I don't think there would be any problem with the stereo subwoofers, but I wouldn't want to put speakers that close together in the first place. Having speakers close to big reflective objects can also play havoc with imaging.

it should be noted that the stereo sub setup will produce best results with acoustic recordings only, as there is almost never a microphone involved in electric bass (or any electronic instrument) recording. DI is used, and that signal is normally 'placed' equally in the l&r mains (not accounting for the 6th, or point one channel in sacd/dvd-a).

lexicon's dr. 'G' (with bass enhance) is taking a page from bob carver's holograph generator and requires PRECISE placement of both speakers and listener's ears. these 2 points are, no doubt, why bass enhance is said to be room and source dependent.

lexicon is the only pre-pro available with stereo sub outputs AND A SEPARATE LFE output.
my guess is that this configuration allows for the bass enhance feature, and is the only reason for it. otherwise, lexicon would be touting the many benefits of this configuration. the simple fact that bass enhance won't work if the LFE signal is summed with the redirected bass signal tells you that soundhound's setup won't either when there is LFE content.

80 hz is too high for a subwoofer.
1 subwoofer to reintegrate redirected bass into the soundfield is enough when the LP point is around 40-60hz.
the second subwoofer is needed for a discrete LFE signal, as the summing of LFE with redirected bass is where almost all bad things happen (intermod distortion, too much demand placed on a single sub system, crossover holes/humps, loss of any chance at stereo bass, phase problems, etc).
stereo subs, placed as soundhound suggests is a plus, but only for acoustic, 2 channel recordings and only if LFE ain't summed into them. also, the fact that 40hz is a wave that's 28 feet long, and therefore is reflecting off many surfaces before it ever gets out of the speaker, matters (this is, in fact, why bass is omnidirectional). soundhound has matched, ear level, direct radiating subs, so he hears the note first and the reflected notes afterward. most HT subs are downfiring or direct radiating, but sitting low to the floor and in the corner to use the corner for gain, which greatly lessens the stereo effect, especially at 40 hz.

dr. 'G' spent too much time developing bass enhance and overlooked the fact that the key to correct multi-channel audio bass is a DISCRETE LFE SYSTEM. among many other benefits of a discrete LFE system, it allows for a full range .1 channel by simply high passing a satellite speaker off the LFE sub (in dvd-a/sacd).

bottom line...i agree with soundhound, as far as placement of the subwoofers. i know the end result is real, and not perceived or imagined. when i record bass tracks in the studio, i have to play alone, while a monitor plays the song because headphones cause the music to arrive instantly to my ears and that tiny discrepancy in time arrival throws my timing off completely (as i am used to live performance much more so than studio work. i agree with lexicon as far as a discrete LFE output. i agree with stereo subs, but don't think they are the important part of the setup, unless 2-channel acoustic recording playback is your primary interest, and you have the room to properly place 3 subwoofers.

of the 3 things, discrete lfe output (and subsequently, crossover, phase and delay processing of same) is the most important, because, only then can you properly set up any sort of subwoofer system for redirected bass.

I fail to see how routing the LFE into the stereo subs where it is reproduced by both, will not work. The LFE in the case of films is synthesized in almost all instances anyway - I know, I create some of them! Please educate me on why sending this signal to two subs equally "will not work"

I said from the beginning that this was best for acoustic recordings, and recordings in large venues especially. Last time I checked, this applied to a significant number of recordings out there. I know it does not apply necessarily to some studio recordings. If you listen to jazz and classical music at all in stereo, this is where the benefit is.

I'm amused by some of the resistance I've encountered on this subject on this forum, and on another I've posted this on. Maybe I'm just too dense and don't get it - maybe the marketing machine has convinced too many people that the LFE is sacred and must be reproduced only by a dedicated subwoofer. I've simply tried to describe a simple and cost effective way to make a HT system that is also used for music listening as effective as possible in both formats.

There are a very significant number of people who do listen to two channel (stereo) music. To ignore it's existance is turning one's back on a vast library of recordings that will never exist in a multi-channel format. The music is the message, NOT the way it's delivered - 5.1 channels, 2.0 channels, or even 1 channel.

[This message has been edited by soundhound (edited April 05, 2003).]

I'd just like to add a couple of comments to my earlier posting on this topic.

My guess is that anyone who has gone from using a single sub to two or more has noticed a big difference - and hopefully an improvement. The question is whether you hear a difference between two subs in mono, and two subs in stereo. And I would argue that, as with all listening tests, unless you can keep everything else equal, and unless you can transition between the two states in a very short period of time, you might be giving your brain too much time to forget what it has just heard. "Time" is a serious factor when it comes to our ability to make comparisons. (Heck, our sense of hearing varies throughout the day depending on any number of factors - something that I proved to myself by taking a number of audiometry tests throughout a single day and seeing that my sense of hearing did indeed vary slightly from one test to the other.) In my case, by having to do nothing but switch between mono and stereo on my ICBM, I'm getting as close to an instantaneous switch in states as possible - and then only when I have someone standing behind the equipment racks to make the switch while I listen. (It's also important that the listener does not know the initial state (mono or stereo) and that a "switch" between states can be no switch at all, when conducting the tests.)

Since my first posting on this topic, I've given it a bit more thought and wonder if stereo subs might produce a noticeably different sound compared to a two-sub mono set up in the case where the front main speakers have less bass extension. I can't easily swap my large mains for less bass-capable speakers, however I CAN use the ICBM to simulate this by simply changing the crossover point. A series of listening tests with the ICBM on bypass, 40, 60, 80, 100, and 120 HZ should either prove or disprove the hypothesis.

When I can find the time I'll see if I can set something up and will report back on the results.

Regards.

Jeff Mackwood

Instead of trying to "prove" or "disprove" this, why don't you simply try listening to a good recording with this configuration and if you like it, keep it, and if you don't like it, put it back the way it was?

Doesn't seem like a terribly big deal to me, but then I have a simple mind, and that simple mind doesn't see any benefit in going from stereo to mono below a certain frequency if I don't have to!

[This message has been edited by soundhound (edited April 05, 2003).]

[QUOTE]Originally posted by soundhound:
[B]I fail to see how routing the LFE into the stereo subs where it is reproduced by both, will not work. Please educate me on why sending this signal to two subs equally "will not work"
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the LFE sub, for movie reproduction, must be capable of subsonic to 120ish hz PLUS redirected bass from 5 satellites (or, 2.5 satellites, in the case of stereo subs). what happens to the 40hz bass guitar E string note when a 30hz (example) LFE+10 note is blasted on top of it in the same amp/speaker? if it's mixed too loud, how do you compensate? if it's out of phase, how do you adjust it? what happens to the LFE's playback capabilities when the sub's LP is set at 40hz to blend with a 40hz HP selection? what sort of subwoofer/amp is needed to survive the assault, and will that sub/amp be the best one for music? what does it do to the stereo sub effect you tried for in the first place? what happens if the .1 channel is a height channel, or contains vocals (in the case of dvd-a/sacd) or other higher range info?

1. adding 5 channels @ 103db and 1 channel @ 113db (LFE+10db) results in a requirement for 121db for the sub(s). testers who have played the dolby test dvd know that 'practically all' systems have a serious limitation in this area.

2.a sub system with a 1w/1m sensitivity of 89db requires 1600 watts to acheive 121db (vs 260 watts @ 113db).

3. intermod and harmonic distortion are unacceptable.

4. volume levels (between LFE signal and RB signal) are not adjustable when they are both summed into one signal.

5. manufacturer's claims notwithstanding, no sub with this capability is worth a crap for music.

6. the .1 channel is unnecessarily limited by the necessity to select the proper LP point to reintegrate redirected bass into the soundfield from which it was extracted.

of course, it 'works' the way it's done now...just not very well. the best education is to segregate the LFE signal in it's own system and run some tests yourself.
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I said from the beginning that this was best for acoustic recordings, and recordings in large venues especially. Last time I checked, this applied to a significant number of recordings out there. I know it does not apply necessarily to some studio recordings. If you listen to jazz and classical music at all in stereo, this is where the benefit is.
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i offer no resistance to the above statement, and apologize if i gave that impression.
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I've simply tried to describe a simple and cost effective way to make a HT system that is also used for music listening as effective as possible in both formats.
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the post is appreciated...in fact, i LOVE this thread. as i said, for 2 channel, acoustic reproduction, i believe your suggestion is a very good one.
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There are a very significant number of people who do listen to two channel (stereo) music. To ignore it's existance is turning one's back on a vast library of recordings that will never exist in a multi-channel format.
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agreed.
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The music is the message, NOT the way it's delivered - 5.1 channels, 2.0 channels, or even 1 channel.
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this is where i disagree. the message of music that's written for and properly mixed in 5.1 cannot be delivered in another format or with bass that never arrives at all, arrives distorted or destroys your system. it's like painting a masterpiece, only to be asked to deliver it to be viewed in watercolor.

the answer is a simple one. 2 discrete outputs, 1 LFE, 1 RB (or, 2 RB, if you prefer stereo RB) and a switch that sums the LFE and RB into the RB jack for those who prefer the current system. not a lot to ask.

Bosso:

Your points are well taken, but I think you way overestimate what is being demanded of the subwoofer by the LFE channel. Also, the listening levels you are talking about will not be used in any home enviornment, at least by anybody who wants to keep their hearing intact. I don't even listen at those levels!

I think you are also blowing up the issue of potential phase problems too. They just don't exist in the real world, on real world movie soundtracks.. Movie LFE tracks and the bass in the other tracks just isn't that radical - mostly it consists either of slowed down natural sounds, of filtered pink noise that has had an envelope overlaid, or sounds processed by a DBX bass synthesizer. There are no "phase" problems to be had; they would immediately make themselves known during the film's mixing process. It is routine during the mixing process to do "crashdowns" into stereo or even mono in order to catch any potential problems down the road.

The film's mixing engineers take into account the fact that the film will be played under much different circumstances, and on lower quality system than on the dubbing stage. They mix the bass accordingly, and they have phase meters where they monitor for potential problems.

There just isn't as much to worry about as you seem to think there is.

[This message has been edited by soundhound (edited April 05, 2003).]

my system consists of a separate preamp, crossover (LP/HP, for full range use of the .1 channel), slope selection, delay and 360 degree phase control, (designed in consultation with and built by phil marchand) a pro sound amp and 1-18", 10 cu. ft. speaker for LFE only, which is taken directly from the player.

the 950, through the SW output sends only redirected bass to another pro amp and 18" sub. the 950 handles the LP for redirected bass.

when i play LOTR for whomever is there, (i don't have the LFE bug, because i get LFE from the player) they always are very impressed with the insane bass levels.

i, however, cringe as i watch the clip indicators (both the preamp's and amp's) as they flash red. i don't know what the engineers took into account, but this disc has everything the format can muster.

now, imagine it's summed with the bass from 5 channels into the average plate-amp-powered 12" sub, without the built-in limiters those products use. it would not survive.

and, what happens to the music that's playing while the LFE plays? i can switch from discrete, 2 subs, to summed, 1 sub...on-the-fly. the difference is dramatic.

it's even more dramatic a difference when playing sacd multi-channel. i can use different LP points, slopes and volume to dial each disc's LFE content without effecting the redirected bass, which belongs to the 5 channels it was derived from and requires different LP point/slope/volume. you only need to hear the difference and draw your own conclusions. like you say above...just try it. you hear a difference and like it, keep it. if not, switch back.

my phase concerns don't center on the source, but the processing and playback of it. a subject that i'll address when it's not so late.

soundhound...thanx for everything.

Bosso:

From your description of LOTR on your system, I can only imagine that you have your LFE cranked far beyond what was intended. I played this film in my room several weeks ago (in DTS) and while the bass was up front and constant, it was not out of the oridinary or "extreme" by any means. I know the calibration of my room since I have to transfer projects from here to dubbing stages with no surprises in levels, bass or otherwise. I normally play back films with a 6db boost on the subs over what the film was mixed at - I like bass as much as the next guy. When I mix, I return them to flat.

If you were to visit an actual dubbing stage where films like this are mixed and listen to the frequency balances, I am quite sure you would shocked at how "mild" the LFE bass really is in the mix of the same films you listen to at home. The engineers will never sacrifice the intelligibility of the dialog in order to get more "boom" from the soundtrack. There is only 20db of headroom above the nominal 85db level of dialogue to work with before the master recorders reach clipping. Loading them down with too much low bass leaves no room for more important things like the music, dialogue and the other sound effects. The purpose of the LFE track is to reproduce this bass so that the main speakers don't have to deal with this power and headroom-robbing signal.

If your clipping lights are flashing constantly, I really think you have the LFE track boosted too high. You might like it like this, and I can understand that, but you also are probably not hearing the film's bass as it was intended.


[This message has been edited by soundhound (edited April 06, 2003).]

An EXCELLENT thread, gentlemen, congratulations.

(Soundhound, practicing your typing?)