Disappointing results...was it my GL2 / DXA-8 Levels? at DVinfo.net

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Old August 7th, 2004, 11:57 AM   #1
Fred Retread
 
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Disappointing results...was it my GL2 / DXA-8 Levels?

Note: Nothing that follows is an impeachment of the quality or performance of the AT987 or the DXA-8 (unless one of mine proves defective). It has to do with my equipment choices and technique

I'm quite disappointed in the results I got last night with my new equipment recording a musical in a small auditorium. I've learned that the directionality of a shotgun adds nothing in this envrironment where all the lead players are laved up and the room is filled with sound by loudspeakers. But my concerns go way beyond that. If anyone has time to read this long post and comment, I'd appreciate it.

I fed one channel of the DXA-8 with an attenuated XLR line from the sound board and the other with my AT897 mic. For placement, I had the phantom-powered 897 at the back of the auditorium with me, about 8 feet off the floor, with the intention of capturing all the ambient sound--direct live sound from stage, audience, and loudspeakers.

The channel from the board was tinny sounding and noisey. I was given the 1/4" "monitor" output from the Mackie, with all fifteen stage inputs (two hanging mics , three downstage surface mount boundary mics, and ten lavs) routed into that output by a single panel button. The 1/4" plug was, of course, converted to XLR for the 25 foot run to my adaptor. The tinny tone was probably a phase problem, because the stage inputs are arranged for a stereo array for the loudspeakers, and all those inputs are dumped into the one jack for me without much thought about that. The director is simply not a sound board expert, and neither was the band member who helped him decided what to give me. And athough he says he mutes the lavs of the kids offstage, I was still getting conversation and static from them. Apparently the signals going to the monitor output were ahead of the mute controls.

1. For the moment I can live with all that because it has nothing to do with my equipment purchases. But does my assessment of the above sound right?

A more disconcerting problem is with the AT897 channel. I got the coverage I was seeking, but I still wound up with the raspy scratchy distortion I associate with clipping during the peak passages (couldn't discern it in real time because the ambient sound drowns my headphones). This absolutely floors me because the DXA-8 is all about preventing that. I need to figure out quickly whether it's my technique or defective equipment. So a few questions about that:

2. The Beach instruction sheet, as well as Bryan B. in his posts and in his DXA-8 review, refer to settings of the CAMERA's gain controls in term of percentages. What does that mean? For instance, does "start with the camera's gain control at 20% of maximum" mean -14 dB, or 20% of the length of the scale visually, or 20% of control knob movement?

3. For operation with the limiters off, The Beach instruction sheet says to start with the camera gain low, about 20%, and to crank up the Beach gain until the camera's meter and/or headphones indicate an appropriate level. For the GL2 meter, the reference scale is an unnumbered succession of dots, with one large green dot at about 2/3 scale that apparently indicates a nominal level. The meter's dynamic indication is an increasing number of bars that are white below the green dot and orange above it. If you drive it high enough it will produce a red dot at the end of the scale. I assume that the orange bars indicate what we used to call "headroom" in analog recording, that the optimal level is to have one or two orange bars flashing occasionally, and that the red dot means peak distortion (man, I really dislike not having real numbers). Does this sound right?

4. For operation with the limiters on, which is the recommended mode, the instructions only say to crank up the Beach gain until the limiter LED's flash regularly. Although it doesn't say so, I assume that you then recheck and readjust for appropriate camera level indication as in number (3.)

Number (4.) is the way I recorded, and got distortion.

Tonight I'm going to record the performance with the (sigh) on board mic and AGC, so at least I'll be guaranteed something usable for a DVD.

TIA for any feedback, answers or advice.
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Old August 7th, 2004, 02:12 PM   #2
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I'd say to practice more before something important came along. (too late now). it sounds as though you're distorting at the camera, drop the camera gain and ride the beach. What was the level on the beach?

A shotgun is the wrong mic for ambience and placement at the back of the audience will bring nothing but grief

edit
my mind isn't working well due to increased pain meds, sorry

If you use agc and the camera doesn't overload than itwas the camera overloading. If not the overload is at the mic input.
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Old August 7th, 2004, 08:29 PM   #3
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Fred
Let me know how things work out. it's either an overloasd at the DXA input or the camera and we just have to figure out which. both problems are easily solved.
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Old August 7th, 2004, 11:40 PM   #4
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I agree with Bryan. I can't remember if you have your camera's Mic ATT switch engaged? I think that would be a must when using the DXA-8.
A couple of other things. Did you use a balanced TRS 1/4-inch to XLR or an unbalanced TS 1/4-inch to XLR adapter when coming out of the Aux Send from the board? If it's unbalanced to balanced, then that can cause phasing problems if it isn't wired correctly. Although it could be a situation like you guessed and that some spaced mics set up for stereo are not mono compatible in the aux send.
It is important to get a post-fader aux send if there are elements that have to be faded or muted. All Mackie boards have at least 2 aux sends and some have up to 6. There will be a mixture of pre-fader (which is also pre-mute) and post-fader sends.
Shotguns from the back of the space are often affected by the back wall reflection. Even if you are using something wider than a shotgun from the back of the room, it's beneficial to put it eiter as close to the wall as possible or instead at least 8 to 10 feet from the wall.
A wider mic from the front of the stage makes the best ambient mic, but sometimes in productions as you are taping, nothing sounds really spectacular including the board feed.
Let us know if you solved the possible overload problem and got any better results.
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Old August 8th, 2004, 02:30 AM   #5
 
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If the signal is out of phase at the cam coming from the mixer due to wiring, you should be able to open the two channel mix from the mixer in your NLE or DAW, and invert the phase of one or the other channels. This will *usually* fix the issue, but not always.
Can't add much more to the excellent responses/advice you've already received.
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Old August 8th, 2004, 10:15 AM   #6
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If I understand correctly he's only getting a one-channel mix from the board, but that's a good reminder for future two-channel work. It's easy to forget just how many different things you can try out quickly on an NLE to fix problems.
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Old August 8th, 2004, 11:33 PM   #7
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Duh!

Thanks, guys.

Jay, yeah, MIC ATT--where have I heard that before? I can't believe I ignored that simply because the Beach's sketchy instructions didn't mention it. But here's the deal:

DXA-8 maximum output spec:
Limiter on -35 dBu (12 mV)
Limiter off -30 dBu (25 mV)

GL2 Mic Input spec:
MIC ATT OFF -55 dBV (1.8 mV)
MIC ATT ON -35 dBV (18 mV)

The GL2 manual doesn't say which, but those must be either nominal or max. Anyway, it's clear enough that MIC ATT must be on with the DXA-8. It wasn't. Too bad. But at least everything falls into place, and I was interpreting the GL2's recording levels correctly. I was just recording a damaged signal.

I was getting "Monitor" not "Aux Send" from the Mackie, but it did have Aux Send outputs. As I said, there wasn't a really competent sound guy on site. On top of that, I have no idea whether the plugs or conversions were correct.

I got usable coverage with the on board mic last night and tonight so I'm okay.

I'll get another chance to try the mic and adaptor tomorrow, in a venue perhaps more appropriate for a shotgun--a little non-musical stage production where no one is miked up.

One more (for now) question: Any estimate of what the stereo channel separation is in a unit like the GL2? I can hear the off-stage lavaliere noise on the AT987's channel as well as the sound board's channel.
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Old August 12th, 2004, 07:21 AM   #8
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My simple observation, or more of a question is, were you able to headphone mix your channel from the board. If your sound guy just looked cool but couldn't find the power button, then his 'mix' to you might be a place to start. Just my .02
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Old August 19th, 2004, 05:43 PM   #9
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mixing and GL2 meters

The "tinny" sound you got could have been a phasing issue, but it could have occurred even at the sound board itself. If all of the channels were being sent to you all the time as you described (backstage sound still getting into the mix) there's a good chance that all of the mics just got dumped together onto a bus and piped to your camera. Sometimes you can get "comb filtering" problems due to extra mics picking up sound from other sources out of phase (do a google search for "3 to 1 rule"). 'Just one more thing to consider, though if this was the case I don't know if you could do much with the mixed signal now. A good sound guy and a post-fader, post-mute mix would do much better.

Some Mackie's have a mono (left+right summed version of the main mix) output which can work for recording (it also has its own level control on the back of the board next to the jack if you're having trouble taming it down).

As for the GL2 not having a scale on its level meters, I believe there are numbers on the small LCD meters on the side of the camera (between the lens and the flip-out screen). Also, if I remember correctly, the "green dot" is at -12db (nominal level since 0db digital is where things clip... hard).

A note of consolation... I tried using a mixer feed two days after I got my GL2. The levels looked good on the screen and were surprisingly "steady" for a live performance. I didn't have headphones to monitor it (***big mistake***). I found out later that the reason why it was so "steady" was that it was basically holding at the max level of the camera's preamps (aka distorting horribly). oops. I picked up some in-line attenuators from B&H that will hopefully help in the future.
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Old August 19th, 2004, 08:51 PM   #10
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we've been recording directly from the main balanced outs(xlr's) of my mackie 24-8 into the beachteck box mounted under my Canon gl1. The sound is awesome...
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Old August 20th, 2004, 07:04 PM   #11
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Bruce, do you mean you take a left and a right signal? What about ambience--do you get enough from the mic inputs to the board, or is this not an issue in your work?
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Old August 20th, 2004, 10:55 PM   #12
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Fred,
This was a small group that we recorded. We took the two ( left and right) xlr outs from the mackie. We got enough ambience from the mics(it was a real small club with a tiny stage), but I guess in a larger venue it would be better to add a couple of room mics ( or one stereo) for some addl ambience.I could set up the stereo mic, and run it through two channels of another mixer. then take the two outs from the Mackie, and run them into two other channels, and mix it all to the two ins on the Beachtek.
As an experiment ( during rehearsal the night before), i set up a decent sony stereo mic in the room, and recorded the group with only the stereo mic....pretty bad! It was like taking a video camera into a movie theatre.
Good luck
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