Powered Subwoofer or Powered Woofer

[IBSTORMIN]

Just like a Submarine is a boat that goes under (sub) the water (marine) the Subwoofer was intended to go to frequencies below (sub) what the woofer is producing and should reproduce frequencies down to 20Hz or below. Most good speakers have a woofer that goes down below 35Hz. When a listed subwoofer only goes down to 35Hz you in essence only have a powered woofer. Just thinking out loud and would love to hear other opinions.

[Poultrygeist]

They lowest note on a bass violin is E which has a frequency of 41.2034446 Hz.

[IBSTORMIN]

The lowest note on a bass violin is E which has a frequency of 41.2034446 Hz.

I am not arguing. Your point is?

[Sir Terrence the Terrible]

They lowest note on a bass violin is E which has a frequency of 41.2034446 Hz.

Big concert bass drums have fundamentals that go below 20hz

[JoeE SP9]

Having speakers or in my case subs that are flat to 18Hz or so really does make a difference.
Most smaller speakers that have a listed response down to 35Hz rarely say how much lower in level the 35Hz portion is. Minus 6, 8 or 10dB at 35Hz puts that 35Hz in the pretty much inaudible category. A sub or any speaker that is minus 3dB at 35Hz will have a much better low end than a small bookshelf that's 8dB down at the same frequency.
Subs also tend to make the main speakers sound clearer and cleaner by taking the work of producing low frequencies away from them. This also increases headroom and allows higher volumes.

[audio amateur]

IF you're high passing the mains...

[JoeE SP9]

True. Unfortunately most inexpensive subs don't do any high pass filtering. I think they rely on people having an AV receiver. They have large and small settings for the mains that include high pass filtering.

[Nasir]

I would not get too concerned about specs and at which frequencies the woofer ends and the subwoofer starts. The idea is to blend their output in a manner which does not put heavy emphasis on the crossover frequencies ( otherwise known as the seamless integration of the 2 speakers, not an easy real life task!! ). From the physics of large speakers, the larger the speaker, the lower the supposed frequency response and the greater the amp power requirements. And to add to the mix, sealed ports for tighter bass and open ports for an even lower frequency response ......
From experience ( and perhaps luck ) an 8 inch ( 20cm) powered speaker is the minimum that I consider as a subwoofer as it will growl effortlessly around 40 Hz. The better designs go lower still, and I have read where people have been pleased by a 20 Hz response from their subs, my best sub manages a decent 30 Hz rumble!!! The powered sub has, as stated by JoeE SP9, the advantage of relieving your amp of the power greedy low frequency duties and cleaning up the sound of the main speakers by crossing over the otherwise unmanageable lower frequencies to the sub. To this end, either the sub has a built-in crossover accepting Left and Right speaker wires from the amp and also Left and Right speaker output wire connectors to feed to your main speakers ( sorry, the name of these speaker wire connectors escapes me at the moment, but someone will chip in with that ) OR your amp has a separate LFE output to feed the sub.
Maybe, I should have answered your question in a different manner. Some of us have spellbound by planar speakers ( Electrostatic and magnepan ) where the low frequency response of such speakers is best from 80 Hz and above, hence the need for powered subs is a must. Also, the combination of a low power ( 20 Watts per channel ) tube (Valve) amplifier with powered sub gave better results.