Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 370 - AVS Forum
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post #11071 of 11077 Unread Yesterday, 06:11 PM
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Originally Posted by HDgaming42 View Post
Hi guys,

I finally moved my sub to the back of the room following all the advice I got way back here, and I completed and placed my bass traps. Here are my results.

My Room Sim was unusual as it suggested the most ideal MLP to be in the dead center of the room. This was it's prediction:



My result (didn't save it) didn't look anything like that (even a 1" movement in Room Sim seems to destroy this particular prediction. I found the ideal sub placement and MLP to be with the MLP 105" into the room, center width.

Room Sim's version of this placement:



This is a bit jumbled, but stick with me if you will. Here is a comparison of no treatment (red) to two full height corner bass traps up front (green) with two tweaks*. More on that later.



Waterfalls:



purple instead of red for some reason--but corresponds to the All SPL above it.


After spending nearly a month's worth of "free time" (which wasn't a lot TBH) I guess I was hoping for a flatter response.

Here's what I found interesting and could use some advice on (actually, I'm soliciting all advice on anything you see here!!).

I have a set of double, solid core doors with air-tight gaskets to enter the room. It seems like that is messing with my response!



By opening the interior door I drop a peak by a number of dB, and raise a null. The door cavity is airtight (double wall construction all around). I've read that drilling holes between the doors to provide airflow into the wall cavities can help...but now I can't dig up that advice. I was worried this would short-circuit my soundproofing. Thoughts? Advice? Also of note, my rack's plexiglass door was creating havok, and I removed it to get to the point you see as "best result", no plexi-door and one door open.

Here's where I'm at utilizing best placement, no plexi-glass door and one door open. Also, two 7ft tall bass traps (corner chunk Roxul Safe N Sound) in the front two corners.



Where do I go from here?
Room Sim doesn't seem to be able to come up with a 2nd sub fix for this room. The back wall is problematic as it has those double doors, and a cubby for the equipment rack. There is really only four feet of treatable area on the back wall.

I'm open to all suggestions--really interested in your thoughts on drilling holes (how big, how many?) between the casing of the two double doors. Would love to be able to keep my (expensive!) plexi door for my rack too...

Feeling...defeated.

PS I tested pulling the traps away from the wall (they're free-standing) in 1" increments. I could see no benefit going beyond 1". I went all the way to 8", which was the maximum feasible in my room. My traps are faced with 6mil poly.
Bumping this for HD...hoping someone smarter than me has some good advice!

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post #11072 of 11077 Unread Yesterday, 06:24 PM
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@hdgaming : The treatments seem to be making a small difference, but IIUC, you only have two bass traps, correct? Based on the waterfalls, which are showing severe bass ringing, you will need quite a few more traps to make a measurable difference. Remember, traps are most effective when they straddle a corner, not when they are placed flat on the wall. If you look at the pictures of my room (My Setup link in my sig), you will see that I use the intersection of the wall and the ceiling as spots for bass traps, as well as every available intersection of two walls, and even a ceiling cloud. It takes a ton of traps to fix a bad ringing problem--don't know if WAF is a factor, but a ton of traps is not always that visually attractive.

The frequency response is not terrible, but could be better. I have been using REW for years, and have NEVER used the room sim tool. Shows you what I think about that feature. IMO, additional subs are your best bet to improve frequency response, as well as "real" sub placement experiments (not the room sim).

I don't know what to say about the door. Personally, I would leave it alone. You have other options--more subs, better placement, more traps, room EQ, etc.
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post #11073 of 11077 Unread Yesterday, 08:06 PM
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Jerry,

HDs waterfalls aren't scaled right, his lower limit is set to 25db. Should be more like 45 or 50....they'd look much better if they were scaled right.

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post #11074 of 11077 Unread Yesterday, 08:15 PM
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Good catch, you are correct. HDGaming, how about some updated waterfalls? To be consistent with what we normally see, set the lower limit to 50Hz, and the time scale to 450 (not 500).
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post #11075 of 11077 Unread Today, 09:24 AM
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Quote:
Originally Posted by Alan P View Post
Bumping this for HD...hoping someone smarter than me has some good advice!
Quote:
Originally Posted by AustinJerry View Post
@hdgaming : The treatments seem to be making a small difference, but IIUC, you only have two bass traps, correct? Based on the waterfalls, which are showing severe bass ringing, you will need quite a few more traps to make a measurable difference.
Quote:
Originally Posted by Alan P View Post
Jerry,

HDs waterfalls aren't scaled right, his lower limit is set to 25db. Should be more like 45 or 50....they'd look much better if they were scaled right.
Thanks guys. Here are corrected waterfalls:

Before Treatment



After Treatment



Truthfully that looks MUCH better! I'm actually surprised the ringing isn't worse in a room with nothing in it but a subwoofer and two (four 1/2 height) bass traps.

It seems 50Hz is the lowest my traps are having a meaningful effect. That null in the 40s will have to be tackled with another sub I suppose? I could probably do ceiling/wall traps or a cloud trap...the rest of the room will be difficult. Hell, I'll take some pictures to show you guys what I'm working with--I appreciate the pics you've posted of your rooms. Let's me get an idea of what it takes!

Have a pretty packed weekend, so pics might not be right away. I'll be checking back for feedback regularly though.

Not sure this is of any use, but here's an after treatment Spectrogram, which I'm equally sure isn't scaled correctly.



EDIT: I just noticed that ringing got WORSE at 17Hz and 20Hz with treatment. Or maybe that's because of the open door...
Attached Images
File Type: png spectrogram.png (450.8 KB, 2 views)
File Type: png treated and doors open - waterfall.png (157.8 KB, 3 views)
File Type: png baseline no treatment - waterfall.png (259.9 KB, 3 views)

Last edited by HDgaming42; Today at 09:28 AM.
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post #11076 of 11077 Unread Today, 09:40 AM
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I would focus on frequency response smoothness for now. The revised waterfalls don't look too bad. A suggestion on your measuring technique for the waterfalls. Ideally, you should aim for a measurement level that is approximately 40dB above your measured noise floor, which of most of us is around 50dB. If you look at the scale on the right of the spectrogram, you see a range of 39-79dB, which is the level of your measurements. I would aim for a peak of 90dB, and then use 50-100dB as the vertical scale on the Waterfall. As it is now, with such a low measurement level, the lower limit on the waterfall should be 40dB, which will alter how the graph looks significantly. Waterfalls are tricky to display, as well as to interpret.

And the tiny blip on the after waterfall at 20Hz should not cause any concern at all. It is probably not audible.
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post #11077 of 11077 Unread Today, 10:00 AM
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Quote:
Originally Posted by AustinJerry View Post
I would focus on frequency response smoothness for now. The revised waterfalls don't look too bad. A suggestion on your measuring technique for the waterfalls. Ideally, you should aim for a measurement level that is approximately 40dB above your measured noise floor, which of most of us is around 50dB. If you look at the scale on the right of the spectrogram, you see a range of 39-79dB, which is the level of your measurements. I would aim for a peak of 90dB, and then use 50-100dB as the vertical scale on the Waterfall. As it is now, with such a low measurement level, the lower limit on the waterfall should be 40dB, which will alter how the graph looks significantly. Waterfalls are tricky to display, as well as to interpret.

And the tiny blip on the after waterfall at 20Hz should not cause any concern at all. It is probably not audible.
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