The Truth Hurts - REW and my room...

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digitaldrummer
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The Truth Hurts - REW and my room...

Post by digitaldrummer » Fri Apr 02, 2021 4:59 pm

I tried to follow the REW directions and a few other tutorial videos, etc. so I hope I did it right. I used my Radio Shack SPL meter to set a 75dB (C weight, slow) but the result here seems like it is averaging 85-90. not sure if that is normal? Thought I would share some results in case anyone else has suggestions. Honestly I don't think it looks that bad, and it did improve slightly after I added 6" of rockwool behind the desk, and then slid the desk as close to the wall as I could (but could only get so close due to that 6" of Rockwool and not wanting to put my powered speaker's heatsinks right up on the fabric...). But there is the 5dB dip between 60 and ~140Hz. (I don't expect to hear too much below 40Hz without a sub)

I have 2 pair of monitors (Dynaudio BM6amkii and Fluid Audio FX80) so I got measurements with each (individually), but they all track pretty closely. My room is 19 x25, and I am in the center of the 25" wall. I have 10' ceilings but it is vaulted so it geos to 15' at the top center. So there is an angle right above my mix position. I do have 2' x 4' x 4" of OC703 right on that angle, and then there are OC703 clouds at the peak of the ceiling. I also have superchunks in each corner - about 9 or 10ft high. So I feel like I am sufficiently trapped...

this is the full SPL graph (with 1/12 smoothing)
4-2-2021_full.jpg
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This is zooming in on the low end - 15hz - 400Hz (also 1/12 smoothing)
4-2-2021_15-400.jpg
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Last edited by digitaldrummer on Fri Apr 02, 2021 5:06 pm, edited 1 time in total.
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Re: The Truth Hurts - REW and my room...

Post by Scodiddly » Fri Apr 02, 2021 5:05 pm

Seen worse. Now you know what you're up against.

In the live sound world I use SMAART, and the usual rule of thumb is that you can EQ lumps down, but you can't fill in a hole. If you see a sharp dip, just move the mic a little and the dip will also change.

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

Post by digitaldrummer » Fri Apr 02, 2021 5:09 pm

by sliding up against the wall, it makes it much more difficult to access the back of the rack (which I don't do that often and hoping I will not have to any time soon...). But I also lost a "storage space" where I had some bass drum heads and guitars shoved back there. now I have to find a place to put that stuff! dang it.
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Re: The Truth Hurts - REW and my room...

Post by The Scum » Fri Apr 02, 2021 6:03 pm

That's what frequency response looks like, even in pretty good rooms. Use the psychoacoustic smoothing if you want it to look flatter :D

It doesn't look like you've got a hole around 100, you've got plateaus at 150-350 and 40-60, if you extrapolate the flat bit from 600 to 10K.

You can clearly see your room modes at 30/45/60.

Have you checked out an approximation of your room in the REW room simulator?

What's the time domain response like? Try the waterfall or spectrogram views. Those are the ones to really try to treat.
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Re: The Truth Hurts - REW and my room...

Post by digitaldrummer » Sat Apr 03, 2021 6:30 am

yeah, as I looked at it more I was coming to the same conclusion. a couple bumps in the low end and then some from 140-400 that I need to flatten out a bit (about 5dB) if possible. I will generate the waterfall diagrams and also look into the room simulator too (have not looked at it yet).

One other good thing that came of this is that while setting everything up, and while I had the pink noise being generated, I adjusted the volume a bit on my monitors. The FX80's have a volume pot that let's me get them really close to each other and to the other pair (BM6a mkii). The right BM6 is about 1dB louder than the left and it only has switches to adjust (I don't think they have any finer tuning but I will look closer). Then again, the FX80 seemed like it might have been a little louder too but I was able to adjust the volume. So I suppose that could be something in the room affecting that too. But I may re-check (outside of REW).
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Re: The Truth Hurts - REW and my room...

Post by MoreSpaceEcho » Sat Apr 03, 2021 7:48 am

That doesn't look that bad.

You're gonna hate me but you really want it on 1/24th smoothing. It's going to look worse. I'm sorry! But if you're within +/-10db at 1/24th you're doing pretty good. If you're within +/-5db you're doing amazing.

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

Post by digitaldrummer » Sat Apr 03, 2021 9:33 am

I'll try the 1/24th smoothing too.

here's the room sim (measurements are not exact since I have the vaulted ceiling - so I think I used 12ft instead of 10 or 15ft) and waterfalls. Seems like the time is fairly consistent.
roomSim.jpg
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leftFx80wf.jpg
leftFx80wf.jpg (173.42 KiB) Viewed 842 times
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rightFx80wf.jpg
rightFx80wf.jpg (171.42 KiB) Viewed 842 times
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Re: The Truth Hurts - REW and my room...

Post by roscoenyc » Sat Apr 03, 2021 10:00 am

I've got an anecdotal story for you that relates to your subject in a sort of 'more than one way to skin a cat' way.

When we first setup Cowboy Technical in it's first location on Hope Street in Williamsburg over 20 years ago (!?!?) we got going
there and started making records. Both my partner Tim Hatfield and I were using Scott Hull for almost all of our mastering.

I have always looked for input on my work from mastering engineers.
One time at Scotts after about a year in our Hope Street location, having completed over a dozen records, Scott had a comment.

He said that our mixes all seemed to have a dip in them around 100-150.
He asked about our setup and offered to come out and have a look/listen (good fortune of our location)

When he came out he listened from our spot at the console and suggested we move everything another 18 inches away from the wall.
We did that and while none of this was done with measuring gear it really helped our results drastically.

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

Post by MoreSpaceEcho » Sat Apr 03, 2021 2:14 pm

Lengthen the time display on the waterfall graph out to a second or more so you can see how long that stuff is really ringing out for.

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

Post by digitaldrummer » Sat Apr 03, 2021 7:20 pm

thanks everyone for the help on this.

ok, here's the time range out to 2000ms
leftFx80wf-2s.jpg
leftFx80wf-2s.jpg (189.51 KiB) Viewed 793 times
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rightFx80wf-2s.jpg
rightFx80wf-2s.jpg (189.64 KiB) Viewed 793 times
oh, and here's the 1/24 smoothing SPL
4-3-2021_15-400_24sm.jpg
4-3-2021_15-400_24sm.jpg (65.87 KiB) Viewed 793 times
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Re: The Truth Hurts - REW and my room...

Post by digitaldrummer » Sat Apr 03, 2021 7:24 pm

and I'm replying to myself because I think each post is limited to a few attachments...

Anyway, I went back to the "before" shots - and let me be clear I moved stuff around and even lowered the volume in the "after" shots (or I tried to, but it looks like I actually increased it. so weird..), so it's not a perfect science here... but I think the "before" might actually be better in the sense that the modes seem to be ringing much less. or is it that I did increase the volume in the "after" and excited the modes more?

So do I go back to where I started?

here's the SPL graph w/ 1/24 smoothing (so remember the scale shifted due to the volume change)
Before FX80.jpg
Before FX80.jpg (70.09 KiB) Viewed 793 times
left waterfall
left fx80 before wf 2s.jpg
left fx80 before wf 2s.jpg (155.76 KiB) Viewed 793 times
right waterfall
right fx80 before wf 2s.jpg
right fx80 before wf 2s.jpg (155.49 KiB) Viewed 793 times
Last edited by digitaldrummer on Sun Apr 04, 2021 6:48 am, edited 1 time in total.
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Re: The Truth Hurts - REW and my room...

Post by The Scum » Sat Apr 03, 2021 10:47 pm

40 hz ringing for over a second?

That's the textbook definition of mud!

It'll be easier to compare the before/after if the relative size of each axis is scaled the same, and the peaks fall on the same places. If the newer plots are 5 dB hotter, then everything is 5 dB higher. If you rescale the new ones to the 55 to 105 dB range, they might look similar to the older ones when you lose the shelf they appear to settle on.

(it might also help to include a little more of the mids/highs in those waterfalls so we can see what things look like both above & below the Schroeder frequency.)
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Re: The Truth Hurts - REW and my room...

Post by MoreSpaceEcho » Sun Apr 04, 2021 8:19 am

The difference in the graphs is for sure just due to the levels being different. If you raised up the level of the before you'd see everything ringing out the same as in the after. There's no way adding a bit of rockwool and moving your desk a bit would change the amount of decay that much.

The good news is your graphs really don't look that bad. The bad news is if you want to improve things further it's going to take a serious amount of treatment, a couple panels here and there won't make that much of a difference.

The ringing is the problem. If you shorten the decay, the freq response will flatten out as a result.

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

Post by The Scum » Sun Apr 04, 2021 12:06 pm

So here are a couple plots of my WIP room.

The room is maybe 23' deep, 11.5' wide and 10.8' tall. The initial treatment was a simple drop ceiling cloud - bare drywall walls, cement floor.

The treatment it's received are rockwool filling the cavity above the drop ceiling, and wall panels of 4" 703, with batt behind. It's similar to MSE's wall treatment.

Here's the initial frequency response and latest results overlaid, no smoothing. You'll notice that the initial curve has like 40 dB variance - with a couple exceptions, the new one much smoother overall.
freq-init-vs-latest.png
freq-init-vs-latest.png (52.16 KiB) Viewed 736 times
I knew the initial was going to be a mess, so I wasn't too careful in the test configuration...hence the upper limit at 1K.

You'll also notice I've got a situation similar to yours around 100 Hz. This is room boundary interference, and I've done nothing to the floor.

I usually use the spectrogram plot for comparisons...it's effectively looking at the waterfall from above, as it it were a topo map. The scales in the following waterfalls should be the same, to try to make comparisons easier.

Here's the initial waterfall...cut off at 1 sec, because anything that lingers that long is problematic. The measured RT60 was in the 800 mSec range.
before-waterfall.png
before-waterfall.png (246.79 KiB) Viewed 736 times
And here's the current state of affairs, 20-20K. Measured RT60 is maybe 150 mS, above 100 Hz.
after-waterfall.jpg
after-waterfall.jpg (153.12 KiB) Viewed 736 times
A couple other things to note.
  • First, it clearly shows the noise floor as an actual floor.
  • Those continuous fins at 180 and 360 Hz are likely switchmode interference from the audio interface power supply. They're there regardless of the sweep configuration.
  • Not sure what the ridge at 30 Hz is...maybe a truck idling outside?
  • 23 Hz and 45 Hz are still ringing, and I'm working on some different bass traps at the rear of the room to try to address that.
"What fer?"
"Cat fur, to make kitten britches."

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

Post by digitaldrummer » Sun Apr 04, 2021 12:57 pm

thanks guys. I used to have my desk setup at the long end of the room (the shorter wall - which is 19' wide), and had it about 3-4 ft from the back wall maybe. But in trying to strike a balance between, good sounding mixes, good sounding drums, and enough space to rehearse or track a band, I decided to move the desk to the longer wall (which is 27 ft long). I had not used REW back then (2+ years since I switched it around). I wonder if that would potentially help with some of the ringing? I'll look at the room sim too. Either way, I've got superchunks in every corner (OC703 stacked up 9 or 10 feet high). But that 15ft vaulted ceiling (with the 10ft walls) throws off every simulation tool... and of course I don't want to make the room completely dead either since I like it to open up a bit when recording drums.

speaking of decay, I had 2 drums kits setup in the room as well as another 24" kick drum that was not in a case/bag (and perhaps ringing a bit). I suppose that could also interfere with the measurements? But I usually always have one kit setup for sure.
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