## Graphical EQ like PEQ4 but with more bands?

Device/Module Wishlist

Original topic on PlanetZ: https://forums.scopeusers.com/viewtopic.php?t=30836

#### Graphical EQ like PEQ4 but with more bands?

Posted: Fri Mar 02, 2012 10:12 am
by asktoby
I'm currently using PEQ4 to calibrate my sound system, using a measurement mic and pink noise to measure my monitors in my room and applying filters to my signal chain to get a smooth response.
Because PEQ4 only supports 4 bands of EQ I am ending up daisychaining several of these modules together, which is cumbersome.
Is there a stereo graphical EQ that can support more than four biquads? e.g. a "PEQ-n", if you will!
I considered rolling my own in Modular, but the parametric and shelving EQs in modular are only mono, so I would have to make two parallel signal flows for left and right, and it would be a pain keeping them in synch!
Any suggestions?

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Fri Mar 02, 2012 11:14 am
by garyb
fix the room first.
fixing the speakers only leads to sadness. when you polish a turd, it's still a turd.
you could put another peq in series...

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Fri Mar 02, 2012 3:20 pm
by jksuperstar
I second Gary's comment. By using and chaining EQs to get a flat frequency response, you are destroying the phase relationships of those frequencies with each filter added. And phase plays the important part in creating a good sound stage during playback.
You'd be better hanging up a few blankets or foam on the walls to kill those resonant peaks and stray reflections instead.

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Wed Aug 15, 2012 10:40 am
by asktoby
An module to convolve the input with an FIR filter would be a good solution. Does such a thing exist for Scope?

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Wed Aug 15, 2012 12:33 pm
by dante
Theres DASGOST ConvolveQ

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Wed Aug 15, 2012 4:05 pm
by YISH313z
What about GraphEq?
Isn't this a Stock Device?

Attachments
    grapheq.JPG (67.4 KiB) Viewed 5235 times

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Wed Aug 15, 2012 4:59 pm
by Tau
Also Wolf's 8-band EQ
But fixing the room is better...

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Wed Aug 15, 2012 11:45 pm
by asktoby
Thanks for the suggestions, all.
I agreed that it's best to treat the room first.
The issue with the fixed-band EQs is that they don't have enough frequency resolution. e.g. GraphEQs has low bands at 20, 25, 31, 40, 50 63 and 80. With a mode at 70Hz there's no way to accurately address it. DASGOST has the same limitation.
With an FIR convolver it would be possible to perform very accurate linear phase EQ.
As a bonuse it would also be able to use impulse responses of real spaces and behave as a reverb!
There are even impulse responses available to download from the web for those who don't want to experiment with their own.
Take a look at http://convolver.sourceforge.net/ which does a similar thing in VST land.
I think this would be a great addition to Scope!

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Thu Aug 16, 2012 12:25 am
by tgstgs
i aggree on the fir but
what you show is fast convolution like convolveQ_ a fft filter which is a special form of a fir_
not useable for realtime just for mastering
with 65536 taps you have a latency of 65536 samples + the host latency_
but good marketing vibes

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Thu Aug 16, 2012 12:44 am
by asktoby
I've not tried convolveQ_ so cannot speak as to its latency.
My understanding of FIRs is that each sample is passed through with no latency (see h[0] path below)
Additionally, each sample is then delayed by one sample per coefficient, convolved with that coefficient, and then mixed with the output.
As such, there shouldn't be any latency!

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Thu Aug 16, 2012 1:02 am
by tgstgs
yes but that is NOT what you pointed to in the link__
this is a FFT convolution__ marked the way you might think it is a true fir_
there is NO WAY to process /multiply add/ 65536 taps even at 44k1Hz in stereo on ANY cpu avail________
maybe 2048 in stereo at the fastest cpus avail;
but then nothing else will run on that pc_
AND you will have dropouts_
as for the true fir df1 this is also only valid depending on the coeffs you use_
and sorry but the pic is not completly correct;
it should be z-1 z-2 to z-n
if z is the inputsample and -n the timeindex;
good vibes

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Thu Aug 16, 2012 1:21 am
by asktoby
Is there any way to implement a true FIR filter on scope? 1024 or even 512 taps would be sufficient I think.
I have the tools to generate coefficients to any tap length, and could just truncate them down to 1024 or whatever is feasible to run on Scope.
I have not developed for Scope so I do not know if this is possible with the SDK.

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Thu Aug 16, 2012 1:36 am
by tgstgs
basically it is possible with feedback and adds;
thisway you may get 128 taps on 1 old dsp;
but to get out the max of it you better code your own fir in assembler;
the dsps are made for this;
readout of sample AND coeff AND multiply AND add in 1 circle;
we have a 4096 prototype running on 1 new dsp with headroom at 44k1Hz
good vibes

Attachments
    FireQ_01.JPG (49.14 KiB) Viewed 5196 times

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Thu Aug 16, 2012 1:43 am
by asktoby
Thanks for the insights, tgstgs.
Looking forward to seeing the finished FireQ!

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Thu Aug 16, 2012 1:50 am
by garyb
it's all moot.
you can't eq a three dimensional space and have the curve be proper for all listening positions(each centimeter) anyway.
fix the room.
is it audio that you care about or computers? if it's audio, then handle it the correct way. eqs are used in the real world, but a good control room is eq'd in the design of the room. eqs are a last resort, or a bandaid. use computers for what they do best. fixing the room isn't one of those things.
or that's what my opinion is anyway...
i'm certainly nor discouraging anyone from making such an eq however, and you can be sure that the GHOST products are done by someone who cares about his work and KNOWS what he is doing and talking about.
anyway, the reason i'm so adamant is that i spent years trying to use eqs to fix my room. i used good stuff, too. i used hardware that had come from real working environments, White, Klark Technic, Urei, and Orban, but i could never hear the speakers properly. sure, i could measure the room response in a couple of places and get a sweetspot where i had dependable flat response, but i couldn't move much. also, the real problems weren't fixable via eq. even with excellent speaks and a measured "flat" response, the image was smeared and murky. there's more to hearing the system than perfectly flat eq of the system.
once i put up a few diffusers and a couple of bass traps things got a lot better. i removed the eqs and lo and behold, i was able to make good judgements based on what i could hear even though the rooms respose was far from flat. suddenly, i had an idea of what was really going on! the point of the rant is that it's better to fix the room a little and NOT eq the system at all, than to eq the room with the finest eq, but leave the room as it is.

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Fri Aug 17, 2012 11:17 pm
by dante

> tgstgs wrote:i aggree on the fir but what you show is fast convolution like convolveQ_ a fft filter which is a special form of a fir_
> not useable for realtime just for mastering with 65536 taps you have a latency of 65536 samples + the host latency_ but good marketing vibes

Would this be easier on the 2146X series Sharcs, w/ built in hardware accelerators for FIR, FFT & IIR filtering ?

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Mon Aug 20, 2012 12:35 am
by tgstgs
sorry i dont get the question;
4096taps on 1 new xite dsp = not possible with a dualcore cpu_
good vibes

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Mon Aug 20, 2012 10:37 am
by dawman

> tgstgs wrote: but good marketing vibes

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Mon Aug 20, 2012 1:21 pm
by dante

> tgstgs wrote:sorry i dont get the question;
> 4096taps on 1 new xite dsp = not possible with a dualcore cpu_
> good vibes

1 new xite dsp = 21369 Sharc.
I was asking if it would be easier on 2146X Sharc.

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Mon Aug 20, 2012 11:15 pm
by tgstgs
--
sorry there is no yes or no answer in my opinion_
it depends on more than just dsp specs_
as soon as there is a board avail and i have realized a filter for it i tell you_
good vibes

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Tue Aug 21, 2012 11:28 pm
by dante

> tgstgs wrote:sorry there is no yes or no answer in my opinion_it depends on more than just dsp specs_as soon as there is a board avail and i have realized a filter for it i tell you_
> good vibes

I saw EZKit Lite for them here :
http://www.youtube.com/watch?v=6rdda46N ... ure=relmfu
And a run down of features here :
http://www.youtube.com/watch?v=3xsq87CJ ... ure=relmfu
At 1:54 he speaks of the FFT, FIR accelerators.
They are made w/ extra heat resistance for automotive applications

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Tue Aug 21, 2012 11:51 pm
by garyb
i could be wrong, but i suispect that there's nothing surprising for Thomas there.
Dante! i think you're a candidate!

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Thu Aug 23, 2012 10:30 pm
by tgstgs
the ezkit is for sure nice if you want to build HW;
but people developing audioSW should get in touch with sc_
there is no better than xite_sdk avail atm.
good vibes

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Fri Aug 24, 2012 12:50 am
by dante

> garyb wrote:Dante! i think you're a candidate!

No way. To take up DSP programming even as a hobby, I would have to give away music, Scoperise and other parts of life to take it seriously. SDK alone wouldnt be enough I would need C++ and the experts are years ahead making already the devices I want.

> tgstgs wrote:the ezkit is for sure nice if you want to build HW; but people developing audioSW should get in touch with sc_there is no better than xite_sdk avail atm.
> good vibes

Agreed. But I was thinking of a future w/ some important parts of algos already built into chips that today must be hand coded.
It amazes me though that the most powerful of these chips end up in cars (automotive ??) - when they can do the blow away stuff that they do for the audio multitracking world, and that music world hardly takes much notice.

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Fri Aug 24, 2012 3:06 am
by tgstgs
_
sdk without coding /means creating your own atoms/ is more like a low level modular;
you do not have to be a coder to get some very good results with modular or sdk;
--
if you want to get deeper_
i would say codeing in c with some advantages of c++ for the stuff running on host cpu;
but the main stuff in xite is happening on the dsps coded in assembler;
--
mattomat f.e. would even run standalone all is running on the dsps_
all new dspcode hand coded btw.
you need the host cpu just for loading the code into the dsp AND for the GUI;
lets say you want to build a hw unit out of it;
you just need to realise a 1 dsp board with midiin/out and a hw controller for interfacing;
how is it called btw. a HUI HardwareUserInterface?
so mattomat could easy be implemented in any synth using sharcs
any manufacturer interested vibes?

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Fri Aug 24, 2012 5:56 am
by jksuperstar

> dante wrote:It amazes me though that the most powerful of these chips end up in cars (automotive ??) - when they can do the blow away stuff that they do for the audio multitracking world, and that music world hardly takes much notice.

Don't assume that! Cars use pretty basic processing, and minimal DSP at that (anti-roll/ABS really is the peak, engine tuning is basic microcontrollers). DSP is fairly "generic" in a sense, with some serious power available these days. ADI is one of the few that adds optimization for audio apps (Texas Instruments specializing in motor control and such). And if you do ever code with ADI (sorry, Analog Devices), their VisualDSP compiler is pretty incredible to use & visualize not only code, but your data...which for DSPs is important. Not to mention the DSP building blocks that come with the compiler. It really makes things easy on the programmer. (I played a bunch with a BlackFin a few years ago, and had an audio processor up & running in a few minutes, with the only misstep I had was needing to move from little endian to big endian ).
tgstgs, are you allowed to describe the tool flow at all? I'm curious what's involved with xite development down at the lowest level.

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Sat Aug 25, 2012 2:05 am
by tgstgs
tools????
any editor worx;
im using a personialized notepad++ for assembler;
is this what you mean vibes
are you developing??
edit and for sure no building blocks
but this goes more and more off topic__

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Sat Aug 25, 2012 10:31 am
by jksuperstar
No, not the editor. I use emacs and vi
I was thinking of the dsp compiler...if there is an API or library that SC provides for VisualDSP, or if they have their own tools that are part of the SDK (which my exposure to has only been with 5.1, and to me seems like a version of scope that allows lower level connections with atoms and writing out devices). But I'm thinking of the creation of atoms.
I would like to do development. not as full time, so I am wondering what investment of time I would need to get full development going, and what there is to learn before I can be efficient at creating scope devices and modular devices. The SDK for 5.1 was sparse regarding documentation, and also the number of atoms included seemed limited to what was available in the past. I only have xite, no pci, so going to an older version is not possible.
All good vibes!

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Sat Aug 25, 2012 11:35 am
by garyb
afaik, there is a LOT, more than most devices require, that can be done without EVER coding. SDK modules function like electronic components, or Scope modular....

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Sat Aug 25, 2012 11:49 pm
by tgstgs
learn?
check out the instruction set from analog devices_
time?
depends on your backround_
but check the instruction sets all answers are there_
talk with holger he is the lord;
if he says you are in i can give you examples of how to make dsp sys dll
if you need something special atom you cant live without and this thing is good for the platform pmme_
good vibes from vienna

#### Re: Graphical EQ like PEQ4 but with more bands?

Posted: Tue Aug 28, 2012 9:21 am
by jksuperstar
Part of the reason for me in investing in the XITE was the possibility for development at multiple levels. Wire studio, wire a modular synth, write DSP code. I like diving in, understanding, and creating at that low level. Need isn't the only drive. For me, curiosity sparks creativity, not to mention the "one thing leads to another" in the realm of happy mistakes and unexpected results.
I'll speak with Holger about the possibility of development at the atomic level.