" 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 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.

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

So, 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]

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

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...