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What to do for acoustics
Old 8th June 2009
  #1
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What to do for acoustics

I just tested my room and was really surprised at how good the bass was. From the graph you can see that everything between like 40 hz to around 300 was within around 5dbs. This is insane I think as my room has no treatment except some blankets hung in first reflection points and the closet full of clothes and pillows. A picture of my room is also attatched.

So what should I do to smooth out the higher frequencies?
What to do for acoustics-room-graph.jpg
Old 8th June 2009
  #2
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sorry forgot the pic of the room
What to do for acoustics-bedroom.jpg
Old 8th June 2009
  #3
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I am still trying to figure out room eq wizard to post my graph. You bass response looks great but does it supposed to look that good? In my graphs the bass is always rolled off and I have 12 4" traps in my room including the 4 wall to ceiling corners.

If the base is supposed to look like that than I am just too damn jealous.
Old 8th June 2009
  #4
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Quote:
Originally Posted by RonT View Post
I am still trying to figure out room eq wizard to post my graph. You bass response looks great but does it supposed to look that good? In my graphs the bass is always rolled off and I have 12 4" traps in my room including the 4 wall to ceiling corners.

If the base is supposed to look like that than I am just too damn jealous.
I know! I've seen some graphs on here and in books and stuff, but nothing has ever been that good! At first I didn't believe it and thought something must be wrong with my mic or something, but then I went through the realtraps test tone CD and every frequency sounded about the same level!

I'm pretty sure the goal of room treatment is to get all the frequencies to about the same level, and that's what is happening in my 20-300hz range.

I'm almost scared to change anything to fix the higher frequencies because I've heard the lows are the hardest to get right.
Old 8th June 2009
  #5
Gear Maniac
 

Where exactly did you make the measurements in your room? I assume at the listening position, but where exactly is that?

From the graph, it appears there's a resonance at 600Hz causing a null at 600Hz, 1.2kHz, 1.8kHz and 3kHz as well as a peak at 2.4kHz.

There are certainly more modes excited, like the one at 800Hz and the first harmonic at 1.6kHz plus lots more above them.

Depending on where you listen, a skyline diffuser tuned for a low frequency of 600Hz could help diffuse backwall reflections that cause the nulls.
Old 8th June 2009
  #6
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I'm in the center of the room the short way and about 40% of the distance between walls (it sounds better than the recommended 38).

I've read that defusers are less effective than absorption in smaller rooms like mine. Is that true or is a defuser the way to go?
Old 8th June 2009
  #7
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I used the RealTraps Frequency/Distance Calculator to figure out that 1/4 of the wavelength of 600hz is about 22.6" which is exactly the distance from my speakers to the wall! As soon as the rest of the family wakes up I'll probably move my speakers a bit closer and see if that changes the modes.
Of course this doesn't help me with my problems, but I think it's pretty interesting to know (if it's correct that is).
I am also hypothesizing about if 5.7" panels would absorb the right frequencies to fix this, as 5.7" is a quarter of the wavelength. That seems pretty thick though, so maybe some 2.8" pannels? I kind of need some advise from a pro (or someone who knows anything about acoustic treatment) on this.

BTW thanks a bunch to Ethan for all the useful info and apps on RealTraps.com!
Old 8th June 2009
  #8
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Ethan Winer's Avatar
 

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Quote:
Originally Posted by AnthonyHues View Post
From the graph you can see that everything between like 40 hz to around 300 was within around 5dbs.
I'm skeptical, and trying to figure out what might have happened to get a graph like that. It's not reasonable (too good) for a room that size and shape.

Quote:
So what should I do to smooth out the higher frequencies?
Maybe nothing. Once you get above 400 or 500 Hz you'll see peaks and nulls that aren't really present, but are due to time delay differences between the two speakers as they arrive at the mic. Did you measure with both speakers playing in mono? If you have all the reflection points treated on the side walls and ceiling, you can probably ignore those peaks and nulls.

--Ethan
Old 8th June 2009
  #9
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Quote:
Originally Posted by Ethan Winer View Post
Did you measure with both speakers playing in mono? If you have all the reflection points treated on the side walls and ceiling, you can probably ignore those peaks and nulls.
I just did some tests with only one speaker at a time, and they came out almost exactly the same as the first one with the peaks and nulls.

Quote:
Originally Posted by Ethan Winer View Post
I'm skeptical, and trying to figure out what might have happened to get a graph like that. It's not reasonable (too good) for a room that size and shape.
As I said earlier, that's what I though too, until I listened to your test tone CD and everything really sounded almost the same level.

the rear wall and left wall are outside and have insulation in them so that might do something, and I've got a dresser full of clothes in the rear corner as well as the closet full. Also the door on the right may be thin enough that the bass escapes through there not needing to be trapped.


Also I figured out that my thoughts on speaker placement were wrong. I moved the desk and mic out to about 2' 3" from the wall and expected the nulls to move down to 500hz, but they stayed at 600. I guess it was just coincidence that my nulls were at the frequency exactly the distance from my walls to my monitors.
Old 8th June 2009
  #10
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Ethan Winer's Avatar
 

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Quote:
Originally Posted by AnthonyHues View Post
I listened to your test tone CD and everything really sounded almost the same level.
If you get a chance, I'd love to see a plot of the response using my 1 Hz spaced test tones. Though it takes a while to run and note every point on the included graph paper.

If it's still that flat you should consider yourself one very lucky guy!

--Ethan
Old 8th June 2009
  #11
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Alright, I don't have an SPL meter, but I ran the sounds in Sonar and recorded the output.

It's not quite as flat as the other test, but it's still pretty good.

The big dip in the middle starts dipping at about 160hz and ends around 219hz, otherwise it seems pretty good to me.
Old 8th June 2009
  #12
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Sorry forgot again to add the attachment
What to do for acoustics-room-sound.jpg
Old 8th June 2009
  #13
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Ethan Winer's Avatar
 

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Quote:
Originally Posted by AnthonyHues View Post
The big dip in the middle starts dipping at about 160hz and ends around 219hz, otherwise it seems pretty good to me.
Yes, but the REW graph you posted earlier should be exactly the same, unless the microphone was not in the same place. Hey, it might really be that flat! But I'm still skeptical only because I've never seen that in a room the size and shape of yours.

--Ethan
Old 8th June 2009
  #14
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Ran the test again, this time with it back in it's original place (it was still moved out from earlier) This time it was an even stranger graph. It's really almost the same except at 273 hz the sound jumped way up. I was in the room the entire time and heard everything that was recorded here. Every time I heard a change in volume I looked over and saw that the graph was changing accordingly.

My room is starting to be kind of weird .

I don't know what was happening in the other tests, maybe it just went through the frequencies too fast. Still, should I be at all concerned about the nulls at 600hz and such or just focus on the bass for now?
Old 8th June 2009
  #15
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man I need to remember to attatch things!
What to do for acoustics-new-room-graph-thing.jpg
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