If only two mics... ?

[micolas]

I avoid to go outside in winter...

And with the sea breeze, in the summer, how do you solve it?

 

[pmfalcman]

I avoid to go outside in winter...

Understandable and wise.

It was in summer. Indoors.
Checkmate!

 

[Emmathom]

Let me go on with the PUI5024 electret project for a short while : if needed and asked for, I'll open a dedicated thread.

So first test in front of the Line Audio Omni1 and here are my first comments :

- PUI5024 has much gain, huge gain, too much gain really !!! Plugged in my (poor little) Edirol UA-EX25 USB powered the gain is almost set to 0. Let's imagine the gain pot going from 7AM (0 gain) to 7PM (full gain) : the Line Audio's gain is set at 2PM (a "normal" setting) while the PUI's one is set at 8AM !!! I must and will replace the 83KΩ resistor by 120KΩ or 150KΩ (150KΩ as I put at first time and which gave me almost the same gain as now but with gain pot set to 11AM)

- PUI5024 is much more sibilant (and that begins to raise from the mids) than LA... but with some EQ I finally get the sound very close to the Line Audio. This EQ (see attached) is a low-pass -4dB from 1800Hz

I guess this first comparative test between the two mics (spoken voice only) has been done fast just to check and does not deserve to be posted here. I'll do some voiceover + acoustic guitar recordings and post the samples asap...

 

[Emmathom]

@pmfalcman don't you have same frequency response issue with your PUI5024 ? The link you gave me leads to a discussion about the mechanical aspects, not the electronics' one nor sounding...

How does your mics sound ? what is their frequency response ?

I thought I will maybe reduce the mid-to-highs-bump by reducing the gain ? (150KΩ instead of 83KΩ which is installed now)
Anyway I've got way too much output level as it is set now.

Or maybe this (cheap capsule) has this inner default...

 

[pmfalcman]

I cannot tell, I've no means to measure the FR. Well, I do have the hardware and software for this (sort of) and could've tried my hand at it but my cats really hated it when I did the sweeps once ..
Panic at the disco, you might say.

All I can tell is that these capsules always gave me a sense of "noise". Some call it "very open", I guess. I realised after some time that this is the higher frequencies ambient sound. I always record outside, mind you. There's usually some wind, even very slight, leaves o moving, rustling. These capsules catch it all. Tiniest sounds.
Your test confirms my auditory feelings in a way.

Another thing I noticed is their rather poor resolution as compared to CM-60/63, for example.
When recording rain or wind, with Takstars I can hear droplets falling or leaves rustling. Recognisable sounds.
With 5024s I hear a kind of white noise.
Scientifically speaking: shhhhhhhh instead of pac-pac-pac-pac.

I'm much happier with my OPIC mics now (yes, yes - I know: 25 mm cardioid vs 10 mm omni capsule).

 

[k brown]

It's really hard to do better than the Promo EM273 (or 272, if you must use a 2-wire capsule), in small electret omnis that have built-in FETs.

It's the capsule that Line Audio mods for use in the Omni1.

https://micbooster.com/microphone-c..._2_4_matched_capsules-single/99-type-no_wires

 

[Emmathom]

Ok "messieurs" thank you for your answers : I would have tried... but the result is far from being unusable nor ridiculous.

I noticed something by manipulating the mic : the sound is more balanced 90° off axis than in axis. Speaking straight to the capsule (a foot away or so) brings unpleasant highs, which is strange to me for an omni mic which is supposed to take all around itself with no difference. Speaking to the mic (set vertically a foot away) but its capsule at the height of my nose instead of my chin gives far way better result....

I also noticed that the level decreases faster than Line Audio the more you move the mic away. It makes me think that this huge output level at 1 foot away could be regular with the mic set 6 or 7 feet away...

So maybe observing these two parameters (distance + capsule angle) make the mic much more usable than I think (I was hoping to use this mic as I do with Line Audio > musical acoustic ensembles live recording)

I have to do real tests in conditions, not the ones I did in a hurry at my desk while holding on the mic in my hand... I'll begin by recording some acoustic guitar in my dining room, 4 or 5 feet away, hand claps, singing, etc... with the Line Audio on a second track.

To @k brown : I could be interested in building the same kind of DIY mic but with the Primo EM273 and I suppose I can refer to Ulli's circuitry... ? For EM272 I guess the circuitry is much simple... as it is for the PUI5024

 

[Emmathom]

Another test with acoustic guitar 6 feet from mics, Line Audio & PUI5024 side by side.

- PUI5024's output level does not decrease the further you go (so I really need to dim that)
- PUI needs indeed to have its capsule pointed up, not to the source, otherwise some unpleasant highs appear
- PUI needs an EQ but less pronounced than I first did

Set as above, the PUI5024 becomes usable and delivers a pleasant sound, different from Line Audio but with its own character. A slight more bright, a slight less mids... (need to play a bit with EQ)

I will put them aside the Line Audio next time I record a real ensemble in a real acoustic and then I'll be able to have an real opinion...

Last circuit attached (much more "normal" about output level)

 

[micolas]

Another test with acoustic guitar 6 feet from mics, Line Audio & PUI5024 side by side.

- PUI5024's output level does not decrease the further you go (so I really need to dim that)
- PUI needs indeed to have its capsule pointed up, not to the source, otherwise some unpleasant highs appear
- PUI needs an EQ but less pronounced than I first did

Set as above, the PUI5024 becomes usable and delivers a pleasant sound, different from Line Audio but with its own character. A slight more bright, a slight less mids... (need to play a bit with EQ)

I will put them aside the Line Audio next time I record a real ensemble in a real acoustic and then I'll be able to have an real opinion...

Last circuit attached (much more "normal" about output level)

Hi @Emmathom!
How would you compare the SNR between the two microphones in real conditions, in your applications?

 

[Emmathom]

Hi @Emmathom!
How would you compare the SNR between the two microphones in real conditions, in your applications?

It would need real measurements but I haven't got the tools for that...
Just by listening I'd say no more noise than Line Audio with same recording levels but as I said the gain is set higher on the Line Audio (to get the same recording level). 10AM for PUI / 2PM for LA. On a log pot that's not so much but thanks to the 150K resistor (much more "normal" output level than with the 83K)

 

[micolas]

It would need real measurements but I haven't got the tools for that...
Just by listening I'd say no more noise than Line Audio with same recording levels but as I said the gain is set higher on the Line Audio (to get the same recording level). 10AM for PUI / 2PM for LA. On a log pot that's not so much but thanks to the 150K resistor (much more "normal" output level than with the 83K)

Philippe, Thanks for the info!
(I used to have fun with this type of simple circuit in the 80s, I used to extract electret capsules from Japanese radio cassette players, I also built lathed aluminum bodies and experimented with different headbaskets, I even incorporated a simple passive EQ that lowered the level but it was ok, they had a high output level, they sounded better than dynamic microphones: Soviet or Philips, Unitra etc )

 

[Emmathom]

Philippe, Thanks for the info!
(I used to have fun with this type of simple circuit in the 80s, I used to extract electret capsules from Japanese radio cassette players, I also built lathed aluminum bodies and experimented with different headbaskets, I even incorporated a simple passive EQ that lowered the level but it was ok, they had a high output level, they sounded better than dynamic microphones: Soviet or Philips, Unitra etc )

Yes I thought about inserting an passive EQ in... but let's do it in post for it gives more latitude...

 

[Cqwet Dbdfte]

There are more things that can go wrong with a 2/3 Mike setup, maybe why not used much for bigger bands.
It would also record the effects of the acoustic space, wich can make the sound more "real", at least for non-electronic sources.
I would think this way would be more challenging, but I appreciate the the effort.

 

[ricardo]

I could be interested in building the same kind of DIY mic but with the Primo EM273 and I suppose I can refer to Ulli's circuitry... ? For EM272 I guess the circuitry is much simple... as it is for the PUI5024

EM273 is a 3 terminal electret so ideally suited for SimpleP48RCA. No need to modify the capsule

This has 10dB less gain, 10dB less distortion and a max. spl of 130dB or better

 

[micolas]

EM273 is a 3 terminal electret so ideally suited for SimpleP48RCA. No need to modify the capsule

This has 10dB less gain, 10dB less distortion and a max. spl of 130dB or better

+1
Excellent capsule!
And let's mention a very good S/N ratio for this class of capsules

 

[MicUlli]

I would like to drive your attention back towards the intention of this thread: Only two mics.
After some recordings with superlux S502MKII equipped with my "repair kit" i could imagine to buy a 2nd one and modify it. Then i have "two mics", but 4 cardioid capsules. The next step would be a modification of two of the capsules towards omni polar pattern. If this works out as feasible the work is done. With this equipment i can configure

ORTF (2 cardioids, 17cm, 110°, trivial)
Sengpiel (2 cardioids 25cm, 90°, combining the two S502MKII)
NOS (2 cardioids, 30cm, 90°, combining the two S502MKII)
AB (2 omnis, 30..70cm, angle as you wish, combining the two S502MKII)
With some mixing you can produce almost all configurations on a "single microphone stand".

1st step to modify a cardioid to an omni is to close the vents. I am sure this will produce a terrible frequency response, but perhaps it can be equalized.
If this should not work satisfying i will open one capsule and modify the inner parts appropriately.

It will take some time because actually i have to work on an NDIR sensor project. Stay tuned..

BR MicUlli

 

[Emmathom]

For example the Shure KSM141 has a ring you turn to switch from cardio to omni : I don't know what - exactly - does the ring... It (surely) closes the vents and maybe add an EQ or some circuit : do someone knows how it works ?

@Khron had opened a thread about this mic (which was out-of-order)
https://groupdiy.com/threads/shure-ksm27-ksm141-circuitry.61079/

Sorry if it's out of topic but I thought knowing how this KSM141 works could help for @MicUlli's idea...
(BTW this mic is very appreciated - as a lot of Shure products, like the KSM44 for example)

 

[Khron]

It (surely) closes the vents and maybe add an EQ or some circuit : do someone knows how it works ?

It closes the vents, but that's it, it does nothing electrical. The circuits of the KSM141 and KSM27 are identical (apart from the bias voltage generator in the 27 since it's not an electret), and there's no frequency manipulation going on in either (apart from the switchable low-cut, of course).

 

[Emmathom]

It closes the vents, but that's it, it does nothing electrical. The circuits of the KSM141 and KSM27 are identical (apart from the bias voltage generator in the 27 since it's not an electret), and there's no frequency manipulation going on in either (apart from the switchable low-cut, of course).

Hum... many users and mic designers according to say that closing the vents only does not make a cardio into omni... but if you say so and if Shure does so (it's then easier for Ulli)
But the Shure's mechanical part for that must be a bit sophisticated since it's very discreet from outside (good job)

 

[Emmathom]

ORTF (2 cardioids, 17cm, 110°, trivial)
Sengpiel (2 cardioids 25cm, 90°, combining the two S502MKII)
NOS (2 cardioids, 30cm, 90°, combining the two S502MKII)
AB (2 omnis, 30..70cm, angle as you wish, combining the two S502MKII)
With some mixing you can produce almost all configurations on a "single microphone stand".

Hi Ulli
If you have a "drawing software" could you please draw how you set your 2 ORTF mics ? Or you mean that some configurations use only one the two capsules of each ORTF mic ?