Re: AOM5024 "Modded 3-Wire" Approach
Thanks, Scott, I'll take that as a "don't worry about it".
On Friday, December 29, 2023 at 09:19:59 AM CST, Scott Helmke <scott@...> wrote:
A few inches from a peacock would be considered ¡°loud¡±.? Thanks, -Scott?
Sent from a mobile device. Please excuse my brevity.?
On Dec 29, 2023, at 9:11?AM, Joe Todd <jjthaden@...> wrote:
? Stefano wrote "Unless you are recording loud things: [use] regular SP48.... As to what qualifies as "loud", if you're not sure if your sounds will be too loud, describe them and group members can weigh in."
What if the project is to record migrating birds' calls (60-90 dB at 1 meter, however, at 1,000 m) but with the capsule in the throat of a 1 meter or larger exponential horn concentrator pointed to the sky? I don't care if overflying airplanes distort, but is there any way I need to worry about a bird call being 'too loud'?
Thanks,
On Friday, December 29, 2023 at 07:14:31 AM CST, Stefano Simonelli <stefanosimonelli6@...> wrote:
Hi C,
the file you mentioned is the fruit of a tedious but interesting
work, needed to verify some options we were discussing at that
time, so no explanations, just measurements.
I totally agree with Casey, if you don't need a microphone capable
to manage very high sound pressures, the simple p48 works
magnifically (the only drawback is the lenght of the cables, they
cannot be longer than, say 15-20m). The low frequency response
depends on the value of C, as shown (and the following amplifier
input stage).
If I recall well, the "Linkwitz" mod of the PUI5024 is not as easy
as the Panasonic WM-61, but probably there is some reference in
the group files.
stefano
Il 29/12/2023 09:04, Casey via
groups.io ha scritto:
>I am talking about the low frequency response rather than the
whole
>response - but my understanding is that the graphs on Page 4
refer to "V1"
>through "V5", which are all Simple P48.
>
>On Page 6, my understanding was that it was talking about V6
(three-wire)
>and V9 (RCA).
That's correct. I was making the point that all the mics have
pretty similar responses. Note that even comparing the LF response
only, the regular SP48 is only down less than 2dB at 30Hz... I
don't know if you are recording elephant footsteps from a mile
away or something, but it's hard to imagine a scenario where
you're going to notice that, and it'd be trivial to e.q. if you
needed.
Also note that V5 of the regular SP48 which used a 5uF capacitor
has nearly equivalent bass to the JLM mod. Not sure if there are
any drawbacks to that cap size (besides physical size).
The JLM mod reduces sensitivity, and while that may not reduce SNR
on paper, in practice it could mean more noise in a recording if
the source is quiet. I built a JLM mod SP48 to mic the"kick" drum
sound in my cajon, for example - the high SPL handling was needed
to avoid distortion. But i use regular SP48 for everything else.
>and maybe it's worth saying, it
>truly is confusing how many variations and partial
explanations there are
>about something that purports to be "simple"...
The mic is simple in form, but not simple to understand (as
evidenced by the recent thread on the polarity question). It's
also a work in progress; capsules change, new things are tried,
etc. This is a DIY mic building forum, not a how-to guide, so
until someone writes up a beginner-friendly guide to all things
SP48, you'll have to expect to do some googling and consolidation
of info. Consider it the price of entry to gain access to the
eldritch wisdom.
>Essentially, I have some AOM 5024s. I'd like to use circuitry
around them
>to have the best low-frequency response, lowest noise, and
smallest part
>count - preferably nothing with additional transistors or
taking apart a
>capsule - do you have a sense of where I should be looking?
Unless you are recording loud things: regular SP48, optionally
with a 5uF cap and resistor sized according to the documentation.
As to what qualifies as "loud", if you're not sure if your sounds
will be too loud, describe them and group members can weigh in.
And for the record, "Linkwitz'ing a capsule does not require
taking it apart, just cutting and modifying a trace on the back.
--
Stefano Simonelli
|
Re: AOM5024 "Modded 3-Wire" Approach
A few inches from a peacock would be considered ¡°loud¡±.? Thanks, -Scott?
Sent from a mobile device. Please excuse my brevity.?
toggle quoted message
Show quoted text
On Dec 29, 2023, at 9:11?AM, Joe Todd <jjthaden@...> wrote:
? Stefano wrote "Unless you are recording loud things: [use] regular SP48.... As to what qualifies as "loud", if you're not sure if your sounds will be too loud, describe them and group members can weigh in."
What if the project is to record migrating birds' calls (60-90 dB at 1 meter, however, at 1,000 m) but with the capsule in the throat of a 1 meter or larger exponential horn concentrator pointed to the sky? I don't care if overflying airplanes distort, but is there any way I need to worry about a bird call being 'too loud'?
Thanks,
On Friday, December 29, 2023 at 07:14:31 AM CST, Stefano Simonelli <stefanosimonelli6@...> wrote:
Hi C,
the file you mentioned is the fruit of a tedious but interesting
work, needed to verify some options we were discussing at that
time, so no explanations, just measurements.
I totally agree with Casey, if you don't need a microphone capable
to manage very high sound pressures, the simple p48 works
magnifically (the only drawback is the lenght of the cables, they
cannot be longer than, say 15-20m). The low frequency response
depends on the value of C, as shown (and the following amplifier
input stage).
If I recall well, the "Linkwitz" mod of the PUI5024 is not as easy
as the Panasonic WM-61, but probably there is some reference in
the group files.
stefano
Il 29/12/2023 09:04, Casey via
groups.io ha scritto:
>I am talking about the low frequency response rather than the
whole
>response - but my understanding is that the graphs on Page 4
refer to "V1"
>through "V5", which are all Simple P48.
>
>On Page 6, my understanding was that it was talking about V6
(three-wire)
>and V9 (RCA).
That's correct. I was making the point that all the mics have
pretty similar responses. Note that even comparing the LF response
only, the regular SP48 is only down less than 2dB at 30Hz... I
don't know if you are recording elephant footsteps from a mile
away or something, but it's hard to imagine a scenario where
you're going to notice that, and it'd be trivial to e.q. if you
needed.
Also note that V5 of the regular SP48 which used a 5uF capacitor
has nearly equivalent bass to the JLM mod. Not sure if there are
any drawbacks to that cap size (besides physical size).
The JLM mod reduces sensitivity, and while that may not reduce SNR
on paper, in practice it could mean more noise in a recording if
the source is quiet. I built a JLM mod SP48 to mic the"kick" drum
sound in my cajon, for example - the high SPL handling was needed
to avoid distortion. But i use regular SP48 for everything else.
>and maybe it's worth saying, it
>truly is confusing how many variations and partial
explanations there are
>about something that purports to be "simple"...
The mic is simple in form, but not simple to understand (as
evidenced by the recent thread on the polarity question). It's
also a work in progress; capsules change, new things are tried,
etc. This is a DIY mic building forum, not a how-to guide, so
until someone writes up a beginner-friendly guide to all things
SP48, you'll have to expect to do some googling and consolidation
of info. Consider it the price of entry to gain access to the
eldritch wisdom.
>Essentially, I have some AOM 5024s. I'd like to use circuitry
around them
>to have the best low-frequency response, lowest noise, and
smallest part
>count - preferably nothing with additional transistors or
taking apart a
>capsule - do you have a sense of where I should be looking?
Unless you are recording loud things: regular SP48, optionally
with a 5uF cap and resistor sized according to the documentation.
As to what qualifies as "loud", if you're not sure if your sounds
will be too loud, describe them and group members can weigh in.
And for the record, "Linkwitz'ing a capsule does not require
taking it apart, just cutting and modifying a trace on the back.
--
Stefano Simonelli
|
Re: AOM5024 "Modded 3-Wire" Approach
Stefano wrote "Unless you are recording loud things: [use] regular SP48.... As to what qualifies as "loud", if you're not sure if your sounds will be too loud, describe them and group members can weigh in."
What if the project is to record migrating birds' calls (60-90 dB at 1 meter, however, at 1,000 m) but with the capsule in the throat of a 1 meter or larger exponential horn concentrator pointed to the sky? I don't care if overflying airplanes distort, but is there any way I need to worry about a bird call being 'too loud'?
Thanks,
On Friday, December 29, 2023 at 07:14:31 AM CST, Stefano Simonelli <stefanosimonelli6@...> wrote:
Hi C,
the file you mentioned is the fruit of a tedious but interesting
work, needed to verify some options we were discussing at that
time, so no explanations, just measurements.
I totally agree with Casey, if you don't need a microphone capable
to manage very high sound pressures, the simple p48 works
magnifically (the only drawback is the lenght of the cables, they
cannot be longer than, say 15-20m). The low frequency response
depends on the value of C, as shown (and the following amplifier
input stage).
If I recall well, the "Linkwitz" mod of the PUI5024 is not as easy
as the Panasonic WM-61, but probably there is some reference in
the group files.
stefano
Il 29/12/2023 09:04, Casey via
groups.io ha scritto:
>I am talking about the low frequency response rather than the
whole
>response - but my understanding is that the graphs on Page 4
refer to "V1"
>through "V5", which are all Simple P48.
>
>On Page 6, my understanding was that it was talking about V6
(three-wire)
>and V9 (RCA).
That's correct. I was making the point that all the mics have
pretty similar responses. Note that even comparing the LF response
only, the regular SP48 is only down less than 2dB at 30Hz... I
don't know if you are recording elephant footsteps from a mile
away or something, but it's hard to imagine a scenario where
you're going to notice that, and it'd be trivial to e.q. if you
needed.
Also note that V5 of the regular SP48 which used a 5uF capacitor
has nearly equivalent bass to the JLM mod. Not sure if there are
any drawbacks to that cap size (besides physical size).
The JLM mod reduces sensitivity, and while that may not reduce SNR
on paper, in practice it could mean more noise in a recording if
the source is quiet. I built a JLM mod SP48 to mic the"kick" drum
sound in my cajon, for example - the high SPL handling was needed
to avoid distortion. But i use regular SP48 for everything else.
>and maybe it's worth saying, it
>truly is confusing how many variations and partial
explanations there are
>about something that purports to be "simple"...
The mic is simple in form, but not simple to understand (as
evidenced by the recent thread on the polarity question). It's
also a work in progress; capsules change, new things are tried,
etc. This is a DIY mic building forum, not a how-to guide, so
until someone writes up a beginner-friendly guide to all things
SP48, you'll have to expect to do some googling and consolidation
of info. Consider it the price of entry to gain access to the
eldritch wisdom.
>Essentially, I have some AOM 5024s. I'd like to use circuitry
around them
>to have the best low-frequency response, lowest noise, and
smallest part
>count - preferably nothing with additional transistors or
taking apart a
>capsule - do you have a sense of where I should be looking?
Unless you are recording loud things: regular SP48, optionally
with a 5uF cap and resistor sized according to the documentation.
As to what qualifies as "loud", if you're not sure if your sounds
will be too loud, describe them and group members can weigh in.
And for the record, "Linkwitz'ing a capsule does not require
taking it apart, just cutting and modifying a trace on the back.
--
Stefano Simonelli
|
Re: AOM5024 "Modded 3-Wire" Approach
Hi C,
the file you mentioned is the fruit of a tedious but interesting
work, needed to verify some options we were discussing at that
time, so no explanations, just measurements.
I totally agree with Casey, if you don't need a microphone capable
to manage very high sound pressures, the simple p48 works
magnifically (the only drawback is the lenght of the cables, they
cannot be longer than, say 15-20m). The low frequency response
depends on the value of C, as shown (and the following amplifier
input stage).
If I recall well, the "Linkwitz" mod of the PUI5024 is not as easy
as the Panasonic WM-61, but probably there is some reference in
the group files.
stefano
Il 29/12/2023 09:04, Casey via
groups.io ha scritto:
>I am talking about the low frequency response rather than the
whole
>response - but my understanding is that the graphs on Page 4
refer to "V1"
>through "V5", which are all Simple P48.
>
>On Page 6, my understanding was that it was talking about V6
(three-wire)
>and V9 (RCA).
That's correct. I was making the point that all the mics have
pretty similar responses. Note that even comparing the LF response
only, the regular SP48 is only down less than 2dB at 30Hz... I
don't know if you are recording elephant footsteps from a mile
away or something, but it's hard to imagine a scenario where
you're going to notice that, and it'd be trivial to e.q. if you
needed.
Also note that V5 of the regular SP48 which used a 5uF capacitor
has nearly equivalent bass to the JLM mod. Not sure if there are
any drawbacks to that cap size (besides physical size).
The JLM mod reduces sensitivity, and while that may not reduce SNR
on paper, in practice it could mean more noise in a recording if
the source is quiet. I built a JLM mod SP48 to mic the"kick" drum
sound in my cajon, for example - the high SPL handling was needed
to avoid distortion. But i use regular SP48 for everything else.
>and maybe it's worth saying, it
>truly is confusing how many variations and partial
explanations there are
>about something that purports to be "simple"...
The mic is simple in form, but not simple to understand (as
evidenced by the recent thread on the polarity question). It's
also a work in progress; capsules change, new things are tried,
etc. This is a DIY mic building forum, not a how-to guide, so
until someone writes up a beginner-friendly guide to all things
SP48, you'll have to expect to do some googling and consolidation
of info. Consider it the price of entry to gain access to the
eldritch wisdom.
>Essentially, I have some AOM 5024s. I'd like to use circuitry
around them
>to have the best low-frequency response, lowest noise, and
smallest part
>count - preferably nothing with additional transistors or
taking apart a
>capsule - do you have a sense of where I should be looking?
Unless you are recording loud things: regular SP48, optionally
with a 5uF cap and resistor sized according to the documentation.
As to what qualifies as "loud", if you're not sure if your sounds
will be too loud, describe them and group members can weigh in.
And for the record, "Linkwitz'ing a capsule does not require
taking it apart, just cutting and modifying a trace on the back.
--
Stefano Simonelli
|
Re: AOM5024 "Modded 3-Wire" Approach
>I am talking about the low frequency response rather than the whole
>response - but my understanding is that the graphs on Page 4 refer to "V1"
>through "V5", which are all Simple P48.
>
>On Page 6, my understanding was that it was talking about V6 (three-wire)
>and V9 (RCA).
That's correct. I was making the point that all the mics have pretty similar responses. Note that even comparing the LF response only, the regular SP48 is only down less than 2dB at 30Hz... I don't know if you are recording elephant footsteps from a mile away or something, but it's hard to imagine a scenario where you're going to notice that, and it'd be trivial to e.q. if you needed.
Also note that V5 of the regular SP48 which used a 5uF capacitor has nearly equivalent bass to the JLM mod. Not sure if there are any drawbacks to that cap size (besides physical size).
The JLM mod reduces sensitivity, and while that may not reduce SNR on paper, in practice it could mean more noise in a recording if the source is quiet. I built a JLM mod SP48 to mic the"kick" drum sound in my cajon, for example - the high SPL handling was needed to avoid distortion. But i use regular SP48 for everything else.
>and maybe it's worth saying, it
>truly is confusing how many variations and partial explanations there are
>about something that purports to be "simple"...
The mic is simple in form, but not simple to understand (as evidenced by the recent thread on the polarity question). It's also a work in progress; capsules change, new things are tried, etc. This is a DIY mic building forum, not a how-to guide, so until someone writes up a beginner-friendly guide to all things SP48, you'll have to expect to do some googling and consolidation of info. Consider it the price of entry to gain access to the eldritch wisdom.
>Essentially, I have some AOM 5024s. I'd like to use circuitry around them
>to have the best low-frequency response, lowest noise, and smallest part
>count - preferably nothing with additional transistors or taking apart a
>capsule - do you have a sense of where I should be looking?
Unless you are recording loud things: regular SP48, optionally with a 5uF cap and resistor sized according to the documentation. As to what qualifies as "loud", if you're not sure if your sounds will be too loud, describe them and group members can weigh in.
And for the record, "Linkwitz'ing a capsule does not require taking it apart, just cutting and modifying a trace on the back.
|
Re: AOM5024 "Modded 3-Wire" Approach
Hi Casey -
I am talking about the low frequency response rather than the whole response - but my understanding is that the graphs on Page 4 refer to "V1" through "V5", which are all Simple P48.?
On Page 6, my understanding was that it was talking about V6 (three-wire) and V9 (RCA).
I could be reading this all wrong, though - and maybe it's worth saying, it truly is confusing how many variations and partial explanations there are about something that purports to be "simple"...? I don't think I ever would have figured out that "JLM" was the same thing as the three-wire approach, if you hadn't said anything.
Essentially, I have some AOM 5024s. I'd like to use circuitry around them to have the best low-frequency response, lowest noise, and smallest part count - preferably nothing with additional transistors or taking apart a capsule - do you have a sense of where I should be looking?
Make sure you are looking at the correct graph -- AFAIK the
frequency responses are about equivalent in terms of flatness.
Maybe you are confusing the low frequency section with the whole
spectrum? The graphs to compare are on page 6 (lower graph) and on
page 4 (middle graph).
The "modded 3 wires" in the Simonelli document is AKA the "Jerry
Lee Marcel" mod, JLM mod, or "Marcel mod". The SP48
doc here mentions it as well, on page 7.
The main reason for the mod is to reduce sensitivity (i.e. to
handle loud sounds better.)
To modify a 2-wire capsule, you do the "linkwitz" mod to it --
exactly how this is done depends on the capsule you are using, but
if you google for that you should be able to dig up some info. Let
me know if not. However note that you can also use a 3-wire
capsule and you don't need to mod it.
In case you still want to build the JLM variant, here are my
notes, gathered from many wise people here (sorry my notes don't
credit authors here):
The third version introduces Jerry¡¯s 2k2 between the FET
source and the capsule case. To do this, a 2 wire capsule like
WM61a must be modified to 3 wire or a 3 wire capsule like Primo
EM182 used.
This does the following :
? Gain & Sensitivity reduced by 9.3dB ie 9.3dB current
feedback
? Max. output (2.7% THD) increased by 10.6dB
? Together this increases the max. spl by 20dB for 2.7% THD to
135dB spl .. a very good spec
It also
? increases the Output Z but as this is already probably 50k, it
is of no consequence
? increases the inherent electrical noise (assuming FET,
capsule, preamp are noiseless) by about 3dB (The other noise
contribution in this supa circuit is the 2k Input Z of the
preamp).
...
JLM mod increases max SPL about 21dB, lowers sensitivity, and
with primo capsule might increase noise by about 1dB.
...
2k2 & 120k as suggested by Jerry & tested by Stefano
is certainly a good starting point for their low THD mod.?
Adjust the 120k for Vds between 5-10V
...
Will just point out that though the 2k won't degrade the noise
of WM61a (tested), the Primo EM184/172s will probably see about
1dB more noise (theoretical).
"If you do the "Marcel mod", the 2k2 MUST be AT the capsule ..
even if R1 & C1 are at the XLR.? After modifying the capsule
to insert the 2k2, you treat the assembly (which is now a 3
terminal device) like a 2 terminal capsule by ignoring the
source connection."
-c
|
Re: AOM5024 "Modded 3-Wire" Approach
Make sure you are looking at the correct graph -- AFAIK the
frequency responses are about equivalent in terms of flatness.
Maybe you are confusing the low frequency section with the whole
spectrum? The graphs to compare are on page 6 (lower graph) and on
page 4 (middle graph).
The "modded 3 wires" in the Simonelli document is AKA the "Jerry
Lee Marcel" mod, JLM mod, or "Marcel mod". The SP48
doc here mentions it as well, on page 7.
The main reason for the mod is to reduce sensitivity (i.e. to
handle loud sounds better.)
To modify a 2-wire capsule, you do the "linkwitz" mod to it --
exactly how this is done depends on the capsule you are using, but
if you google for that you should be able to dig up some info. Let
me know if not. However note that you can also use a 3-wire
capsule and you don't need to mod it.
In case you still want to build the JLM variant, here are my
notes, gathered from many wise people here (sorry my notes don't
credit authors here):
The third version introduces Jerry¡¯s 2k2 between the FET
source and the capsule case. To do this, a 2 wire capsule like
WM61a must be modified to 3 wire or a 3 wire capsule like Primo
EM182 used.
This does the following :
? Gain & Sensitivity reduced by 9.3dB ie 9.3dB current
feedback
? Max. output (2.7% THD) increased by 10.6dB
? Together this increases the max. spl by 20dB for 2.7% THD to
135dB spl .. a very good spec
It also
? increases the Output Z but as this is already probably 50k, it
is of no consequence
? increases the inherent electrical noise (assuming FET,
capsule, preamp are noiseless) by about 3dB (The other noise
contribution in this supa circuit is the 2k Input Z of the
preamp).
...
JLM mod increases max SPL about 21dB, lowers sensitivity, and
with primo capsule might increase noise by about 1dB.
...
2k2 & 120k as suggested by Jerry & tested by Stefano
is certainly a good starting point for their low THD mod.?
Adjust the 120k for Vds between 5-10V
...
Will just point out that though the 2k won't degrade the noise
of WM61a (tested), the Primo EM184/172s will probably see about
1dB more noise (theoretical).
"If you do the "Marcel mod", the 2k2 MUST be AT the capsule ..
even if R1 & C1 are at the XLR.? After modifying the capsule
to insert the 2k2, you treat the assembly (which is now a 3
terminal device) like a 2 terminal capsule by ignoring the
source connection."
-c
|
AOM5024 "Modded 3-Wire" Approach
Hi all -
I'm having a little trouble finding a simple guide to building the "modded 3-wire", though - and I'm wondering if anyone had a clear explanation or some other links to share? It seems like I have to tamper with the electret element in order to do this, so I would like to be as precise as possible.
Thanks!?
C
|
P48 Phase Testing with impulses
Jules Ryckebusch:
>I recorded a couple handclaps and snap sounds with the SimpleP48? >wired with pin3 to the capsule "+" and this is the resulting waveform.?It would seem that? pin3 to the capsule "+" is the right way to do it.Also the U87 you have is wired the same way according the test you have already done.....
Still there are a couple of no sayers.
---------
Best regards,
Goran Finnberg
The Mastering Room AB
Goteborg
Sweden
E-mail: mastering@...
Learn from the mistakes of others, you can never live long enough to
make them all yourself.??? -?? John Luther
(\__/)
(='.'=)
(")_(") Pyret, Ranglet, Aron, VovVov, Nero, Smurfen & Pussin:RIP
|
Re: SimpleP48 -- Polarity
Most of the data sheets for electret capsule show them with the FET's source grounded and the output taken from the drain, which suggests that the electret diaphragm produces a negative pulse when submited to a positive pressure.
This would be consistent with the use of negatively charged electrets.
Now it would be interesting to compare with a non-FET electret; do they reverse the carge, or are they "phased" differently, IDK.
Unfortunately, electret mfgrs keep their secrets jealously, so one can only speculate.
toggle quoted message
Show quoted text
Le 26/12/2023 ¨¤ 17:44, Scott Helmke a ¨¦crit?: [Edited Message Follows]
Since I don't think I've seen it come up yet, here's the basic FET diagram relating to polarity. With a simple two-wire connection to an electret you're getting the inverted output (also that bottom resistor probably wouldn't be there, just a direct connection to the ground terminal).
Oops - guess I still can't just dump in a picture.? I'll put it in a photo and link to that.
-Scott
|
|
|
Re: SimpleP48 -- Polarity
Since I don't think I've seen it come up yet, here's the basic FET diagram relating to polarity. With a simple two-wire connection to an electret you're getting the inverted output (also that bottom resistor probably wouldn't be there, just a direct connection to the ground terminal).
Oops - guess I still can't just dump in a picture. I'll put it in a photo and link to that.
-Scott
--
---- Scott Helmke ---- scott@... ---- (734) 604-9340 ----
"I have ceased distinguishing between the religious and the secular,
for everything is holy" - Joe Henry
|
Re: SimpleP48 -- Polarity
"Arjay, if you reverse the capsule connections in a normal ¡°true¡± condenser mic, nothing happens there, either¡¡.¡±
"I hadn't realised that... I had always assumed that if you reverse the polarity of the DC to a capsule element, you would reverse the polarity of the signal from it?¡±
From the perspective of the capsule, the polarizing voltage has been reversed, so the output signal polarity reverses. But the signal connections have also been swapped. Double reverse. To the outside world, polarity stays the same. I discovered this the same way you did. I swapped capsule leads, expecting the signal polarity to change and it didn¡¯t.
Jerry, I have seen differing descriptions of electret film and how it is made. In one case, the film is heated in a strong electrical field, and then cooled, leaving the plastic with one side having excess electrons, the other side excess holes. So it is an electret dipole, with a positive side and a negative side. I think the first electret mics used such polyester film for a diaphragm.
The other method uses an electron gun to irradiate a high-temperature insulator, usually Teflon to use the commercial name. In this case, there is no positive side, there is only a trapped cloud of electrons. A monopole. I believe this is usually preferred because of long-term stabilty. Teflon doesn¡¯t hold tension well as a diaphragm film, so it is usually put on the backplate, and Mylar is used for the diaphragm.
If you know of an article describing how electret film is applied in mics, I¡¯d appreciate more information. I¡¯m curious how the film is adhered to the backplate. Glue? Sprayed like paint or powder coat, baked, and then charged? A couple of machined brass backplates I¡¯ve looked at had some tented holes, as if a film was glued over the finished metal and not all the holes were opened afterward. Cheap electret backplates look like they were stamped from pre-coated sheet metal.
Electret film is available in industrial size rolls. For home experiments, electret film is used in some air conditioning filters, and maybe could be liberated for a home brew capsule?
I wondered what the effective ¡°polarizing voltage¡± of an electret is. After all, tiny 4mm electrets whose working capacitance would only be 3 or 4 pF are used in cell phones, and their S/N is acceptable. At the other extreme there are 34mm electrets from Transound and unidentified Chinese companies. Sensitivity isn¡¯t amazing at -40dB or thereabouts. Same as a normal K-67. Apparently, the need to increase spacing between diaphragm and backplate with diameter lowers the effective ¡°voltage¡±. Around 200V for a 6mm capsule, and 60V for 34mm.
I¡¯d like to see someone put electret film on the backplates of a K-12 or K-67. Could such a high quality capsule be built with the extra layers? It would have to be built with insulated double backplates to allow pattern switching. All of the existing electrets make the backplate connection from the middle at the back instead of the side, so back-to-back cardioid construction isn¡¯t possible. All of them use plastic acoustic filter / delay plates on the rear, and none sound like the classic 34mm capsules from AKG or Neumann.
As fixed cardioids, they sound good, with their own signatures. Worth experimenting with. I have used RK-99s on acoustic bass and pipe organ with nice results. The cheap ¡°brass covered¡± 34mm capsules are good for some vocals and I¡¯m still trying them on other stuff.
and following blog posts.
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P48 Phase Testing with impulses
I recorded a couple handclaps and snap sounds with the SimpleP48 wired with pin3 to the capsule "+" and this is the resulting waveform.?
-- Best Regards,
Jules Ryckebusch
214 399 0931
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Re: Where to buy electronics parts in the EU
thanks again all for the links and suggestions
@adrian- yes I buy from Nick at micbooster all the time, v helpful and excellent service
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Re: SimpleP48 -- Polarity
Sorry to contradict you on some points.
You cannot compare directly a standard externally polarized
capsule with an electret capsule.
First because the former is parallel-fed, while the latter is
series-fed.
Then you must consider that the traditional polarity of a true
condenser is conditioned solely by the polarity of the bias
voltage.
A positive pressure on the diaphragm results in a negative pulse
only when the bias voltage is positive.
See what happens with the rear capsule in variable pattern mics
when put in figure-8 position.
Most electret mics are built with the negative side of the
electret facing the diaphragm. A positive pressure puts the
diaphragm closer to the electret, which results in a negative
pulse. After being reverted by the FET, it results in a positive
output.
It is also consistent with the constant charge principle; when the
capacitance increases, the negative voltage impaired on
the diaphragm decreases.
Le 24/12/2023 ¨¤ 23:56, Henry Spragens
via groups.io a ¨¦crit?:
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Show quoted text
Arjay, if you reverse the capsule connections in a normal ¡°true¡± condenser mic, nothing happens there, either.
Electrets are weird. It took some experimentation for me to figure out how an electret capsule behaves. My greatest confusion is around polarity of the signal generated. Does the electret act like a constant charge on a variable capacitor, same as a ¡°true¡± condenser? Or does the effective charge vary as the diaphragm moves into and out of the electret field?
It appears the ¡°charge¡± increases as the diaphragm approaches the electret film, so this isn¡¯t a constant charge Q = CV situation, where if C goes up, V must go down. What is the voltage, anyhow? If you measure at rest, despite the constant electric field, there is no voltage between the electrodes. And what is the charge, Q? If you put a meter from diaphragm to backplate, no current will flow. Is charge zero? Thinking in these terms wasn¡¯t getting me anywhere.
That¡¯s why I think in terms of electrons migrating. We have a bunch of electrons trapped in a plastic film, which create a negative electret field around the backplate. Bring the diaphragm into the electret field, and electrons from the diaphragm will be repelled to ground, so the diaphragm acts as if it is positively charged. Bring the diaphragm closer, and the field and ¡°voltage" increases. So does the capacitance, incidentally. Both effects increase the apparent negative ¡°charge¡± on the backplate, which causes current to flow across the gate resistance of the FET, driving it negative. As the gate goes negative, the drain goes positive.
And that¡¯s how I explain it to myself. If it turns out my Neumann, Shure, and AKG mics are wired backwards, or I¡¯ve made a stupid mistake, I¡¯ll have to revise my explanation. 8^)
At least all my mics match, which is the important thing. Including Jules' OPA Alices with RK-12 capsules, which are outstanding mics, BTW.
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Re: Where to buy electronics parts in the EU
I buy my cables at Thomann. Mostly "Summer Cable" or Mogami from ebay.
Am Mo., 25. Dez. 2023 um 10:26?Uhr schrieb Ralf R Radermacher via <fotoralf= [email protected]>:
Am 25.12.23 um 09:16 schrieb underwood via :
> I buy most of my stuff at Reichelt Elektronik.
They're fine. Just stay away from their cheap cables. Two strands of
wire aren't a sufficient screening and I've had the connectors literally
fall off on several occasions.
Ralf
--
Ralf R. Radermacher? -? K?ln/Cologne, Germany
Blog? :
Audio :
Fotos :
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Re: Where to buy electronics parts in the EU
Am 25.12.23 um 09:16 schrieb underwood via groups.io: I buy most of my stuff at Reichelt Elektronik. They're fine. Just stay away from their cheap cables. Two strands of wire aren't a sufficient screening and I've had the connectors literally fall off on several occasions. Ralf -- Ralf R. Radermacher - K?ln/Cologne, Germany Blog : Audio : Fotos :
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Re: SimpleP48 -- Polarity
For as far as i know, and you said it already, the electrons are trapped in the electret, so it is impossible for them to move. So you cannot measure anything. Not by a multimeter or something like that. But there is a charge in the electret. And the charge will not change, the rule Q=VxC is not relevant, for this is not a normal capacitor consisting of 2 plates. I consider a normal capacitor as a special case of handling static electricity.
And look what is happening in the di?lektricum of a standard capacitor. This isolator acts also with opposite charges on both sides of it. Here is also no electron movement possible, the electrons in the atoms are forced to move within the atoms themselves and are able to create a bigger capacity compared to plain air. All is about static charge. We call it static, for it cannot move dynamically.
Just my 2 cents
Henry Spragens via groups.io schreef op 2023-12-24 23:56:
toggle quoted message
Show quoted text
Arjay, if you reverse the capsule connections in a normal ¡°true¡± condenser mic, nothing happens there, either.
Electrets are weird. It took some experimentation for me to figure out how an electret capsule behaves. My greatest confusion is around polarity of the signal generated. Does the electret act like a constant charge on a variable capacitor, same as a ¡°true¡± condenser? Or does the effective charge vary as the diaphragm moves into and out of the electret field?
It appears the ¡°charge¡± increases as the diaphragm approaches the electret film, so this isn¡¯t a constant charge Q = CV situation, where if C goes up, V must go down. What is the voltage, anyhow? If you measure at rest, despite the constant electric field, there is no voltage between the electrodes. And what is the charge, Q? If you put a meter from diaphragm to backplate, no current will flow. Is charge zero? Thinking in these terms wasn¡¯t getting me anywhere.
That¡¯s why I think in terms of electrons migrating. We have a bunch of electrons trapped in a plastic film, which create a negative electret field around the backplate. Bring the diaphragm into the electret field, and electrons from the diaphragm will be repelled to ground, so the diaphragm acts as if it is positively charged. Bring the diaphragm closer, and the field and ¡°voltage" increases. So does the capacitance, incidentally. Both effects increase the apparent negative ¡°charge¡± on the backplate, which causes current to flow across the gate resistance of the FET, driving it negative. As the gate goes negative, the drain goes positive.
And that¡¯s how I explain it to myself. If it turns out my Neumann, Shure, and AKG mics are wired backwards, or I¡¯ve made a stupid mistake, I¡¯ll have to revise my explanation. 8^)
At least all my mics match, which is the important thing. Including Jules' OPA Alices with RK-12 cap
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Re: Where to buy electronics parts in the EU
Conrad is very expensive. I buy most of my stuff at Reichelt Elektronik. They sometimes have PUI-Audio capsules in stock.
TME electronics is another source. I believe they are based in Poland.
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John Thaden
underwood