Topic: LCF (Low Cut Filter)/bass rolloff on the Sony PCM-M10

[jj69]

I contacted Sony Support to figure out exactly where the PCM-M10's Low Cut Filter rolls off the bass.  Here's the answer I got:

"Lo cut filter frequency starts at 200Hz, 24dB/Octave filter, effects both Mic and Line input"

200 Hz seems pretty high, but I'm wondering what the 24dB/Octave filter means.  Perhaps one of you more tech minded members can explain it to me?  Does it maybe mean that although it starts at 200 Hz, it's a gentle roll off curve? 

I've used it for several shows and it doesn't seem much more severe than the 80 Hz rolloff on my Tascam. 

Also, for anyone who is interested, the LCF filter, when switched on, functions through both the LINE IN and the MIC input.  This is super handy when your mics/batt box don't have a any built-in bass rolloff. 

[aaronji]

I think the "24 dB/octave" means that for every halving of the frequency (i.e. one octave decrease), starting at 200 Hz, the signal will be decreased by 24 dB.  So at 100 Hz, down 24 dB.  At 50 Hz, down another 24 dB.  Pretty drastic low-cut; often it's 6 or 12 dB per octave...

[jj69]

Okay.  Thanks for the explanation.  I'm surprised to hear that, because in actual use it does not seem very severe at all. 

I have a battery box with adjustable bass roll off on the way, so it will be interesting to make some comparisons. 

[DSatz]

I just got an M10 today. It looks to me as if what you were told is about right. Relative to 1 kHz, the -3 dB point with the filter turned on is at 200 Hz, and it's 24 dB down at 100 Hz and 48.4 dB down at 50, and continuing below there. This was measured through the line input, using the analog line output.

Wow! That is one steep filter.

[cashandkerouac]

the LCF on the M-10 is not a very useful tool in my opinion.  the limiter is also pretty useless.  however, it's a great little machine at an excellent price. 

[LikeASong]

Not exactly related to this, but now that we're at low-cuts and stuff... What do you think it's better (pressuming identical dB/octave settings): using the preamp/battery box low-cut switch or the recorder's one? I would always bet on the preamp/bb, but I would like to hear some more opinions. Thanks!

[Lostbrook]

I don't plan to use the M10 LCF anymore.  I don't like what it did to my Smashing Pumpkins recording.  Of course, the sound sucked at the Patriot Center anyway.

[F.O.Bean]

ALWAYS do the LFC/HPF in POST PRODUCTION!!!!

[justink]

ALWAYS do the LFC/HPF in POST PRODUCTION!!!!

[DSatz]

To me it depends on why the filter is wanted in the first place. If its purpose is protect against wind noise, then use it as early in the chain as possible, because low-frequency energy from wind noise can overload the input of a microphone's own electronics, let alone a preamp or recorder that the microphone is attached to.

But if there's no imminent danger to the recording and the purpose of the low-end cut is to improve the sound of an otherwise OK recording, then I agree with the previous two posters: Make all possible adjustments at home or in your studio while listening to good loudspeakers that you're familiar with. Otherwise you won't know how much to cut or at what frequency. The big risk is of making a larger adjustment than necessary.

--best regards

[Church-Audio]

One of these days companies will make it adjustable. Its all in the dsp anyway pretty easy to do for the most part. Unless they are using actual circuitry for the filter ouch.

[ArchivalAudio]

ALWAYS do the LFC/HPF in POST PRODUCTION!!!!

exactly - you can always remove but never add...

[Church-Audio]

ALWAYS do the LFC/HPF in POST PRODUCTION!!!!

exactly - you can always remove but never add...

Very true.