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Will a subwoofer add depth and clarity to my system, or just bass?

hi folks,
I just purchased a set of Focal Aria 906 speakers with stand, powered by a Bluestream PowerNode (not my ideal system but I had a limited budget).  I think it sounds really good, but am wondering if an upgrade to a subwoofer is worth it, and if so, what would pair well with this system -- my audio guy recommended the JL Audio D110 10" Dominion Subwoofer, but that's out of my price range.  Perhaps a SVSPB1000, for $499?  My room isn't very big, and I don't use the system for movies, just listening to mostly jazz and rock (and classical).
Thank you!
jazz99
ieales's avatar
ieales
297 posts
 
One must remember that a filter alters both the phase and magnitude of the signal. This is represented by a phasor vector. See https://www.electronics-tutorials.ws/accircuits/phasors.html

Adjusting the phase control does not adjust level, only phase. When correct, there is minimum deviation in the vector sum, even though the level sum is relatively unchanged

See http://www.ielogical.com/Audio/SubTerrBlues.php/#Phasors for illustrations of how vector sum affects sub response.

If your sub does not have phase control, phase invert and variable slope, you have to be very lucky to achieve optimal integration.

In the immortal words of an LA musician, composer and all around genius:
¿¡¿¡¿¡¿¡¿ Those little speakers aren’t putting out all that gorgeous bass ?!?!?!?!?
<- No, there’s a Force subwoofer at the end of the sofa. ->
Every other subwoofer I’ve ever heard just boomed!!
millercarbon's avatar
millercarbon
324 posts
 
And I totally believe that you are quite capable of hearing when you had the correct phase setting. I just think you are most likely hearing the frequency response improvement that arises from your phase optimization
- audiokinesis

Hey Duke that is an interesting point you raised there. Reading between the lines you seem to be implying two distinct aspects- timing and frequency response. The way I've been thinking of phase is it sort of emulates location. Like, if the wavelength is 10 feet and you move the speaker 5 feet its the same as 180 degrees in phase. Yet I know that's really simplistic, its not just the one 10 ft wave that was shifted they all are. So is that why the setup (if I even understand that fully!) is first to get the four subs located one by one for flat response, and then fine tune with phase? To minimize messing up timing in the process of trying to get flat response? 
audiokinesis
1,872 posts
 

Millercarbon, my suggestion is this:  Once you have placed the subs, first adjust the gain, then the frequency, then the phase on the sub amp.   Expect to cycle through gain-frequency-phase several times.  

The word "timing" seems to me to imply "arrival time".  The ear/brain system is not very sensitive to arrival time in the bass region, but it is sensitive to decay time, because decay time translates to frequency response in the bass region.  Let me explain:

Because speakers + room = a minimum-phase system at low frequencies, the frequency response and the time-domain response track one another.  When you have a time-domain problem, you either have a peak or a dip.  The good news is, when you fix one, you simultaneously fix the other.   So bass traps reduce the decay time and thereby fix the frequency response along the way.  Likewise when a distributed multisub system fixes the frequency response, it also fixes the time domain response along the way.  Peaks take longer to decay into inaudibility than the rest of the signal, which is why they make the bass sound "slow". 

Back to "arrival time" for a minute.  I read an AES paper several years ago where they played signals of less than one wavelength at bass frequencies through headphones.  The listeners did not detect any sound.  They could not detect the presence of bass from less than one wavelength, and had to hear multiple wavelengths before they could detect pitch.  This implies that relatively small timing differences - "small" relative to the wavelengths in the bass region - are not going to make an audible difference in and of themselves. 

But in the bass region, the ear actually has a heightened sensitivity to differences in sound pressure level.  This is shown by the way equal-loudness curves bunch up south of 100 Hz.   A 6 dB difference at 40 Hz is subjectively comparable a 10 dB difference at 1 kHz.  This is why we can hear the bass so much better when we turn the volume up.  This is also why it takes so long to dial in the correct gain setting on a subwoofer amp - if we're off just a little bit, it's distracting.  Finally this implies that the subjective improvements from smoothing the response in the bass region are greater than we would think simply from eyeballing before-and-after curves.

So I think that where the phase control makes an audibly significant difference ends up being in the frequency response domain, especially in the region where the sub is blending with the mains.  I believe that the correct phase control setting is the one that results in the smoothest frequency response, but this is found in conjunction with the gain and frequency controls.  They all work together... gain makes the biggest difference so we adjust that first, then we adjust the lowpass filter frequency, and then the phase, and then we cycle back through fine-tuning at least once.

Imo, ime, ymmv, etc. 

Duke


noble100's avatar
noble100
1,093 posts
 
Duke,

Excellent explanation and it all makes perfect sense to me.
I was thinking, however, that I may understand better than some reading it since I’ve experienced the transformation of perceived bass response in my room by using a DBA (distributed bass array) system.
I think the practical consequences of designing a DBA system based on utilizing the principles you explained does not really become fully understood until an individual actually hears the transformation themselves.
I remember James Romeyn describing the bass response I should expect in my room from his Audio Kinesis DEBRA DBA system and thinking it all sounded too good to be true.

In fact, I recall being skeptical right up to the point I pressed play after setup was completed in my room. It didn’t take me long to know James was telling me the truth. My honest opinion is that the transformation of the bass response in my room to state of the art was nothing short of miraculous, especially considering it was affordable ($3K) and done without any mics, room correction, room treatments or other special equipment.
I know you’re too much of a gentleman to use a thread post as a sales promo for your own products so I’m taking the opportunity to do it for you and Jim as a very satisfied customer. Besides, no one ever accused me of being a gentleman.
I can state with certainty that the DBA system works extremely well whether it’s an Audio Kinesis Swarm or Debra complete system or a 4 sub custom configuration with subs of your choice.
My main point being that I could write a book on how well it performs and convince no one but it only requires a short audition to prove to anyone. To mangle an old expression, a listen is worth a thousand words.

Tim

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