Help reading waterfall

[Thrashin Vamp]

I snagged the Room eq wizard from Home Theater Shack and used a Radio Shack spl meter to shoot my room from listening position. I've done this before with a tone generator I got from here and it showed problems around ~100 hz, which I notice closer to 110.

This is what the new test gave me.





What does it mean I thought it would look very close to my other data, but it looks much... better! I think.

I'm ready to pull the trigger on some massive bass traps to help my 110 problem, but what should I be fixing based on this?

[Ethan Winer]

Your graphs show too large a vertical range. Re-plot with a vertical range of 30 dB, with the peaks just hitting the top of the graph. Then for the waterfall plot set the time (front to back) long enough so the you can see where "mountains" fall through the floor. Like the ETF graph below.

--Ethan

[Thrashin Vamp]

Is this better?


Still have 60 db res, but I had to go that big to get any drop off. I can just do it again if needed!

[Ethan Winer]

This still looks strange to me. How big is your room? Can you make the time (front to bacK) even longer?

--Ethan

[avare]

Originally Posted by Ethan Winer

This still looks strange to me. How big is your room? Can you make the time (front to bacK) even longer?

+1 It looks like coupled spaces. An L shaped room. An open hallway or large closet of sort. A weak wall(s) with a stronger one behind it. Or something else.

Dimensions and shape are definitely needed.

Andre

[Thrashin Vamp]

Here it is. The drawing isn't dead to scale, but the measurements are on. The small rectangle on top is an empty room on the west, my iso-booth in the middle-ish, and a 18 inch deep closet on the east. There is another closet on the east side of the 40 inch hall, and on the other side of the east wall is a 8 foot wide room of unfinished basement. All walls are 2x4 with insulation, and the ceiling is 93 inches high with r13 on top of drop in tiles. I have a 2x4 foot cloud over the mix point, and foam, including foam bass traps, on the walls.

I'll put up another waterfall tomorrow with longer time, but it won't be until afternoon CST. Thank you guys!!



This pic is a little old, I'm now farther from the wall, but you can get the idea. And no, I can turn to run the long way, the wife insists it's a house first, studio second!

[Thrashin Vamp]

Here's some new graphs and some questions with a finer point on them.

1.Would I benefit from more bass trapping, or do I need something else first?
2.If bass traps are the answer, would I benefit from placing them at the front or the back of the room?
3. Do I have a dip at 110 as I hear, or do I have a bad masking problem from other freq's bouncing around the room?

Thanks again!!

[Ethan Winer]

Originally Posted by Thrashin Vamp

1.Would I benefit from more bass trapping, or do I need something else first?

You'll always benefit from more bass trapping.

Do I have a dip at 110 as I hear, or do I have a bad masking problem from other freq's bouncing around the room?

I still don't find that graph believable. If you email me the REW data file I'll be glad to load it up here and take a closer look. Click the RealTraps link in my sig below and email me from the Contact page.

--Ethan

[avare]

Originally Posted by Ethan Winer

I still don't find that graph believable. If you email me the REW data file I'll be glad to load it up here and take a closer look

+1. It is very strange. Any idea what the measuring mic location is?

Andre

[Thrashin Vamp]

Ethan, I'll get it out to you today, thanks!

As for where I did the shoot from, if you look at the actual pic the chair is sitting just about where I mix from now (the desk is at least a foot farther from the wall and the speakers are now on the desk). I held the meter at head level and moved my head out of the way. When I did the other shoot and found the 110 hole I had the same meter on a stand and stood well away from it while graphing the readings.

[avare]

What is the height to the hard ceiling above the suspended ceiling and what is hard ceiling made of?

Andre

[Thrashin Vamp]

102 1/2 inches and OSB. (That's from cement to OSB, I have a pergo subfloor and pad that might be 3/8th thick total in the room in question if those numbers matter for bass) So 9.5 inches between suspended and hard, and there is r13 in the joists, not actually sitting on the suspended tiles.

[Ethan Winer]

Originally Posted by Thrashin Vamp

Ethan, I'll get it out to you today, thanks!

I can't tell what is wrong with your file, but I'm pretty sure it's not right. Maybe the recorded signal was very low? But it's clear that the data is not valid because it doesn't come even close to matching the response you plotted by hand using my test tone CD. The manual plot looks more or less normal, with 20 dB nulls around 90 and 120 Hz. Your REW graph has a 10 dB null around 80 Hz.

When you ran the REW tests was the sweep tone reasonably loud? Did you look at the level meters in REW to confirm both were in a reasonable range?

--Ethan

[Thrashin Vamp]

It said I was getting 105 db on the test, but it told me I was close to -20 on something and that I should be at -10 or less. I'll go try again and see if I can get some higher numbers.

[Thrashin Vamp]

Had to switch from my normal inputs and use the front mic/line inputs on my motu 828 mkII to get high enough levels. I also used the calibration for the spl meter I'm using. Here are the new shots. The top one is 38 to 300, the bottom is 17 to 150. Ethan, I'll email you the data file again.

[Ethan Winer]

Originally Posted by Thrashin Vamp

Ethan, I'll email you the data file again.

It still looks too good to be true, and I still don't understand the disparity between REW and the hand plots you made using my test tones. Was the microphone in the same place for both tests?

--Ethan

[Thrashin Vamp]

Dawned on me, the spot stayed the same (~38% of the room) but I moved the speakers this summer when I bought my new monitors. I'll retake the test cd and see if they match up.

But just with the waterfall, what would be a good next step? I'm still thinking of two larger bass traps near the back of the room (one at the end of the hall and one behind mix position), but would I be better off with some diffusion or something else first?

[Thrashin Vamp]

Here's the test cd results. Pink noise was at 75 db.



Any recommendations or ideas?

[Ethan Winer]

More bass traps. That's the only solution.

--Ethan

[Thrashin Vamp]

Additional ones in the front (side corner and ceiling corner...) or should I start adding to the rear of the room? Should I focus on the dip at 80, or knocking down 120-300?

I assume it isn't as easy as just trapping more corners, aren't there some size and depth issues I should be looking for to target my specific problems??

[Ethan Winer]

Don't "focus" on anything except getting as many bass traps into as many corners as you can manage.

This may help also:

Pink noise aids placing bass traps

The idea is to play the bassy pink noise, then listen or use an SPL meter to find which corners have the most bass build-up. Wherever the bass builds up the most, that's where traps are needed.

--Ethan

[Weasel9992]

Originally Posted by Thrashin Vamp

I assume it isn't as easy as just trapping more corners, aren't there some size and depth issues I should be looking for to target my specific problems??

At the point you're at, there really isn't any more to it than covering square footage in critical spots. After you cover all the basics, *then* we can talk about targeting certain things. If you've still got the LNRDs in the corners and the foam on the front wall, there's part of the issue right there, but all of the corners, the front wall and the back wall are the first suspects.

Frank

[Thrashin Vamp]

At the point I'm at?? I thought I had covered the basics 5 years ago on the recomendations of Auralex. Every now and then the whole thing seems like cat bones and mojo with no one being willing to show their math.

And what part of the issue are the bass traps and foam I have up? I have the ceiling of the front wall done, the corner of the left/front wall done, and the floor AND ceiling of the left wall done. My right wall is 35 feet away from my mix point, and the back wall doesn't have hard corners until almost 17 feet from mix point.



I used the bass test tone to see what corners are loading up, and the only one that changed more than 3 db from the open space around it was the corner I have the most trapping in already. I was already planning on putting a large trap there, and from what has been said it looks like it will make a difference. I have to figure out a place to put some on the rear wall, I assume that will be trial and error.

I'll start there and see what I end up with. Thanks much to everyone that helped so far, especially Ethan for help in getting the numbers right.

[avare]

Originally Posted by Thrashin Vamp

At the point I'm at??

You at the point with a problem in a room that no one here can go to and inspect. It might obvious to a trained eye and ear, but they are not there. I am wondering if some is vibrating at those frequencies.

Andre

[Weasel9992]

Originally Posted by Thrashin Vamp

At the point I'm at?? I thought I had covered the basics 5 years ago on the recomendations of Auralex. Every now and then the whole thing seems like cat bones and mojo with no one being willing to show their math.

And what part of the issue are the bass traps and foam I have up? I have the ceiling of the front wall done, the corner of the left/front wall done, and the floor AND ceiling of the left wall done. My right wall is 35 feet away from my mix point, and the back wall doesn't have hard corners until almost 17 feet from mix point.

Sorry...on reading that a day later my post was more critical than I meant it to be. I meant nothing personal by it. I know this stuff seems cryptic, and the fact is that much of the science of acoustics is not intuitive...at least not until you know the physics pretty well.

Part of the issue is that foam simply doesn't work very well in the corners...it's not that it doesn't work in any application, it's just that bass trapping isn't a great one. I'm not sure why anyone would tell you to put 2" foam on a wall when your monitors are right up against it...that's one of the basics I was talking about. The fact that your right wall is 35' from the mix position when your left wall is just a few feet away presents another basic issue from a positioning standpoint. Even though your back wall is 17' behind you it's still going to be the source for some of your deepest nulls and highest peaks.

What we're saying with respect to your waterfall display is that it doesn't make sense...there's a disparity between the waterfall and the graph that throws everything into question.

Frank