After blocking the ports of my monitors (4.1 mch speakers and sub is now effectively a 'sealed' system), I needed to redo my room EQ & delays -- yet again -- by now
I have lost count.
This is going to be a reasonably "complete" visual documentation so apologies in advance for taking up so much space.
SETUP: main monitors (Sceptre S8 at 2m distance) cross their axes in front of the center main listening position which means one is listening ~ bet. 15-20 degrees off-axis. Surrounds (JBL LSR305 at 1.45m distance) are located at the side and rear corners along the back wall.
First order of business was to re-adjust delays.
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Acoustic timing reference is required to use the alignment tool.
I only needed to cut 2ms from total delay already allocated to the fronts and surrounds. There's no need to change my previous sub and speaker EQ (above 1kHz EQ).
BEFORE AND AFTER CORRECTION PER MONITOR
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I've changed my tactic per recommendations given by others to use 90 deg orientation. Left & Right channels are matched to each other first; and then to an arbitrary target curve thereafter. Due to the room and placement, minor 'fine' adjustments were made to the response above 1kHz for better matching.
I was too lazy to modify the EQ for the surrounds, so I left it alone as it was...
Not quite sure if I'll ultimately keep it, but I previously decided to leave that sharp peak at ~72Hz for the benefit of the summed bass.
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FINAL MMM RESULT
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PER CHANNEL vs SUM
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Notice that summing two channels during MMM boosts the bass by about ~2dB.
LFE + FRONTS / SURROUNDS
(just to check if any suckout develops from phase xo issues)
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LFE 10dB + 5dB from the normal sub bass boost.
It looks like the ideal movie watching volume is around 80-5dB --
better 80dB or below to not over-tax the poor single sub I have running -- which also accounts for headroom required for transient peaks.
DISTORTION MEASURED AT MLP
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SWEPT SINE
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If your phase still looks "off" despite proper positioning and use of acoustic time reference, try applying some smoothing and/or frequency dependent windowing, as well as auto/manual time offset adjustments:
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Many things can inlfuence the measured phase: directivity (narrow/wide) and angling of monitors, reflections and the presence or lack of acoustic treatment, speaker xo & driver arrangment etc.
GROUP DELAY & WAVELET SPECTROGRAPHS
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High frequencies between fronts & surrounds were aligned based on measurements,
as well as further refined by listening and manually adjusting delays until the "surround" upmixed effect sounded "right" to me.
OVERLAYED FOR COMPARISON
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IMPULSE & STEP
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RT60
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DECAY
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WATERFALL
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CLARITY
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*As it is not absolutely needed, I only used simple PEQs in this exercise. No convolution or FIR filters.