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Speaker Resonating Frequency

shadoe

Experienced
I've owned my Axe FX II for nearly 3 years. I had a standard before that. I've been attempting to make a nice, smooth metal tone for just as long. I could always nail the mids-highs and gain that I wanted. However, I could never figure out low-end. When I eq'd the low end to my tastes, it just muddied everything up.
This morning when I woke up, I thought about editing a tab in the amp block that I had never touched before. Thus, I dove into the speaker tab.
THIS CHANGES EVERYTHING
I read up on the wiki, and proceeded to find the Speaker Resonating Frequency. DEAR Jesus. My low end sounds nice and crisp. I love it. It was only a minor change. But, it made a world of difference.
I assume it would do the same for low-gain tones or what have you. However, I HIGHLY encourage all you high-gain guys to check it out.
If you haven't read up on SRF, here's an excerpt from the wiki.
  • "The speaker tab is not an EQ. It allows you to adjust the impedance that the virtual speaker presents to the virtual power tubes. In most cases the resulting EQ is quite different than the impedance curve since negative feedback flattens the response. If you turn the damping all the way down then the EQ will be close to the impedance curve (but still influenced by the transformer)." source
  • "There are certain aspects that simply can't be modeled and require user intervention. For example, a speaker has a low-frequency resonance. A tube amp will create a higher output at that resonant frequency. The Axe-Fx has no way of knowing what that resonant frequency is and defaults to a value that is common for the speakers that are typically used with that amp. However, if you drive that speaker through a solid-state amp you won't excite the resonance unless you adjust the Speaker Resonant Frequency to match it."
  • "One way to find the SRF is to put a Filter block after the amp block. Set the type to Peaking, Q to 5 or so and Gain to 10 dB. Start with a Freq. of 50 Hz. Play some chugga-chugga and slowly adjust the Freq. until you hear and feel the cabinet resonate. Make a note of the frequency. Remove the filter block and set the amp block SRF to match. 4x12s typically have an SRF of between 80 and 120. Open back cabs are typically a bit lower."

    http://wiki.fractalaudio.com/axefx2/index.php?title=AMP_block_parameters
 

Pwrmac7600

Power User
  • "One way to find the SRF is to put a Filter block after the amp block. Set the type to Peaking, Q to 5 or so and Gain to 10 dB. Start with a Freq. of 50 Hz. Play some chugga-chugga and slowly adjust the Freq. until you hear and feel the cabinet resonate. Make a note of the frequency. Remove the filter block and set the amp block SRF to match. 4x12s typically have an SRF of between 80 and 120. Open back cabs are typically a bit lower."
  • http://wiki.fractalaudio.com/axefx2/index.php?title=AMP_block_parameters
So excuse my ignorance, but does this method of finding the resonant frequency only apply when using an amp and cab, ir when running direct also? I ask because it states to roll the freq until you hear the cab resonate. Would i hear a virtual cab resonate?
 

Deadpool_25

Power User
Heh. Yeah researched this and did it a week or so ago for my real cab. It made a huge difference.

Cliff put up an in depth article on it.
http://forum.fractalaudio.com/threads/about-speaker-lf-resonance.78003/

I wonder how many people go in and change it when changing IRs. I'd think it wouldn't need to change much/at all if you were switching between cabs with the same speaker, but if you switch from like a V30 cab to a G12M cab or something and the bass response seems a little "off", it would make sense to tweak it a little.
 

Tahoebrian5

Fractal Fanatic
So excuse my ignorance, but does this method of finding the resonant frequency only apply when using an amp and cab, ir when running direct also? I ask because it states to roll the freq until you hear the cab resonate. Would i hear a virtual cab resonate?
Yes, it does not apply if you are using frfr
 

shadoe

Experienced
So excuse my ignorance, but does this method of finding the resonant frequency only apply when using an amp and cab, ir when running direct also? I ask because it states to roll the freq until you hear the cab resonate. Would i hear a virtual cab resonate?
It works with irs too. Although, it's definitely more subtle. It improved my ir low end and cleaned up some mud.
 

Hubi

Experienced
It works with irs too. Although, it's definitely more subtle. It improved my ir low end and cleaned up some mud.
Same here - absolut important if you use IR´s.
Makes a lot of difference and you should change whenever you change the amp with the same cab.

I like CabIR IR´s - there´s the right resonance frequence in every info of the cab.

But it works also with the info you get from the internet (Jensen for example, if you use Own Hammer DLX 112).

The piece of paper with the frequences is above my Axe.........will post, what I have found.

It saves a lot of meters on the tweaking road...........
 

mtmartin71

Experienced
I'll say it again, wouldn't it be great if there was a drop down in the speaker tab so you could select from a list of common speakers and have the matching values populated for you! Please?... :)

Yes! Two fold really. It would be nice if the IR makers who are mostly selling to the AxeFX crowd would supply the speaker tab measures when they sell the cab/speaker packs. I think the The Amp Factory is the only one who has taken the time to do this but not sure what those settings are and how they end up impacting the tone. The other thing is as you said...give us a short cut to select some reference settings by cab/speaker type. So 4x12 angled, 4x12 straight, oversized 4x12, 2x12 open back, 2x12 oversized, etc.

Having said all of that, I wonder if...due to the wide and varying settings for what seem to be similar cabs... Cliff and team just set what they think is sounded best for that model. 4x12s range between 100 to 115 and 2x12s are all over the place. I don't know if they actually measured or just estimated. Anyhow, in the spirit of striving for accuracy, this is one area that would be cool to get a WIKI of measures going or get it built into the product itself.
 

Hubi

Experienced
Yes! Two fold really. It would be nice if the IR makers who are mostly selling to the AxeFX crowd would supply the speaker tab measures when they sell the cab/speaker packs. I think the The Amp Factory is the only one who has taken the time to do this but not sure what those settings are and how they end up impacting the tone.

Have a look above - or on the CabIR website.
 

dr bonkers

Fractal Fanatic
Vendor
If you load the ir in Cab Lab, you will see the plot of frequency response in the graph.

You can adjust the Amp Block speaker tab settings to replicate that graph.

It's a better way to go if you are mixing various different cab ir's and mics together into one mix ir.
 

ML SOUND LAB

Cab Pack Wizard
Vendor
The low resonance frequency is one of the most powerful tools I fine tune for achieving the best metal tones. Even the smallest tweaks like 114hz to 115hz changes your palm mutes completely and the amount as well. Good for pointing this out @shadoe .
 

barhrecords

Axe-Master
If you load the ir in Cab Lab, you will see the plot of frequency response in the graph.

You can adjust the Amp Block speaker tab settings to replicate that graph.

It's a better way to go if you are mixing various different cab ir's and mics together into one mix ir.

The impedance graph from the spkr page and frequency plot from the IR are not the same right?

The spkr page settings determine how "hard" the amplifier is working at any particular frequency. This is not the same as the frequency response of the speaker.
 

Wolfenstein98k

Power User
Personally I tune the low resonance frequency to a note in the key I'm playing. When I'm just jamming Metallica or whatever - aka playing almost exclusively in E minor - I tune it to E (82.41Hz) or B (123.47Hz), whichever's closer to the default, and call it a day.
 

dr bonkers

Fractal Fanatic
Vendor
The impedance graph from the spkr page and frequency plot from the IR are not the same right?

The spkr page settings determine how "hard" the amplifier is working at any particular frequency. This is not the same as the frequency response of the speaker.

Interesting. I did not think of that. In some cases, the Manufacturer does not release those impedance graphs.

For example, Hartke keeps that data really close to the vest, when I tried to research it when using the Redwires ir's.
 

barhrecords

Axe-Master
Interesting. I did not think of that. In some cases, the Manufacturer does not release those impedance graphs.

For example, Hartke keeps that data really close to the vest, when I tried to research it when using the Redwires ir's.

And when they do release the information, it's almost always measured in the free field and the Y scale is often omitted. (The X scale it typically octaves on ISO centers but not always.)

IIRC FAS said you need to measure at the speaker terminals with the speaker in the cabinet and the amplifier in the circuit.
 

mtmartin71

Experienced
If you load the ir in Cab Lab, you will see the plot of frequency response in the graph.

You can adjust the Amp Block speaker tab settings to replicate that graph.

It's a better way to go if you are mixing various different cab ir's and mics together into one mix ir.

The issue I find with this is trying to eyeball and interpret that graph. For 4x12s, I've arrived at 115Hz for an Angled Marshall-type cab, 110Hz for a straight 4x12, and 105Hz for bassier cabs where I need to take some off.

To the point of ML Sound Lab, this frequency is key for me. I guess I'm one of those anyl bastards though and want to do what's accurate. It's hard for me to get around that...rather than just dial in what sounds best by ear. I'll probably just stick with my current approach.
 

Rex

Legend!
The impedance graph from the spkr page and frequency plot from the IR are not the same right?

The spkr page settings determine how "hard" the amplifier is working at any particular frequency. This is not the same as the frequency response of the speaker.
Right. A speaker's impedance curve and its frequency response aren't the same thing. You can't use the graph in Cab-Lab to find a cab's resonant frequency.
 

dr bonkers

Fractal Fanatic
Vendor
Right. A speaker's impedance curve and its frequency response aren't the same thing. You can't use the graph in Cab-Lab to find a cab's resonant frequency.

Thanks. I have learned something new.

It's too bad that there is no automated way of finding this curve using the ir file.

If people are able to find this resonant frequency using a filter block and playing chugga-chugga as suggested above, I would think there must be a way to automate this discovery process, since finding those graphs for some manufacturers is like chasing snipes in some instances. And playing chugga-chugga introduces all sorts of instrument/pickup, player perception, and monitoring environment variables into the discovery process.
 
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