My experience adding subwoofers to 2 channel

mijostyn:
" I can not believe people are so far off on the subject of time and phase. Time and phase are intimately related. wire two of your subs backwards and see what you get. That is 180 degrees out of phase."

Hello mijostyn,
     It seems we still have a misunderstanding about time and phase on deep bass sound waves. I believe, at the core of this misunderstanding, is that you're referring to arrival times of deep bass tone frequency soundwaves at the listening position and assuming that the effects of these deep bass soundwave arrival timing are just as critical as they are with midrange and treble tone frequency soundwaves.  
      The owner and speaker designer at Audio Kinesis, Duke Lejeune, has stated that the arrival timing of deep bass tone frequency soundwaves at the listening position are much less critical than the arrival timing at the listening position of midrange and treble frequency soundwaves.  He stated the reason is the extreme differences in the physical length of these sound waves: a 20 Hz bass soundwave is about 56 ft long, a 2,000 Hz midrange sound wave is about 6.75 inches long and a 20,000 Hz soundwave is a fraction of an inch long.  
     I wanted to include a prior post in which I responded to another question from you concerning the time-domain of bass soundwaves that contains similar and some additional relevant info: 

 mijostyn: "You have two subs back there with you and you hear those fractionally before you hear the ones on the front wall. This will smear transients. You want to hear all your subs at exactly the same time."  
    It's my understanding that the time-domain on frequencies under 100 Hz are not as critical as some believe. I also read an article on an experiment proving we don't even detect deep bass sounds until the entire frequency soundwave cycle exists in the room. The experiment consisted of subjects wearing headphones. A series of computer generated partial and full cycle deep bass tone soundwaves were played and the subjects only were able to detect the bass tones in which the full cycle was played and no sound at all when the partial cycles were played. As you know, it takes some time and distance for a full 56 foot long 20 Hz soundwave to develop in a 23 x16 foot room.

     I realize the importance of correct phase in audio reproduction but admit only having a basic understanding.  All 4 of my Audio Kinesis Debra DBA subs are operating in mono and in-phase configurations.  Once all 4 of my subs were optimally positioned, however, I followed the procedures by reversing phase on each sub sequentially, one at a time, to verify whether or not the overall bass response improved with one specific sub's phase reversed. I noticed no improvement with any single sub's phase reversed and, therefore, maintained operating them all configured as in-phase.
     The above is what I learned from scientific research results conducted by acoustical experts Dr. Earl Geddes and Dr. Floyd Toole and Duke Lejeune's posts and writings.  I believe everything I've stated is accurate but you could always refer to their writings if you'd like to verify or learn more.


Tim

millercarbon the radiologists when doing a barium GI study call it FOS.
Blaming me for not knowing what you are talking about will not change the reality of the issue. All of you reverse the wiring of one of your sub woofers and tell us what you hear. millercarbon you are way out of your league. In my estimation filling other people full of your mythology is not an ethical way of dealing with your compatriots. 
Tim, never trust anyone who is trying to sell you something. Arrival times (phase) are even more critical in the bass. I wish I could demonstrate that to you directly but that is not possible. Again, wire your subs out of phase and tell us what happens. Regardless of what anyone says, a phase (time) coherent system is more accurate and realistic than one that is not, particularly in the bass. I have nothing to lose because I am not trying to sell you a darn thing. Beware of Greeks bearing gifts. Go to a local club and have a listen. If your Hi Fi does not approach that sound quality playing similar and well recorded music you have problems you might want to conquer if you even care. Music is not something you just  hear. You also feel it which is critical to the experience. millercarbon obviously does not understand this and is destined to wallow in mediocrity unless he changes his approach to life. It is not easy to achieve this with analog equipment but it can be done and there in lay the challenge. millercarbon would rather make excuses than except that challenge. Will you do the same?  I hope not. It is a wonderful thing to be able to get home at night, go to the concert and feel as if you are really there. If not it is something to strive for which I did for 45 years.

Hello m-db,

     Thanks for the additional info.  I do understand your point about subwoofer DSP room correction differing among manufacturers as well as differing by version from the same manufacturers.
     I only have limited sub DSP room correction knowledge and experience, mainly gained from helping install and configure subs in the systems of friends and family.  My 4-sub Audio Kinesis Debra DBA system has provided exceptional bass results in my room without utilizing any DSP room correction or room treatments and I believe this can be accomplished in any room and with any pair of main speakers. 
     Khiak has 4 exceptionally good subs, two JL Audio F112s and two Funk Audio 21.0LXs, that utilize relatively basic DSP room correction (with the Funk Audio subs only using DSP to adjust signal delay times and not the more specific adjustments possible via parametric equalization) and my current thinking is that these subs could be used to form a very high quality custom 4-sub DBA system either with or without  running their DSP room correction.  
      The main adjustments for good integration would be the manual settings on each sub for volume, xover frequency and phase.  I used these exact same controls, although on my sub amp for all 4 subs running in mono mode simultaneously, to achieve excellent bass response and seamless integration.  I'm unaware of any reason khiak couldn't get the same or even better results in his system and room. 
     Once all 4 subs are positioned and configured, he could always run room control, for a pair of subs at a time, to see if it improved the overall bass performance and just use the configuration he liked best.
     But I think khiak was a bit shocked by my suggestion he should remove all the numerous and expensive bass traps he currently has installed around his room.  I understand since they were likely a big investment but they actually are unnecessary and it would free up a lot of room space.

Tim
       

     
 

My experiences tuning subwoofers with main speakers is that the phase timing is critically important at crossover blend region where the subwoofers and main speakers transition between each other.
An 80Hz wavelength is ~ 14 feet long and is small enough that room dimensions, distance between subwoofer and main speakers as well as distance to listening position can affect the quality of bass response.
Even with a 40Hz crossover frequency there is still significant energy at critical mid bass frequencies (e.g. 80-120Hz) being broadcast by the subwoofers and main speakers. If the timing of the subwoofers is not adjusted accordingly so that the mid bass frequencies aren’t optimized then the listener will hear weak midbass from phase / timing cancellations.  The deep bass will be OK but there will be a gap in the response such that the impactful midbass frequencies are relatively weak.  
The only way I have found to get this right is to use tracks with powerful bass beats and adjust the phase of each subwoofer until it sounds the best- (by ear). With experience you’ll know it when you hear it.  The impact frequencies in the midbass will sound effortless even at low volume levels.  The key is in the midbass.     
DSP, room correction etc. fall short of achieving this automatically.

mijostyn:
"Oh, and Tim. I am not saying that in certain situations a DBA system may not be the easiest way to reasonable bass performance. It may work reasonable well for many people. What I am saying is that in the end it will not produce the most accurate and realistic results but do to do so usually requires advanced digital speaker control that at this time costs at least $6K. If however you have a tape measure, some savvy and some luck, you might be able to get there without the computer. An important part of this hobby is being able to screw around with your system to see if you can get it to sound better and in doing so you learn. So, start screwing around!"


Hello mijostyn,

     Incorrect, wrong and you're mistaken.  Millercarbon absolutely knows you're wrong because he had the intelligence and cajones to give it a try.  There's no need for expensive advanced digital speaker control gear, any other DSP or PEQ equipment, tape measures, meters, bass room treatments, voodoo, chants, snake oil, savvy or even luck. 
    The key ingredients are just a minimum of 4 subs , proper positioning of all 4 subs and some precise and time consuming listening, calibration  and repeating of the volume, xover frequency and phase settings until it sounds just right.
     I believe the root cause of our disagreement over the effectiveness of 4-sub distributed bass array systems is your lack of experience and familiarity with them.

Tim