NEW from La 67: LR4 VC Crossover

[lasesentaysiete]

I present the LR4 Crossover, a 3-way voltage controlled crossover in 6hp.

Modular Grid page

I have had this idea for a while now, so I decided it was time to go ahead and release it. It will be available in July for the price of 125€.

Proper demos and a user guide are still to come. Meanwhile, I welcome any questions or comments

[Foghorn]

Cool.
It is a VC XO
I could use this for Tri-amping my sound system?
but why do I need voltage control over XO?
or, how would I use it?

thanks

Maybe I could use it because my stupid Beh XO (2496) keeps burning out

[lasesentaysiete]

I could use this for Tri-amping my sound system?
but why do I need voltage control over XO?
or, how would I use it?

I suppose no one needs voltage control over a crossover

But it can be used to add movement during multiband effecting, for example.

Putting the LR4 between a power amp and a 3-way speaker could also work, but its not quite as elegant as some of Mr. Pass' offerings in that regard.

[lasesentaysiete]

I am happy to announce that Elevator Sound in Bristol will be carrying the LR4 (as well as the WFM).

Also, I will get around to some patch example videos of the LR4 next week.

[Stice]

I’ve wanted a voltage-controller crossover for years, this is great. I intend to use it to set up different processing chains on different frequency bands, but I’m sure I’ll find other uses too.

[lasesentaysiete]

I’ve wanted a voltage-controller crossover for years, this is great. I intend to use it to set up different processing chains on different frequency bands, but I’m sure I’ll find other uses too.

I’ve wanted one for a while, too. Multiband processing is often overlooked in hardware, I think.

[Foghorn]

So I could use this to "break out" three frequencies or frequency bands from a mono synth signal (or use 2 modules for stereo).
Then different processing could be applied to each frequency band.
.
That would be good for adding reverb to just the high band signal or a delay to just the baseline.
Or I could use it in my sound system where I have some presently non-used low range amp and speaker sets. (subs)
Place those speakers far away and add some verb to it. Cool
.
Now, I have to figure out what to use the voltage control for.
.
Of course, this is also a state variable (multi-mode) filter where you can sweep the cut off with a CV.
It just doesn't have adjustable Q (resonance).
In other words a LP, BP, HP filter like say Ripples or Joranalogue filter 8,
but without adjustable resonance so it is probably much cleaner sounding.
.
Exponential CV response, I wonder how well does it track the CV?

Foghorn

[lasesentaysiete]

Now, I have to figure out what to use the voltage control for.

I will make a few patch example video this week illustrating the use of CV over crossover frequency.

Of course, this is also a state variable (multi-mode) filter where you can sweep the cut off with a CV.
It just doesn't have adjustable Q (resonance).
In other words a LP, BP, HP filter like say Ripples or Joranalogue filter 8,
but without adjustable resonance so it is probably much cleaner sounding.

In theory, the Linkwitz-Riley curve gives a flat frequency response if the outputs are summed. So yes, using the LR4 as a conventional 4-pole LP, HP, or even a variable-width BP give a pretty clean sound (relative to the input signal).

Exponential CV response, I wonder how well does it track the CV?

It tracks CV at 1v/oct.

[Leverkusen]

Hey, looks great! Is it possible to move the crossover points out of the audible range? Like fading in an effect by frequency by moving the upper crossover point down into the actual sound.

[lasesentaysiete]

Hey, looks great! Is it possible to move the crossover points out of the audible range? Like fading in an effect by frequency by moving the upper crossover point down into the actual sound.

I am not sure I understand the question, so correct me if this does not apply

Both filters (i.e. crossover points) can sweep the entire 20-20k range, so it is possible to overlap the two filter and partially or completely eliminate a certain band. For example, if the low/mid crossover point is 1kHz, and the mid/high crossover point is 500Hz, there will be no output from the "mid" band.

[Leverkusen]

Yes, that's what I was thinking of.

Eliminating a band, patching it into an effect like echo and than slowly 'fade' it in again to let the echo come to full effect.

[lasesentaysiete]

Yes, that's what I was thinking of.

Eliminating a band, patching it into an effect like echo and than slowly 'fade' it in again to let the echo come to full effect.

Ah, ok. Yes, totally possible. For example, a variable-bandwidth bandpass is easy to patch because the CV inputs are normalled, and they each have an inverting attenuator. So, with one CV input, you can make one filter move up in frequency while the other moves down.

[Leverkusen]

Sounds interesting - doing the same just inverted on a second device would open up nice ways for spectral mixing and crossfading. Signals slowly appearing in the midrange of other signals and finally taking over the whole spectrum...

[lasesentaysiete]

Sounds interesting - doing the same just inverted on a second device would open up nice ways for spectral mixing and crossfading. Signals slowly appearing in the midrange of other signals and finally taking over the whole spectrum...

Well, about 2 years ago I had thought of using a circuit like the one in the LR4 in some sort of multiband processing module. I was thinking multiband compression, overdrive, plus a send/return in one module. Unfortunately, something like that would probably take up a lot of space. After a while I decided to just go ahead with the crossover portion, since any type of multiband processing starts with a crossover.

[BugBrand]

Nice little effect - a useful building block - & good you're working with Elevator Sound (just down the road from me).

[lasesentaysiete]

Nice little effect - a useful building block - & good you're working with Elevator Sound (just down the road from me).

Cheers. I am definitely excited to have La 67 modules offered at Elevator Sound.

The BugBrand crossover has always intrigued--and inspired--me. Along with the Cwejman, it got me thinking about VC crossovers for synths. As you say, a building block for processing audio.

[lasesentaysiete]

A few people have asked me for an explanation of how the circuit works. I am still preparing the official user guide, but below I have attached a crude version of the block diagram that will appear in that document.

Basically, the high pass output of the first SVF gives the "HI" band. The low pass output of the first SVF is input into the second SVF. The high pass output of the second SVF gives the "MID" band, and the low pass of the second SVF gives the "LO" band.

[lasesentaysiete]

The preliminary "User Guide" is now up on my website: LR4 Crossover User Guide

As always, any questions or comments are welcome

[nomass]

Seems like you could use this to — kind of — split out individual bands from a Cwejman Res 4.

[lasesentaysiete]

Seems like you could use this to — kind of — split out individual bands from a Cwejman Res 4.

I suppose you could try, but the Res-4 would have 4 "bands". The LR4 only has 3. You would also have to dial in the CV gains for each module pretty accurately. Not impossible, but it could get complicated. Cwejman has a 4-band crossover module. I have never used it and am not sure if its actually available, though.

[nomass]

One of the problems with the res 4 is that it doesn’t have individual outs per band. Seems like you could get three of them out with this. That sounds pretty good to me.

[starthief]

This is pretty neat. I can think of all kinds of uses for a crossover in modular.

[pekbro]

Definitely cool and on my radar.

[lasesentaysiete]

I am still working on some more illustrative demo videos, but I have a few audio clips in the meantime. First up:

La 67 LR4 Crossover transparency test #1.

The initial clip is the original sound source (noise).

The second clip is the same noise source run through the LR4. The HI, MID, & LO outputs of the LR4 are then summed.

During the second clip, I sweep both crossover points through their full range, and then I eliminate them one at a time.

[lasesentaysiete]

Here is the same exercise, but done using a more "real world" audio clip. Description:

La 67 LR4 Crossover transparency test #2.

The initial clip is the original sound source (sequence).

The second clip is the same source run through the LR4. The HI, MID, & LO outputs of the LR4 are then summed.

During the second clip, I sweep both crossover points through their full range, and then I eliminate them one at a time.