A Mic below 50Hz? Why?

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A Mic below 50Hz? Why?

Post by ManFromGlass »

If very few end user sound systems can reproduce the fundamental of the low E on a bass (roughly 40 Hz depending who you ask) I am wondering why one would choose a mic that can record lower than that.
For the projects I work on (for media, never tunes to be heard on their own) I usually roll off pretty steeply at 80Hz for the final mix. I do roughly the same when recording. I occasionally record acoustic and electric bass and have a good monitoring system with a sub and I’ve never felt that bottom was missing.
Curious what others think.
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Re: A Mic below 50Hz? Why?

Post by blinddrew »

Piano? Goes down to 28Hz, pipe organs can go lower, but more frequently I'll frequently put a low synth pad on stuff that'll fill out that 20-40Hz octave.
If I hi-passed my stuff at 80Hz I'd be loosing quite a lot of content.
The other thing to remember is the growing use of headphones, most of which will comfortably go down to 20Hz.
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Re: A Mic below 50Hz? Why?

Post by ManFromGlass »

I’m counting, and perhaps incorrectly, on the listeners brain filling in the fundamentals from the overtones. For film and tv music this keeps the low end cleaner for the big explosions and big machine sound effects etc.
That being said I have layered an octave below sine wave sub tone in with a kick now and then. Perhaps I need to rethink my philosophy. Always something to learn in this business!
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Re: A Mic below 50Hz? Why?

Post by Hugh Robjohns »

ManFromGlass wrote: Tue Aug 24, 2021 1:19 pm If very few end user sound systems can reproduce the fundamental of the low E on a bass (roughly 40 Hz depending who you ask) I am wondering why one would choose a mic that can record lower than that.

Do you record for the lowest common denominator, or the highest possible standards?

And while few cheapo sound systems might reproduce 40Hz fundamentals, most earbuds and headphones can take a damn good stab at it.

There's also the fact that the electric bass isn't the only instrument on the planet; plenty of other instruments (and percussion) generate content well below 40Hz and which is critical to their sound quality and character.

It's also well known that the phase relationships between channels at low frequencies contribute significantly to the sense of spaciousness in a recording.

So all in all, having material in that bottom octave is important and does make a difference in the right contexts.

Returning to mics with a roll-off below 40Hz, it's quite an educational experience to compare the sound of something like a 'cello or even a violin recorded with both a cardioid capsule (natural roll-off around 40Hz) and an omni capsule (natural roll-off at least an octave lower). I've demonstrated this many times with Sennheiser MKH40s and 20s, and every time the audience/students notice that the omni capsule sounds much more natural and, in comparison, the 40 sounds 'phasey' and wrong in a way they find hard to put into words. Heard on its own, no one complains about the cardioid, but in direct comparison it's obvious and I think it's down to unwanted phase shifts linked to the roll-off.

It's often a good idea to 'bracket' the sound on individual sources with high-pass (and sometimes low-pass) filtering, but I'd rather have the option at the control desk or in the DAW, rather than have it enforced by the mics.
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Re: A Mic below 50Hz? Why?

Post by ManFromGlass »

Hugh Robjohns wrote: Tue Aug 24, 2021 4:14 pm Do you record for the lowest common denominator, or the highest possible standards?

And that is what I wrestle with. I haven’t worked on a project with a good budget in awhile so can’t afford to go to a “proper” studio. My studio is ok to good for close mic recording. Why would I want an awesome mic for a room like that? I have a few good mic pres but at some point it’s has to be diminishing returns with an increase in quality (and budget with is another factor). So more mental wrestling and research is in order.
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Re: A Mic below 50Hz? Why?

Post by Martin Walker »

Hugh Robjohns wrote: Tue Aug 24, 2021 4:14 pm It's often a good idea to 'bracket' the sound on individual sources with high-pass (and sometimes low-pass) filtering, but I'd rather have the option at the control desk or in the DAW, rather than have it enforced by the mics.

Hear hear!

Taking this route rather than relying on any built-integral mic filter, you also get the option of using different cutoff 'shapes' - many HPF plug-ins in particular may offer a slight resonant peak at an octave above the cutoff frequency, which may balance out the loss of the extreme lows, as well as the standard roll-off at typically 12dB/octave or 18dB/octave.

Some even offer fully-variable Q to adjust the height of the resonant peak, so you can tweak with your ears to suit the sound. I use LTL Chop Shop's EQ for instance (available from Plugin Alliance):

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Re: A Mic below 50Hz? Why?

Post by Hugh Robjohns »

ManFromGlass wrote: Tue Aug 24, 2021 5:36 pmWhy would I want an awesome mic for a room like that?

Why wouldn't you? If the mic isn't capable of capturing the most accurate (or most desirable) sound why bother at all?

But it's worth remembering that phase-shift mics -- meaning most conventional cardioids, hyper-cardioids and super-cardioid (including multipattern capacitor mics) -- rarely if ever have a bass response that extends much below 40Hz. The physics simply doesn't make it practical.

If you want to pick up stuff below that then you need to use an omni (which will typically stretch down to 20Hz or lower) or arguably a good quality ribbon fig-8.
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Re: A Mic below 50Hz? Why?

Post by ManFromGlass »

So if Earthworks says their cardioid mic does 30-30k at 6” are they being accurate or is there something they aren’t saying?

As for what awesome mic means to me, I didn’t express myself correctly.
I mostly close-mic, recording 1 instrument at a time. The room does not add any desirable sound that I want to include in the mix. So I’ve ruled out an omni mic. Rarely I record acoustic bass or concert bass drum or other instruments that have low frequencies. I do have a nice Royer for those.
I usually eq out the low end of what I do record up to just where I hear I am losing the sound of the instrument. I thought if the mic only went down to say 50Hz then it would be a bit less eqing to do. But other comments now have me questioning my approach - which I am totally open to.
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Re: A Mic below 50Hz? Why?

Post by Sam Inglis »

ManFromGlass wrote: Tue Aug 24, 2021 8:38 pm So if Earthworks says their cardioid mic does 30-30k at 6” are they being accurate or is there something they aren’t saying?

It's a fairly meaningless claim unless a tolerance is specified. If they said ±3dB from 30Hz to 30kHz that would mean something.

Looking at the graphs of their SR30 for example it's fairly clear that there is a roll-off below 100Hz. At 5 inches it looks to be about 8dB down at 30Hz. Yet they claim a frequency response of 20Hz to 20kHz for that model.

I suspect that the roll-off is partly deliberate since the mic is designed to be used close up. It certainly should be possible to create a cardioid mic that is a lot flatter than that in the low end even at a greater distance.
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Re: A Mic below 50Hz? Why?

Post by Hugh Robjohns »

ManFromGlass wrote: Tue Aug 24, 2021 8:38 pm So if Earthworks says their cardioid mic does 30-30k at 6” are they being accurate or is there something they aren’t saying?

They are unusual in stating the measuring distance -- bonus points to them -- but a tolerance range would make the response bandwidth really meaningful!

6 inches is well into the proximity zone, though, which will bolster and extend the low end a little below the typical 40Hz of most cardioids measured at greater working distances.

I thought if the mic only went down to say 50Hz then it would be a bit less eqing to do. But other comments now have me questioning my approach - which I am totally open to.

Doesn't really make any difference, does it? If you set the HPF to 60Hz it removes everything below whether the mic captures it or not!

But your recording rationale makes sense to me.
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Re: A Mic below 50Hz? Why?

Post by blinddrew »

ManFromGlass wrote: Tue Aug 24, 2021 8:38 pm As for what awesome mic means to me, I didn’t express myself correctly.
I mostly close-mic, recording 1 instrument at a time. The room does not add any desirable sound that I want to include in the mix. So I’ve ruled out an omni mic.

An omni isn't just about capturing the room though (or not as desired), as Hugh mentions above, it's about capturing the true character of the instrument. With guitar, for example, one of my preferred close mic'ing techniques is with a pair of SDC omnis, one around the 12/14 fret, one behind the bridge, both about 8" away. The proximity to the guitar means that I get a lot more instrument than room, the omni pattern means no proximity effect, and the natural response, I find, gives a more honest picture of the instrument, despite the close-mic'ing.
It's certainly worth trying if you have a less-than-good room and a pair of omnis around.
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Re: A Mic below 50Hz? Why?

Post by John Willett »

blinddrew wrote: Tue Aug 24, 2021 10:19 pm
ManFromGlass wrote: Tue Aug 24, 2021 8:38 pm As for what awesome mic means to me, I didn’t express myself correctly.
I mostly close-mic, recording 1 instrument at a time. The room does not add any desirable sound that I want to include in the mix. So I’ve ruled out an omni mic.

An omni isn't just about capturing the room though (or not as desired), as Hugh mentions above, it's about capturing the true character of the instrument. With guitar, for example, one of my preferred close mic'ing techniques is with a pair of SDC omnis, one around the 12/14 fret, one behind the bridge, both about 8" away. The proximity to the guitar means that I get a lot more instrument than room, the omni pattern means no proximity effect, and the natural response, I find, gives a more honest picture of the instrument, despite the close-mic'ing.
It's certainly worth trying if you have a less-than-good room and a pair of omnis around.

And the inverse-square law means that the closer you get the less room you get.

Omnis are great mics - I love them.

I know Hugh has already said most of what I would say (thanks Hugh) - but the loudspeakers in my living room go down to 30Hz and lower than that in the roll-off. :thumbup:
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