# First measurment



## yveletnik (Dec 7, 2011)

I'm new to this whole measuring and room treating idea, but here it goes, measurements taken with uncalibrated ECM8000 mic, 15x16x8 living room, wood floors, filled with furniture, 1 sofa. I brought all soft items we had in the house, mattresses for direct reflection points, a rug between speakers and listening area, pillows, blankets, coats... 
no sub, both front speakers are on in tests
so the *blue one is treated *and *green is untreated*. First thing, I heard HUGE improvement in sound on my speakers the highs and mids got so much more defined, clean it's unbelievable. Sound became more realistic, imaging improved as well. One thing that got worse is Norah Jones' voice got somewhat less alive, I have a feeling its one of those dip at 220 or 415 Hz.


So here is a few questions regarding the improvements i can do:

1. Highs roll down after 3K Hz on both treated and untreated versions, is it my rooms or speakers or AVR's fault? 
I thought it was mic calibration problem, but i tried measuring with Audyssey mic and it happens in those measurements as well. Another possibility is that the speakers not fully broken in, i got like 20-30 hours on them.
2. dip at 120Hz only happens when I run 2 speakers at the same time, individual measurements don't have that dip, left is even in that area, right speaker has a slight dip at 120Hz, but nothing like on both speakers on. How do I fight that specific dip?
3. Dips at 220 and 415 got worse, how do I treat a room without creating more problems?
4. Using manual equalization in general, in my case to rase the whole region above 3KHZ. My receiver is Marantz SR6005, it has 9 bars on EQ for every speaker and automatic MULTEQ. I talked to audyssey and they sad that copying the Audyssey flat curve into manual curve will not create the same result. They say the manual EQ is a coarse version of Audsseys filter. They refused to say how many adjustment points Audyssey's EQ filter has, they just sad its multi-hundred and it also works in 'time domain'. Kinda hard to believe. Anybody has first hand experience using manual EQ vs Audyssey auto created filter? If what they say is true than using equalization to fix problems is out of question.
5. RT60 looks much better with treatments, i think, is it close to where it should be?

http://www.hometheatershack.com/forums/attachment.php?attachmentid=33995&stc=1&d=1324020337
http://www.hometheatershack.com/forums/attachment.php?attachmentid=33996&stc=1&d=1324020337


Any input appreciated


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## SAC (Dec 3, 2009)

Let's see, I have about 5 minutes for this... (Need it be stated that ALL measurements are made with the mic in exact SAME reference position...)

Much of your perceived problem is a result of your assumptions and methods...

Regarding cancellation with multiple speakers...

Its called superposition. And you WILL get comb filtering and the equivalent of active noise cancellation nulls where the signals at a particular frequency are out of phase 180 degrees as happens when you drive multiple speakers generating the same passband. The physical result is polar lobing, with regions that vary by frequency where sound is canceled, resulting in the null between lobes, and regions where the sound remains. The fact that the mic is located in the null at certain frequencies accounts for the 'comb filtering pattern you observe. Think of it as the 'marvel' of multi-source physics and to a degree, stereo. It is normal.

Do not measure with multiple speakers simultaneously broadcasting the same bandwidth unless you are intent on displaying the behavior as a sort of comb filtering demonstration. In that regards it is working 'as designed'.
Make general measurements with one full range speaker driven at a time.

To the larger issue.

You do NOT resolve superpositional anomalies resulting from the summation of non-minimum phase signals with EQ. You resolve them in the time domain.

Thus, you examine the minimum phase region dominated by modal behavior below about 80 Hz by generating a waterfall response. You will observe the modal behavior for the frequency range of ~0-250 Hz. In this region you would properly employ frequency selective bass traps;and after all is done, then employ limited EQ for the fundamental issues below ~80 Hz of the passband.

Above the modal region (from ~250 Hz up), you generate the full range ETC response and evaluate the indirect specular energy arrivals for each source. From this you are able to determine their vector paths and points of boundary incidence and you can surgically treat the anomalous high gain reflections.

Addressing these indirect signal arrivals that arrive and combine out of phase resolves the notches due to superposition that you observe in the frequency domain. You cannot correct such non-minimum phase anomalies with EQ.

The RT60 calculation is a statistical calculation that assumes a homogeneous behavior that is not in evidence in a small acoustical space. Instead, rely on the applicable waterfall(or alternately displayed spectrogram) for locally distributed modal resonance and on the ETC for locally variable high gain indirect signal arrivals, and treat accordingly.

Note, this is a very quick suggestion regarding a _few_ of the mentioned issues - it is not a comprehensive analysis of your individual situation.


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