High frequency resonance when recording mic'ed high gain AMP

[Mochi]

Hello everyone,

I have a recording "problem" that is really bugging me and that I can't solve, and I'm sure that the pros here might be able to tell me what is wrong :-)

So I have a high frequency resonance when I record mic'ed up high gain amps. I like the recorded sound that I get but this resonance boggles because I can't un-hear it once i've noticed it. So for starters, here is a quick recording: https://soundcloud.com/mochimallone/prise

Can you hear what i'm talking about? A resonance, as if someone was next to the microphone with ringing bells just to piss me off lol .

So I have this noise:

- No matter the amp (I have 4 available) here the sound was recorded on a JCA50h
- No matter the guitar
- Tried bringing down the gain to crunch levels
- With ot without going through the pedalboard and no matter the cables used
- No matter the microphone used, though the ones I own are low end (here it is a Superlux PRA 628MKII) but it also does that with a sm57, a friend lent me one, I also tested with sm57 copies, always that same "tinny"resonance
- No matter the cab, I have 2, a splawn 4x12 in V30s and a homemade 1x12 with a celestion BN12-300s (here it is the BN12-300s)
- I moved the cabs around, put them in other rooms and also in a walking wardrobe, and even outdoors
- Whether I push the amp or not, I try to EQ it out directly from the amp side, doesn't work
- Whether I record in 96khz or 44.1 khz or anywhere in between - 24 bits and 16

I begining to think that it comes from the audio interface, a focusrite 6i6, I adjust the input level so that it does not exceed -6db (rather towards -11db), is the level too hot?

I can somewhat attenuate the resonance, by tweaking on the frequencies between 2.6khz and 4.2khz with a parametric EQ in the DAW (Reaper) but of course I also lose a lot of punch and dynamics.

I do not have the resonance when I go through a line out (after power amp) and I add IR cabs.

Any idea what my problem is? I can't hear this resonance while in the room, and it isn't picked up if I record with a camera mic/room mic

Thank you for reading :-)

[ajaxlepinski]

Post to check out after work.
This is interesting.

Are the floors, walls and ceilings, the same in each room that you recorded? Same height and materials?

With out listening to the clip, my guess is that you have standing waves. Put some foam or paddind above and below the mic. That will get rid of floor to ceiling standing waves.

[Mochi]

Nope different size rooms, some have carpets some do not, some wooden walls some not, i'll try the padding, good idea.

[ajaxlepinski]

Standing waves are usually floor to ceiling and floor height is usually consistent throughout a house or apartment. Probably, the only thing that remained constant during all your recordings.

[fretless]

I don't hear it yet . What are you monitoring with ?

[Ostinato Rubato]

have you recorded in the past? is this something new that you're hearing in recordings that wasn't there before?

I don't really hear what you're describing. I might be hearing some clipping, might. How high is the input gain on your scarlett? Try recording with much lower input gain and pushing up the volume on the master fader in the DAW. That might change what you're hearing, might.

[GuitarBilly]

You should use high/low pass filters. Set your EQ to low pass at around 15khz and high pass at 40hz. That should take the overtones out without changing your core tone. I'd use a graphic EQ instead of a parametric. That's standard process when recording heavy guitar tones to sit in a mix. If you are recording multiple tracks, send the tracks to an effect bus and process them all at once in the bus.

[Holy-diver]

the Scarlett has a hot input have you tried the pad function as well? I don't heAR what you are saying either though so idk

[ajaxlepinski]

I hear some not good distortion... are you recording super loud? Mic could be overloading or, as mentioned above, digital distortion (clipping) at the converter.

Waves Audio makes a fantastic, 30 band mono/stereo Graphic EQ plugin. 30 bands makes EQing very precise and easy.
Waves has an installer that you have to download first which is annoying but, their Graphic EQ and Vocal Rider are worth the effort.
Their Graphic EQ is on sale RIGHT NOW!!! http://www.waves.com/plugins/geq-graphi ... r-overview

[Holy-diver]

2nd the highpass/lowpass suggestion to remove unwanted highs and lows. That is what it sounds like to me after listening in the car and on the at m50

[Mochi]

ajaxlepinski You are spot on with the standing waves, what I did is put a guitar case in front of the speaker and cover over it like so : http://i.imgur.com/NvU7GWH.jpg .

Thanks so much it was driving me crazy. No the rooms in my house are actually all quite different, (dry wall, wood wall, suspended ceiling in one of them, more or less insulation and whatnot) but they are all quite big and somewhat empty.

I didn't notice it before either, until I started noticing it, and then I couldn't unhear it, my monitors are quite cheap that is true (fender ones), but I could hear it in everything, cheap IEM, cheap headphones, AKG 702, car stereo, laptop speakers, home cinema, it was always there

It was always there in my recordings just that I didn't notice it until recently (actually after I had a good drink lol). Now I'm by no means any good at recording, i'm learning with my meager home studio setup lol.

I was recording with a -11db with peaks to -6 (I did amplify the clip in the OP but it wasn't clipping according to the DAW). But after you mentioned it, I did do a bit of research on the web about levels, as I did start my very first recordings on tape, where I was taught to get close to the 0db clip. After some research -15 looks good for editing headroom, so thanks for putting me on that track.

Now i'll be looking at all the rest of the stuff to make the sound better, now that resonance has gone.

Thanks for all your input, much appreciated !!!

[ajaxlepinski]

I once owned an analog recording studio, that was located under a butcher shop and appropriately named, Meat Market Melodies.
It had a cement floor with a sheet rock ceiling. Even after installing thin, industrial carpeting, the standing wave between the floor and ceiling was annoying. If you clapped your hands, it created a very fast, high pitched echo that made a vvvringgggg sound. It was more noticeable on the drums than guitars or vocals. I put some Sonex tiles over the drums and that took care of the issue.

This is why pro studios are built with floors, ceilings and walls sightly out of parallel. Slightly angling the wall reduces the echo that causes standing waves. Acoustic tiles, furniture, carpet, diffusers, etc also help.

This is an effective but, extreme example of a diffuser:


And a more decorative one:


In concert halls, diffusers are used to disperse the sounds more evenly:

[Cirrus]

I can somewhat attenuate the resonance, by tweaking on the frequencies between 2.6khz and 4.2khz with a parametric EQ in the DAW (Reaper) but of course I also lose a lot of punch and dynamics.

That is a *very* common frequency range within which you might find ringing, annoying resonances when recording distorted guitar.

Basically, it's because of the physical size of 12" guitar speakers - you get common resonances that are just a function of the size of the frame, distance from the voice coil to the edge of the speaker etc.

Usually, you can remove them quite well with a very narrow EQ cut - basically as tight as your EQ can go, centered on the exact frequency of the ringing - sometimes you need to hit a couple of different frequencies.

But, as you've found, the more you take out the 'problem' frequencies, the more castrated the recording becomes. So it's a balancing act.

[ajaxlepinski]

I can somewhat attenuate the resonance, by tweaking on the frequencies between 2.6khz and 4.2khz with a parametric EQ in the DAW (Reaper) but of course I also lose a lot of punch and dynamics.

That is a *very* common frequency range within which you might find ringing, annoying resonances when recording distorted guitar.

Basically, it's because of the physical size of 12" guitar speakers - you get common resonances that are just a function of the size of the frame, distance from the voice coil to the edge of the speaker etc.

Usually, you can remove them quite well with a very narrow EQ cut - basically as tight as your EQ can go, centered on the exact frequency of the ringing - sometimes you need to hit a couple of different frequencies.

But, as you've found, the more you take out the 'problem' frequencies, the more castrated the recording becomes. So it's a balancing act.

That's really awesome to know!!!
In some situations (like recording high gain guitar) I would imagine that angling the mic may not even help.
I wonder if positioning the mic's diaphragm at 90 degrees, perpendicular to the speaker would do any good?

[Mochi]

I can somewhat attenuate the resonance, by tweaking on the frequencies between 2.6khz and 4.2khz with a parametric EQ in the DAW (Reaper) but of course I also lose a lot of punch and dynamics.

That is a *very* common frequency range within which you might find ringing, annoying resonances when recording distorted guitar.

Basically, it's because of the physical size of 12" guitar speakers - you get common resonances that are just a function of the size of the frame, distance from the voice coil to the edge of the speaker etc.

Usually, you can remove them quite well with a very narrow EQ cut - basically as tight as your EQ can go, centered on the exact frequency of the ringing - sometimes you need to hit a couple of different frequencies.

But, as you've found, the more you take out the 'problem' frequencies, the more castrated the recording becomes. So it's a balancing act.

Hun hun didn't know that, i'm thinking that those frequencies where bouncing off of something (the ceiling maybe) coming back to the mic and exacerbating it, yes what I was doing to find the frequencies, was using a very narrow parametric EQ at +12 and moving it around until I amplified the frequency, then tried to narrow down on the frequency as much as possible then attenuated it, it was taking quite a bit of time and I couldn't get rid of it completely.
And what i've always heard and being taught is you want to get a recorded sound as close as you want it EQ wise, because the more you EQ it the more you take away from the sound and dynamics.

I will be looking into diffusers, and the science behing the construction of them, because I have the tools, I know how to use the tools and acces to the material to make that, but I expect that the "paterns" used are not random.

[ajaxlepinski]

There are books on studio design and acoustics that provide formulas and math for designing diffusers and "tuning" rooms.
I sat in at a lecture, at the Audio Engineering Society, by a noted engineer who described all the ins-and-outs of diffusers and eliminating standing waves, echos and unwanted reflections. You can calculate what frequencies will be attenuated and which will be boosted based on room size, building materials, wall angels. There are even formulas for laying out wood blocks on a diffuser.
It all boils down to:
1) avoid parallel walls and ceilings - the more irregular, the better.
2) the softer and deeper the wall, floor & ceiling coverings, the fewer unwanted reflections.
3) In a small to average room for recording, deader is better.