# Adjusting Q



## snowplow (Jul 20, 2009)

Hey guys, I just gotta new (to me) pioneer deck and I forgot how adjustable they were.

So I have an adjustment for Q. 

The definitions I found for Q are: 

"In a bandpass equalizer, the ratio of center frequency to bandwidth."

and Q-Factor

"A measure of the sharpness of resonance."

So basically I was going to zero out the amp and use the deck to do all my amp tuning ect. So for the Q adjustment, do I need to know anything specific or do I just put it where it sounds best to me?

Just asking because the above definitions are a little hard for me to grasp.

Thanks!

DC


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## snowplow (Jul 20, 2009)

Just found this. I think I got it. 

JL Audio - Car Audio Systems


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## dolbytone (Jun 30, 2010)

What Q setting you use depends on the width of the band you want to cut or boost. If for instance if you have just one band that is offensive like 2K, and the 1.6 and 2.5 bands are fine as they are, you'll want to use a narrow Q to affect 2K and the surrounding frequencies as little as possible. If you have a hump of several frequencies in a row, you can widen the Q and boost or cut them in a group using the frequency setting as the center point. So, it's just situational depending on what you need.

Here's a video that quickly goes over parametric equalization:

YouTube - How to Use Parametric EQ Like a Pro


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## snowplow (Jul 20, 2009)

Awesome thanks! So it looks like you might be able to use the Q factor to make something sound warmer (wide) or more clear (narrow) for instance. Cool!

What kind of music do you use to tune your system? Do you use a test CD over the normal music you usually listen to? 

In my head it seems like you would want to use music you normally listen to but maybe pick one with the widest range of sounds or instruments.


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## nineball (Jan 17, 2008)

snowplow said:


> In my head it seems like you would want to use music you normally listen to but maybe pick one with the widest range of sounds or instruments.


bingo. much easier to tune using something you are familiar with.


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## snowplow (Jul 20, 2009)

Awesome thanks!


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## dolbytone (Jun 30, 2010)

Before I EQ, I use a multimeter to set amplifier gains. After that I use pink noise to tune out the nasty spikes and dips using an RTA. I only have 3 parametrics on my head unit and I use them all up doing that so I don't really do any further tuning on my current system.

After I finish I put in a mixture of music I am very familiar with to make sure it sounds like it should. I prefer music that has a lot of space to it so it is easy to pick out the quality of voices and instruments for making small adjustments. Here's a short list of songs I use.

Fast Car - Tracy Chapman
Eric Johnson - Forty Mile Town

Midnight Star - No Parking on the Dance Floor
Queensryche - Della Brown
Nu Shooz - I Can't Wait
Chaka Khan - Ain't Nobody

And when I'm done with all that, I stick in a copy of Master Plan by Dave Weckl and crank it up. Here's the best cover I could find on Youtube:

Cover of Dave Weckl - Tower of Inspiration


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## snowplow (Jul 20, 2009)

Great thanks!

So I have been reading about Slope. It sounds like it might be the same as Q.

So is the slope of the crossover the same as adjusting the Q Factor?


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## dolbytone (Jun 30, 2010)

No. Q is selecting a band's width to boost or cut in a parametric EQ. Slope refers to how steep you want your crossover to roll off. It is not part of equalization. When you select a crossover point, the crossover can't just cut everything out below/above the frequency you select. What it does is filter those frequencies gradually. When you choose slope, you are selecting how steep the roll off is.


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## snowplow (Jul 20, 2009)

Ok gotcha. So slope is an initial amp setting (or possibly on the deck too) but the Q setting is for fine tuning at the end.

Thanks


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## snowplow (Jul 20, 2009)

Do you think you could give me an example of when you would want a high slope vs a short slope or vice versa?

Seems like a short slope (low number is what I mean) would be better because there would be less overlap and I think less of a volume increase.

Also what does '_flat_ to 60 db' mean?


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## dolbytone (Jun 30, 2010)

I don't know what "Flat to 60dB" means, I would have to know the context before I could answer.

High slope vs. low slope, I guess the obvious answer would be a situation where you are running a high pass filter for door speakers that are rated for 60Hz - 22kHz and you are wanting to snug up the crossover point as closely to that as possible because maybe that gives you better articulation for bass guitar notes or something like bass drum attack. You would want to set the crossover high pass point close to 60Hz and use a high slope so the bandwidth you are actually sending doesn't extend very far below that.

Or, say you want to crossover higher than 60Hz but you still want your door speakers to integrate with what the sub is doing so your sub isn't pulling the sound stage behind you in the lower frequency range, you could set your HP crossover to 80Hz and use a more gradual slope.

I have actually heard something else before, when I was tuning my sound system and messing with slopes and crossover points. I was listening to something that had a really snazzy bass line and I could actually hear the bass moving between my subwoofer and door speakers, with a gap in the middle where the notes were diminished and parts of it were inaudible. In this case I was using a crossover point that was entirely too high, and the slope was insufficiently tapered causing a gap in frequency response of the system.

What slopes and points you use is more determined by the speakers you are using than anything else. There is a little wiggle room for when you are trying to get good integration but you should certainly know the hard limits before hand.

Also be aware that your chosen slope can affect phasing. I think it is generally a 90 degree shift for each order of slope (6dB/Octave). If you are experiencing huge phasing anomalies you can change settings on your slope to somewhat alleviate the situation, but keep in mind this is not the only thing that can affect speaker phasing.


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## snowplow (Jul 20, 2009)

Hey thanks for all the information. That makes a lot of sense. I started tuning it all a bit last night so it helped to understand what you are saying.

By the Flat comment all I meant was that I hear guys on here say they want speakers to play flat to a certain db point but I dont really know what that means. 

How would you determine the hard limits of your stuff? Is there a rule of thumb?

What I have is a home brew 3 way setup. My old MB quart 2 way tweeters and mids (4") and I added 6.5 Focal polyglass midwoofers and swiss audio 3 way crossovers. Just to give you an idea what I am working with.

BTW my pioneer deck has a bunch of Q factor adjustments in 16 different frequencies. I can boost the level from 0-2 and go into a narrow q pattern or wide.

Just curious if there was a 'normal' baseline to start with? Like for example 0-Wide. Kind of like starting to tune with your EQ zero'd out.


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## dolbytone (Jun 30, 2010)

Hard limits are determined by the frequency response of your speakers. If you have a driver that's rated by the manufacturer for 3.5kHz - 20kHz then you wouldn't want to pass anything under 3.5K to that speaker or you risk damaging it. Also it's pointless to pass frequencies to a sub that it cannot reproduce.  Consult your speaker manuals and spec sheets to find these numbers.

So for a 3 way system example (these numbers don't imply anything about your setup):

High: 3.5kHz - 20kHz - High pass somewhere around 4kHz.
Mid: 80Hz - 4kHz - Band pass somewhere around 80Hz to 4kHz.
Low: 35Hz - 300Hz - Low pass somewhere around 80Hz because of your mid setting.

Now, I'm not sure you entirely understand the parametric EQ stuff so here's a quick explanation. There are 3 controls for each parametric EQ.

Frequency: Selects the center frequency you want to adjust.
Q: Selects the width of your adjustment around the center frequency you have selected.
Boost/Cut: Raises or lowers the frequencies within the Q range around the center frequency you have selected.

My Head unit has 3 parametric EQs. One for High, one Mid and one Low. There are several frequencies within each section that I can choose to equalize using the parametric controls. So, for low my options are something like 60Hz, 100Hz, 200Hz. For Mid my options are something like 500Hz, 1kHz, 2kHz. For High my options are something like 4kHz, 5kHz, 10kHz.

I can only select one center frequency for each range, Low, Mid, and High. I cannot equalize them all. Once you select your center frequency, the Q and Boost/Cut controls affect that frequency. If you adjust 1kHz for example, and then move the frequency setting to 2kHz, you are essentially undoing your EQ to 1kHz and moving those settings to the 2kHz center frequency.

The only time this sucks is when you have a spike at 1kHz and 2kHz but the frequencies between them (1.25kHz and 1.6kHz) are low. In this situation you have to choose which one sucks the most and kill it using a narrow Q. If you widen the Q to cover the bandwidth around 1kHz and 2kHz and cut it, you are killing the stuff in between which should really get a boost and you have chosen the greater of two evils.

If you have a hump of frequencies you can cut them all by setting the right Q width around the center frequency the hump exists. So let's say 800Hz, 1kHz and 1.25kHz are a bit nasty, you would set your F to 1kHz and your Q to 1 octave and cut them all at the same time. If you are flat except for 1kHz then you want to narrow the Q so you are only cutting 1kHz and affecting 800Hz and 1.25kHz as little as possible.

The only really positive way of knowing WTF to do though is to use an RTA and measure the frequency response of Pink Noise. Otherwise you are simply guessing and messing around with it until it sounds good to you.

This brings me to that comment about flat to whatever. If you have an RTA and are playing Pink Noise, you can see if you have frequencies reproduced in your system that are higher or lower than the average of everything else (spikes and dips). It is desirable to get a flat frequency response as much as is feasible. For instance movie theaters, if properly tuned have a flat frequency response between 100Hz and 2kHz +/- 3dB (sometimes you can't get it that good but it's the target). After 2kHz there is a roll off of 2dB per octave and subwoofer is typically set 10dB above the center channel average for digital sound track reproduction, and flat for analog. This is how the movie sound track engineers expect the auditorium to be when they mix the movie so if it's not set that way their movie won't sound like it should, or like they think it will. It's a concept called Faithful Reproduction and that's kind of what that THX crap is all about.

Car audio isn't stringent like that though. Really the goal is to please yourself, not some movie production snob. A good starting place though is flat, and you can make adjustments from there as you feel the need. Usually flat means there won't be anything painful in the reproduction... you know how it doesn't sound so loud when it sounds really good. That's because your ears aren't getting stabbed by some offending wayward frequency and you can enjoy it more at higher volume. Sometimes though you have to come to the realization that some recordings just sound like **** and there's no tuning in the world that will fix that, or if you try, you will be screwing it up for all that other stuff that was well recorded.

I do think that an overall goal of both disciplines is to accomplish your goal with as little equalization as possible. It is true that you can have a flat response on your RTA but you've tweaked the EQ so much that you've actually introduced distortion into the system by overly manipulating the waveforms. A gentle EQ will get you better results in the end.


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