Does anyone know how to test a compressor/limiter using an Audio Precision System 2?

Why do you want to compress/limit anything? These processes decrease sound quality.

a compressor/limiter is practical tool to control dynamic range. It's used often in many types of recording & mixing because it makes the dynamics easier to manage and easier to mix. And when used in certain ways, a compressor/limiter can have certain musical effects. There are actually compressors out there designed to create "undesirable" compression effects such as pumping, distortion, etc. It is also used in mastering to achieve decent volume levels without clipping the signal. It's okay to limit a few peaks a few dB for the sake of not making the song way too soft.

Unfortunately, in H.A. the only context we ever hear "compressor" and "limiter" are in the cases of super-squashed records. Those cases illustrate the flat-out misuse and abuse of a compressor/limiter.

(as for Jon2980, sorry.. I don't know ) edit: spelling

I don't agree. The only case limiting/compression isn't diabolical: The technical specifications don't allow enough dynamic range (FM radio or so). Music naturally has peaks. Once you've started with that, you'll soon end up with what we have today.

go listen to a rock record without compression on the drums and tell me if you think it sounds good....

the sound you hear from a CD isn't natural to begin with. Recording music is a totally unnatural process. Think about how drums (where most peaks come from in generic music) are typically recorded... a set of certain mics chosen for their certain characteristics are placed right next to the drums. Already this is different from how humans hear a drumset. It's completely unnatural, and it will give you unnatural peaks... ones that might be irritating, unnatural, and just have to be limited.

And it all gets converted to digital data, mixed, eq'ed, compressed, reverbed, etc.etc. in order to make it fit into the mix. And then played back through a couple of headphone cones or speakers.

You remove the compressor cuz its evil, but so what? Let's remove the effects and reverb and EQ while we're at it b/c they are just as evil. Let's remove the mixing console (unnatural level/balance adjustment -- evil) microphones (evil), the recording room (unnatural environment -- evil), the whole rest of the studio... and you get "_______"

this sort of "unnatural" sound design is all part of recording an album. Bands and/or their producers will decide on certain mics, and certain recording & mixing methods in order to aim for a certain sound. It's all part of the art. Even if you want to aim for a "natural" sound on a CD, you will have to obtain it through unnatural methods such as mic choice & placement, the whole mixing/eq/compressor/efx ball, and the end result is entirely artificial (with the illusion of "natural" sound). To say the hell with artificial sound recording processes (or even just the compressor), you are removing part of the art of your favorite CD.

a compressor is a practical tool with several applications that help to enhance the sound of the album. Since the aim of any album is to create a good sound, a compressor can be used to make a good sound. Using it is not a slippery slope to hyper-compressed squashed albums. There are actually intelligent ways to use it, and valid reasons to do so. Just as you can misuse a mixer, an EQ, effects, and a microphone setup or what have you... you can misuse a compressor. And unfortunately most mainstream albums do.

Seannyb has it nailed. Compressors are really useful on drums, but not to limit peaks, noooo... Take a drum that sounds too boomy. Apply compression with 100-300 ms of attack or so. The initial attack goes through (leaving a nice peak transient), then the compressor kicks in and mutes the drum, giving you that nice quick & punchy drum sound. A compressor in this instance actually increases the peak to average ratio!

This guy is right on the money. Seriously, I find the overreactiveness of HA's readers absolutely appalling, and I'm the guy who created loudnessrace.net!

People think that limiters automatically = noticably less dynamic mix, when a limiter, when used PROPERLY, are designed to only effect very, very small portions of the waveform; we're talking barely audible here. A snare drum transient will be made up of multiple sine waves, and simply attenuating one or two of these will not cause any significant damage to the sound. An audiophile might notice an extremely slight lack of "sparkle", but the dynamics in general should be unaffected.

It's only when you start clamping down on the rest of the mix and begin to lower average levels of the transients that you have to start worrying.

(analogy)

This post made me thinking. I've experimented something with this, and, in fact, a compressor, used in this way, can increase the impact of a drum hit, since it reacts 'too late'. But I wouldn't call that "compression" any more, it's just "dynamics processing".

To reiterate what others have said, compression, just like anything else, is a great thing when used properly. I am much more familiar with live sound reinforcement techniques than anything else. Compression and gating can really help the sound of a drum kit. Another example is if you have a horn section, like in a ska band, compression is very necessary, horns can be very loud and kill the mix if not kept in check.

To answer the original question, I would think that you would want to check things like frequency response, phase distortion, and check that the amplitude is scaled to match the ratio of compression you are using.

yeah, that's a pretty common use for a compressor. An interesting technique I read about a while ago (haven't thought to try it yet) is to mix the poppy compressed signal with the original signal, and you'll get that poppy compressor sound without squashing the drums' dynamics into sameness