ReaComp Question.

ShanPeyton

Member
Hey gang, i have been absent for a good long while. My new job has robbed me of all the "fun things" in life. I vowed never to be "that" adult, but guess what. Life sucks when you have bills to pay for i guess.

My question is about the "preview filter" check box in reacomp? When i check it i hear a difference. And in previous projects i have done i have left it checked on for all my mixing and final outputs. I started looking around a bit and it seems some users say this is not a good practice?

Am i compressing all wrong? Should i have it unchecked? I was told to trust my ears and i have been really trying hard to do this, and i think i have been doing an o.k. job but now i may be leading myself astray?

Help ?!:(
 
I'm thinking you're not actually compressing at all!

I guess I'm not completely sure, but I'm pretty sure that preview filter just shows you the effect of the filters on the "sidechain" that feeds the detector that tells it when to compress and how far, but doesn't actually apply the compression. You're suppose to use that switch to fine tune your filter settings and then turn it off so the compressor can actually do its thing. I never actually use the preview filter thing, because you really should be listening to how the filter settings actually affect the compression*. Maybe if you're using it as a de-esser and really want to zero in on the offensive sibilance frequencies or whatever, but you'd still want to uncheck it to set up the actual compression.


*Actually, I don't really use the internal filter at all, but...
 
From the cockos forum answers when you have the 'preview' on, you are only hearing the frequency range specified by your high and low-pass filters, so it would sound different - but not compressed, just filtered.
 
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Well that is pretty cool. Great link!

But is it safe to assume that if i leave the preview filter box unchecked it has no adverse effect on the ACTUAL compression? It is just compressing the whole frequency range in its entirety.

That would make sense.
 
Well that is pretty cool. Great link!

But is it safe to assume that if i leave the preview filter box unchecked it has no adverse effect on the ACTUAL compression? It is just compressing the whole frequency range in its entirety.

That would make sense.

I don't think so. The preview filter just audibly "shows" you your hi- and lo-pass filters. Unchecking it still compresses based on those filters. It just doesn't filter the monitoring output. I've seen other plugins with this feature, it's just a way to hear the signal in the same way that your filter is hearing it.
 
In case it's not clear...

In normal operation - with Detector input set to Main L+R - ReaComp splits the signal into the audio signal and what is essentially a sidechain signal that feeds the detector. It's that sidechain signal that gets run through the filters. Then it is compared to your threshold setting, and depending on the other settings it figures a gain reduction amount. That gain reduction is applied to the main audio signal, which is what you hear out the other end...unless you've got "preview filter" checked.

Changes to the filter settings can sometimes make subtle differences, but can also be used for special things. The de-esser I talked about above is one - set the hipass up around 3-5-10K and it will only compress when the input signal has a lot of those high frequencies that make s sounds so nasty. Still compresses the whole signal, but only when it's excessively trebly.

You can actually get the same result by setting it up for actual external sidechain compression and feeding the "Aux" inputs with a filtered version of the original signal, which is really a lot more flexible, but a bit more advanced routing-wise.
 
I played around with it more last night and now i totally understand what it is doing now. Just when i think i understand basic compression Reaper goes and throws that at me.

It explains why some of my final mixes sound like unwashed butts. I use reacomp on my master channel just for a final little bit of "polish" (or so i thought) and i'd user that master glue preset and tweak it a bit. But i would always leave the preview checked because the changes i made were audible and then i would render that stuff down.

I should probably not do that anymore.
 
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