Verify my testing procedure

[Dange]

Originally Posted by kasmira

Now, I have seen tests done with the mic in a tri-corner (usually, ceiling-wall-wall corner) - why is this done?

You can couple to all room modes from a tri-corner. So for measuring modal response the loudspeaker should be placed in a lower corner and the mic in the diagonally opposite upper corner.

Originally Posted by kasmira

Should I use the windscreen with the Behringer ECM8000?

Only if there is a breeze in your room, also I wouldn't bother with calibration files in REW for the mics especially as this is a comparison test for the same room.

[kasmira]

Originally Posted by Dange

You can couple to all room modes from a tri-corner. So for measuring modal response the loudspeaker should be placed in a lower corner and the mic in the diagonally opposite upper corner.

Only if there is a breeze in your room, also I wouldn't bother with calibration files in REW for the mics especially as this is a comparison test for the same room.

Thanks for the pointers, Dange! Also, at a breeze in my room - I will have to save that one for later!

[gullfo]

it's useful to capture the "room" response with the opposite corners but if this is a critical listening room, then you'll want to make the majority of measurements @ the listening position(s). once you set up the corner traps your corner to corner measurement will be skewed somewhat but ultimately should show you how the treatments have affected the room in total, the listening position tests will ensure not only proper frequency and phase response, but also reflections.

[Glenn Kuras]

Four 4' x 15" x 15" soffits made of R30 (stacking two on top of each other for full floor-to-ceiling traps on my front wall-wall corners)

Having 4 traps in a room is a good start but that is really all it is, so don't look for outstanding results. There is a reason why Ethan has 40 traps or so in his room. Kidding you don't need that much, but just saying. Also 15"x15" are kind of small. Yes they will work but...........................
If I where you I would not worry about the SBIR for now and put all of those traps you have now in corners (straddle the panels). Then follow up with MORE panels for the early reflection points. Measure (actually measure before hand to see progress), see how things look, then treat from there.
Not sure why you want to measure with 2 mics. All that matters is the mix spot. Focus on that for now.

edit.. I just got a note from someone about my comment of "4" traps. What I mean is covering floor to ceiling in only 2 corners. I ASSumed he made each soffit trap 4' high and his ceiling is 8'.

[DanDan]

The Spectrum Analyser in REW can be used for an instant hit.
This is especially useful for quick BIR warnings.
e.g run the analyser no smoothing, with the special Pink supplied in REW.
Move the speakers towards and away from local boundaries. All becomes revealed instantly. Write down the warnings, i.e. deep nulls.
I don't think REW can do multichannel Recording.
FuzzMeasure can.

DD

[kasmira]

Originally Posted by gullfo

it's useful to capture the "room" response with the opposite corners but if this is a critical listening room, then you'll want to make the majority of measurements @ the listening position(s). once you set up the corner traps your corner to corner measurement will be skewed somewhat but ultimately should show you how the treatments have affected the room in total, the listening position tests will ensure not only proper frequency and phase response, but also reflections.

Thanks for the info Glenn! I will be doing my measurements at listening position then.

Originally Posted by Glenn Kuras

Having 4 traps in a room is a good start but that is really all it is, so don't look for outstanding results. There is a reason why Ethan has 40 traps or so in his room. Kidding you don't need that much, but just saying. Also 15"x15" are kind of small. Yes they will work but...........................
If I where you I would not worry about the SBIR for now and put all of those traps you have now in corners (straddle the panels). Then follow up with MORE panels for the early reflection points. Measure (actually measure before hand to see progress), see how things look, then treat from there.
Not sure why you want to measure with 2 mics. All that matters is the mix spot. Focus on that for now.

edit.. I just got a note from someone about my comment of "4" traps. What I mean is covering floor to ceiling in only 2 corners. I ASSumed he made each soffit trap 4' high and his ceiling is 8'.

Firstly, you ASSumed correctly (But I think the note that you received is because I have 4 soffits, as well as 7 other traps). I made four 4' tall soffits, and will be stacking one on another, so my two front wall-wall corners will have the soffits in them. I realize that 15" soffits aren't the best you could do - but my frequency response was already pretty good in my room, and it was the only practical size. For 17" I'd have to chop a fiberglass bat in half, then in half diagonally, then in half diagonally again...wouldn't be fun to do. I also toyed with the idea of 24" soffits, but 15" wide rolls were on sale for $12, which was enough to make all four soffits. Couldn't pass up that deal.

I have 11 traps in total. 4 soffits, 5 four inch thick + three inch airgap, and 2 six inch deep traps. The soffits honestly didn't do a ton of damage but they still helped. I think they would work MUCH better in the back corner of my room as that's where my big 55hz resonance is built up at, but I unfortunately can not place them back there.

Also, I didn't necessarily want to or assume I needed to use two mics. I just have two of them, so I wasn't sure if I could use both of them to benefit the testing set up.

Thanks for the response Mr. Kuras

Originally Posted by DanDan

The Spectrum Analyser in REW can be used for an instant hit.
This is especially useful for quick BIR warnings.
e.g run the analyser no smoothing, with the special Pink supplied in REW.
Move the speakers towards and away from local boundaries. All becomes revealed instantly. Write down the warnings, i.e. deep nulls.
I don't think REW can do multichannel Recording.
FuzzMeasure can.

DD

Forgive me for addressing your post backwards:

I don't have a Mac, so I can't use FuzzMeasure, but thanks for the tip on that.

I have so much trapping around my speakers, I feel like I really don't have too much bias coming from BIR, but I haven't played with the math yet to exactly see around what frequency I should be looking around. The 55hz modal resonance is easily my biggest problem, but even then its down 40db within 200ms. Is 40db down a pretty decent start to knocking it down there?

I've used the spectral analyzer in REW but did it with a sine wave - but I didn't do it to position my speakers. I'll keep the pink noise in my mind for when I do tests to find the optimum listening position.

Thanks for all your advice so far in my journey, Dan, its greatly appreciated!

[kasmira]

Bump.

I'm getting my new monitors (Event 20/30s) hopefully on Wednesday. I wanted to wait on these tests as my current speakers (Rokit 5s) completely die below 50hz. I will be making these measurements within the next few weeks when I have time.

Until then, does anyone care to chime in about how to properly position a mic for testing? I know the obvious bit about not moving it - the mic stand will stay in the same place the entire time, but I'm not sure on how to place it at listening position properly to stay away from comb filtered effects from both speakers. I want an accurate ETC measurement in this process. Thanks for any links or help anyone can provide!

[DanDan]

I feel like I really don't have too much bias coming from BIR

The biggest BIR NULLS often come from the back wall.

For a full Modal picture place a speaker on the floor in the front corner (or both). Place the mic in the opposing back corner, on the floor or at the ceiling.
For Frequency Response place the mic where your ear is. Drive one speaker only, and there will be no comb filtering from the speakers at least.

DD

[Syncamorea]

Bumping for data. How is this project progressing?

[kasmira]

Though I've ran a few tests myself, I haven't had time to take everything out and do multiple measurements unfortunately. I really do want to publish the results so people can know what to expect from *some* treatment in a room.

Right now I'm currently doing some tech stuff (wiring up some patchbays, fixing the routing situation, etc) at a friend's studio, along with building him 16 - 2'x4' absorbers, full 16" x 16" floor to ceiling corner traps, and 4 - 4'x8' gobos for his 27' x 12' studio, along with working three jobs (plus producing) so my head will explode if I add anything else