There exists an acoustical phenomenon called "undertones". Two frequencies sounding together create a phantom tone well below the fundamental frequency of either of the original tones. Just as with "overtones" (harmonics), the presence of these undertones is a large part of what gives instruments timbral complexity, and what allows one to hear or sense the volume of the space that the instrument or voice is playing in. The sound instruments playing together or alone is a practically infinite matrix of the interactions of fundamental tones and harmonics (under and overtones). If a system cannot reproduce the lowest frequencies, the sound of instruments will definitely be impacted. How much and how important that particular aspect of sound is, is a personal call when we consider how many other things there are that affect correct record/playback. |
Ecruz, I wrote my post just after and before reading yours. Your account is a perfect example of what I described. |
****Clearly a sub often if not usually makes a big difference but the existence of lower frequencies in the harmonics is not required to explain it.**** - Mapman
Very true, but it is required when the sub is used in a purely "augment" mode as many (most) subs are used; as opposed to using the sub's internal xover, when the benefits you describe are technically as well a audibly obvious.
Another term for undertone is "difference tone". |
****so most likely not something that the speaker would play a role in producing assuming the speaker does in fact deliver the real instrument fundamental frequencies up to snuff.****
Some modern composers have exploited these difference tones in their music, and the tones are audible to the listener (audience). When I was in music conservatory we performed an experiment to find out if the remarkably loud difference tones produced by certain combinations of fundamentals heard in the performance of Eugene Bozza flute trios were captured by a recording, and they most certainly were. So I think while some of these effects may occur in the recesses of our hearing mechanisms only, undertones, in the usual sense, can most definitely be captured by the recording process, and hence need to be reproduced by speakers if the complete timbre of instruments is to be reproduced.
The cool thing about all this is that there is so much to this stuff that is still not fully understood. |
Not so sure either. If a recording captures, say, a 25hz tone that is a difference tone produced by two instruments' fundamentals (let's say 90hz and 125hz; just for argument, I am not up to the math right now) interacting acoustically, and the speaker playing back the recording has no output below, say, 30hz, then that 25hz tone is missing in the playback of the music. Now, does the presence in the recording of the two original fundamental tones mean that the acoustic interaction of these two tones in the listener's room produce the 25hz difference tone at the same level and with the same quality as what is heard live? I doubt it.
Moreover, why is it possible to hear the hall's sound in a live recording before a single note of music sounds from the recording; or in the rests in the music. Interesting tuff, no? |
****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. |
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****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. |
One of the things that bothered me most about early digital recordings (actually, until very recently) was not the harshness, brightness or grain, it was the very obvious (to me) sense that there was a frequency extension ceiling above the music; that the upper harmonic extension simply came to a screeching halt; technically speaking, around 21KHz. Some would argue that we can't hear above that range. Well we can argue that one forever, but wether it is the absence of harmonics above that range, or the effect that this absence has on lower audible frequencies doesn't matter, it is audible either way. I hear a similar effect at the bottom end of the spectrum. Wether it is the ambience cues that we hear/sense, or undertones, or whatever, when the speaker is incapable of reaching into the lowest octave there is an audible low frequency ceiling (floor?), where just as with the high frequency ceiling, things come to a halt and one hears/senses the absence of limitless extension even if there is no musical content in that frequency range. All this compared to the sound of live music, of course; not just in a hall, but also what one hears in a studio. |
