limiting/ cross over

[buryher17]

can someone please explain what exactly a limiter does. and what crossovers are.

these are the only 2 things i never really grasped or got to understand well. I ahve a compressor/limiter/gate and dont really get the limiter part.


thanks

 

[legionserial]

A limiter is a device or plugin you use to minimize the dynamic range of audio in order to make it louder, usually in the mastering phase. Its basically an extreme form of compression. You will notice that your mixes aren't as loud as modern commercial cd's, the limiter (amongst other things) is used to make it louder. It works by bringing up the quieter bits and smashing down the peaks to get it all level. Which is not how music should really be, but the industry really cares more about money these days than making nice sounds. Basically if you get a modern cd, and rip it to a wav file, and have a look at the waveform, a lot of them you will see that the waveform is more of a block of color, than a bunch of peaks and valleys as it should be.

A little limiting is ok, but its got to the point now where all the dynamics are smashed out of music, and it sounds like shit. Limiting is not the only contributor to a louder mix. Decent tracking and mixing is a majorly important factor. However don't expect to get your mixes as loud as a commercial cd at home with a limiter plugin. Trying to push it that loud will result in shitty squashed abrasive sounding mix that will give you ear fatigue.

As for crossover, it depends in what context you mean it. One definition is the frequency at which your audio will 'crossover' from coming from your speaker to coming from your sub. But there are a bunch of definitions as I say depending on the context.

 

[RAK]

legion got it right on when he said that a limiter is an extreme form of compression. Generally, you can think of a compressor with a ratio of 10:1 or more as limiting. Now the exact definition of when compressing becomes limiting is vague, and could be debated at length, and other factors (not just ratio) may play a role in the differences, but this is a very basic sense.
With really high ratios, anything above the threshold is reduced so much, it essentially hits a wall (hence, brick wall limiting) and is limited to the point of no signal above the threshold.

Crossovers can be complicated, as there are different kinds, and different kinds of filters that can be used, but essentially, if you have a speaker with a tweeter and a woofer, each driver handles its own information (high freq. for the tweeter, low freq. for the woofer). The crossover network is the thing that splits the audio and sends the highs to the tweeter and the lows to the woofer.
Basically if you take a high pass filter, and a low pass filter, and cross them, the point where they cross is called the crossover. A two way crossover will have 2 filters and 1 crossover point, splitting into high and low. A 3 way crossover has 3 filters and two crossover points, splitting into high, mid, and low. Crossover networks can also be active and passive. And the there are a few different types of filters (Bessel, Butterworth, Linkwitz-Riley). I think that wikipedia does a decent job of giving a basic overview of crossovers.
http://en.wikipedia.org/wiki/Audio_crossover

Also here's a basic signal flow of active versus passive crossovers:

Passive: Amp->Crossover->Tweeter
-------------------------->Woofer

Active: Crossover->Amp->Tweeter
------------------>Amp->Woofer