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MXR M87 Bass Compressor Settings Help

Discussion in 'Effects [BG]' started by tovey87, Oct 18, 2011.

  1. tovey87


    Feb 2, 2010
    I am a noob when it comes to compressors and need some help. I purchased a MXR M87 compressor today to go in my effects loop and eventhough I notice a change for the good in my tone, I'm not sure on how to achieve exactly what I want.

    First of all I'm not sure if I should place it in the effects loop of my Trace Elliot with my other pedals (if so where about to achieve the best result, before after overdrive etc.) or place it before the amp.

    Secondly, I want to have a punchy sound and I'm unsure how to set the m87 to achieve this. I have read Bongomania's FAQ (which is excellent) and he suggest set the ratio of compression to 8:1. I now know I have a slightly better understanding of what the attack and release knobs do but I have read various posts suggesting that having the correct input level on the pedal for my required sound is extremely important! I know I can use the meter on the pedal to help me reach the required amount of compression. Should I be aiming for the input level to light up the -3 to -7 dB LED or should it be a smaller difference?

    Can anyone give me any assistance on this? I really want to maximise the potential of the pedal as it will really improve my overall tone!

  2. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    So, while you're checking out the FAQ, be sure to read the sections on "how to use the effects loop on your amp" and "good settings".

    I would say, as a broad starting place, set the input on the pedal so that your playing mostly just lights up the green LEDs. Set it so your quietest notes don't light up any of the LEDs, or only just a smidge, and your stronger notes light up more of the green. There's absolutely nothing wrong with lighting up the yellow and red, but when you're starting out, reserve that range for when you are intentionally experimenting with heavier compression or hard peak limiting.
  3. tovey87


    Feb 2, 2010
    Thanks for the reply! Here is what I have understood from the your 'good setting' FAQ, I hope I am understanding it correctly!

    Increasing the input level on the pedal reduces the threshold, meaning that more of my signal will be compressed? And is a signal only compressed with a low to mid ratio, in the case of the M87, compression can be achieved best using ratios 4:1 and 8:1? And the ratio means that if the signal goes X times over the threshold, the signal is compressed. So if the ratio is 4:1, it means that if the signal is 4 times higher than the threshold, the signal is compressed? From what I understand, I need the signal to be compressed to produce a punchier sound as well as other factors.

    Is my understanding correct when I assume that reducing the input level means that there is more room for the signal to act as it is, with only the extreme peaks of a signal crossing the threshold and being smoothed out. This would be good when using a synth pedal for example as you sometimes get extreme peaks from the pedal? So higher ratios of signal to threshold would need to be used for this?

    I'm still unsure slightly on the release setting of the pedal. I assume that a punchier sound is achieved from a quick attack setting? As a higher atatck setting means it takes less time for the signal to be compressed.

    To achieve the punchier sound that I want, is it better for the release time to be set to short, so that the signal is back to normal before being compressed again. I think I read in one of your FAQs that if the release time is longer, the signal wont go back to normal before being compressed, having a negative effect on the signal.

    Thinking out loud now, I'm starting to doubt my assumption that a punchy sound is achieved by compressing the majority of the signal and maybe that setting a higher threshold ratio would help me achieve my desired sound as only the extreme peaks of the signal will be smoothed out.

    Sorry for all the questions, I am extremely keen to fully understand how my compressor works as I have realised how important this is from reading your FAQs with a setting being slightly out could mean that it has a bad effect on my sound. Any comments on my understanding of your FAQ would be hugely appreciated!

  4. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    I'm not quite sure what you mean here... 4:1 is moderate compression and 8:1 is strong compression.
    Ah, no--if the signal is any amount over the threshold it gets compressed. The amount it's compressed is the ratio. A ratio of 4:1 means for every 4 dB the signal goes over the threshold, it only goes up by 1 dB at the output. It's not that there's a "boost" of 1 dB, but that "1" represents a percentage of change.
    To be clear it's not a ratio of signal to threshold, but a high ratio is good for capping extreme peaks. The threshold is set independently, based on the specific signal you feed it.
    It's actually the reverse: the faster the attack of the compression, the faster it starts compressing. I have an article about "punchy" sound, and one of the points is that everyone has a idea about what punchy means, with a fast or a slow attack. Try both ways, see how it feels.
    Yes, although it's not "negative" if that's the desired effect. It's a popular and traditional model, having the signal always just within the compression envelope. Depends on the vibe wanted.
    Doubting assumptions is a good thing! :D Experimentation is key.
  5. tovey87


    Feb 2, 2010
    Thanks for all your help, I am away until Monday now so I won't be able to test it out til then! I can't wait to get back and start working on it again! I'll let you know how I get on and see what you think! Thanks again!
  6. I have this same compressor and I'm a total noobzor also.

    So far I've just been trying to set the threshold such that my moderate playing trips one or two green LEDs. Quiet notes do not light anything. And when I'm banging away on the fretboard like a maniac, it lights up more of the lights. I've tried compression ratios of 1:4 or 1:8. Mostly I just leave it on 1:4. Attack and Release are at noon. Output is set for unity gain, more or less.

    I kind of set it and forget it. I take a look at the lights now and then to see if they're still behaving as I expect. If not, I adjust.

    Possibly I'm missing out on a lot of interesting settings one can get with this pedal, but that's where I'm at for now.
  7. ninepoundjammer

    ninepoundjammer Supporting Member

    Apr 23, 2010
    Berkeley, CA
    Just picked one of these up. So what's the deal on the ratio setting; does it also change the threshold? If I leave input the same and increase ratio, I should see more LED's lighting up, no? I'm seeing the opposite.

    This thing is working fine for me at 4:1 or 8:1, but if I turn my input up enough to get any significant limiting going on at 20:1 I get distortion. Not that pleased.
  8. Alvaro Martín Gómez A.

    Alvaro Martín Gómez A. TalkBass' resident Bongo + cowbell player

    If you have a low threshold (input knob clockwise) and a high ratio, a fast release time (release knob clockwise) will result in distortion, and it will get worse with a fast attack time (attack knob clockwise). Check your settings and try to avoid that scenario.
  9. That's a good question. My gut reaction is "no." But the metering doesn't really seem to behave as you'd expect, so I'm not sure. The manual doesn't seem to say anything about it, though.

    Make sure you have a fast attack and fast release. Then adjust the input such that only your loudest notes light up the meter.

    I'm not sure what could be causing your distortion. But are you running the output such that it's close to unity gain with your bypassed signal?
  10. Also, for posterity, I thought I'd update my previous comment about my own settings.

    I now run at 8:1 all the time and my threshold is such that every note lights up the meter, even finger style. I try to avoid burying the meter when I slap, though. I think I've settled on a moderate-to-fast attack and a moderate release.
  11. ninepoundjammer

    ninepoundjammer Supporting Member

    Apr 23, 2010
    Berkeley, CA
    Huh. Sure enough, slowing down the attack and release times does eliminate the distortion. Thanks for the tip.

    It still seems as if the ratio settings also change the threshold.
  12. I just got this pedal, too, and I noticed the exact same thing.

    I set the pedal for 4:1 ratio, Attack & Threshold at noon, adjust Input(threshold) so 3 to 5 LEDs light, then Output for unity gain.

    When I increase the Ratio and leave everything else as-is, less LEDs light up (the opposite of what I expected).

    Did you find anything out?
  13. JohnDavisNYC


    Jan 11, 2008
    Brooklyn, NY
    Endorsing Artist: Aguilar, D'Addario, Subdecay, Tonefactor
    that's because of something called the 'knee' of the compressor... since there are so many things about this pedal that are similar to the old UREI 1176, i'd assume that the knee situation is similar.

    basically, a lot of compressors will have what is known as a 'soft knee' at lower ratios. this means that the unit eases into compression before the threshold is actually reached, and then reaches the full compression ratio when the signal reached the actual threshold. this makes sense, because generally with a lower ratio you are looking for some smooth, subtle dynamic shaping, and it generally feels more musical to have that sort of response. now, when you're up at 20:1, you are using the unit much more as a limiter, and generally speaking, are looking for a more aggressive sound. if feels and sound much better to have the limiting happen in an immediate and aggressive manner.

    granted, this is speculation as far as the MXR comp goes (haven't used one yet) but lots of experience with vintage and reissue UREI gear.... and the 1176, LA4, and LA2A all exhibit harder knees and (apparently) higher thresholds at higher ratios.

    kirillio likes this.
  14. Thank you for your response.

    From your explanation, and what I would expect, wouldn't the following happen (keeping the same settings, except ratio):
    lower ratio = less gain reduction, therefore less LEDs light up on the meter,
    higher ratio = more gain reduction, therefore more LEDs light up on the meter

    However, with all things remaining the same (see setup in previous post), when the ratio is increased, the opposite happens with the meter.
  15. Someone should reach out to Dunlop and see if any of their engineers can clarify this for us.
  16. Does yours do the same?

    I sent them an email.
  17. To tell the truth, I haven't really done the experiment. But I suspect that it does. I'll see if I can investigate this weekend.
  18. JohnDavisNYC


    Jan 11, 2008
    Brooklyn, NY
    Endorsing Artist: Aguilar, D'Addario, Subdecay, Tonefactor
    You misunderstand my post. At higher ratios, the threshold is effectively raised, so you see less gain reduction on the meter, but relative to the threshold, the gain reduction itself is actually greater, although the total g/r may be less....

    This is partly why meters are great and why they suck.

    For instance, slap a real 1176 on a snare drum, and at a 4:1 ratio, you will get g/r at a relatively low input gain. However, it will sound rather squishy, because it is beginning to compress at a lower threshold, but because it is a low ratio, you will still have a rather large dynamic range. Switch the 1176 to 20:1 and the needle may not move because the threshold is higher. This is for a few reasons. One reason I didn't mention is that with a high ratio and a low threshold, it is difficult to achieve small amounts of gain reduction without having the input very low and the makeup gain cranked. This is noisy and sucks for all applications.

    Basically the short answer is that there is less apparent gain reduction at higher ratios for gain structure reasons, and also it's important to keep in mind that higher ratios are not necessarily intended for more gain reduction.

  19. It has to be something like this. I can't think of another explanation other than a complete malfunction/design flaw of the unit.
  20. Thank you!!