Room Acoustic Measurements (REW) Rabbit Hole

Accessories and Tweaks
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How hard is the audiophile life! After speakers and components have been settled there are always cables and tweaks, then AC lines, then room treatments, then upgrades, then… a new journey is coming.

Room measurements, here I am! After having tried a few Apps for iPad I decided to download Room EQ Wizard (REW).

I spent several days studying REW literature and videos

The good thing is that it took me away from this forum for a while LOL!

From theory to practice is the next step. I purchased the MiniDSP UMIK-1 USB microphone and I’m planning to connect the MacBook Pro running REW directly to the MSB DAC via USB to send sweep signals to my speakers.

Before starting this new rabbit hole I’d be very happy to ask all of you, veterans of this forum, a few questions. Your estimated opinions will be very appreciated, as usual.

What I learned during last years is the fundamental role that the room plays in this hobby, much more than other things where we usually spend lot of time and money. So, why not?.

My aim is having a general picture, first and foremost to satisfy my curiosity. Then I will face the issues based on what the measurements will be able to enlighten (and I know that there will be peaks and deeps and reflections for sure). In particular I have to decide if removing or not my 2 subs (by ears I already like what I’m hearing without them).

Which graphs are more useful?
Tips and tricks for newbies?
Settings suggested?
Biggest mistakes to avoid, taking measurements?

Any of you that already experienced this stuff would be so kind to share results and plots? It seems a little embarrassing maybe but it’s not common practice sharing these graphs of room, even more rare than pictures themselves of the rooms.

As always, thank you so much!

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Room measurements software? I am the last person to analyze audio graphs. Have some wine and enjoy the music will be my recommendation.

You’re so deep into the rabbit hole that I can’t even reach you with a 10 meter Dragon cord.:laughing:

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Savvy suggestion, my friend! Have I already told you that I ordered 2 STEALTH power cords that are expected to be here early in March? Need to get busy with something in the meantime!

Kidding aside, don’t underestimate the improvement of sound quality that the room can provide. And at a cheaper cost!

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Luca

I agree with you entirely about the room which is why with the newly constructed room I have gotten all of the primary room treatments in to place first even using the “temporary” equipment on hand in doing so. Once all of the first “final” set of gear is in place then only tweaking should be necessary.

As another Otello owner let me ask you a couple of questions. Is the reason for removing the subs aesthetic or do you really not here a difference. Also what do you have the crossover point set at on the subs. I have mine set at around 40hz and while it doesn’t really do anything with “normal” instruments bass wise turning them off does change the soundstage in my room.

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316-page pdf!

once again, you are the pioneer

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Luca you are about to learn how the room is the speaker and you are part of it.

REW is very comprehensive measurement software and although it is technically freeware I always send the author some money for their efforts. I sent $100 USD but it is really up to you to place a value on the product.

I had a nice set of written instructions for myself on procedures that worked for me but it was lost in my recent move.

If I happen to find it I will post a copy.
The main thing is to have fun while you’re learning about how sound propagation works.

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The help file that comes with REW is also good for procedure.

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I have a lot of experience with Anthem ARC Room Correction software. Place the calibrated microphone in a few different places and run the test tones. The results are usually very good to my ear.

Other friends here run other Room Correction software.

A week or so ago I was happy to learn a new way.

With higher levels of BACCH you get a pair of calibrated microphones that go into each ear. The test tones play and BACCH makes its magic XTC Crosstalk Canceling process.

Now, with those same microphones BACCH ORC Room Correction does Room Correction first, applies the results to the DSP, and then you run it one more time for the XTC filter.

Edgar explains that normal Room Correction software has you put a microphone in multiple places and then it AVERAGES the results. Through this process of averaging it means that no matter where you sit, it isn’t quite right.

With BACCH ORC, you sit in your listening chair, mics in ears, and it does a tremendous job for that listening position. You can do it for as many listening positions as you like. You can also use a camera for tracking the location of your head so if you move, it makes adjustments for your current position.

What this means in my reckoning is that Edgar has found a new and more accurate way to do Room Correction analysis. He still gives you all the graphs to look at and learn from. But the process is largely automated. Plug the mics in your ears and sit still. In a minute or two you are done. Add a new plant to the room? New piece of furniture? Make a new filter…

Long story short, you may be learning how to do something that is already obsolete. It could be interesting and fun though.

While I am listening I can enable and disable the Room Correction function with a mouse click. It makes a really obvious difference. Really Obvious. What surprised me is of course it helps with the bass, but it helps with the highs even more. The high end got a nice kick up.

Tools are given to fine tune these things in case you want to vary the results of the Room Correction. High signals a bit too much or too little, change a setting and run the test signals again. Want to fatten the midrange for when Steve comes to visit? Sure thing.

It’s easy, and it’s fun. What it definitely isn’t, is Average.

Steve.

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What he said ^^^^^^

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Also remember if you are going to measure freq sweeps that the 20khz wave is only 16mm long so if you are going to be able to duplicate measurements from test to test you need to make sure the microphone is within that distance or you will have differences show up on the graphs.

Also any corrections you make should only cut and not boost or you will be disappointed in the results. If you happen to be sitting in a null you cannot fix it with software. You have to move your seat or the speakers.

This is a rabbit hole way bigger than you can even imagine.

Hopefully you are a strong willed man or else you will end up in a pile of clef note shaped goo.

Here’s a really good source but very technical at the same time:

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From what I understand, in addition to aesthetics, a fundamental problem would be the excess cables if SUBs were also used.
Signal, power supply, if you use a High Level, the matter becomes further complicated.
You should have real full-range speakers, but there aren’t many of them around.

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True. :slightly_smiling_face:

The ultimate in automatic measurements.
It would be nice, however, to be able to understand the reason for those possible attenuations.
It would be necessary to analyze the bare room as it is and then intervene with sound absorbers and diffusers.
The best result would be the one obtained when an active correction limits as little as possible following an excellent passive correction.

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Why?

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I have full range speakers. And subs. You can’t do too much to tune the woofers in a passive speaker. You can tune a sub easily. Cables for subs is so not a big deal. Stock cables work fine. Better cables are nice but no big deal.

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To prevent the software from making a correction that is too invasive.
That is exactly what happened with my RP (of the MEN220) in my listening room without absorbers and diffusers.
Now I also do without the active MEN correction.

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Yes, me too, and I think exactly like you.
But it might be possible to create real Full-Range speakers, look at the “old” McIntosh XRT2K which had 6 12" woofers per tower.
They could also be amplified (tri-amplified) with 6 MC2.1KW, therefore 18 Mac modules. (6KW for tower)
Then, using an active correction you can further refine intersections and delays. :blush:

However, if it is of excellent quality, I remain of the opinion that the SUB, if there are no deletions or overlaps, is very useful.

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Following up Al’s question, I would say its the other way around.

In my experience, the most effective use of room/speaker “correction” software has been when I make the effort to address proper speaker placement in relation to my listening position and the physical characteristics of the room, followed by a judicious use of acoustic room treatment at the first and second reflections of the side walls and bass absorption in the front wall corners.

One might argue that the less the software has to do the better job it does.

FWIW.

PS

That said, I agree with you if your point was that measuring your room’s acoustic characteristics to facilitate proper room treatment would be a good first step.

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Fortunately for hoarders like me the more stuff there is in the listening room the better it sounds. Yay!!

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Maybe I expressed myself poorly, but that’s exactly what I meant. :yum:
If we analyze the room and thanks to the reading of its problems we could, subsequently correcting the first reflections, obtain very clear results when the active correction software does its job.
A fairly light job thanks to the initial analysis.

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REW is a very good starting point to know you room, and how it interacts with your speakers. It has eq capabilities, but it is far from SOTA in that matter.

Couple of tips, from one that has been in this rabbit hole for some years:

  • be careful with the sweep levels for measurement. Don’t go over 85dB, to not risk your tweeters. The spl meter in REW is a good tool to use before measurement
  • take the measurements of each channel in separate. Use the timing reference option, so you can time align the measurements for analysis
  • the most important graphics for me are frequency response (use 1/12 smoothing) and spectrogram. The first one will show you the ups and downs of your room’s response, and the later will show you the reverberation time in the frequency spectrum
  • do not be obssessed over the RT60. It means little for small rooms
  • group delay is also an important graphics to show the excess phase and help with designing the eq filters. But I suggest you leave it for the second step.
    Should you need any kind of help, or should you want to discuss any aspects ot measuring with rew, just shoot a message and I will try my best to help.
    Welcome to this new phase of the hobby. For me, it has been the most interesting one.
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