Recently I had a number of conversations on “what do you use for sub-bass”.

I have a few answers here’s the popular ones:

• I don’t think you understand sub-bass and audio.
• I don’t.
• I duplicate my bass track and offset one by a few microseconds.

Huh?

Let’s build this up.  I will start at the wikipedia entry on subbass (as of 13Apr2011). Specifically this quote:

Sub-bass is a term used to describe audible sounds below 90 Hz and extending downward to include the lowest frequency humans can hear, typically 20 Hz. Sound systems often feature one or more subwoofer loudspeakers that are dedicated solely to amplifying sounds in the sub-bass range. Sound below sub-bass is called infrasound.

If you want to stick with this fundamentally broken definition, go with it, stop reading, and don’t talk to me about sub-bass.

Now for the truth and logic.

The “sub” element generally refers to “below”. So your sub-floor is under your floor, a subway is under the “way” aka road. If something is sub-standard it is below the standard.

So that definition (and the hard core etymological roots) dictate that sub-bass is a “below bass frequency(ies)”.

So what is bass?

Humans generally can hear down to 30hz, 20 hz is pushing it, 10 is the bottom and isolated. Yes, you can feel those frequencies, but not necessarily hear. If you hear something at 20 hz you are hearing formant, extra noise, or elements that bump energy into normal hearing range.

You can hear 20hz when you have an LFO at 20hz applied to another (audible tone).That idea is dubious in nature, but important to mention.

The standard bass reference is the instrument that holds the name “Bass” guitar.  Using a standard tuning the low E bottom note (the actual low E) is ~41 hz. A standard tuned 5 string bass guitar sees the low B at ~31hz. (info via wikipedia).

According to The Mixing Engineer’s Handbook, Second Edition (ISBN # 1-5986-3251-5) Bass Guitar has a bottom of 50hz, a kick (bass)  drum bottoms at 80hz, organ and piano have “fullness” at 80hz,  the voice has fullness at “120hz”.

If you search on the internet for a bit you will come up with a kick/bass drum frequency range of 50-120hz.

More debunking!

I have a significant amount of experience in car audio as well as other audio formats.  My last system (I stopped only due to theft) has these stats:

• 1000 watts class A FET amp
• 2 x series 1 (basic speakers rated at 80 watts each) 8″ speakers
• 7th order enclosure (nominal 4 cubic feet)
• 34hz free air resonance
• faithfully reproduces 20-150hz
• measured at 140-150 db no distortion
• blew out 2 front windshields from bass
• could make myself or any passenger ill, really ill, in 30 seconds using bass reference test signals
• unable to insulate the CD player from vibration to actually push speaker harder
• quarter bounce test on the trunk.  12″ no problem!

So that is one of many “street cred” on bass.  Why do I mention this? Because in engineering a system and reproducing sound the speakers are applied in ranges. In the most simple scenario, as well as the most common, you will have bass, mids, highs.  There are middle categories, but that is just splitting hairs.

In developing a system (car, home, and venue) in three ranges you will use crossovers. A crossover removes certain frequency ranges in an audio signal. This is applied to sound as a large power system will not have many speakers (usually none) that can cover the full frequency range (20-20k hz).  So the bass speakers get only lows, the tweeters get only highs, and you scoop the mids for the midrange speakers.

Makes sense.

So, let’s look at how professional audio applications mechanically define bass.

The following information is from 3 random selections (first Google results offering technical specifications) for car audio crossovers.

1.) PYLE Wave PLXR2 Crossover specifications state “Low Pass Frequencies :  90 Hz, 50 Hz, 180 Hz” where these numbers represent the point where the crossover takes effect.

So at a 90hz setting the slope of the crossover will be applied thus diminishing the signal strength above 90hz and effectively only allowing 90hz and below to pass through (thus a bass pass).

1b.) This same Pyle unit also has a “Bass Boost” – where the specifications state  “Bass Boost Frequency : 45 Hz, 80 Hz, 120 Hz”. (at those frequencies you can add 0-12db).

2.) Parts Express Subwoofer Crossover is a 4 OHM (load) passive crossover that applies a 12db/octave slope to frequencies above 130 Hz. In other works, this simple passive crossover circuit states bass is 130hz and lower.

3.) Lanzar OPTI Drive OPTID100 Crossover is an active crossover with adjustable cross over points. So we need to use the boost as a definition of bass. That range is 40 – 400 Hz

I can pull out stats like this left and right.  Bass, by any reasonable definition, is audible. Sub-bass is not.  Thus my favorite answer from above:

I duplicate my bass track and offset one by a few microseconds

Meaning, I employ REAL SUB-BASS by stacking and offsetting 2 bass frequencies to create subtle phasing. This generates REAL SUB-BASS frequencies similar to the LFO-ish tone of a 1/2 step (flat 9). These frequencies are very low.

Another REAL SUB-BASS method is to apply an LFO to your bass. The common practice calls for a chorus effect.  Octave dividers also perform in a similar fashion (oh, some fun math in dividers!)

Conclusion

Sub-Bass is nothing more than a misnomer used by people who either “don’t understand sound” or who are looking to be special.  There are isolated references for sub-bass here and there, but in the larger professional scope (and I could go on forever) bass is generally considered to be 30-150hz.

The bass heavy music that saturates the scene is typically 50-80hz. That is called bass, not sub-bass, just bass.

Thanks for listening. Feedback welcome.

–Marc

[[[edit / update]]]

Peter with Livid pointed out Sound Traducers ability to generate true high energy real sub-bass. Yes! They are out there, I have played with them, they will void any and all warranty on everything, including the building.

These “speakers” have a few names, but they all function on the same level.  In short, they are the copper coil+magnet for electricity (get ‘cah electromagnetic action ON!) as in a speaker. But instead of moving a speaker or cone, you strap these buggers on the floor, wall, couch, whatever. The result is your couch (example) IS the speaker.  This is, in a simplified sense, how piano (sounding boards) make strings louder.

In the case of the piano the strings vibrate, they are strung across a bridge (general term) that has a high solid surface area contact to the sounding board wood. That wood in turn amplifies the sound. Same general methodology used for a violin, guitar, etc.

And your door. That is why your little knuckle is enough for the dogs to hear when they are our peeing on your garden.

So using sound transducers, your floor (or whatever) becomes the speaker.

Alternatively, you can use ST’s filtered (optional) and 180 degrees out of phase (required) to cancel out waves. And with some math, good sampling equiptment, and tight audio engineering you can manipulate bleed, room volume, and isolate freequencies for removal.  Total audio crack. But I digress.

Thx Peter!