general question! -ACID Product Family - MAGIX Community Forums Archive

Subject:general question! Posted by: SkZ Date:6/12/2003 1:04:43 PM Why when using EQ(on the master) then cutting all frequencies below 60hz and also having a spectral analyzer next in-line (on the master)Why do frequencies still appear on the graph of the spectral analyzer below 60hz ? shouldn't these be cut?
Subject:RE: general question! Reply by: spesimen Date:6/12/2003 1:36:06 PM which eq are you using? the sf one? when you do a 'cut' with that eq with the low shelf, it's not to infinity, it's just to the depth that the filter supports at that freq. so you're probably cutting like 12db at 60hz and then becase of the curve, something like 24db at 30hz, etc. to truly remove, rather than just attenuate, all those low freqs you need something more specific to that purpose than a low-shelf filter. if i remember correctly, cool edit pro has some super-steep filtering algorithms that can do this, but i've not really seen ones that steep in real-time eq's anywhere. in practice i'm not sure there's really a need for it since if you need to cut or boost by more than 12db in a signal it's either for a very specialized purpose or because you probably just need to re-track the sound..
Subject:RE: general question! Reply by: chaircrusher Date:6/13/2003 12:12:11 AM A) as spesimen said, a lowpass at 60hz falls off at a certain number of dB per Octave, meaning that it will leave some low frequency content below 60hz B) All or most of the spectral analysis algorithms use bandpass filters which also roll off gradually at the edges of the pass band. Thus, even if you really don't have significant output below 60 hz, the bar for the 60hz band is still going to register sound energy above 60 hz.

Subject:general question!

Posted by: SkZ

Date:6/12/2003 1:04:43 PM

Why when using EQ(on the master) then cutting all frequencies below 60hz and also having a spectral analyzer next in-line (on the master)Why do frequencies still appear on the graph of the spectral analyzer below 60hz ?

shouldn't these be cut?

Subject:RE: general question!

Reply by: spesimen

Date:6/12/2003 1:36:06 PM

which eq are you using? the sf one?
when you do a 'cut' with that eq with the low shelf, it's not to infinity, it's just to the depth that the filter supports at that freq. so you're probably cutting like 12db at 60hz and then becase of the curve, something like 24db at 30hz, etc.
to truly remove, rather than just attenuate, all those low freqs you need something more specific to that purpose than a low-shelf filter. if i remember correctly, cool edit pro has some super-steep filtering algorithms that can do this, but i've not really seen ones that steep in real-time eq's anywhere. in practice i'm not sure there's really a need for it since if you need to cut or boost by more than 12db in a signal it's either for a very specialized purpose or because you probably just need to re-track the sound..

Subject:RE: general question!

Reply by: chaircrusher

Date:6/13/2003 12:12:11 AM

A) as spesimen said, a lowpass at 60hz falls off at a certain number of dB per Octave, meaning that it will leave some low frequency content below 60hz

B) All or most of the spectral analysis algorithms use bandpass filters which also roll off gradually at the edges of the pass band. Thus, even if you really don't have significant output below 60 hz, the bar for the 60hz band is still going to register sound energy above 60 hz.