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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
audiokinesis
2,753 posts
 

Jnorris2005 wrote:  "One thing to be aware of is that the sub will not add clarity to the main speakers unless the sub or the preamp provides a high pass filter to them, blocking out the bass that is now to be handled by the sub. Otherwise you're just adding murk to the low end."

That is certainly a very reasonable statement, but I don't think it's an absolute truth, logical as it may be.  In my experience it is possible to clean up the bottom end with subs even without a highpass filter in series with the main speakers, and depending on the specifics of the situation, that may even be preferable.  I can cite examples if you would like. 

"Also, if your room is small, chances are you don't need a subwoofer at all. The addition of one will muddy up the sound and probably activate room nodes that will devastate the imaging and sound balance of your speakers."

Agreed!  The smaller the room, the worse it is from a bass mode standpoint.  Chances are a single subwoofer in a small room will sound boomy, tubby, and bloomy, unless you turn its level down very far below the level of your main speakers. 

That being said, imo there is hope for good quality deep bass even in a small room.  This is somewhat counter-intuitive, but smaller the room, the more it benefits from the modal smoothing effect of using a whole bunch of intelligently-distributed bass sources.   

Duke

avanti1960
1,511 posts
 
@Jnorris    Absolutely not the case.  All speakers have a natural roll-off frequency beginning at their F3 frequency.  If it is a ported speaker the response drops steeply and makes a perfect acoustic crossover point.  You just have to find that frequency.  I use RTA software and full spectrum pink noise to measure the response at the listening position.  My current Harbeth C7ES3 have a very steep rolloff at ~ 55 Hz and that was the approximate starting point for my sub crossover.  
 Adding a high pass filter to the main speakers is something I would never do.  
noble100's avatar
noble100
2,419 posts
 
Hello again Duke,

     I'm very grateful for your many contributions on this thread sharing your very relevant knowledge and experience concerning how to attain very good bass response in our home music and ht rooms.
     You've mentioned 'real world' examples and it made me think that's exactly what I consider myself to be.  
     So, I thought I'd give some details about my speakers, room, how my 4 Debra subs are positioned in my room and the results just as a real world example for illustration purposes in case it might help.  
     My combo 2-ch music and ht system is in my 23 x16 x 8 ft. living room. I have a large hdtv centered on the front 16' wall with a Magnepan CC3 center ch spkr wall mounted just above the tv and a pair of Magnepan 2.7QR speakers straddling the tv, about 8'apart and 3-4' away from the front wall.  Here are the important specs on the 2.7QRs:

6' x 2' 3-way planar-magnetic panels
QR tweeter : 1½″×56″
midrange : 98in²
woofer : 620in² 
34Hz-26kHz ±3dB 
87dB/2.83v/m @500Hz 
Low-Pass 12dB/octave @ 650Hz

Band-Pass 6dB/octave @ 500Hz-950Hz

High-Pass 6dB/octave @ 950Hz

bass inverted

     2 of the AK Debra bass system's subs are positioned along the front 16' wall, one about 2' away from the left-front corner and the other about 2' away from the right-front corner with both behind my main spkrs and the 10" drivers facing the front wall and less than 2" away from it.

     The remaining 2 subs are placed along the 23' side walls, one on each wall about 2' away from each rear corner.

     All 4 subs are run in mono and powered by a single class AB 1K w Dayton with the cutoff frequency set at 40Hz.  I experimented with the phase control, slowly adjusting it from '0' to '180' and back again numerous times while listening for subtle improvements in the bass response. I failed to notice any changes so I set this control to '0' (in phase) and proceeded to the next setup step. 

     Once all 4 subs are setup, the instructions call for sequentially reversing the polarity on each sub to determine if the in-room bass response is perceived as improved with the polarity reversed on one specific sub of the 4.  If I recall correctly, my friend helping me and I were both tired at this point and we both couldn't imagine exactly how the bass could be improved, so we never completed this step on setup day or since.  It's been 3 years now and I still can't imagine how the bass in my system could be improved.  Since everyone who's ever listened to my system, including my friend and I, believes the bass is sota,  I'm thinking there's no good reason to mess with it now and possibly jinx it. 
     My current opinion is that the DBA system is the best method to achieve sota bass response in any room and it will be able to integrate seamlessly with any pair of main speakers.  I know I'll never need to buy another bass system again and I can use any pair of speakers I want with it in the future.  The DBA concept honestly does perform that well and it costs about the same as 2 high quality subs.  I also believe this system has a high WAF factor in my medium sized room.

Tim
erik_squires
16,414 posts
 
Umm ...

To OPTIMALLY separate the (low bass) subwoofer passband from the (mid-bass) main woofer passband, it's necessary to use a full 4th order (24dB/octave) active Linkwitz-Riley crossover.

The electro-acoustical sum is what matters, and it's more than just what you remove, it's how the subwoofer integrates with the rest of the system.

This is why THX used a sealed 80 Hz limited satellite as the standard.  Add 2nd order high pass filter, and voila, you have a total 24dB/octave roll off which would integrate nicely with a sub using a 4th order electrical low pass filter.

Honestly, only speaker makers and active room correction software does this anywhere near optimally, which is why I'm wary of recommending subs at all. It's not the tech is bad, it's the complications in the setup that I've so often heard as poor.

Best,
E
phusis's avatar
phusis
1,228 posts
 
I've chosen a 7th order (42dB/octave) Linkwitz-Riley low-/high-pass at 80Hz for my tapped horn subs and all-horn mains via a Xilica XP-3060 digital XO - it's simply what sounds the best. 

Previously I ran my mains full-range with a single SVS SB16-Ultra low-passed at 61Hz 24dB/octave (via its own build-in DSP), and while this pairing integrated very well my new setup with two tapped horns (powered by a Crown Macro-Tech 1200) and managed by the Xilica unit, now high-passing the mains, even at this rather early optimization stage sans PEQ offers better, indeed seamless integration with the mains, while lending the presentation a sense of uninhibited "breath," ease and coherency not heard with the previous single SVS-installation. 

Aspects of this no doubt falls back on the inclusion of not one but two tapped horns, but running the mains full-range, by-passing the Xilica, with a lower ~60Hz low-pass of the TH's tells me all I need to know with regard to my preference; to my surprise even running the Xilica over the mains with a high-pass isn't detrimental in regards to transparency, but has a freeing effect on the sound with noticeably better energy-coherence and overall integration. If there is something robbed of nuance via the Xilica, I'm not hearing it (in indication of how good a digital XO it really is), masked perhaps (perhaps not) by the other qualities it brings to the table with the high-passing of the mains that only adds to the enjoyment and insight of the sound. 

In not trying to make a case with the above as a generalization of what works the best in every situation (certainly, it depends), but simply to highlight that the typically non-audiophile approach of steep filtered, high-passing of the mains in the 80-100Hz region can work extremely well - with a pair (not four) of symmetrically placed tapped horns, no less, and in stereo mode, God forbid.  
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