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Narrowing the stereo field of the low end?

I understand that narrowing the low end is often done when mastering for vinyl, but is this ever used when mastering for CD?

Is it desirable to go mono with frequencies below, say 200hz?

Thanks,
Mark

Comments

Pro Audio Guest Fri, 09/08/2006 - 10:57
The key thing to remember in this discussion is that "omni-directional" is completely different from, "hard to localize." As an example, a 100 Watt lightbulb is pretty close to omni-directional, but still very easy to locate in a room. You are right that no source is perfectly omni, and much depends on the ratio of source dimensions to wavelength. Anyway, a 12" woofer at 50 Hz is pretty darn non-directional in free-space. Doesn't mean you can't tell where it is.
- anxious

I like what anxious is sayin here. But its not just about location, its about the lowends of L and R being identical in phase. Its probably good?

JoeH Tue, 08/22/2006 - 16:34
Well, I hate to disagree with such esteemed folks opinions, but I'm fine with going to mono from around 100hz, sometimes even up to 150 if necessary, depending on the material.

We can differ on bass omni-directionality, (is that a word?) but most home systems now have subs, even cars do now; and it's anyone's guess where they get placed. I've seen some strange stuff out there, I'm sure you have too. Most stuff below 120 is going to be mono as a result, even on many high end systems. (I'll bet you can count on one hand how many folks you personally know with more than one sub in their system anyway.)

I think we'd all agree that in most cases, the sub-bass/ultra low end (20-40 hz) is being felt, not heard, regardless of where you put the box. To my way of thinking, it's all summed to mono down there anyway, and there's less chance of phasing issues or conflicting info coming at the sub from mis-matched or weirdly panned low end.

My own sub is adjustable from 80 through 120, and for my space, I've set the curve of my sub to match my mains at about 80-90hz (which is probably lower than most consumer subs). So, I get a little of both speakers info when summing this way; it's not just the sub telling me what's working or isn't.

In trying for the most transportable mixes as possible, at least to my way of thinking, a good solid low-end is a great foundation to build the rest of the mix on. Aside from a few unusual circumstances, I just think of all low end as mono, and build up from there. I'll mic tymps or double bass sections in the orchestra; and pan accordingly for L-R coherency in the mix, but I'll still sum the low end to mono. It fills up the mix, yet you KNOW where it sits onstage due to the HF cues.

For cheaper and less involved systems without a sub, anything below 80-100 hz mostly disappears anyway. This way, I'm good on the cheap stuff as well as the turbo-charged.

Pro Audio Guest Fri, 09/01/2006 - 07:24
Hey guys,
I'll try asking this question again. Please pardon me being ignorant, but how would you narrow down low frequencies using MS. I don't have Sequoia just an audio sequencer, but would like to try this. So, if I split the stereo track into M+S channels, what's the next step, if for example I'd like to narrow down frequencies under 60 hZ?
Thanks in advance

Cucco Fri, 09/01/2006 - 07:44
Effero wrote: Hey guys,
I'll try asking this question again. Please pardon me being ignorant, but how would you narrow down low frequencies using MS. I don't have Sequoia just an audio sequencer, but would like to try this. So, if I split the stereo track into M+S channels, what's the next step, if for example I'd like to narrow down frequencies under 60 hZ?
Thanks in advance

Well, just by going M/S, I don't know of any way to narrow JUST the low frequencies. I could narrow the WHOLE width by going M/S, but just the lows...tough to say.

Of course, I must point out one thing - Most large house systems use crossovers to drive seperate subs and speakers. The crossover for bass (usually set around 100-150 Hz) is sent to a mono amp. In reality, you probably don't need to lower the width of the bass stuff too much if at all.

Just a thought.

J.

Zilla Fri, 09/01/2006 - 10:16
As mentioned before, summing LF is legacy from stereo vinyl cutting (which we still do here every single day). The problem is that if there is too much uncorrelated LF energy you get to much vertical and the disc becomes unplayable. An example would be if you had a track with double kicks panned hard left and right. This might sound spectacular on tape, but you could never physically cut that to disc at an acceptable level.

The solution was/is to send the signal through what is essentially a cross-over circuit with the LF component summed to mono. We call such a unit the "LX" (low-frequency cross-over). LX should not be needed for CD/digital releases as there is no physical limitation like there is with stereo vinyl. If there is something wonky with you low end such that you feel the need to effect it somehow, its advisable to re-mix and correct it there. This avoids the already mentioned potential coloration of phase shift due to passing program through a filter.

In use, the LX is typically set under 150hz. But our unit is selectable from 30-500hz, and there has been occasion to select those higher frequencies.

Pro Audio Guest Wed, 08/23/2006 - 14:28
75hz is where FM radio puts a hipass filter, so if you mono-ize 75 and below, your stuff should have the same spatial feel over the air as it does on a full-spectrum wav file at home. At any rate, this is one of many reasons to clean up the low end. Just my two cents. I'm new to the forum, have been experimenting with this lately. Definitely looking for recording friends (my band just glazes over when i start in with the technical talk)

Cheers,
Nate

Michael Fossenkemper Wed, 08/23/2006 - 15:09
CrackBuddha wrote: 75hz is where FM radio puts a hipass filter, so if you mono-ize 75 and below, your stuff should have the same spatial feel over the air as it does on a full-spectrum wav file at home. At any rate, this is one of many reasons to clean up the low end. Just my two cents. I'm new to the forum, have been experimenting with this lately. Definitely looking for recording friends (my band just glazes over when i start in with the technical talk)

Cheers,
Nate

Nate,
welcome to the forum. lot of cool guys and gals around.

Cucco Sun, 08/20/2006 - 18:05
Yeah, I agree with Mike- 200 Hz seems a tad high (you're likely to run into issues with male vox and low guitar with that frequency).

If a mix is a tad lacking in the punch department, I will use Sequoia's built in stereo enhancer in multi-band mode to bring stuff from 90 Hz (the lowest setting possible in Seq) into the middle of the mix more. It can make a world of difference even though it's usually subtle.

J.

JoeH Sun, 08/20/2006 - 20:55
I sum below 100 or 150 hz all the time. Anything that low is generally unidirectional anyway. I use Sequoia's Stereo enhancer tool for this as well. It's great for this kind of thing, on the stereo output.

It's a nice way to focus the low end and clean up any messy rumble and "Junk in the trunk" down there. Anything above that 100 to 150 and upwards gives all the direcitonal cues you need.

Many systems are subwoofer equipped as well, so you'll get a good idea of what your stuff will sound like when using one of those, too. Maybe it's an analog leftover for me, but it's nice working from a solid foundation on upwards. The mono low-end does it for me.

Michael Fossenkemper Mon, 08/21/2006 - 05:57
100hz seems a bit high for me too. If I need to clean up the sides a little, 40-50hz does it for me. anything higher than that can really change the depth of a mix. I couldn't find anything that I liked that was on the market so I designed my own. you also have to be careful about phasing out the subs when you push them into the middle. You might be better off filtering instead of combining.

Cucco Mon, 08/21/2006 - 06:59
I think the trick is not to make it entirely mono. If that were the case, then 100 is too high. Usually, I bring it between 60 and 80% of original width.

Personally, I don't subscribe to the assumption that bass is entirely omnidirectional. I do believe it's harder to localize, but not impossible. For the longest time, I couldn't figure out why my system sounded off, but something was clearly wrong. My sub was located in the corner behind my left speaker.

I decided to move it inside next to my right speaker and voila - the system sounded MUCH better.

Since I listen primarily to classical and in about 95% of the orchestras in the world, the basses are on the right (audience perspective), the low frequency needed to come from that direction. Bear in mind, my sub is crossed over at 32 Hz, so there wasn't a lot of information there, but enough to throw me off.

Sorry - tangent over.

Pro Audio Guest Tue, 08/29/2006 - 23:18
The key thing to remember in this discussion is that "omni-directional" is completely different from, "hard to localize." As an example, a 100 Watt lightbulb is pretty close to omni-directional, but still very easy to locate in a room. You are right that no source is perfectly omni, and much depends on the ratio of source dimensions to wavelength. Anyway, a 12" woofer at 50 Hz is pretty darn non-directional in free-space. Doesn't mean you can't tell where it is.

The audibility of "stereo" bass has been demonstrated many times in research environments, down to frequencies below 40 Hz. Even when the listener can't specifically localize the sources, there is recognizable spatial impression from the so-called, "inter-aural lateral energy."

[PS- I think that bass weapon stuff is purely urban legend. It makes for fun speculation, but the math just doesn't pan out. Someone once sent me a hysterical, pseudo-historical web page about a Nazi sound weapon that accidentally destroyed itself. Can't find the link anymore...]

Cucco Wed, 08/30/2006 - 07:09
anxious wrote:

[PS- I think that bass weapon stuff is purely urban legend. It makes for fun speculation, but the math just doesn't pan out. Someone once sent me a hysterical, pseudo-historical web page about a Nazi sound weapon that accidentally destroyed itself. Can't find the link anymore...]

Nope...
The funny thing is - the fact that it exists is easy to gleen from the government thanks to the Freedom of Information Act (FOIA). However, they certainly won't go into details - FOIA only applies to non-classified or non-sensitive data. The fact that they exist is neither.

The majority of the sonic weapons they use are ultrasonic in nature, not infrasonic, however, there are purposes for infrasonics. Unfortunately, I do have first hand knowledge on this as I'm one of the lead scientists for a Defense contractor working on advanced weapons systems projects in the Pentagon and out of NJ. One thing I *can* say is that they do in fact exist.

J 8-)

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