this is the correct way to treat the LF of a multi-channel audio system.

i've played electric bass for some 36 years. any recording of electric bass is done DI, whether live or in the studio. though i appreciate someone's desire to use stereo bass reproduction (though the choice of good source material is relatively small), and i really don't care what sort of matrixed synthesis of the original source someone may prefer to design, manufacture or use at home (unless it was MY recording), i don't see the requirement of 2 outputs for redirected bass. nevertheless, it costs next to nothing to implement, so why not?

the really important thing is the discrete LFE output to it's own system of filters/slopes/delay/sub/amp and level control. as soon as you understand the potential of the 6th channel, you know that you shouldn't just sum it with redirected bass.

the demand on a sub is drastically reduced for movie formats. add a HP filter and you have a full range channel for dvd-a/sacd. use a LP point and slope that best suits LFE while not destroying the critical adjustment needed to reintegrate redirected bass. significantly reduce intermod distortion. ease placement problems by reducing the size of the subs. have a 'musical' sub and a 'movie' sub in the same system. be able to calibrate the LFE in relation to the redirected bass levels...on-the-fly if need be. invent new instruments. and, yes, even matrix the 6 channels instead of 5.1 (for those who like such things ) into gozillion.1 without changing anything but to add an LFE output. any one of these points warrants the output. it costs nearly nothing. lexicon is right for doing it and the 3 points they bring up to justify it (less demand, level adjustment and separating it from derived bass) are dead-on correct.

one more thing...once you've 'enhanced' my bass lines, promise you'll stop there and not compress, add reverb or flange or run your subs 6db 'hot'??

Many thanks to all that have contributed to this topic... this has the richest, most informative. and most relevant discussion I can remember in any audio forum. Although I am not shocked, I am in awe of the level of technical knowledge and uncommon sense displayed by so many of the Gunslingers here.





I have some basic questions concerning the Stereo Sub set-up, and the configurations suggested by SH, Bossobase and others...

Question #1: Does the inclusion of an Outlaw ICBM provide additional benefits to a Stereo Sub configuration, over and above the use of the 950 alone? The LFE Mix control seems to be one benefit, but it becomes irrelevant if the LFE channel is made discrete.

Question #2: Assuming the mixing of the LFE signal with redirected bass to Left and Right Stereo Subs is potentially as serious as bosobase suggests, would it make sense to configure a system with three (3) subs? Two subs dedicated to the redirected bass from the 5.0 signal; and one (possibly more) dedicated to the LFE (0.1) signal...

My configuration currently uses stereo subs which are located directly adjacent to (and aligned with the face of) Front Left and Front Right floor standing speakers. I am using an ICBM to send redirected bass to the Stereo Subs, and mix in the LFE signal as it is designed. Otherwise, it is similar to the set-up that SH suggested in the opening post.

Question #3: Is a potential solution (system improvement) as simple as this?...
a) Unplug the LFE input to the ICBM, and stick it in a new dedicated Sub.

With all speakers set to Large, everything should work, with no cross contamination between the full range (up to 150Hz) LFE signal, and the redirected bass to the Stereo Subs (which are crossed over at 60Hz). Yes? No, I think...

Question #4: How to overcome the Outlaw 6-Channel Bypass Mode "base management" algorithm?... The 6-Channel Bypass Mode sums redirected bass (at a fixed 80Hz crossover point) from the 5.0 channel signal and mixes (sums) this with the LFE signal. The full range 5.0 signal can be sent to the speakers by turning Bass Management "Off," but the Outlaw LFE output is not suitable to the purpose of separating the LFE from the rest of the system signal as it still contains the under 80Hz signal from the 5.0 channels. What to do, what to do? Perhaps... but I don't know...
a) An A/B switch for the low level LFE signal that allows the user to bypass the 950's Sub I/O processing section(s), therefore connecting the dedicated LFE sub directly to the source. But... this would take out the 950's control of the LFE channel volume. What a mess! The LFE signal level would need to be constantly adjusted when changing the volume in 6-Channel Bypass Mode and then again when switching back to the other source modes.

It would probably easier to bypass the Outlaw 6-Channel Bypass Mode altogether. Perhaps someone could suggest a more simple product alternative that could perform this purpose... or a better overall system configuration? I am aware that there are Pre-Pro's that allow the user to maintain a discrete LFE channel, with separate outputs for stereo subs dedicated to redirected bass. This is a nice feature of Lexicon's MC-12(B or no B) and the new Parasound Halo C1 unit.

I am with other Outlaw owners who are looking forward (with our hands together) to the next generation of the 950. Bass management that provides significantly more flexibility in system configuration would be first on my wish list. The ability to assign individual settings for each source a very close second. Even though I don't like the logo... I would silk screen it on my front door if the Outlaws keep their eye on performance enhancements that we can enjoy in a dimly lit room.

Again, thank you all for interesting reading...


P.S.: I have found that it becomes especially beneficial to have good sound isolation spikes for the sub and the Main Left and Right speakers when they are placed so close together as they are in my system.

[This message has been edited by AGAssarsson (edited April 29, 2003).]

As long as your subs can take the combined re-directed bass in addition to the LFE, there is no problem with recombining the signals. There is a disadvantage to using a dedicated LFE sub however, and that is that the LFE will be only reproduced by one sub instead of two. I prefer to have the added oomph of having the LFE reproduced by more than one sub personally, in addition to the room mode averaging afforded by multiple subs.

The ICBM is a workable solution, however I think (I could be horribly wrong) that the stereo sub crossover ability is limited to a fixed 80Hz frequency.

Am I missing something or is not the Center Channel just as important as left and right? I would think that the ultimate would be to have Left Sub, Center Sub, Right Sub and LFE (.1) Sub.

For multi channel audio discs, yes, the center has the same low bass requirements as the other front speakers. For movies, in practice, very low frequencies are kept out of the center speaker because the mixing engineers need to keep the channel open for dialogue, which is the most important element in a film's mix (from a mixing standpoint). Low bass eats up the available headroom in a channel, which is the main reason for the LFE.

Stereo subs operating with the left and right fronts (with center and surround bass re-directed) is a reasonable compromise given the nature of most source material.

The ICBM has a switch that allows the user to select between mono or stereo sub output from the L & R RCA sub terminals. In stereo mode, the Left Sub gets a full lowpass signal from the Front Left and Left Surround channels, and half the signal from the Center Front and Center Rear channels. This is explained in the ICBM Manual (Page 14, pdf file available @ this site).

I have tested the crossover response, and the ICBM does permit independent crossover settings for the following channel groups:
a) L & R Fronts (2 channels)
b) Center Front (1 channel)
c) L & R Surround (2 channels)
d) Center Rear (1 channel)

The crossover choices are 40Hz, 60Hz, 80Hz, 100Hz, 120Hz, and Bypass for each channel group.

The effect of flipping the switch from mono to stereo varies significantly on recordings with good bass content. I believe many recordings have mixed (summed) bass content to the L & R channels, and therefore have defeated the opportunity for stereo bass. I believe this underlines SH's point regarding the splitting of a specific musical instrument's sound signal, which can happen because:
a) the listener definable Sub/Main crossover setting (where the Subs are located distant from the mains), and...
b) the arbitrary mixing point chosen by the engineers in the studio (where low bass is summed equally to L & R, assuming the sonic characteristics of the listeners speakers and system are not up to reproducing full range stereo signals).

As SH states... "The closer the notes being played are to the bass crossover frequency [or low bass mixing point], 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".

One example... The Talking Heads and TomTom Club have very good stereo recordings of low bass frequencies, with lots of electric bass and all kinds of drums. The benefits of Stereo vs. Mono Sub-woofing are very evident. With stereo subs, the location, image and phase coherence of each instrument provides a sense of realism that is significantly better than with the ICBM switch in the mono position.

While I have not perceived a problem with the lack of a discrete LFE sub (or subs), I believe that Bossobase's quest for independent LFE signal is a good one. In my opinion, it is like chicken soup... will it help???... it couldn't hurt...
but it will cost you.

Best Regards

[This message has been edited by AGAssarsson (edited April 29, 2003).]

answer to Q #3: if your ICBM is placed between the player and the preamp, then yes. you may, however, need a seperate preamp to boost the LFE signal from your player to your sub's amp.

adjustment of LFE volume separately is not that big a problem (actually, it's a good thing to be able to balance the levels properly, which you'll learn to do as you experiment). i do it regularly. my LFE preamp is set next to the player. i simply set the volume for each disc when i load the disc.

remember, this will only work with dvd-a/sacd. unfortunately, the player will output the LFE through both the analog SW out AND the digital out. this means you'll get LFE into the 950 when in digital modes along with LFE into the 3rd sub.

obviously, LFE summed with RB 'works'. it just doesn't work as good.

try the setup described in your Q #3 with 1 sub as a dedicated LFE sub and the other one as a redirected bass sub.

also remember that the added 'oomph' will still be there as multi-channel audio discs use the LFE channel (by and large) for that purpose. you'll still get the same signal into the 2 subs almost always. you'll just get full use of the LFE channel AND best reintegration of RB.

the ICBM has a glogal LP of 150 hz on the LFE channel, so try that first (disable your sub's x-over). i use a 2-way x-over on my LFE system, with selectable x-over points. it works great for a full range 6th channel as some sacd discs warrant it, and looking toward the future.

dial the RB sub to best integrate it with your sats. try 80 hz for all sats first, then venture from there as your sats permit.

wherever the 2 subs are placed, make sure they are both precisely the same distance to your ears.

this is a convoluted work-around, i agree. i also await the new outlaw having a dedicated LFE output.

finally, the discrete LFE assumes a good music sub and a good LFE sub are in the system, with proper phase, levels, x-overs, slopes, etc. no setup will make a poor system sound good. experiment. it's worth it.

Thank you Bossobase.
I will give it a try next month, when I can borrow a good preamp from a friend.

I have two Velodyne HGS15 Series 2 subs, so I think they are worth the trouble to test this feature. My speakers are large floorstanders, but I cross them at 60Hz, as they sound better. Ultimately, I will be getting a new sub for LFE, when Outlaw decides to put the dedicated LFE channel output on the 950 version 2.

I will let you know how it works… Thanks again.

sorry for this incorrect suggestion (long day). if you configure your LFE sub per question #3, you'll use your sub's x-over and bypass the ICBM.

I have owned Def Tech 2000's tower speakers( with "stereo subs" ) for years ( you either love 'em or hate them...) and use a "y" splitter from front L/R outputs of my pre amp (soon to be a 950) going to the 2000's "full range low level inputs" and the other part of "y" going to amp running the mid/highs for the 2000's. This is how Mr. Pelkowski from Def Tech has recommended me to set up my speakers for "true" stereo subwoofers. I love what I hear, and although I am certainly not an expert at the scientific reasons for it all, it sounds pretty darn amazing....(right now using Yamaha CX-2 Pre Amp..really nice Pre Amp by the way, and am keeping just to use the Phono outputs.... and Fosgate Model 4 Processor....)
this thread has (as usual) been really informative.....you Outlaws are the best when it comes to helping each other out with suggestions, etc....
just had major spine surgery and it is holding me back from upgrading right now ( I want to, I want to, I want to...I NEED to!).....
anyway....
first need to sell my old equipment on EBay or Audiogon...and move on up to the 950/770 combo.... boy, I cannot wait!!!!! I think stereo subs are worth it if you can do it, and once again have learned alot from these kinds of posts....Love this part of Outlaws website, and just had to chime in.....
better late than never.....
It's the only website I look at every day.....amazing stuff and amazingly intelligent gunslingers out there.....love it!!
well, anyhow,
Stereo subs are a big plus in my opinion....