Compare Thunder Class D Amplifiers   Model Thunder1501D Thunder801D Thunder421D Thunder311D Thunder251D 2 Ohm Load 1000 w x 1 500 w x 1 300 w x 1 200 w x 1 160 w x 1 4 Ohm Load 500 w x 1 250 w x 1 150 w x 1 100 w x 1 80 w x 1 Bridged 4 Ohm Load           2 Ohm Load 1500 w x 1 800 w x 1 420 w x 1 310 w x 1 250 w x 1 4 Ohm Load 750 w x 1 400 w x 1 210 w x 1 155 w x 1 125 w x 1 Bridged 4 Ohm Load           Hi Level w/ Smart Engage   X X X X Low Level X X X X X Input Select           Hi/Low @ 85Hz           Hi Pass @ 85Hz           Low pass @ 85Hz       X X Hi/Low @ 40Hz-200Hz           Low Pass @ 40Hz-200Hz X X X     Low Pass Only X X X     Full Range Only       X X Variable Hi, Low or Full Range           Compression Circuitry X X       ThunderEQ X X X X X EBC2 Port X X X     With ISO Feet 17.8" x 9.75" x 2.1" 11.5" x 9.75" x 2.1" 9.4" x 9.75" x 2.1" 8" x 9.75" x 2.1" 8" x 9.75" x 2.1" 45.3cm x 24.8cm x 5.3cm 29.3cm x 24.8cm x 5.3cm 23.9cm x 24.8cm x 5.3cm 20.4cm x 24.8cm x 5.3cm 20.4cm x 24.8cm x 5.3cm