My experience adding subwoofers to 2 channel

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 

Avanti I agree with you almost entirely. You do have to with your rooms acoustics physically but particularly when it comes to bass there are limits as to what you can achieve. You can not achieve SOTA bass without digital bass management and subwoofer control. First you have much more control over x-over frequencies and slopes. In the digital realm there is no phase shift. Then you can adjust the frequency response of the sub woofers so that they are up 3 db at 20 Hz. Tolerably sized sub woofers start rolling off at around 60 Hz and are down 6 to 9 db at 20 Hz especially if they are not closely coupled to a wall or corner.
With enough power this can be corrected with startling results. Putting on a 20 Hz tone is a riot. It sounds and feels as if it is coming from the whole house and everything buzzes and rattles. Dishes, silver ware, picture frames, the toilet and my teeth. At 60 Hz I can definitively localize the sound and the symphony of rattles stops around 40 Hz. 
Tim, the best speaker control (room control) measure each speaker independently and adjusts each speaker independently. The problem with sub woofer systems is that they ignore the satellites.     

Oh and Tim I have used subs in every configuration you care to think about and have been using 4 subwoofers for......25 years anyway.
I am glad you like your system and that it works for you. Unless you are extremely lucky your bass below 40 Hz is for certain a mess. Lord knows what it is doing up to the x-over. If you send me pictures of your room and system I would be happy to fix it for you. I am working with another forum member who has Acoustats and was unhappy with his DBA system. Of course he is use to a level of detail and imaging that you can't get out of dynamic drivers so the muddiness of a DBA system would be more offensive to him. I have not heard back from him yet but I think we have finished adjusting his system.
I don't have to use a tape measure myself. All I do is set up a microphone and tap the measure button which is displayed on my PC. If I am happy with it I tap the enable button and all the volume, delay and frequency adjustment are made in a few seconds. Then I overlay my own response curves and we are good to go. No guessing and I am not relying on anybodies hearing not even my own. There is no way I could get bass this good by playing around and depending on hearing. You can't either especially with sub woofers thrown all over the room.