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One last point: If you've got the dough and real estate to spare, don't shrug off the sub-20Hz content I've shown in the reference waterfall plots as unintended artifactssay, scraps of subway rumble or HVAC noisethat somehow slipped through the filters during the mixing process. The content is program-related and meant to be there. So, okay, as a hardware matter, how did the engineers at Todd-AO who snagged an Academy Award for Best Sound for Black Hawk Down monitor all that gut-twisting infrasonic contentall those rumblings I've mentioned that lie just beyond the reach of even refrigerator-sized subs? They used big Bag End subwoofers22 of 'em.
Suffice to say the difference the TRW made was quite significant. After seeing/hearing with the TRW, the Vogon's destruction of Earth scene in HHGTTG was empty and hollow with just the three subs, almost devoid of the rumbling that the TRW provided. The cannon shots in Master Commander were OK before the TRW, hitting you in the but. With the TRW, the cannon shots were shockingly violent. You were absolutely there in the cannon bay of the British man'o'war, getting a concussion from the black powder cannon blast. WOW! After these clips, I simply HAD to HAVE this TRW IN MY THEATRE!
Perhaps the biggest misconception is that very low frequency sound is all "feel". If you get 6-10Hz up to over 120dB then yes, you begin to feel it. But you can actually hear it long before you feel it. In fact with mixed tones as is the case with a pipe organ the audible thresholds for very low frequencies are much lower, about 6 to 10dB less than the pure tone thresholds. In other words, well before you feel the sound you will hear it. In the middle of the sanctuary the 32' and 64' sine wave stops sounded really good. 105dB is the sound level it took to make these tones below 20Hz audible. This became the reference level for these stops.
A most important feature of the magnitude graph (relative to our earlier periodic-function spectra) is that our transient signal has frequency content at every frequency, not just at discrete frequencies. Our example also shows that the frequency content gets smaller as we go higher in frequency. This trend will be observed in all spectra of transients; thus we can use such spectra for estimating the highest frequency for which a system model must be accurate, just as we did with Fourier series for periodic inputs. Note also that much of the frequency content is located below the frequency 1/T, so 1/T is useful in roughly gauging where the spectrum begins to drop off. Thus if T=1.0 second, we have strong content to 1Hz. This feature is applicable to general transients, not just our simple example.
In the real world sounds go literally all the way down in frequency, an audio system should do the same. An audible form of distortion exists if content below 20Hz is not reproduced.
Originally Posted by gchuva /forum/post/16850196
How important is to have a sub with substantial output below 20 hz? If a sub has a sharp roll-off at 20hz, will that be less important if your are listening at lower volumes?
Originally Posted by bossobass /forum/post/16851040
Anonymous commenter at a demo of the Thigpen Rotary Woofer:
From a research scientist:
Observation from an acoustician:
My own observations:
The number of soundtracks with sub 20Hz content is large enough, and there's no reason to suspect that the trend will reverse, especially with the advent of lossless soundtrack encoding.
There isn't a requirement for substantial sub 20Hz playback ability. Nearly all sub 20Hz content is encoded at -10dBFS or lower, requiring playback at reference level to hit peaks of 105dB.
The fact that most every room will offer room gain boost of sub 20Hz playback makes reproduction easier and cleaner.
When people have asked me why I concern myself with sub 20Hz reproduction I usually have answered the question with a question, "Why not?" It's simple enough to do. In fact, it's a consequence of building a subwoofer and placing it in a room, not a mythical quest for unobtainium.
My own opinion of sub 20Hz content when listening at lower than reference levels is that there is zero evidence to suggest what is heard, felt or not, relative to the rest of the bandwidth. The Equal Loudness curves many refer to are 1/2 century old extrapolations from higher frequency single sine wave tones.
Thigpen's observations regarding his work in augmenting a pipe organ in the sub 20Hz BW suggest that the ELC need to be revisited with modern technology and better test methodology.
Finally, the bottom line is that opinions are irrelevant to the fact that the specification for all discrete multi-channel surround formats dictates a BW to 3Hz for all channels. This has been the case for over 15 years, and it isn't going away any time soon.
My philosophy is 'to each his own'. There is no law against setting your own standards of an arbitrary bottom frequency, for whatever reason. But, there is no question as to the BW of the format and the number of examples with sub 20Hz content within the format. The question as to how it's perceived at sub reference level playback has yet to be addressed at all, let alone having been answered.
Originally Posted by Scott Simonian /forum/post/16857583
This picture you captured is also a great visual to show to people were all that 'slam' comes from on a bass drum, for example. Not just in the "midbass" area.Goes all the way up to the mid thousands. Great reference.
Originally Posted by Ricci /forum/post/16856852
To add to what Bosso has said. This is the spectral content of a bass drum strike (mine) as picked up by a microphone that is only about 3db down at 20hz but is almost 12db down at 10hz. Hence the level of really low bass below 20hz is represented lower than it should be.