A few somewhat random questions

[egproductions]

Rather than creating a few threads I was hoping someone or a few of you could give a little insight to a few recent questions I had lately:

• When using a phantom powered microphone, is there any benefit of selecting 48v v.s. 24v on my preamp if the mic works with 24v?

• Lets assume all things are equal aside from microphone. This means using a high quality preamp, same recorder, same pickup pattern etc. What should I specifically be listening for to hear the difference between a high quality and low quality microphone. Lets say we are talking about hyper cardioid mics and then maybe the differences between supercardiod also.

• Why don't we typically see boom operators using cardiod condensor mics on location (or do we). Something like this:
• http://www.amazon.com/AKG-C214-Large-Diaphragm-Condenser/dp/B001AM5PS4/ref=sr_1_1?s=musical-instruments&ie=UTF8&qid=1350938428&sr=1-1&keywords=akg+c214

• What is being sacraficed in the audio when the limiters kick in (such as the limiters on the mixpre-d)

• If I split a phantom powered microphone so that I can bracket audio, am I loosing anything? Will I have to double each channels gain?

 

[Alex H.]

When using a phantom powered microphone, is there any benefit of selecting 48v v.s. 24v on my preamp if the mic works with 24v?

You may extend your battery life, but if you have 48v then use 48v for best output. Some mics will have higher s/n ratio as the power drops.

Lets assume all things are equal aside from microphone. This means using a high quality preamp, same recorder, same pickup pattern etc. What should I specifically be listening for to hear the difference between a high quality and low quality microphone. Lets say we are talking about hyper cardioid mics and then maybe the differences between supercardiod also.

Frequency response, distortion (depends especially if you're working with high SPL sources), handling noise... kind of depends on what you're recording, but frequency response is the first one. Cheap mics will have poor response on low and high ends, and may have nasty bumps in the mids that make things sound wonky. It's partially subjective, though... at a certain level, mics are up to personal taste. You just have to listen and decide what sounds good to you.

Why don't we typically see boom operators using cardiod condensor mics on location (or do we). Something like this:

• http://www.amazon.com/AKG-C214-Larg...=UTF8&qid=1350938428&sr=1-1&keywords=akg+c214

Because they are 1) heavy and 2) fragile.

1) Every ounce matters on the end of a boom. Back in the way, way old film days you'd see a large ribbon mic on the end of a boom, but that was on a Fisher Boom which is not hand-held but rather is supported on a fulcrum. That said, nowadays there are better response patterns and much lighter mics.

2) Large-diaphragm condensers are made for studio use, and are generally not suited to live up to the abuse of film production.

What is being sacraficed in the audio when the limiters kick in (such as the limiters on the mixpre-d)

It depends. If the limiters are just barely catching peaks, you aren't going to hear much - if any - difference. If the limiters are slamming full-throttle, then you'll hear the artifacts. First and foremost, the high frequencies will start to go.

If I split a phantom powered microphone so that I can bracket audio, am I loosing anything? Will I have to double each channels gain?

I assume you're asking about using a Y-cable splitter to connect one mic to two inputs? Bad idea, as it will impact the strength of the signal. If you're using the MixPre-D or the 302, rout the mic input to the center using your L-C-R pan switch. Then use the recorder's input controls to create your safety track. No, it's not ideal as it doesn't allow the safety to catch any problems in the mixer, but it's better than nothing. If you're using the 442 or 552, or something like the Shure FP33, you have a rotary pan control and can actually use it to create your safety by panning slightly to one side (which drops the level in the other output channel).

 

[Richard Crowley]

When using a phantom powered microphone, is there any benefit of selecting 48v v.s. 24v on my preamp if the mic works with 24v?

Some microphones need the full 48V to handle high SPL. OTOH 24V phantom power likely drains batteries less.

• Lets assume all things are equal aside from microphone. This means using a high quality preamp, same recorder, same pickup pattern etc. What should I specifically be listening for to hear the difference between a high quality and low quality microphone. Lets say we are talking about hyper cardioid mics and then maybe the differences between supercardiod also.

Differences would include: sensitivity, on-axis frequency response smoothness, off-axis smoothness, directionality, susceptibility to handling noise, and susceptibility to wind noise.

• Why don't we typically see boom operators using cardiod condensor mics on location (or do we). Something like this:
• http://www.amazon.com/AKG-C214-Larg...=UTF8&qid=1350938428&sr=1-1&keywords=akg+c214

a) Typically not directional enough for those kinds of distances in any sort of real-world location
b) Often they have off-axis frequency response that is different from on-axis.
c) Most LDCs are bloody heavy and you wouldn't want to be holding them up at the end of a boom.

• What is being sacraficed in the audio when the limiters kick in (such as the limiters on the mixpre-d)

The integrity of the original dynamic range. Frequently this is important. Sometimes you can make it up in post-production editing, but it is painful to fully reverse.

• If I split a phantom powered microphone so that I can bracket audio, am I loosing anything? Will I have to double each channels gain?

You typically don't lose anything significant. No, you don't have to double each channels gain.

 

[TheDingo]

When using a phantom powered microphone, is there any benefit of selecting 48v v.s. 24v on my preamp if the mic works with 24v?

Some recorders/mixers are more power efficient at lower voltages, so your battery may last longer.

What should I specifically be listening for to hear the difference between a high quality and low quality microphone.

The overall sound quality. ( how well does it capture the full audio frequency range, how much frequency separation does it reproduce, how much off-axis noise does it include, etc... )

Better mics sound better, have low self-noise, have low handling-noise, etc...

You need a good pair of headphones and a good headphone amp to hear these differences. ( mixers generally have much better headphone amps compared to recorders )

Why don't we typically see boom operators using cardiod condensor mics on location

The large diaphragm mics are much heavier than pencil mics ( 3-5 times heavier ), require much bigger and bulkier wind-protection ( again much heavier ), don't sound much better than higher end pencil mics.

It's a lot easier to hold a 3oz pencil mic with an 5oz Rycote softie ( 8oz total weight ) at the end of a 12 foot boom, than a 12oz large diaphragm mic inside a blimp. ( 16-32oz, 28-44oz total weight )

What is being sacraficed in the audio when the limiters kick in

Dynamic range. Everything beyond a certain audio level is being compressed to stay withing the maximum sound level. ( this can sound very "flat" and unnatural if not handled properly )

If I split a mic so that I can bracket audio am I loosing anything?

Normally no, but this may be unnecessary depending on the gear you are using. If the recording device has a very low noise-floor, you can set a lower recording level when recording, and then boost the audio level in post with no fear of ever hearing the noise-floor of the recording device from the boosted audio. Most low-cost recorders are too noisy for this, so splitting your recording levels is one way of extending the dynamic range of low-cost gear.

 

[Doc Bernard]

Be gentle with limiters..........set them so they just take the uppermost edge off. Too strong.....and you will hear them kick in. If you find you really have to use the limiters hard......then you need to invest in some inline pads.

 

[egproductions]

Amazing responsed all around! I really appreciate the knowledge sharing!

 

[ggrantly]

Egg

Your questions, and how you asked them should be a sticky for how to get a good response; ask specific questions in bit size chunks. So often the section gets the same questions over and over, and over. Like why does my low output mike not match up to my low gain preamps in my cheapo recorder, or how do I get great sound on a $200 budget. Some folks are just too lazy to research the braindead questions. You have a lot of posts, so you know how the board works, and the good responses you received are the result. Just sayin.

Grant

 

[paulears]

Can I just add something to the splitting question? We routinely split microphones, as it's essential for what we do, and the industry have been doing it for years. One microphone on stage, feeding the equipment in the audience for the front of house sound. The same mic gets split to the on stage mixer which feeds the musicians monitors, and if you are doing a festival, maybe even a third feed to feed the video OB truck.

There are a number of small issues, none of which really makes much impact - most of the time, but for the point of accuracy and perhaps future problem solving are worth tucking into your head.

First is signal loss - if you split the signal to two destinations then there is a 3dB loss. It's physics - however, it's hardly even noticed. Maybe if the microphone is very, very low gain, on a source that is very quiet, then when you ramp up the preamp gain, you could notice it. On normal sources, forget it.

Second is potential power supply problems. Power to phantom microphones is fed through a pair of matched small resistors, designed to limit the current. If you split a microphone to both channels on your camera, then you are 'connecting the phantom power back to itself' - putting the current limiting resistors in parallel. Again, in most cases, it makes little or no difference, but some cameras can only just supply the right amount of power, and the consequence of the change in resistance is that the voltage to the microphone can fall below the limit of good quality - still working, but perhaps just sounding a little rough and lacking in quality.

Third - and unlikely in battery operated equipment is ground loops - where there are multiple earth paths that can in mains systems introduce unpleasant hum into the system.

Fourth - perhaps rare, but worth remembering is that with a split system, any fault before the split wipes out BOTH channels. For me this means I never split audio on my cameras, I have an external mic on channel one and the built in mic on channel 2, just in case. I have never found a circumstance that needed a split to give different gain on two channels. My view is it's a lazy system designed to allow you to forget about sound. If you really cannot pay attention to sound levels, switch on the limiter, or worse, auto gain. Even auto gain is better than no audio, and on my cameras, the auto position isn't dreadful, and any abrupt changes can be sorted in post.

All of my splitter systems are 100% passive, and they've been very reliable. Some people swear by transformer splits that give electrical isolation between the splits.


I also use the kinds of cable splits we are talking about here to feed one microphone to two mixer inputs, just as we're doing in this topic. The reason is for instant changes in eq - so maybe channel one is for speaking and channel two has effects and processing for when they sing. I can simply bring one fader down and push the other up to change the sound of the mic. On digital mixers of course this is simply a memory recall, but the Y split is very simple, and our suppliers even carry them as a made up item.

 

[GaryNattrass]

Just as a side not we used Neuman U87 mic's on our large fisher booms but KM84's tend to be the fave these days, hand held poles usually have 416 type short shotgun mic's or hypercardioid's.

 

[Noiz2]

To add to Paulears post.

There are a number of ways to split the signal so that is part of why you will see variations on recommendations.

You can split it with a Y cable on the mic line or a Y cable after the preamp/ mixer. Up side is simplicity, down side is if you are using phantom power the Y on the mic line is going to be cross pollinating the power. Paulears hasn't had problems with this but I would be weary. He is working a concert with I assume some backups and sound checks. If your doing production work you not carrying a lot of extras and you are not going to have the same amount of time before you are "on". Don't try anything on the set you haven't really tested before hand. Splitter on the line out should not cause any problems. Both suffer from the problem anywhere is a problem everywhere issue.

There are dedicated mic splitters. They usually have some sort of isolation so phantom should not be a problem, providing you can have one leg pass the power on. An isolated output ought to be able to have a problem and not trash what's on the other side of the isolation so you get some protection there.

You can also on most mixers send an input to more than one output, thus splitting the signal. This is common in studios and places where you have a real mixer since you have good control over the split and each leg is it's own entity.

And a fair number of recorders allow you to split internally and send a reduced volume to another channel.


RE: limiters.

The SD limiters are very good and hardly noticeable unless you are slamming them. Some limiters have a slow reaction time and you get a "pumping" where the level shoots past the limit (possibly clipping) and then is pulled back. Those same ones often also have a slight lag on "recovery" of the return to an unlimited level. The result is similar to Auto Gain Control circuits.

So good limiters, not generally an issue, not so good limiters nasty badness.