How to Measure Good Room Acoustics
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- Опубліковано 19 тра 2022
- In this video, I will show you an easy measurement you can make in your theater room to better understand how good or bad your acoustics are. This method requires you do download the free measurement software (www.roomeqwizard.com/) and a calibrated mic. (I put recommended microphone in the text below.)
RT60, is a metric which describes the length of time taken for a sound to decay by 60 dB from its original level. In REW I show you how to make an accurate RT60 decay measurement and what it means. A specialized version called RT 60 Decay will be discussed and how it better relates to small room acoustics.
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I built a home theater in my basement. After I had all the furniture and speakers in, I did some measurements and RT60 came out to .5 for most frequencies above 200hz. Below it went up to 1s at around 120hz. Room sounded ok for movies, but music was mostly a mess.
I watched Anthony's presentation and followed his recipe (but treating less than the 15% absorption+15% diffusion he recommended). Now the RT60 is relatively flat at around 300ms above 150hz. At 100hz the RT60 is at 500ms. So that worked great; it sounds much better now too, especially music is a world of difference.
The thing I still need to improve is bass consistency and I want a bit more bass absorption, but I need to convince my wife for more budget first. Need to get that 2nd sub. Everything below 100hz is still a bit of a mess.
Thank you so much for all the great resources.
Thank you so much!
I've watched almost all of your videos and the others from your associates, on REW... and this is the first video I've seen clarifying which rt60 option to use, and also what to look for.
Many videos have said rt60 is for larger rooms, but you're the first to explain rt60 decay in contrast.
Thank you so much.
This is exactly the video I’be been searching for. Thank you Gene! Fantastic work!
This video was needed for so long. You're the best Gene !
been waiting for this for months. great video.
I know a lot of the users who are new to the community have been asking for this. Great video Gene! Anytime someone asks me “What’s a good place to start in terms of tweaks?” I always tell them precisely what you said, get a USB mic and REW otherwise you’re flying in the dark. One thing that obviously sets Audioholics apart from other audio sites is that the plethora of information available to us is based on quantifiable data. A rarity these days! I meant to add Gene. With a 7.4.6 setup in an L shaped room I’m at 500ms. I have diffusion, Auralex bass traps in the corners and am going to add just a small bit of absorption to the side walls.
Another excellent video Gene. I need to run this test and see what it does in my open space family room HT. Great stuff as always.
Hey Gene, it’s your Amazon guy here. Thank you for covering this topic. My room was completely over treated. I removed many of my treatments and got RT60 up to.338.
Seriously excellent knowledge right there. Thanks mate, really appreciated this video. Knowing your room first is really at the heart of that great experience we're all looking for.
Thanks for this. I have been using REW for years, but really never knew how to use these features. I now have 2 to 3 rooms to work on.
Thanks Gene for making a nice simple video, this is exactly what I was looking for to get started working on my new room. Nice job on the theater too, that has to sound spectacular.
Fantastic video Gene. I havent done one for a while but this has given me a reminder to get the mic back out.
Great video sir! Going to run this test in my theater room today 👍
Loving these kinds of videos!!!
Thanks for the information & examples! This will be my next task.
Great video, very informative! I appreciate the in-depth view of the RT60 Decay view in REW, and analysis of "over-treated" and :"dead" with too many thin panels that unevenly reduce RT60. I have a big living room, wide to left (dining) and right with listening area in the middle. I have a GIK panel behind the couch, and a few GIK panels behind the speakers and TV. RT60 is about 300-450 or so (peaks at around 500) down to 70Hz. Sounds pretty darn good in my opinion, with Ascend Sierra-LX speakers and Marantz receiver.
This was the best rt60 explanation i've seen (2) total, but still.
Thank you for giving us the ATM! And That Means about RT60. I've read conflicting recommendations. I trust yours!
Superb tutorial, thank you. I have two set ups in treated rooms but never measured so just guessing really. This will put some science behind it and evaluate the treatments true effectiveness and point out any improvement opportunity.
Looking forward to your MultEQ-X vid as I have invested in it and the mic but there are some elements I'm unsure about. So hopefully your experience will provide some answers.
cheers from the UK.
Great video Gene, it is very helpful.
An over treated room ya say, I've yet to meet that monster. All the Gurus say that an Anechoic chamber is probably not what you want. But I can assure you that I want one very very much! Not for a home theater room, but I still really really want one. Cheers Gene 🍻
Wow, never seen anything like this before. Thank you, Gene!
Thanks that was great. I measured my room today! Its quite large with large glass windows on two walls. So its very live. Now the question is how to address the issues!
Thank you I needed this. I will get the REW software and a mic. I need to see what is going on in my room (14’x21’) which is open to the kitchen behind it, before I upgrade my current sub to a REL HT 1508 or the Perlisten D15.
glad 2 here all the acoustic videos and such you're planning for the home theater. I'm very interested in what you did for the at screen. I seem to remember you saying you where switching screens. 🤩
Great video Gene! Very impressive results on the non-theater rooms with no treatment! My living room runs about 700ms with no treatment, office before I closed it in similar to you was also around 700ms, then around 600ms after the wall. Theater is under construction but hoping to achieve good results in there with a proper set of room treatment.
Great content, perfect for me as having designed and built my own cabinets, crossovers etc and measured them individually using REW, I wanted to understand room eq.
So my lounge has zero intended room acoustic panels, just thick carpet, non brick construction, slightly triangular compressed cardboard ceiling and a large soft material sofa. The room isn't huge so around three large sofa lengths yet I achieve a flat 250ms-275ms response bar a lump at 200Hz (note, two cabinet setup for both music and 'theater'). This I suspect to be the patio windows & doors along one side of the room reflecting/ reverberating.
Boom, I have a room to challenge your $100,000 theater using nothing more than essential items for a lounge 😂
Great video Gene … still building my room will post the results …. 🎉
Thank you. I made some absorption panels for my theatre and was wondering how to measure what effect they had. I’m going to try this some night with and without my panels.
The "guest room theater", lol I can't say I can relate 🤣you're a boss Gene! 💯
thank for the data, good having reference
i'am close to your reference room...in 70m3 room untreated, with 4 sub, need damp ~200hz low Q, and fix 80hz mod high Q
RT 0,4 realy flat above 200, thx to the cluttered room
you can conpensate also with some eq if you cant use aborbers etc.based on rt60 graph or on what you hear
I did my RT60 with a balloon, a pin, and the ETC curve on AudioTools on my iPhone. You get several echo returns from various walls and mine everaged out to 400ms each. Very good for my room volume of 7200 cu. ft. Grimani's formula for desired RT60 came out to the same. Waiting for my UMIK-1 microphone to try REW.
very cool
Thank you for this information!! I have a 11' x 19.5' room that has to dub as my home theater and 2 channel HIFI setup. My ears get fatigued when I listen to 2 channel audio and I'm looking into what I can do to treat the room. The ceiling is about 7.5' high and the walls are paneling, which I'm finding to be less than ideal. I was struggling for a place to start with how approach the treatment and this gives me a good idea of what to look for.
I strategically put up more than 10 absorption panels up in my room (15m2 bedroom used for home theater). The RT60 decay shows that decay time is reduced from 600-800ms to 300-500ms for 100Hz and up, which seems pretty good. But then when I check the spectrogram, although above 100Hz is pretty much a straight line, the delay shoots up to 50-100ms when it goes below 100Hz. Is it because of insufficient bass trapping? I also did some movie test and the bass sounds sloppier and less punchy compared to before treatment, although the low frequency response doesn't seem to change much.
I apologize if this is rude to post a question unrelated to the video- i just thought a newer video would help me get more views/answers and this is a very helpful community, so i hope it doesn't upset too many people as that wasn't my intent. Or if someone can even guide me to the proper place for this discussion.
I used an old version of itunes on a very old laptop to play digital music. HDMI hooked up straight from laptop to denon x4500 set to multi channel stereo (I'll glady include other gear in my setup if it would alter anyone's answer). To me, this provided best sound from my available options. I did use the itunes EQ with custom setting that wasn't altered too much from their flat preset.
That laptop died and I'm setting up itunes library again on a new one. It will not recognize my .wav files (this was my preferred format) and downgrades them to an mp4 along with the associated smaller file size when I try to import them. My dinosaur version of itunes imported them fine as far as i could tell.
I did a quick google search and didn't look like answers would be easy to find and I'm honestly anxious to get my digital catalog back.
Any input would be appreciated and I'm open to using a different audio program or player- even if i have to pay for it. I stayed with itunes so long bc i was simply happy with it, some other reasons associated with my old laptop, and time it'd take to move all my files to a new player. Thanks to everyone who took time to read this- even if you don't have any input on my situation.
Gene- i haven't watched this video yet, but it's at the top of my to watch list and I'm sure it's excellent as they always are. I'm even giving it a thumbs up after i post my problem.
Superb video once again. I've re-energized this audio journey over the last 2+ years and learnt a lot from your videos. I like my system and think it sounds pretty good - however fine tuning is where the action is. Just got my Dayton Audio UMM-6 microphone (2 month wait) and working on understanding key aspects of the REW software. Two simple questions for you (or anyone with experience); firstly via my Windows 10 laptop, is it best to pass tone sweeps from laptop soundcard via HDMI out to to HDMI in on AVR or from soundcard via headphone output (using 2.5mm jack split to pair of RCA) to an AUDIO input with RCA's on AVR? Secondly, can the UMM-6 be used as an accurate SPL mic within REW or should i invest in a decent handheld SPL meter (if so....suggestions?) Thank you very much from your northern neighbour.
Finally got around to taking these measurements on my day off! My RT60 Decay is between 200ms and 300ms between 100Hz and 3.5kHz but between 190ms and 230ms past 3.5kHz.
To be fair, my room is tiny (10ft x 12 ft x 8ft), has carpet, a couch, an open coat closet, and three absorption panels. I have a total of eight diffusion panels scattered throughout the room but overall it does sound too dead for music. I think it's a decent for home theater use though which is what it's really designed around.
When you talk or clap in the room, does it seem lively or dead? I would guess it leans toward the dead description as in no reflections. You may like that. I think what Gene is saying is that HE likes it a little more lively in the 300-400ms range. YMMV from Gene's.
@@CobraChamp that roof was definitely dead but it was such a small space that it wasn't too unnatural. Like I said, it was good for movies but not the best for music. I've since moved and my room now is probably too lively but it's a weird vaulted ceiling rental so there's not much I can do.
Great video!
What do you look for under 100hz?
I don't currently have a mic for REW (I will eventually buy one) but I imagine my RT60 Decay time is a good bit lower than in the video. Small 13 x 11 feet room with underlay and carpet. Plus over the carpet two rugs, one is thick Australian sheepskin.
13 acoustic room treatment panels. Though the 4 4inch depth absorbers have front scattering plates. And a couple of 6inch depth hybrid cylindrical diffuser/absorbers. As well as a few normal wooden diffusers.
The diffusers and absorbers with front scattering plates make my small room sound more spacious and immersive. Plus stops it from sounding too dry for both music and movies.
I recommend actually measuring it, the Behringer ECM 8000 ist only like 30 bucks. Sometimes you are so deep in fiddeling with your system, you loose any objectivity and you think "this must sound good, therefore it does".
thanx for sharing, i would like to try this, do you know if the mic that comes with the anthem gear will work ?
Gene - 1st time commenter here. A big thank you for all your content, guest experts, and this insightful video on RT60 Decay time. As a 2channel guy, I'm curious not so much about an average decay time from 20-20Khz but what the decay time is for Bass, Midrange, and High frequencies because then I can do something practical to make it better. An overall average decay time from 20-20KHz tells me nothing specific to "fix." So, with whatever frequency range you consider to be Bass/Mid/Highs, what decay times do you recommend for the three ranges for 2 channel stereo listening?
And for what it's worth, I've been told that certain musical genres also have slightly different decay times with classical music having longer times than say folk and jazz that have typically shorter decay times. Would you agree?
Lastly you mentioned FIR filters I think as part of your big-rig system . . . I've recently invested in Audiolense XO software that measures and creates a convolution FIR filter file that I play within JRiver. It's ability to time align impulse responses from all drivers+speakers for phase alignment and group delay and its ability to get your frequency response to match your desired Target Curve is sonic bliss. Here's to DSP power! If you haven't already done a video on other measurements and/or the convolution process to generate FIR filters, then there's goodness there to be shared . . . just an idea.
Thank You for showing this! I measured the RT60 decay in my home theater room which is underground and the stair to go up has no door! And the decay goes from 700 to 1.5 seconds! I have to treat this room and I already know it because even clapping hands allows to hear that there is huge reverbe. I am only thinking that one of the big problems in the room is the free stair access. I suppose it is a sort of "reverbe amplificator". Do you have any suggerstion about that?
I have my cinema hovering around 400ms and it sounds good with both music and movies.
where did you get those skyline diffusers on the back wall? the brown ones
I heard it's smarter to spend money on a modest speaker + room treatments vs a high-end speaker + no room treatments. You're tests seem to confirm this. I'd love to see a short video on how to DIY build absorbers. 2D, and especially 3D diffusers are probably best left to purchase. I would be awesome if Anthony Grimani could offer a discount code for his diffusers for Audioholics.
Depends I guess, what speakers? What kind of room? Does it already have carpet and sofas? Ceilings seem to be a bit of a problem but people rarely treat those.
General rule it's ; ceilings,floor, back wall, first n 2nd reflections.
Do you think I can use my Anthem Avm70 mic for this ?
So the focus here was decay time. Fortunately Audioholics has a few other vids explaining how to improve decay. The spectogram was interesting but we only got to see a snippet. What should we do Gene if our rooms aren't as phase coherent as yours? What causes some frequencies to be hottest a few ms after the rest? And any chance of some more vids looking at other REW features and what the results mean, spectogram and clarity for examples? 👍
Pffff that’s child’s play, I can get Grimani T-shirts at Walmart, and even pay half off for them at Ross. ;P
I liked this video a bunch, I dig the vibe.
I remember hearing somewhere (maybe from Matt) that psycho acoustically it’s been found that people like a steep initial decay, with a long reverberant tail. Which I think is evolutionary from being in forests.
My only other tidbit to add to the conversation is that receiver room-eq is pre-calibrated for the mic it’s packaged with. So swapping in a “better” mic may actually throw it off. Hopefully that will become a thing of the past with online access to mic profiles, and who knows maybe even cloud processing to the 10,000th octave.
Which brings me to my next tidbit, data speeds, I noticed the loadtime on these files was how should I say… in excess of milliseconds ha ha, I bet if you got a really zippy SSD in there those load times would be snappier.
Congratulations on that sweet spectrogram, my room accoustics these days is a soundbar with wireless surrounds and hanging little softball sized disco balls on a paneled ceiling as a sort of Accoustic atmos. I’ve found shining the surround speakers at the wall and listening to the reflections feels more enveloping that taking them as a direct firing point source, my challenges have been over whether to favor on-axis reflections towards myself, or on-axis reflections into my disco balls. I’ve been thinking allot about acoustics from the standpoint of diffusing on-axis sound and absorbing off-axis sound. With then considerations of creating a sound field by balancing the geometry of how wide the speakers are placed in consideration of how their on axis reverberations would bounce around rooms of various dimension.
Using the geometry of the room’s unique dimensions to determine speaker placement, in tandem with other conventional considerations.
This could have used more of a walkthrough on how to actually take the measurements. What settings do I use in REW? Full range sweep? Am I correct that by default it will only use one of the main speakers plus the sub? Is that what I want?
Great info!! If I have a high delay do I start with absorption panels first? Or diffusers? Thanks!!
Absorption! Just get some rockwool, build some cheap Wood frames and you should be able to Experiment with a budget of around 50 bucks.
0-20hz - 700ms (ish)
20-50hz - 450ms
50-120hz - 250ms
120-20khz - 190ms (ish)
10ft width x 24ft length x 9ft height room
Can you generate RT60 and compare with RT60 Decay? I find no difference b/w the two.
i have an omnidirectional mic (condenser) that isn't the pencil type. it's more of one of a pair of overhead mics.
will it suffice for the measurements? I downloaded REW and have a steinberg audio interface. I don't want to go too far out of pocket to get these kinds of readings.
thanks
how loud you have to put the receiver for good mesurements ? I'm owning denon products , 0 , -10 , -20 ? is there a target db to optain or is as long that there is no compression of any speaker , thanks
My understanding is 40db (AT A MINIMUM) over your noise floor. Use the SPL meter/RTA function in REW to determine your noise floor……obviously turn off your HVAC system, keep the family as quiet as possible, etc.
Just a few questions, Why not do each channel separately? Why would you not use psychoacoustic smoothing?
Looks like 389 MS is my worst time @ 230ish Hz. When I do measure them together the top end dives really fast! Which I think means some phase issues. I have an Anthem MRX740 and even though I have set AARC to flat it's rolling off like the default for Dolby Heights.
I suppose you can use psychoacoustic smoothing but it doesn't really represent what we are hearing. Try measuring each speaker individually to see if HF still drop off like that.
@@Audioholics Will dive in today again. I thought that what the psychacostic was supposed to be more like what we hear. Looks like the help file is where I will be, the ERB looks nice.
how do I measure delay--echo in my listening room???
Awesome vid man!
Would be cool if you got a good mic and did a few tests of how music sounds in each room so we can hear the differences as well.
You’ll get better performance from your acoustic screen if the treatment behind it is black. Light leaks through the holes that the sound is passing through and bounce off the white material reducing contrast.
I have a black scrim layer under the screen so it doesn't matter. Otherwise you're correct.
It appears the noise floor of your room could change your decay times. Is it fair to say you want your measurement volume to be at least 60db over your rooms noise floor?
Yes I think that's a fair point.
RT60 decay is ≈300ms down to 80hz. Then 80-40hz ≈ 500ms. 40-10hz ≈ 1sec.
Below 100hz this is not an accurate measurement.
im happy to see thet im not alone with these 50hz nulls 😂...
Are there no phone apps that are good enough?
Gene, quick question. Are these measurements with both speakers and sub playing at the same time?
Yes
Wish there was more information and learning offered instead of rushing through graphs. Just learning this stuff. Way over my head.
Correction captain! SVS 3000 Micro :)
Yes, weird slip up
Thanks for the abuse from the Opening/Title page 11 to 20 seconds into this video, OUCH!!!
I may watch your video later.
A 10 dB Bass Boots has nothing to do with hifidelity. Sorry!
It absolutely does. It's a gradual rise in level from 20khz to 10hz, aka a room curve.
Flat in-room response is unlistenable. Most speakers exhibit a bass boost when measured in-room.