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Post by Johnkenn on May 21, 2015 20:48:04 GMT -6
I just recorded some acoustics and noticed I was getting a bell like feedbackish ton that I had to notch out at about 1100 hz. What the hell is that? And how do I correct it? Obviously that has something to do with the acoustics of the room...I've experienced it before, but today it seemed more prominent.
I am using EQ to pull the offending frequency up at about 9 seconds, then again at 21ish seconds...
https%3A//soundcloud.com/johnandkris/1khz-room-mode
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Post by sopwith on May 21, 2015 20:58:06 GMT -6
You using one mic or two? I got a bit of this last weekend with a 57 on the grill of a cabinet and the CV4 set a few feet back, I think it was some comb filtering from the (small) room. I did flip the phase on one mic, but it was still there a bit whenever the levels of the mics were uneven. When I pulled them both up to -6, it mostly disappeared.
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Post by Johnkenn on May 21, 2015 20:59:47 GMT -6
Just one mic. Almost like its feeding back/resonating at that frequency.
I googled comb filtering and listened - that's not what I'm getting...and I guess it can't be comb filtering because it was one mic and one signal.
Maybe it's a node? I have no freaking clue what I'm talking about, but I with I could get rid of it.
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Post by sopwith on May 21, 2015 21:15:53 GMT -6
Yea that's kinda what I had with my setup. Pretty sure it's the room. I'm nooby mcnoobert around here so let's go with a node :shrug: I'm sure one of these guys can sort you out when they hop on.
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Post by Johnkenn on May 21, 2015 21:20:02 GMT -6
Well apparently it is Room Modes...
"The input of acoustic energy to the room at the modal frequencies and multiples thereof causes standing waves. The nodes and antinodes of these standing waves result in the loudness of the particular resonant frequency being different at different locations of the room. These standing waves can be considered a temporary storage of acoustic energy as they take a finite time to build up and a finite time to dissipate once the sound energy source has been removed."
Might need to move some absorption around. And I should probably play towards the long side of the room so I'm not reflecting from the 12 ft width of the room.
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Post by gouge on May 21, 2015 21:33:30 GMT -6
at 1.1khz you are most likely looking more at flutter echoes. diffusion takes care of that for lower volume instruments.
it could also be comb filtering between the mic and the acoustic. 1.1khz has a wavelength of about 12"
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Post by Randge on May 21, 2015 22:26:50 GMT -6
That is a Martin, John. It's what they do. Those are indigenous to the instrument. They are harmonic content within the instrument and not from any recording process misstep. Normally, if you play a G chord, it is a major 7 note ringing out in a Martin coming from the D string. You can take it to whatever room you want to, and now that you hear it, it will be the same regardless of where you are. Usually, I only find it offensive at the end of songs, so, I tend to find the offending tone and automate it out with a tight Q in a good ITB eq.
R
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Post by Johnkenn on May 21, 2015 22:31:35 GMT -6
Thanks guys...I can take it out with notch eq...but it's just weird...
I added an example at the top. You can really hear it at the beginning of the snippet.
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Post by sopwith on May 22, 2015 3:29:52 GMT -6
Oh yea that's kind of wild. Does just sound like a normal Martin dread though. Randy are those overtones dictated by the bracing, body shape, or by the wood? Always felt like my d35 is overtone rich but very balanced.
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Post by keymod on May 22, 2015 4:09:15 GMT -6
This may be sacrilege, but can you stuff some of the filling that they use inside speaker cabinets into the body of the guitar in order to dampen the offending freqs?
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Post by Ward on May 22, 2015 6:39:45 GMT -6
Thanks guys...I can take it out with notch eq...but it's just weird... I added an example at the top. You can really hear it at the beginning of the snippet. , do you have any basic carpentry skills? You could make up a couple of inexpensive diffusors in the garage, if you have the tools. A few of us could share plans here for you and others to pick from... As a resource to the RGO 'community'. Just a thought! |
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Post by Randge on May 22, 2015 6:57:33 GMT -6
After hearing that example, what I am talking about is something entirely different. I am talking about when you strum a chord and hold it and it rings different notes than the intended chord.
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Post by svart on May 22, 2015 7:04:58 GMT -6
Yeah I don't think it's room issues. That sounds either like a resonant node from the guitar and the strings, or something from the mic/pre.
Try changing the strings to a different gauge or different brand and see if it goes away or changes frequency. If it does, then it's the guitar/strings combo.
If it doesn't, then start by moving your recording to a larger space, maybe even outside, and see if it goes away. If not, then it's not the room and must be the mic/pre.
Or you could just change the mic or pre first and see..
Anyway, I had a hard time hearing it. It's much more apparent at 0:21 than 0:9. In a mix I'd be nobody would hear it.
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Post by kcatthedog on May 22, 2015 7:30:26 GMT -6
room modes will effect specific freq and aren't really source dependent, i.e.e any source with that freq in its sound will excite the room node. as you seem to have just noticed this with the current guitar, strings, mike and location, I think svart is on to something, in terms of checking all that that? maybe you were on to something building those diffusers a while back  comb filtering I don't believe is a specific freq, sounds more like a phased/flange sound sweeping across a range of freq but it is related to the room nodes etc as the sound you hear is not a true representation of the source as freqs are being affected across the range ( hence the comb image with various points) ? |
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Post by indiehouse on May 22, 2015 7:48:49 GMT -6
Yeah I don't think it's room issues. That sounds either like a resonant node from the guitar and the strings, or something from the mic/pre. Could you explain a little how the mic pre could cause this? I'm actually dealing with a similar issue. I recently tracked a mono acoustic with a nasty freq around 1khz using a DIY EZ1290 (1073 clone). The last session (same player/guitar) didn't have this issue when I used my VP28. |
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Post by indiehouse on May 22, 2015 7:56:27 GMT -6
Transformer ringing or something? Or perhaps self-doubt and paranoia that I screwed up my build.
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Post by svart on May 22, 2015 8:03:12 GMT -6
Yeah I don't think it's room issues. That sounds either like a resonant node from the guitar and the strings, or something from the mic/pre. Could you explain a little how the mic pre could cause this? I'm actually dealing with a similar issue. I recently tracked a mono acoustic with a nasty freq around 1khz using a DIY EZ1290 (1073 clone). The last session (same player/guitar) didn't have this issue when I used my VP28. I'm guessing it could be a variety of reasons. I had an issue with my Neve preamps before having a strange response with certain loads on the input and output. My first guess is that it's the transformers resonating/ringing. Most people look at overshoot and frequency response only, but a transformer is basically an inductor and can form an LC tank oscillator in certain circumstances. Neve circuits operate with some local feedback in the circuit, which could lead to some ringing at lower frequencies when excited with a specific tone, or sets of tones. I suppose you could run a sine sweep through the preamp and record the output to see if the amplitude peaks around 1khz. Since the older neve modules were rated at 600R, giving them a load of 10K-47K(Line level input range) is probably too light of a load. Try putting a small 600R pad(-3dB or so) on the output and see what happens to the response when you do a sine sweep. I bet it flattens out considerably. Or try the -3dB/600R pad with your acoustic and see if the nasal tone goes away. Of course, this is all guessing. |
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Post by tonycamphd on May 22, 2015 8:17:45 GMT -6
John, now that u hear that resonance in the recording, do u hear it when u just play the guitar? If yes, do u hear it when u play the guitar in another room?
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Post by Johnkenn on May 22, 2015 8:28:40 GMT -6
I have had this happen on different brands, so yeah, Randge...like you said, don't think what I'm talking about is the same...Not sure it's the pres - Seems to happen on all of them. I really think it's just something to do with the room. svart, you've seen how small my room is...and then I'm cutting it down even more with those half ass baffles I made. Maybe I should take those down and make sure I play long-ways instead of sideways. Also, maybe getting the mic closer could possibly help...If it's the room, you would think that would help. |
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Post by Johnkenn on May 22, 2015 8:32:34 GMT -6
John, now that u hear that resonance in the recording, do u hear it when u just play the guitar? If yes, do u hear it when u play the guitar in another room? I'll check...but like I said, I've heard this in acoustic guitars for years. This particular recording just seems a little more pronounced. Actually, the recording that I posted is just me doodling, and I used the 84 and the 47 in stereo...The original recording I was having problems with was mono - just the 84. Usually, I could just yank a little down around 1khz...but I had to notch this freq out on that recording...It wasn't me, so maybe the player was moving and maybe the mic got a lot closer to the soundhole...not sure. |
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Post by Johnkenn on May 22, 2015 8:32:54 GMT -6
And btw - now I think I hear that sound in my sleep...
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Post by svart on May 22, 2015 8:44:51 GMT -6
And btw - now I think I hear that sound in my sleep... And you'll hear it everywhere too. I put my KM184 mics right up on acoustics and I don't think I hear anything quite like that. I'd try going out to that balcony outside your room and seeing if it happens out there, since it's much more open. You'll get more room sound, but you won't have fast reflections from close walls. IIRC, your small room was VERY dead sounding already. It could be just a "peak" in the response of the room due to the angles and narrow walls, but I swear I didn't hear much room tone in your recording, if at all. |
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Post by Johnkenn on May 22, 2015 8:46:29 GMT -6
Yeah I don't think it's room issues. That sounds either like a resonant node from the guitar and the strings, or something from the mic/pre. Try changing the strings to a different gauge or different brand and see if it goes away or changes frequency. If it does, then it's the guitar/strings combo. If it doesn't, then start by moving your recording to a larger space, maybe even outside, and see if it goes away. If not, then it's not the room and must be the mic/pre. Or you could just change the mic or pre first and see.. Anyway, I had a hard time hearing it. It's much more apparent at 0:21 than 0:9. In a mix I'd be nobody would hear it. Oh - just to be clear - that is me pulling up the frequency at 09 and 21... |
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Post by Johnkenn on May 22, 2015 8:48:34 GMT -6
Yeah - I guess it's not THAT much of a big deal considering I can notch it out...but damnit...I want a perfect take...And the weird thing is, I swear I've had some acoustic tracks that sounded almost perfect. It could all be psychosomatic.
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Post by svart on May 22, 2015 8:52:52 GMT -6
Yeah I don't think it's room issues. That sounds either like a resonant node from the guitar and the strings, or something from the mic/pre. Try changing the strings to a different gauge or different brand and see if it goes away or changes frequency. If it does, then it's the guitar/strings combo. If it doesn't, then start by moving your recording to a larger space, maybe even outside, and see if it goes away. If not, then it's not the room and must be the mic/pre. Or you could just change the mic or pre first and see.. Anyway, I had a hard time hearing it. It's much more apparent at 0:21 than 0:9. In a mix I'd be nobody would hear it. Oh - just to be clear - that is me pulling up the frequency at 09 and 21... Honestly I wouldn't have heard it if you didn't boost it. I've come to expect that each instrument will have something like this, so I focus on overall tone fitting the mix and the performance. |
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