Topic: Synching 2 + 2

[stevetoney]

Is it really that big of a deal if you have two separate recording decks just to run separate rigs and synch the two recordings afterwards?  I've never had any trouble with stretching or shrinking one recording to synch/match another.  The reason I ask this is that it seems like a reasonable money saving option to buy...say...a second M10 as opposed to selling and putting $800 or $1000 into a DR680 or R-44.  I'm not considering doing this, only curious about peoples responses because it seems like it's never mentioned.   

[Patrick]

Obtaining perfect sync between two separate word clocks is virtually impossible.  Even if you can line up waveforms, there is still drift between the two sources that can result in some pretty terrible things like smearing the stereo image, phase cancellation, and at worse a slapback delay sound.  Even if it is easy to run two separate recording decks in different locations, I don't have time to do the tedious post work and therefore always try to get all my channels run to a centralized point in the venue.  Sometimes the effort is worth it, but most of the time it simply isn't. 

[macdaddy]

one machine is preferable to two when in the field, imo. plus since i dont carry both p2s with me at all times, i miss the last minute matrix option (when asked on the spot if i want a sbd signal). i am looking at the two machines in the original post so that all i would need to do is carry an extra set of cables and the pair of attenuators and i would have the ability to add a sbd source at any time. thetime saved by not having to sync tracks by hand is a nice side benefit (but i get that by sync'g two p2s). finally, further down the line, the only mic i see myself buying is the soundfield, and the four channel recorder would be needed for that. but in reality, i am simply considering thw move to a 4ch recorder because it is one machine instead of two in the bag, and i will always be ready when given the permission to record a sbd feed...

[acidjack]

A lot of guys say it's no big deal but I personally have had a hell of a time doing it.  The last time I had to do it I had to ask another member here for his help.  When he did it, it worked well.

You can of course link two decks perfectly using a USBPre2, but that may not really save you much.  If you just wanted 4 channels, obviously an R-44 is cheaper. 

If I already had a 2-channel rig that included a USBPre2, it would be an economical and easy option to just buy the least expensive second deck with digi in that you could get (which I think would now be the DR-100mkII, IIRC).

[adrianf74]

If I have the choice, I'll use my friend's DR-680 to handle the multiple sources.  This will make synching the recording extremely easy once I've lined up beats and checked them at varying points throughout the recording.

However, there have been times where I've had to use an M10 or two M10's and the DR-680 to record a show.  I've then had to reclock one source against another.  If it's done with extreme care (and precise measurements) you can get the files to match within hundredths of a second in a 2-and-a-half hour show.   Most recently, I had a show where I had a soundboard feed, AKG 480's (hypers0 and DPA 4061's (omnis) and was able to matrix the entire 140 minute show without incident.  The AKGs and SBD were run to the 680 and the 4061's were run to the M10.  I hadn't yet received my PFA's from Jon so I couldn't use them for this show.  I listened to this both with headphones and over speakers and the quality is just superb. 

Likewise, I posted my the New Deal recording from Toronto which is a matrix of my 4061's and my friends 480's.  Again, didn't have the PFA on-hand until just after the show otherwise my life would've been made easier, however, since I had the sample length for the other shows I'd already run, the sample lengths on the 4061/M10 were ahead by less than a second over 2 hours.   Fixed and now up on LMA. 

If I had my way, I'd run a deck that has the ability to run two sources simulatenously but since I don't do this often enough, I can't justify dropping a grand on a R-44.  My friend has had NO issues with the 680 but I know many people in these parts have so I would tend to shy away from that option.

[acidjack]

Adrian also makes a great point - how often do you plan to run 4-channel, Steve? 

I run 4-channel at almost every single show, and I'm mixing down several shows a week.  The extra time of syncing two clocks in post would kill me - I don't have the time to mix down what I have as it is.  But if I was only doing it, say, once per month, I tend to agree that it's harder to justify spending big bucks on a multi-channel deck. 

[stevetoney]

Adrian also makes a great point - how often do you plan to run 4-channel, Steve? 

I was doing 4 channel into an R4 Pro for awhile but my recordings would sound better than the 2 channel versions in only a handful of situations, so I stopped. 

I asked the question more out of curiosity since it seems like people consider it sorta taboo, but since digital recorders exhibit no wow and flutter, I've never had much trouble synching two sources spot on perfect with the software I use and it usually doesn't take much more than 10 to 15 minutes to get them lined up and get one of the files changed if I'm using a fast computer. 

I do agree though that if you do 4 channel often it wouldn't make sense to not have a 4 channel recorder.

[adrianf74]

That's the thing.  It's a matter of "how often" are you gonna be doing it?  If I was doing multiple shows per week like AcidJack, I'd be running a 680 or 44 pronto.  If it's the odd show that you want to matrix because both mics sounded like crap on their own (but complement each other well) or you had board access and wanted to spruce it up, then I'd run the two recorders and "fix it in post." 

I've done quite a few matrix recordings in the past year (about 15 of them) but I still wouldn't spend the extra cash for that few shows.   Now that I have the PFA, I have to figure out how I'm gonna use inputs 5+6 on the 680 and if I'm gonna have to attenuate the board feed from XLR > RCA in order to best utilise my inputs - but that's another story/thread.

[page]

Obtaining perfect sync between two separate word clocks is virtually impossible.  Even if you can line up waveforms, there is still drift between the two sources that can result in some pretty terrible things like smearing the stereo image, phase cancellation, and at worse a slapback delay sound. 

Completely agree, even when you get really good at reclocking stuff, there can be minor amounts of non-linear drift during a set (depending on individual units, not brands or models). I've done 2+ hour sets and heard instruments and soundstage move around slightly due to cancelation/emphasis that I don't hear on either of the sources and it gradually occurs over a period of time (e.g. not a mix adjustment in the room). It's not bad, I only notice it if I'm really doing analytical listening on a few really good setups, and all of my sync points line up visually down to the sample, but I've never been able to eliminate that teeny tiny bit of change when it shows up. My 4ch clocked stuff doesn't have this issue.

If I already had a 2-channel rig that included a USBPre2, it would be an economical and easy option to just buy the least expensive second deck with digi in that you could get (which I think would now be the DR-100mkII, IIRC).

bingo, that's what I did. I have a 722 which is my workhorse recorder, and bought a usbpre2 as a dac/amp, but it also doubles as a second preamp/adc that can clock against the 722 if needed. So since I sold my old dac/amp and used that cash to buy the pre2, I was out the cost of a D50 for what essentially is a slightly bigger footprint and 4 clock-able channels (or 2+2 if I want to run on separate stages simultaneously). So while the pre2 isn't a perfect box, it's damned close in that aspect.

I only record 4ch about 3 times a year, so there was no good reason for me to blow cash on it, but this option allowed me to pick up gear I like the sound of and do it on the relative cheap.

[hi and lo]

The clock drift between recorders might not be consistent over time. Trying to use different decks really isn't an option and you'll waste countless hours trying to get it to work , if it works at all.

[runonce]

Arent there certain gear combos that allow you to sync the second deck's A/D to the firsts clock....?
HD-P2?

[stevetoney]

The clock drift between recorders might not be consistent over time. Trying to use different decks really isn't an option and you'll waste countless hours trying to get it to work , if it works at all.

That really hasn't been my experience the time's I've synched two different sources that were sourced from digital recorders.  The drift between the two is linear so it's straight forward to address and the synch is consistent throughout the recording after correcting one or the other, but yeah I definitely agree that if one of the two clocks isn't linear or if one of the recorders drops bits here and there then it wouldn't be very easy to synch the two sources together.

[justink]

The clock drift between recorders might not be consistent over time. Trying to use different decks really isn't an option and you'll waste countless hours trying to get it to work , if it works at all.

That really hasn't been my experience the time's I've synched two different sources that were sourced from digital recorders.  The drift between the two is linear so it's straight forward to address and the synch is consistent throughout the recording after correcting one or the other, but yeah I definitely agree that if one of the two clocks isn't linear or if one of the recorders drops bits here and there then it wouldn't be very easy to synch the two sources together.

the drift between my R-44 and another recorder was consistent three straight nights actually.

[stevetoney]

Arent there certain gear combos that allow you to sync the second deck's A/D to the firsts clock....?
HD-P2?

Yeah, for sure.  HD-P2 can link to other HD-P2's and the 2 channel Sound Devices can also.  I'm sure there are others.

[acidjack]

Adrian also makes a great point - how often do you plan to run 4-channel, Steve? 

I was doing 4 channel into an R4 Pro for awhile but my recordings would sound better than the 2 channel versions in only a handful of situations, so I stopped. 

I asked the question more out of curiosity since it seems like people consider it sorta taboo, but since digital recorders exhibit no wow and flutter, I've never had much trouble synching two sources spot on perfect with the software I use and it usually doesn't take much more than 10 to 15 minutes to get them lined up and get one of the files changed if I'm using a fast computer. 

I do agree though that if you do 4 channel often it wouldn't make sense to not have a 4 channel recorder.

FWIW, also, when I say "four channel" I generally mean SBD+mics.  Four mics (or six mics) can be interesting, especially if the mics are placed in different locations (i.e., one pair onstage, one pair FOB), but I tend to agree with you that for just throwing up some mics somewhere in a room, I'm not sure running four mics together is always that beneficial, esp for how much of a PITA it is.

[page]

Adrian also makes a great point - how often do you plan to run 4-channel, Steve? 

I was doing 4 channel into an R4 Pro for awhile but my recordings would sound better than the 2 channel versions in only a handful of situations, so I stopped. 

I asked the question more out of curiosity since it seems like people consider it sorta taboo, but since digital recorders exhibit no wow and flutter, I've never had much trouble synching two sources spot on perfect with the software I use and it usually doesn't take much more than 10 to 15 minutes to get them lined up and get one of the files changed if I'm using a fast computer. 

I do agree though that if you do 4 channel often it wouldn't make sense to not have a 4 channel recorder.

FWIW, also, when I say "four channel" I generally mean SBD+mics.  Four mics (or six mics) can be interesting, especially if the mics are placed in different locations (i.e., one pair onstage, one pair FOB), but I tend to agree with you that for just throwing up some mics somewhere in a room, I'm not sure running four mics together is always that beneficial, esp for how much of a PITA it is.

QFmfT

To me, the combfilter and smear in the soundstage produced by phase cancelation when using 2 semi-coincident pair of mics just isn't worth the little gains in pattern adjustment. Put the mics in really different places and it gets some redeaming value. Use a sbd and a set of mics and it has value, but 2 sets of mics in the same spot is just more work for just about no net benefit. The occasions when I've seen 2 pair of mics (that are in close proximity) compliment each other enough to outweigh the sonic downsides created by mixing when compared to picking just one of the sources and tweaking it can be counted on one hand with fingers left over. ymmv.

[stevetoney]

Adrian also makes a great point - how often do you plan to run 4-channel, Steve? 

I was doing 4 channel into an R4 Pro for awhile but my recordings would sound better than the 2 channel versions in only a handful of situations, so I stopped. 

I asked the question more out of curiosity since it seems like people consider it sorta taboo, but since digital recorders exhibit no wow and flutter, I've never had much trouble synching two sources spot on perfect with the software I use and it usually doesn't take much more than 10 to 15 minutes to get them lined up and get one of the files changed if I'm using a fast computer. 

I do agree though that if you do 4 channel often it wouldn't make sense to not have a 4 channel recorder.

FWIW, also, when I say "four channel" I generally mean SBD+mics.  Four mics (or six mics) can be interesting, especially if the mics are placed in different locations (i.e., one pair onstage, one pair FOB), but I tend to agree with you that for just throwing up some mics somewhere in a room, I'm not sure running four mics together is always that beneficial, esp for how much of a PITA it is.

QFmfT

To me, the combfilter and smear in the soundstage produced by phase cancelation when using 2 semi-coincident pair of mics just isn't worth the little gains in pattern adjustment. Put the mics in really different places and it gets some redeaming value. Use a sbd and a set of mics and it has value, but 2 sets of mics in the same spot is just more work for just about no net benefit. The occasions when I've seen 2 pair of mics (that are in close proximity) compliment each other enough to outweigh the sonic downsides created by mixing when compared to picking just one of the sources and tweaking it can be counted on one hand with fingers left over. ymmv.

That was my experience too, but it was super fun trying and experimenting with four mics.  Actually, I just made my conclusions based on my recordings not sounding any better, but now that you put in words what I was probably hearing on my recordings, it was probably the smear factor that drove me to those conclusions. 

[Patrick]

Many of the 4 mic setups I run usually result in tossing 2 of the channels and using whichever sounds better.  I have heard many good sounding 4 mic mixes but for most PA systems, it's just another opportunity for phase cancellation.  I almost always try to run omni's NOS or equivalent as one pair of mics and use a near coincident pair for the other 2 channels.  Stacking 2 pairs of cardioids on top of each other is kinda silly (even though I've done this before, too!)

[hoppedup]

I mix 4 channels from two recorders quite a bit. It works for me.

I've done six channels from three recorders once and it worked fine, IMO. http://www.archive.org/details/bdl2011-07-03.mtx.flac16

The only time I've done a matrix of two mic sources in the same location, I think it turned out great: http://www.archive.org/details/acousticmanner2011-07-16.mtx.flac16

Granted, I don't have the critical listening skills some of you guys have. Don't really need 'em if it sounds good to me, though. I always listen to each source independently and in different mixes before I decide what to post. I don't mix in other sources unless it sounds better (IMO) that way.

[hi and lo]

Many of the 4 mic setups I run usually result in tossing 2 of the channels and using whichever sounds better.  I have heard many good sounding 4 mic mixes but for most PA systems, it's just another opportunity for phase cancellation.  I almost always try to run omni's NOS or equivalent as one pair of mics and use a near coincident pair for the other 2 channels.  Stacking 2 pairs of cardioids on top of each other is kinda silly (even though I've done this before, too!)

Some damn good advice here! I will often run a 6-channel rig (SBD + 4 Mics) and rarely do I end up using all four microphone channels. I have run spaced omni's + a coincident pair which works out great, but more often than not I am running 2 x coincident pairs and end up tossing one or the other. It allows me to experiment with microphone configs and feeds my masochistic tendency to haul more gear than needed to a show, but is generally not useful for the resulting mixdown.

With that said, I have mixed two coincident pairs before and while you do have to be careful about phase cancellation and comb effect, it's not impossible and is infinitely easier than the topic of the OP (clock syncing the recording from two decks in post). Most of the times I've done this is because the NYCtaper crew hit up a show as a team effort, with more mics being run that we possibly need, and it's nice to include everyone in the final product. It's usually hypers + cards, not cards + cards, and if done with some care and effort is certainly not detriment to the end-result.

[Todd R]

To me, the combfilter and smear in the soundstage produced by phase cancelation when using 2 semi-coincident pair of mics just isn't worth the little gains in pattern adjustment. Put the mics in really different places and it gets some redeaming value.

To Steve's original question, I've synched different sources a number of times, and really don't prefer doing it anymore -- just too much effort.  That said, the 4ch (or 4+) mixes I've done in the past several (many?) years have been done either with a mixer or mixed in post from a 4ch/8ch recorder.  I haven't synched sources since back in the DAT day, and the different tape speeds, warble, different clocks, etc, just made synching a nightmare.

Lately, I never seem to do 2ch aud (or better yet 2ch on-stage) + SBD mixes.  My 4ch mixes when I do them are 4mic mixes.  I agree with Page that 4mic mixes of 2 (semi)coincident pairs don't generally do much for me.  I'm usually mixing a center semi-coincident card pair with a pair of split omnis. 

What are people's thoughts on this?  Sometimes I like it, sometimes not.  When I do, it is the spaciousness of the split omnis together with the grounding of the center pair to get rid of the hole-in-the-middle effect.  That said, I don't know that I've noticed soundstage smear or phase cancellation.

BTW, to Steve's point:  I now record my mics>V3(digital)>D50 as my main source, and then have added in a Tascam DR2d for an analog feed from the V3, plus an analog feed of omnis>littlebox.  Since I already had all the other gear, the extra for the 4ch recorder is just the cost of the DR2d.  I got mine for $185, but I think they are now like $130.  For $130 extra, it hardly is worth fiddling with synching sources.

[page]

It allows me to experiment with microphone configs and feeds my masochistic tendency to haul more gear than needed to a show, but is generally not useful for the resulting mixdown.

I stand behind this. Learning how to analyse a given situation on the fly is very important for what we do, and having that experimentation allows for a more controlled experiment. The one time I've debated running 4 mics was to compare the tightness of patterns, not mixing them together. I ultimately decided not to because I already had an idea of how that would turn out (and lugging the extra gear thus wasn't worth it to me), but others who have multiple mic families at their disposal would see a greater benefit. There comes a point where one should reasonably know what to do and thus the benefit of the extra gear is deminished even further, but the educational process to get there is still very valid.

Granted, I don't have the critical listening skills some of you guys have. Don't really need 'em if it sounds good to me, though.

I also stand behind this. I can't stand clipping at the original point of A>D because there was a period of time when I had gear that did not behave well when playing back clipped recordings, even tiny bits. Now I have gear that behaves a little better with it, but I'm sensitive to that now due to that experience. Same thing with soundstage, once I changed my playback gear to gear that was able to produce a very detailed soundstage, I noticed what that did to a recording and having the smear from mixing became a disadvantage. If I couldn't hear it, it wouldn't bother me. This is the same vein as the "maybe it's your playback" thread.

Ultimately, many (I dare say most) of us tape for ourselves first and foremost. If it sounds good to us, then that's a large chunk of the battle. It's nice if it sounds good for others, but at the end of the day, you've gotta be happy with it first. I may value soundstage above a couple of other things, you may value some other things above soundstage, and that's ok.

I'm usually mixing a center semi-coincident card pair with a pair of split omnis. 

What are people's thoughts on this?  Sometimes I like it, sometimes not.  When I do, it is the spaciousness of the split omnis together with the grounding of the center pair to get rid of the hole-in-the-middle effect.  That said, I don't know that I've noticed soundstage smear or phase cancellation.

To recycle some of my response to Dale, if it sounds good to you, I wouldn't worry too much about it then. I've had a value shift over the last year or so to where smear is generally something I like to avoid (and I now understand why freelunch hates the sonosax and it's smear). There are occasions that it works well, but I find they are far and few anymore. On a side note, I think it works well when you're soundstage is already bad and smear improves either the euphoric quality or intellegibility of the primarily intended sound.

If I was going to do wide omnis and a center fill, I'd do just a single forward hypercard (or possibly figure8 ) channel for the fill in a decca tree arrangement and have the perpendicular angle of the tree's center/flanker capsules be on axis with the stacks in an attempt to minimize the phase cancelation within each channel. I've thought about doing that at a festival, but didn't want to mess with the setup and borrowing gear to accomplish it.

edit: stupid smiley in the last paragraph, fixed now.

[Todd R]

Thanks for your thoughts Page.  I agree the way to do it is with a single center channel.  I usually think of my DIN cards as my main recording rig -- the 4ch stuff is just for playing around.  I haven't been willing to sacrifice my DIN cards for that experiment.

I've considered running cards A-B as my main 2ch rig sometime and then just using the center one of those cards for the center channel of a 3mic mix.  That might fly.

[hi and lo]

We're hijacking a bit here, but I'm definitely going to start experimenting with a stereo pair + center channel config. I had put in an order for a Grace Spacebar overbridge attachment to do this very thing, but Jerry at posthorn couldn't find it in his office! Guess I need to just order one from Grace directly.

[hi and lo]

The clock drift between recorders might not be consistent over time. Trying to use different decks really isn't an option and you'll waste countless hours trying to get it to work , if it works at all.

That really hasn't been my experience the time's I've synched two different sources that were sourced from digital recorders.  The drift between the two is linear so it's straight forward to address and the synch is consistent throughout the recording after correcting one or the other, but yeah I definitely agree that if one of the two clocks isn't linear or if one of the recorders drops bits here and there then it wouldn't be very easy to synch the two sources together.

YMMV... I've had several recordings aligned perfectly at the beginning and end, only to discover that the middle portions are 20-100 ms apart.

[page]

The clock drift between recorders might not be consistent over time. Trying to use different decks really isn't an option and you'll waste countless hours trying to get it to work , if it works at all.

That really hasn't been my experience the time's I've synched two different sources that were sourced from digital recorders.  The drift between the two is linear so it's straight forward to address and the synch is consistent throughout the recording after correcting one or the other, but yeah I definitely agree that if one of the two clocks isn't linear or if one of the recorders drops bits here and there then it wouldn't be very easy to synch the two sources together.

YMMV... I've had several recordings aligned perfectly at the beginning and end, only to discover that the middle portions are 20-100 ms apart.

and then have them come back to alignment (or better aligned if not perfect) later on in the show. The first time that happened I spent days messing with it trying to figure out where I went wrong. Now I just grouse about it on TS... 

I think the worst part is that you can take 2 units and they won't drift the same exact amount consistantly each time. Most of the time it's "good enough", but sometimes it's noticable.

[acidjack]

Thanks for your thoughts Page.  I agree the way to do it is with a single center channel.  I usually think of my DIN cards as my main recording rig -- the 4ch stuff is just for playing around.  I haven't been willing to sacrifice my DIN cards for that experiment.

I've considered running cards A-B as my main 2ch rig sometime and then just using the center one of those cards for the center channel of a 3mic mix.  That might fly.

To add a bit more on the 4mic thing, Dan Lynch does a 4-mic setup that is effectively pretty similar to center channel - running 150s in a very tight pattern + ORTF DPAs.  While I stand behind my previous comments on my experience with 4-mic setups, I listen to enough of his recordings that I have come to conclude that his method results in better recordings than either of those two particular sets of mics separately.  The Neumanns have a very particular, rolled-off sound, but they have a ton of "sparkle" at the high end and their rolloff offers a sense of directivity to the vocals and the sound generally.  Running them the way he does with the wide DPAs, which provide a big, wide soundstage but will never be associated with terms like "sparkle", it allows him to create a mix that is better suited to the particular sound and environment he is in.  I personally have never noticed big issues with phase etc. with his recordings, partly because the Neumanns are virtually a center channel.

I would not recommend this method as a "general rule" by any means, but with that particular combo of mics and the number of times he runs it, I personally like the results a great deal.

[bdasilva]

I had a show that was 1/2 second off in a 100 minute show....  I went along and remover 2ms at every minute of the longer recording... a pain in the ass??? yes!! did it work? Like a champ

[ellaguru]

snip..
   "Lately, I never seem to do 2ch aud (or better yet 2ch on-stage) + SBD mixes.  My 4ch mixes when I do them are 4mic mixes.  I agree with Page that 4mic mixes of 2 (semi)coincident pairs don't generally do much for me.  I'm usually mixing a center semi-coincident card pair with a pair of split omnis.

What are people's thoughts on this?  Sometimes I like it, sometimes not.  When I do, it is the spaciousness of the split omnis together with the grounding of the center pair to get rid of the hole-in-the-middle effect.  That said, I don't know that I've noticed soundstage smear or phase cancellation."


^^i do alot of 4 channe stuff too..ive found my 414's ~3ft split omnis with my mg210's ortf/pas makes for a fine mix at an outside gig.  the omnis inside are not the best but ive ran split subcards a couple of times with tolerable results..

[Patrick]

I had a show that was 1/2 second off in a 100 minute show....  I went along and remover 2ms at every minute of the longer recording... a pain in the ass??? yes!! did it work? Like a champ

Sorry to beat a dead horse in this thread.. But in this case the clock drift is probably not occurring every minute and also doesn't last 2ms.  So just because the two files are the same length doesn't mean that they're phase synced.  I'm sure that the recording sounds fine but there is definitely some ugliness happening between those two sources, especially close to your edit points. 

It's this kind of post work that makes it worthwhile to get into the venue early and run all my channels to one location and recording deck.

Edit: Spelling

[acidjack]

^^i do alot of 4 channe stuff too..ive found my 414's ~3ft split omnis with my mg210's ortf/pas makes for a fine mix at an outside gig.  the omnis inside are not the best but ive ran split subcards a couple of times with tolerable results..

I agree that for outdoor work, adding some split omnis to a 4-mic mix can really be a benefit - because I think you often do still want the more direct sound from a hyper or card as well. 

[tcf]

My main 2 ch rig is mics-audient Mico-702. Each box has a word clock option. I can also break the chain up and run the sbd into the 702, mics- Mico-digi handheld, synched by wordclock. I like this rig because I travel light a lot and can just use the 702 by itself, or re-bag it for 4 ch.

[F.O.Bean]

This is why I bought a Tascam DR2D Steve Still have my 2 x M10s for taping 2 diff stages at festies, but have my DR2D to record 4 chan at local shows. And for $125.00/Shipped for a DR2D, you CANNOT beat it

[Gutbucket]

I somehow overlooked this thread.

Continuing the slightly OT discussion-
I like running multiple channels for multiple reasons, and one of the important guiding ones is this:  I can keep a standard 'base-line' mic configuration and add to that to compare different approaches to my standard 'known' config.  That is hugely helpful in leaning which works better where.  But beyond that, I often set up the other channels not just as a totally separate pairs, but also with the possibility of combining things in potentially interesting ways.  A good example mentioned here already is spaced omnis + a center pair.  Either can stand alone, or I can play around with combining them.  If the center pair is coincident, that makes for even more options since I can simply sum the center pair to form a single forward faced mono center mic (M/S technique) and end up with a three channel config that avoids potential center phasing issues.  Recording more than four channels the potential combinations become many and interesting if you think about it a bit in advance.

Spaced omnis is an obvious thing to add to a favorite near-spaced or coincident pair, which generally has less potential phase issues than combining two near spaced pairs.

But, I want to mention an alternate idea for 'expanding on a known good configuration' which might be interesting for those of you interested in trying some three channel approaches by building upon your favorite near-spaced stereo pair setup- It's another Michael Williams approach (the Stereo Zoom guy) I read about in one of his AES papers awhile back which he calls 'Magic Arrays'.  Magic because they are multichannel mic arrays which can produce a number of different target outputs without changing the array.  In short that means that if you only keep the L/R pair and throw all the other channels away, you have uncompromised stereo, but if you keep the center mic too, you have 3-channel stereo which can be played back as either regular 2-channel stereo or 3 channel L/C/R.  Add more mics and you have the option for 5 or 7 channel surround or not, keep just the center mic and you have mono, etc. 

I don't mention this because of the multichannel playback thing though, since I know not many here are interested in that. I mention it because I think it would be a good approach for combining multiple channels without problems for two channel playback if you care to, without compromising your standard two mic config.

Most of the arrays use combinations of mic angle, spacing and time offset built on the Stereo Zoom stuff- meaning you typically need to put the center mic out in front of the stereo pair and apply a time delay to the center channel to get it to line up correctly and play nice.  But it's amazing to me that such a system can work like this at all, in that the imaging of the two channel pair matches that of the three channel setup and isn't screwed up by adding the center mic without changing the configuration of the other two.  Here's a link to a PDF of his Magic Arrays AES paper, which he's generously made freely available along with his other papers on his website.  Diagrams of the configurations start on page 14.  You can ignore/eliminate the two rear facing microphones which add 5 channel compatibility.  The arrays shown are limited to those using microphones with identical patterns for all channels in the array.  The L/R pair are common configurations anyone around here would be familiar with.  I haven't had a chance to give this a try but I'd like to, especially since the approach fits perfectly with my 'build upon what works rather than scraping and starting completely anew’ philosophy.

[bonghitwillie]

i do this with seperate recorders. usually sbd and stage mics. i then use final cut pro to sync them. i find that you lose a frame every 5 minutes or so. i just snip or add a frame at song breaks and it works well.

[SmokinJoe]

For the last 4 years I've had an R4 and love it for mics + sbd. Like Jack, I run that way most of the time.   I used mics/ua5/h120 + sbd/r09 about a dozen times before getting the r4 and I would hate to go back. I bought another identical Busman hybrid R4 for my daughter to use, and on the few occasions when I've wanted to align them in post I've been very happy to find they within .002 or .003 secs over an hour or so set. I'm tickled pink.