Use of Low Pass filters a general philosophy

A quick listen to the sound of a ribbon mic can confirm this premise.

best regards,
mike

It ain't as obvious as the low end, where bass and kick should rule, but the principal is the same.  Clear out the trash and leave those frequencies clear for stuff that needs high end.  If you listen to old tape/analog recording the very high end got rolled off a lot - naturally.  Between "loss-less" digital and over compression, a lot of modern music just sounds harsh and flat.

@

I tend to do some of the same as previously mentioned.  I don't typically HP piano but I will typically HP electric Keys pending the patch/synth sound.  I will almost always HP a VOX to clean up any prox. effect.

Jimbo21


Just curious about how people generally use low pass/hi cut filters. I guess I tend to forget about them except on bass
and reverb busses. I was watching a groove3 video (free 30 day trial), one of the studio secrets vids and the guy mentioned that you don't really need all those top end frequencies in today's digital realm.

Jim

Bass frequencies consume more spectrum than highs do, generally.   I roll off anything and everything I can from every track in the low end (even bass) to the point where I feel there's no extraneous garbage there.
 
Frequency "build-up" happens quickly and isn't always audible (but visible on an analyzer).   There is a tremendous difference  when this is done -- especially if you're using any compression (which most do and will).
 
However, I DO roll off top end on things that don't need it as well.   While the HF frequency build-up isn't as troublesome (due to the nature and speed of cycles), it does add some gunk just like LF's do.
 
I also do roll off some top end in the hi hats, cymbals, etc.   They, like strong bass freqs, affect the overall signal management in compressions/limiters.   This shows up even more when you've done a good mix then do some master limiting.  Since the overall signal is being pushed up, all that LF and HF 'gunk' gets pushed up even more.
 
While I'm not a big fan of the Sonitus EQ for deep EQ'ing,  it works really well for general EQ'ing.  So I have a preset that sets a HPF (lo cut) around 39Hz with a 1.4 Q and a LPF (hi cut) around 10K with same Q.   This is just to use as a quick setup.  I then tweak from there, subject to the source material.
 
I use this on almost every single track in a project and then adjust.  For example, a synth part may be able to be cut as low as 300HZ before it sounds different or less full.   So the numbers above are just to get a setting I can quickly tweak.
 
But it's the gunk build-up that can affect an overall mix, and that's why I think it's good to manage that early on.
 
 
 

All this advice is good but bear one thing in mind. Use the bypass facility of your HPF. Make sure you are doing good by switching it in and out. You can get too carried away with removing low end and then it starts effecting the sound of the actual part you are using the HPF on. eg it starts to make it sound thin. By checking switching in and out keep and eye on the low end of the sound you are directly on. Unless of course you are keen to shave a little low end off which is sometimes desirable. But you can also overdo it as well and start thinning out guitars etc and wonder why they sound so thin later on.

The HPF cutoff frequency does not have to be all that high in order to remove a lot of unwanted rumble etc..Then you are leaving the main sound alone. A good thing is something like the WAVES filter set for a very steep slope. Then you can set it lower and still remove unwated stuff and not efect the sound hardly at all.

Be aware of the ranges of frequencies of the instruments you are applying a HPF on. eg guitar goes down to 80Hz don't forget that!

For most genres, there's nothing but trouble below 40Hz. Chop off everything down there.

If you scope a lot of mastered tracks there is a hard low pass at 10-12KHz these days. I take this area out and it allows you come back with some nice upper end boosts on acoustic guitar and vocals without things getting harsh.

i high pass and low pass almost every single track.
i also do selective eq on every track, that depends on the source
i high pass my master buss at 32hz.

With the slope in opposite directions?

Sort of like a bandpass?

ba_midi

mike_mccue


With the slope in opposite directions?

Sort of like a bandpass?

Actually yes, now that you mention it :)
 
I have actually seen situations where an engineer low passed and high passed a signal to create a special effect or special sound.   It looks pretty on a scope.  (Not really lol).
 
I just wish the industry would have a consensus on the terminology. 
 
HPF = Low Cut Filter too.
LPF = High Cut Filter too.
 
The terms are often used interchangably.  It can be confusing if someone isn't aware of the actual functions or is just new to the entire field of audio. 

Yep, that's how you do the telephone voice simulation.

Not sure if anyone is acquainted with Imogen Heap but she is an amazing British artist who spent 2 years creating her last album at home. I find her music and her minimalist approach to creating music refreshing.

She has a neat way of approaching vocal de-essing which is to not use a de-esser. She creates clips of each T and S in her vocal track and applies a low pass EQ. Then she automates and last compresses. This keeps the compressor from over reacting and produces a very nice vocal result. Automated EQ and applied EQ can really make a track stand out.

The other tip is to not over automate but use EQ for parts where you want the guitar or piano to stand out. Bump it in the key range and voilà, no automation required which raises the conflicting frequencies as well as those you want people to hear.

Lot's of cool EQ approaches.

Aren't Low Pass Filters at the other end of the spectrum of High Pass filters?

Duh, I guess I should read thread titles before replying! Had I done so, I'd have realized that this thread was potentially more interesting than most, since it's HPFs that are the usual topic of discussion.

LPF applications:

- roll off highs above 16KHz prior to MP3 encoding
- make reverb and delays sound more natural
- take away unnecessary high frequencies from bass so you can beef up the midrange
- reduce sibilance on vocals
- make brass instruments less brassy
- hiss reduction
- make snares sound bigger
- frequency sculpting, de-cluttering the high end for the vocal
- reduce hit transients from kick and toms
- soften consonants on double-tracked vocals
- taking hats out of the kick track
- separating kick and snare for sidechain keying

Of course, for many of these applications you'd actually use a high shelf or baxandall filter rather than a low pass, but the concept is the same.

at the risk of seeming boorish...


may I refer everyone back to post #2?

best regards,
mike

Middleman

ba_midi


Phil,  I absolutely LOVE Imogen Heap.   Are you familiar with the track "Hide And Seek" that was done by Tiesto and her?  One my all time favorite tracks. 

Yes great track. That she gets such amazing sounds with very average outboard & mics and is an inspiration to home recording. Glad to know you are a fan Billy.
 
Bitflipper, low passing tracks was one of my duh inspirations in digital recording. Gives you some control over the "Edge" as they say. Talk to me about the sidechaining for kick and snare. How does that work?

Glad to know you're a fan of hers too, Phil :)
 
I had actually started a thread last year about "high end" ...  don't know if you remember it, but I was trying to focus in on why it is some records I love (and even some I don't) seem to have this certain sound in the 'top end' and in what ranges or ways that can be understood.
 
Since that thread, I've actually pretty much settled in on a better technique for myself -- one being the use of LPFs/Hi Cut filters and even moreso, as Dave/Bitflipper points out, more/better use of 'shelving' EQ.
 
And, if you don't mind me jumping in on the kick/side-chaining thing, I'll tell you the quick/easy way (at least one) that I use all the time now, even on non-dance tracks (but with differrent settings):
 
- Insert the Sonitus Compressor on the Master Bus as the FIRST FX in the bin.  Make sure it stays as first. (though this is not always necessary in different genres).
Just to start:
- Set the attack time to the equivalent ms of the tempo  (example:  at 125bpm set it to 120ms); 
- Set the release time to the shortest subdivision (roughly a 32nd note)
- Set the input threshold to between -18 and -20db
- Set the knee to between 4 and 9
 
The above settings are just rough targets -- you'll want to adjust once you have a real track to work with.
 
Now, have your kick on it's own track and create a SEND to the Sonitus Compressor on the Master Bus.  (You have to insert the compressor first, obviously).
 
Also set the send to be PRE not POST.   This allows you to adjust the kick's actual output track without affecting the signal going to the Send (as you probably already know/understand).
 
Now play back your project and play with the INPUT threshold of the Sonitus until you get the degree of side-chain compression you want.   The more input (ie, the lower the db threshold) the more "pumping" you'll get.  But if you just want to kind of tighten/clean up the feel, you won't want to go to low on this.  I find between -18 and -24 to be the range subject to how much signal is arriving at the Master Bus in the first place.
 
You'll see in the compressor there's now an "Audio" button -- clicking on that only plays the kick side chain signal, so you don't want that.  Clicking again gets you back to side-chain (and the Audio button will show as a toggle).
 
This takes  less than about 30 seconds to setup and tweak. 
 
You can then add other FX in the bin, and you can try moving their order but I've found having the side chain compressor first in the chain to work really well.
 
I often put yet another compressor, then a spatial control fx, then a final limiter on my master bus (for dance music at least) -- and I don't go too far with any of the settings on these other FX.
 
Hope that helps.
 
 

OH PS about side-chaining:   it helps to use an EQ prior to the side chain (like the inline Sonitus EQ) to roll of any of the bottom not necessary to the overall sound.

Otherwise that 'gunk' down there will also affect the side-chain.