Topic: Matrix recording steps and FAQ (744T series, and others like it)

[robotaper]

Great information everyone.  Thanks for the direction and assistance.  I'll keep you posted on my progress.  Making my first attempt this Saturday night.   

[Todd R]

drift = don't need to worry about
delay = you do need to worry about.

I agree with the overall discussion, and agree practically speaking with baustin.  To be totally correct though, drift can be a function of the internal clocking differences of the sbd and aud sources.  This wouldn't be an issue when using a 4ch recorder with a single clock.

Drift can also occur due to changes in the speed of sound (so the time differences between the sbd source which is not dependent on the SOS and the aud source which is dependent on the SOS changes as the SOS changes).  The speed of sound (SOS) depends on both temperature and humidity.  If you go into a club with relatively low humidity and a temp of 68, and then it gets filled with hot, sweaty, dancing people and rises to 85 degrees with high humidity, the speed of sound (and hence the delay between mics and board) will change from when you start recording to when you finish.  Over a 3 hour show, depending on the changes of temp and humidity, I think this can cause a drift of ~5ms.  A 5ms drift isn't really enough to worry about when matrixing the recording, but there still could be some small amount of drift even with a 4ch recorder.

[goodcooker]

Like Joe said aligning the two sources is not an exact science.

To get in the ballpark I make a note of how far from the source my room mics are in feet. I add that many ms to the beginning of the SBD feed then do the final adjustment by ear, not by sight. I listen for comb filtering in the bass and phasing in the snare drum. You can hear the bass "tighten up" all of a sudden when you hit the spot where they align.

I also use Wavelab Montage

[robotaper]

Following the discussion here I have pulled my first Matrix tape and am in the post production process.  I made the mistake of recording the show as a .wav mono, however I have the SD Wave Agent program which can split the files.

The setup I used was pretty straight forward as the mics were basically on the stage so I have no need for matching/alligning the sources due to "delay" as it's been discussed here.  Coupled with the SBD source (12' Dark Train cable to the 744) I ran my AK40's on the stage lip at about 3' high (using the LC3KA cable to run back to the bodies, and then a Dark Train interconnect to the 744).

Once transfered from the 744 to my PC, I loaded the raw files into Audacity (my first time using this program).  Overall I found it to be very easy to use, although it seemed limited in what can be accomplished.  I tested various levels for each channel until I achieved what I believed to be an optimum sound (based upon my own judgement by ear), and exported the file to a 2 track stereo file.  In my estimation I achieved a 55% SBD / 45% MIC split in the mix.

I am very pleased with the sound of my first matrix recording.  I still have tracking, dithering, etc. to complete for this project.  Once completed I will post some samples.  Thanks for your suggestions.

Rob

[phishy12]

drift = don't need to worry about
delay = you do need to worry about.

I agree with the overall discussion, and agree practically speaking with baustin.  To be totally correct though, drift can be a function of the internal clocking differences of the sbd and aud sources.  This wouldn't be an issue when using a 4ch recorder with a single clock.

Drift can also occur due to changes in the speed of sound (so the time differences between the sbd source which is not dependent on the SOS and the aud source which is dependent on the SOS changes as the SOS changes).  The speed of sound (SOS) depends on both temperature and humidity.  If you go into a club with relatively low humidity and a temp of 68, and then it gets filled with hot, sweaty, dancing people and rises to 85 degrees with high humidity, the speed of sound (and hence the delay between mics and board) will change from when you start recording to when you finish.  Over a 3 hour show, depending on the changes of temp and humidity, I think this can cause a drift of ~5ms.  A 5ms drift isn't really enough to worry about when matrixing the recording, but there still could be some small amount of drift even with a 4ch recorder.

very interesting point about the temp and humidity affecting drift. i've often wondered why my second set would sometimes need a few more ms delay for it to align properly. thanks for the info todd!!! +t

[Gutbucket]

Drift can also occur due to changes in the speed of sound (so the time differences between the sbd source which is not dependent on the SOS and the aud source which is dependent on the SOS changes as the SOS changes).  The speed of sound (SOS) depends on both temperature and humidity.  If you go into a club with relatively low humidity and a temp of 68, and then it gets filled with hot, sweaty, dancing people and rises to 85 degrees with high humidity, the speed of sound (and hence the delay between mics and board) will change from when you start recording to when you finish.  Over a 3 hour show, depending on the changes of temp and humidity, I think this can cause a drift of ~5ms.  A 5ms drift isn't really enough to worry about when matrixing the recording, but there still could be some small amount of drift even with a 4ch recorder.

very interesting point about the temp and humidity affecting drift. i've often wondered why my second set would sometimes need a few more ms delay for it to align properly. thanks for the info todd!!! +t

+1

[goodcooker]

the mics were basically on the stage so I have no need for matching/alligning the sources due to "delay" as it's been discussed here

running mics on the stage doesn't always guarantee that the stereo mixdown will be just right....I've had to add as much as 8ms to a matrix where I ran the mics on the stage lip.

Adding that +/- 8 feet to the SBD source pretty much "moved" my mics to the lip of the kick drum (into closer proximity with the drum overheads and bass amp) which caused less phasing in those two sources and shifted the comb filtering into the guitars and heavily processed vox where it did far less damage (and actually did some good since the "woofer in a cardboard box" monitors where about three feet from my mics and the inherent but minor comb filtering cut out some of the unpleasantness)

Sorry that was a heck of a run on sentence !