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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
noble100's avatar
noble100
2,419 posts
 
millercarbon,

      I just recalled something about the Audio Kinesis Swarm and Debra that Duke knows more about than I do; there's something called 'bass room gain' that needs to be compensated for when setting up a distributed bass array system.  I believe it's a 3 dB increase in the volume of deep bass frequencies in typical rooms using subs that is the result of acoustic interactions in the room itself.  

     I know Duke somehow compensates for this so that the in-room bass response is flatter and more accurate but I'm not certain of exactly how he does this.  Hopefully, Duke is still following this thread and will respond.  If not, I suggest you pm him and ask.  

    Sorry I didn't recall this earlier but I think it's important for your custom DBA build.

Tim
millercarbon's avatar
millercarbon
12,531 posts
 
Yeah that’s fine Tim I got it covered. Its called room reinforcement. Every room has it to some extent. 3 dB per octave is rule of thumb. But it varies.

The free Parts Express cabs are all sealed. Frequency response of a sealed enclosure drops off very gradually, which actually turns out fine because the drop off is pretty much offset by room reinforcement. But you never can be sure your room reinforcement will kick in just right to match your speaker roll off. They may roll off early. So what Duke suggested, and I of course did, is build 2 sealed and 2 ported.

This way if it turns out I need the extra extension I’ve got it covered with the ported subs. But if it turns out that’s too much then I can simply plug one or two, in effect turning them into sealed cabs with the earlier/slower roll-off.

Some of this I have known since it feels like forever- from having built a transmission line speaker in 1980, and a ported sub about 10 years later. But a lot of the details used here, the use of room reinforcement, the sealed/ported options, and especially the distributed bass array concept itself, for all of that I owe a huge debt of gratitude to Duke. When it gets into "exactly how he does this" its proprietary info but everything else he has been graciously willing to share. As exemplified in his posts here. I only wish more were able to get their minds around this revolutionary development in subwoofer technology.
audiokinesis
2,730 posts
 

noble100 wrote:  " Duke somehow compensates for this so that the in-room bass response is flatter and more accurate but I'm not certain of exactly how he does this."

According to Martin Colloms and several others, "typical" room gain is about 3 dB per octave from 100 Hz on down.  Imo the implication is that  a subwoofer's response should gently roll off by 3 dB per octave across the same region.   This is too shallow to achieve with an unequalized sealed box even if the Qtc is very low.  However it can be approximated with a vented box with the right woofer parameters, box size, and tuning.  The Swarm units come very close to this target curve from 80 Hz to about 20 Hz, and since I don't normally recommend lowpass-filtering them any higher than 80 Hz, that seems to work fairly well.

There is another related effect going on with a distributed multi-sub system:  The subs are spread far enough apart that their outputs are combining in semi-random phase at the top of the bass region, but down at the bottom of the bass region the room size may be too small relative to the wavelengths for that to be the case, and their outputs end up combining approximately in-phase.   The transition from semi-random phase combining of the outputs to approximately in-phase combining of the outputs has the effect of once again boosting the bottom end relative to the top end of the bass region by maybe 2 or 3 dB.   If using only one amp, reversing the polarity on one of the subs usually restores balance to the force.  If using two amps with the phase controls set for phase quadrature, that phase setting addresses the issue. 

Other ways of dealing with either too much or too little "room gain" include plugging and un-plugging ports, engaging the "bass boost" switch on the back of the amp, and using the parametric EQ. 

The goal is to end up with smooth bass, and all of these things are just a means to that end. 

Duke

dave_b's avatar
dave_b
3,159 posts
 
Ya puts the speakers and the sub in da room and ya moves em around till day sounds da best!  Badabing....hopefully not badaboom :))
plga
184 posts
 
Hi guys,
I´ve been styuding about adding a pair of subs to my system.... you and Jim Smith got me convinced!

Although I wouldnt recomend bookshelf speakers with subs instead of a good pair of floorstanders, it seems that a pair of subs could improve quite a lot the sound of a full range stereo speakers. We'll see!!

I live in Argentina and it's much more expensive for me (about 50 to 100% more) to buy gear and impossible to try them home and have the chance to send it back to a dealer if I don't like it. So, I have to buy blindly, following the advice of others.

Wich subs would you recomend under this limitations:

1- My budget is about 1k top for each sub.
 
2- I would prefer not big subs (due to room and decor limitations). I only have two squares about 2.5' x 2.5' each, between the speakers and their respective side walls.

3- They have to be able to reach at least 25 Hz.

4- I've been advised to buy ones that can be connected to the output of the power amp, not to the preamp, to have better results.

I think the SVS SB-2000 could be a good choice, but it cannot be connected to the power amp, as I understand. How much does this issue affect the sound?  I have to mention that the distance between my amp and preamp to the possible locations of the subs is about 16/18' the longest and one of the cables for the subs (if a dedicated ones are needed) will have to share the same pipe as one speaker cable.

What about cheaper brands like Klipsch or Polk Audio?

I've had one Polk Audio PSW125 with a pair of bookshelf speakers and then with a pair of floorstanders and I didnt like the results AT ALL. Of course I didn't had it correctly voiced and it was only one sub, so I cannot blame it for the bad results. 

Thank you in advance!
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