Multi-band compressors: Let's split!

[Mark Hammer]

In the What Compressor, there is some interesting filtering in the path to the peak followers.

Yes, but the What ends up with all of that sidechain governing a single LDR for the entire spectrum.  It IS a much more "intelligent", if you will, rectifier in terms of how it handles the spectrum, and comments from users indicate that voice-processing benefits from this, but ultimately, the gain/level reduction is applied monolithically.  Note that, while the amount of harmonic content in the otherwise unprocessed voice is essentially under the control of the user, and subject to remarkable constancy over the lifespan of any held note, the plucked string has a VERY short lifespan for harmonic content, and that is the fundamental challenge to design of any pleasant-sounding guitar compressor.

I've always thought that the Old Testament could benefit from significant compression and noise reduction.

Many biblical scholars think it was an exercise in band-splitting and separate processing already.  It's the folks who treat it like an EHX or MXR "one-knob wonder in a standard box" that I worry about.  Other folks worry that its "current consumption" has declined in recent years.  There's lots of internal tweaking that some folks tend not to think about.

Anyways, let's skip the OT humour stuff here, and stay on track with respect to compression.

Question to ED-1 owners/users: Do you find the tone-control-like adjustment of rectifier properties makes the unit behave better than what you've experienced with other compressors?  I'm wondering if a single linear pot, with wiper to ground, could be used to adjust the relative "drive" to separate hi/lo sidechains (which presumably are tailored, in fixed manner, to optimal properties for their band).  Again, the goal is to have something more tailored than a Dynacomp or Anderton, but not as compicated as the Trace-Elliot or a DBX unit.

[John Lyons]

oops!

[John Lyons]

Funny how this thread is discussing compressors and the bible. Kind of cool the duality

"I've always thought that the Old Testament could benefit from significant compression and noise reduction."
Nice one!!!

John

[markm]

I've always thought that the Old Testament could benefit from significant compression and noise reduction.

[Ben N]

Just to get back ON topic, I have and like an ED-1, but I don't find the emphasis control makes much difference in use.  Whic is surprising, I guess, because in general I find it to be rather flexible--worlds better than the only other comp I have used, a Dynacomp.  I confess, though, that I am not that much of a comressor user.
Ben

[Mark Hammer]

Seems like the easy/cheap attempt at a start towards this would be to grab a couple compressors (I'm sure many of us have built both a Squeezer and a Dyna/Ross Comp, and isn't there a Dano compressor from the really cheap mini line?) and throw together something like the front end of Anderton's quadrafuzz, send the frequency split outs from that into the compressors and then mix 'em back together and see what you get.   /quote]

Actually, there was a project (with schematic but no layout) in POLYPHONY in 1982 or so by Thomas Figuerdo I think, called "The Penultimate Compressor" that used band-splitting and an NE572 compressor chip (remember when you could just BUY them at Radio Shack?).  I may have scanned it.  I'll have to check at home tonight.

Steve Ritmeyer has a nice compact board for a dual Orange Squeezer over at his U-Stomp site: http://www.ustomp.com/index.html?menu=2&section=13  That, plus a simple highpass/lowpass filter and passive mixer circuit, could form the basis for some interesting experiments.  Especially if one has adjustable gain in the  OS op-amp, and variable decay.

[StephenGiles]

http://www.4shared.com/dir/1321731/a7e7124c/sharing.html

Look at CClark synth 1 drawing 3 for a 2 transistor VCA which might be useful for several channels of multiband compressor. Alternatively, and more flash is the SSM 2164 quad VCA, or even more flash is a hand of CA3094s

[markm]

Steve Ritmeyer has a nice compact board for a dual Orange Squeezer over at his U-Stomp site: http://www.ustomp.com/index.html?menu=2&section=13  That, plus a simple highpass/lowpass filter and passive mixer circuit, could form the basis for some interesting experiments.  Especially if one has adjustable gain in the  OS op-amp, and variable decay.

This seems like it could be a great starting point for this project! 

[analogguru]

I don´t really understand the purpose of a multiband compressor on a (distorted) guitar signal.

If you are interested in existing multiband compressors, have a look at:

Telcom C4
(I think dbx had also similar stuff)

and

Aphex Studio Dominator (Model 700)

The crossover what I like the most, is a 24db-linkwitz-riley subtractive filter

I used it 15 years ago in active 4-way studio-monitors with Dynaudio chassis.
They sounded unique.  The studio owner, for whom I constructed this, got nearly crazy by listennig to club-live records. He thought he was sitting there.  Sadly he died in the meantime, and i don´t know what happended to this monitoring system - I would like to have them at home - but maybe it ended in the trash.

I used a similar configuration for a H&K 4-way disco-system prototype.
4 triple-chamber bass-reflex subwoofers (each 800 W), upper-roll of at 80 Hz !!!
the 4 top-units I believe were assembled with 2x 12", a 2" for High mid and 2 JBl treble-drivers.
The subwoofers were linear down to 20 Hz, lowest possible frequency 8 Hz.
You should have listened to Phil Collins´ "In the Air tonight"-remix of the late 80´s or Grace Jones "Slave to the Rhythm" or Robin S. "Show me love" ojn this system to get an idea what is: BASS

analogguru

[markusw]

Many thanks for those links.  The Trace Elliot pedal, aimed at amplification of acoustic guitar, from what I gather,

Sorry, I linked you to the wrong manual. Here's the right one http://britishaudioservice.com/inst/SMXPED.PDF   

The SMX comp is intended to be used for bass. It's also part of the various SMX bass amps. Interestingly, it seems to have the same specs as the acoustic comp.. 

Anyway, thanks a lot for your analysis Mark!

Markus

[Sir H C]

On the 'bay you can often find 4 band crossovers from old audio gear up for sale cheap as this is all done digitally now.  So, you could get one of those with the tweakable crossover points, and the rest and put the compressors in the output and a little mixer and have some fun.

[toneman]

Hey Mark,
surprised no one mentioned the Harry Bissel compressor....

much talk a while back about it on the SynthDIY pages...

here's a link (i think) to the EDN article---

http://www.edn.com/article/CA265499.html

can U say "multiband"??

err...   maybe it's more an EF than a compressor, but the multiband part is there...

[GFR]

http://www.4shared.com/dir/1321731/a7e7124c/sharing.html

Look at CClark synth 1 drawing 3 for a 2 transistor VCA which might be useful for several channels of multiband compressor. Alternatively, and more flash is the SSM 2164 quad VCA, or even more flash is a hand of CA3094s

Stephen,

I was able to download the compellor and CClark_synth_1.gif, but 4shared gives an error for CClark_synth_2.gif. Would it be possible for you to upload it again?

Thanks.

[StephenGiles]

How strange, I'll put it up again this evening.

[Mark Hammer]

Hey Mark,
surprised no one mentioned the Harry Bissel compressor....

much talk a while back about it on the SynthDIY pages...

here's a link (i think) to the EDN article---

http://www.edn.com/article/CA265499.html

can U say "multiband"??

err...   maybe it's more an EF than a compressor, but the multiband part is there...

Harry's IS one of the great envelope followers but it is really more oriented at having filters and other "events" track well without ripple.  If you split the spectrum to have faster time constants for the top, and slower ones for the bottom, ripple is less of an issue and, conceivably, even a shoddy old-fashioned half-wave rectifier can be adequate i tandem with, say, an LDR.

[Mike Burgundy]

I agree with analogguru on multibands on distorted guitar, although I can imagine some really "unnatural" sounds available with that, especially if you muck with attack and release times on each band.
That said: I do love multiband on drums and mixes in the studio (up to 5 bands - now that's luxury) and on bass too (3 bands is best for flexibility). This is a luxury however, but there's definitely goodies to be found, especially on bassists who mix styles a lot (fingerpicking on the neck and slapping near bridge in the same song, that sort of stuff).
I've actually thought of constructing something like this based on Jack's QD2 with some attack tweaks (I like the bottom end around 30-60ms, mid 20-30, top 15 or something. I never really look at the dials, rather tune by ear) but I backed off after some digging into crossover circuits. These get quite substantial quite fast.
I'm in the studio tomorrow, I'll see if I can take some settings down. Interesting to see how the theoretical approaches compare to (my, specific) taste. I do suspect it's probably hard to get something to suit most instruments, styles and tastes without a big bag'o knobs but who knows. Interesting, this.

[Cliff Schecht]

I've got a few NE571's, somebody get me a schematic to breadboard .

[R.G.]

but I backed off after some digging into crossover circuits. These get quite substantial quite fast.

There's a lot of parts there, but it's highly repetitive.

The active-crossovers-for-speakers people have been digging in that hole for a long time. For some good canned crossovers, check out the third order Linkwitz-Rileys at Rod Elliots page - sound.westhost.au.

[StephenGiles]

How strange, I'll put it up again this evening.

Sorry, didn't get done last night, I have written myself a note!

[StephenGiles]

How strange, I'll put it up again this evening.

Sorry, didn't get done last night, I have written myself a note!

This should be the link:
http://www.4shared.com/dir/1321731/a7e7124c/sharing.html

Yes, that works.