[Gareth Magennis[_3_]]

Hi,

I have a possibly faulty one of these for repair, but it might not be
faulty.
http://www.akg.com/pro/p/c414-b-xls

You might not believe the amount of SMD circuitry inside this thing - I have
a photo I could post.


Anyway, my aural observation is that the front capsule (silver grille) is
quite different to the back (black grille).

I have determined that the back capsule has a lot more proximity effect than
the front. Other than that, the mic sounds faultless.

Speak up very close to both capsules in fig8 or Omni, and they are the same.
Back away 50cm or so and beyond, and the back capsule loses a lot of bass
the front capsule doesn't.

This doesn't seem quite right to me, but I don't have anything to A/B it
with, and I can't think of a fault that would do that.
I have heard significant discrepancies in the past with double capsules
sounding different to each other, but this just seems one step beyond that.

Is anyone able to say whether this is how these mics are or not?


I should add:
The owner brought this mic to repair because it suffered a major Big Bang,
then apparently lost gain, intermittently. I am trying to establish whether
he may have mistaken the above apparent anomaly for evidence the Big Bang
broke the mic, when in fact the Mic was always like this, and he had some
kind of local phantom power/cabling problem.
He seems pretty switched on to me, but we can all be fooled some time.




Cheers,


Gareth.

[Gareth Magennis[_3_]]

What IS all that stuff?

http://tinypic.com/r/ouyz9c/9




Gareth.

[Mike Rivers[_2_]]

On 9/14/2016 4:07 PM, Gareth Magennis wrote:
What IS all that stuff?

It's where they put the magic smoke that makes it work.

Try making a test recording up close and at a distance from the front
and rear capsules when in figure 8 mode. Also, see how good the null is
by speaking into the side of the mic from about 6 inches away. It should
be pretty deep and pretty similar on both sides.

Many of those magic smoke containers switch the polarization voltage on
the capsules to create the polar patterns, and I expect there's a lot of
frequency response shaping (electronic filters) to get the frequency
response they want. But, yeah, it really looks complicated.


--

For a good time, call http://mikeriversaudio.wordpress.com

[Scott Dorsey]

Gareth Magennis wrote:
I have a possibly faulty one of these for repair, but it might not be
faulty.
http://www.akg.com/pro/p/c414-b-xls

You might not believe the amount of SMD circuitry inside this thing - I have
a photo I could post.

Oh, I sure would.

Anyway, my aural observation is that the front capsule (silver grille) is
quite different to the back (black grille).

I have determined that the back capsule has a lot more proximity effect than
the front. Other than that, the mic sounds faultless.

There's only one capsule in there.

Speak up very close to both capsules in fig8 or Omni, and they are the same.
Back away 50cm or so and beyond, and the back capsule loses a lot of bass
the front capsule doesn't.

That's because it's directional at low frequencies. You'll notice the top
end also changes a lot with direction in omni mode. The omni isn't very
omni at all.

This doesn't seem quite right to me, but I don't have anything to A/B it
with, and I can't think of a fault that would do that.
I have heard significant discrepancies in the past with double capsules
sounding different to each other, but this just seems one step beyond that.

Is anyone able to say whether this is how these mics are or not?

If you want an omni that is actually an omni, or a figure-8 that is symmetric,
this is likely not the microphone for you. I think what you are hearing is
normal behaviour.

I should add:
The owner brought this mic to repair because it suffered a major Big Bang,
then apparently lost gain, intermittently. I am trying to establish whether
he may have mistaken the above apparent anomaly for evidence the Big Bang
broke the mic, when in fact the Mic was always like this, and he had some
kind of local phantom power/cabling problem.
He seems pretty switched on to me, but we can all be fooled some time.

I'd send it in to AKG and just have them give it a once-over. It won't
hurt to have them check it and it will give everyone involved peace of
mind. They used to be very cheap and sometimes didn't even charge for
this sort of thing although under the new regime a lot of things are
different.

If there IS an electronics problem on an XLS, I wouldn't touch it. There
is just too much crap inside there, and most of it really has no business
being in there.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Phil Allison[_4_]]

gareth magennis wrote:



Anyway, my aural observation is that the front capsule (silver grille) is
quite different to the back (black grille).

I have determined that the back capsule has a lot more proximity effect than
the front. Other than that, the mic sounds faultless.

Speak up very close to both capsules in fig8 or Omni, and they are the same.
Back away 50cm or so and beyond, and the back capsule loses a lot of bass
the front capsule doesn't.



** How are you monitoring the sound of the mic ?

With headphones on and using your own voice ?

Although used by lotsa folk, doing this has a major traps stemming from possible phase and time delay issues between the sound arriving from the headphones and your voice being transferred direct through your head to your ears.

If you have a phase switch somewhere, you will hear significant differences in low frequency response when the switch is operated depending on how close the mic is when speaking.

Note: figure 8 mics have reverse phase when approached from the rear - so back & front will normally sound different when using the above method.

These traps are avoided if you use another sound source, rather than your own voice.



..... Phil

[Phil Allison[_4_]]

gareth magennis wrote:

What IS all that stuff?

http://tinypic.com/r/ouyz9c/9



** Resistors, capacitors, transistors, op-amps ....

Oh, and the one with all the legs is a TI "ultra low power" microcontroller.



..... Phil

[gareth magennis]

On Thursday, September 15, 2016 at 4:04:09 AM UTC+1, Phil Allison wrote:
gareth magennis wrote:



Anyway, my aural observation is that the front capsule (silver grille) is
quite different to the back (black grille).

I have determined that the back capsule has a lot more proximity effect than
the front. Other than that, the mic sounds faultless.

Speak up very close to both capsules in fig8 or Omni, and they are the same.
Back away 50cm or so and beyond, and the back capsule loses a lot of bass
the front capsule doesn't.



** How are you monitoring the sound of the mic ?

With headphones on and using your own voice ?

Although used by lotsa folk, doing this has a major traps stemming from possible phase and time delay issues between the sound arriving from the headphones and your voice being transferred direct through your head to your ears.

If you have a phase switch somewhere, you will hear significant differences in low frequency response when the switch is operated depending on how close the mic is when speaking.

Note: figure 8 mics have reverse phase when approached from the rear - so back & front will normally sound different when using the above method.

These traps are avoided if you use another sound source, rather than your own voice.



.... Phil




Blimey Phil, you're right. How have I not noticed that before?
This is well extreme.

Scratches head and blushes a bit ....



Cheers,


Gareth.

[Mike Rivers[_2_]]

On 9/14/2016 11:04 PM, Phil Allison wrote:
** How are you monitoring the sound of the mic ?

With headphones on and using your own voice ?

Although used by lotsa folk, doing this has a major traps stemming
from possible phase and time delay issues between the sound arriving
from the headphones and your voice being transferred direct through
your head to your ears.

If you have a phase switch somewhere, you will hear significant
differences in low frequency response when the switch is operated
depending on how close the mic is when speaking.


Good catch. I suggested that he check the mic by making a test recording
outdoors.

I ignore people at trade shows who hand me headphones and say "check out
this new vocal mic." And when setting up a headphone mix for a singer,
if he doesn't like the sound of his voice in the headphones, usually
switching the polarity of the mic signal at the preamp fixes it.

And if the mic has its own track, if it doesn't sound right in the mix,
you can always flip the polarity back to where it was originally. With
some voices and instruments, you can hear a difference when switching
polarity, but that's for a different reason than what you brought up here.


--

For a good time, call http://mikeriversaudio.wordpress.com

[Phil Allison[_4_]]

gareth magennis wrote:




** How are you monitoring the sound of the mic ?

With headphones on and using your own voice ?

Although used by lotsa folk, doing this has a major traps stemming from possible phase and time delay issues between the sound arriving from the headphones and your voice being transferred direct through your head to your ears.

If you have a phase switch somewhere, you will hear significant differences in low frequency response when the switch is operated depending on how close the mic is when speaking.

Note: figure 8 mics have reverse phase when approached from the rear - so back & front will normally sound different when using the above method.

These traps are avoided if you use another sound source, rather than your own voice.




Blimey Phil, you're right. How have I not noticed that before?
This is well extreme.

Scratches head and blushes a bit ....



** Thanks for the confirmation - I was pretty sure I knew what you had done wrong.



..... Phil

[Scott Dorsey]

In article ,
Phil Allison wrote:
gareth magennis wrote:

What IS all that stuff?

http://tinypic.com/r/ouyz9c/9


Oh, and the one with all the legs is a TI "ultra low power" microcontroller.

And that is where it gets scary, because that thing is basically being used
for pattern control because it's cheaper than a reliable mechanical switch with
silver contacts.

The evolution of the 414 has been an ever-increasing attempt to cut costs in
every possible way, beginning with the discontinuation of the 414EB....
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

gareth magennis wrote:


Blimey Phil, you're right. How have I not noticed that before?
This is well extreme.

I thought you said you heard it in omni mode too, though. The low end won't
change from front to back in omni mode because it'll have the same polarity
phase both in front and in back.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[gareth magennis]

On Thursday, September 15, 2016 at 2:26:09 PM UTC+1, Scott Dorsey wrote:
gareth magennis wrote:


Blimey Phil, you're right. How have I not noticed that before?
This is well extreme.

I thought you said you heard it in omni mode too, though. The low end won't
change from front to back in omni mode because it'll have the same polarity
phase both in front and in back.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."


Thanks, Scott,
just been back and checked the Omni mode, and yes it is wholly consistent.

Which has just pinged my head as to what I think happened.


There WAS a level inconsitency between both sides of the capsule as reported by the customer, AS WELL as the bass in my head cancellation in fig8. I remember hearing it in Omni. Omni was definitely goosed, it isn't now.

So, this level problem has dissapeared now I've dismantled the mic, took the photo, and reassembled it, but leaving the bass cancellation anomaly, which I mistakenly thought was a misinterpreted loss of gain.


Cheers,


Gareth.