Boom or (digital)wireless

[Doug Brandon]

To bring up a favorite subject,

I've aimed searches and found 'wireless' and 'boom' mentioned variously here, but not necessarily head on. What are some of the recognizeable differences between the two? When should it matter to use one or the other?

Projects range from friends putting together zero budget meaningful fun to large scale 'can't miss a beat or heads will roll'. The expectations from the sound department seem to vary as well. Some are happy enough with what I consider poor quality, often times on larger scale productions. As has been mentioned before, some directors are willing to post/ADR various ammounts of their work. I don't think anyone really wants to do this, my guess is they've had bad experiences waiting for poor sound teams which somehow equated to honest costly delays.

My initial statements are (subject to individual perspective and circumstance--those are my late night defensive qualifiers, I'm not sure what that means), 1) wireless is faster..........until it doesn't work, and 2) wired boom is technically better (when properly executed).

As was discussed at Don Coufal's seminar, we as the sound team should have the say to what method is used to capture the signal. Variables will determine whether to use wireless or not, but how do we interpret these, especially when they come as 'orders' from production? For some shows, the techniques are obvious. Such as reality based television. Or Electronic News Gathering, or documentary style shooting. But when we have the time to lay cables and 'get in there,' should we option for the easy day and just stick a wireless plug on the end of the pole/belt pack ?

Don also mentioned that plain old experience plays a great role in deciding what to do. Obviously, a good boom operator can make all the difference in the world, as can placing a wire right the first time (which I still find myself humbly consulting with the pro's). Experience also says, just do what the Director wants. If ace director Joe Pytka doesn't want to see a boom pole, well then, Joe doesn't see a boom pole. The wireless had better work, no exceptions!

So why is it okay to use wireless when technically, hardwire is optimal? I guess cases such as Pytka's, if he wants to use it, then use it. Otherwise, if they're spending that much money on a project, give them the best. So where's the debate?

Simply put, most wirelesss transmitters are required by federal law to use a compander (compressor/expander) to minimize the signal in order that it fit into the limited bandwidths allowed for radio transmission. In some argument, this is okay in that companders are used in most types of professional noise reduction gear, ie. dolby and dbx. The signal then passes through two frequency doublers that bring it up to a range for radio transmission. The signal is reduced from radio transmission and expanded back to it's original width at the receiver. A decent site that explains terms such as 'compander'- http://harada-sound.com/sound/handbook/glossary.html

Arguably, this normal wireless system (the kind Sennheiser, Shure, Sony and many other's employ), without a doubt, does affect the signal.

Letrosonics' solution, which arguably still affects the signal, is to avoid the compander with some crafty work on the transmitter end by first converting the signal to digital (in the transmitter) and sending digital data over analog radio transmission, then decoding it at the other end. Now, if we are already recording digital at the cart, we've added a second AD/DA conversion. Herein lies another possibility for erroneous noises. If the sample rate at the converter in the transmitter is different than the sample rate on the cart, even though the signal has been converted back to analog, (I'm guessing) it seems the stair-stepping effect created by the bit rate transferred to the analog signal can possibly create artifacting to some degree. And if they are recorded at the same sample bit-rate, it seems (again I'm guessing) that they could play to or against each other again to some degree. But then, maybe not to any discernable levels.

I found a nice article discussing wireless transmissions at great length. This is an exerpt from the website that basically says what I just said (not including the bit-rate stuff which I try to explain afterword) http://www.audiosystemsgroup.com/wireless.pdf

In addition, most wireless mic systems also use noise reduction systems

(known generically as companders). They compress the audio level before transmitting

and expand it again in the receiver. When this is done well, the audio is not changed by the

total process, but noise in the radio link is greatly reduced. dbx and Dolby noise reduction

are other examples of compansion systems. Most of the better quality wireless systems use

companders, and are capable of dynamic range on the order of 105 dB. Some brands and

models work much better than others. This is another area where low cost systems tend to

be inferior -- their cheapie compansion circuits produce very audible pumping.

All analog wireless microphones, including those using compansion, must also use peak limiters

to prevent over-modulation according to FCC rules. While these limiters can help improve

the signal to noise ratio, it is important that they be adjusted so that they are not overused.

Most wireless mic transmitters have preamp input gain control accessible as a screwdriver

adjustment which can be accessed through a hole in the transmitter case. It should be

adjusted so that peak limiting is not audible in normal operation. Excessive peak limiting will

be audible as a pumping of background room noise and, in severe cases, as a loss of high

frequencies (the latter is caused by the pre-emphasized highs being limited more severely

than the rest of the audio).

Digital/Analog Hybrid Lectrosonics offers a conventional analog wireless system that uses

DSP to transmit audio as digital data over the radio link, then convert it back to analog audio

in the receiver. No analog signal processing or compansion is used – the DSP does it all.

You can see lectrosonics version of this story at http://www.lectrosonics.com/wireless/400/uh400atd.pdf which describes their commonly used 'butt plug' type transmitter.

It seems to me, there is a lot going on between the microphone and the mixer no matter which product of wireless one might use, and that to a discernable ear, one can hear the difference.

Many years ago I was surprised when my producer/engineer friend Michael Lutz (owner/musician of Brownsville Station fame-I hope he doesn't mind mentioning his name, I usually ask people's permission first), who prefers to record analog, and still records many sessions analog, was challanged by Apogee to tell the difference between his analog and their converters. A gal showed up at his studio with some equipment and plugged it into his monstrous Genelec's. They sat there and played like sound geeks for the entire day. End result, and the gal from apogee was quite astonished. Michael was able to recognize the digital conversions nine times out of ten. His bottom line, he told her no thank you, I'll keep things the way they are. It's an analog studio.

Some people can tell. Maybe not the average movie goer, but where do we draw the line on quality? If it's going to be wired boom, then does the old argument hold any ground of digital vs. analog at the mixer/recorder... 44.1k? 48? 96? 

As many of us probably know, the reason they came up with 44.1k is that the human ear at best can hear 20 to 20,000 times per second. Recording at 44,100 times per second basically eliminates the possibility of generally perceptable eroneous harmonic artifacts due to additive synthesis of frequencies under 22,050 times per second, slightly above what any human is going to hear.

The Bit rate determines the signal to noise ratio (this will all come together in a moment). The higher the better (I believe it's 6dB per bit....16 bit sampling yields 96dB S/N). Another way to look at it, the speaker moves toward and away from you with each up and down of a wave form (audio signal). At zero phase the speaker is dead center in it's back and forth capability. At 16 bit, there are 96 places a speaker can move to between the rear and the front of it's sway. The smaller the bit rate, the fewer number of spaces the speaker has to move to as it tries to emulate the uninterrupted characteristics of the original analog signal. Obviously, a sample bit rate of 1 would sound like complete trash as the speaker would have only six places to make it's stops across the entire amplified spectrum of quiet to full peak signal.

This stair-step effect of the sample bit rate has been a major area of increased quality to digital recording. Faster computers allow faster processing of higher bit rates. The higher the sampling bit rate, the less the speaker magnet stair-steps its way back and forth across its full amplification spectrum.

I don't think the *frequency sample rate 44.1k, 48k etc. makes too much difference (*as opposed to the sample's bit-rate) in dialogue recording, seeing as we are so close to the source (human vocal chords which, like stringed instruments, create a beautiful looking wave form-not a product of modulated wave, unless you couldn't get that low frequency air conditioner hum turned off), but I do feel the stair-stepping affect of just about any sampling bit-rate (not frequency sampling-rate) is going to have some kind of effect on the overall warmth of the sound. Maybe not totally perceptable all the time, but more of a subtle "I wonder why it is I don't like this sound' type of feeling.

Wired boom seems the best option. Have good cables.

Wierd boom ops seem the best option. Have good food on the tables.

(I believe )That's all I have to say about that.

Doug

[curleysound]

I've aimed searches and found 'wireless' and 'boom' mentioned variously here, but not necessarily head on. What are some of the recognizeable differences between the two? When should it matter to use one or the other?

...

Letrosonics' solution, which arguably still affects the signal, is to avoid the compander with some crafty work on the transmitter end by first converting the signal to digital (in the transmitter) and sending digital data over analog radio transmission, then decoding it at the other end. Now, if we are already recording digital at the cart, we've added a second AD/DA conversion. Herein lies another possibility for erroneous noises. If the sample rate at the converter in the transmitter is different than the sample rate on the cart, even though the signal has been converted back to analog, (I'm guessing) it seems the stair-stepping effect created by the bit rate transferred to the analog signal can possibly create artifacting to some degree. And if they are recorded at the same sample bit-rate, it seems (again I'm guessing) that they could play to or against each other again to some degree. But then, maybe not to any discernable levels.

Doug,

  Great post! I do want to bring up that Lectro also has the UDR700, and UM700 which keep the audio at 24Bit/44.1K(?) all the way through, and have an AES digital out from the reciever. I don't know why they don't try to promote/develop that more, but it's not my company...

As an occasional user of wireless boom, I think that it is a great tool to have in the box. I break it out if a shot needs it, or if the conditions are perfect, and I feel like having an easy day. It's one of those calls I make, with the best of intentions, and if it affects the quality of what I'm doing, even for a second, then I take it back to the safe old boom snake. I also think that using top notch gear is very important in this situation. I would never do wireless boom with even an older (VHF, non-diversity, or fixed frequency) lectro set, unless I was able to verify beforehand that it would be untennable. Also, I do a fair amount of ENG work, and I have never done the wireless camera link. I hate recording to camera in the first place, and that's a little too risky for my taste.

I also have a regular TV gig, where the production requires hidden lavalieres on all talent, and while that seems myopic, the result is that I've gotten quite accustomed to hiding mics on all kinds of wardrobe from nervous actresses in sheer dresses to stand-offish rock stars in leather and heavy jewlery. It is now no problem for me to do so on a film set, so I guess if the situation demands it, I try to make the best out of it...

Tom

[Doug Brandon]

Thanks Tom,

I'm not sure about all that I wrote--sometime during the middle of the night (should have been sleeping, dreaming of short post's).

Specific questions may not seem clear. I had in mind somethings like:

"Can anyone hear the difference between using good wireless booms and laying cables?"

Has anyone ever heard any strange sounds in the signal after using 'digitalhybrid' wireless boom tx/rx's? Older style wireless booms?

When my friend told me he could hear the difference between the sampled sounds and analog recorded sounds my reaction was kind of, 'yea, but it still sounds good enough to make a platinum album.' And sure enough they do. And they also record great movies and television shows as well.

It was brought up outside of this forum that some compromises in sound are acceptable, which I agree they are. There have been great movie/television shows made with less than premium circumstances that have sounded great and gone on to win prestigious awards.

It is the overal finished project that determines it's overall character being good, bad or great.

I see many shows on the teli where the sound is frankly awful. But the shows are being aired. That's where we are today in entertainment, and it is what it is. Personally, I just want to apply the best possible solution for any givin situation and that's what I'm trying to learn about here.

I'm not complaining. My heart goes out to people like VIN in India (kind of a tongue twister) or Alan Chong in Singapore. It sounds like they have their hands full trying to capture a clean track. Keep up the efforts!

Doug

[Guest Eric Lamontagne]

OK,

it's easier to go wireless, so is not brushing your teeth in the morning.

When I go to set, I got for ALL the sounds, foley, BG, EFX, and dialog. just jingle your keys through a wireless link to find out how untrue your foley is!

Also, you are judged on your sound produced at the end of you day. If the transient of the slate through a wireless boom sounds bad but the dialog is fine.....hummm what does everyone down the chain say behind your back when they sync, view dailies, online, etc etc especially in a controlled environment!

It's a compromise that I sometimes use, but never always!

Good Luck

Eric

PS, body mics sound as good as the clothing noise/muffle permit

[Guest Mick]

We've used wireless everything on CSI for seven seasons with little in the way of sonic problems and only a small amount of interference issues that I'm sure will increase over the next year or two. I am not audiophilic (?) by any means. I like the sound that I get from wirless transmission of my Neumanns and so does post, but I think the difference between the "wired" sound and the cabled sound is not significant enough to make an appreciable difference. IMHO

[Jeff Wexler]

OK,

it's easier to go wireless, so is not brushing your teeth in the morning.

Also, you are judged on your sound produced at the end of you day.

It's a compromise that I sometimes use, but never always!

Good Luck

Eric

I think some of what is being said here is that ALL recordings can most probably be referred to as compromised, or certainly the methods and procedures used have involved compromises. The general topic of this discussion is how much of a compromise is the use of wireless boom in today's production recording environment. I am of the school of thought that prefers to NOT have this question answered just by polling the shows, the movies (or even this group) and letting those things determine the answer. For example, just because 90% of the current TV shows may be using wireless boom, and people are still watching (and listening) to these shows, does not mean it is a good thing. From experience I do know WHY wireless boom is the norm on the TV shows but for me personally I consider it too much of a compromise (and yes, I DO hear the differences). Whether anyone else down the chain, or even the audience, can tell the difference...  I don't know.

There is a lot to be said about the evolving technology and techniques we have today, but as I have said before, many times, I think the sound in movies in the 1940's was often better than the sound we have today, for a whole lot of reasons. I would not want to turn the technology clock back but I would like to turn the procedure, practice, attitude and artistry clock back a bit --- no such luck at this point, the cat's out of the bag for sure ("what's your problem... I heard them talking!").

Regards,  Jeff Wexler

[Guest Mick]

"There is a lot to be said about the evolving technology and techniques we have today, but as I have said before, many times, I think the sound in movies in the 1940's was often better than the sound we have today, for a whole lot of reasons. I would not want to turn the technology clock back but I would like to turn the procedure, practice, attitude and artistry clock back a bit"

Jeff, I'd love to hear what you mean by that. Personally I've yet to hear a movie from that era sound anywhere near as good as the average movie today... but I'd be open to a change of opinion.

regards

Mick

[larry long]

Ok  I've been thinking about this a lot. reading and talking to folks.

My favorite thing ( and perhaps it's because I use a cooper board ) I love the preamps, they are fat and full. When using the lectro plug on, it sounds good for the most part but when you need to adjust on the fly you have little control. I don't think I can go wireless yet. They are convienent. How about a really nice line lvl out pre with a chunky transformer before the TX?

If I let my ears relax too much , or my head, will I hear me fall ?

LL

PS STFU Larry it's the whiskey.