Frequencies:
Most subwoofers have a frequency response range of 30Hz to 200Hz
For normal young ears the entire audible range of sounds extends from about 20 to 20,000 hertz
Music can go as low as 18 Hz (which is about the pitch of the lowest rumbling notes on a huge pipe organ with 32-foot bass pipes)
Musical Instruments with low bass at Sound in tech.Frequencies within the range of 4 to 16 Hz are felt but not heard.
Piano A0 (28 Hz) to C8 (4,186 Hz) Bass C1 (33 Hz) to C5 (523 Hz) Picolo C5 (523 Hz) to B7 (3,951 Hz) Guitar (Bass) 4 string E1 (41 Hz) to C4 (262 Hz) Barritone Sax C2 (65 Hz) to A4 (440 Hz) Harp (28 Hz) to (32,000 Hz) Tuba (45 Hz) to (380 Hz) Large Pipe Organ with a 32 foot stop in the pedal (16 Hz)
Size:
See: 10" vs 12" Subwoofers (The Real Difference) | BoomSpeaker
Size is the speaker element not the box.
10" subs sound punchy while 12" subs sound boomy.
A 10" sub has less distortion
A 12" sub is louder and better for a large room.
Examples: (Manufacturer specs - List response but not SPL(dB)
10" Polk Audio PSW10 $159 40-160 HZ 10" Elac SUB1010 $130 37-200 Hz 10" JL Audio 10W3v3-4 $380 25-250 Hz 10" Klipsch Reference R-10SW $200 32-120 12" Polk Monitor XT12 $350 24-160 Hz 12" ELAC Debut 2.0 SUB3030 $650 25-150 Hz 12" Jamo C912 $205 29-125 Hz 15" Kicker 45L7R152 $429 20-100 Hz (element only no enclosure) 15" Dayton Audio RSS390HF-4 $270 18 to 800Hz (element only no enclosureAre frequency responses specifications consistent between manufacturers:
Power:
Higher end subwoofers have their own powered amplifiers.
'Passive subwoofers' have a subwoofer driver and enclosure, but they do not include an amplifier.
Crosover:
Crossovers limit the frequency response of a speaker. Subwoofers typically employ a crossover called a "low-pass filter." A low-pass filter only permits source frequencies of a certain hertz and below to reach the subwoofer.
Professional concert sound system subwoofers typically operate below 100 Hz,
THX-certified systems operate below 80 Hz.
Erin's Audio Corner had the most comprensive testing I could find. Erin recommends multiple subwoofers to provide a smoother in-room response. YouTube presentations: Budget <$200 10 inch subwoofers | Erin's Audio Corner 10" down to A 10" subwoofer is good with bookshelf 10" speakers 1. Elac SUB1010 $129 powered 60 w box 12" w 14" 2. Polk sw10 $150 Budget ($175-$300) 12 inch subwoofers | Erin's Audio Corner Down to 30Hz 1. Infinity R12 $175 (not available 2022) 2. Jamo C912 $250 3. Eclipse 12W 29HzÐ150Hz Pay $400-$600 to go lower than 20 HzLinks: