REW and my room.

[HMacFidelity]

First time caller. Learning. A place to gather my thoughts. Please excuse the clutter.

Llistening room measurement. Trying to get a baseline.

24’x15’x8’ room.

Speakers 8ft from front wall, 5ft between the speakers centered on the rooms width.

Sub rear ported. Rear edge of sub 16” from the front wall, centered on the width.

This measurement done with mic 14’ from the front wall. Centered on the width.

L+R+Sub not individual measurement.

Umik-1 Zero degree calibration. Mic at listening position. Mic pointed between the speakers.

updated zero degree Mdat

L+R+SUB baseline.mdat

drive.google.com

Questions, comments, concerns, feel free. Just trying to get a handle on the software as I work on the room.

H

for my own reference.

Taking and Interpreting Measurements with REW (FREE eBook)

A few years ago, Amir wrote Room Measurement Tutorial for Dummies Part 1 and Part 2. The third part has never materialized despite many requests. In the meantime, there is a clear need for clear guide on how to take room measurements because we are seeing more and more people take and post their...

www.audiosciencereview.com

 

[waofner]

40 Hz resonance easy to EQ; weird from 1800 Hz upwards:

Try generator pink noise + RTA, moving microfone method also helps.

 

[HMacFidelity]

some housekeeping -

Mic was at listening position. 90 degree calibration file. Mic pointed between the speakers.

 

[DVDdoug]

Mic was at listening position. 90 degree calibration file. Mic pointed between the speakers.

I believe 90 degrees expects the mic to be pointed up at the ceiling. But at low frequencies it won't make a difference.

At higher frequencies the reflections "get crazy" and slight changes in mic position (or listening position) make a big difference so it's usually best to use the moving-mic method to average it out, or just make gentle high frequency adjustments by ear and don't try to make it "perfect".

 

[HMacFidelity]

I believe 90 degrees expects the mic to be pointed up at the ceiling. But at low frequencies it won't make a difference.

thanks for catching that.

I'll work on getting proper measurement.

 

[HMacFidelity]

Cleaned up the first post with updated mdat.

 

[Ktacos]

I'd suggest measuring L and R and Sub individually and repost the mdat.

 

[HMacFidelity]

I'd suggest measuring L and R and Sub individually and repost the mdat.

absolutely, should be coming soon.

 

[uriy-ch]

Measure only the left speaker, then only the right, and then both together. This will make it clearer if there are dips in the measurements of both speakers.

Judging by the pulse of your measurements, one speaker is positioned slightly further from the microphone than the other. If this is indeed the case, the frequency response will show interference pits and humps not only due to the room but also due to the different distances between the microphone and the speaker.

 

[HMacFidelity]

Judging by the pulse of your measurements, one speaker is positioned slightly further from the microphone than the other. If this is indeed the case, the frequency response will show interference pits and humps not only due to the room but also due to the different distances between the microphone and the speaker.

Thanks for taking the time. A very likely scenario. Trudging along by ear up until this point.

 

[Keith_W]

Some general observations about those measurements:

1. No timing reference
2. The measurements should be of individual speakers and every sub. This way, if you see something funny in the summed curve, you can diagnose the cause since you at least know which speaker is responsible.
3. The "room decay" measurements, i.e. RT60, spectrogram, and ETC are all very good. Your room is comparable in size to mine and your room decay measurements are better. You have some kind of room treatment/absorption, yes?

Anyway here are a couple of flaws:

See that rising treble response? The book gives a list of the usual culprits. The most common is measurement error, i.e. using the wrong calibration file for the wrong mic orientation. I can tell it's not furniture reflection (no reflections on the ETC) or distortion (it is commendably low). So it's going to be either measurement error or something wrong with your speakers.

That subwoofer impulse is arriving very late. It's probably just late enough to make the sub sound disconnected and "slow". You might want to do something about that.

Slowly go through the book and compare your own measurements with what you see. If there is something you don't understand, just ask!

 

[HMacFidelity]

Some general observations about those measurements:

1. No timing reference
2. The measurements should be of individual speakers and every sub. This way, if you see something funny in the summed curve, you can diagnose the cause since you at least know which speaker is responsible.
3. The "room decay" measurements, i.e. RT60, spectrogram, and ETC are all very good. Your room is comparable in size to mine and your room decay measurements are better. You have some kind of room treatment/absorption, yes?

Thank you Sir.

I'll be reading the book tonight.

More on the room -

Undeveloped basement. Cement slab floor with a single, fairly thick, rug between the chair and speakers. Exposed joist ceiling. 15.25" opening between joist, 14" from the bottom of joist to plywood floor.

Sidewall first reflection are freestanding 4'x8'x9" absorbers. 3.5" pink fluffy 3.5" rockwool comfort batt 1" rockwool comfort board.

Front wall first reflection 2x4'x5" 3.5' pink fluffy 1" comfort board, centered at tweeter height. The front wall and 8ft of the side walls are covered in 4x8x3/4" sheets of sonopan to be covered in fabric.

Rear wall 4x4'x9" 7" pink fluffy 2" comfort board centered on the wall. To the left and right of the absorber are "depot diffusers" stepped diffusers. 34.5" wide.

Rear side wall 4ft from the rear wall stand 2 more depot diffusers. The diffusers are mounted flush to the wall.

Only furniture is the listening chair and temporary placement of a air hockey table.

And, as of tonight, 2 bags of r40 and enough lumber for 3 24"x24"x8' corner traps.

 

[HMacFidelity]

New measurements. Left, right, sub and all three together. Furnace was on.

https://drive.google.com/file/d/1MPL0se8El_NAyqEnqz8DvzwG7XEYkDac/view?usp=sharing

 

[Keith_W]

Re: your new measurements. The most important speaker that needs a timing reference (the sub) does not have a timing reference. Go back and redo them.

 

[HMacFidelity]

Oh geez!

 

[HMacFidelity]

I measured again. Before I post them, I changed the sweep to 20-200hz, mains still connected. Is this enough for proper measurement?

 

[uriy-ch]

New measurements. Left, right, sub and all three together. Furnace was on.

Stereo is no longer an issue.

-Modal oscillations at 628Hz raise questions.


-The subwoofer's cutoff frequency is slightly higher than the speaker's, resulting in a slight frequency response bump at 60Hz.

In general, if you want a good, detailed consultation based on your measurement results, chat jpt can read REW files and can clearly answer any of your measurement-related questions.

 

[Keith_W]

I measured again. Before I post them, I changed the sweep to 20-200hz, mains still connected. Is this enough for proper measurement?

Provided it's well above the XO frequency of the sub, which I suspect it is, it would be adequate.

 

[HMacFidelity]

Let's try that again.

dec 31.mdat

drive.google.com

 

[HMacFidelity]

I notice something different between the speakers around 100hz. On the “all spl” graph, they cross near 100hz. ChatGPT suggests sbir.