precision ASP LX521®.4


New: Cascaded ASP for LX521.4 v2.0

Widely optimised circuit.

Circuit adaption available -on request- for upgrade driver LINKWITZ 22MG



SKU: pASP LX521.4 Categories: , ,


Siegfried Linkwitz: “An optimum crossover filter topology should be the starting point when the outputs from multiple drivers with different frequency responses and sensitivities need to be combined for a flat acoustic response.” (In “Crossover Topology Issues”)

A new product generation of ASP for LX521.4 was the opportunity to start circuit design with optimum cascaded topology. Furthermore, CAD optimisation in filter design allowes a reduction in filter stages. ASP LX521.4 v2.0

Some basic considerations, see “Crossover Topology Issues” on

parallel (typical), summing errors:

cascaded plus all-passes (ideal) leads to perfect summing:


  • Generally, the cascaded ASP LX521.4 generates the same filter (magnitude) curves as before. Now with improved phase coherence among all channels
  • The cascding of the 120Hz high pass relieves the 10cm HiMid driver in the 200Hz region and below.
  • Topology theory New edition V2.0 with cascaded circuit topology, same magnitude filter curves, improved phase coherence between all channels.
  • Reduced noise levels
  • Reduced distortion
  • CAD based optimised filter blocks (F,Q,Gain)
  • Parallel filter blocks at critical locations reduce noise and distortion further by a factor √2 . Furthermore, it improves inter channel matching by √2
  • Shortest feedback loops minimize stray capacitances, stray inductances and external interference pickup.
  • Newest Generation, High Performance Audio OpAmps (OPA 1656 etc.)
  • Dedicated ground returns.
  • Tightly specified 1% capacitors with lowest distortion figures (eg polypropylene dielectric) and 0,1% metal thin film precision audio resistors. This allows 20x better inter-channel matching.
  • Balanced signal input for maximum common mode rejection
  • 3-step rumble filter for turntable users: off – med – hi.
  • Input gain increase by 12dB selectable (install jumper).
  • Optimised gain structure in woofer channel.
  • Smart power supply decoupling with feed-tru capacitors and large local buffer capacities.
  • +/-13V rails, from ultra low noise LDOs with additional CMC filtering, effective up to the MHz range (especially useful for SMPS use and their common mode spikes).
  • DIN 5-pole power plug compatible with MeanWell desktop PSU.
  • Slim design. Massive 3mm full aluminum case with stainless steel front plate: ca. 44 x 36 x 5,5 cm.
  • Dedicated case grounding point (M4 screw).
  • Neutrik XLR input and output plugs. XLR-RCA adapter cables are optionally available available in our webshop.
  • On request, please specify when ordering: Circuit adapted for the new LoMid driver LINKWITZ 22MG. 

Additional information

Weight6 kg