If there is no "stereo bass," then why use mono output for two channel listening? Why not just use either the left or right channel and send that to all subs? Will there be a difference?

I had a few minutes of free time last Monday evening, so I decided to do a little stereo bass experimenting. I currently send the full range digital PCM stereo signal to my DCX2496. I send the left channel to my left MFW-15 and the right channel to my right MFW-15 with an 80 Hz L-R 24 db low pass. I wanted to know if both channels sounded the same. I turned off the main amplifier so only the subs were on. Using the DCX2496’s computer software I toggled the mute on and off on each sub and compared them to each other. I could not tell any difference in content between the two of them using a few different songs (as should be expected if the bass is not decorrelated). I have stored both a stereo and a mono setting on the DCX2496 and have switched between them frequently in the past while listening to music. I have never noticed any change in imaging between the two settings. However, I have preferred the stereo setting.

When speakers are set to small with a 80 Hz crossover, I assume that receivers combine the bass below 80 Hz from the L/R channels and send this info to the sub(s) as a mono signal. To duplicate this using the DCX2496, I then combined the left and right channels and sent this to the left sub. I let the right sub still receive just the right channel. I compared back and forth and the sub that got just one channel sounded cleaner and more articulate. I found that on the mono sub the notes seemed a little thicker and bloated.

If bass is not decorrelated, is it necessary to combine the left and right channels for a mono configuration?

By the way, for movie listening the 5.1 signal is down mixed to the stereo signal. Therefore, I could still use this method for movies without losing either the LFE channel or bass below the crossovers in each speaker.

Nobody ever said there was no stereo bass. Bass is fairly omnidirectional, but that's not the same as saying there is no stereo bass. The right and left channels do not necessarily carry the same bass information. If you only used one or the other for bass information, you would be missing whatever info is on the channel you didn't use.

Nobody ever said there was no stereo bass. Bass is fairly omnidirectional, but that's not the same as saying there is no stereo bass. The right and left channels do not necessarily carry the same bass information. If you only used one or the other for bass information, you would be missing whatever info is on the channel you didn't use.

There have been many threads here at AVSForum regarding stereo or decorrelated bass. Here are some comments that I have read:

Dr. Geddes - The fact is that decorrelated bass on source material is all but non-existant.

Bossobass - Most electronic bass is not recorded in stereo because it simply isn't possible to create a stereo image from a mono electronic signal. As a result, you'll have to seek out and acquire the rare, high quality multichannel acoustic bass included source. It won't matter if it's stereo or 10.2, it only matters that the source is acoustic and was recorded to be captured in a multichannel format.

Mark Seaton - Examination of a wide range of recorded music will find stereo bass exceedingly rare.

Nobody ever said there was no stereo bass. Bass is fairly omnidirectional, but that's not the same as saying there is no stereo bass. The right and left channels do not necessarily carry the same bass information. If you only used one or the other for bass information, you would be missing whatever info is on the channel you didn't use.

Do you have any examples of recordings with stereo bass for us?

Nobody you quoted said it did not exist, but that it is rare. Rare by definition means that it does indeed exist. All it takes is one recording that has an acoustic bass in only the right channel or the left channel to cause your system to have a 50/50 chance that it isn't going to play the bass line.

Also, what sort of crossover are we talking about? At what frequency do most of the tracks stops being in stereo? 50hz? 80hz? 100hz? There is no universal rule. Depending on your crossover, you may be missing some bass info if you only use only one channel as the source.

Do you have any examples of recordings with stereo bass for us?

I would have to do some listening searches through my collection to find some, but I have definitely listened to bass lines that were only in one channel or another. Also there are bootleg recordings that do not adhere to any typical industry standard.

In this article, Tom Nousaine proves there are modern CDs with true recorded stereo bass, but in his opinion concludes it's best to sum the left and right channels for playback.
http://www.nousaine.com/pdfs/Stereo%20Bass.pdf

I used to have a few bass CDs for car audio that had stereo bass. You could hear as well as feel it sweep from one side to another. I can't recall any of the titles of the discs though. However, I am guessing you want to find actual music with stereo bass. What about stuff with string bass, and you hear it off center or even on one side of the stage? or for that matter, drums are usually placed off center and even on the opposite side of the string bass. I hear this stuff in my left and/or right channel with or without a sub connected. Of course, the sub just enhances the sound.

I used to have a few bass CDs for car audio that had stereo bass. You could hear as well as feel it sweep from one side to another. I can't recall any of the titles of the discs though. However, I am guessing you want to find actual music with stereo bass. What about stuff with string bass, and you hear it off center or even on one side of the stage? or for that matter, drums are usually placed off center and even on the opposite side of the string bass. I hear this stuff in my left and/or right channel with or without a sub connected. Of course, the sub just enhances the sound.

Was it one of the Bass Mekanik discs? I have one I still use to setup subwoofers at home because of all of the frequency sweeps and test tones that go low! It's still the only disc with a tone that will literally "shake" the rooms walls when played back. ;)

Well, I had about 15 bass CDs, so I would guess that Bass Mekanik was one of the discs that had stereo bass, but I know there were a few others. Not just as test tones either but in the songs.

I believe the concept is sound, for stereo sub bass whether it’s two-track of six-track Dolby stereo with split-stereo/surrounds.

I’ve done some independent frequency waterfalls of Dolby six-track mixes and there is noticeable difference on left and right fronts and split-stereo/surrounds as well.

Most portions of stereo bass/sub will be equally sent to left and right (phantom) with only a few occasions of deep low independent shudder or slam, on the left to right, what ever. Point is it worth it, how many are really going to notice the difference?

I might notice the difference and until I buy matching subs as I have two already except their different sizes and therefore not matching, doesn’t mean their rubbish.

Also you’d have to make sure the lows in the lower register have uniform smooth frequency response with fewer dips and peaks so it’s the same old story. Back to square one, to make sure frequency is smooth enough, otherwise it’s going to be boomy/muddy.

Also I’m running DCX2496 only thing is I’d need a few more of them for the concept to work.

Sounds like fun.:)



By the way, for movie listening the 5.1 signal is down mixed to the stereo signal. Therefore, I could still use this method for movies without losing either the LFE channel or bass below the crossovers in each speaker.

Except LEF.1 discrete track will be sent equally to left and right while some portions that have independent hard left/right from front to some surrounds as all movies from the 1970’s to early 1990’s had monaural surrounds only few that had stereo surrounds from 1978 Superman the Movie being the first one.

I’d say you’d have about 90% phantom monaural sub bass and 10% independent stereo sub bass.

But hold on!

Some signals can crossover from left front to rear right in stereo, haven’t noticed as of yet hard low end.

What about that silly film Pulse, now that scene you know which part, that has lows more or less of the same value on the primary five channels, it’s a disorienting mix.]

Chapter 15
Time 69 minutes 31 seconds to 70 minutes 58 seconds

There’s a subtle difference in the frequency waterfalls that I took from this naff film a few months ago, I can’t stand it, its pants.

http://i282.photobucket.com/albums/kk279/SpectrumsubbassLFE13417/Pulseleftfrontchapter15.jpg

http://i282.photobucket.com/albums/kk279/SpectrumsubbassLFE13417/Pulserightfrontchapter15.jpg

http://i282.photobucket.com/albums/kk279/SpectrumsubbassLFE13417/Pulseleftsurroundchapter15.jpg

http://i282.photobucket.com/albums/kk279/SpectrumsubbassLFE13417/Pulserightsurroundchapter15.jpg

http://i282.photobucket.com/albums/kk279/SpectrumsubbassLFE13417/Pulsecentrefrontchapter15.jpg

http://i282.photobucket.com/albums/kk279/SpectrumsubbassLFE13417/PulseLFE1chapter15.jpg

http://i282.photobucket.com/albums/kk279/SpectrumsubbassLFE13417/PulseLFE1chapter15-10db.jpg

Do you have any examples of recordings with stereo bass for us?
"Live And Let Live," from Daniel Amos' Vox Humana album is recorded with true stereo bass. Also, Pink Floyd's Wish You Were Here disc has one track with the bass signal alternating back and forth between the L/R channels. Some early Beatles albums had the bass in one channel only, including (IIR) many songs on the White album. It wasn't uncommon in the early days of stereo to see the bass in one channel.

Regards,
Wayne

Wayne, good to see you. Where have you been hiding ? Let me guess....in the shack ? ;)

Regards,

Do you have any examples of recordings with stereo bass for us?Many of the early Telarc CDs and Dorian CDs had decorrelated low frequencies (stereo bass), as did the recordings that John Eargle made for the Delos label. The wider your speakers (or subs) are spread, the easier it is to hear the low frequency spaciousness.

I believe the concept is sound, for stereo sub bass whether it’s two-track of six-track Dolby stereo with split-stereo/surrounds.

I’ve done some independent frequency waterfalls of Dolby six-track mixes and there is noticeable difference on left and right fronts and split-stereo/surrounds as well.

Most portions of stereo bass/sub will be equally sent to left and right (phantom) with only a few occasions of deep low independent shudder or slam, on the left to right, what ever. Point is it worth it, how many are really going to notice the difference?



Except LEF.1 discrete track will be sent equally to left and right while some portions that have independent hard left/right from front to some surrounds as all movies from the 1970’s to early 1990’s had monaural surrounds only few that had stereo surrounds from 1978 Superman the Movie being the first one.

I’d say you’d have about 90% phantom monaural sub bass and 10% independent stereo sub bass.

But hold on!

Some signals can crossover from left front to rear right in stereo, haven’t noticed as of yet hard low end.

What about that silly film Pulse, now that scene you know which part, that has lows more or less of the same value on the primary five channels, it’s a disorienting mix.]

Chapter 15
Time 69 minutes 31 seconds to 70 minutes 58 seconds

There’s a subtle difference in the frequency waterfalls that I took from this naff film a few months ago, I can’t stand it, its pants.



http://i282.photobucket.com/albums/kk279/SpectrumsubbassLFE13417/Pulseleftsurroundchapter15.jpg






I added a single mono subwoofer to my R & L surround channels. I can hear a difference in soundtracks that do have a lot of sub 50 Hz bass placed in the surround mix.

Apollo-13 is another one of those movies that has a lot of bass in the surround channels.

HOwdy, all. Relatively new to home theater and to this forum. I think the issues are well-covered above, but I'll chime in for whatever it may be worth. The risk you run using just the left or right channel to feed your sub is that you will have unpredictable occasions of either too much or too little bass. Thinking in terms of music, when the mixing engineer fades Paul McCartney's bass to the hard left, he pushes the whole instrument that way. not just the sub-100 hz part, and not just the above-100hz part. And even for a 40 hz fundamental tone at the bottom fo a 4-string bass, a LOT of the sound and almost all the distinctive character of the instrument and player come from harmonics, many of which fall above 100 hz. The bass, like most other instruments and voices, is most often recorded in mono. Pianos, and sometimes other acoustic instruments may be recorded in stereo. Usually, the electric guitars are recorded to a single track using a single mic. Even when multiple mics are used for a guitar, or as quite commonly happens on a snare drum - - 1 mic for the batter head on top and one on the bottom to catch the snares - - the resulting feeds are usually combined into what becomes in effect a single mono signal. That is, the two snare mics are mixed together then panned to the same location, and usually if electric guitar multiple mics are actually used in the mix, they're combined to get the sound that works best, and treated as "the guitar," and panned to a single location). Some engineers and producers like 2 mics on the bass drum, too, but again they combine them to capture the bass drum as a single drum in a single location, not as a "stereo" bass drum, whith the slap of the beater in one place and the growl of the drum in another. They can put that drum anywhere on the stereo soundstatge they want, from far left to far right, but it's still, in effect, a mono bass drum recording being electrically panned to occupy a particular spot on the stereo stage.

So the mix certainly may have information below 100 hz or so that is more prominent in one channel than another. Whether at the mastering stage the low stuff has been summed mono and distributed equally between the channels is somewhat unknowable, but from what I understand it is not uncommon.

Assuming most of what we hear has the low end equally distributed between the two front channels, then when you set up your sub to run off the left only, you'll set levels to accommodate this. When the bass is fed to two channels, the left channel and right channel are each -3 decibels (I think, maybe it's -6 db) from the total bass level, so that they sum correctly when played through stereo speakers. But if a particular cd or movie has all the low end from a particular source (bass, bass drum, dinosaur) panned hard left, then your sub level actually may be too high. If it's all panned hard left, the sub "sees" the full bass signal, although it's calibrated to "see" half of it, so it will be in effect +3 db (or +6, whichever it actually is) too high. On the other hand, if say the bass is panned hard right, the sub gets zero of that low end, so you lose the reinforcement entirely. Of course there are lots of in-between possibilities, especially with music, where individual instruments may be recorded (in a "purist" recording) or panned all across the stage from far left to far right. You'll never know for sure that your bass level is consistently reflecting the recording unless you feed the sub from a summed left + right signal. I think.

Many of the early Telarc CDs and Dorian CDs had decorrelated low frequencies (stereo bass), as did the recordings that John Eargle made for the Delos label. The wider your speakers (or subs) are spread, the easier it is to hear the low frequency spaciousness.

Thanks Sanjay. Are there any specific titles worth mentioning?


"Live And Let Live," from Daniel Amos' Vox Humana album is recorded with true stereo bass. Also, Pink Floyd's Wish You Were Here disc has one track with the bass signal alternating back and forth between the L/R channels. Some early Beatles albums had the bass in one channel only, including (IIR) many songs on the White album. It wasn't uncommon in the early days of stereo to see the bass in one channel.

Thanks Wayne. My interest is in playing with stereo bass for the idea of LF spaciousness Sanjay mentions above. In the last thread regarding decorrelated bass I couldn't find any specific recordings mentioned. I'll have to check out the Daniel Amos album.

I added a single mono subwoofer to my R & L surround channels. I can hear a difference in soundtracks that do have a lot of sub 50 Hz bass placed in the surround mix.

Apollo-13 is another one of those movies that has a lot of bass in the surround channels.

The hardest part is where the LEM engine is fired for a short burn now that had some large peaks, the launch is mostly up front over LCR with a few moments of LFE.1 track slamming in.

“That was some little jolt”.:D
Jack Swigert