Want to make my own headset microphone, which capsule do I need? - Page 1
Forum section: electronics / beginners

author: josephpate
author_rank: Contributor
timestamp: February 01, 2017, 12:55:53 am
content: I've modified my headphones to have a ~3inch long cable with a female 3.5mm jack. This way I can use a male-to-male 3.5mm patch cord in any length that I want. The jack itself is very close to my mouth, so I had the idea to add an in-line poseable boom mic in case I ever wanted to record with them.There are lots of these on amazon, but they are all designed assuming you're going to add them to the end of a normal pair of headphones, not in-line like I would need it to be.Rather than modifying an existing product, I thought it'd be pretty simple to create my own. All I would need is a small capsule mic, and some stiff/poseable wire, and some as-yet-to-be-determined connector to put it in-line with my headphones.Looking around for a mic capsule, though, all I can find are condenser mics, which I believe require a small voltage to work. Is this the case? If so, do phones/PCs/tables/whatever supply the needed voltage through the headphones that built-in mics use? If not, do they make small dynamic mic capsules?For reference, these are the types of capsules I'm talking about:https://smile.amazon.com/uxcell-Capsule-Electret-Condenser-Microphones/dp/B00AUB8NPS/ref=sr_1_1?ie=UTF8&qid=1485906901&sr=8-1&keywords=electret

author: Buriedcode
author_rank: Super Contributor
timestamp: February 01, 2017, 10:56:29 am
content: Almost all commercial 'PC headsets' use small diaphragm electret mics, that have a built-in FET and so, do indeed require power. However, the standard hookup is feeding 1.5-9V via a resistor, with a cap for the output. This configuration can add noise and produce a non-linear response, but those are only really of concern for 'studio quality' recording, or measurement mics - the simplicity and gain is ideal for voice quality.Most cheap elecret capsules are omnidirectional, and sound surprisingly good for general recording or nature sounds, but for a headset mic where you probably don't want to pick up much ambient sound, a unidirectional or 'noise cancelling' capsule should be used.QuoteThey do indeed require a small voltage, however, almost all PC soundcards (or on-board sound) provides a small voltage bias and are specifically designed to work with these little elecrets. I suspect you could get away with just using a screened cable for the two connections straight to a 3.5mm jack, as that is how most headsets are connected. Note almost all mic inputs these days on PC's are stereo.. so you could connect the mic to both left and right, but it is often just to the left channel - the tip of the connector. If you don't know which terminal on the mic is 'signal' and which is 'ground', the ground is usually connected to the housing via a small trace on the back. Another easy check would be to wire it however you want, and, when listening to it from your soundcard, if it hums when you touch the metal capsule, you've got it wired the wrong way aroundSome elecrets have 3 terminals, that provide access to the source and drain of the FET, as well as ground (negative side of the mic element, and housing). This is more versatile, but only needed for different configurations where accurate measurement of SPL (sound pressure level). The standard two-terminal types are by far easier to work with, requiring no circuitry if they are to be plugged into a PC/laptop/tablet/phone.There are some dynamic mic capsules, but they are rarely small. For karaoke type quality (which isn't all that bad!) they are generally about an inch/25mm in diameter and an inch deep. Smaller dynamic mic capsules tend to have significant bass roll-off -> they can sound very tinny. Where-as even the subminiature 6mm elecret mics can easy pick up 30Hz-18kHz.In summary, the capsules you linked will be fine. Screened cable to a 3.5mm plug and you're good to go. If you can find uni-directional, or 'noise cancelling' electrets then these will be better for a headset application, but omni's will work just find - especially since its so close to the user, so the gain will be low enough that it doesn't pick up much in the way of ambient sounds.

author: josephpate
author_rank: Contributor
timestamp: February 01, 2017, 02:02:38 pm
content: I see. Interesting. So do phones supply a bias voltage to those cheap crappy microphones built into earphones? If not, what powers those? If I want to use this with a phone too, would it need is own power supply?Also, would shielded cable be necessary since the whole thing will only be three inches long? I already have some stiff wire that I want to use since it's already poseable.

author: joseph nicholas
author_rank: Frequent Contributor
timestamp: February 01, 2017, 02:06:41 pm
content: The answer to the question above is yes. But the bigger question what is it. And what is the value when you apply the "boost" value.

author: Buriedcode
author_rank: Super Contributor
timestamp: February 01, 2017, 09:58:15 pm
content: Phones usually have a 4-pole TRS connector, ground, L, R, and mic, and will provide the bias the mic needs, so.. does it require its own power when using for a phone ? no. Will it require a different connector? yesPC's generally have stereo 3-pole TRS connectors, since there is room to for other connections like mic and line-in to have their own separate connectors.

author: josephpate
author_rank: Contributor
timestamp: February 01, 2017, 10:37:53 pm
content: Hmmm I was gonna use a TRRS anyway, guess if I want to connect it to a PC i'll have to make a splitter. Thanks for the info.

author: Audioguru
author_rank: Super Contributor
timestamp: February 02, 2017, 12:58:56 am
content: The Amazon mic capsules are so cheap that there is probably something wrong with them. A manufacturer's rejects, sweepings from the floor. I would buy a trustworthy name-brand mic from Digikey.A headset boom mic is near your mouth so its preamp gain will be low, then background noise will also be low. If you move a noise-cancelling mic a tiny distance then your voice will be cancelled.

author: Richard Crowley
author_rank: Super Contributor
timestamp: February 02, 2017, 01:43:33 am
content: Those small "jelly-bean" electret mic capsules are made by the millions. It is unlikely there is anything "wrong" with those capsules on the Amazon web page. They are available everywhere for retail prices around US$1 or significantly less. They are the kind of microphones used in most communication devices on this planet. That is why they are so incredibly inexpensive.Certainly, all modern phones, computers, tablets, etc. provide "plug-in power" for those Electret Condenser Microphone (ECM) capsules. If you study the interface to the TRRS 3.5mm connectors on these devices, you will find one of these two "standard" pinouts:Using one of those small ECM capsules isdrop-dead simple. Connect the ECM (with the proper polarity, of course) to ground and the microphone ring of the connector.If I weren't just making it myself, I would get one of these to accomplish joining the microphone boom to the headphone connection.

author: josephpate
author_rank: Contributor
timestamp: February 02, 2017, 02:49:41 am
content: Thanks for the info. I've done a bit of hacking with several pairs of headphones so I think I have a pretty good grasp of the connectors.If the TRRS plug and the headphone jack were gender-swapped that'd be the exact doohickey I need to hook this all together when I make my boom (I decided to use a female jack on my headphones for some reason, and I don't really want to modify them again).