Low Res Freq and speaker EQing

Jeff B

Jeff B

Inspired
Hey everybody! So, I know everyone is busy drooling over FW18b, but I just have a question that I'm hoping some of you more experienced users can help me out with. It involves the LF, HF and EQ settings.

Before moving over to the AFX, I've never really had to deal with changing Hz settings for my cabs or anything of the sort or really doing much EQ'ing in general, since you found a cab with the speakers you liked and just went with that... for me anyways. I always used Greenbacks. Now, I've been experimenting with FRFR and the NL212 cabs recently and I found some postings of the EQ adjustments that are necessary to help calm the high frequencies and such that are inherent in the cab. Also, some guys are messing with lowering the Hz to 85Hz. Something to do with the cabinet frequency, etc. I've never been really good at understanding all of those things and I'm wondering if any of you have any good advice to help me learn more of why I would want to change these settings and how to guide me in the right direction rather than just randomly picking numbers. I don't want to have to always depend on stumbling upon settings that someone else used and copying those, but rather scientifically/musically understanding the adjustments and picking numbers based upon educated choices and not just luck (guessing)

Here's a link to a post that I'm referring to, but this applies to many other things for me as well:

http://forum.fractalaudio.com/amps-cabs/95094-matrix-nl212-tweaks.html

If you scroll down to mid-page, you will see the conversation with Robin of Matrix and his response to a user sharing his EQ settings. I look at frequency graphs of speakers and they look pretty similar overall. How does one know which frequencies should be dropped and which should stay?

Anyways, I know this post is going to make me seem like an idiot, but it's a valid question and I hope I can gain some more knowledge in understanding these speaker charts and how to set these things correctly. Thanks so much! :)
 
Hey Jeff,

You probably know more than you think. The topic is a little complex so I'll try to cover the very basics.
You're familiar with the Bass, Mid Range, Treble and Presence controls on a guitar amp, right?
Turn the Bass knob way up and you hear more Bass coming from the guitar cab.
Turn it way down and you hear a lot less. Big difference.
Turn the Presence knob way up and your guitar sounds a lot brighter.
Turn it way down and it sounds flatter, less bright, warm , dull, whatever word you want to use to describe it, it sounds very different than with the Presence way up.
The tone control knobs are there for you to color the sound.

Those speaker graphs you mention give you a visualization of the tone of a given speaker.
Some speakers have more Bass which makes them sound bass heavy, some have more Treble/Presence which makes them sound brighter/clearer.
You can see that in a graph very easily, once you understand what you are looking at.

The numbers you see at the bottom of a graph represent the Frequencies.
The scale on those graphs goes from the left, 20 Hertz (Super Low organ pedal bass sounds that you feel more than you hear) to the right, 20 kilohertz (Super high dog whistle sounds that none of us guitar players can hear anymore anyway)
Your guitars most important sounds, called the fundamental frequency range, is from 82 Hz (Your open low E String) to 1.2 kHz (Your High E string played at the 24th Fret)
Beyond making the fundamental frequencies, your guitar makes more sounds called "Harmonics".
Harmonics start at about 1.2 kHz and for all practical purposes go up to about 10 kHz. There are sounds above 10 kHz, some folks call it sheen or air.

EQing the Low or Bass Frequencies:
Sounds guys like myself will use a High Pass/Low Cut filter to roll off the lowest sounds your guitar makes, typically in the 85 Hz to 100 Hz range.
The reasoning behind this is to make a sonic space for the Bass guitar and Kick Drum to "sit in the mix".
Too much Bass from the guitars drowns out and muddies up the Bass guitar sounds and Kick Drum sounds. (Bad!)
Advice: If you play in a band, use a PEQ or Graphic EQ and remove everything below 85-100 Hz so your guitar let's the bass and kick sit better in the mix. Personally I use 100 Hz.
If you record, use a PEQ or Graphic EQ and remove everything below 85-100 Hz so your guitar let's the bass and kick sit better in the mix.
If you don't play in a band, don't worry about removing any low end.

EQing the High or Treble Frequencies:
Your Matrix Cab has speakers that can produce much higher frequencies than the typical Guitar Cab Speaker.
In the example below, the graph shows the Celestion V30 rolling off the high frequencies dramatically after 5kHz. (See the area labeled #2)
For example: A 7 kHz frequency is 30 db quieter than a 5 kHz frequency. That's a lot quieter!
That's pretty typical of guitar cab speakers. They start to roll off the high frequencies after 5-6 kHz.

The other thing you might notice is the "bump" which peaks at about 2.5 khz. (See the area labeled #1)
Based on the red base line of 100 db, the frequencies around 2.5 kHz are roughly 6-8 db louder than all the other frequencies in the range.
That means this speaker will be much brighter than if the graph were just a straight line.

So what does this have to do with your situation?
Your Matrix Cab is allowing you hear high frequencies you typically don't hear out of your guitar cabinet.
It may sound unnatural at first. Tinny, Fizzy, Brighter, Thinner... especially if you A/B them side by side.

"Ultimately, your Tone depends on what Guitar>Pickups>Amp>Gain Settings>Tone Settings and Cab/Speakers you are using"

Advice: Use a PEQ (Parametric Equalizer) or Graphic EQ, start at the highest frequency 20 kHz and start cutting highs.
Important Note: You have to this at the volume you're going to be gigging at, typically 90-100 db. Pretty LOUD! Bedroom volume won't translate well to gigging volume.
For the Graphic EQ, go to the slider all the way to the right and bring it all the way down: "THEN PLAY AND LISTEN"
Bring it back up to the middle: "THEN PLAY AND LISTEN"
Hear any difference?
Leave that slider all the way down, repeat above with the next slider until you start to hear what YOU consider to be a big difference.
You may get to 12 kHz and decide, "That's the tone I'm looking for!"...
Or, you may end up @ 6.5 KHz...
You will hear it when you get there, if you "PLAY, THEN LISTEN, THEN GO BACK AND COMPARE TO YOUR LAST SETTING"

Personally I use a pair of Matrix CFR-12's that I used Smaart analysis to PEQ pretty darn flat. See image below.
Since I'm using FRFR speakers, I always have a cab block in the signal path.
For some amps I use the cab block high pass and low pass settings to roll off lows @ 100 Hz and highs @ 7.5 kHz.
Others I set at 85 Hz and 12.5 kHz.
The right numbers depend on the: Guitar>Pickups>Amp>Gain Settings>Tone Settings and most importantly, my ears.

The low end is easy, just do it.
The highs must be seasoned to taste.
If you're not interested in starting at the highest highs, cut everything past 5 kHz, like the Celestion V30 and then bring one slider up at a time.
Having the X/Y feature built into the Ax makes it easy to compare EQ sounds.

Aside from cutting lows and highs, if you're still not 100% happy, you can shape the sound by gently cutting or boosting in the fundamental and harmonic frequency range. Most guys would use the amps tone controls to tweak this, but if they don't get you there, then try cutting a few db's in the 2 kHz-5 kHz range or boosting the 600-750 kHz 3-4 db.
Tip: In the end, extreme settings on your tone controls make the whole process more frustrating. Try setting Bass, Mid Range, Treble and Presence to "5" or mid point to dial in your cab tone.

Hopefully this gets you pointed in the right direction.

Celestion Vintage 30.jpg Greenback.jpg CFR-12 Smaart Analysis Comparison.jpg
 
Last edited:
^--- Agree, really well written and clearly explained, jimnov :encouragement:

One very trivial correction about harmonics; they actually overlap the fundamental range of guitar notes. For example, the lowest E (about 80 Hz) has harmonics at double the frequency (about 160 Hz), triple the frequency (about 240 Hz), etc.
 
That's a really nice explanation of frequencies and how to adjust them but it doesn't really address what (I think) he was asking about. He was referring to the Speaker tab in the amp block. You were talking about adding a PEQ to adjust frequencies which is great and good info to know since I am a PEQ noob as well! The Speaker tab looks like a sort of PEQ as well since it has Q settings and whatnot but Cliff has said it is not an EQ but some kind of simulated Impedance deal. From what I can gather, you are supposed to look up the specs on the speakers in your cab and then adjust the settings in this tab to match? But the only setting that really matches up with specs is the LF resonance frequency. The other settings such as HF resonance and the Q settings are still a mystery to me. Any ideas on how to set this other than just adjust them until it sounds like you want it?
 
Thanks for that link Winger, pretty much answers my questions! Also it looks like this tab isn't as important for me since I use SS power amp and guitar cab instead of direct or FRFR.
 
Jimnov.... WOW! I have to begin by saying thank you so very much for such a thorough and well-written reply. There is a lot of information in your response and I'm going to sit with it for awhile to "digest" it all while attempting to apply these principles you outlined. I know that this may raise a few more questions from me, so I hope you don't mind if I PM you with any specific questions I may have. You're obviously a wealth of information and I'd love to learn a bit more from you. Where in NY are you located? I'm on the island... maybe you're near?

One question that comes to mind is a comment that was made in that forum post by Robin from Matrix regarding setting the Hz to match your cab...

"set the cab low res setting to the same point that the real cab hits its low resonance, and this would correctly "load" the amp, just like the real speaker did, and get you a little closer to the exactly original sound".

"The cab is actually tuned to around 70 Hz, so if you have a genuine Fender head that you use with your NL212 and you are trying to get the exact same sound with your AxeFX, then 70 Hz would be a good place to start. If you only use an axe FX and are just trying to get "great tone" then the best place is most probably someplace else, and will only be found by experiment, there is nothing at all to suggest you have to use the same setting as the speaker is in real life, and indeed on FRFR systems, you would almost never use the same settign as the FRFR is tuned to, you would use the settign that most correctly emulates the thing you are trying to copy .. or whatever sounds "best" to your ear".

How does one know what Hz their cabinet is set at and what are the effects of tweaking those settings? I tried sweeping them high to low and hear maybe subtle changes in high/low tones (I think), but I'm not sure if what I'm hearing is the effect that it should be having. I guess I'm looking to hear a change and maybe imagining it?

Again, thanks SO much for such an amazing response!! This is exactly why being an AFX user wins out over any other product out there.... people like all of you on this forum!!
 
GM Arts said:
^--- Agree, really well written and clearly explained, jimnov :encouragement:

One very trivial correction about harmonics; they actually overlap the fundamental range of guitar notes. For example, the lowest E (about 80 Hz) has harmonics at double the frequency (about 120 Hz), triple the frequency (about 240 Hz), etc.
Click to expand...

Yep, you are absolutely correct!
I was trying to keep explaining the fundamental frequencies simple...
But in the real world, harmonics live there to.
Sometimes a picture better illustrates what actually happens as the harmonics are produced.
guitar harmonics.jpg
 
Hey Jeff,

Yes, you can PM anytime. I live in White Plaines, about 30 miles north of NY city.
Are you using a Cab block with the NL212 or just running an amp block?
Scott's article [link above] does a great job of explaining the complex interaction between an amplifier and a speaker.
What kind of amp are you using?
What kind of music do you play?

jimnov
 
Nagi Mysore said:
Awesome I may finally derive working PEQ knowledge from this
Click to expand...

If you have a DAW, record a guitar track, add a PEQ to the track, loop a section of it, pick any frequency, cut or boost it 12 db and then slowly sweep it left to right.
You'll hear some crazy tones, but you'll also might hear some places where the track pops.
Play a guitar track in a mix and do the same.
If you hear something you like, write down the frequency.

You can learn a lot by just playing around in the DAW. It doesn't mess with your preset, but it gives you a good idea of exactly how an EQ can shape your sound.
You might be surprised how nasty some guitar tracks sound all by themselves, but in the context of a mix, they fit perfectly.

It's one of the challenges we guitar players have...
We make it sound good solo, in our room, and then it disappears in the mix when playing live with the band.
 
FractalAudio said:
I wouldn't go by that information. It is outdated.
Click to expand...

Da Man!

Thank you for all you do! 18 is amazing!

How would you best describe the relationship between the speaker impedance settings in the amp block and the cab we are using, be it a FRFR or standard guitar cab?

Then how does the impedance curve [ low and high resonance settings] translate to the sound of my rig? More feel? Tighter Bass response?

How audible is it?
 
Just wanted to also chime in with thanks for jimnov, too. Great write-up!


Sent from my iPad using Tapatalk
 
Jeff B said:
Jimnov.... WOW! I have to begin by saying thank you so very much for such a thorough and well-written reply. There is a lot of information in your response and I'm going to sit with it for awhile to "digest" it all while attempting to apply these principles you outlined. I know that this may raise a few more questions from me, so I hope you don't mind if I PM you with any specific questions I may have. You're obviously a wealth of information and I'd love to learn a bit more from you. Where in NY are you located? I'm on the island... maybe you're near?

One question that comes to mind is a comment that was made in that forum post by Robin from Matrix regarding setting the Hz to match your cab...

"set the cab low res setting to the same point that the real cab hits its low resonance, and this would correctly "load" the amp, just like the real speaker did, and get you a little closer to the exactly original sound".

"The cab is actually tuned to around 70 Hz, so if you have a genuine Fender head that you use with your NL212 and you are trying to get the exact same sound with your AxeFX, then 70 Hz would be a good place to start. If you only use an axe FX and are just trying to get "great tone" then the best place is most probably someplace else, and will only be found by experiment, there is nothing at all to suggest you have to use the same setting as the speaker is in real life, and indeed on FRFR systems, you would almost never use the same settign as the FRFR is tuned to, you would use the settign that most correctly emulates the thing you are trying to copy .. or whatever sounds "best" to your ear".

How does one know what Hz their cabinet is set at and what are the effects of tweaking those settings? I tried sweeping them high to low and hear maybe subtle changes in high/low tones (I think), but I'm not sure if what I'm hearing is the effect that it should be having. I guess I'm looking to hear a change and maybe imagining it?

Again, thanks SO much for such an amazing response!! This is exactly why being an AFX user wins out over any other product out there.... people like all of you on this forum!!
Click to expand...

Doh..... Why didn't I check the "Tech Notes"....

Here's some info from Cliff himself that I never knew was there, because I didn't visit that section of the forum....

About Speaker LF Resonance
http://forum.fractalaudio.com/tech-notes/78003-about-speaker-lf-resonance.html#post949557

About HF Resonance
http://forum.fractalaudio.com/tech-notes/81121-about-hf-resonance.html#post985574
 
You must log in or register to reply here.
Back
Top Bottom