Analyzing Room EQ Wizard graphs

aesthetiical
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Analyzing Room EQ Wizard graphs Jan 17, 2019 23:58:56 GMT

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Post by aesthetiical on Jan 17, 2019 23:58:56 GMT

Hey,

I was recommended to post here regarding my room acoustics. My Behringer ECM8000 came in today and I did a few tests with Room EQ Wizard to compare my room with and without treatment, and am trying to make sure I can fully interpret the results before I commit to anything treatment wise.

These are the REW graphs, and here also are the REW files. The graphs confirm that there is a huge peak at 130hz, which I was going to treat with a couple thick panels; before taking these measurements I planned on buying a couple of cheap Ikea bookshelves (like this) and filling them with a bunch of leftover insulation that I have (covering them with fabric), giving me two 9.5 inch panels for the front corners. I'd then use the insulation in my current panels to instead make 7 inch panels for the early reflections.

My room for reference is 398x279x256cm or 13x9'1x8'4ft and looks like this (the desk + monitors are now very close to the front wall). The current treatment used in the REW tests are four absorber panels made with this 90mm insulation on the two mirror points for the early reflections, as well as two on the back wall/closet.

In regards to reverb, I can instantly hear that there is a dramatic improvement with the treatment, however the frequency difference looks like it might be negligible. I used a calibration file for the microphone but did not calibrate my interface or do an accurate SPL meter calibration.

Just trying to make sure if these tests were done correctly and if going ahead with building the thicker panels is a good idea, in addition to testing some other listening positions.

Thanks for any help!

Michael Lawrence
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Analyzing Room EQ Wizard graphs Jan 18, 2019 1:14:46 GMT

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Post by Michael Lawrence on Jan 18, 2019 1:14:46 GMT

Welcome, Aesthetiical -

I've already given you my $0.02 via the other post, but I'll paste the relevant portions here as well just so the discussion will be complete. The acoustics nerds should be along shortly with additional insight on the setup and treatment options, and I'll ping Ethan as well. Maybe he'll have some wise words for you. In the meantime, do check out the stickies on this board for some good foundational information on this topic. //

Due to the way the analyzer does its calculations, you get a data point every X Hz, which means as frequency increases you get more and more data points per octave. This looks inconsistent, gives us far too much data to be helpful at HF (we call it 'grass') and is also not really consistent with the way our ear hears things. So a little bit of smoothing of the plots can help. After smoothing is applied, you can overlay both measurements to see the trends. I see a slight reduction in HF which is consistent with treating a relatively small surface area with relatively thin panels like you said.

i.imgur.com/soCVcY6.png

It also appears that you may have measured with both L + R channels on. Try not to do this - it creates a comb filter - try measuring them independently. I would point to that as a likely culprit for the HF response.

But with treating early reflection points, the real action is in the time domain. Overlaying the two impulse response measurements shows the reduction in reverberation time you perceived:

i.imgur.com/hdzYHvH.png

I don't see any truly troubling early reflections in the "pre treatment" data, which is looking really nice and clean for a small room.

Looking at your waterfalls, you're not in terrible shape for such a small room. A room that size will never be perfectly flat, but you will be able to even things out a little bit more with some bass traps.

Last Edit: Jan 18, 2019 4:20:13 GMT by Michael Lawrence

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Ethan Winer
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Analyzing Room EQ Wizard graphs Jan 18, 2019 17:12:05 GMT

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Post by Ethan Winer on Jan 18, 2019 17:12:05 GMT

The graphs are labeled With and Without treatment, but your post lists only proposed treatment in a bookcase, and the graphs look nearly identical. I can tell you that bookcase is not a good idea for bass traps that straddle a corner. The rigid back removes the advantage of a corner air gap behind the insulation.

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aesthetiical
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Analyzing Room EQ Wizard graphs Jan 19, 2019 1:03:26 GMT

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Post by aesthetiical on Jan 19, 2019 1:03:26 GMT

Jan 18, 2019 17:12:05 GMT Ethan Winer said:

The graphs are labeled With and Without treatment, but your post lists only proposed treatment in a bookcase, and the graphs look nearly identical. I can tell you that bookcase is not a good idea for bass traps that straddle a corner. The rigid back removes the advantage of a corner air gap behind the insulation.

I mentioned in my post that my current treatment - the treatment used in the 'with treatment' REW graphs - consists of four absorber panels made with this 90mm insulation (https://www.bunnings.com.au/earthwool-r2-5hd-90-x-580mm-9-42m2-wall-acoustic-and-thermal-batts-14-pack_p0810603) on the two mirror points left and right from my listening position for the early reflections, as well as two on the back wall/closet. I'm not entirely sure why there doesn't seem to be much of a change on the graphs, I'll do another test today to make sure.

Do you think that if I didn't install the back of the bookshelf and instead put fabric over it, that it would suffice?

Last Edit: Jan 19, 2019 1:05:01 GMT by aesthetiical

rock
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Analyzing Room EQ Wizard graphs Jan 19, 2019 1:41:15 GMT

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Post by rock on Jan 19, 2019 1:41:15 GMT

Right, like Ethan said, "The rigid back removes the advantage of a corner air gap behind the insulation." So, yeah, take off the back. Breathable fabric is OK on the back. For better LF performance, a thin membrane of paper or plastic over the front.

Your RFZ absorbers on the wall are good but you still have reflections from the ceiling and floor. (My wife just bought a 2" thick shag throw rug from Costco for the living room, something like that might be good at the floor reflection area.)

As for your measurements, you might experiment with slight changes of mic (listening) position. Adjustment of speaker position can influence measurements too.

aesthetiical
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Analyzing Room EQ Wizard graphs Jan 19, 2019 1:55:24 GMT

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Post by aesthetiical on Jan 19, 2019 1:55:24 GMT

Jan 19, 2019 1:41:15 GMT rock said:

Right, like Ethan said, "The rigid back removes the advantage of a corner air gap behind the insulation." So, yeah, take off the back. Breathable fabric is OK on the back. For better LF performance, a thin membrane of paper or plastic over the front.

Your RFZ absorbers on the wall are good but you still have reflections from the ceiling and floor. (My wife just bought a 2" thick shag throw rug from Costco for the living room, something like that might be good at the floor reflection area.)

As for your measurements, you might experiment with slight changes of mic (listening) position. Adjustment of speaker position can influence measurements too.

Yeah I'll have a look into a rug and am about to try some other listening positions, but anyway here's a test I just did, with and without my absorbers again, left monitor only (original post was right monitor). Still don't see too much of a difference