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initial basement SPL measurements
Old 7th November 2019
  #1
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initial basement SPL measurements

I'm starting to setup my gear in my basement (32' x 30'). This is the first measurement done in REW, It seems I have a big bump at 135Hz and a dip at 95Hz. Is this within a decent range to start - meaning can I possibly turn it into an OK room?

curves have 1/48 smoothing. L - green, R - red monitor. Recorded with Genelec 8040s and behringer ECM8000 / antelope discrete8.
Attached Thumbnails
initial basement SPL measurements-lgreenrred.jpg  
Old 7th November 2019
  #2
Here for the gear
 

I am just getting started as well, but this looks very close to my initial measurement so I wanted to share what I have discovered thus far through weeks of research and testing. I think that this will help you.

My account is new, and I haven't been able to create my own thread, so perhaps this will also help to verify some of my observations.

In my room, the first two axial (front to back) room modes are at 22hz and 38hz. My sub does not produce 22hz, but I have a massive peak at 38hz, much like yours. I am considering this the primary mode in my space. It would be nice to see what is happening below 40hz btw. When using a test tone at 38hz, it is 5-10db louder than the listening position in the front corners, particularly the wall/wall/ceiling corner, extending all the way across the ceiling to the opposite corner. It is also hot on the back wall in the same places, but not as bad (25ft long).

I am not knowledgable enough to know exactly how that buildup is affecting the rest of the frequency response, but my best guess is that by treating all of the areas that are hot at 38hz, a lot of the other low end problems would be also be corrected or at least improved. My plan is to use 24x48" batts of r-30 (9" deep), triple layered to 27", to absorb as much 38hz as possible without resorting to a more exotic solution. I am going to build rectangular columns (soffit style traps) at 24x48x27" and fill the hot areas.

Also in my room, I have a large peak at 76hz, similar to yours. This is also directly related to the corners of the room, and presumably to the primary mode of 38hz, being an octave up. If I use something that absorbs 76hz but not 38hz, that peak goes down.

I also had that same massive peak at 120hz. In my case this is still a little mysterious, but when playing a 120hz tone, the sound was 100% localized at my desk. It was almost inaudible elsewhere, very weird. Getting my speakers on stands, and ISO Acoustic stands, raising them and angling them down helped quite a bit. My hypothesis is that a ceiling cloud could also help with this if that is not an option for you.

As far as your nulls at 60hz and 90hz, I have a similar problem at 50hz. I think that the nulled frequencies have waves that are the right size to cancel at the listening position. So to attempt to treat those, I am going to treat the hot areas when I play a 50hz tone, in an attempt to absorb the reflecting waves before they can cancel the waves from the sub at the listening position. Not surprisingly, the hot areas appear to be in the corners as well.

The rest of your frequency response looks ok to me, better than mine! I think I you follow the standard advice of treating the first reflection points (side walls, ceiling, front and back walls) you ought to be ok. At least that's my best guess. Flattening out the low end is going to be your real challenge, or so I think.

Hope that helps!
Old 4 weeks ago
  #3
You have two dips, not just one. Please post your .mdat.
Old 4 weeks ago
  #4
You have two dips, not just one. Please post your .mdat.
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