" Q " help !

[richluvsound]

Anyone,

Can someone explain what Q refers to ? I think I have a vague idea . Does it refer to a nattow band of FQ's above and below the actual FQ that one would specify when selecting a adjustment on a PEQ.
I realise this is an elementary ? , but thats me :o: Please ,Please keep it simple . Imaging your trying explain it to corpse on Valium !

Rich

[Hoerninger]

HIGH Q:
Like rough mountains with steep slopes - for example a notch filter.
LOW Q:
Like hills with gentle mountainsides - for example ordinary bass and treble control.

After this language experiment of mine I will go for a cold shower.
I hope you have time for a hot cup of tea . ;)
___________
Peter

[rs237]

hello rich,

my english its bad and peter hats already declared if it is not enough look here

http://www.adp-gmbh.ch/csound/filters.html

regards
juergen

[Robh3606]

Here's a quick visual. Those are the voltage drives for 3 notch filters at 1K. The Q's are 20, 10 and 5

Rob:)

[Ian Mackenzie]

Q was in James Bond Movies

[boputnam]

Can someone explain what Q refers to ? I think I have a vague idea . Does it refer to a nattow band of FQ's above and below the actual FQ that one would specify when selecting a adjustment on a PEQ. Slowdown, cowboy...

What is "FQ"...?

Q is a measure of a filter's bandwidth. Q is dimensionless, but always, higher Q values = more narrow (precise) filters. Juergen has it - try this on Filter's Q (http://www.adp-gmbh.ch/csound/filters.html). :applaud:


Here's a quick visual. Those are the voltage drives for 3 notch filters at 1K. The Q's are 20, 10 and 5So, in this case...

Black is Q = 20
Green is Q = 10
Purple is Q = 5

[boputnam]

The Q's shown here are in units of octaves.

[richluvsound]

:banghead::banghead::banghead::banghead::banghead: :banghead::banghead:

I have been pissing around with this thing all ______ day I'm going on a nasty site for some relief ......... Ian , go forth :biting: XX.


I can't get it save the eq settings.

I hate Bill Gates ! I set the xover slopes save to PDC then set the EQ and then what ?

Dumb Fck

[richluvsound]

Here's a quick visual. Those are the voltage drives for 3 notch filters at 1K. The Q's are 20, 10 and 5

Rob:)

It refers the speed of the filters effect; The higher the Q the quicker , the lower the slower. ?

thanks Rob, pictures have always been the way I learn, that and being shown,
sometimes more than once !:p
Rich

PS. I think widget and ken should get their Deqx out for me !

[cooky1257]

It refers the speed of the filters effect; The higher the Q the quicker , the lower the slower. ?

thanks Rob, pictures have always been the way I learn, that and being shown,
sometimes more than once !:p
Rich

PS. I think widget and ken should get their Deqx out for me !

Not so much the speed as the sharpness.....
Cooky

[readswift]

high Q steep filter can easily self oscillate , then you sense the so called "ringing" . In fact every filter above 3rd order ( 18db / Oct) used to ring , I read this in a Burr Brown paper. _Linear phase_ digital filter is different animal it has ringing before(!!) AND after the transient (first millisec of a drumhit for example) , so I'd advise to use max 18-24 dB / oct linear phase filters.
If you want steeper filters, use the "minimum phase" filter setting , that has no pre-ringing.

[UreiCollector]

http://en.wikipedia.org/wiki/Q-factor

this link may be helpful.

the part that will interest you most is the equation.....

delta F = F0 / Q

So therefore with a frequency of 50hz and a Q of 2, the 3db down points (half power points) will be at 37.5hz, and 62.5hz.

At a frequency of 50hz and a Q of 5, the 3db down points (half power points) will be at 45hz, and 55hz.

Notice that as q goes up, the effect of the filter becomes sharper, and as q goes down, the effect becomes broader.

Hope this helps.

[boputnam]

The Q's shown here are in units of octaves.


It refers the speed of the filters effect; The higher the Q the quicker , the lower the slower. ?No.

Think of Q as bandwidth.

For the image you posted, Q is in octaves.
0.5 = 1/2 octave
2 = 2 octaves
etc.

When expressed in octaves the higher the number the wider the Q.

If you want a broad filter, use 3 octaves.
If you want a narrow filter, use a fraction of an octave, say 0.5 (or 1/2) octave.

[boputnam]

I'll try to display "Urei's" points for you...


So therefore with a (filter centered at a) frequency of 50hz (with) a Q of 2, the 3db down points (half power points) will be at 37.5hz, and 62.5hz.

37.5 Hz (lower limit of filter, at -3dB down point)
50 Hz - center freqency of filter
62.5 Hz (upper limit of filter, at -3dB down point)


At (filter centered at) a frequency of 50hz (with) a Q of 5, the 3db down points (half power points) will be at 45hz, and 55hz.

45 Hz (lower limit of filter, at -3dB down point)
50 Hz - center freqency of filter
55 Hz (upper limit of filter, at -3dB down point)

You see? As Q increases, the bandwidth of the filter narrows.

Refer to Rob's post #4 (which he has since exaggerated the gain! :coolness: ).

The filter is centered at 1kHz.
In all cases shown the gain is -14dB down.
The only thing that varies is the bandWIDTH of the filter.
The Q varies the bandwidth of the filter's impact.
Q = 20 is Black (-3dB down bandwidth is 50 Hz, from 975 Hz to 1.025 kHz)
Q = 10 is Green (-3dB down bandwidth is 100 Hz, from 950 Hz to 1.050 kHz)
Q = 5 is Purple (-3dB down bandwidth is 200 Hz, from 900 Hz to 1.100 kHz)

[boputnam]

Here's an image from a simple spreadsheet, showing the examples of Rob and Urei...

[Earl K]

Refer to Rob's post #4 (which he has since exaggerated the gain! ).

The filter is centered at 1kHz.
In all cases shown the gain is -14dB down.
The only thing that varies is the bandWIDTH of the filter.
The Q varies the bandwidth of the filter's impact.
Q = 20 is Black (-3dB down bandwidth is 50 Hz, from 975 Hz to 1.025 kHz)
Q = 10 is Green (-3dB down bandwidth is 100 Hz, from 950 Hz to 1.050 kHz)
Q = 5 is Purple (-3dB down bandwidth is 200 Hz, from 900 Hz to 1.100 kHz)
http://audioheritage.csdco.com/vbulletin/attachment.php?attachmentid=31572&stc=1&d=1205713495



- Though it's tougher to see due to the use of the Log Scale in Robs' pic / the quoted "Q"s given for the Linear X pic, don't actually jive with the "Q"s one derives ( for the three notches ) / when using Fredericks' defination of electrical Q ( which, is in agreement with all my textbooks ) .
- FWIW, I see Qs' of @ 5, 2.5 & 1.25 using the classic textbook method .

- Something is amiss .

- Things appear to be off by a factor of around 4 .

:)

[richluvsound]

OK, so the lower the Q ,the wider the affected bandwidth. I can see it happening went I alter the Q .

I guess this is what makes the PEQ far more powerful than a graphic EQ .
Next Question, Is there a graph somewhere that shows the normal frequency
of various musical instruments . I can here things going on ,but it would really helpful to be able to go straight to the offending Q and Frequency.

Thanks for all the help so far. At this rate I'll be working at the Abbey Road this time next week !:p

Rich

[Fred Sanford]

I guess this is what makes the PEQ far more powerful than a graphic EQ .
Next Question, Is there a graph somewhere that shows the normal frequency
of various musical instruments . I can here things going on ,but it would really helpful to be able to go straight to the offending Q and Frequency.


There are some GEQs that have less of the phasing issues, but I haven't yet used them- others here have posted about them. PEQs are more precise and more versatile in my experience, both in live PA work and home or club systems. GEQs (as you've noticed) are a of an bit easier concept for most people to grasp, the spectrum is laid out & visible. I use GEQs on instruments to shape sounds all the time, though, different needs and different approach.

I think you're looking for a shortcut, and I'm just going to tell you there isn't one, really.

Here's more than you need to know about the ranges of differing instruments, but keep in mind that this seems to represent the fundamental musical notes that the intruments produce, not the overtones and real-life range of frequencies that you hear and associate with an instrument...including the reverbs and such. Your voice's range may be a baritone, but the "breathy" sounds and sibilance and other aspects won't fall into the "baritone" range...make sense?

http://www.listenhear.co.uk/general_acoustics.htm

Chart is Copyright © 1980 by Hachette Filipacchi Magazines, Inc. Reprinted from Stereo Review, April 1980.

[boputnam]

...I guess this is what makes the PEQ far more powerful than a graphic EQ...That is part of it.

Another is the exact choice of filter center frequency (vs typical 1/3 octave in GEQ).

[JBL 4645]

HIGH Q:
Like rough mountains with steep slopes - for example a notch filter.
LOW Q:
Like hills with gentle mountainsides - for example ordinary bass and treble control.

After this language experiment of mine I will go for a cold shower.
I hope you have time for a hot cup of tea . ;)
___________
Peter


The Hills are alive with the sound of “Q”.

I couldn’t resist that one.:D

I like the benefits of what Q offers with EQ on the DCX2496 and BFQ2496 over the other dinosaur EQ’s that I have. Takes a lot of practice too shape or morph the frequency curve into a near flat frequency response. Is that not correct?


By widening the Q at specific frequency of user’s choice does this not expend that practically frequency to play wider in bandwidth such as loudness or if it was narrowed along with reducing the db level make it play softer in loudness?