Where to focus on your first REW measurement

[acangialosi]

I hope I got the right form for questions on interpreting REW charts. If not let me know and I'll repost.
We built our first home theater room this winter and I'm starting to learn REW measurements and look at room treatments. I've taken my first round of measurements at the MLP and now I'm trying to understand what's good in the measurements, what's bad, and how to start treating the biggest problems. I would love to hear feedback on how I should proceed.
From the looks of it I think I need to focus my attention on the ~50Hz peak and the ~100Hz, ~300Hz nulls.
1. Are these the right areas to focus on first?
2. Anything else I should pay attention to in these charts?
3. I've been told to focus on <500Hz. Should I share the 500Hz-20KHz?

I think the 50Hz peak is straightforward to tackle using Audyssey MultiEQ app.
The nulls at 100 & 300Hz are going to be more challenging. We have a custom-built cabinet front wall with enclosures for the subwoofers. There is only 2" on either side for adjustment and 2" front to back.
1. Given this constraint, I think I need to focus on adjusting the seating position front to back. Is that correct?
2. Are these nulls severe enough to be audible?
3. Anything else I should try?

Last I've purchased a set of 6 2'x4' 2" spot panels to start room treatments. These are not reflected in the measurements yet. I'll share post treatment measurements once the panels are up.
1. Are there any problems that would obviously be dealt with using room treatments?

I appreciate your advice and expertise!

Mic Position	Left Speaker	Right Speaker
MLP Center
MLP Left
MLP Right

 

[FargateOne]

I am far from an expert but I can safely say this:

very narrow dips or hollows are not subject to investigation because inaudible

instead of only taking one measurement , I prefer this method https://mehlau.net/audio/room-correction-peq/index.html or read :http://www.ohl.to/audio/downloads/MMM-moving-mic-measurement.pdf it is closer to the reality of our hearing, and the graph is less discouraging!

of course the area you choose is the first to check but we don't know if your mlp measurements are for the speakers response at full range or with the subs and crossover (it looks like a sub+main response to me, if I am right it seems not so bad already for me!)

 

[thothsong]

very narrow dips or hollows are not subject to investigation because inaudible

Even if it coincides with a commonly used bass/rhythm/drum note in music?

 

[sm52]

acangialosi, I see a big problem in the 250-500 Hz range. It comes from reflections. At 100 Hz, the same thing, but there is a narrow range. To solve the problem of reflections, you need to move the listening position or speakers. Absorbing panels are of little help. At 16Hz +10dB. This is not good either. But it is not clear where this hump came from. You have not calibrated the sound card. You haven't used timing, either acoustic or loopback. Your microphone is inverting the signal. Most likely. To see the correct phase response, after the measurement, you can press the 'invert' button.

 

[ddude003]

It might be a good idea to tell us the dimensions of the room and what if anything is in it... And what about those speakers? Are they all built into a wall and/or a "custom-built cabinet front wall"... Can you tell us more about that too? Maybe a photo or two would help...

 

[acangialosi]

It might be a good idea to tell us the dimensions of the room and what if anything is in it... And what about those speakers? Are they all built into a wall and/or a "custom-built cabinet front wall"... Can you tell us more about that too? Maybe a photo or two would help...

Yes, absolutely. Here is a schematic of the room and some pictures. The overall room is ~7'x25'x10'. It is 7' tall wtih 6" coffers. It is ~25' long and 10' (at the front). The room gets 6" wider from the popcorn machine.

The LCR, side, rear, & height speakers are all built into the wall / ceiling in dedicated box to the target volume for the speaker specs. The SVS subs obviously have their own cabinets but sit inside a dedicated cabinet box in the lower built-in cabinet at the front wall.

The new GIK 2" spot panels in the pictures were not in the room at the time of the original measurements but will be up on the wall shortly and will remeasure.

 

[acangialosi]

acangialosi, I see a big problem in the 250-500 Hz range. It comes from reflections. At 100 Hz, the same thing, but there is a narrow range. To solve the problem of reflections, you need to move the listening position or speakers. Absorbing panels are of little help. At 16Hz +10dB. This is not good either. But it is not clear where this hump came from. You have not calibrated the sound card. You haven't used timing, either acoustic or loopback. Your microphone is inverting the signal. Most likely. To see the correct phase response, after the measurement, you can press the 'invert' button.

Thanks for the additional input and thanks for looking into the data file. I thought everything under 20Hz was inaudible, so I was ignoring the bump at 16Hz. Should I be looking at EQing that bump too?

Speakers are all built in so I will try moving the MLP forward and back 12-18" to see how that affects the 250-500Hz range.

The GIK test results for the 2" spot panels show a >1 absorption coefficient from ~375Hz and up.
gikacoustics.com/wp-content/uploads/2014/07/salford-Spot-Panel-absorption-coefficient.jpg

Should I not expect some reduced reflection based on this data for that part of the range?

 

[sam_adams]

Thanks for the additional input and thanks for looking into the data file. I thought everything under 20Hz was inaudible, so I was ignoring the bump at 16Hz. Should I be looking at EQing that bump too?

Speakers are all built in so I will try moving the MLP forward and back 12-18" to see how that affects the 250-500Hz range.

The GIK test results for the 2" spot panels show a >1 absorption coefficient from ~375Hz and up.
gikacoustics.com/wp-content/uploads/2014/07/salford-Spot-Panel-absorption-coefficient.jpg

Should I not expect some reduced reflection based on this data for that part of the range?

The first thing that you need to do is to reposition the mic.

The red arrows in the above pic indicate where you should position the UMIK-1 and where the tip of the microphone should be pointing. There is no need to calibrate the soundcard as that calibration is ignored when using the UMIK-1. If you have a 90 degree calibration file for the UMIK-1, that is the one you should load for the measurements. Take measurements for individual speakers, Left, Center, and Right, from each position using the center channel as the timing reference. Post your .mdat when done.

 

[acangialosi]

Thanks for the info Sam_Adams. The mic had gotten moved and was not in the location shown in the pictures. The readings above titled "MLP Center" were located in the location of your center arrow with the mic facing up and a 90deg calibration file. The readings marked "MLP Left" & "MLP Right" were taking ~12" left and right of the center arrow in your picture. I took readings for the left and right speakers.
Per your suggestion though I retook the readings and included the center channel and attached the latest mdat file.
Thanks again!

 

[sm52]

the bump at 16Hz. Should I be looking at EQing that bump too?

Yes.

Should I not expect some reduced reflection based on this data for that part of the range?

Try it. To affect the range below 375 Hz, two panels can be stacked together.

 

[ddude003]

@acangialosi the MLP is sitting in approximately the half way point in the room... You might try measurements forward a few feet or back a few feet... Also, I am wondering if and where your crossover between the mains and subs is? You might try setting L&R and maybe even C as large speakers and the crossover below 80Hz and set the subs around 80Hz also... Progressively (80Hz, 75Hz, 70Hz, 65Hz, 60Hz, 55Hz, 50Hz) lower the crossover point and rematch the subs to the mains to see if you can smooth things out a bit... I also agree with @sm52 in that you need 4 inches or _more_ to affect below ~375Hz...
I also recommend the Master Handbook of Acoustics by F. Alton Everest & Ken C. Pohlmann... You should be able to find a pdf file on the internet... There is a nice treatment on the various types of acoustic absorbers...