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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
atmasphere's avatar
atmasphere
11,958 posts
 
A very illuminating study was conducted in which short-duration low frequency signals - including mere fractions of a cycle - were digitally created and played over headphones (to avoid room effects). Listeners were UNABLE to even DETECT the presence of bass energy from less than one full wavelength. Consider how long wavelengths are at low frequencies and you’ll see that, unless your room is very large, by the time you BEGIN to hear the deep lows, that energy has already reflected off of multiple room surfaces. In this context, a difference in subwoofer arrival times which amounts to a tiny fraction of a wavelength is inconsequential.
Herein also explains why high damping factors are overrated! The ear cannot detect instantaneous starts and stops if less than one waveform; it is the ability to stop a woofer that is trotted out in the discussions about damping, which goes something like 'Imagine a pulse which starts and stops...' and of course you can't hear that, and further doesn't exist in the real world.


Not meant to derail the topic!



noble100's avatar
noble100
2,419 posts
 

Hello Duke,

    I'm just glad you were following this thread and willing to give such a detailed and informative answer to my question. It all makes perfect sense to me.....Again..... and I'm sorry you needed to repeat your excellent explanation just for that dim-witted knucklehead. Thank you, again and the knucklehead did take notes this time.
    There's a lot of interesting and useful things to know about attaining very good bass reproduction in a domestic sized room and I'm very appreciative for your and James Romeyn's help in sharing the knowledge and experience both of you have gained over the years. It's definitely been of great value to me in my journey that has finally led to attaining near sota bass performance in my room and system.
    I've learned a lot and gained valuable first hand experience along the way. For example, I discovered that class D amp bass can initially sound very good on one's main speakers; very quick, impactful, dynamic and taut. However, I've learned the very high damping factors of many of these class D amps is a likely cause of the bass sounding somewhat unnatural, although still enjoyable, with the leading edge of the bass notes being emphasized and the trailing edges being underemphasized and the decay even being truncated. 
     I only realized this after I installed the AK Debra 4-sub DBA system powered by a Dayton class AB amp and continued to run my main speakers full range driven by my high powered class D mono-blocks (D-Sonic M3-600-M with 1,200 watts and damping factors > 1,000) originally into my 4 ohm Magnepan 2.7QR and now into my 4 ohm 3.7i main speakers.  Suddenly, the bass sounded much more natural, still with powerful and dynamic leading edge bass but also with easily discerned trailing edges and natural sounding decays.  
    I was wondering if you noticed the same thing with class D high damping factor amps versus class AB lower damping factor amps driving your speakers and subs?  If so, is this why you use a class AB amp instead of a class D amp on the Swarm and Debra systems?

Thanks for all your help Duke,
              Tim
tomic601's avatar
tomic601
13,037 posts
 
@audiokinesis Duke I emailed you a cool video of constructive and destructive interference and the nodal pattern , reflection matter :-) as I know you know
bdp24's avatar
bdp24
9,959 posts
 

In regard to Duke's mention of Jon Dahlquist's conclusion that the trailing edge of a bass tone is of more sonic consequence than is it's leading edge: Danny Richie of GR Research, in one of his Tech Talk Tuesday videos (viewable on You Tube), discusses the matter of "fast" bass. He explains why though woofers don't have to move very fast (in comparison with the other drivers), some woofers do indeed sound subjectively "faster" than others. It is his contention that it is the ability of a woofer to "stop" when the signal does (to "track" the signal) and return to "rest" that makes one woofer sound faster than another. All the GR Research subs employ the Rythmik Audio Servo-Feedback woofers and plate amps, known for their ability to produce "stop on a dime" bass.

Owners of planar loudspeakers, particularly big Magneplanars, know how different planar bass is from dynamic woofer bass. Tauter, leaner, a standup bass sounding more like a string instrument than it does when played by most box woofers, which make the string bass sound a little "plump." It may be that some consider the former type bass reproduction "over-damped"; I don't.

In one video, Danny shows spectral decay displays (waterfall plots) of various drivers and complete loudspeakers, THE most telling loudspeaker measurement in his opinion, the one most predictive of how a driver/loudspeaker will sound. Well worth the time searching for the video. 

audiorusty
287 posts
 
Playing with phase settings has little impact on the problem since there’s just a toggle for 0 and 180
This is not phase. This is polarity.
Some of the more upmarket subs have 360 degree control
This is phase. This basically helps to achieve maximum output level of the subs.
but the subs are obviously affected in the same way as the mains by the room modes and the frequency response anomalies.
 Multiple subs helps with this issue.
There's almost a smearing affect where the air and space around images diminishes and that's what I'm referring to as a 'phase anomaly'.
 This could be caused by an overlap in frequencies being produced by your mains and your subs. This is an issue that a crossover or speaker management system can eliminate. If you do not want to do an external crossover set the low pass filter on your subs to the low end cutoff point of your mains. Plugging any ports should also help.


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