A thread for asking the things you should know by now but don't

[juicylime]

You know what I mean. We've all got 'em!

Ok, I'll go first; Why does a graphic waveform have top and bottom shapes that aren't symetrical? What different things do they represent?

That wasn't so hard once I just asked it!

[Oroz]

Originally Posted by juicylime

You know what I mean. We've all got 'em!

Ok, I'll go first; Why does a graphic waveform have top and bottom shapes that aren't symetrical? What different things do they represent?

That wasn't so hard once I just asked it!

A sinewave would be identical because is the same frequency (100 Hz for example) but musical instruments are not, they have different frequencies, harmonics and stuff, do you know what I mean?

[No4PCs]

I always worry about that too ! Maybe the Volume variations of the signal?

[Oroz]

Originally Posted by No4PCs

I always worry about that too ! Maybe the Volume variations of the signal?

...and different loudness of course .

[strings]

Okay, I'll bite.

How do you know when to use the "phase" button on a preamp?

[peeder]

Originally Posted by strings

Okay, I'll bite.

How do you know when to use the "phase" button on a preamp?

Effectively, when it sounds better that way.

It's most often used in two situations: first, on a vocal cue, the phase interactions between the direct sound from the singer's throat to their ears can interact badly with those coming in via their headphones, so you want to give them the best sounding cue mix. This will vary depending on how the mic is wired and how far they are from the mic. Flip it and ask them what they like better.

Another frequent use is when there is an intrinsic phase reversal when micing a source from different positions. For instance, if you mic a speaker cab from front and back simultaneously, then the relative phase will be inverted on the two signals. This is because when the speaker is moving toward the front mic, it is moving away from the rear mic. Flipping the phase of the rear mic will result in far less cancellation on the low end and a louder sound. Drums miced from both sides can also exhibit this effect.

Finally you can use phase-nulling to ensure two mics are in optimal phase. When positioning an AB pair, you flip the phase of the B mic, and move it until it combined with A makes the least sound you can find. Flip it back into phase and your mics will be ideally phase coherent for that point source.

[Silentstudios]

Originally Posted by peeder

Effectively, when it sounds better that way.

It's most often used in two situations: first, on a vocal cue, the phase interactions between the direct sound fromt he singer's throat to their ears can interact badly with those coming in via their headphones, so you want to give them the best sounding cue mix. This will vary depending on how the mic is wired and how far they are from the mic. Flip it and ask them what they like better.

Another frequent use is when there is an intrinsic phase reversal when micing a source from different positions. For instance, if you mic a speaker cab from front and back simultaneously, then the relative phase will be inverted on the two signals. This is because when the speaker is moving toward the front mic, it is moving away from the rear mic. Flipping the phase of the rear mic will result in far less cancellation on the low end and a louder sound. Drums miced from both sides can also exhibit this effect.

Finally you can use phase-nulling to ensure two mics are in optimal phase. When positioning an AB pair, you flip the phase of the B mic, and move it until it combined with A makes the least sound you can find. Flip it back into phase and your mics will be ideally phase coherent for that point source.

I've also been told to hit the phase button when using the rear side of a "figure of eight" pattern mic, such as a ribbon.

[peeder]

Originally Posted by Silentstudios

I've also been told to hit the phase button when using the rear side of a "figure of eight" pattern mic, such as a ribbon.

Sure...you want absolute polarity to be correct.

While many people argue that polarity switches are inaudible, a quick demonstration with a sawtooth wave will show that is not the case. Your speakers will reproduce one polarity differently than its opposite, and I believe we should strive to maintain the polarity that a listener in a live situation would have heard.

[lordwesley]

um, What do the initials XLR stand for?

[Old Cane]

Originally Posted by strings

Okay, I'll bite.

How do you know when to use the "phase" button on a preamp?

When it has one.

Well, Peeder beat me here but yeah, use it. If it sucks, don't use it.

[morphtec]

Xternal, Live, Return.

Originally Posted by lordwesley

um, What do the initials XLR stand for?

[big country]

(cannon) X latch rubber
Originally the "Cannon X" series, subsequent versions added a Latch ("Cannon XL") and then a Rubber compound surrounding the contacts, which led to the abbreviation XLR
XLR connector - Wikipedia, the free encyclopedia




question

how many different guitar neck scales are their????
fender 25 1/2
?
?

[djwayne]

In reference to its original manufacturer, James H. Cannon, founder of Cannon Electric in Los Angeles, California (now part of ITT Corporation), the connector is colloquially known as a cannon plug or cannon connector. Originally the "Cannon X" series, subsequent versions added a Latch ("Cannon XL") and then a Rubber compound surrounding the contacts, which led to the abbreviation XLR.[1] Many companies now make XLRs. The initials "XLR" have nothing to do with the pinout of the connector. XLR connectors can have other numbers of pins besides three.

[Old Cane]

Originally Posted by lordwesley

um, What do the initials XLR stand for?

Originally the "Cannon X" series, subsequent versions added a Latch ("Cannon XL") and then a Rubber compound surrounding the contacts, which led to the abbreviation XLR


Kind of like "here have a coke" and hand you a Pepsi. It was a brand type name that became generic. I don't think they get a royalty but who knows.

[lordwesley]

Interesting stuff. I'd guessed at maybe ground/left/right or something. I've heard them being referred to as cannons now and again. It all falls into place. Thanks.

[Francis Vaughan]

Ok, I'll go first; Why does a graphic waveform have top and bottom shapes that aren't symetrical? What different things do they represent?

A pure tone is of course symmetric. Just a sine wave.

Fourier showed that any periodic signal can be made from a series of harmonics. So if we want to break down your waveform we can do it by taking a sine wave at the base frequency, and then adding to it harmonics of that base frequency. So a sine wave of twice the frequency, three times, four times etc. For each harmonic we need to determine two things, the level of the harmonic and the phase of the harmonic. But once we have done this we can exactly construct your waveform.

Now we come to an interesting result. You can show that if the waveform is half wave symmetric (i.e. if you shift it in time half a period, and then flip it over - it will exactly match itself) it can only contain odd harmonics.

The upshot of this is that if your waveform contains any even harmonics it cannot be half wave symmetric. Since even harmonics are very much part of musical sounds, it should be no surprise at all that your waveform isn't symmetric.

[idylldon]

Originally Posted by big country

how many different guitar neck scales are their????
fender 25 1/2
?
?

Any scale you'd like. A friend of mine builds custom guitars and basses and routinely makes non-standard scale lengths for his clientele. Cutting the fret slots is just a matter of programming the CNC machine with the results from a scale-length calculator.

Here's a link with some info:

Stewart-MacDonald: Fret scales

Cheers,
--
Don

[PhilE]

Maybe this doesnt really qualify but.... why do consoles have a phase flip button rather than a phase sweep pot? Is it just a cost issue?

[backhair]

headroom?

i'm under the impression that it has something to do with the ammount of electricity running through the components (discrete components run at a higher voltage than ICs for example, and thus have higher headroom), but for all the talk, i've never seen anybody explain what headroom is, what it sounds like when you "run out", why you need more, etc. did tad donnely make it up?

[FireMoon]

What is left and right?

Do people use the stage left and right definition asre the performers perspective, or do you use left and right as in relation to your own listening position?

[mdme_sadie]

Originally Posted by PhilE

Maybe this doesnt really qualify but.... why do consoles have a phase flip button rather than a phase sweep pot? Is it just a cost issue?

Because phase can be altered two ways and to invert you would either -

1) True inversion - Simply invert the phase of the signal, i.e. what's high becomes low, what's low becomes high, basically it's a simple polarity switch, positive becomes negative, negative positive.

2) You shift a signal over by 180 degrees... yup it's ambiguous and that's the problem because a signal is made up of many waveforms of varying length, so which length do you choose? Shifting the phase and adding it together with it's original source is in fact the basis of most EQ and filtering algorithms.

So basically it's because there's no way to know how much of a sweep you should do to invert, and if you swept a true inversion what you'd actually end up doing is reducing volume down to -infinity then reducing it to negative 0... so not very useful. Inverted phase is simple and works.

[staudio]

Headroom.

Headroom is the difference between your "standard operating level" and the
"maximum operating level"

Operating level of pro gear is +4dBu

Maximum operating level is the highest level the circuit can reproduce without distortion.

Headroom is the difference between the two.

If your preamp has a maximum output level of +20dBu then your headroom is 16dB.

A circuit can be discrete or integrated and have the same headroom.

[staudio]

On Headroom,

In some amplifier designs, as the level of the signal approaches the maximum operating level the sound of the amplifier may change. The sound of this change is dependent on the amplifier design. Some amplifiers even sound "good" when pushed beyond their maximum operating level. Some tube amplifiers and transformer coupled amplifiers begin to produce what is called harmonic distortion when overdriven. We sometimes call this distortion "warmth" or "saturation"

When you run out of headroom things start to sound "clipped"
transients get squashed and squared off, and eventually you get a square wave which doesn't sound very nice.

[wheever]

On headroom:

(just to add an illustration.)

...So when you run out of headroom the signal will "clip"--squaring off the top and bottom of the wave (clipping it off or distorting it) turning your sine wave progressively into more or less a square wave as headroom is exhausted. In the digital realm especially, this is really ugly.

[Kiwiburger]

Originally Posted by juicylime

You know what I mean. We've all got 'em!

Ok, I'll go first; Why does a graphic waveform have top and bottom shapes that aren't symetrical? What different things do they represent?

That wasn't so hard once I just asked it!

The reason this happens in real instrument sounds is basically simple physics. Say we hit a string, or a membrane, the first excursion of the string or membrane is the loudest. After that, it springs back due to elasticity, and it's losing energy all the time - pushing air around & internal friction. It's the same principle that a pendulum, once released, will never return to it's original position.

Wind instruments and vocals are under the control of the player/singer, but there will still be some asymmetrical component - especially with sibilance and plosives.

[strings]

Good Thread!

Thanks for answering the Phase Button question!

Sometimes when I use it, it may sound better, but less stable (or less consistent).
That is usually with just a single mic for vocals.

When that happens, I don't use it (like suggested above).

[Oldone]

How did Unity Gain get that name?

[TheBluesBrother]

Ok this one has been literally hurting my neck recently. . .

Why does everyone put racks of gear on the floor in studios. Why not prop everything up at least a foot or two so you don't have to break your neck to use the bottom pieces of gear. I'm sick of having to sit on the floor to EQ something. If I ever get to build my own studio I will make the gear easily accessible.

[skatingbasser]

Originally Posted by FireMoon

What is left and right?

Do people use the stage left and right definition asre the performers perspective, or do you use left and right as in relation to your own listening position?

There is stage perspective and audience perspective.

"Stage Left/Right" is the perspective of the performer on stage looking out to the audience. His Left is Stage Left.

If you're behind a board facing him, then you're left (Audience Left) is actually his right. So when you're looking at the stage and want to signal the guitar on YOUR left, you have to call him Stage Right.


FYI closer to the audience is Downstage, and further back (towards the drummer) Upstage.

[Francis Vaughan]

Originally Posted by Oldone

How did Unity Gain get that name?

Unity is a mathematical synonym for one. It crops up in many places, not just gain. The English language loves slight abbreviations, so "unity gain" == "gain of one". "Unity" is an adjective whereas "of one" is an adjectival phrase. It is easier to construct sentences.

"A unity gain amplifier" versus "An amplifier with a gain of one."

Eventually of course it just sounds more technical, and people love that.