24 45.72) (size 40.64 25.4)
    (stroke (width 0.1524) (type solid))
    (fill (color 0 0 0 0.0))
    (uuid "sheet_lp1")
    (property "Sheetname" "LP1_3000Hz" (at 142.24 44.45 0)
      (effects (font (size 1.27 1.27)) (justify left bottom)))
    (property "Sheetfile" "sk_lowpass_stage.kicad_sch" (at 142.24 72.39 0)
      (effects (font (size 1.27 1.27)) (justify left top)))
    (pin "IN" input (at 142.24 50.8 180)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "slp1_in"))
    (pin "OUT" output (at 182.88 50.8 0)
      (effects (font (size 1.27 1.27)) (justify left))
      (uuid "slp1_out"))
    (pin "+15V" input (at 157.48 45.72 90)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "slp1_vp"))
    (pin "-15V" input (at 167.64 71.12 270)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "slp1_vn"))
    (pin "GND" input (at 162.56 71.12 270)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "slp1_gnd"))
  )

  (sheet (at 198.12 45.72) (size 40.64 25.4)
    (stroke (width 0.1524) (type solid))
    (fill (color 0 0 0 0.0))
    (uuid "sheet_lp2")
    (property "Sheetname" "LP2_3000Hz" (at 198.12 44.45 0)
      (effects (font (size 1.27 1.27)) (justify left bottom)))
    (property "Sheetfile" "sk_lowpass_stage.kicad_sch" (at 198.12 72.39 0)
      (effects (font (size 1.27 1.27)) (justify left top)))
    (pin "IN" input (at 198.12 50.8 180)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "slp2_in"))
    (pin "OUT" output (at 238.76 50.8 0)
      (effects (font (size 1.27 1.27)) (justify left))
      (uuid "slp2_out"))
    (pin "+15V" input (at 213.36 45.72 90)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "slp2_vp"))
    (pin "-15V" input (at 223.52 71.12 270)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "slp2_vn"))
    (pin "GND" input (at 218.44 71.12 270)
      (effects (font (size 1.27 1.27)) (justify right))
      (uuid "slp2_gnd"))
  )

  (wire (pts (xy 71.12 50.8) (xy 86.36 50.8))
    (stroke (width 0) (type default)) (uuid "w_hp1_hp2"))
  (wire (pts (xy 127 50.8) (xy 142.24 50.8))
    (stroke (width 0) (type default)) (uuid "w_hp2_lp1"))
  (wire (pts (xy 182.88 50.8) (xy 198.12 50.8))
    (stroke (width 0) (type default)) (uuid "w_lp1_lp2"))

  (label "AUDIO_IN" (at 25.4 50.8 0)
    (effects (font (size 1.27 1.27)) (justify right bottom))
    (uuid "lbl_in"))
  (label "MID_OUT" (at 243.84 50.8 0)
    (effects (font (size 1.27 1.27)) (justify left bottom))
    (uuid "lbl_out"))

  (wire (pts (xy 25.4 50.8) (xy 30.48 50.8))
    (stroke (width 0) (type default)) (uuid "w_in"))
  (wire (pts (xy 238.76 50.8) (xy 243.84 50.8))
    (stroke (width 0) (type default)) (uuid "w_out"))

  (symbol (lib_id "power:+15V") (at 45.72 40.64 0) (unit 1)
    (uuid "pwr_p")
    (property "Reference" "#PWR10" (at 45.72 40.64 0) (effects (font (size 1.27 1.27)) hide))
    (property "Value" "+15V" (at 45.72 36.83 0) (effects (font (size 1.27 1.27))))
    (pin "1" (uuid "pwr_p1")))
  (symbol (lib_id "power:-15V") (at 55.88 76.2 0) (unit 1)
    (uuid "pwr_n")
    (property "Reference" "#PWR11" (at 55.88 76.2 0) (effects (font (size 1.27 1.27)) hide))
    (property "Value" "-15V" (at 55.88 80.01 0) (effects (font (size 1.27 1.27))))
    (pin "1" (uuid "pwr_n1")))
  (symbol (lib_id "power:GND") (at 50.8 76.2 0) (unit 1)
    (uuid "pwr_g")
    (property "Reference" "#PWR12" (at 50.8 76.2 0) (effects (font (size 1.27 1.27)) hide))
    (property "Value" "GND" (at 50.8 80.01 0) (effects (font (size 1.27 1.27))))
    (pin "1" (uuid "pwr_g1")))

  (text "Copy tips: Woofer = two LP sheets @ 300 Hz only. Tweeter = two HP sheets @ 3 kHz only."
    (exclude_from_sim no) (at 25.4 90.17 0)
    (effects (font (size 1.27 1.27)) (justify left bottom))
    (uuid "tcopy"))
  (text "Component values: run python calculator.py 300 3000 — see active-crossover/docs/BOM.csv"
    (exclude_from_sim no) (at 25.4 92.71 0)
    (effects (font (size 1.27 1.27)) (justify left bottom))
    (uuid "tvals"))

  (sheet_instances
    (path "/" (page "1"))
  )
)