Room frequency measurments

Discussion in 'Listening Spaces' started by patate91, Jun 13, 2017.

  1. patate91

    patate91 Active Member

    Chicoutimi, Qc, Canada
    Still testing!

    I managed to correct the 1000 to 2000 hz dip but it created a huge dip at 70 hz. I put the bass back. By listening the difference between a dip at 70 hz is far more noticable than a 1000 hz dip. Note also that 1000 hz and above are more impacted by sitting position than 70 hz and bass in general.

    1/6 smoothing
    Purple = old
    Grey = new

    sept 1-6 2.jpg


    Sept RT60.jpg

    I still experienced room mode and speakers placements. It is fascinating how some frequencies can almost completly disappear. Everyone should try this with REW and a DAC.

    I found a wall that causes a big reflexion. I need to find a way to treat it. Since it's a wall that can be see when you enter the house I need to find something more appropriated.
  2. patate91

    patate91 Active Member

    Chicoutimi, Qc, Canada
    Today I wanted to see if the flexi rack between my speakers was doing good or bad thing, so I removed it and filled it back, taking measurements between major changes.


    1/6 smoothing
    Purple - before removing everything, so my measurement from the last week
    Gold - without rack - amplifier and dac on the floor
    Green - Everything back

    Sept - Comp rack.jpg

    Here's the details

    1/6 smoothing
    Purple - old
    Gold - no rack
    Light green - Empty rack
    Red - Rack with amp, CD player
    Black - all LP added
    Pink - CD added
    Blue - Everythoing back to normal with TT on top

    Sept comp rack filling.jpg

    Here's the impule response

    Blue - With rack
    Gold - Without rack

    Sept - comp rack impulse.jpg

    There's a reflexion at 1,12ms just a little bit over 20 db (22,1db), I won't sacrifice the frequency response for a small relflexion like this. Maybe I can just move the rack a little bit but, filled It won't move, I'll need help. The spike spike at 13 ms is a rear reflexion, I removed some bean bags and cushions behind the sweet spot, but It can be easily corrected with wall treatment. A simple cotton towel can do it, but I'll try to find something with a high WAF, because it can be seen when we enter the house. Maybe I'll install drap and remove them when not listening to music.

    In conclusion I'll keep the big rack between the speakers. Maybe If I moved the speakers again I would have manage to correct things a little bit, but my setup is tune and I also need a place to store all my CD and LP and keep it convinient.

    I think that the rack, lp, and CD act as a ''baffle extention'', what's your thought about this?

    There's still a small dip at 70 hz I'll try to get some rigid mineral wool panels to see what can be done.
  3. patate91

    patate91 Active Member

    Chicoutimi, Qc, Canada
    Fixing the rear reflexion.

    I installed a curtain rod I put a blanket on it. It's removable so wife will stay happy.

    Impulse - both speakers - before
    You can see the nasty peak/reflexion at 13,8 ms?
    Sept - comp rack impulse.jpg

    Impulse both speakers with blanket on wall
    No more peaks/reflexions
    Note that I placed the microphone differently on that one, the peak is still below 20 db though with the previons setting. I placed the microphone the reproduce if I just sit more comfortably.
    Sept 13 Impulse deux.jpg

    Impulse left speaker - No nasty peaks
    Sept 13 Impulse gauche.jpg

    Impulse right - still looks good
    Sept 13 impulse droit.jpg

    Let's look at the freqency response - again it takes only few inches to modify your measurements and what you hear.

    1/6 smoothing
    Green = Sitting perfectly square
    Pink = Sitting more comfortably a couple of inches below
    Gold = Tried to close the door to the right again - the response looks good now!
    Blue = just for fun - I placed the micro where my head is when I lie down on the couch (and fall asleep)
    sept 13 1-6 smooth.jpg

    Bass - no smoothing
    Sept 13 no smooth.jpg

    So no more reflexions here, I did add convoluted foam matress top (1 inch) at first reflexion points on left and right walls, there were no big reflexions, below 20db, but now it's almost perfect. The next step will be to make this look pretty, but since I don't have money to invest it will wait.

    The next thing that still bother me is the dip between 63,8 hz to 71 hz, - 5 db. I need to think about a solution I know it's coming from the right speaker.
    Last edited: Sep 13, 2017
  4. patate91

    patate91 Active Member

    Chicoutimi, Qc, Canada
    I've done more critical listening and casual listening now and I can say that I can hear a difference when there's changes in the room.

    It always appears like a lack of focus. I have to move constantly to keep instruments locked and singer centered.

    When it happen I found that someone let a door open, forgot to add an absober, etc.

    With everything setup correctly the image is locked on place and small mouvements have less impact.

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