compressors: the real differences

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cello_pudding

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What makes a compressor different than another?

wave goes in, amplitude reaches a height, amplitude gets reduced by a certain ration at a certain reaction time and release time...they all have the same settings and function. most compressors will have a high/low attenuator.

What makes one different than another? is it the way the wave is analyzed? turning one compressor to the exact same settings as another...it seems they would sound the same. Is it like these 1 band compressors are acting like a set multiband compressor to create these sonorities?
 
cello_pudding said:
Is it like these 1 band compressors are acting like a set multiband compressor to create these sonorities?
Click to expand...

That's possible, also they can have an EQ effect that is not amplitude-dependent, and they can have different knee behavior. They might also create harmonic distortion in pleasing or displeasing manners, like any other amp.

There's probably lots of other reasons too . . .
 
Ah, grasshopper...

Both sound and electronics are FAR too complicated for our simple analysis. That's why specs lie like cheap rugs, and two components with basically identical specs can have radically different sounds. Don't ask why... you can spend a lifetime studying and wind up feeling like you know even less (if only because you realize then how many more things you don't know).

But please, PLEASE do not say that "A and B do the same thing and have the same specs, therefore they sound the same, and anyone who says different is suffering from a placebo effect due to the money they spent". Coz that's a big cop-out.
 
they do the same things, but i know they don't sound the same

the placebo money thing exists, but still we know they sound different for whatever reason.

i guess that's why the companies making them and i just use them.
 
Everything from the metal on the front panel to the topology of the PCB will change the way any electronic audio gear will sound.
Remember that between the microphone and the speaker, audio is some form of EM wave, and hence obeys all hte usual rules for EM waves.

And, unless you really, really like EM waves (it happens), then you probably won't enjoy the answer to the "why do compressors sound different?"

However, there are a couple of simple things that make compressors different

Detection/triggering- How the unit decides when to start/stop compressing. Does it detect the peak level across the entire frequency range, or does it have a specific trigger band? etc

Compression engine- It could be digital, optical, tube, or solid state/vca. Each one has different effects on the compression.

Release method - how does the compressor release the signal from it's compression? does it bypass it's circuit, or does it simply crank a VCA to it's full potential?

Then, as I mentioned, there's actual, physical differences. Does the circuit path get wider at some point? Does it pass near the power supply?

Etc.

If you really want the answer to thee questions, I'd suggest the "Geekslutz"forum on gearslutz.com, or an EE/Physics degree.
 
yeah, i was wondering about the engine/nitty gritty details
 
cpl_crud said:
Everything from the metal on the front panel to the topology of the PCB will change the way any electronic audio gear will sound.
Click to expand...

very informative post but I have to ask how the metal faceplate will affect the sound. its not like the voltage runs through it. unless the circuit is grounded to the faceplate, and then I am still not sure it would make a differnece.

don't forget the makeup amp, input and output impedances, and whether or not the knobs go to 11. :D

quick question...
why not, "why do different mic amps sound different" or "why do different guitar amps sound different". A marshall is a fender clone, why do they not sound the same?
 
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Whatever the physical cause, the effect on the signal can be expressed in the time, frequency, or amplitude domain. Maybe there's a domain I missed, but the point is the user is interested in the effect on the signal more so than the cause.
 
a little of both...

you know what would be really cool... set up a mic and out it to a few different compressors. just sing something and then zoom in and give us a screen shot of the wavs. (you'd have to bounce a wave that uses a plugin compressor)

i would actually really like to see/hear the differences between different mic pres, especially tube pre's expirimented in the same fashion.

i would...but i don't have a studio like you guys. aka....i use all plugin compressors and have 0 tube pre's.( besides in my school's studio) but i may buy a nice pre in the future.

now this could be an interesting thread
 
cello_pudding said:
a little of both...

you know what would be really cool... set up a mic and out it to a few different compressors. just sing something and then zoom in and give us a screen shot of the wavs. (you'd have to bounce a wave that uses a plugin compressor)
Click to expand...


Or one better, just simply close your eyes and use your ears. The best assets of a compressor don't show up on a screen, they pour out of the speakers. :)
 
FALKEN said:
unless the circuit is grounded to the faceplate, and then I am still not sure it would make a differnece.
Click to expand...

In pretty much all equipment, the ground for the power is connected to the chassis...

However, remembering that we're dealing with a box full of oscillating currents, anything that is able to carry current will react to it... Aluminium and steel will react differently to the current, and thicker/thinner metals will also have different reactions.

The faceplate can also provide some degree of sheilding from external influences.

Most gear will run at an internal voltage of about 17V across the opamps. A 0.1V fluctuation due to magnetic reactance from the faceplate is about 0.5% difference- way above the quoted THD levels for most gear.

Rackmounting can lead to strain on the faceplate, which can distort the casing, and, possibly, the PCB.

So, there really are a number of ways that even someting as simple as a faceplate will alter the sound- even if that alteration is very slight.

And I believe that cause and effect are linked- I'mone of those "understand the basics and work from there" kinda people. Or maybe i'm just mad.

Also, the listening to the speakers is probably better than the waveforms, or at least listen frist, look second.
 
ok..then if someone has the capabilities to make a 160 mp3 and upload it to yousendit.com or something...that would be awesome

just sing happy birthday or something
 
cpl_crud said:
Most gear will run at an internal voltage of about 17V across the opamps. A 0.1V fluctuation due to magnetic reactance from the faceplate is about 0.5% difference- way above the quoted THD levels for most gear.
Click to expand...

Except that audio grade opamps are designed to be insensitive to small power supply fluctuations.

Seriously, that is the easiest thing in the world to test. Run a sinewave through a very basic opamp circuit, once with faceplate, once without, and analyze the result on an oscilloscope, and document the THD. I really doubt you can degrade opamp THD performance to that extent by changing faceplate metal. No doubt you can degrade noise floor with poor shielding, but that isn't the same thing. And strain on the faceplate causing an audible or even measureable difference at audio frequencies . . .

At any rate, gear is tested assembled, not rated from opamp specs, and it's easy for an enduser to verify THD within a limited measure of confidence, certainly 0.5% is going to have a hard time hiding.

Of course there is a cause and effect, and circuits are the sum of their parts. I firmly believe in scientific testing and measurement; however, this is a design issue more than a user issue. Even so, several of your claims seem to go beyond what is measureable, so if you can document them, please do.
 
I was simply stating that the whole unit will effect the sound.
I'm not saying that if you strap a behringer faceplate on a 1176LN that yuo're going to degrade the signal noticably.

Sure, everything is tested, but at the super-high end they take everything into consideration, becuase they can afford to. When you crank out thousands of compressors a day, you're not going to care about the quality of the amps, and much less the faceplate...

However, you do raise a good point- is it actually noticable? I might investigate this further, and I'll let you know. I do know that with a signal generator and a oscilliscope you can tell the length of a cable, and find any joints in it. Sure, it's piss all, but it's there, and visible even on a crappy, 4" CRO screen.

The OP asked what makes one compressor different from the other, and I simply wanted to point out that there are many, many factors that make compressors different, and it's not a simple case of lining up compressors bytheir published stats alone...
 
cpl_crud said:
IThe OP asked what makes one compressor different from the other, and I simply wanted to point out that there are many, many factors that make compressors different, and it's not a simple case of lining up compressors bytheir published stats alone...
Click to expand...

Fair enough. But compressors aren't exactly the same as preamps, there aren't really published stats that are meaningful for compressors, not because the stats aren't honest, but simply because THD and noise tell you nothing about the behavior of the compressor that you're interested in. Preamps are at least a little different in that respect.

Besides, people seem to want color out of compression more often than pres. Just a random observation, I can't back that up with any actual data :o
 
cpl_crud said:
Everything from the metal on the front panel to the topology of the PCB will change the way any electronic audio gear will sound.
Remember that between the microphone and the speaker, audio is some form of EM wave, and hence obeys all hte usual rules for EM waves.

And, unless you really, really like EM waves (it happens), then you probably won't enjoy the answer to the "why do compressors sound different?"

However, there are a couple of simple things that make compressors different

Detection/triggering- How the unit decides when to start/stop compressing. Does it detect the peak level across the entire frequency range, or does it have a specific trigger band? etc

Compression engine- It could be digital, optical, tube, or solid state/vca. Each one has different effects on the compression.

Release method - how does the compressor release the signal from it's compression? does it bypass it's circuit, or does it simply crank a VCA to it's full potential?

Then, as I mentioned, there's actual, physical differences. Does the circuit path get wider at some point? Does it pass near the power supply?

Etc.

If you really want the answer to thee questions, I'd suggest the "Geekslutz"forum on gearslutz.com, or an EE/Physics degree.
Click to expand...



Yup. Go to gearslutz.com They have sound engineers their that know their stuff.
 
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