I have used my subwoofers in "stereo" for years. Read the following and see if you think you might get some benefit from this setup. To do it, all you need is two powered subwoofers with internal line level crossovers, and two extra interconnects.

While it is true that low bass is in theory non directional, the way that bass mixes in the room is not. An example - suppose that you have a group of performers on a stage and they are being recorded by two or three omni directional microphones in front about 15 feet away, which is a common technique. Now say you have someone playing a bass drum or string bass on the extreme left of the stage. The sound of that instrument will reach the left microphone earlier than the right microphone. Considering the frequency of the instruments will be be around 30 Hz in the case of the bass drum and 40 Hz in the case of the bass, the delay in the sound reaching the left and right microphones will be as much as half a wavelength. If you were to play this with a single subwoofer, or two subs with the bass between the channels summed by the crossover as it is when you use the "sub/LFE" output on your pre/pro, this acoustic delay would simply cause peaks and dips in the response of the bass from that instrument. However, if you use stereo subs and are hearing ture stereo bass, this delay between the sound reaching the left and right microphones is heard as natural acoustic mixing of the bass frequencies from those instruments in the listening room, just as it did in the original recording venue. The way the bass mixes in the room is natural, acoustic, and dynamic over time.

As an example of another real-world benefit of stereo subs located next to the main left and right speakers, consider the following example. You have your single subwoofer connected to the "subwoofer/LFE output of your pre/pro, and the sub is located next to your couch, and you have it crossed over at 80Hz (in other words, a pretty conventional arrangement). The distance from your listening position to the mains is 10 feet (the sub is 10 feet from your mains). You play a studio recording that has a bass player coming from the right speaker. He plays an open "E" string. Guess what? The fundamental frequency of that string (about 40Hz) will come from the subwoofer next to you. The second harmonic at around 80Hz will come from both your sub and your main speakers. The 3rd harmonic (and above) of the bass will come exclusively from your mains. As you can imagine, this plays absolute havoc with the harmonic presentation and structure and of the instrument! The effect is of the same type, if not to the same degree, of taking the tweeter out of your speaker cabinets and relocating them a couple feet away. Fundamental frequencies coming from one place, and the harmonics coming from another. The closer the notes being played are to the bass crossover frequency, the worse this disembodiment of the fundamental from it's harmonics will be, as the phase difference between the two will be greater due to the higher frequency. Adjusting the "phase" control of your subwoofer will not correct this: it only corrects for one specific frequency, that of the crossover, and musicians hate being restricted to playing only one note (at least good ones!).

Electronics designers take great pains to ensure that all the frequencies in an amplifer (especially at the low end) are amplified with a minimum of phase shift (this is the reason for DC coupling) - Why mess this up if you don't have to?

I notice an increase in sense of "air" and "realism" on almost all recordings that have live performers, even studio recordings. While low bass cannot be heard as "directional" in the traditional sense, the way the bass interacts as it mixes acoustically in the listening room certainly can be sensed and felt as added realism, and the filling in of that dimension that you are in the space where the recording was made. In addition, sound effects that were recorded in stereo for movies will have their bass reproduced in stereo. This is especially apparent in city street scenes when a bus or train passes. It just sounds more "real" as a result of the way the bass mixes in the room, just like it would if you were there. This benefit wil also be apparent when playing multi-channel discs like SACD and DVD-A, as the main left and right channels will give this added realism from the natural acoustic mixing of the low bass.

This setup is completely transparent to HT, multi-channel, and stereo playback, as anything you throw at it will have the bass reproduced correctly, regardless of format. No more fooling around with the logisitics of what to do with the subwoofer when playing SACD/DVD-A - the bass just reproduces seamlessly.
And best of all, if you have the two subs and extra interconnects, doing this costs nothing.

The ".1" channel is a convention that came from the movie industry, and had no precedent in the music recording industry. It works for movies since in a large theater, very few people are in the "sweet spot", so a mono LFE track is a reasonable compromise.

The ".1" track is a bad fit for music however. Forcing the "movie" model for speaker configuration on a system playing music where a significant number of people are in the "sweet spot" does not work well - it's a kludge in my opinion.

You're basically thinking of your main speakers/subs as _very_ extended full range speakers that can take the demands of film/HT, while at the same time being optimal for music. The LFE track in movies is simply being routed as a mono signal to both of your mains, where it ends up in both of your subs, just the same way it would be if your subs were connected conventionally to your pre/pro with a "Y" adapter. When playing music (either stereo or multi-channel SACD/DVD-A), the entire music spectrum, including the bass, is in stereo, and coming from where it should be: next to (or part of) your mains. One of the results is a cleaner, more coherent and focused soundstage. I've also noticed a heightened sense of realism, and of feeling I'm in the recording venue. Even hearing the low frequency content of the air conditioning rumble and "room tone" that exists in all large spaces in stereo rather than mono enhances the sense of realism. A side benefit is that in movies, you will hear the extremely low frequency content of stereo sound effects (like street scenes with busses and trains etc) that reside in the main left and right speakers in stereo - something that you won't hear in a movie theater, or even on a movie dubbing stage since the mains in these venues only respond down to around 40Hz.


If you have to use a single subwoofer for whatever reasons, at least take into consideration the above and place the sub as close to the mains as possible, preferrably equal-distant from both. This is still a compromise however, since a single sub is still a significant distance from the mains.

While it is true that as the frequency of sound goes down, the ability to locate the source diminishes, but there are a lot of other things to take into consideration. It's just not as simple as "bass is omni-directional so it doesn't matter where you put the sub"!


To configure your system to take advantage of stereo bass, do the following:

First of all, move one subwoofer as close as possible to your main front left speaker. Move the other subwoofer as close as possible to your main front right speaker.

In the 950’s speaker setup menu, set your main left and right front speakers to "Large". Set the subwoofer to "Off". Set your center and surrounds to "small" or "large" depending on their size. Most setups use the "small" speaker setting.

Disconnect the subwoofers from the LFE/Subwoofer output of the 950. Run an interconnect from the main left and right outputs of the 950 to the "line input" of each subwoofer – the left out of the 950 to the left subwoofer, and the right output to the right subwoofer. Run an interconnect from the "line output" of your left subwoofer to the input of your left channel power amplifier. Run the right subwoofer’s "line output" to the input of your right channel power amplifier.

Set the crossover frequency of both of your subwoofers to the crossover frequency you used previously in your 950. You will probably need to re-adjust the level controls of your subwoofers.


[This message has been edited by soundhound (edited April 01, 2003).]

Soundhound, I would love to try this one, have been pondering your posts on stereo subs from the past and my logic tells me the quest achieving what I like in music could benefit greatly from this setup.

But space!. You guys would die if you saw my house. (Picture cottage…and I don’t refer to style).
Right now the Def tech is shoehorned behind the display into the triangle nook it creates, equadistance from the mains.

Something like Gonks SVS (I could literately fit inside of), would not fly in this sq.footage challenged location.
Starting (and stopped) a search on REL subs, without checking out their dimensions.
I feel you might have an inkling of how my personal tastes run in sound, do you think I would benefit from finding one very nice very musical sub Vs the tradeoff of having to find units [very very} small, assuming a degraded performance after factoring cabinet size restrictions, - in stereo? I have a feeling you will pick the stereo setup, but wonder. Any recommendation for quality built mini-me subs?


[This message has been edited by Smart Little Lena (edited April 01, 2003).]

Lena:

If you don't have the space, then obviously stereo subs are not an option for you. BUT - do you really need to park your cars in that big garage - ever built a custom room? I think you "need" a larger HT room! (just don't sneak up on your husband while he's cutting the wood for it!)

Lena,

In addition to the garage, you can use the kitchen space towarts the HT room. Eating out in restaurants is a very enjoyable and fun thing to do. Plus you can sell the Wedgewood, Waterford, silverware and kitchen appliances, using the money towards the HT room and equipment.

Do you really need an indoor bathroom? An outhouse, on the other hand, ...

Paul

p.s. I have two Stryke brand AV15 subwoofer drivers and a Crown K1 amp awaiting. As soon as I get boxes made for each of the AV15s, I'll be doing the stereo sub route.

[This message has been edited by Paul J. Stiles (edited April 01, 2003).]

just don't sneak up on your husband while he's cutting the wood for it!

awohoow low blow!

An outhouse, on the other hand !!! some of you guys have WAF, I on the other hand fight, ACDD
(acoustically challenged diminutive dimensions).

I actually started drawing up a whole new house last summer in a moment of wishful mulling…it seemed to start and stop around the AV area which was about as far as I got with my theoretical floorplan, (I lost interest when I had to draw the outhouses) (I think I have issues).

Regarding stereo subwoofers, Dr. Griesinger of Lexicon observed the psychoacoustic phenomenon where bass coming from directly in front of you is perceived as being inside your head instead of in front of it. To this end, he came up with something for the Lexicon processors called Bass Enhance, which takes the bass from the center channel and redirects it to side subs or full-range mains, plays a few games with the phasing, and in principle offers a significant advantage over bass without this technique.

In practice, this technique has been shown to be highly room- and position-dependent. It's an option on the processors, so some people (like myself) use it, and others do not.

Jeff

Folks,

I've used multiple subs for years - not for "stereo" reasons but rather because I've found it much easier to balance the sound (bass) throughout the listening area when using more than one sub.

In my main theatre's current set-up I've recently gone to using three subs (Velodyne Servo 1200, B&W ASW1000, and a passive home-built from my engineering design days that uses extra-high density particle board, four 6 1/2" Polk drivers, and a 12" Polk passive radiator) in what is a relatively small room. It's producing the best (admitedly a subjective term) sound that my set-up has ever produced. On top of that my mains are large towers with a tested -3db point of 27Hz - so they're not lacking much in the way of "musical" bass either.

On the subject of stereo subs, I'm sure that some people can, or at least think they can, hear a difference. In my case, using only two subs, located close to their respective left and right front speakers, I hear no difference at all - and neither do a number of fellow listeners who have done some "blind" listening tests with me. I currently use an ICBM-1 which, as you know, has a switch that allows mono or stereo sub operation, so I can switch between the two modes instantaneously. Nobody hears a difference. Nobody can tell which is mono or which is stereo. Even though I'm using two different subs, and even though there is no way that I would ever be able to match the subs up exactly in terms of output level (I use a Radio Shack analogue level meter), cross-over point (I rely on the indicated settings which are probably off by at least 10-20%), or low frequency extension (since the Velodyne goes much lower that the B&W). So despite even these differences, there is no detectable difference - at least not to my ears. I can only imagine that identical subs, set up identically, would yield even less of a difference.

Just my opinion / observation. Not that I am doubting anyone who does notice a difference. That's the beauty of this obsession (er hobby) called home stereo / theatre.

Jeff

The benefit of having stereo subwoofers is greatly recording dependent. The recording method that takes the greatest advantage of capturing bass in stereo is "spaced omnidirectional". This microphone technique captures both intensity and time information. Co-incident and near co-incident techniques such as X-Y, crossed figure 8s, ORTF etc, capture only intensity differences, and thus are less likely to display enough information to make stereo bass audible. Studio recordings can go either way, depending on the particular microphone techniques employed, how many musicians are playing together in the same room, and panning.

On recordings I make, I use three spaced omnidirectional microphones in much the same manner that the classic Mercury recordings were made, and which Telarc mostly uses. The effects of stereo bass are most apparent when recording in large spaces with long low frequency decay times. Several recordings of pipe organs I've made in large churches display a beautiful sense of space from the directionality of the low frequency ambience.

Soundhound,

I should introduce you to Dr. Griesinger at some point. I suspect you'd both benefit very much from a technical conversation.

Jeff

Soundhound I applaud you and I absolutely agree with everything you said although I could not have explained or given the details as well. Stereo subs set up correctly in my system was the single best improvment in sound quality that I have made. (with the exeption of the speaker purchase) I do exactly as you said and have the subs directly beside the mains. I do have the LFE connected along with the main L/R channels but the controller for the subs allows me to defeat the LFE input and just use the mains signal. Your organ bass comment is right on because on of my favorite DVD-A's is Deep Purple and that Hammond sounds better with the stereo setup. No doubt in my mind.
SH I do have a question though. Do you think that maybe certain setups wouldn't benefit if the main L/R speakers are to close together? It seems a lot of people tuck the speakers as close to the monitor as possible which isn't how I have mine set.