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  1. #1


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    Multiband Compressor in GarageBand
    My last step in mixing before sending to iTunes is turning up the post and pre-gain in the AU Multiband Compressor. However, are these the only two things I should be adjusting?
    - If so, what are the standard dB levels?
    - Should I only be using one or the other?

    It always sounds so full in GB, but once exported it loses a lot of its punch, even when I adjust the post/pre-gain.

    Additionally, the exported MP3 sounds louder on my iPod and quieter on my computer when compared to other professionally mixed songs in my collection. How do I know where to keep it???

  2. #2

    deus_ex_machina's Avatar
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    Get your levels as close to 0 as you can without clipping before compression. Unfortunately I've never used the compressor in GB

  3. #3

    Audio.Trench's Avatar
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    What is it that you are trying to use a compressor on? I only ask because people typically have no idea what a compressor does exactly, or how it properly works.

    Before you use a compressor, you must understand how they work.

    First of all, you'll hear a lot of "they make the loud sounds quieter, and the quieter sounds louder."

    This is a false statement. In a nutshell, a compressor levels out the sonic dynamics of the signal, but limiting the the "highest" and "lowest" points of the waveform.

    With that being said, it makes it sound like the low sounds are being boosted, and the highs are being cut. A compressor is commonly used in country music, most notably during fast, clean guitar riffs which typically sound "uneven" because of the playing dynamics. You might hit some notes harder, and some softer than others.

    A compressor cuts the height of the signal to a preset level, usually the "Attack" knob. Comps can also add sustain (at least perceivable sustain) as well, by trying to keep the output level roughly the same, even if the original signal's volume is dropping.

    And like deus_ex_machina state, you want your mixdown to be as close to 0dB as possible, before adding any kind of compression, because the comp will change the sonic dynamics of the signal.

    Hope this helps!

  4. #4


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    When you say as close to 0dB as possible, what do you mean and how can I check for this?

  5. #5

    Audio.Trench's Avatar
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    Basically, decibels are measurements that express the magnitude of a physical quantity (ie, power or intensity) relative to a set reference level.

    That said, 0 dB is typically used as the reference level when dealing with acoustics, mostly because 0 dB is what a typical human considers "normal."

    To put things into perspective a bit, normal conversation between two people is anywhere between 40 – 60 dB.

    So by having your signals/tracks closer to 0 dB, you'll avoid clipping (the signal is too "hot" and makes things distorted and fuzzy sound). Since compressors change the sonic dynamics of the signal, if your track is currently pumping out at 20 dB, if you compress it, depending on the settings, you could cause clipping/distortion, or it could make your track seem quieter (again, depending on settings of the compressor). Also, keep in mind that compressors could possibly cause a lot of noise/hiss on your track while being used, and you'll often see a compressor paired with a noise gate/filter.

    To do this in GarageBand, I have no idea.. I don't use GB, so some one else might have to help you out. I found THIS link might help you out a bit more with the actual functionality of GB.

    Good luck!

  6. #6


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    Very helpful. Would you mind taking a quick listen to the song in question, after I've messed with the compressor, etc.? It's here: http://makeoutmusic.knoxware.org/gos...0done)%206.mp3

    It just doesn't seem to pack a punch. By that, I mean MP3s on my Mac sounds good at 3 ticks (when you hit the volume key on the keyboard). When I play my song, it sounds too quiet at 3 ticks, but good at 4 ticks. However, since a perfectly-mixed album by U2 off iTunes, for example, sounds too loud at 4 ticks, I'm assuming my song is too quiet overall.

    I have the pre-gain at -27.37 and post-gain at 4.21

  7. #7

    Audio.Trench's Avatar
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    Okay, so I've listened to it (cool sounding track btw!), and it's definitely very quiet compared to a track from a CD. I have the volume at max on my laptop, and it's somewhat at a "normal" volume level.

    Typically with pre/post-gain controls on a guitar amplifier, the pre-gain control would control the strength of the signal going into the pre-amp, and the post-gain is essentially the the volume for the power-amp section.

    That said, the pre-gain basically would be your "distortion" (typically labeled "gain") knob on the amp. So if you set it to a high level, you'd get more distortion. After that is set to taste, you'd use the post-gain to adjust the overall volume of what you're doing.

    Keeping this in mind, try adjusting the pre/post gains with this explanation in your head.

    For starters, increase the pre-gain slightly, then play the track back. If you notice the playback volume increasing, then you've solved your problem. You basically have to find the "sweetspot" between the pre and post-gain levels.

    Another thing to check out, is in the options of iTunes, check to see if the sound enhancer or volume balancer (forget what it's called) is enabled, this could affect your playback as well.

    Also, try playing the track on different things like iPods, cd players, other media players on your computer, etc.

  8. #8


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    I turned the levels in iTunes up to 100% while making the MultiBand Compressor a whopping 8.42. Again, it's louder in GB, but once it's exported, it's not. I'm wondering if maybe I'm not doing the compressor correctly. i want to select this for the Master Volume, right?

  9. #9


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    I found out what was wrong: I had Auto Normalize on. On one hand, it helped because I never mixed all of my tracks to stay out of the red so once it was exported, it never popped or clipped. However, once I took Auto Normalize off, it sounded like a sonic mess exported into iTunes.

    So what should be my next step: I've upped the post-gain to a whopping 30dB and increased the iTunes volume level to 100%. Still, I don't think there's much difference in the exported MP3. Does this Auto Normalize feature automatically cap volume limits no matter what I do?

  10. #10

    deus_ex_machina's Avatar
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    glad you figured it out and posted the solution. Now you can spend time adjusting the levels!

  11. #11


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    Heh, well, I shouldn't speak too soon. I just did a quick edit of my post regarding what to do next...

  12. #12


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    The problem I felt I always had when mixing down to 0dB and staying out of the red was a quiet mix. Sure, I could make it louder with the compressor, but either the drums or the bass always came out too quiet because I had to mix them in with 20 or so other guitar/synth tracks. I thought I had avoided that whole process with this Auto Normalize feature!

  13. #13

    Audio.Trench's Avatar
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    Glad you figured it out! I would've posted earlier, but I've been running errands all day! Haha..

    But yeah, like I said. I can tell you/teach you how to use a hardware compressor, but talking about GarageBand, I have literally no experience using it. I've always been a Cakewalk/Reason guy.

    But yeah, now you should have absolutely NO problem mixing everything down, and applying the compressor. Just remember to make sure you watch the pre-gain level, as that is the main control that will cause clipping in your tracks/signal. Unless, of course you want it to clip, but judging from the track you let me listen to, you definitely DO NOT want clipping to happen.

    Good luck!

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