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Gear / Technical Help => Ask The Tapers => Topic started by: Roving Sign on March 04, 2006, 09:14:29 AM
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Would there be any feasibility/advantage to this appoach?
i.e. - use some sort of crossover to divide the signal into L/R bass and L/R treble channels...and record them independenly. Then control the blend in post.
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I've wondered about doing something like this and just found your post after a search. On a practical level, if you're recording four tracks and planning on doing post work anyway, why not record four full range signals and make any decisions about crossover points & slopes and levels later, when you can listen critically?
I'm curious about this from more of a theoretical standpoint. Here's my thinking in bullet points:
- I mostly record with spaced omnis (or baffled or HRTF, but forget those for now) and really love the depth, ambiance, openness, low end, etc.. all that typical omni stuff. If the situation allows for a decent spaced omni recording, I usually prefer those qualities the over the sharper imaging of a directional config, if forced to make a choice.
- Of course I want it all, sharp imaging too.
- It's not unusual for classical recording engineers to run flanking omnis with a center pair (coincident or near-coincident) and then mix those feeds to stereo to add some of the rich open ambiance of the omnis to the tighter primary center pair.
- I've had some good results mixing some of my spaced omni recordings with someone else's ORTF recording to combine the better aspects of both. This provided a clearer and more present and 'upfront' vocal and mid range, while still retaining the openness and ambiance of the omnis. I primarily used this to adjust the frequency balance and reverb ratio more than the imaging aspects. I also noticed some less obvious effects on the soundstaging.
- I have somewhat of a grasp on the physiological basis of human hearing and how various mic techniques exploit the manner in which we hear. To make a gross generalization an quick summary:
- We determine direction using three phenomena: time (phase) difference between ears, intensity (sound level) difference between ears and differences in spectrum of sound at each ear correspond to direction (determined by the shape of our head an ear pina). Forget about the last one for this discussion and just consider time & intensity.
- We use time (phase) differences to determine direction at lower frequencies. Time differences are captured using spaced mic techniques.
- We use intensity (level) differences to determine direction at higher frequencies. Level differences are captured using directional mic techniques.
- What about using the time based spaced technique to record the low frequencies (spaced omnis), and the level based technique for the high frequencies (coincident directional mics)? The different frequency ranges could be split with a crossover function before mixing. Obvious configurations would be a center pair with flanking omnis, or a Decca tree with a coincident pair in place of the center omni. These mic configs are not uncommon, but I've never heard of doing the crossover technique with them.
- In addition to exploiting the psychoacoustic principles above, the crossover technique may also eliminate potential comb filtering problems when summing the multiple mic feeds, at least outside of the crossover region.
Obviously the thing to do is try this frequency range based mixing technique with the spaced omni and ORTF mix that I got good results with when I mixed the four full frequency feeds. I need to get deeper into my editing software to try that and find some time to make it happen. Just throwing the idea against the wall here to see what sticks. I'm interested to hear your thoughts. Someone must have tried this before, but I haven't found much in my searches.
Lee
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Would there be any feasibility/advantage to this appoach?
i.e. - use some sort of crossover to divide the signal into L/R bass and L/R treble channels...and record them independenly. Then control the blend in post.
That has been done in the studio actually. Its the basis for a Meyer sound eq that was developed. But they did not have separate outputs they did however use a crossover to divide the signal and then recombine it so you could control the spectral output of each frequency band and then use it as a "balance control" over a selected bandwidth. Its a very good idea.. And it can be done the only problem is your recording will only be as good as the crossover or frequency division network you use. Good electronic crossovers are very expensive around $2000+ the cheapest one you can get would be made by DBX the minidriverack. But again anything less then $450 to $2000 and your really going to bastardize the signal and make it much worse then it already was. A good crossover will allow you to change the phase and time alignment of each frequency band, as well as the ability to use parametric eq in each band all with in one processor. This is a pretty cool idea. But one that requires deep pockets to pull off correctly.
This is a link to the VX-1 Meyer Sound processor I was talking about.. http://www.meyersound.com/products/processor_drive_systems/vx-1/
This is a link to DBX drive rack ( cheap but ok crossover ) http://cgi.ebay.ca/NEW-DBX-DRIVERACK-PA-DJ-DSP-CROSSOVER-COMPRESSOR_W0QQitemZ250103292073QQihZ015QQcategoryZ4785QQrdZ1QQssPageNameZWD1VQQcmdZViewItem#ebayphotohosting
Chris
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Interesting info on the Meyer EQ unit. Chris.
Roving Sign proposed using a (hardware) crossover to divide the spectrum before recording it. I'm proposing doing that in post in a DAW where you could also tweak phase/time alignment, eq, etc. if needed like in the big dollar prosound units you describe. No guarantee that you won't bastardize the signal and make it worse than it was of course, but the option is there without committing to it in advance.
I'm somewhat familiar with the electronic crossovers and speaker management systems you mention: the stuff on the sound reinforcement side like the DBX driverack, BSS, Ashly, Rane, big dollar Meyer stuff etc.. the audiophileish tubed Marchand, DEQX, Tact.. I'm sure there are others aimed at studio monitors and mastering houses.. and the cheap Behringer DCX2496 unit that lots of DIY speaker builders use to tweak crossover designs or run multiway active speakers with separate amplification for each driver with phase, time alignment, eq's, high order asymmetric x-over slopes, etc. I almost bought one to play with active multi-amping some old infinity speakers I've got. I'm sure you get what you pay for and Moore's law marches steadily on..
All that's the practical side. Thoughts on the theory, assuming you've got the right tools to do the job?
Here's the important question buried in my post above:
- What about using the time based spaced technique to record the low frequencies (spaced omnis), and the level based technique for the high frequencies (coincident directional mics)?..
-[edited for bad typin']
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Interesting info on the Meyer EQ unit. Chris.
Roving Sign proposed using a (hardware) crossover to divide the spectrum before recording it. I'm proposing doing that in post in a DAW where you could also tweak phase/time alignment, eq, etc. if needed like in the big dollar prosound units you describe. No guarantee that you won't bastardize the signal and make it worse than it was of course, but the option is there without committing to it in advance.
I'm somewhat familiar with the electronic crossovers and speaker management systems you mention: the stuff on the sound reinforcement side like the DBX driverack, BSS, Ashly, Rane, big dollar Meyer stuff etc.. the audiophileish tubed Marchand, DEQX, Tact.. I'm sure there are others aimed at studio monitors and mastering houses.. and the cheap Behringer DCX2496 unit that lots of DIY speaker builders use to tweak crossover designs or run multiway active speakers with separate amplification for each driver with phase, time alignment, eq's, high order asymmetric x-over slopes, etc. I almost bought one to play with active multi-amping some old infinity speakers I've got. I'm sure you get what you pay for and Moore's law marches steadily on..
All that's the practical side. Thoughts on the theory, assuming you've got the right tools to do the job?
Here's the important question buried in my post above:
- What about using the time based spaced technique to record the low frequencies (spaced omnis), and the level based technique for the high frequencies (coincident directional mics)?..
-[edited for bad typin']
When you start playing around with sound at that level there are no theories just good results and bad results. :) Not to many people have done it, its very time consuming and in the end its only as good as your source.. So I dont know... :) I think that it could be interesting properly applied it could be very interesting, there are other things that can be done as well like using a different reverb for the highs and lows and mid range to "recreate" spaces by separating the bands you can in fact simulate more closely the real world acoustic reverberation that takes place in a real concert hall. Lexicon first introduced the crossover algorithm to there Lexicon 224 reverb with Larc back in the Late 70's The still use this crossover algorithm today in there processors. So there are lots of things that can be done its really just a limit on your imagination and the willingness to try different approaches to audio. That is why I love audio. There are many different ways to accomplish good sound.
Chris
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When you start playing around with sound at that level there are no theories just good results and bad results. :)
Sounds like Duke Ellington's philosophy: There are only two kinds of music, 'good' and 'bad'. ;D