Topic: matrix delay

[DaryanLenz]

So, I have this idea up my arse, that says it wants to start making matrix tapes with a new mixer I just picked up.  Now I know delay issues exist in order to time align the mic and sbd sources.  So, theoretically, if I were to run mics say, at the sbd, how much delay are we talking here?  How about closer up?  Second, what kind of unit does one need to do this...preferrably not too exspensive...ie, 100 bucks?  Thanks for the help, I really appreciate it!
Thanks

Daryan

[Tim]

if the mics are within 100 feet of the board you should be okay without a digital delay unit.

[MattD]

Tim, I don't follow your reasoning. Perhaps a further explanation would shed some light on things. Why does distance from the board matter? Isn't the distance from the sound source also important? Assuming instantaneous transmission (no cable delay), if the mics are 100 feet away from the PA, then the mixer will receive the sound from the PA about 0.09 seconds later than the board feed. This is an audible difference.

-Matt

[Tim]

it was late, I meant within 100 feet of the PA, thanks!

rethinking my idiocy in the light of day and after a vigorous workout at the gym the rule of thumb is 1ms for every foot. I guess 100 feet might be a bit much  

[JeffK]

You won't notice a huge delay if you're within about 30 ft of the source.  So... most small clubs, you'll be fine running sbd/aud mixes, but outdoors or larger theaters, you'll wanna have a digital delay unit.  Even in smaller clubs, you'll notice that your sbd/aud mix tapes will sound MUCH cleaner with the delay unit in place.  The only one that I'm familiar with is the TC Electronics D-Two, which is a rackmount unit that you'll need AC for, sells new for a bit over $400, IIRC.

Tim is right though, with a guestimate of about 1ms/ft. of delay.  The actual delay formula has to do with temperature as well though, so it will actually change throughout the show.  Either way though, you're still a lot closer to being exact than not using a delay unit altogether.

[Todd R]

I think you'll need to be no further away from the stacks than 30 to maybe 40 feet.  I did a SBD+Aud matrix of SCI a few years back without a delay for the board feed.  Jon-O asked what I was doing, and I told him I was trying a matrix.  He sortof laughed, but told me to go ahead and try it.  I was recording by the board about 50 feet back.  Jon-O said it would work when you were 30 feet or so back, but had his doubts it would work 50 feet back.  Turns out he was right--it's not completely unlistenable, but has quite a bit of echo/reverb to it.  Recorded outdoors, but sounds like it was recorded from the back of a big hockey arena.  I'd never try it without a delay as far back as 100 feet--that'd be about 100ms delay difference and I bet would sound like ass.

I never found much in the way of a cheap, portable, DC-powered delay.  I did pick up, but never got around to using, an Alesis nano-verb.  You can pick one up for $50 or less.  About the size of a D8, it is an 18-bit digital stereo effects processor for guitar.  Lots of effects, including a digital delay.  No way of setting your exact millisecond delay, but you should be able to get a feel for it and do it by ear.  Only other issue is that it is AC powered so you'd need to use a power inverter to run it.

I'm curious if other folks have found a reasonably priced, portable, DC powered digital delay that would work for this task.

-Todd

[Jason B]

I bought a Behringer UB1832FX-Pro mixer especially for multi-mic and matrix mixes. It has a built in, 24 bit effects processor with 99 effects. I think there are 6 or 7 delay effects, but they are not individually setable. They are all preset delays.

I have made some board/aud matrixes with it, but have yet to do so in a room where my mics weren't within 30 feet, thus I have not yet had a chance to use the delay.

-JB

[John R]

jeff's right not only temp, but barometric pressure and wind of course.  jon-o uses the yamaha digital board for peters tapes and the stuff i get at blues and brews.  he IS the man.

jr

[Tim]

John are you actually in Telluride? God I love that place...

[John R]

moved down to seaside fla in dec after 12 years in tride.  going back for bluegrass, four corners, and hopefully blues and brews again if i can put it together.  you going to be there this summer?  have we met there?

jr

[Marc Nutter]

Hi All,

While you may not hear a discrete delay (echo), assuming equal levels of both sources) until about 50mS (about 55 feet) or more, the common sources being combined but out of time will cause significant comb filtering (cancellations in the frequency response).  Even a time arrival difference of 1mS causes combing to begin at 500 Hz and have intervals every 1k on up.

A good way to observe the impact of misalignment is to take two recordings of the same show, align them perfectly and then offset one of them by .5mS, then 1mS, and more to see how it works.  This can be achieved with a good software package that allows working with more than two audio channels.  The offset can be performed by dragging one file or through setting a delay on an insert or effects send.  

It won't be until about 40mS or more that you can actually detect a discrete echo.

While the initial tendency is to hear the combined board/audience ("matrix") recording as fuller and richer, due to the level increase of two common sources, you will gradually start noticing the changing frequency response.  I often find that it is one way to take two good recordings and make one mediocre one, unless great care is given to proper time alignment, including the changes that occur as the show goes on (heat and humidity), and changing the time offset as needed to maintain alignment.

As far as those who are interested in finding a delay unit, they are somewhat hard to come by.  Those used for sound system driver and cabinet alignment often include numerous functions that will not be of use to most home users, unless you also want a great crossover and EQ.  Then, expect to pay over $1000.00

Less expensive units like those from Rane and Behringer, available for $200-400.00, are known for their functionality and price point but not necessarily for optimal sound quality.

Still once you are in that price range, assuming you have a computer, you are well on your way to a recording package that would perform the exact functions and have more beneficial qualities to offer as well.

Happy Recording Everybody,

Marc

[jpschust]

Marc,

A question since you have so much knowledge on the subject.  which would be prefferable to the ear:

1.  A matrix made with a very high end digital delay in a 2 mic/sbd mix (nothing terribly fancy)

or

2. A "matrix" made with an aud recording and a patch off the board post mixed through software?  Would doing this negate the fq issue faced without the digidelay unit?

Jonny

[wboswell]

Marc-
Another ?  When you say "good software package", which would you consider a good enough package to matrix in the post without the dealing with such cancellations?  I realize that my question isn't necessarily fair, so here is another go:  Most people on the hobby level use programs such as Sound Forge 6.0, Wave Lab, and Cool Edit Pro.  Will these commonly used programs produce desirable results?  Thanks for your insight!

-William

[JAH]

Marc-
Another ?  When you say "good software package", which would you consider a good enough package to matrix in the post without the dealing with such cancellations?

-William

Samplitude or ProTools are the shit.  A product that you get what you pay for.

jah

[jpschust]

I'd probably use protools.  Soundforge and Wavelab arent meant for multitrack applications so much.  Yes they can do the combinations, however thats not really what they are meant for.  I'd want to be working in software designed for multitracking purposes.