Unusual field recording setup leads to unusual results

SonicPadawan

SonicPadawan

Member
Greetings,

A few weeks ago during a shoot I experienced something very unusual and rather mind-blowing to me. I'd like to try and describe my setup and results to find if anyone can explain this.

Setup:
I normally run a dual setup when recording on set, from the mixer output I split the mixer output signal each to my Marantz PMD-661 recorder and a breakaway snake cable which typically feeds the camera or sits unconnected in my bag. In this setup I typically have left channel on boom and right channel on wireless lav2 and/or lav1.
(SD 302 mixer -> XLR "Y splitter" cable -> Marantz PMD-661 Recorder & 15' breakaway snake)


Situation:
The director wanted a "Comtec" monitoring setup but I don't yet own one and budget didn't allow for rental so I took another XLR "Y splitter" cable, connected the two channels of the "Y" to the end of the snake, then connected the summed 1/8" connector into a spare Sennheiser G2 ew100 unit transmitter. The director wore the receiver and a headset for monitoring. No connection to the camera in this unusual setup.
(15' breakaway output -> "Y Splitter" -> G2 ew100 transmitter)

Result:
During playback from the recorder after shooting the first scene of the day, I didn't have channel separation - both boom and lavs where identical on each channel. I started to freak out. I checked and double checked my channel assignments on the mixer and found them to be correct - boom on left and lav 1 & 2 on right. Why was I getting identical signal on both channels in the recorder?!

I retracing my connection setup and I came to the conclusion that the "poor man's Comtec" configuration was the only change from my normal setup. I then disconnected everything from the snake. NOW I was back to having channel separation.

Question:
What in the world would cause that kind of result? Did my unusual connections cause some manner of back-feeding into my recorder? I don't know how that could be, but that's the only explanation I could come up with.

Thanks in advance for your thoughts and insight.
 
A great many important details are left out of your story. It would not be possible to give you an absolute answer without knowing many other things, quite possibly things that you don't know yourself without further research and/or testing.

But as I read your story, two phrases jumped out at me: "XLR "Y splitter" cable" and "summed 1/8" connector".

NO "Y-splitter cable" is a "summing circuit" unless it is specifically designed for that purpose. And I would wager lunch for the rest of the week that your's is a simple hard-wired Y-connection. That is an extraordinarily strong candidate for explaining how your two mic channels got shorted together.

There is no fundamental problem with your proposed solution. But you don't appear to have the proper adapters/cables to do it properly. That doesn't seem surprising since it is not a conventional application.
 
One of the downfalls of the SD302 mixer.. no mono output.
Even if you go to SD's website for the schematic and make a combining cable with resisters off the TA3 tape output, it will then reduce the channel separation on the XLR outputs. I have done this and tested it, not happy with it and sold mixer for a mixer with a built in mono output.
You went one step further in this direction by using a "Y" cable as a combiner/summing circuit.. as Richards said, this is a big No-N0!
Study, test, and know your workflow!
 
You shorted your outputs together so the mixed.

The only way you could do what you tried with out having that happen is to run the "split" into a mixer and have it combine the channels in to a mono feed. Or use the headphone out from you mixer or recorder, providing either will give you a "mixed" mono output.

Y Cables don't buffer anything so they are just two new "taps" into your out put. If you short those out they will have problems. Actually going down to the 1/8" connector also shorted out the balancing on your cables. So your probably lucky all you got was a mix and not a buzzing static mess.

BTW you should be monitoring your recorder which would have shown you the channels were getting mixed.
 
monitor for director on 302... And if it's not wirelles...Well, then it's not wirelles. Low budget is for everyone, so also for directors....

your monitor (headphones) on the maratz.
 
whenever i've been using my 302 and client has requested IFB i stick a splitter on headphone and warn them that i'll be listening to different modes of monitoring. and as long as i volume down for blasting tone i've yet to get complaints.
 
Richard Crowley said:
A great many important details are left out of your story. It would not be possible to give you an absolute answer without knowing many other things, quite possibly things that you don't know yourself without further research and/or testing.
Click to expand...
That's fair. But wasn't that my test and isn't this my further research? ;-)

But as I read your story, two phrases jumped out at me: "XLR "Y splitter" cable" and "summed 1/8" connector".

NO "Y-splitter cable" is a "summing circuit" unless it is specifically designed for that purpose. And I would wager lunch for the rest of the week that your's is a simple hard-wired Y-connection. That is an extraordinarily strong candidate for explaining how your two mic channels got shorted together.
Click to expand...

I think I tripped over myself when trying to describe all this. When I said "summed" I was trying to truncate my description for brevity. In actuality it was a XLR-M to XLR-F Y-splitter attached to a XLR-M to 1/4" adapter connected to a 1/4" to 1/8" adapter. A bloody mess, I know, but it got me to where I thought I wanted to be. With all that said and forgetting the ridiculous adapter setup I used, can you help me understand simply why merging two signals into one using a Y-splitter is not considered summing?
 
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BRH said:
One of the downfalls of the SD302 mixer.. no mono output.
Even if you go to SD's website for the schematic and make a combining cable with resisters off the TA3 tape output, it will then reduce the channel separation on the XLR outputs.
Click to expand...
But that's exactly what I want! I don't want channel separation for this purpose. Remember, I'm trying to get my mixer output to a wireless transmitter for the director (or anyone else with earbuds and a receiver) to monitor what I'm recording.

I can't yet afford the proper Comtek units so I'm trying to cleverly produce similar results. That's where I'm at.
 
Noiz2 said:
You shorted your outputs together so the mixed.

Y Cables don't buffer anything so they are just two new "taps" into your out put. If you short those out they will have problems. Actually going down to the 1/8" connector also shorted out the balancing on your cables. So your probably lucky all you got was a mix and not a buzzing static mess.
Click to expand...
You're definitely right about the mess part, and it surely could have been worse. I'd like to make sure though that I articulate myself properly in my original point and greater concern...
For this unusual setup there was two destinations for my mixer output - one to my digital recorder and one to the wireless transmitter with each being fed from the original Y-splitter cables. When you say shorted together (on the transmitter side of the output split), are you saying that caused me to lose channel separation on the digital recorder?

At the end of the day, I don't care about what happened on the wireless transmitter end. But I clearly lost channel separation on the recorder (only using this crazy setup) and that concerns me greatly. Fortunately for me it was only for one setup so really no one was the wiser.

BTW you should be monitoring your recorder which would have shown you the channels were getting mixed.
Click to expand...
Right, I totally agree. The thing is, for this scene setup, with one channel for the boom and the other for the lav, the shot was so tight that I could get in with the boom just as close as the lav was to the subject so what I was monitoring seemed identical anyway. The only reason I figured out there was a problem was monitoring between setups as the actors continued their rehearsal. THAT'S when I started questioning things.

dre83 said:
monitor for director on 302... And if it's not wirelles...Well, then it's not wirelles. Low budget is for everyone, so also for directors....

your monitor (headphones) on the maratz.
Click to expand...
You know, that is a really simple statement that really resonates through the bigger picture in all of this. They didn't have the budget for the extra gear that was needed to fulfill their request and while I originally said just that to them, at the last minute I tried to play hero and impress them with my cleverness. I think that's one of the valuable lessons I'm taking away from this for the future. And for that, I thank you.

manglerBMX said:
whenever i've been using my 302 and client has requested IFB i stick a splitter on headphone and warn them that i'll be listening to different modes of monitoring. and as long as i volume down for blasting tone i've yet to get complaints.
Click to expand...
See, another simple solution. I'll be tucking this one and the others away for future reference.
 
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SonicPadawan said:
...
Situation:
The director wanted a "Comtec" monitoring setup but I don't yet own one and budget didn't allow for rental so I took another XLR "Y splitter" cable...No connection to the camera in this unusual setup.
..t.
Click to expand...

Herein lies a basic lesson for all project management, including movie making. One's budget is NOT the amount of money one has available to allocate to the various expenses you'll incur and budgeting is not an act of deciding where to spend it. The budget is the bottom-up estimate of what it's actually going to cost to acquire the tools, skills, and materials necessary to do the job properly at a required level of quality and budgeting is the process of cost estimating. If you have that amount or more available, you're golden and the project can proceed. If you don't have that amount, you need to get more. If you can't raise it, your project is doomed to failure. You don't say "the budget doesn't allow for rental." You say "We need a Comtek in order to monitor properly and one will cost $xx to rent for the duration of the shoot. Add $xx to the budget to cover those costs."
 
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SonicPadawan said:
You know, that is a really simple statement that really resonates through the bigger picture in all of this. They didn't have the budget for the extra gear that was needed to fulfill their request and while I originally said just that to them, at the last minute I tried to play hero and impress them with my cleverness. I think that's one of the valuable lessons I'm taking away from this for the future. And for that, I thank you.
Click to expand...

I'm sure they had 5105403434354354354534534 different lenses, and there were 5545343043034343043434053435 director assistants, camera assistants, producer assistants and other people that still now you're wondering "what the hell were they doing there ???"

But indeed, as it comes to sound, they all want to have 304043545345343 wireless mics, 540154534564343 wireless listening for everyone who's only waling in the way
 
Steve House said:
Herein lies a basic lesson for all project management, including movie making. One's budget is NOT the amount of money one has available to allocate to the various expenses you'll incur and budgeting is not an act of deciding where to spend it. The budget is the bottom-up estimate of what it's actually going to cost to acquire the tools, skills, and materials necessary to do the job properly at a required level of quality and budgeting is the process of cost estimating. If you have that amount or more available, you're golden and the project can proceed. If you don't have that amount, you need to get more. If you can't raise it, your project is doomed to failure. You don't say "the budget doesn't allow for rental." You say "We need a Comtek in order to monitor properly and one will cost $xx to rent for the duration of the shoot. Add $xx to the budget to cover those costs."
Click to expand...

it's true...the problem is that person A will say "this will cost 100$", but if person B says "naaah, I'll offer it for free", they (= producers) all think everything relying to sound is always free.

They don't mind spending 521043054354534534343044304304304304304040 $ for camera gear (lenses, unusefull things, unusefull ****), but when it comes to gear for sound, they all want it free.
 
"With all that said and forgetting the ridiculous adapter setup I used, can you help me understand simply why merging two signals into one using a Y-splitter is not considered summing?"

Some basic electrical knowledge will go a long way here.

What a summing circuit does is combine some inputs into some outputs. They are one way devices. What you did added the inputs together but was a two way device so input A could actually flow back up input B. This "pollutes" your inputs so everything is connected. If you had gone into a summing amp the inputs would have stayed untouched and only the output of the amp would be mixed.

If you think of cables (and adapters are in most cases are just the same as cables) as pipes and your signal as a liquid. If you don't have any one way valves (check valves) in the piping all your fluids are going to get mixed up once you put in a Y adapter. Once they are mixed together you can't separate them. You put in a bunch of pipes with no check valves so it all got mixed up.

There is really no way to "sum" signals with out active electronics - ie something that needs power.
 
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