Low end rubbish

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Re: Low end rubbish

Post by RichardT »

Hugh Robjohns wrote: Tue Jul 05, 2022 12:16 pm
Stig Ø wrote: Mon Jul 04, 2022 8:55 pmThe filters had center frequencies at approx. 100Hz, and the one-band HP on the master buss has a 24bB/octave slope.

The master buss is waaaayyyy too late for filtering out subsonics. You've got to get rid of them at the earliest point in the chain. Otherwise all your other processing -- especially compression -- is likely to make the situation far worse than it need be.

So if you have a subsonic filter on the mic, use it. If that's not doing enough and you have a high-pass filter on the preamp, use that too... or instead.

And once the signal is in the digital domain, the very first plugin should be a third-order (18dB/oct) high-pass filter. Some filters are steeper -- analogue synth filters are commonly 24dB/octave and digital filter algorithms can often provide some seriously steep filter slopes -- but 18dB/oct is about the best compromise for effective subsonic removeable with minimal audible side-effects.

If your plugins have a linear-phase option, use that too because steep filters do inherently mess up the low-end phase response and you might not like the audible effect (it can start to sound slightly unnatural). Experiment with the high-pass filter's corner frequency (centre frequency applies only to band-pass filters) to find a setting that minimises unwanted subsonics without affecting tone.

This is good advice. If the noise really only occurs during the rasgueados, I would consider automating the EQ so that it only kicks in at those points. Because rasgueados have a large noise component, you won’t notice the filters kicking in and out. That way you avoid any negative effects of HP filtering on the rest of the track, even though they are likely to be small anyway.

It’s common for recordings to have unwanted low frequency components - are you sure everything is OK on the rest of the recording? If not, that would change the picture and leaving the EQ in place would be the best option.
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Re: Low end rubbish

Post by Martin Walker »

The Elf wrote: Mon Jul 04, 2022 5:42 pm A technique I use for assessing low end is to place a finger *gently* against the edge of a speaker cone. You can learn a lot about the low end using this technique.

Damn - The Elf beat me to it with this tip.

I can however add that you can often see really low end unwanted cone wobble visually without using your fingers. I tend to spot it on instrumental (and particularly synth) performances that I receive from elsewhere, that haven't yet been mastered, and occasionally on Bandcamp releases where the musician has smaller monitors, so hasn't heard or spotted the problem before release.

Sound libraries can sometimes be the worst offenders, particularly with kick and other explosive sounds, so watch out!
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Re: Low end rubbish

Post by James Perrett »

That's the one good thing about the white cones on the NS10 - it makes it easier to see the cone moving which is the best way to judge bass on them.
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Re: Low end rubbish

Post by The Elf »

James Perrett wrote: Tue Jul 05, 2022 8:54 pm That's the one good thing about the white cones on the NS10 - it makes it easier to see the cone moving which is the best way to judge bass on them.

Bass on an NS10? ;):lol:
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Re: Low end rubbish

Post by Stig Ø »

Thanks again, everyone. Hugh, I see your point about placement of the filter. I do have a HP on a regular channel eq before the compressor, but I’ll try changing the placement and type of the steep filter and use a linear phase eq for that part. I’ll report back.
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Re: Low end rubbish

Post by Stig Ø »

So I followed Hugh’s advice and swapped out the main buss one-band eq with a linear-phase low cut in the first channel effects slot. In addition, I disabled the two lowest bands in the regular channel eq that I use to shape the rest of the guitar sound. The sub artefacts are now almost completely gone, except a tiny flicker in one of the rasguedos. Next time I’m doing a solo acoustic recording I’ll be sure to enable low cut on the mic itself, or the preamp. Speaking of which, are there important arguments for choosing one over the other, or is it a hear for yourself kind of deal? Thanks to everyone who helped out - much appreciated.

-Stig
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Re: Low end rubbish

Post by Hugh Robjohns »

Stig Ø wrote: Wed Jul 06, 2022 9:09 am So I followed Hugh’s advice and swapped out the main buss one-band eq with a linear-phase low cut in the first channel effects slot....The sub artefacts are now almost completely gone...

Yay! I'm still a useful old fool... :lol:

Next time I’ll be sure to enable low cut on the mic itself, or the preamp. Speaking of which, are there important arguments for choosing one over the other...

Low-cut filters on preamps are usually second (12dB/oct) or third (18dB/oct) filters typically with a corner frequency between 30 and 80Hz. These are ideal for helping to reduce unwanted LF and subsonic noise.

Mics that have LF filters can have one or other (or both) of two types of low-cut filter. You need to know which type is provided to use it appropriately.

One type is intended to remove unwanted LF and subsonics, so has a low corner frequency between 30 and 80Hz and a reasonably steep slope of 12 or 18dB/oct.

The other type is intended to correct for proximity effect (bass tip-up from close placement of directional mics) and usually has a very gentle slope of 6dB/oct with a much higher corner frequency, typically somwhere between 100 and 250Hz.

Because the slope is so gentle and the corner frequency so high, this proximity correction filter is of no use for removing subsonics.

So you need to identify the type(s) of filtering provided on your mic, and use the correct one if available.

There's no problem using the low-cut filter in the mic and the low-cut filter in the preamp at the same time if you really need to. Using both together effectively makes the slope even steeper and so gets rid of more subsonic rubbish.... but it will also introduce more LF phase shift which may be noticeable.
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Re: Low end rubbish

Post by Zukan »

Use the band solo feature in your eq to isolate and hear what is allowed through the lead in on the slope. I tend to go for higher slopes for cutting low end nonsense but you really do need to be wary of how the slope affects the attack transients on low end sounds. On some sub basses if you use a steep slope you can end up with a clicky attack.

Pay attention to the type of eq you are using as well.
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Re: Low end rubbish

Post by Stig Ø »

Zukan wrote: Wed Jul 06, 2022 11:52 am Use the band solo feature in your eq to isolate and hear what is allowed through the lead in on the slope. I tend to go for higher slopes for cutting low end nonsense but you really do need to be wary of how the slope affects the attack transients on low end sounds. On some sub basses if you use a steep slope you can end up with a clicky attack.

Pay attention to the type of eq you are using as well.

Thanks - good advice. I’m not sure that Logic’s eq has a band solo function, but will look into it.
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Re: Low end rubbish

Post by Stig Ø »

Hugh Robjohns wrote: Wed Jul 06, 2022 11:30 am
Stig Ø wrote: Wed Jul 06, 2022 9:09 am So I followed Hugh’s advice and swapped out the main buss one-band eq with a linear-phase low cut in the first channel effects slot....The sub artefacts are now almost completely gone...

Yay! I'm still a useful old fool... :lol:

Next time I’ll be sure to enable low cut on the mic itself, or the preamp. Speaking of which, are there important arguments for choosing one over the other...

Low-cut filters on preamps are usually second (12dB/oct) or third (18dB/oct) filters typically with a corner frequency between 30 and 80Hz. These are ideal for helping to reduce unwanted LF and subsonic noise.

Mics that have LF filters can have one or other (or both) of two types of low-cut filter. You need to know which type is provided to use it appropriately.

One type is intended to remove unwanted LF and subsonics, so has a low corner frequency between 30 and 80Hz and a reasonably steep slope of 12 or 18dB/oct.

The other type is intended to correct for proximity effect (bass tip-up from close placement of directional mics) and usually has a very gentle slope of 6dB/oct with a much higher corner frequency, typically somwhere between 100 and 250Hz.

Because the slope is so gentle and the corner frequency so high, this proximity correction filter is of no use for removing subsonics.

So you need to identify the type(s) of filtering provided on your mic, and use the correct one if available.

There's no problem using the low-cut filter in the mic and the low-cut filter in the preamp at the same time if you really need to. Using both together effectively makes the slope even steeper and so gets rid of more subsonic rubbish.... but it will also introduce more LF phase shift which may be noticeable.

Thanks, Hugh. When recording acoustics I use the UA 4-710D preamp. It has a corner frequency of 75Hz, with a slope of 12dB/octave, if memory serves. The frequency on the Røde mic hasn’t been easy to find, but I’ll stick with the preamp’s filter in the future.
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