Oktava ML-52-02 Resonance Analysis and Mod

[Michael Joly]

In an earlier thread some of us were discusing the grille resonances
of the ML52. George Reiswig sent me a sample of some lead foil-backed
limp mass material to try and use to dampen the ML52's grille.

Set up:

The ML52 I used for the tests had already been modified by cutting out
the vertical grilles and replacing them with two layers of wire mesh.
The arched grilles at the top were bonded to the underlying wire mesh
with epoxy to create a larger more stable mass with less resonance –
so the mic is not stock.

I ran a series of ML52 resonance tests by recording the output of the
mic while tapping on the mic cable with a pencil. I then burned a CD
and analyzed the results in Cool Edit.

Results:

Normal speaking level for reference: -48dB

ML52 with no felt or limp mass dampening:
Resonance: -34dB @ 238Hz
Decay Time: 280ms (100% level to 10% level)

ML52 with limp mass, felt and clamp:
Resonance: -40dB @ 230Hz
Decay Time: 155ms (100% level to 10% level)

ML52 with grille removed and replaced with wire mesh screen:
Resonance: -44dB at 280Hz
Decay Time: 29ms 100% to 10% level)

Summary:

Limp mass plus felt reduces ringing by 6dB and shortens ring time to
55% of original value. (Limp mass alone was about as effective as
felt/clamp system).

Removing the grille and replacing with wire mesh reduces ringing by
10dB and shortens ring time to 10% of original value - significantly
less noticable.

The top ring of the ML-52-02 is so highly resonant that it takes a
clasped thumb and index finger wrapped around the mic case to stop the
ringing. Simple solution – take the top off and roll your own wire
screen.

Best, MJ

[A. & G. Reiswig]

Thanks for sharing about your experiment, Mike. Good data.

George Reiswig
Song of the River Music

"Michael Joly" <mic...@electricspace.com> wrote in message
news:a884fa43.03121...@posting.google.com...

> In an earlier thread some of us were discusing the grille resonances
> of the ML52. George Reiswig sent me a sample of some lead foil-backed
> limp mass material to try and use to dampen the ML52's grille.
>
> Set up:
>
> The ML52 I used for the tests had already been modified by cutting out
> the vertical grilles and replacing them with two layers of wire mesh.
> The arched grilles at the top were bonded to the underlying wire mesh

> with epoxy to create a larger more stable mass with less resonance -

> so the mic is not stock.
>
> I ran a series of ML52 resonance tests by recording the output of the
> mic while tapping on the mic cable with a pencil. I then burned a CD
> and analyzed the results in Cool Edit.
>
> Results:
>
> Normal speaking level for reference: -48dB
>
> ML52 with no felt or limp mass dampening:
> Resonance: -34dB @ 238Hz
> Decay Time: 280ms (100% level to 10% level)
>
> ML52 with limp mass, felt and clamp:
> Resonance: -40dB @ 230Hz
> Decay Time: 155ms (100% level to 10% level)
>
> ML52 with grille removed and replaced with wire mesh screen:
> Resonance: -44dB at 280Hz
> Decay Time: 29ms 100% to 10% level)
>
> Summary:
>
> Limp mass plus felt reduces ringing by 6dB and shortens ring time to
> 55% of original value. (Limp mass alone was about as effective as
> felt/clamp system).
>
> Removing the grille and replacing with wire mesh reduces ringing by
> 10dB and shortens ring time to 10% of original value - significantly
> less noticable.
>
> The top ring of the ML-52-02 is so highly resonant that it takes a
> clasped thumb and index finger wrapped around the mic case to stop the

> ringing. Simple solution - take the top off and roll your own wire
> screen.
>
> Best, MJ