Spectrum analyzer questions

[Blue_fire]

I have been trying to wrap my head around the understanding of a spectrum analyzer/peakmeter. the only thing i really can't understand is why is everything negative from zero?
EDIT: more importantly, can anyone link me to some good reading on the overall effect of an eq. Mostly i leave all of my music flat, but learning is never somthing i leave flat

 

[Aleatoris]

dunno if this is related to what you're asking, but here you go anyway:
http://www.head-fi.org/forums/f4/how...torial-413900/

 

[Blue_fire]

Quote:

Originally Posted by Aleatoris /img/forum/go_quote.gif dunno if this is related to what you're asking, but here you go anyway: http://www.head-fi.org/forums/f4/how...torial-413900/

hmm thats actually a constructive read, thanks.

 

[Rempert]

On a digital peak meter, 0db refers to full scale. This is a reference point that is supposed to represent the greatest amplitude possible in the digital system. Anything louder than that will clip. Going beyond full scale is like when kids try to one up each other and come up with gems like "infinity plus ten". When you try to apply that number to the real world, it can't be done. So we need to ultimately end up with everything at or below that full scale reference. Hence the negative numbers.

You need to keep in mind also that decibels are a logarithmic unit. Everything is relative. Every time you lower it 6 db (roughly), you've cut the amplitude in half. So, -24 db is about 1/16 the amplitude of 0 db (half of -18, which was half of -12, and so on). Raising by 6 db doubles the amplitude.

With regards to the effects of EQ, I think the best thing is to experiment and learn by listening. Take a song you are familiar with, preferably with some vocals and real instruments, and see what happens to the sound if you boost just one specific frequency band. Then work your way through the spectrum doing that and get a feel for what happens. If I boost at 500 hz, how does that affect the bass? How does it affect the snare drum? What does it do to the vocals, or the guitars? What about if I boost at 5000 hz? You have to hear it for yourself. Then maybe do it again with another song to confirm your impressions. Once you have an idea what each frequency band actually sounds like, you have a foundation to consider your own tastes or weaknesses in your playback chain.

 

[Acix]

Analog or digital, never cross the 0db...remember only green, no red light.

 

[CDBacklash]

Actually, you want the first red light (or last orange) on most mixing desks

 

[Acix]

Quote:

Originally Posted by CDBacklash /img/forum/go_quote.gif Actually, you want the first red light (or last orange) on most mixing desks

No red light

 

[gregorio]

The first two paragraphs by Rampert were accurate and the last post by Acix. BTW, Acix, analogue is routinely overdriven, ie., beyond 0dB, but digital never can be.

As a general rule I would always advise a consumer not to EQ. There are a lot of issues regarding EQ, many of which are mis-understood by consumers:

When mixing down, the digital master is often maximised to within a few tenths of 0dBFS, particularly when creating a 16bit version from a 24bit original. Applying any EQ boost to a file mastered in this way is obviously going to hit 0dBFS and cause distortion, unless the input level into the EQ is significantly lowered. So the rule would be, if you are going to EQ only cut, never boost. Unfortunately, depending on the EQ software and the type of EQ applied, even cutting may cause brief peaks which again could distort. Some DACs have reconstruction filters which allow for an extra 3dB or so of headroom to avoid clipping, as even the reconstruction filter itself can cause peak overs. If you have to EQ, the best place is after the DAC, in the analogue domain.

G

 

[Acix]

If the levels stack on the 0db, any EQ change in the dynamic can cause distortion.
Some of the distortion you can monitor, and some not, and this why you need the most sensitive audio equipment that you can get...some music software and hardware have default of -12 / -6 and -3 db, and you can insure a minimum headroom and future good for mastering.