PRIMO Lapel Mic capsules - low noise - effects of negative phase mic output - Lapel mic placement
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- čas přidán 5. 08. 2024
- A look at four inexpensive and very low noise mic capsules (omni and cardioid ) plus introduction about the effects of negative phase audio which is output by most 'two wire' connected electret / capacitor mics and how this affects the nature of the sound. How you can flip the 'phase' to return your audio to positive phase and change its timbre. This is more noticeable when a lapel mic is high up on the chest eg nearer the second shirt button than lower down.
Also, be aware when self monitoring in headphones live that a mic that outputs a -ve phase signal will sound deeper - ie more bass - when applying bass-cut in your mixer - but the recorded sound will still have bass cut.
Have you experienced the difference in sound of a negative phase signal from a 2-wire electret microphone compared with its positive phase signal when 'inverted' ? Theoretically there should be no difference on the recording between +ve and -ve phase sound when only one microphone is in use.
FOR USEFUL TIPS ABOUT USING LAPEL MICS SEE my video for the Institute of Videography.
• Setting up Lavalier Mi...
NOTE :
The microphones were connected to a SoundDevices MixPre3 and the signal fed to a Lumix FZ2000 Bridge camera with the audio level set to -12db in the camera.
There has been no post processing of audio other than to lower handling spikes when changing foam wind/pop shields.
The Primo EM172 (omni) has a S/N ratio of 80db (ie self noise of only 14db)
The Primo EM182 (cardioid) has a S/N ratio of 78db (ie a self-noise of only 16db)
Disclosure : This is my independent review. I have purchased and used all these microphones.
Sources :
Primo mic capsules / lapel mics from (UK) micbooster.com/
Sanken Cos11x and MixPre3 purchased from Pinknoise-systems
www.pinknoise-systems.co.uk/ - Krátké a kreslené filmy
Most of the polarity flip difference you are hearing is the signal vs your own bone conducted "head voice." They will either cancel out or reinforce, the two signals, depending on the polarity in the headphones. There is less of a difference to a third party listener, or your own listening after the fact (not live, but recorded playback.) Just thought that might be added to the discussion.
Yes, that is the only explanation - important to know that listening to yourself live can give you a totally different sound - a problem if you are applying EQ. Thanks for your useful comment.
@@delcanvideoproductions4895 I could hear a difference when you swiched them.
@@fitnessboss Thanks for that confirmation. It's not just me then ! Some people can't tell - it is less evident on loudspeakers because the room scatters the sound waves. I always like to have the correct phase when editing and adjusting EQ wearing headphones in order to get the final sound I want. I was surprised that this is not a well known phenomenon.
@@chrisdelcan2757 Was waring M50s so might have been that headphones ability to pick it up better than say a phone speaker. Also this video was great exactly what I was looking for. These capsules seem like good value for the quality. Why pay $150 for a road lav mic?
Thank you for explaining and demonstrating everything so well.
Thanks for your interest. It is worth experimenting with phase reversal if you are interested in getting a nice sound.
This is a really interesting discussion on this topic as well as a great review of the Promo mic capsules. Well done Chris!
Thanks for your interest - I wish I knew the reason for the change in sound for -ve to +ve phase. You have really good audio on your videos.
@@delcanvideoproductions4895 Could the effect you're describing be due to monitoring your own voice in real-time in antiphase?
@@AronBCapable Hello Aron,. thanks for your thoughts. Yes, I think that may account for the 'live monitoring' effect but I can also hear a difference (maybe not as great) when playing back a recording where the phase is reversed - but I don't know why that should be the case. Interesting though ! Thanks for your input.
Beautiful video. You should have million views. Brilliant
Thank you for your kind remarks. Much appreciated. The differences are quite subtle but important to people wishing to get the best audio possible without spending a fortune.
Very high quality! Not the sound of the capsule (that is great too) but your content. Thank you very-very much!
Thank you for your kind comments. I hope to do a short piece comparing other lapel mics shortly.
@@chrisdelcan2757 good news! Thank you!
Great video :)
Thanks! That's a real nice explanation indeed.
Thanks Herm.
Good day. Thank you for the movie. Regards!
Yes good effort mate
Thanks Steven. I'll try to get som more content up.
I have been wanting to do some nature recording on the cheap.
I have a pair of primo inserts which i will be wiring together to boost sjgnal. Are there any easy ways to measure thr noise from your mic ?
@@stevenmcc6052 Not sue how you would make an accurate technical measurement of inherent noise from the mic capsules. I get a general idea by recording my voice at about 15 cm peaking about -6db in a very quiet and non-reverberant room and then listen to (and look at) the noise levels in iZotope RX (or you could try Audacity). If you stick to the gain levels you need for narration at 15cm then you should be fine for nature recordings. Obviously if you crank up the gain too much you will get hiss from your system but the Primo 172 capsules (now 272) at SN 80db (self noise 14dB) are about as quiet as you will get without specialist kit. Let us know how you get on.
Great video, great crystal clean low noise sound! Were the soundtracks edited?
Hi, Sorry for the delay in responding. The sound from these mics / capsules was not processed - no noise reduction applied and no EQ, so you can hear the actual sound that the mics produce. The Primo mics are incredibly low noise. Another capsules I have since found is the PUI 5024L which is very low noise (80db) and has a nice warm rounded sound if tht is what you are after. (Also try inverting the phase !!)
Inverting the polarity of a single mono sound does not create ANY change in what it sounds like.
If u have two channels that record the same sound, then you will hear a difference if u flip polarity on one of the channels and leave the other as is. That is because the waves start to cancel eachother out in different ways than before.
When I flip the phase at 2.35 there is a difference in the sound. I don't know whether that is because this mic is a 3 wire capsule wired as a 2 wire, which alters the output route on the FET amp in the capsule - but there is a difference on the recording. It is more pronounced when the mic is closer to the sound source. I have run several tests and the difference is discernible on playback, not just when self monitoring live. No real explanation for this since, as you say, phase cancellation can only occur with 2 mics on the same sound source. Thanks for your input.
It seems to me there's worthy audio going on beyond 20kHz, I'd say near 40-60kHz, extensions of lower frequencies, particularly involving metallic objects ringing and clanking about.
9:33 sounds the best to my ears but they are sound very very good.
Yes, this capsule is very good if used correctly. Thanks for your comment and interest.
Why these things are so expensive?
The differences in the signal you're hearing when inverting negative phase to positive phase, is due to FET leakage. In the common 2-wire (negative phase) configuration, incoming FET current leakage from (+V) Drain to Gate goes through the gate's high impedance and the capsule's -mV signal output (dips) are unaffected. The FET leakage in opposite direction, when the capsule outputs a high +mV signal, a small diode amount of voltage leaks out to Source and rolls off the peaks. When you invert this signal into positive phase, the dips and rolled off peaks are inverted, so the peaks become more pronounced. -Doug Ford, audio design electrical engineer, explains it a little bit at the end of EEVblog #611 Electret Microphone Design.
Hi Justin, Thanks for that. I could not figure out why flipping the -ve phase mic output produced a different more rounded and open sound, when phase reversal should not have made any difference. So this is why it changes the sound ! I'm really grateful for your explanation. Thanks.
Thanks for that - it went against everything I knew.
Not the first time, nor the last, that less-than-perfect real-life components have offered potentially useful 'flaws' !
This is complete nonsense. Flipping the phase of an audio signal does NOT change the sound AT ALL. What it will do is change how that source interacts with other mics or your perception of the sound in your headphones as you speak and the interaction with your skull. But only as you speak and listen, not playback. It will have *zero* effect on the timbre of the recorded sound itself.
Hi Andrew, Thank you for your feedback.
There are two distinct things here - one as you say, is when you listen to yourself live through headphones, where the mic sound interacts with the 'natural' sound in your head - the other is the lesser known phenomenon of a negative phase signal sounding different when you listen to the recording afterwards.
There is no obvious reason why a negative phase signal from a single microphone (with no other mics plugged in) should sound different from a normal positive phase signal when you listen on playback to the recording through headphones - but they do often sound significantly different. The negative phase output is often quite stony and harsh, whereas when flipped to positive the sound is much fuller and more rounded. I have demonstrated this many times with different mics. The difference is only noticeable when listening to the recording on headphones where the sound is being received directly and separately by your ears. There is no significant difference if you listen on monitor speakers - I suspect because the sound is bounced around the room space so is not hitting the eardrums as pure separate signals.
But why does a negative phase signal sound different on headphones ? The most likely reason is where the recording produces an asymmetrical waveform - many male voices (mine !), brass and strings often produce an asymmetrical waveform and it is probably this that accounts for the audible change in the 'tone' of the mic - although I am not sure why.
A few weeks ago I came across a users guide note from AEA about the Coles 4038 ribbon mic, which talks about capturing sound in the opposite phase from the back of the mic and that flipping the phase of the signal from an asymmetrical waveform (eg some voice, drums, bass and plucked strings) changes the sound which, it says, can't be corrected fully by EQ.
It says :
" If you change the polarity of these [asymmetrical] signals it tends to sound as if you made an EQ change. However, if you try to EQ back to the original sound, you never can get it back. Thus it is a good idea to to watch polarity in microphones, cables, electronics and speakers. "
So there is some authority on this phenomenon, which does not yet seem to be explained by sound science. At the end of the day it is what you actually hear that counts - science is only a way of trying to explain natural phenomenon.
Have a look at my more recent video covering this and listen to the sound samples on good closed back headphones. - and do some tests yourself. If you can't hear the difference it is not something you need worry about.
czcams.com/video/dx3bYoL3MZ0/video.html
Hi Andrew, We now have a useful technical explanation from Justin who says (Sept 13 2022)
Justin • 5 days ago
"The differences in the signal you're hearing when inverting negative phase to positive phase, is due to FET leakage. In the common 2-wire (negative phase) configuration, incoming FET current leakage from (+V) Drain to Gate goes through the gate's high impedance and the capsule's -mV signal output (dips) are unaffected. The FET leakage in opposite direction, when the capsule outputs a high +mV signal, a small diode amount of voltage leaks out to Source and rolls off the peaks. When you invert this signal into positive phase, the dips and rolled off peaks are inverted, so the peaks become more pronounced. -Doug Ford, audio design electrical engineer, explains it a little bit at the end of EEVblog #611 Electret Microphone Design."
if I use the em273 it s 3wire and direct into mix pre 3 from xlr ，I just connect it with xlr it will works？with out phantom 48V？or I should made a simple P48 for it？I want buy it but I don‘t konw how to connect it ……
Do not connect it to an XLR - the 48 volts will blow the capsule. It needs about 5 volts only. You could convert it to a 2 wire capsule by shorting the source to ground (as at 1'30") and then plug it in to the 3.5mm input on your MixPre3 - set up to have Aux as Mic input. (The Aux input set to Mic delivers about 5v to drive the capsule). The power and the signal will then be on the same wire - connect to the tip of the TRS). This will increase the sensitivity of the capsule by about 10db and it will reverse the phase (which you can flip to 'Invert' back to positive on the MiX Pre3 for the channel you are using). Or you could make a 48v drop down to 5v adapter if you know how to do that (Google it).
@@delcanvideoproductions4895 ok thank you
Great video, great crystal clean low noise sound! Were the soundtracks edited?
Sorry I missed this when you posted. No, there is no post processing except where I say I have flipped the phase in the edit. These mic capsules are super quiet in terms of self noise but with fairly high sensitivity for the sound you are recording.
@@delcanvideoproductions4895 Thank U!