RTO XP-12x (xpider)

Autohifi subwoofer

Manufacturer parameters
  • Diameter: 12" (30cm)
  • Power (W): 400/800
  • Impedance (Ohm): 4
  • Sensitivity (db/1W): 88
  • Qts: 0,586
  • Price: 43
  • Diaphragm: coated paper
  • Basket: plech
  • Magnet: single
Measured parameters
  • Fs = 38.47 Hz
  • Re = 3.60 ohms[dc]
  • Le = 2234.06 uH
  • Qt = 0.66
  • Qes = 0.73
  • Qms = 7.57
  • Mms = 106.43 grams
  • Cms = 0.000161 m/N
  • Vas = 46.24 liters
  • Sd= 452.39 cm^2
  • Bl = 11.301346 Tm
  • gamma = 106.2 N/A.kg
  • ETA = 0.35 %
  • Lp(2.83V/1m) = 91.00 dB (Sensitivity 88dB)
  • EBP=53 Hz (bassreflex/sealed)


Tuning - adding another ferrite ring on rear pole piece
  • Fs = 38.25 Hz
  • Re = 3.60 ohms[dc]
  • Le = 2174.22 uH
  • Qt = 0.48 (-0.18)
  • Qes = 0.53 (-0.20)
  • Qms = 6.04 (-1.53)
  • Mms = 94.57 grams
  • Cms = 0.000183 m/N
  • Vas = 52.61 liters
  • Sd= 452.39 cm^2
  • Bl = 12.475436 Tm (+1.17)
  • gamma = 131.9 N/A.kg (+25.7 N/A.kg)
  • ETA = 0.54 % (+54.3%)
  • Lp(2.83V/1m) = 92.88 dB (Sensitivity 90dB) (+2dB)
  • EBP=72 Hz (bassreflex/sealed)


Car subwoofer so cheap, that you can't expect any miracles. Motor is quite weak for its size, together with low suspension compliance you get quite high Qts, which makes this woofer not suitable for bass-reflex.

front side Basket and magnet