Ok, brainiacs, let's see what you've got...

Hehe, sorry for the thread title, but you guys know way more about electronics design than I do...

Couple of questions:
1] is it possible to implement linear phase crossovers in the analog world?
2] What sort of (if any) circuit could take a transient and essentially 'slow it down', slew rate limiting, maybe? At the same time, could said circuit also generate some harmonics to soften said signal further?

I know these questions are vague, but I'm going somewhere with this, and before we dive into ideas of how to approach the issue I want to deal with, I figure knowing these things will help me formulate my further questions.

THANKS!

1] is it possible to implement linear phase crossovers in the analog world?

Click to expand...

If you by "linear phase" mean delayless, then the answer is no.

2] What sort of (if any) circuit could take a transient and essentially 'slow it down', slew rate limiting, maybe? At the same time, could said circuit also generate some harmonics to soften said signal further?

Click to expand...

You'd need to define what you mean by 'slow it down'..

Jakob E.

is it possible to implement linear phase crossovers in the analog world?

Click to expand...

Exact linear phase is not possible. But it can be approximated. It's rather a question of effort you want to put in.

What sort of (if any) circuit could take a transient and essentially 'slow it down', slew rate limiting, maybe? At the same time, could said circuit also generate some harmonics to soften said signal further?

Click to expand...

As you said, anything with low slew-rate will do. In addition to this, tubes, transformers and analog tape is very likely to have similar effect.

And all of them will distort and thus generate some additional harmonics.

Samuel

Check out this paper by rane for some crossover overviews.
http://www.rane.com/note147.html

Here are some papers by the guys who make digital crossovers:
http://www.lake.com.au/proaudio/white.htm

You should be able to get close to linear phase crossovers in the analog domain. You will get a uniform delay over the whole audio spectrum.

[quote author="gyraf"]

2] What sort of (if any) circuit could take a transient and essentially 'slow it down', slew rate limiting, maybe? At the same time, could said circuit also generate some harmonics to soften said signal further?

Click to expand...

You'd need to define what you mean by 'slow it down'.[/quote]
That's not technical enough for you?

Haha, sorry. You have to remember that I'm an idiot...

Basically, here's the scoop. Digital recording (primarily cheap digital, but most all of it in general) sounds too transient to me. Not going to argue accuracy here, I simply prefer the distortion that analog tape and such add - one of those being that analog tape (and some processing) seem to limit the slew rate, the transient response, compared to digital...

To give you the idea of what I'm thinking - how difficult would it be to design something that had a variable crossover point above which everything would be variably limited in it's transients (speed) and at the same time, would allow adding some coloration to 'soften' transients. Not looking for a tape emulator, just curious about pursuing a box that would help me treat many of the analog recordings I deal with daily...

[quote author="bblackwood"]how difficult would it be to design something that had a variable crossover point above which everything would be variably limited in it's transients (speed)[/quote]

Not too hard, it's been done before - it's called a multiband compressor.

Peace,
Al.

[quote author="alk509"]Not too hard, it's been done before - it's called a multiband compressor.[/quote]
Thanks, but that's not what I'm looking for...

Hi Brad,

I've been staying out of things for a while but for you I'll stick my nose in.

Why are people always focused on the crossover passive or active when the driver hanging off the end of it all and the mounting position is often of greater consequence.

Take the time to look at the driver response AND the phase response together. You can plot these on the same graph. Group delay and overall group delay for the system is also worth looking at.

here is a tip
get a el cheapo B digital crossover and sit back and have some fun experimenting.
... I was told the old one has some better features BUT the new one looks cool too and may be simpler to use.

you may learn something

[quote author="Kev"]I've been staying out of things for a while but for you I'll stick my nose in.[/quote]
You're opinion is always welcome, Kev!

Why are people always focused on the crossover passive or active when the driver hanging off the end of it all and the mounting position is often of greater consequence.

Click to expand...

I am because I don't want anything coloring the signal any more than it has to. I mean, the GML 9500 has lower distortion than my speakers (which are pretty stunningly low distortion on their own) yet I could hear the 9500 with no boost or cut applied...

I appreciate what you are saying, but I certainly don't want any coloration that isn't necesarry or intended added. Maybe a good xover will work fine in this app, I dunno, but I'm always careful of adding gear to the chain that colors stuff unnecessarily.

Hey Brad, you finally received the GML. :thumb:
You promissed some pics.

chrissugar

Busted!

We like pictures!

Sorry, didn't like it and sent it back months ago...

Guess I'm stuck with my Sontec and Ibis until I find something else yummy.

Thanks, chunk. To be honest, I have tons of kewl tools for just this purpose (3 peices of Crane Song stuff alone with coloration available to fight it) and have tried virtually every combo over the years. This is why I'm curious about doing it analog, doing it with something in real time that works as you mentioned above. I imagine filters can be built that would be virtually (if not totally) inaudbile - the real trick is figuring out how to soften the top without making it mushy or dark..

hmmm sounds to me like your thinking of a multiband Transient compressor?

[quote author="pucho812"]hmmm sounds to me like your thinking of a multiband Transient compressor?[/quote]
Possibly. With added variable harmonic generation, something akin to the airbrush in photoshop - spreads the energy out to soften the 'image' without reducing overall energy.

Only needed on hi-freq, but MB with full variability would be fine.

No plug-ins necessary - want real-time hardware here.

Is this even possible? I dunno...

I think we have a breakthrough. :grin:

Hey brad,

it sounds like you require something similar to the variable risetime knob on the groovetubes vipre? I'm pretty sure this is like a slew rate control.

Anyone know how that works?

Maybe you could do as butta suggests with the filters (I thought low order bessel filters had linearphase response in the pass band?) and then run the topend through a harmonic generator of sorts, maybe something tubey? with slewrate control....in effect slowing the topend down a little?

Just a thought.......

Good luck

-Tom

Brad,

The problem here is that you do not specify what you mean by the subjective term "transient speed" or or the basis of:

Digital recording (primarily cheap digital, but most all of it in general) sounds too transient to me

Click to expand...

We can do almost anything in frequency/time/level domain if you can specify in unambigous terms what it is you need.

But I fear that what you're after is simply not that easy.

Try to elaborate on what it is you're after, and why.

Jakob E.

Maybe what you want (as far as I understand it) is actually not linear phase but the opposite.

Linear phase filters are used in digital audio mainly to make sure transients will "line up" again after filtering so transients will stay intact. The only problem with this is that the filters will have some delay (the delay is the same for all freq's ) and some pre-ringing that some people don't seem to like.

Not-linear phase filters will actually phase-shift the overtones that make up a transient in a more random way so the transient will get smeared-out more. It seems to me this is more like what you're after.
I read somewhere that in broadcasting they even use machines like this to even out transients and peaks so they can squash and limit signals even more without getting too much distortion.

So you'll need an analog filter with unity magnitude response and a phase response that is non-linear.

I could code you a vst plugin for that :twisted: but i have no idea how to make something like this with a soldering iron

You may be right, Mendelt. I know just enough to be dangerous...

Jakob, I don't know how to describe it technically. I just want to soften the high end - diffuse it, prehaps. I don't know how to get there from here, hoping you guys can point me in the right direction.

Do you really not understand what I'm hearing vs. what I want to hear?