How critical is bass in stereo?

default -- Sat, 03/07/2009 - 22:42

I use to run 2 REL stadium's in stereo from speaker terminals as per REL's recommendations.
But now have 2 Fathom 12's running off Nad master series preamp which is a mono outlet. I'm using on board crossover in preamp at 60Hz. Movies are fine but music does worry me. I would have to split bass off from main preamp out which is not ideal. The Good sound doctor Miami says what I'm doing is fine.  I felt there was a sound improvement going to sub out and using on board crossover. My main speakers seem cleaner more dynamic and smoother by removing low bass. Fathoms are incredible so still a bit overwhelmed by there presence.

Steven Stone -- Tue, 03/10/2009 - 23:18

I'm a big fan of stereo subwoofers. I have a pair of Fathom F112 subs that I run with a stereo feed from my Lexicon MC-12B. I cross over at 60 HZ as well. The NAD doesn't give you an option of a stereo subwoofer feed? I'm surprised that it doesn't offer that option.
 
In theory at 60 Hz low bass is not directional, but the problem comes when the sub's bass extends up to 120 Hz (which if you are using a 2nd order crossover will still be audible) The JL's allow you to use a 24 dB per octave roll-off, which should get them out of the way by 120 Hz.
In my system I don't notice the JLs until there is some real low bass. The trick is to keep them as sonically invisible as possible.
 
I assume you're using JL's  microphone and built-in EQ system. You might also want to put on some full range music and listen with the subs on and off as well as with main's right and left power amp off to see where the bass does come in and what it's upper frequencies are.
 
Setting up and blending in subwoofers is as much an art as a science...

Steven Stone
Contributor to The Absolute Sound, EnjoytheMusic.com, Vintage Guitar Magazine, and other fine publications

Art (not verified) -- Thu, 03/12/2009 - 11:27

Depending on your speakers, of course, 60 Hz seems like a pretty high crossover frequency.  If your speakers are of good quality & truly full range, I recommend a lower frequency, maybe 40-45 Hz. More exactly: Use a test disc to find out where your main speakers roll off, and set the crossover so that the sub rolls in over that same frequency.  Tweak by ear if necessary, but you may find that this, along with proper volume matching, already provides excellent integration.
If you are using little 'satellites', then 60 Hz is probably reasonable.  But no sub I've heard is as musical at 60Hz as a decent full range speaker.  So expect some compromise.  That high crossover may also explain the need for dual subs.  At 40-45 Hz, sound is truly non-directional, and a single sub with adequate power will do the trick even in a large room.  The stereo image comes from the main speakers. (Tthe sub  provides a foundation and greatly expands the soundstage & sense of space.)
You want the main speakers doing as much of the work as they are capable of, and the sub doing only what they cannot.  That  will give you the best quality bass, and just the right amount .  Done correctly, you should never 'hear' the sub.  You should only miss it when it's not there.
Happy Listening!

Atul Kanagat -- Wed, 03/11/2009 - 08:28

My experience with subwoofers is that they are tough to dial in, but when integrated properly can transform the listening experience. The toughest thing to do is to find the best location for your room and the right filter & phase settings. Get any of these wrong and the result is often not very good (unless you have a room made in audio heaven). In many ways the setup is as important as the component and wiring scheme used.

Robert (not verified) -- Wed, 03/11/2009 - 16:47

Thanks for your comments. unfortunately Nad does not offer stereo out on sub although it has 2 outputs.
Absolutely love JL's I used ARO and JL microphone. I only hear it on low bass mainly movies but it is present in terms of the overall sound but seemless. I had my training on REL's and that did take some months to get right. I tend to be lean in terms of bass.
I've tried 24 db JL crossover although it was a cleaner sound my main Tannoy DMT12's are lean already in the mid bass so I prefer the Nad. I initially crossed over at 80hz but much prefer 60hz.
I always find it takes time and listening to a large selection of recordings to get sub settings right or as good as your room will allow.
 
 

Barry Diament -- Thu, 03/12/2009 - 11:01

 I believe the theory of non-directional bass is a misunderstanding that gets propagated via audio circles.
 
While low frequencies may radiate in all directions, this is not at all the same things as low frequencies coming from all directions.
Aside from its evolutionary uses, localization of low frequencies (i.e. stereo bass) is a reality.  This can be proven by taking a good, low distortion sub outdoors.  The low distortion part is important because we don't want higher harmonics (easier to locate) creeping into the picture.  Play a low frequency tone at a moderate to low level (to minimize incidence of harmonic distortion) and you'll find the sub is as easy to locate as a tweeter would be.
 
I am reminded of a great article Jon Dahlquist wrote for The Absolute Sound many years ago.  He very specifically differentiated between sound "in all directions" and sound "from all directions".
 
Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com
 
 

John Huff - Huff Loudspeaker Co (not verified) -- Thu, 03/12/2009 - 18:19

Bass is very directional.  That it is not is one of several persistent false myths in audio that refuse to die, or is dying slowly.
You can easily demonstrate it indoors, as I have done in my showroom at CES many times, to help put the myth to rest. I  wager with all disbelievers (who question my use of 2 subs by repeating what they understood from other "experts" ), that they can hear localization in the bass.
The experiment is as follows.  I have a complete high end system, with a pair of subs, also connected in stereo. 
First, I  disconnect 1 sub via a switch (or wire/plug). Within 2-3 seconds, literally every listener would identify which sub was still working, 100% of the time.
However, my external active) crossover also allowed me to flip 1 switch and convert (only the bass) to mono. With both subs working, identifying  the difference between mono & stereo bass is more difficult, but still, any good listener could do it. As Barry above mentions, for the test to be fair, the subs have to be very low in distortion, so listeners are not hearing higher freq harmonics.  (If there is harmonic distortion, the localization proof is invalid, due to the fact that the listener is hearing higher freqs.)  Our Sub Ones are sealed, compound loaded, Q of .53, with very high quality drivers, arguably the lowest distorting subs available, so they fill the bill nicely.
All high quality systems should have stereo subs, and HT systems should have a third LFE sub (assuming you want the best sound, and budget allows). This is all really common sense, to someone who thinks it thru & does the listening, rather than repeating myth.   I was a pro bass player in my youth, and I setup live literally thousands of times and listened to differences, so I have a lot of experience with bass.
Additional reasons for 2 subs: multiple locations of bass origination smooths out room modes (standing waves), electrical summing (within a crossover) is not at all the same as acoustic summing (in the room), cues re original room acoustics are contained in the bass, and much more.   Rather than go on, check my web site or email for more info.  www.huffloudspeaker.com
Thanks, and most importantly, enjoy the music!
John Huff
 

two (not verified) -- Sun, 03/15/2009 - 12:20

,,,,,,,,,Huff,,,.is that like my ohm speaker only a lot newer   any in michigan to listen too          I tune sub,s with a paino playing a few notes when the note  start s to get heavy I stop .It has to be a sub 4 music No movie subs  The way I tune movie sub,s is I get a crow bar and set the sub up with that  who cares

two (not verified) -- Sun, 03/15/2009 - 12:24

..ya,,3 subs are better then 2 smother responce5 better then 4

billy gold (not verified) -- Fri, 03/13/2009 - 02:55

Bass in stereo is for me critical.  I listen a lot to symphonic rock type music incorporating extensive use of synths and keyboards.  Much of the dramatic sequences in this music is built upon low-freq. bass as fundaments, so bokk-shelf type of speakers don't do it for me.  My final solution was to buy speakers with built-in active subwoofers with level control for the bass amplification.  In this way I am able to have one sub per speaker and the crossover is done by the manufacturer for best possible matching to the other elements within the speakers.  At the moment I am using a pair of Avantek Nine floorstanders from Swedish manufacturer Audio-Pro and I am very satisfied with this solution.
Thanks, and most importantly; enjoy the music!
Billy 

Loren (not verified) -- Sun, 03/15/2009 - 11:06

I learned about the importance of bass response long ago when helping a friend set up his Levinson HQD system.  Beyond the obvious musical content in the 20-80 Hz region, a great deal of room tone content is in this same frequency range.  When the bass is right and room tone properly revealed, properly done recordings can take on new life and a sense of reality, not just of the instruments, but their location in the room in which they are placed and the acoustics of the room itself.  This is as much about signal phase coherence between the sub & main speaker as it is level.
 
As to the directionality of bass, that would be dependent on the content of the bass.  A pure 40-Hz sine wave with no upper harmonic content is likely to be more difficult to resolve directionally than something like a kick-drum, which clearly has harmonic content and with it, a greater directional cue ... but who listens to sine waves?  In any case, phase considerations between the subs and the main speakers must be considered, and there will be a signal propogation difference in using the preamp outs vs. the speaker outs.  Some of that may be resolved with speaker placement, depending on the size of your room and the opportunity for change in speaker placement, but it may be a long distance from a slam-dunk.
 
My $0.02 worth.
 
Loren

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