Distributed Bass Array configuration

    bdp24,
      The 4-sub Audio Kinesis Swarm and Debra DBA systems utilize a  Kilowatt class shelf-mount class AB amp/control unit with a 4th order variable lowpass filter that rolls off the bass at 3 dB per octave from 100 Hz down to 20.  
     The 4 sub modules have a gentle roll-off across their passband that is the approximate inverse of typical room gain from boundary reinforcement. Typical room gain from placement near a wall is 3 dB per octave below 100 Hz, and so the Swarm modules roll off at about

3 dB per octave from 100 Hz down to 20 Hz.  Here's a link to the system's description and specs: 

 http://www.audiokinesis.com/the-swarm-subwoofer-system-1.html

     When utilizing a 4-sub DBA in mono mode, I think it's important for everyone to understand that one is still able to perceive a deep and wide sound stage illusion in full stereo over the entire, standard and audible 20 Hz-20KHz frequency spectrum.   In other words, one is able to perceive stereo deep bass below 80 Hz and localize deep bass instruments in the stereo sound stage illusion.  

     I don't believe this bass perception, however, can accurately be classified as "stereo subwoofers" or "stereo deep bass" since the bass below about 80 Hz is technically being played back in mono.  In all the music source material I possess, the bass below about 80 Hz is also summed to mono during the recording process.

     My theory, about how this mono bass is perceived as stereo bass , is that bass sounds below 80 Hz have harmonics, or overtones, that reach beyond 80 Hz which are able to be localized.  These harmonics or overtones are recorded and played back in stereo through the l+r main stereo speakers. Our brains are then capable of associating these over 80 Hz harmonics/overtones, coming from the main l+r speakers in stereo, with the under 80 Hz fundamental tones, coming from the 4 subs in mono, and creating an overall perception of stereo bass that specifically details where in the 3 dimensional stereo sound stage the sound is coming from in a very natural and realistic manner.  

     My opinion is that this type of stereo deep bass perception is unique and deserves its own name or description, other than "stereo subwoofers" or "stereo deep bass".  I find a fairly low crossover frequency between 40-50 Hz performs best in my room and system for both music and HT.  Even though I know the bass is mono, I definitely perceive the music as high quality, very natural, very realistic and in full range stereo.

Tim

Tim yes correct. If I walk into a room with somebody bowing the low string on a cello, which is 41Hz, I can tell where it is. If the first 2 octaves can’t be localised then how is this possible?

It’s the harmonic overtones providing the spatial clues and the preservation of these overtones is vitally important to the entire spectrum.

It would not be possible to locate a signal generator producing the  same 41Hz .  as a sine wave.

noble101

There is no such thing as stereo bass below 80 Hz since it's a fact that humans cannot determine the originating location of any sound deeper than approximately 80 Hz.

That wasn't a fact back when you argued this under your old username (noble100). Remember? Tthat led to such vile, profane arguments from you that you were banned from the group. Now you're back with same same pronouncement.

If anyone thinks they're able to distinguish the specific originating location of bass below 80 Hz, I'd suggest testing this for themselves ...

Some of us have actually tested this, using both commercial and original recordings. You might want to try it for yourself sometime.

... Timing and arrival time of deep bass sound waves at an individuals ears are, therefore, also not anything to be overly concerned with since a 20 Hz bass tone sound wave is about 56 feet long, which likely exceeds the dimensions of at least the length or width of most domestic rooms ...

Non-sequitur.

The truth is ... we're still not able to determine specifically where these bass sound originated from if they're below about 80 Hz.

That's not quite true. Nor is that the standard for proving whether there is such a thing as stereo bass. Because phase matters, stereo bass can sound different than mono bass. It's not solely about localizing LF.

... Recording engineers have been routinely summing left and right bass under about 80 Hz as mono, and sometimes even higher, as a standard practice for over 4 decades.

It's not a universal practice and it originated as much for the convenience of the end user - to ensure trouble-free playback on cheap turntables - as it did to make things easier for the mastering engineer.

Because these recording engineers have known the truth about the myth of stereo deep bass for about the last 100 years, ever since scientists first discovered and formally established this fact through the scientific method. Don't believe me?

You do not know what you are talking about. First, we didn't have stereo 100 years ago. We didn't have the LP, either. Or tape. And I can prove to you through simple measurement that there is such a thing as "stereo bass." That is, I can show you that it is possible for bass recorded and played back in stereo to sound different from the same recording with bass summed to mono. 

@noble100 @noble101 you might want to get your head out of Secrets of Home Theater and your tattered copies of Stereo Review and stop fabricating imaginary scientific studies. You might also want to review the references about this that I gave you before you were banned from the forum, because you are just making yourself look silly here. After all, if those scientific studies you claim were conducted 100 years ago actually existed, the researchers surely would have posted them to the internet, right?

To be clear, mono bass can sound great, and it's often the best and easiest way to get good bass in some rooms. So as compromises go, accepting mono bass is a small one.

Hello lemonhaze,

     Thank you for using a very interesting example to confirm this likely principle.  I understand your comment about a signal generated 41 Hz fundamental tone not being locatable since it lacks the necessary overtones.

Thanks,
Tim

Seems that the term non- directional is getting mis-interpreted also. The low frequency sound waves from a subwoofer emanate in all directions and although seemingly an oxymoron is called non-directional because of that fact. As opposed to high frequencies that emanate from a tweeter in a single and focused direction.