frequency range for instrument vs speaker

Agreed!

****If the article is correct, only wind and string instrument can create undertone. ****

Yes, and we all know how authoritative Wikepedia is. And no, not just those instruments can create undertones.

The Wikepedia article is (as usual) very incomplete. The production of undertones does not require special playing techniques. They can (and are) be produced by the acoustic interactions of two or more fundamentals. In the example that I described, no special techniques were
needed nor used. Undertones occur naturally as part of the harmonic texture of music. They add timbral complexity to music.

****I tend to agree that below 30Hz is not really musically relavant. ****

Really?

****Sure, it adds ambience in some cases. By the low 20s it is more felt than heard. It is an awesome experience to hear a large pipe organ in a large cathedral. I have never heard that reproduced electronically 100%.
Perhaps it would take a room nearly as big as a cathedral to do it. The 16ft pedal on the pipe organ just makes a pressure and creates a certain mood and is always a relief when that low frequency sound ends. I think that is part of the mood too. I think some experiences like being in front of a large pipe organ need to be experienced first hand.****

Sounds like musical relevance to me. Below 30hz reproduction may not be absolutely necessary, but it is clearly relevant and adds a great deal.

How did that happen? The Audiogon gremlins strike again. I didn't resubmit that post. Nonetheless, sorry.

06-22-12: Onhwy61
I think Frogman is correct, but it should be put into perspective. Suppose you were an audiophile with limited funds. Would you be better off pursuing bass response down to 20Hz, or compromise at 50Hz (with room reinforcement) and put more money into going for a better quality midrange and treble? Unless you're an absolute bass fanatic the answer is self-evident.

It's only "self-evident" to those eager to sacrifice an octave of the music for a little extra refinement. Actually, different music-loving audiophiles split up their priorities and budgets in different ways, and full range frequency response is one of them. All the imaging and transparency in the world can get annoying over time if a conspicuous part of the pitch spectrum is missing.

I think there's a strong case to be made for making a pair of powered subwoofers part of a speaker budget. Not because I'm a bass freak, but because it may be a smarter way to split up the frequency range--and the money. These days there are some stupendous stand-mounted speakers at $3K or less, with transparency, excellent dispersion and therefore uniform power response, treble extension, soundstage and especially pinpoint imaging.

At some point when you build a passive loudspeaker system and you go for full range, a lot of the money is spent on cabinet rigidity and damping to keep the big woofer from smearing the rest of the sound emanating from the higher drivers. With separate subs it's easier to retain the transparency and imaging of the mini-monitor while adding a low frequency foundation that does not cost too much on one hand and doesn't smear the rest of the sound on the other. How many of us have heard a line of speakers where the stand-mounted unit sounded the best while the floorstanding version lost some of the magic just to get another 1/2 octave of bass extension?

With separate powered subs you get to retain the magic while adding the foundation. You also have the option of placing the subwoofers where they mate best with the room. How many times do we move full range speakers around, finding that one spot gives the best midrange/imaging/soundstage but another provides the best bass? It's pretty typical. Separate subs fix that, and you don't have to be a bass freak to appreciate it.

Also, it's more cost-effective. You could get a pair of Cirrus Vapors with the external crossover option, stands, and a pair of JL F112 subs for at least $5K less than a pair of Wilson Sophias. You'd get all that midrange transparency and treble extension of the ribbons, plus inner detail owing to the Herculean bracing and cabinet damping of the Vapors, plus the slam and dynamics of the JL powered subwoofers. The total package is cheaper because you don't have to damp and brace the monitor cabinets to keep deep bass waves under control--they're in a separate box.

If you think you can just buy a subwoofer, drop it into your living room and add an octave to the range of your music, then you are deluding yourselves. Room volume and size plays a much greater role in the low frequency response of a stereo system than with the higher voice range frequencies. Just like discussed, speakers can have a perfectly flat frequency response in an ideal anechoic environment, they do not quite achieve that flat response line in a real world listening environment. Perfectly flat response is a bit dull and boring anyway. I know, I tried that once years ago. I worked hard on my room with an analyzer and anechoic panels to make a flat response at my listening position. It sucked the life out of the music. btw- I had speakers back then had a 20-20k Hz range. I found the bass sounded better way into the next room as compared to my listening position.
When you add a subwoofer to your system and things seem to go deeper, that's mostly because it is reinforcing the 30-40's Hz range. You are not going to hear 20Hz from 12 ft back, ie. not at the same SPL level as the higher frequencies. That wavelength is over 56 feet long. Sure you can fold it over and reflect it back, but you better have some sturdy walls to get efficient reflections and the distances better be just right so it is at the correct phase angle at your ears. Even the 30-40 Hz range have wavelengths over 20ft long so their SPL levels at 12 ft back are not going to be as high as levels in the voice range without some boosting. Just try listening to the grand pipe organ from 12 feet back sometime. You won't hear the low pedals that close to the pipes nearly like being much further back in the building.