## Frequency separator

Scope and XITE Development

Original topic on PlanetZ: https://forums.scopeusers.com/viewtopic.php?t=4203

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Posted: Mon Feb 11, 2002 8:12 pm
by eliam
Would it be complicated to create a soft which would do the same job than an external cross-over? It would have to be able to precisely separate the frequencies and assign each of the spectrum zones to different outputs...
This would be great, because professional quality cross-overs are somewhat expensive... And in this way we could easily have 3 way amplification for an unequaled resolution...

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Posted: Mon Feb 11, 2002 9:35 pm
by jabney
You can create a crossover using tools supplied with Pulsar and a free download called "Multi Speaker" (it appears to call itself "Speaker setup" once it's installed). Speaker setup accepts a stereo pair and sends three stereo pairs - this gives you level control (and muting) for each band of the crossover. (The device was posted on Planet Z 6-14-1999 by "Anonymous - posted as Michael Miller" - thanks Michael for a very useful device! Cool for zoning too.)
To create the low-pass (i.e. bass) section, route one of the three pairs from speaker setup through a High Cut filter on each channel. Cascading the 12dB per octave filters will give you a steeper slope. Two in series approximate a Linkwitz-Reilly (sp?) filter for instance. The high-pass (i.e. treble) section is created similarly but with Low Cut filters. The band-pass (i.e. midrange) section uses both High Cut and Low Cut filters.
Add a simple delay on the mids and highs if you want to get really fancy. Just remember to watch your DSP load as you build. Simpler is better - as long as it does the job. When I built a crossover (pre 3.0), I did not have the stereo filters available, but I would think they should work.

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Posted: Mon Feb 11, 2002 9:47 pm
by marcuspocus
Very interresting! So using a luna IObox, one could 'recreate' a 5.1 (6 out) pretty easily!
About that free plugin, i don't know about it, but i remember seeing a thing called 'Z Matrix' made by John Cooper (our great Z creator!) made especialy for this....

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Posted: Tue Feb 12, 2002 7:47 am
by eliam
Thanks for the tips...
Jabney, you propose to use two filters in series? Is there something like a "brick wall filter" which totally cuts with razor sharp precision above or below a certain frequency?
Marcus, you say there's a tool made especially for that... Can you retrace it?

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Posted: Tue Feb 12, 2002 9:04 am
by marcuspocus
I'm not sure it really doing what you want, but anyway, you can have a look, the thing is, it's not free at all
http://shop.creamware.de/shop2000/de/Sh ... es#TARGET0

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Posted: Tue Feb 12, 2002 12:01 pm
by at0m
There's Low and High cutters by Creamware, but I enjoy STW's the most. They're s t r o n g but not cheapo either.

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Posted: Wed Feb 13, 2002 8:55 pm
by jabney
Sorry I wasn't more precise in the first version of the posting. The level control device is called "Multi Speaker" and is currently on page 5 of the devices. It seems to call itself "Speaker setup" once its installed. I edited the posting to reflect that.
The Z Matrix looks like a very cool item, but it was not what I was referring to.

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Posted: Wed Feb 13, 2002 11:48 pm
by eliam
Atomic, you think that these filters could VERY precisely separate the frequencies? Are they sold on their own?

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Posted: Sat Feb 16, 2002 3:44 pm
by at0m
I haven't used frequency analysers, just my ears. I don't know if they're good enough to do X-over.
The VintagEQ is still for sale, I even think they're doing a V3 update The EQ's are 139$.
If you want, I could do some testing, let me know how you want me to do it.

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Posted: Sat Feb 16, 2002 5:47 pm
by eliam
Yes, that would be very appreciated... I just want to know if we could get rid of external separators and get close to the quality of electronic cross-overs...
Thanks for your selfless service!

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Posted: Sat Feb 16, 2002 6:31 pm
by at0m
I think I need to take a break.
There's no low pass in my STW pack.

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Posted: Mon Feb 18, 2002 8:44 pm
by jabney
eliam: I'm not sure what you mean when you speak of a sharp filter to 'very precisely' divide the frequencies. The most common slopes are 6 deciBels per octave, 12 dB per octave, 18 dB per octave and (my favorite) 24 dB per octave.
I suppose you could use a steeper slope, but why? If 24 dB per octave is good enough for BSS (Brooke Siren) crossovers, it's good enough for me. When I 'built' my Pulsar crossover, I used it in one system while I used a BSS (the 'cheapest' - but still very sweet) crossover in another system. They both worked.
To gain an audible improvement over either, I would have needed to get an XTA with FIR filters (which is another - albeit interesting - topic), and even then I'm not sure I would be able to tell much difference. (I've only heard the XTA with a VDOSC rig.) None of the crossovers I mentioned sounded nasty - including the Pulsar. I have heard crossovers which colored the sound in an unpleasant way, but they shall remain unnamed in this posting.
Have you built a Pulsar crossover yet?

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Posted: Mon Feb 18, 2002 10:32 pm
by eliam
I did not build it yet... I'm not an expert in the field, but I know that cross-overs in the best mixing rooms separete frequencies very sharply, and I was just wondering if we could get close to the precision of these units, without having to pay the thousands of dollars thay cost. I'm talking about high-end mixing environment here. The steeper the slope, the less leak of frequencies will occur between the amplified channels dedicated to portions of the sound spectrum, and thus the flatter the freq reproduction...
I've been in contact with someone who used to build electronic cross-overs, but I lost his track. I'll try to reach him and ask what he thinks about it... I'll let you know if I succeed...
In your opinion, what would be the steepest cutoff slope we can possibly create and how? (With software tools if possible).

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Posted: Tue Feb 19, 2002 5:36 am
by jabney
elian,
If you want to create a sharper cutoff, simply keep cascading high-pass or low-pass filters. But why? I named the two classiest crossover lines I know of - BSS and XTA - other than a dedicated speaker control system (e.g. EAW) and they do not exceed 24 dB per octave. Why? Consider that everything in audio represents a compromise of some sort. Remember, even the mildest 6 dB slope can introduce phase anomalies. The steeper you get, well ...
The classic slopes (6, 12, 18, & 24 dB per octave) are chosen for a reason - they work. Some slopes work better than others in some systems. It's your ears which should decide. In the case of the Creamware environment, we can work with 12 dB per octave slopes.
As for me, I would like to have 6 dB filters added to the menu because that would give the option of 6 dB and 18 dB slopes. However, other than as an experiment, I've never used anything other than 12 dB and 24 dB slopes.
Since it is so simple to build a crossover in the Pulsar environment, I suggest you try it. Other than some screen real estate and dsp cycles, you have nothing to lose.

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Posted: Tue Feb 19, 2002 7:13 am
by eliam
I'll try it out! Thanks for your help!

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Posted: Wed May 29, 2002 6:47 am
by kensuguro
I think I might as well build one in mod2. Should be very easy.
You got mod2 eliam?

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Posted: Wed May 29, 2002 7:30 am
by kensuguro
na, nevermind.. I tried using every single type of filter in mod2 but none of them have a proper linear resonse. The all seem to be tweaked to sound musical, so I can't make an accurate crossover with these filters. I guess they're modeled to sound "analogue-like" and not meant to be used as digitally precise filters. (unlike standard Pulsar filters?)
Anyone care to make an accurate "no-cheese thankyou" multimode filter for mod2?

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Posted: Thu May 30, 2002 4:39 pm
by celmo
you could try this simple one:
http://www.celmo.com/Download/CrossoverCelmo.zip
(it's for free...)
celmo