Hi guys,
How can I figure out whether the EQ I am using is linear phase or not? (Of course the manual has not mentioned or explained it)
The other question is whether iZotope RX spectral cuts are linear phase or mess up phase?
What about spectral cuts in Adobe Audition?(Cuts like 4096db/Oct)
My main problem is Limiting. When I want to limit audio I want to have control on bands and limit each band separately and I know there are some plugins like ML4000 from MCDSP which are multiband limiters but I want to do it manually but I am not sure whether It f&cks up phase or not!

 

If the manual has not mentioned it, it's probably not linear. You could in theory set up a plugin analyzer and observe the effect on phase response as you boost and cut, but realistically ain't nobody got time for that. If they didn't proudly say it's linear, it isn't. Btw, as you know, non-linear EQs have their own advantages.

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RX uses a linear phase engine for the editor. The built in EQ though, is switchable. The "analog" mode is the non-linear phase one.

Check out the Newfangled Elevate 26 band limiter, it sounds like your dream come true. It's also got multiband transient shaping and multiband saturation, if you want it. Also fully linear phase. Have fun!

 

Pass a dirac spike through it. That's a single sample of maximum amplitude in a section of silence. If the filter is non-linear the spike will pass through the filter with a trail of diminishing oscillations passing out behind it. Linear phase filters work by calculating time both forwards and backwards, consequently the dirac spike will pass through the filter with rising oscillations before the spike point and oscillations after. This is why linear phase filters mess with transients, it's the leading wave that softens them.



A linear phase dirac delta function.

 

Well you explained it thoroughly but didn't tell where to find a dirac spike.

So you mean if I do spectral editing it is linear phase? I know the EQ Module has two modes. I am talking about the spectral editor.

 

So would you suggest Newfangled Elevate for separating bands for limiting?
BTW, the purpose of asking this question was finding a manual way doing it instead of using a tool. I am actually looking for manual way doing it without messing with phase.

 

Newfangled Elevate nice for what it is, you might be able to do what you're wanting a lot faster with it. And certainly much cleaner than if you were setting up your own homebrew crossover filters. The linear crossovers it uses are pretty special and tuned in a special way to have the least pre-ring.

Another issue, how independent do you want the limiting bands to be? If one band is having a lot of limiting occuring, should neighbour bands just ignore that and do their own thing? That has an effect on how it sounds when you're pushing hard. With Elevate, there's fine control available for this, and they even claim there's "AI" helping things sound more natural. You can dial the AI up or down as desired.

 

You make one using a wave editor such as Wavelab, Samplitude or Sound Forge. Many DAWs will allow you to do this too, these days. You get 2 seconds of silence, and draw a single spike at 1 second.

 

As Satai said Elevate bundle is a great tool, if you want crazy amount of control of each limiting band check out DMG Multiplicity, takes a while to get your head round it but is a deep tool!
BTW Linear phase tools don't always sound the best, it does sound better smearing the phase sometimes too.
It all depends on the source etc...
Best of luck MaXe

 

FIR = linear phase.

Spectral editing SHOULD be FIR.

Limiting audio is NOT a linear process, and artefacts might not be symmetrical. Then the rest lies in whether the multiband crossovers are FIR or not. Ozone 5+ has configureable crossovers , see http://help.izotope.com/docs/ozone/pages/options_dynamics.htm

 

What do you mean by "Limiting audio is NOT a linear process"? As far as I know limiting is changing dynamics and does not mess with Phase. Does it?

 

With what exactly should I draw a single spike? Could you give me a link or any tutorial explaining what you have in mind?

 

Sure. You need a tool that allows you to change individual samples in a wave. Reaper can't do this. Wavelab can and Samplitude can.

First you need a few seconds of silence. There'll be either an insert silence function in your editor, or, you can just record a few seconds of nothing.

Next, you have to zoom right down to the level of single samples, this will be a very, very small up close zoom.

Then, using your wave editing tool, grab and drag a single sample from silence up as high as it will go. Save it. That's a dirac spike.

Next, get your filter, insert it in the channel holding the dirac spike and render the filter by bouncing the file. That should give you a clear image of the filter's processing effect. If it results in a blank file the filter's modelling is rejecting the "high frequency" of the spike, keep adding adding additional samples immediately next to the first until you get a spike that will survive the filter's smoothing and modeling.

 

Well, I'm being vague so it could be true, limiting adds harmonics which weren't in the original, & you never know what's going on underneath that might mess with the phase