We need deeper bass response than the lowest pitch frequencies

[Brian Beck]

I'm new to this particular thread, but wanted to add my two cents worth (two hertz worth).

There is a mistaken impression that one only needs very deep bass response (say below 30 HZ or 20Hz) for that rare pipe organ recording or for movie soundtrack noises. Some people feel that the lowest frequency of interest ought to be the lowest note on a bass instrument, E1 (41.20Hz) and that 40 Hz response is therefore low enough for all but E. Power Biggs fans. Oh yes, the argument continues that 88-key pianos do go down to 27.5 Hz, but that the energy of that fundamental is very low due to inefficient sound board coupling (quite true). Well, 40 Hz may be low enough for some people, but this thinking, when professed as a fundamental truth for all others, reflects a misunderstanding of the physics involved, IMO.

Only steady state sine waves occupy a single frequency (in theory only those waveforms that started at –infinity and will continue through +infinity can be said to occupy a single discrete frequency). The transform of a 40 Hz tone that starts and stops abruptly (say, a plucked string) produces a frequency spectrum with variations on a sinx/x shape, which is to say that energy may be centered at 40 Hz, but that there is energy smeared well above and well below 40 Hz. (This should not be confused with sub-harmonics; that’s another matter.) We need to hear/feel that energy to recreate the full plucked or gated effect as if it were live. Energy from any transiently-gated bass waveform will show considerable energy down into the so-called infrasonic range. Drums combine periodic waveforms and some noise-like waveforms, but being transient in any case, also produce energy down very low, especially with bass drums, of course.

If you high-pass filter that original signal with a speaker that roll-offs below 40 Hz (and most do), especially with a steep roll-off like you’d have with a vented enclosure, then a part of the original spectrum is cut off, resulting in a changes to the transient envelop and time smearing. We're so used to it, we hardly notice most of the time.

The ear/brain/body can sense low frequencies even below levels where steady state sine waves cease to be audible. Call it a “feeling”. There exist plenty of decent recordings with some of this low frequency information left more or less intact. When played back on a truly wide range system, which is one that goes well below 20 Hz, there is a sense of openness, space and “being there”, more than the sensation of lots of bass tones. Too many people have really never heard a truly full-range system with good recordings.

Bag End makes subwoofers that are equalized down to 8Hz. Silly? Not at all; they understand musical physics. Their description follows: “The reason that the INFRA type subwoofers sound dramatically better than the others is because of their superior time domain performance. The INFRA subwoofer maintains the bass energy in a tight packet, aligned with the upper range signal, providing a seamless musical connection with the main loudspeakers. This is achieved by making the system have a very wide, very flat frequency domain response.” (I am not affiliated with bag End, nor do I endorse their products).

I am stepping off my soap box….right now! Comments?

[Pan]

Right on!

I do believe this goes for the other direction as well. Even if most of us only hear up to 18k listening to sine waves I think we need DSD or 24/192 to even approach truly realistic sound. The sharp roll of down low and the brickwall shape at the upper limit of 16/44.1 PCM is a phenomena that never happen in nature.

5Hz-50kHz BW is a realistic goal for a high performance rig IMO.

One must also not forget that not only our speakers are BW limited, but also some electronics, the microphones and lots of intermediate stages and all of this accumulate which is very detrimental to natural sound. -1dB here and -3dB there soon creep down well into the audible range, resulting not only in decreased amplitude but also as a phase distortion, a distortion in time domain as you mention.

/Peter

[AndrewT]

Hi,
IMO you are in the wrong forum. Audio ranges from 20Hz to 20kHz although at my age it stops at 14kHz. This is DIYaudio.
Find a forum called DIYfeeling(infra) to DIYultra and ask them.
Sorry you asked for comment, I'm not feeling too helpfull tonight.
I agree but for a different reason. To get a flat response over the full range you need to ensure the reproducing system is frequency and phase accurate and this necessarily requires the system to reproduce well outside nature's audio range.
I believe that most listeners will agree that our limited range systems are a compromise that try to meet value, space and partner/neighbour demands.

[Pan]

I´m sure you´ll feel better after a good nights sleep!



/Peter

[Brian Beck]

Peter,

Good point about needing top-end extension for similar reasons! Now, this is not a subwoofer topic, but my first posting sure was.

[aosone]

In addition to what you've said, it would be good to point out that extended low frequency response has to be accompanied by a good power bandwidth in order for it to be useful. You have to move a lot of air. That's the part of low frequency cabinet and driver design that's hardest to accomplish.

And you're right. Too many people haven't heard this kind of low end.

[simon5]

I agree with you, we will probably be able someday to go to 1 Hz - 100 kHz. With Diamond drivers and the like we are near the 100 kHz, but the low end is causing more problems.

[454Casull]

Why would anybody even want to listen to/feel 1Hz?

[simon5]

Earthquakes

A well built cinema made to handle the new Movie, San Francisco, with 1 Hz 130 dB blasts!

Well, we need at least 5 Hz I guess... to reproduce most of the spectral content of the 8.2 Hz organ pipe.

1 Hz - 100 kHz sounds good too, "my system handles 5 decades" or maybe 1 Hz - 131 kHz, "my system handles 17 octaves"...

[efren sabio]

I have to agree with IMO.

Recently I listened to a concert in a park and it was a percussion
group from china. There were huge drums, the biggest I've
seen so far. The PA sound system was adequate with big
speakers like in rock concerts. I compared the sounds emitting
from the huge speakers and from the sounds coming from
the huge drums by going back in forth to the 2 sound sources.

The sound coming from the big speakers paled in comparison
from the sound coming from the huge drums! With these drums
it's so much better to listened with both the ears and our bodies!

It was obvious too that the SUB-frequencies from different
directions were mixing and the resultant AUDIO frequencies
were being produced.

We live on planet earth and we do hear the sub and ultra
ranges but we audiophile unconsciously know it's very
expensive to extend our current systems!

Peace

sonda