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Post by scorpiodog on Sept 18, 2018 11:43:22 GMT
Experts all, I'd like to try to understand something that, I confess, may be beyond me.
I have a friend who used to be a sound recording engineer. We were chatting about my EQ settings when playing with Men In Black. Just to be clear, I need to explain that my job in Men In Black is to supply the steady beat using an acoustic guitar. If you like, I take the place of the back line in a full band. So my EQ settings, in simple terms, are to boost the bass and cut the mids out almost entirely. This gives me a low thump even though I'm only using an amplified acoustic in standard tuning.
My friend, Jeremy, was telling me that I should boost frequencies lower than the low E on an acoustic guitar. He was saying that I could exploit frequencies as low as 80Hz (which he says is the low E on a bass).
What I can't understand is how there is anything to boost at 80Hz. I can understand how I can utilise harmonics above the fundamental for any given string, but on the basis that string length, thickness and tension provide the fundamental of any given string, where can lower frequencies come from? Jeremy assures me that strings produce what he calls sub-harmonics, but he couldn't explain in any terms I could understand where these sub-harmonics come from.
Is he talking rubbish? I doubt that, though knowing the man as well as I do, he is fully capable of BS in subjects on which he is not an expert, but in sound engineering he IS an expert.
I've tried as hard as I can to explain the query, but in technical matters such as these, not only is my knowledge limited, but my vocabulary is also sadly lacking. So:
a) Can a string produce harmonics lower than the fundamental? b) If so, why?
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Post by Deleted on Sept 18, 2018 12:43:11 GMT
Absolute bollocks Paul. Like you said, there is very little down there to actually boost. If you want a low end punch its is sometimes better to boost frequencies around the 120Hz mark- far more effective. Lower than 80 is just rumble, and a lot of speakers aren't going to make much of that anyway.
Robbie
p.s re the harmonics- no, you cant add harmonics lower than the fundamental- it goes against the laws of physics!
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Post by scripsit on Sept 18, 2018 12:47:11 GMT
By definition, a harmonic is a higher frequency than the fundamental by whatever proportion: the harmonic is determined by the fundamental, but is always some multiple of it (ie, higher).
The bass E of a guitar is about 82 Hz (as a fundamental note), and that is as low as you can get on this particular instrument which sounds like a musical note.
When you record acoustic guitar, it is common to use a 'high pass filter' as EQ, which takes out everything below (say) 50 Hz, which is usually room and reflection noise, not directly from the guitar itself. It's probably a good technique for sound reinforcement, too. Anything below the bass E fundamental is probably mud. You will find some people expect it because they think this is what amplified sound should be like.
Unless you are using the face of the guitar for percussion, I can't see the point in trying to produce very low tones through the PA.
By the way, the 'mid' tones , 300-500 Hz, are what most people hear as bass when you crank the volume.
I think you need to do some experiments where you get out of front of the speakers while you are playing and listen to what happens as EQ is varied.
Kym
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Post by andyhowell on Sept 18, 2018 17:15:43 GMT
I agree. This is bollocks as there is nothing really there. To be fair there are lots of weird shit tricks that are done by studio engineers but you are talking about playing live.
All you need to do is to get a good sound and the think about the two of you together — somebody might have to cut some mids to get rid of muddy-ness (if there is any).
But not doubt the two of you have been playing long enough to know your sound.
What I find weird is that in a combo setting in studio recording if anything they will cut a hell of a lot of the bass on an acoustic.
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Post by Craig on Sept 19, 2018 10:15:09 GMT
I've been thinking about this with my scientific head on!
Yes it's true that the fundamental frequency of the low E string is around 82Hz so you would think there is nothing below that but there are also intermodulation frequencies being generated between different notes.
Think of the beat frequency you listen for when you tune a pair of strings, this might start at 10hz and go down to zero as they become more in tune. These will also occur when playing chords.
Whether or not this is something you want amplified is debatable but you can't argue with science 😁
Craig
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davewhite
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Post by davewhite on Sept 19, 2018 10:35:12 GMT
Remember that there are a number of things that you have to think about the physics of - one is the sound producer and the other is the sound receiver and processor, aka the brain. The brain is a wonderful and not fully scientifically understood thing, for both vision and hearing it fills in based on past "sampling" experience. I know that for baritone guitars one way to get the problem low string usually pitched around A to be clearly heard is to have the middle string gauges such that the tensions are really high. The loudness of these means that the brain fills in the much lower frequency range and you hear the lower bass string. Not great for the long term structural stability of the instrument but it works.
I am not a master of the dark arts of sound men/women but some of this may be at play in the situation you describe Paul.
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Post by andyhowell on Sept 19, 2018 10:35:54 GMT
I've been thinking about this with my scientific head on! Yes it's true that the fundamental frequency of the low E string is around 82Hz so you would think there is nothing below that but there are also intermodulation frequencies being generated between different notes. Think of the beat frequency you listen for when you tune a pair of strings, this might start at 10hz and go down to zero as they become more in tune. These will also occur when playing chords. Whether or not this is something you want amplified is debatable but you can't argue with science 😁 Craig Possibly. But then I doubt this is anything to worry about when you are plugging into the pub PA!
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Post by soundout on Sept 19, 2018 10:58:06 GMT
Interesting what Dave White said about the brain compensating for what the ear isn’t actually hearing. As a team of sound engineers providing PA at folk festivals, we often notice this when we have travelling guest sound engineers who come with the bigger bands. The common complaint from the audience (apart from it being too loud of course) is that they can’t hear the words. It became clear to us that the regular sound engineers listen to the bands’ repertoire so much that they actually know each song by heart, whether they have set out to learn them or not. Their brains seem to be filling in the missing detail, and not to notice that the crowd is right when they say they can’t hear the words. In a former life I was such a touring engineer, and as a performer, we always toured with our own engineer. I sincerely hope I/we didn’t let the audiences down. Regarding the original query about frequencies and where to place a rhythm guitar in the mix, I feel you should have a radical rethink of your whole PA mix with a new set of ears telling you what the crowd is actually hearing.
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davewhite
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Post by davewhite on Sept 19, 2018 11:37:48 GMT
It became clear to us that the regular sound engineers listen to the bands’ repertoire so much that they actually know each song by heart, whether they have set out to learn them or not. Their brains seem to be filling in the missing detail, and not to notice that the crowd is right when they say they can’t hear the words. Having heard some of those words my brain sometimes does the same job as those sound engineers
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Post by Craig on Sept 19, 2018 12:13:19 GMT
That's an interesting thought, as an audience member it's always easier to hear the words of songs you already know.
Craig
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