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Author Topic: Wireless microphones for use in screen with CP750
Ross McLaughlin
Film Handler

Posts: 22
From: Worthing, West Sussex, UK
Registered: Feb 2012


 - posted 06-26-2013 08:28 PM      Profile for Ross McLaughlin   Email Ross McLaughlin   Send New Private Message       Edit/Delete Post 
Hi,

My manager is looking at doing some Q&As and other events when we'll need wireless mics to use in the screen, plugging into our CP750. The booth is about 40-50 metres from the front of our auditorium - just wondered whether anyone had any experience with fairly reliable (and preferably cheap) mic sets?

Many thanks

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Randy Stankey
Film God

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From: Erie, Pennsylvania
Registered: Jun 99


 - posted 06-26-2013 10:00 PM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
The best kind of wireless microphone is the kind you plug in. [Wink]

Don't get cheap wireless mics. You definitely get what you pay for! You'll want a mic system with dual diversity. Diversity systems have two (or more) receivers inside one unit and two separate antenna inputs. The system monitors both sides and picks the one with the best signal. There's less chance of losing the signal that way because one antenna/receiver should always be able to get a signal. There are also frequency agile systems which monitor several radio frequencies to find the one with the least interference. None of these features come cheap. Expect to pay $500 to $750 (USD) per microphone/receiver set.

Seriously consider getting external antennas to mount in the theater and run the feed cables through the wall (conduit) to the booth. There are many good wireless systems, these days, but few are THAT good that they can go through walls and punch through all the electronic interference that's usually present in an average projection room. That's two antennas for a diversity system. Mount them several feet apart in an area at the rear of the auditorium. Not necessarily line-of-sight but it's often better if you do. Probably $100 (USD) for a set of antennas and mounting hardware. Coax cable to feed the antennas to the receivers is extra cost.

Also consider an antenna distribution amplifier. With a distro, you can feed four or more receivers, allowing you to run multiple transmitters and receivers on only one set of antennas. It also amplifies the signal, giving you better range and reliability. Expect to pay $750 to $1,000 (USD) for a distro.

All of this equipment usually can be mounted in a sound rack, making it all easy and convenient to set up and maintain. Outputs of these systems are often XLR microphone lines. The CP650 has XLR mic inputs for PA use. Not positive but I think the CP750 does, too. In which case, you ought to be able to just plug it in.

Spend a few bucks on a rack mountable drawer. You can keep your handheld transmitters, spare batteries, accessories and user manuals all in the drawer. They'll be safer and less likely to walk away. When you're paying $1,000 to $2,000 on a set of equipment, you don't want to lose it. The drawer will help you keep tabs on it.

Two mics, two receivers, two antennas, a distro and accessories is probably going to cost $1,500 or more, depending on dealer pricing/discounts. Again, don't go too cheap. You'll regret it!

We have Audio Technica wireless mics, receivers and distros at Mercyhurst. They work well, they're robust and, once properly installed, are virtually turnkey. Other brands are good, as well. They are mid priced. Not too cheap. Not too expensive. And I have experience using them.

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David Buckley
Jedi Master Film Handler

Posts: 522
From: Oxford, N. Canterbury, New Zealand
Registered: Aug 2004


 - posted 06-27-2013 02:38 AM      Profile for David Buckley   Author's Homepage   Email David Buckley   Send New Private Message       Edit/Delete Post 
Or as us sound boys say: a $1,000 wireless mic works nearly as well as a $5 cable.

Sennheiser are also a respected maker of wireless kit, that works really well.

The only observation I would make is that it helps to have a compressor / limiter in the chain to keep the audio levels approximately consistent to improve intelligibility. The most convenient setup is a "channel strip" which is approximately a single channel of a mixer, plus a compressor, all fitted in a 1u rack mount box.

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Carsten Kurz
Film God

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From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 06-27-2013 04:47 AM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Yep - 40-50metres and connection within the booth definitely needs a quality system.
Best would be a receiver/antenna mounted inside the auditorium, and a cable leading into the booth. The CP750 has a symmetrical mic input, so, even placing the receiver near the screen and feeding a 50m cable to the booth would be an option. Especially since it could be a rather cheap wired backup option. You always want backups.

I don't think you absolutely need a system with detachted antennas in this scenario. But if the money is there...

Over longer distances and within a cinema environment, you have to expect 'irregular' events. E.g. at our cinema we had a rather cheap AKG system with the receiver placed inside the booth. It never caused problems during short announcements or testing. But it happened that due to temporary installations for special events the receiver needed to be placed in slightly different locations, and that changed the situation completely. Also, when we had longer speeches, it turned out that the 'perceived' reliability suffered considerably. Once we had an event with three business people surrounding the microphone, each of them with a cell phone or pager in their pockets. Usually these things are not considered harmful, but over a longer transmission distance and if these noise sources are in close proximity to sender or receiver, they can be a real problem. I also once had considerable noise from the receiver because some idiot placed it right beside a BluRay Player. 10cm away and the noise was gone.

If you have a short dropout during a 10s announcement, hardly anyone will notice.

If a local business rents your auditorium for a presentation and their CEO has a dropout every minute, you want to run away...

We solved that issue by placing the receiver on the back wall of the auditorium and running a cable into the booth. If I had to buy a new system, I would never go with that type of equipment again. Something in the range of 500US$ up should be sufficient. Maybe a dual receiver with two mics.

- Carsten

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Ken Lackner
Phenomenal Film Handler

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From: Atlanta, GA, USA
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 - posted 06-27-2013 08:15 AM      Profile for Ken Lackner   Email Ken Lackner   Send New Private Message       Edit/Delete Post 
quote: Randy Stankey
Probably $100 (USD) for a set of antennas and mounting hardware.
Would you not simply purchase the mounting hardware and use the antennas that would normally mount on the receiver?

quote: Carsten Kurz
I also once had considerable noise from the receiver because some idiot placed it right beside a BluRay Player.
Hey, now. I never would have thought that a BD player would be a source of interference for a wireless mic system, and I doubt most people would consider me an idiot. [Razz]

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Jim Cassedy
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From: San Francisco, CA
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 - posted 06-27-2013 08:32 AM      Profile for Jim Cassedy   Email Jim Cassedy   Send New Private Message       Edit/Delete Post 
quote: Ross McLaughlin
just wondered whether anyone had any experience with fairly reliable
(and preferably cheap) mic sets?

Since you specifically asked for info on reasonably priced wireless microphones
I can tell you that I've had excellent results with several mid-priced ($150usd)
from NADY systems. You can either buy direct from NADY or find them on e-bay.

However- - the digital equipment & xenon power supplies in modern projection
rooms tend to put out a lot of radio-frequency noise. The LAST place you want
to put your receiver is in the booth- - even if it's near the porthole.

At the distance you mention, it would be best to find a way to put your receiver
behind the screen or as close to the front of the auditorium as possible and
then run good microphone cable back to your CP-750.

In my experience UHF microphones tend to be less prone to RF noise spikes than VHF.

Be aware that the first time you use any microphone with the CP-750, you may need
to go to the MIC INPUT tab in the CP-750 setup software and establish a level
and enable or disable phantom power depending on what type of mic you're using.
You'll also need to decide which speakers your mic sound will be sent to.

Also- - just an anecdote: I have a 2nd "cheap" NADY wireless system which I
use when I need extra microphones at big events that I only paid $US80.00 for.

It performs almost as well as the other system I paid twice as much for,
the only difference I can hear is that the audio from the "cheap" system
sounds a little 'thinner' than that coming from the more expensive one.
But the only way you can hear this is if you do an A/B listening test
using the same speaker talking into both microphones at the same time.

In actual use, the slight difference in audio 'fullness' is inaudable.

Also- for some reason, at one location, there is some sort of radio frequency
signal eminating from a house located behind the theatre that jams one of
the wireless micorophone frequencies (209.15mhz) making one of the microphones
unusable. But I've only encountered this at ONE location out of dozens I've used
(or let others use) this system at. So it's just an anomoly to that location.

In short- - if you can afford an expensive system go ahead & spend the big bucks,
but there are also a lot of low-to-midrange systems that will proably work for you.

It depends a bit on your situation and who will be using your facility.

As someone else has pointed out- - if you are going to be holding conferences
involving big-wig CEO's of major corporations, you NEED to spend some money.
(and charge them accordingly for the theater rental!)

But if you're just going to be catering to smaller businesses or community groups,
where an occasional audio drop out can be a bit more tolerated, you'll probably
do just fine with a mid-range priced system.

Final word: By all means stay away from really "cheap" wireless systems.
(Anything from Tandy/Radio Shack for example)

Good Luck!

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Richard Hamilton
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From: Evansville, Indiana
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 - posted 06-27-2013 08:57 AM      Profile for Richard Hamilton   Email Richard Hamilton   Send New Private Message       Edit/Delete Post 
When MegaSystems was around, we used these , both hand held and lapel mics. I never saw them "in action", just installed and tested them. Not sure which model, but probably in the lower range because they weren't used often. Any way, they worked fine and were rack mountable with the kit.

Rick

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Randy Stankey
Film God

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From: Erie, Pennsylvania
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 - posted 06-27-2013 09:08 AM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
quote: Ken Lackner
Would you not simply purchase the mounting hardware and use the antennas that would normally mount on the receiver?
The antennas supplied with the receivers are usually "rubber duck" style antennas. I have done just as you say, mount the stock antennas remotely and cable back to the receiver. It does work that way but the accessory antennas are better.

Depending on manufacturer and the frequency range the system runs on, you'll either get vertical, "Sputnik" style antennas or Yagi/LPDA antennas. You'll get much better gain and less interference. Yagi/LPDAs are more directional, too.

When we first started out, I mounted the stock antennas on the wall and they worked but, once we finally got the purpose made ones, they were noticeably better.

I once built a set of antennas out of copper-silver brazing rod. They worked pretty well but, we bought a new wireless system and got the factory made antennas. I gave my old homemade antennas to a friend who runs an amateur radio club. He now uses them for "bird dog" exercises.

I think my antennas were better but it was just as easy to buy them ready-made.

Personally, I prefer to put my receivers backstage or in the booth. Your average presenter does not understand how microphones work. Putting them near the stage just means you have to run farther (and in public view) when it becomes necessary to troubleshoot or make adjustments.

Bob Ballard came to my theater to give a lecture. He "accidentally" put his microphone on mute. When he walked out on stage and his mic didn't work, guess who everybody was looking at? It was MY fault because HE fucked up!

Subsequently, I learned to put the receivers where I can get to them easily and to tape or use safety covers over all the controls on the transmitters to prevent naive users from fiddling.

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Sean McKinnon
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 - posted 06-27-2013 10:05 AM      Profile for Sean McKinnon   Email Sean McKinnon   Send New Private Message       Edit/Delete Post 
This brings up a question... I always felt that since during theatre construction electricians were being paid to pull speaker wires from the booth to behind the screen how much extra would it have cost to have them throw in a couple runs for xlr inputs under the screen? Maybe not in every house in a complex maybe just the big house. Would doing this have added significant construction cost or is it an issue of not identifying a need in the average commercial complex?

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Ross McLaughlin
Film Handler

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From: Worthing, West Sussex, UK
Registered: Feb 2012


 - posted 06-27-2013 11:18 AM      Profile for Ross McLaughlin   Email Ross McLaughlin   Send New Private Message       Edit/Delete Post 
Thanks everyone - now just have to speak to the money man!

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Carsten Kurz
Film God

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From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 06-27-2013 02:52 PM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
quote: Sean McKinnon
Maybe not in every house in a complex maybe just the big house. Would doing this have added significant construction cost or is it an issue of not identifying a need in the average commercial complex?
As a matter of fact, pulling in a CAT6 oder CAT7 cable is usually cheaper than dedicated mic cable, but can be used for all sorts of purposes - and it gives four channels of symmetrical audio, any direction. A roll of 100m quality cable costs less than 100US$.

I usually recommend putting in two lines of ethernet cable from the booth to one or two locations in the auditorium. In our auditorium, it runs along the speaker cables so we could use large parts of the existing wall openings and conduits.

Analog audio (bidirectional), analog video, digital audio, digital video, DMX, remote faders, format switches, RS232/RS422/RS485, networking, remote control, intercom - everything is possible with either low cost passive or medium cost active converters. The same type of cable could be used if you decide to replace your amps from the booth to behind the screen, for either multichannel digital or analog audio. IMHO, a no-brainer.

- Carsten

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Louis Bornwasser
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From: prospect ky usa
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 - posted 06-27-2013 05:34 PM      Profile for Louis Bornwasser   Author's Homepage   Email Louis Bornwasser   Send New Private Message       Edit/Delete Post 
All this info is really good.

Don't forget the obvious: Distance is your enemy. If you have interference, you can mount your receiver in the basement just below the speakers table or behind the movie screen. Normal wiring up to the amplifier. The mike signal will be higher than the interference.

In this way, even a cheaper system can be OK. Wires, though, are ALWAYS better.

Note: mike wires in a speaker conduit are always a no-no because of the level difference. louis

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Carsten Kurz
Film God

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From: Cologne, NRW, Germany
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 - posted 06-27-2013 06:12 PM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
No problem with differential transmission. A NoGo indeed with singleended wiring.

- Carsten

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