How to build a Stereo Microphone and Battery Box

[BlastM]

Hey, that looks like my design!

After opening three 9V batteries (two of them Duracell like the howto) none of them had the plastic case thing, but instead cardboard-backed contacts and cheap, thin plastic wrapping. So I had no choice but to use this design, and it's worked very well.

Instead of hot gluing the whole thing, I just put duct tape over the components as I wasn't sure how hot it would get (not very, but I didn't know if I had shorted anything) but I do plan on covering it all in glue now.

The first recording was at a heavy metal show. Not the loudest show I've been to, but I got good results with very little clipping standing just behind the soundboard. But the sensitivity of the capsules is noticably different so I'll have to match a pair.

Thanks for the howto greenmachine!

[greenmachine]

Very nice. The capacitors look somewhat large-ish, don't they?

Be sure to loop the cable around the board before finishing it and be careful that no glue enters the jack.

[woulfer]

Well, I've done it also. Thanks to greenmachine for this great diy (and a little extra help). I have posted a song from my first band recording. It's a local metal band. It was very loud, and I could pick the mix apart, but I think the recording turned out great. Please take a listen and let me know what you think.

[attachmentid=1209]

Edited December 8, 2005 by woulfer

[renho3k]

i made a diy battery box and encased it in a radio shack project box, but i like your design better because the project box is just too bulky to carry around. well, that and my friend decided we should put a big red button switch on it so it sorta resembles a bomb detenator. getting caught sneaking gear in is one thing, but now my biggest fear is having to explain why i have this sketchy device on me. anyhoo, question for the floor: how long (approximately) does your 9v battery last? do you put a new one in before each show?

[greenmachine]

Assuming that the microphones consume less than 1mA and battery capacity of an Alkaline is in the ~300-500mAh region, the battery should last about 300-1000 hours. I put in a new one once the voltage drops below 7V or so. If you don't constantly use it, it should last at least a year or so. Putting in a new battery before each show is a waste.

[woulfer]

Hey guys. Check out my new diy battery box. It is housed in an Altoid's Gum tin. It's the perfect size (not much bigger than greenmachine's), and I feel more comfortable that it has some protection.

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[SkttrWave]

So, I'm trying to make both a battery box and a pair of binaural mics (with panasonic mce2000 caps). I'm a noob on this area, this will be my first experience with soldering and putting an electronic device together.

I'm basically facing 2 material problems. first I've found it hard to find the 3.5 mm stereo connector with the cable as shown on the pics on the first page. I've cut open a (bad quality) pair of earplugs but it didn't look like cable on the pic. Maybe someone could point me in the right direction on where to find these. I've got some 3.5mm jack > dual mono RCA cables lying around, would these contain the cable needed?

Second I just noticed I've only got 0.25W 10 kOhm carbonfilm resistors. Could I use these instead of the metalfilm resistors? What will be the difference?

Thanks in advance

[greenmachine]

So, I'm trying to make both a battery box and a pair of binaural mics (with panasonic mce2000 caps). I'm a noob on this area, this will be my first experience with soldering and putting an electronic device together.

I'm basically facing 2 material problems. first I've found it hard to find the 3.5 mm stereo connector with the cable as shown on the pics on the first page. I've cut open a (bad quality) pair of earplugs but it didn't look like cable on the pic. Maybe someone could point me in the right direction on where to find these. I've got some 3.5mm jack > dual mono RCA cables lying around, would these contain the cable needed?

Second I just noticed I've only got 0.25W 10 kOhm carbonfilm resistors. Could I use these instead of the metalfilm resistors? What will be the difference?

Thanks in advance

1) I found them in a local electronics store and have a few left. PM me if interested.

2) These usually have somewhat greater tolerances (+-5% instead of +-1%). Actually it makes very little difference unless you do it professionally. You can use them without thinking twice. If you have more than two of them, you can use a mulitimeter to match them by yourself.

[SkttrWave]

I'll just use those carbon film resistors then. Thanks for the offer on the cables. Tho, I just cut open one of the jack > dual mono RCA cables and those are the ones I need, so it won't be necessary for you to send me the cables. I'll post some pics when I'm finished, which will hopefully be at the end of next week since I still have to receive some parts I ordered.

[igorxa]

a while back i inherited a pair of audio technica mini cardioids, at831c's to be exact. they came with no power module, and terminated in mini-xlr plugs. i've played around with them with my sony d7, and with or without phantom power (there seems to be little performance difference that i've noticed. it's been a while since i've used them with phantom power, though, so i could be remembering this wrong. the last show i used them with pp was coldplay in 2003. now that i think about it, it seems with pp the recording suffered from much less clipping.), by themselves they overpower the mic-in for most shows, and don't quite push enough for the line-in. my question is, instead of getting some electret capsules and making my own mics, could i use the at's with your battery box? i'd really like to come up with a sleek solution with the at's, since they're obviously higher quality than i could make myself (one day i'll track down and invest in a matched pair of omni caps to swap out when i want to. it was quite a pleasant surprise to find the heads unscrewed.), but i don't want to risk damaging them. i lost the pp supply and have since rigged up a variable line attenuator to keep the clipping to a minimum through the mic imput.

and one day there will be a non-ipod linux solution to line-in recording with my ipod video, and i'd like to have these usable with that as well. any help/advice you have would be very welcome.

[mightymouse]

Hi,

I'm totally new to live recording and even more to all the technical details here. Since I have a minidisc I thought to give this DIY a go. I think it's clear enough for even a total beginner like me. So thanks for this DIY.

I just have one question about matching the microphone capsules.

How do I do this? Do you mean by matching that they should have sequential numbers?

Thanks

[greenmachine]

Matching is the process of finding two (or more) capsules that perform (close to) identically in order to keep channel differences at a minimum. It can be done in different ways. The most simple yet effective is propably to wire two capsules, hold them as close together as possible, use a loudspeaker with random noise or music or different individual frequencies as the sound source, connect the mics to the recorder, set it to rec pause (with appropriate manual levels set) and observe the meters while moving back and forth to the loudspeaker (or fix them at a certain distance and adjust the loudspeaker's volume). If they read exactly the same in the upper range, you have found two matching capsules. If they don't, try again with different capsules. If you don't have more than two capsules available, you can skip matching and hope for the best.

Good luck.

[patcheswfb]

would it make a difference, using polarized vs nonpolarized caps? i know in speakers you have to use nonpolarized for the crossover to the tweeters, but would it make a difference in this?

thanks

[greenmachine]

Electrolytic (polarized) caps have an advantage in size and price, while other materials might be more durable. They should perform nicely for at least a few decades though. The negligibly small alternating voltage from the mics won't damage polarized capacitors.

[KrazyIvan]

Just saw this thread. Excellent! I really like the altoids tin case. I don't mind the extra bulk. I am going to have to try this!

[woulfer]

I want to thank greenmachine again for this diy. I can't believe the quality of recording that can be made with this! It has given me inspiration to take on some other electronics projects. I've got lots of books from the library, and am soldering something up almost every night.

[greenmachine]

We need to thank those who invented the electret technology. Also those who build, constantly improve them and make them available to the public at very affordable prices. I think these little panasonics are a milestone in recording quality if you know their limitations (i can't think of any other than somewhat high self-noise at the moment) and how to use them effectively.

[mrsimontibbs]

Is there an easy way to add a light that shows the existing battery power? I have a commercial 9v unit and never know whether the battery is still good or not. I don't find out my battery's dead until I hear my crappy recording. I'm thinking of building this DIY unit and that would be a handy feature. Thanks!

[greenmachine]

Is there an easy way to add a light that shows the existing battery power? I have a commercial 9v unit and never know whether the battery is still good or not. I don't find out my battery's dead until I hear my crappy recording. I'm thinking of building this DIY unit and that would be a handy feature. Thanks!

I'd rather use a multimeter or any other externel battery tester, but you can try this simple circuit. You'll need a pushbutton, two resistors and a red LED (2V). At 9V the LED will glow bright enough to be easily recognizable, at 7-8V pretty dim and from approximately 6V and below there's no indication anymore. At that point it's about time to replace the battery. Always disconnect either the microphones or the battery after use to avoid unnecessary drain. Don't use a permanent switch, which can be accidentally left in 'on' position to avoid unwanted current drain by the test circuit. If you want to use blue, white, green or any other 3V LED, you'll need different values for the resistors.

Here's an exemplary schematic:

[attachmentid=1437]

Edited February 13, 2006 by greenmachine

[woulfer]

Here's a new setup I tried Saturday. It is a set of diy mics from the tutorial. I mounted them in an aluminum tube with hot melt glue, then put some heat shrink over them.

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Then I cut some rings out of pvc, drilled some holes in them to thread elastic cord through, and mounted the mics in them as a shockmount. I then used my soldering "helping hands" and a drum clamp to rig it all to a mic stand.

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I added a song to my album from Saturday nite. I think it turned out pretty good. This diy stuff is addicting!!!

Edited February 13, 2006 by woulfer

[greenmachine]

How do you like the sound without a separator (your head) in between? From own experiments, i think it sounds a little lifeless/flat, without real dimension/depth. You could also try to experiment with a jecklin disk, dummy head or any other kind of artificial baffle. Thanks for sharing.

[woulfer]

I had planned to try to make a jecklin disc, but just ran out of time. Through speakers, I think is sounds fine. I have not yet heard it through headphones. I think I will notice the difference a lot more then. I'll report back tonight and let you know. I posted a song in the gallery, if anyone wants to check it out. I'd appreciate any comments you may have.

I really like the "battery test" circuit. It would be a nice feature for when your running out the door and don't have your multimeter handy. I really appreciate you sharing your knowledge with us!

[RockyJ]

GM,

thanks for the DIY. I just bought 4 61b's for $9 + shipping and need to get the other stuff somewhere.

These have tabs, and I believe they are there to solder to to keep the heat down. Being a rather novice, do you think I'll do any damage with my 25w iron. I doubt I'll be soldering to those tiny tabs. I've soldered to my AIWA's and did no damage and the pellets were too hot to touch!!

What d'ya think?

I've got some small heat sinks that fell off my old sound card, so I'll clamp the pellets to those to help.

Edited February 16, 2006 by RockyDisc

[greenmachine]

The more heat you apply, the shorter you have to keep the soldering time in order not to damage it. Passive cooling should lower the risk somewhat. I've also (most of the time successfully) done it with a 25W iron before i got a better suited one. The trick is to work quickly. If you don't succeed instantly, let it cool down then try again.

[RockyJ]

Do you have any suggestions on small diam shielded cable? I can't seem to find any, even at Radio Shack?

And do you know where to get those lapel clips?

[A440]

I squeeze my SoundPro BMC-2 into these. But it's a very tight fit and they have a soft housing. Greenmachine's mics might be just a tiny bit too big in diameter.

http://www.bhphotovideo.com/bnh/controller...oughType=search

Take a look at these, too:

http://www.bhphotovideo.com/bnh/controller...t.y=8&Submit=Go

You can wire a mic to the one on the bottom, with the wire running between the body of the clip and its little holder.

[RockyJ]

well I made the mic connections. I can't tell if my solder job got the cap too hot causing damage or not. How would you tell

Also I couldn't find small dia shielded cable so I settled for a radio shack special. A 6' single core with shielding sold with alligator clips as a test cable. It is almost as thick as the 6mm mics so the soldering was that much harder to see. I'm not sure if I soldered the ground where it is touching the case, but I do hear crackling when I bend the cable so I don't know where I stand on that one. Anyone know for sure what would cause the crackling when the cable is flexed?

[RockyJ]

well my first mic is rather ugly and the cabling is way too stiff, I'd say its 5mm judging from the 6mm mics. And my radio shack mini-jacks are huge and clunky. Anyway I can't find shielded cabling. Would the unshielded give me problems in a theatre setting where there shouldn't be much EM interference?

The wires for something like cheap earbuds would be just right although they may develop continuity problems.

[woulfer]

I have used the wires from cheap ($.99) headphones for all my builds, including the battery boxes, and have not had an issue yet.

[greenmachine]

A shielded cable just blocks electro magnetic fields / radio frequencies somewhat better. If you stay away from EM/RF emitters, it doesn't really make a difference. Use whatever is available. Your choice of mic capsules and mic placement will make the big difference in sound quality in the end, not the cable.

[RockyJ]

Sounds great, I figured I'd be safe in my recording environment but I'm going to try again with the cheapo (but small) wires.

Thanks for replies, I'll post again when I get these done.

[geestring]

does anyone mention the costs of making these mics and battery box?

[woulfer]

Panasonic WM-61A mic capsules were $1.89 a piece. I found some cheap headphones for a buck that I cut off the phones to use a cable. Some hot melt glue, solder, and heatshrink, and there's the mics.

For the battery box, the stereo jack and the battery are the most expensive. I'd bet you can do this project for $15 or less, depending on whether you already own some of the tools necessary (i.e. soldering iron, solder, glue gun, etc.)

[geestring]

although i dont have a lot of time... I spent $100 cdn on mics... i guess ill make the battery box...

could have saved a bunch of money.

[geestring]

all this can be found at the shack?

[woulfer]

The only thing you can't get there is the 10k ohm metal film resistors, unless you by them in a pack with a bunch of other values. All there single value resistors are carbon. But the metal film pack is only about $5, and by the time you pay for shipping from an online order, you'll pay about the same price.

[geestring]

hey i like your altoid box thing...

anyone know where i can get a tiny tin box like that? canada doesnt sella altoid candies...

[atrain]

you can buy them online for a couple of bucks, try ebay or just search google.

last time i needed some i bought high caffine penguin mints

http://www.peppermints.com/

[geestring]

sweet.. yea im going to buy a box of 10 on ebay... mmm sour cherry...

[geestring]

woulfer is it possible to make it so that no wire is sticking out of the altoid box?