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[Jeff Ekstrand]

Another way to save money changing batteries it to get a good volt meter. Decide at which point you're going to change batteries, and stick to it. You'll find yourself changing batteries a lot less ambiguously (is that a word?)

Also, somebody pointed-out that they found a 9.6 volt battery. Most 9v start higher than 9.0 volts. Typically a wireless mic works with voltage down to anywhere around 8.3-8.5 volts, depending on the brand, throw distance, etc. 0.6v is not enough power difference to hurt anything, and it gives longer battery life than starting right at 9.0v.

One thing to remember about rechargeables, expecially 9v, is that each time you charge them, the maximum charge becomes lower. Eventually you may only end-up with a full charge of only 9.2 volts. If you charge your batteries every week, in about six months, you may start running into problems. Your time may vary before seeing significant charge loss, but that's why I don't trust rechargeable batteries.

I'd be especially concerned if I were at high altitude, as battery life is notoriously shorter.

[Kent Thompson]

We check each battery voltage before we install and will not install a battery below the 9.25 for a service. We are currently using energizers. The new voltage is running around 9.25-9.45 and averaging toward the 9.4 area. We still get the occasional battery which measures good before the install but never makes it through the service. Don't know what's up with that but it happens. We install new batteries before each service(they never make it through 2 services occasionally one will have enough voltage left to make it through practice night. We just donated a drawer full of 8.** batteries to a member who used them in hand held testing meters.

One question I have is does anyone remove the batteries after use?

How do you dispose of the used batteries?

[Jonathan kronc]

I quickly found this site (I have no idea if its a respectable one)

http://www.onlybatteries.com/showitem.asp?ItemID=14671.11&am p;cat1=14&uid=1970

, but this Li-ion battery has almost twice the mAh then the NiMH Mike listed and for only 4 bucks more you can't go wrong (as long as the battery is quality). Li-ion has no memory, the only thing that causes it not to charge fully is how old they are, they should also charge quicker then a nickel based battery (metal hydride or cadmium). Also a big plus you don't have to discharge them fully before charging them again, you can charge them whenever you feel like it. One of the draw backs of Li-Ion is that they are really fussy on how far you charge and discharge them, but those batteries had built in protection so my opinion is try a Li-Ion battery like those.

Jon

[Don Boomer]

Batteries for wireless is indeed an issue ... and becoming a larger issue all the time.

I just returned from California where they now require batteries to be disposed of as hazardous waste.  You have to purcahse a special container (for $60) and have it picked up when it weighs 40 lbs.

We just sold 700 wireless transmitters to BYU for classroom use.  We figured if the 700 units needed the batteries changed every day times 5 days a week times 50 weeks a year ..... that would be ... are you ready ... 380,000 batteries per year!  That's a lot of batteries to be throwing in the landfill. Our systems use NiMH batteries that charge inside the units just like using your cell phone.  NiMH batteries should be good for about 250 - 500 cycles.

[Jeff Ekstrand]

Don, do you have a link to the transmitters you're talking about that will charge like a cell phone? I'd like to see specs.

[Don Boomer]

http://www.sabine.com/sabine-professional-audio/SWM7000-engi neering-specifications.htm

http://www.sabine.com/sabine-professional-audio/True-Mobilit y-SWM7000.html

[Kent Thompson]

Well right away I see a problem with those wireless units. Using 2.4ghz can interfere with any wireless networks set up in a church which we have. Also if there are any 2.4ghz wireless phones in the building it could possibly cause problems. It also looks like you are stuck with AUDIX microphones for handhelds. Another microphone option would be nice. The rechargeable clip idea I like. I am sure you could turn it off but, I am not crazy about the modeling gimmick. The digital processing is interesting as long as the quality is acceptable. .o: 1.5v cells?
Have you encountered any interference problems like I mentioned with those units?

[Jason Ellis]

Our sound team and Music Minister sat down and discussed this just a few months ago. We too spend several hundred a year on 9v and AA batteries...

Our conclusion was that we would rather pay for the batteries then have a mic shutdown during a service and be a distraction. The cost of batteries is less than turning up the thermostat a degree or too or running the lights. The church wastes more money on facilities on a weekly basis then on batteries, in fact battery costs are almost immaterial in an accounting sense in regards to weekly expenses - so we decided to continue to purchases batteries.

We currently use Duracell Procells and are happy with their performance and we put fresh batteries in before Sunday morning worship. We do have a battery meter and after worship we save the decent ones for light duty events and practices and only use fresh batteries for worship.

[Don Boomer]

Not to hijack the thread ... but since you asked ...

First I have to quote Henry's quote ...
"Every new [intentional] radio emitter since Marconi’s 2nd transmitter has caused interference to other systems!"

There is potential for interference in any system ... but I think you'll find the problems very small and easily managable compared to what will happen after Feb 2009 to most UHF wireless mics.

These wireless mics operate on what's called the ISM band.  By international treaty that band is limited to low power devices... no TV stations and the like. One of our limitations is a big plus for most users and that is that 2.4g doesn't travel very far.  It's limited to about 100 yards.  Truth is that if you have about 25 feet or so of separation there is no interference.

Wi-fi and phones use a collision avoidance system and move their channels when they detect interference.  It depends on how many systems you need to use.  You could probably use 3 different wi-fi spread spectrum channels and still have about 30 channels left for wireless mics keeping the frequencies separate. It's easy to assign the frequency your wi-fi is at and there's a built-in scanner in our wireless system to measure the room.

Our transmitters were designed especially for NiMH batteries and their characteristics ... it was not an afterthought.  Alkalines may be used in emergencies but you do get over 8 hours continuous from a charge (and 250-500 charges before replacing the NiMH).  

Another advantages in the system is that the transmitter actually transmits battery run time.  Have you ever put in new batteries for a 10 minute soundcheck then gone to dinner and when you come back hours later wonder weather or not the mic was properly switched off.  I used to swap the batteries because I couldn't risk screwing up my client's show for a couple $$$ worth of batteries.  Everybody has little bar graphs ... but akalines always seem to look nearly full until they drop like a rock and die.  I wouldn't risk my reputation on them.

As far as Audix heads ... they are very rugged and have very good feedback control.  You can model the mic to sound like most other popular mics.  Honestly the mic models sound more like the wired mic they represent than just sticking that other capsule on some other manufactures wireless.  Ever notice how a wireless SM58 never sounds like a wired SM58 side by side.  That's because conventional analog compander circuits are noisy at low frequencies so other manufacturers are forced to roll off the low end of their systems.  We found a DSP solution to the compander problem and our transmitters are like 3 dB down at 20 Hz.

As far as the rest of the digital processing ... built-in FBX and/or 10 band PEQ on each channel, comp-limiters, de-esser, hi-lo pass filters and presets so you can set  a personal preset for each user.

Back to the thread ... if you use a lot of batteries, these systems are free!

btw ... what are the channels of your current stock of wireless mics and IEMs?

[Henry Cohen]

Kent Thompson wrote on Wed, 20 February 2008 16:57

Well right away I see a problem with those wireless units. Using 2.4ghz can interfere with any wireless networks set up in a church which we have.

It can, but it all depends on frequency/channel coordination and distance between devices. With a little planning, you can have several mixed (DSSS vs. FHSS) 2.4GHz devices operating simultaneously in the same venue quite well. Further, since the Sabine unit is frequency hopping and the carrier is only 300kHz wide under full deviation, it'll have virtually no effect on WiFi networks; however the 22MHz wide WiFi channel could interfere with the Sabine if too close together.

Don Boomer wrote on Wed, 20 February 2008 19:24

These wireless mics operate on what's called the ISM band. By international treaty that band is limited to low power devices... no TV stations and the like. One of our limitations is a big plus for most users and that is that 2.4g doesn't travel very far. It's limited to about 100 yards. Truth is that if you have about 25 feet or so of separation there is no interference.

Operating distance relies on effective radiated power output (RF output plus antenna gain), obstructions and overall environmental RF noise floor. Enterprise level WiFi and commercial grade 2.4GHz devices with high gain antennas - the very configurations found in event production and commercial environments - regularly propagate over distances far in excess of 100 yards. (Don - Your engineering department really needs to get rid of those consumer D-Link or Linksys access points and get some enterprise level models in there that have rated outputs of +20, +23, even +27dBm with which to do interference analysis ).

Quote:

Wi-fi and phones use a collision avoidance system and move their channels when they detect interference. It depends on how many systems you need to use. You could probably use 3 different wi-fi spread spectrum channels and still have about 30 channels left for wireless mics keeping the frequencies separate. It's easy to assign the frequency your wi-fi is at and there's a built-in scanner in our wireless system to measure the room.

Not all WiFi devices have spectrum sensing capabilities, and those that do don't do it dynamically; it only performs a scan at power up. Further, if there are three co-located WiFi devices on the three non-overlapping channels, there's no clear spectrum remaining between 2.401GHz and 2.483GHz (except for the two 3Mhz 'slots' between channels 1 and 6, and 6 and 11.

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