Subwoofers and Phase Question For You Sub Experts


I use a pair of Dunlavy SC-3 speakers, known for their time/phase coherent crossover design.

When the stars align the speakers completely disappear and there’s a sense of space and 3 dimensionality that I’ve heard from few other speakers/systems. It’s easy to destroy the illusion with things like poor placement, poor setup of room treatments, etc.

Adding subs to the setup is both a blessing and a curse. The Dunlavy’s need some support in the nether regions and a pair of HSU subs do add a solid foundation to music which enhances the overall presentation; however, it’s at the expense of some stage depth, width and image dimensionality. Placing the subs a few inches forward of the front plane of the speakers helps a little but that isn’t where they perform at their best as ‘subwoofers’.
Finding optimal room positions for bass augmentation always creates a clash with the phase aspect of integration resulting in the diminished soundstage described above.
Playing with phase settings has little impact on the problem since there’s just a toggle for 0 and 180.

Which brings me to the questions - 
1/ How does running a swarm setup, with 4 subs, affect phase/time integration with the mains? Does it create twice or half the issue or remove it altogether?

2/ Looking at subs such as the JL Audio F series with auto room calibration, does the EQ algorithm compensate for any time/phase anomaly or is it simply looking for a more linear bass response?

I don’t mind investing in more sophisticated subs so long as I don’t end up with the same problem. I’m not really inclined to mess with software and the like, unless there’s no other way.

Thanks

Rooze


128x128rooze
Auto EQ is soooo variable.  

It is damn convenient and anyone can ise them, but I can understand why many dislike the results.  So, Dirac and JL have good results.

I love my miniDSP but what a PITA to set up right

gosta:"Tried the "swarm" approach and moved four subs into the room but unfortunately found out that they all have about the same tops and dips wherever placed (+/- 20 db from 25 to 100 Hz). So not much of an improvement. Room eq necessary."

Hello gosta,

     As Duke mentioned, something is likely wrong in your positioning of the subs or configuration if you didn’t notice a dramatic bass improvement using a 4-sub DBA in your room. I suggest you may want to answer Duke’s questions to you on his reply if you’d like to figure things out, he knows more about attaining good bass than anybody I’m aware of.
     In the meantime, I thought I’d share how I setup my 4 subs just in case it might work well for you. I have the Audio Kinesis Debra 4-sub DBA system using a single sub amp/control unit. However, I don’t know which 4 subs you’re using, a complete AK Swarm or Debra bass system kit or 4 traditional self-amplified subs. Either should work well, it’s just that you’ll need to adjust the volume, crossover frequency and phase controls on each sub individually if you use traditional self-amplified subs. On the Swarm and Debra, you just need to adjust these controls once on the included amp/control unit for all 4 subs as a group.
     But either way, following my positioning method could be helpful to you:

1. Disconnect your main speakers and move them to another room.
2. Hookup sub#1 and place it at your listening position. If you’re using self-amplified subs, do the same thing but set the volume to 50%, the crossover frequency to 40 and the phase control to "0" (in-phase).
3. Play some music with good and repetitive bass.
4. Starting at the front right corner of your room, slowly begin walking in a counter-clockwise direction around the perimeter of your room listening for the first exact spot that the bass sounds best to you (solid, detailed, dynamic and natural). Take your time, listen carefully and repeat this step until you are certain you’ve found the exact spot.
5. Once you’ve identified the exact spot, move sub#1 from your listening position to this exact spot.
6. Hookup sub#2 and place it at your listening position. If you’re using self-amplified subs, do the same thing but set the volume to 50%, the crossover frequency to 40 and the phase control to "0" (in-phase).
7. Play some music with good and repetitive bass.
8. Starting at sub#1, slowly begin walking in a counter-clockwise direction around the perimeter of your room listening for the next exact spot that the bass sounds best to you (solid, detailed, dynamic and natural). Take your time, listen carefully and repeat this step until you are certain you’ve found the exact spot.

9. Once you’ve identified the exact spot, move sub#2 from your listening position to this exact spot.
10. Repeat this procedure for subs #3 and #4, beginning from sub#2 for placing sub#3 and from sub#3 for placing sub#4.
11. Bring your main speakers back into the room, hook them up and position them optimally in relation to your listening position for midrange/treble and imaging. You now have 2 systems: an independent powerful,fast, smooth,detailed and dynamic bass system as a solid foundation and an independent everything else system consisting of any main speakers you choose to use.

     Once all 4 subs have been positioned, the final step is to optimally set the volume, crossover frequency and phase controls. It’s much easier to do this if you sit at your listening seat and have an assistant adjust the settings at your direction. I achieved the best results by precisely setting the volume and crossover frequency as low as possible with the bass still sounding powerful, fast, smooth, detailed, dynamic and natural. I set the phase at the position at which the bass subjectively sounded the best to me.

     As I mentioned earlier, these 3 settings are set once, for all 4 subs as a group, on the Swarm/Debra amp/control unit but must be individually for each sub if traditional self-amplified subs are utilized.


Hope this helps,
Tim
EQ wont affect phase. Beauty of JL is the continuous phase adjustment.Barry Ober the support guy at JL has some excellent material on their site explaining foolproof phase set up. (reverse polarity on speaker cables, play test tone at crossover frequency, dial phase until you hear the signal null, reconnect cables correct polarity) Check out his stuff.
My 2 cents.

 A pair of JL Fathom subs positioned near each SCIII and budget permitting a CR1 crossover.  Crossover the SCIII and the Fathoms at 80 Hz. bypass the crossover in the Fathom subs built in control.  Run the correction on each sub.  Then phase align them.

Play an 80 Hz tone. 

Disconnect the right speaker and subwoofer.

Reverse the polarity of the left speaker by connecting the positive speaker wire to the negative terminal and the negative speaker wire to the positive terminal.

With your head placed equidistant from the speaker and the subwoofer, slowly rotate the subwoofers phase control knob until you notice the bass drop off significantly, then begin to rise. With the speaker and subwoofer playing the test tone at the same level, but 180 degrees out of phase, a null point is created, and the bass cancellation should be easily discernible.

Set the subwoofers phase control at the position where the bass appears to have the least amplitude.

Reverse the polarity of the speaker again by connecting the positive speaker wire to the positive speaker terminal and the negative speaker wire to the negative speaker terminal.

Repeat for the right side.

>The CR1 has damping and and sub/sat balance controls for fine tuning.  Do a Google search and read the reviews.


OP, if you think this is a phase problem, in the sense that you would hear out of phase L and R speakers, swap both of your main speaker cables.  See if that fixes what you are hearing.
If that's not it, then I have no idea why we are talking about phase problems in your particular situation. If that's not what you are hearing, then the issue is the usual complicated subwoofer problem of integrating to the room and main speakers.