Can you restore Frequencies that have already been EQ'd?

[vanq]

After you EQ something and export it into a Wav file, is it possible for someone else to open that file and use EQ to get back the frequencies you cut out? And return it to its original sound before it was messed with?

So say I completely cut out all the low and mid frequencies on a snare leaving only the High range, then export it. Could someone else then open it back up with their own program and use EQ to get back those Mid and Low Frequencies I cut out? Or would it never really sound like the original again?

 

[krushing]

Not really possible, at least if they're truly cut out instead of being heavily attenuated. And even in the latter case it's not a simple case of "hey I'll just turn these back up".

 

[chris carter]

Yes and no. If you are just talking about boosting and cutting certain frequencies, then generally speaking you can get back to where you started. It might not be EXACT, but it should be pretty darn close (typically close enough that you can't tell in the mix). The reason it won't be exact is because different EQs have different curves and characteristics. And even if you used the exact same EQ, many have a different curve or Q boosting vs. cutting.

Now, on the other hand, if you ELIMINATE frequencies, then it can be extremely difficult. For example, if you hi-pass an instrument at 500Hz with a 12dB/oct filter, then by the time you get down to 125Hz there's really almost nothing there to boost to get back the sound. You can get some of it back, but there will be limits - and at a certain point you will just bring up muck. I've been in this situation plenty of times where a beatmaker went to heavy on a HPF or a LPF (usually the LPF) and I'm cranking +20 to get something back and at a certain point you are just boosting too much hiss in the sound.

 

[Synapsis]

Yes and no. If you are just talking about boosting and cutting certain frequencies, then generally speaking you can get back to where you started. It might not be EXACT, but it should be pretty darn close (typically close enough that you can't tell in the mix). The reason it won't be exact is because different EQs have different curves and characteristics. And even if you used the exact same EQ, many have a different curve or Q boosting vs. cutting.

Now, on the other hand, if you ELIMINATE frequencies, then it can be extremely difficult. For example, if you hi-pass an instrument at 500Hz with a 12dB/oct filter, then by the time you get down to 125Hz there's really almost nothing there to boost to get back the sound. You can get some of it back, but there will be limits - and at a certain point you will just bring up muck. I've been in this situation plenty of times where a beatmaker went to heavy on a HPF or a LPF (usually the LPF) and I'm cranking +20 to get something back and at a certain point you are just boosting too much hiss in the sound.

um.... the more EQ you apply, the more phase distortion is entered.... Once something has been cut, it is gone... it has also left a little phase warble to the sound... so if you want to re'boost the frequency, it will add more phase warbles... which can become issues if you are dealing with a lot of frequencies 'warbling' frome the EQ.... cranking 20+ db on an EQ especially a digital one... (though there may be a few SSL and Linear Phase that translate quite well) is just silly.... that needs to be put away

 

[chris carter]

um.... the more EQ you apply, the more phase distortion is entered.... Once something has been cut, it is gone... it has also left a little phase warble to the sound... so if you want to re'boost the frequency, it will add more phase warbles... which can become issues if you are dealing with a lot of frequencies 'warbling' frome the EQ.... cranking 20+ db on an EQ especially a digital one... (though there may be a few SSL and Linear Phase that translate quite well) is just silly.... that needs to be put away

Most EQs are minimum phase EQs and the relationship between phase and amplitude is 100% reciprocal. So provided the Q doesn't change (and not withstanding other characteristics like noise, distortion, etc.) if you boost 3dB at 4kHz and then make the exact same 3dB CUT at 4kHz the phase introduced with the boost will be undone with the cut - leaving you right back where you started.

That said, from a practical standpoint, it's meaningless because why would anyone intentionally do that? And if you do some crazy EQ and then don't like it, you just need to do something that sounds good - not necessarily get back to 100.0000000% of the original. This is music after all.