Modding crossover frequency

[SwamiRob]

Ive got a dual band compressor that I was wanting to change the crossover on, currently it's at 350hz with a bit of an overlap either side, but I'd like to change it to something around 150-200hz so when I'm compressing the low end it's not affecting the sound of my bass as much. Currently it's very audible in the lower mids, and I only really want a tiny bit of compression on the rest of my signal compared to the fairly heavy hand I'm trying to give the lows to keep them nice and even.

This is the schematic, I have very very little electronics knowledge but I'm hoping changing a couple of values might be able to sort it:



Cheers for the help

[robthequiet]

Welcome aboard.

Do you happen to have a small value capacitor handy? Such as 10nF to 22nF, somewhere where in that range? What I would try, just to make sure we're in the right area of the circuit, is to place the leads of your extra cap across the leads of either/or C6 or C5. Careful not to short anything in the process! You may be able to tuck the extra cap leads under the leads of the existing cap and curl them over, or use clip leads. Then see if that has a result and let us know. Other forum dwellers may weigh in with other choices, so maybe this will give us all a bit of evidence. Hitting the exact crossover frequency will probably require some math. By all means, feel free to ask any questions as we go along.

[PRR]

> at 350hz ...change it to something around 150-200hz

Snip shows the capacitors to change.



Heavy precision is not usually warranted even on a 2nd-order crossover. "150-200" can be rounded to 175Hz.

350Hz/175Hz is half-frequency. (Another reason I jumped to 175-- lazy math.) Half frequency is double-size caps. So change 33nF to 66nF (68), change 47nF to 94nF (100).

As other-Rob says, you can indeed go lower by tacking caps *across* the existing caps. 33nF across 33nF is octave-down, 175Hz.

My gut-think is that 200-250Hz may be useful. But a bassist working with a guitarist who uses his fatter strings may have to put-out mostly under 150Hz. So put in some kind of lugs or turrets, so you can swap to 47nF or 150nF after some band-trials, without chewing up the circuit board. Don't go crazy fine-tuning. It isn't a sharp filter and the stage (and spectrum) is never big enough for all.

[ashcat_lt]

This is, of course, important information.  I have to admit, I always feel like just changing a cap to change a filter cutoff is "too easy" or something.  Like, that has to affect something else, no?  But actually, it usually works just fine.

Anyway, I don't mean to be That Guy, but...

Inconsistent low end from a bass guitar is usually better dealt with in other ways.  Compression can be a half-assed bandaid in some situations, but it's almost never ideal, and often just can't really help, depending on what's causing the inconsistency to begin with.

If you're playing exactly one note over and over and the low end is inconsistent, that's all you.  Sorry to say it, but that's all about your pick hand control.  You will be much better served to practice like crazy until you can actually play it the way you think it wants to be heard.  Adding compression after that can be an aesthetic choice to change the envelope and tone of the notes, but don't use it as a crutch to overcome poor playing.  Or, maybe, do use it as a crutch for now, but remember that a crutch is meant to be a temporary aid til you're done with physical therapy and can walk on your own.

If you got that down, but you're playing different notes on the same string and they seem to carry a different amount of weight, this is more likely something in the amp and/or room.  Either resonances in the speaker cabinet or poor acoustics in the room are making some notes stand out more than others.  Quite often, which notes are louder depends on where in the room you're standing.  If it's a cab resonance thing, you might be able to swap cabs, but if it's the room, it'll take some fairly serious construction.  You might be able to improve your rehearsal room or recording studio, but there won't be much to be done for any venue you might play in.  There really isn't anything at all that any compressor can do for you on that. 

If it seems like the inconsistency comes when you switch between strings - one string is louder or quieter than another, it might actually be either of the two above issues, but it can also sometimes be something in the setup of the instrument itself.  It might need some tweaking to saddle heights or pickup height or both.  Sometimes you have to "tilt" the pickup by raising one side or the other closer to the strings.  Or maybe you need staggered pole pieces.  Either way, just like the differences caused by poor technique, compression isn't really the best way to overcome this issue.

[PRR]

> I always feel like just changing a cap to change a filter cutoff is "too easy" or something.  Like, that has to affect something else, no?

Changing resistors WILL "affect something else". DC bias. Impedance relationships.

Changing a mid-band capacitor pretty much does what it says.

Changing a 400Hz filter to 40Hz may interact with other bass cutoffs.

If caps are used in pairs/trios (as this plan), change all caps of a group the same ratio.

If filters are in high/low pairs, as in a crossover, you usually want to adjust *both* filters the same way. Occasionally you may want to "spread" them for a dip. But that's usually better done with a proper mating crossover and a dip elsewhere in the system.

> That Guy, but... , that's all you.

Points noted. You must have heard me play. Offense taken with glee.