The Truth Hurts - REW and my room...

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Re: The Truth Hurts - REW and my room...

Post by The Scum » Thu Apr 08, 2021 10:49 am

An easy test to see what might be ringing:

Clap your hands loudly (or, since you're into percussion, maybe you have a slapstick), and listen to what responds. Then remove or dampen what you can.

I discovered that the sections of the HVAC diffuser ring like a bell - I need some dynamat or something to dampen it.
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Re: The Truth Hurts - REW and my room...

Post by digitaldrummer » Thu Apr 08, 2021 12:07 pm

I'm not really hearing any ringing. it's more what shows in the measurements, which makes me think it is more in my setup. Specifically I think the monitors on top of the sidecar racks are suspicious. I wonder if anything like a Mopad would help? I originally did not have the bricks on top, but adding those seemed to tighten up the low-end, which is another reason I think I may be in the ballpark... And of course there are plenty of knock-offs of Mopad-like supports, as well as different designs for even more $$. the prices are all over. ATS Acoustics has some Mopad-like iso-pads for $6 pair.

anyone using iso-pads and what is your experience?
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Re: The Truth Hurts - REW and my room...

Post by digitaldrummer » Tue Apr 20, 2021 8:12 am

so I bought a set of these. https://www.amazon.com/gp/product/B08GL ... UTF8&psc=1

they are knock-offs and maybe a real set of mopads or similar name-brand would work better, however, for these I think it actually slightly lengthens the low frequencies ringing just slightly. I'd like to try some real mopads but didn't want to spend the $$ if they didn't do anything.

here's the "before" look:

1/24 smoothing SPL...
SPL-full-24.jpg
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left-nofoam.jpg
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I don't think these look too bad really. I also pulled the desk out away from the wall a little more, so the monitors are probably closer to 3' from the wall again now
Last edited by digitaldrummer on Tue Apr 20, 2021 8:15 am, edited 1 time in total.
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Re: The Truth Hurts - REW and my room...

Post by digitaldrummer » Tue Apr 20, 2021 8:14 am

here's the "after" or with the foam pads:
and the low end only SPL (1/24 smoothing)...
SPL-low-24.jpg
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left-withfoam.jpg
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right-withfoam.jpg
right-withfoam.jpg (169.1 KiB) Viewed 4392 times
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Re: The Truth Hurts - REW and my room...

Post by losthighway » Sat Mar 26, 2022 1:47 pm

This would seem the right place to put this, as opposed to a new thread since I'm following a similar experience.

Here's my bad news:

Image

Or if photobucket wants to be dumb (or I am) you can view here:
https://drive.google.com/file/d/1VekeEX ... sp=sharing

I played around a lot with speaker position and the various settings on the back of my Focal Shape 65s. It just spit out subtle variations of what we see here. The problem is large, physical and very centered as a null around 80hz and a slightly less brutal one at its multiple, 400hz. I measured with a Shure ksm141 in omni. I left my office chair in front of the desk where it would normally be and placed the mic at the same altitude and position my head sits when working. I will be zero degrees offended if anyone would like to critique my methodology, this is my first REW rodeo.

I'm going to need some trapping, no one is surprised.

Here's the basic info.

The room is narrow, maybe 12' x 22'. The ceiling slopes up from where the desk sits at around 9' high sloping up to14' at the back, if I remember. 3 out of 4 walls have 2 inch 703 from about 3 feet up to the ceiling covered in fabric with some wood slats. The corners behind the speakers started with four inches of 703, but then I added floor to almost ceiling 4 inch thick 703 panels in front of those when I was wildly shooting from the hip and not measuring things like a reasonable person. The back wall is shelves with books and snares, a smooth door, a lot of random wood tacked to the walls. There is another guess made 'trap' at the corner of the back ceiling made of pegboard with 2" 703 glued to it, and 4" fluffy pink stuff on that that goes diagonally from the higher part of the wall to where it meets the ceiling.

I can't symmetrically put traps floor to ceiling in the back corners because the door to the live room is in one of those corners. I could reconfigure the stuff I did on the front corners to include more fluffy pink stuff. If I remember, the way it is framed now I could easily get another 8 inches to a foot in there with a little demolition and re-beautifying. I could also build some kind of corner ceiling soffits to run some length of the ceiling.

I'm a little scared to get super precise with a DIY job on some Helmholtz resonant absorbers, but am willing to try anything.

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Re: The Truth Hurts - REW and my room...

Post by vvv » Sat Mar 26, 2022 6:11 pm

Right now, how's it sound?
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Re: The Truth Hurts - REW and my room...

Post by losthighway » Sat Mar 26, 2022 7:21 pm

vvv wrote:
Sat Mar 26, 2022 6:11 pm
Right now, how's it sound?
Ya know, it sounds okay. But I think a major hurdle in my work probably could have been cleared a couple years ago as I started trying to finish up my space if I would have just taken the plunge into this stuff.

I find that I want to peek at my mix on other systems and I'm always confused by what I hear. Part of it is the weirdness of other systems, but sometimes they're revealing what I missed on my fancy speakers in my control room. And it's largely low end.

This has been confirmed by a couple different mastering engineers who I asked for feedback to see what they have to correct. In more than one instance said that the mixes were good and it was all typical mastering moves, except that there was some boomy low end business either on a bass guitar or the kick that took some magic to tame. Every time I'm mixing and I want to feel a little more oomph on the kick and start to bring up a little notch I get anxious that I'm setting up a boomy situation without knowing it. Makes sense now that I can see the massive hole at 80hz in my listening environment.

But does it sound good? I think I just really want it to sound accurate enough that the idea of checking it on the office speakers sounds totally unnecessary.

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Re: The Truth Hurts - REW and my room...

Post by Dok » Sat Mar 26, 2022 8:13 pm

losthighway wrote:
Sat Mar 26, 2022 1:47 pm
The problem is large, physical and very centered as a null around 80hz
The only way you'll fix that is with a sub, probably two of them.

https://mehlau.net/audio/multisub_geddes/

https://carltatzdesign.com/downloads/el ... rticle.pdf

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Re: The Truth Hurts - REW and my room...

Post by losthighway » Sat Mar 26, 2022 8:59 pm

Dok wrote:
Sat Mar 26, 2022 8:13 pm
losthighway wrote:
Sat Mar 26, 2022 1:47 pm
The problem is large, physical and very centered as a null around 80hz
The only way you'll fix that is with a sub, probably two of them.

https://mehlau.net/audio/multisub_geddes/

https://carltatzdesign.com/downloads/el ... rticle.pdf
I'm a little skeptical. Especially considering the second article seems confident that 125hz is the missing frequency with near fields in a typical smallish control room, and that's my biggest peak. Or the idea that the room mode exists no matter how much volume that frequency is putting out there it's arriving with a negative phase relationship so putting out more of the lacking frequency will put out equal amounts of it in those same destructive phase terms.

But I never thought about how multiple subs could change the movement of those frequencies in the space over time. The graphs on the first link are pretty compelling.

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Re: The Truth Hurts - REW and my room...

Post by MoreSpaceEcho » Sun Mar 27, 2022 6:53 am

You need more treatment, not a sub. A sub is only going to make it worse right now.

Your problem is almost for sure SBIR from the front wall. Maybe the side walls as well.
losthighway wrote:
Sat Mar 26, 2022 1:47 pm
I could reconfigure the stuff I did on the front corners to include more fluffy pink stuff. If I remember, the way it is framed now I could easily get another 8 inches to a foot in there with a little demolition and re-beautifying. I could also build some kind of corner ceiling soffits to run some length of the ceiling.
Do that for starters.

How far are the speakers from the front wall?

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Re: The Truth Hurts - REW and my room...

Post by losthighway » Sun Mar 27, 2022 7:20 am

MoreSpaceEcho wrote:
Sun Mar 27, 2022 6:53 am
Do that for starters.

How far are the speakers from the front wall?
They're only a couple feet away, but close to my panels, so they can't move closer to the wall, but I shot the room with them another foot or two out and the null was identical.

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Re: The Truth Hurts - REW and my room...

Post by Dok » Wed Mar 30, 2022 5:25 pm

losthighway wrote:
Sat Mar 26, 2022 8:59 pm
Dok wrote:
Sat Mar 26, 2022 8:13 pm
losthighway wrote:
Sat Mar 26, 2022 1:47 pm
The problem is large, physical and very centered as a null around 80hz
The only way you'll fix that is with a sub, probably two of them.

https://mehlau.net/audio/multisub_geddes/

https://carltatzdesign.com/downloads/el ... rticle.pdf
I'm a little skeptical. Especially considering the second article seems confident that 125hz is the missing frequency
That's not quite what it's saying:

What this means is that you are making
your mix decisions in a low-frequency
‘Grand Canyon’ which runs from
approximately 125Hz or higher down to
maybe 60Hz. With the setup described
above, which is very typical, there have
been no exceptions to this phenomenon.


Your grand canyon starts attenuating at 120Hz and goes all the way down to 60 - that's almost exactly what's described in the article. The reason it varies from room to room is a property of each room's unique dimensions. Anyway, no amount of treatment is gonna get rid of that null - and keep in mind that it's a lot easier to buy a subwoofer, test, and return it if it doesn't work out than it is to do the same with acoustic treatment. Good rooms have both but you'll never get rid of that big-ass null without proper speaker placement and sub(s). Check out where digitaldrummer's big nulls are too in the posted graphs - notice anything similar?

I have an earlier post where I described finding the right positions for my subwoofers in my current room here, maybe you'll find it helpful: viewtopic.php?f=14&t=90064&p=719342#p719342

Also it seems counterintuitive, but you're not really putting out more of the specific lacking frequencies than any other with a sub other than whatever is below the crossover (that's what your corrective EQ a la SonarWorks is for after you've dialed in your positioning), and you're not trying to put anything "out" into the room. You're trying to activate the room itself at those missing frequencies - make the box you're in vibrate sympathetically instead of antagonistically, which is often why good results are found when the subwoofer is firing at the wall it's next to.

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Re: The Truth Hurts - REW and my room...

Post by losthighway » Wed Mar 30, 2022 7:04 pm

^ You caught me- I skimmed the article. Thanks for taking the time to clarify.

I think adding a sub might be my final step. Especially one that can be tuned into a narrow frequency range. For now I tried some ideas Morespaceecho was kind enough to share with me. I moved the speakers as close to the wall as possible, which as he predicted moved the hole in the spectrum to a higher (and more easily managed) frequency. With some added corner trap action I went from a 15 db hole at 80 hz to a 5-10 db hole around 95. My 400hz hole totally disappeared (which how the hell was I mixing with such a dent in the mud/bark end of the spectrum?), I got a little more support in the sub 50hz area. Maybe a little high around 60hz, but it's a clear improvement.

I'd love to see if I can get a little more of that 95hz in with some more trapping, but I don't think I will get it all the way up with anything reasonable I'm willing to do to the room. Just some lighter shades of better.

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Re: The Truth Hurts - REW and my room...

Post by Dok » Wed Mar 30, 2022 7:13 pm

losthighway wrote:
Wed Mar 30, 2022 7:04 pm
I moved the speakers as close to the wall as possible, which as he predicted moved the hole in the spectrum to a higher (and more easily managed) frequency.
Cool. This works on the same principle as a properly-positioned sub. That close to the wall, your monitors are doing some of the work exciting the room modes.

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Re: The Truth Hurts - REW and my room...

Post by MoreSpaceEcho » Thu Mar 31, 2022 7:11 am

Dok wrote:
Wed Mar 30, 2022 5:25 pm
Anyway, no amount of treatment is gonna get rid of that null
???

That's exactly what proper room treatment does.

I don't feel like arguing so I'll just say that going from a 15db null at 80 to half that at 95 is a HUGE improvement and losthighway I hope you did a little celebration dance.

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