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Woodridge Studio Acoustic treatments (REW)
Old 25th January 2017
  #1
Woodridge Studio Acoustic treatments (REW)

Table of Contents
Post 2 - Introduction and Mission
Post 3 - The Room
Post 4 - Undiciplined REW measurements from Aug 2016---all around the room
Post 5 - Improvements for next time we measure.

Great discussion and advice

Post 13- Refined mission and methods
Post 14- 3way position A measurements BEFORE 2017 treatments
Post 15- 3way position B measurements BEFORE 2017 treatments
Post 16- TB3" Position B measurements BEFORE 2017 treatments
Post 17- Adding Bass Traps in the Room
Post 18- Completion of the Bass Trappin and SBIR absorbin and other boundry treatments
Post 19- 3way position A BEFORE and AFTER measurement comparisons
Post 20- TB3" and 3way PositionB BEFORE and AFTER measurement comparisons
Post 21 - Room wall vibration profiles ---accelerometer readings
Post 22 - Not to obsess over that which you can not change.
Post 23 - Room wall vibration and acceleromenter control - Mains Power off
Post 24 - Establishing a new BEFORE bassline and finding the sub polarity is bass ackward.


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Okay Fire Away:

What brought this all about is I built these little checkmix speakers to get things to translate better and now I am back to fixing my room. The last round of acoustic attention here was 10 years ago. I used Liberty Audio Suite to measure the last round but now I have REW 5.1.

Great perspective from these <100$ DIY checkmix speakers.-pentagon-3inch-1-.jpg

I took the measurements using the big speakers and the sub last year. What I am thinking is;

1) what can I fix cheaply in the bass
2) How can i fix the holes ~ 54-63Hz and the other one around 100-120Hz
3) whats with this crazy resonant peak at 150Hz?

Next is what and how can I measure and optimize in the room to assure that what I am hearing from the little nearfield checkmix pentagon speakers s are making my mix translate better. BTW the 6" coax and Tangband 5" speakers are just for alternate perspective and I do not use them so much for mixing, I just use the checkmix and big 3 ways for mixing.

Any advice is greatly appreciated.

By the way it is day two and this thread has nearly 300 views and not a single comment. Please Fire Away Slutz.

Last edited by philsaudio; 27th February 2017 at 09:17 PM.. Reason: Update Table of Contents
Old 25th January 2017
  #2
Background

Hi Gearslutz:

Some quick background about me and my mission.

I have a home project studio and along with a younger friend, we record our music buddies bands for demos and so they have some merch to sell at gigs and online. All the music we record is original and the kind that people play and sing on real instruments live. We try to keep as true to live as we can but we do overdubbing and frankensteining, however these kids can knock the songs out live in a live situation.

I got my first tape recorder over 50 years ago for my tenth birthday. The AIWA TP61R was about the size of two packs of cigarettes. I think I could record one or two songs per side but the power usage was so drastic that the sound was noticeably slower by the time I went back to playback so I would give it a little help with my finger. I had one tape.

Woodridge Studio Acoustic treatments (REW)-iawa-tp-61r-reel-reel.jpg

An uncle of mine was a speaker builder and he introduced me to John Karlson who lived in my town in the NYC suburbs. I am not so sure of the science but his intentions were pure. Here is me in high school with my X15s, my most ambitious woodworking project to date. (cir. 1969) Woodridge Studio Acoustic treatments (REW)-phils-karlson15.jpg

As I got older and secured a job, I purchased a few reel-to-reels, cassettes, 8 track players, digital compact cassettes a Teac 4 track R2R, a Teak portastudio and was a bass player in a few cover bands, soundman for a 7x Grammy winner and then a father who graduated with an EE degree and somewhere along the way I quit playing music. I built an octave RTA for my undergraduate senior project. I was interested in acoustics 40 years ago.

After putting the music playing down for a spell, so I could raise a couple of kids (my 40 YO daughter learned to walk on a tour bus), I got hooked on audio again. It began with building speakers, then progressed into playing bass, then I got in a band and before I knew it my big empty basement took on a life of its own, as my personal project studio. Recording was part of the band scene and soon I had a Fostex VF16 portastudio and figured out how to burn CD's.

Twelve years ago, I finished off my 10" 3 ways and began putting my room together with 200 sqft of 2" OC703 on the walls, unopened, unfaced attic-blanket-bass-traps in the corners and a well diffuseer above the listening position. Then I added an Aura 1808 13cuft sub (tuned as an extended bass shelf reflex cabinet) which satisfied my low end craving for well for over 10 years. As a matter of fact, I did not really touch the room or the speaker system until last year a few months ago. When I was "tuning" my basement I used Liberty Audio Suite to measure waterfalls and RT60's.

Here is some progress pictures from 10 years ago. The 703 panels are flat on the walls with a space between them. I later bridged the spaces with more 2" 707 panels so there were alternating sections of 2" flat on the wall, 4" flat on the wall and 2" 2inches away from the wall. The panels are covered over with layers of cloth. Woodridge Studio Acoustic treatments (REW)-rt-60-baacckleft.jpg

The well diffusers are made from scraps. They mount between the rafters beginning at 8' above the floor and going as high as 8/6 to the subfloor above. A few small areas have 703 in them but mostly the entire ceiling is the bottom of the subfloor above at 8.5' above the concrete floor. I did try putting clouds where the diffusers are but did not like the sound. Here are a couple of pictures of the diffusers. This is how they look from the top.

Woodridge Studio Acoustic treatments (REW)-rt60-difuserrback.jpg

And how they look from below.

Woodridge Studio Acoustic treatments (REW)-rt60-humpback-stocastibaiter.jpg

and from inside

Woodridge Studio Acoustic treatments (REW)-rt-60mousecam.jpg

You can see one of my "bass traps" stuffed in this corner. It is nothing more than a 3#/cuft unfaced R30 attic blankets in an unopened package. I have them placed about the room.

Woodridge Studio Acoustic treatments (REW)-rt60fpback.jpg
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-iawa-tp-61r-reel-reel.jpg   Woodridge Studio Acoustic treatments (REW)-phils-karlson15.jpg   Woodridge Studio Acoustic treatments (REW)-ws-control-room-acoustic-treatments.jpg   Woodridge Studio Acoustic treatments (REW)-ws-control-room-spkr-placement.jpg   Woodridge Studio Acoustic treatments (REW)-ws-floorplan-useage-annotated.jpg  

Woodridge Studio Acoustic treatments (REW)-ws-handrawn-2005-floorplan.jpg   Woodridge Studio Acoustic treatments (REW)-rt60detail-top.jpg   Woodridge Studio Acoustic treatments (REW)-rt60-difuserrback.jpg   Woodridge Studio Acoustic treatments (REW)-rt60fpback.jpg   Woodridge Studio Acoustic treatments (REW)-rt60-humpback-stocastibaiter.jpg  

Woodridge Studio Acoustic treatments (REW)-rt-60mousecam.jpg   Woodridge Studio Acoustic treatments (REW)-rt-60-baacckleft.jpg  
Old 26th January 2017
  #3
About the Room.

I am going to begin with a hand-drawn scale drawing from last decade then I will put some dimensioned computer drawn up diagrams.

Woodridge Studio Acoustic treatments (REW)-ws-handrawn-2005-floorplan.jpg

Woodridge Studio Acoustic treatments (REW)-ws-floorplan-useage-annotated.jpg

Woodridge Studio Acoustic treatments (REW)-ws-dimensions-diagnols.jpg

This is where the acoustical treatments are located.
Woodridge Studio Acoustic treatments (REW)-ws-control-room-acoustic-treatments.jpg

This is how my big monitors and sweet spot are arranged.

Woodridge Studio Acoustic treatments (REW)-ws-control-room-spkr-placement.jpg
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-ws-dimensions-diagnols.jpg  
Old 26th January 2017
  #4
Measurements

Here is the meat and potatoes of this post, the measurements from last August 2016. I wish I could have saved them all into one MDAT for you but I could only get two locations per project to upload so we now have five MDAT projects containing measurements from 9 locations in my control room. Seven of the measurements are made along the centerline. I have ordered my full REW 5.1 project with the locations begining with the mic where someone sitting along the back wall in the couch head would be. Then where the head would be if they rolled the chair into the front of the couch. Then from that front-of-the-couch position ;up near the ceiling and one down near the floor. Next one where maybe someone sleeping on the couch head would be. The last two of the seven would be rolled up to the keyboard and then with the head over the desk that the keyboard tray is attached to. Finally I took two measurements over at the stage left side where singers love to record for some reason.

The measurements were taken with both Left and Right speakers outputting the noise simultaneously.


I entered the data for my control room into Bob Golds room mode calculator using . L=12'11" ; W=35'7"; H=8'10". The height is the bottom of the subfloor for the story above. This is the result.
Woodridge Studio Acoustic treatments (REW)-ws-bob-golds-modes.jpg

BG-1) I notice that I have a long decay at around 30 Hz in both of my waterfalls and Golds shows a warning for 31.8Hz. Aha- theory and practice seem too agree.

BG-2) Golds has a warning for 54 Hz -66 but I do not see a mode in the REW measurements. However the spectrograms show a node here.

BG-3) Golds has a lot of activity around 150Hz and the waterfalls and spectrograms for all of the positions show a huge mode at 142 Hz and this mode persists for all the positions.

Woodridge Studio Acoustic treatments (REW)-ws-spectrogram-ss-sit-back-mix.jpg

S-1) Most notable is the build up of frequencies in the Golds mode calculator around 150Hz. Would you look at that spike in the spectrogram. I don't think I hear this as a wolf note (D below middle C).

S-2) Golds, the spectrogram and the waterfall show a long mode around 29Hz. Total agreement with theory and practice. This should be something I need to address.

S-3) Golds shows some isolated modes from 43 to 47 Hz- The waterfall shows a little bump there past 180ms. The spectrogram has some activity in this area. Agreement.

S-4) Golds shows more isolated frequencies in a group from 54-65Hz. I seem to have a node here.

S-5) I seem to have a hole at 100 hz in a lot of the measurements. Bob gold did not pick this up.

Woodridge Studio Acoustic treatments (REW)-ws-waterfall-sweet-spot-chair-back.jpg
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-ws-bob-golds-modes.jpg   Woodridge Studio Acoustic treatments (REW)-ws-waterfall-sweet-spot-chair-back.jpg   Woodridge Studio Acoustic treatments (REW)-ws-spectrogram-ss-sit-back-mix.jpg  
Attached Files
Old 27th January 2017
  #5
Improvements moving forward.

Things I think I could do better the next time I measure.

Measurement Mic positioning and speaker measurement.

1) Place the Behringer ECM 8000 mic on the centerline between the two speakers facing upward . Measure different positions along this line from the furthest position back against the wall up to the closest position up above the desk, positions I actually assume during actual mixing and tracking. These are the positions my posted measurements above were taken at. I bet I could center the mic better.

2) When the mic is in one of the positions:

Measure the left, right and sub separately.
Measure the left and right checkmix speakers separately.
Measure the L and R bigs together
Measure the L and R bigs with sub together
Measure the L and R checkmix together

Doing this would result in 8 separate measurements per mic position. Yikes.

I am wondering that with all this measuring; what more would that really tell me about the areas in my room that need addressing? Or even more poignent; will I learn more about the three areas I want to address with more measurements? I mean there is only so much one could do in a room, right?

A) I have a bass ringing at 30 Hz everywhere I measured in my room.
B) I have holes at 54-63 Hz and another from 100-120Hz in most of the places in the room, probably due to my ceiling height.
C) I have long resonance at around 150Hz due to room dimensions.

What more can I learn with more measurements? How can I tell if any attempt of mitigation is working? What can I do to work smarter this time around?



PS: I had lunch with a friend who has George Ausperger designed studio at lunch today. We revisited the design of his control room bass trap. It is 4' to 6' high and 4' deep running the length of the 30' back wall. It is made from fluffy fiberglass attic blanket type insulation not particularly compressed. I would consider this extreme but effective and something I can not implement in my home project studio.
Old 27th January 2017
  #6
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JWL.GIK's Avatar
In general there are two things you can do to improve the response of the room: re-arrange things so they are more optimal in terms of sound; and add the right treatments in the right places.

For the first, if possible I would re-arrange the room so the speakers are firing into the longer part of the room. As it is, your rear wall (relative to the listening position/orientation) is quite close to you, which may be responsible for some of the nastier peaks and nulls you measured. See this for details:

Positioning the Listening Spot - GIK Acoustics

Next, you need more bass traps. The 4" 703 and the insulation rolls are probably helping some, but upgrading and adding more traps will make things even better. These will ehlp you:

The Basics of Room Acoustics: Bass Traps, Diffusors, Acoustic Panels
Video Testing for Corner Bass Trap Placement - GIK Acoustics
Old 28th January 2017
  #7
Quote:
Originally Posted by JWL.GIK View Post
In general there are two things you can do to improve the response of the room: re-arrange things so they are more optimal in terms of sound; and add the right treatments in the right places.

For the first, if possible I would re-arrange the room so the speakers are firing into the longer part of the room. As it is, your rear wall (relative to the listening position/orientation) is quite close to you, which may be responsible for some of the nastier peaks and nulls you measured. See this for details:

Positioning the Listening Spot - GIK Acoustics

Next, you need more bass traps. The 4" 703 and the insulation rolls are probably helping some, but upgrading and adding more traps will make things even better. These will ehlp you:
Thanks for responding. I am hoping for some advice interpreting the measurements I posted, advice on how to go about more measuring and interpreting those results and specific methodology evaluating and remeasuring before and after putting more treatments in the room. I appreciate the link to how to place bass traps. I should have thought of this but your video smacked me right in the face. I think I will try listening in all the places with noise playing from the left right and center independently and hear what we got.

I am pretty tied into the room arrangement the way it is. And here are the reasons:
  • I have been in this basement for 20 years and I have positioned the "stereo" in quite a few places. For a spell it was where the live room is now, which was actually two rooms and then I pulled out the dividing wall. It was set up in there with the 38% rule at first but then I moved the listening position along the back wall and that position became the preferred location by myself and all my speaker building audio buddies from the Atlanta Audio Society. This was when my only measuring instruments were my ears the 1/3rd octave analyzer.
  • For a time the room, which is now the CR, was the staging area for experimenting on new designs. At first the speakers were along the short wall firing back toward the workshop as you recommend. There is a huge obstruction in that room. It is the large black box in the pictures. It is a cinder block foundation holding up a huge brick two story fireplace above. It ain't moving. There is really no way to position at 38% in that room or any way near the back wall. None of us liked the sound as much as where it is currently positioned.
  • Also that position works well as far as running wires between the CR and the Live room.
  • Also that position works well with the sub as I can position the 13cuft sub equidistant from the sweet spot and as a bonus it is out of the way.
  • Also that position works well when I have 10 people in the control room.
  • Also that arrangement works well during tracking as I can put one person over toward the open space and another near that block wall and get pretty good isolation with directional mics. Then I can have a band in the live room at the same time with two singers in the CR and 7 people on the couch.
So I am not planning on re-arranging the room any time soon.
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Next. Yes yes yes. I want to add more treatments. I need to make a trip to home depot soon and I am thinking about getting 3 more of those insulation blanket packages and putting them in the corner behind the sub because I have room there and I figure that is the excitement source ??????? Also that is an easy "fix" that just takes a little money.

I have room to stuff a few (2 or 3) more of the blanket packs in the space between the fireplace foundation and the live wall. Do you think that would help with the 30 Hz? It may help with bass bleed. My low frequency bleed is pathetic, There is about 9dB isolation at 63Hz from a speaker in the corner near the drum set.

The traps I show in the picture above are only one blanket pack. How does putting two, floor to ceiling change their efficacy?

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Specifically,
  1. How do I figure out what is causing that 30 Hz mode and where to position the bass traps to mitigate it?
  2. How do I figure out what is causing the 54Hz-63Hz and 100Hz -120Hz suck outs and where to position treatments. I had tried clouds over the mix position, more 703 behind the desk ( in front of the mix position and I thought those positions sucked the life out of the music.
  3. What about that 150Hz resonance. I am not sure I hear anything here and I am not sure it is something to worry about but how would one go about mitigating that?
  4. Are the MDAT files I posted what is expected in this GearSlutz forum?
Old 29th January 2017
  #8
Quote:
Originally Posted by JWL.GIK View Post
In general there are two things you can do to improve the response of the room: re-arrange things so they are more optimal in terms of sound; and add the right treatments in the right places.

For the first, if possible I would re-arrange the room so the speakers are firing into the longer part of the room. As it is, your rear wall (relative to the listening position/orientation) is quite close to you, which may be responsible for some of the nastier peaks and nulls you measured. See this for details:

Positioning the Listening Spot - GIK Acoustics

Next, you need more bass traps. The 4" 703 and the insulation rolls are probably helping some, but upgrading and adding more traps will make things even better. These will ehlp you:

The Basics of Room Acoustics: Bass Traps, Diffusors, Acoustic Panels
Video Testing for Corner Bass Trap Placement - GIK Acoustics
I watched the video on testing for corner bass trap placement. Yes isn't it interesting how when I get a new toy (REW) my brain goes dead regarding what I knew as the only way in the past, playing a 1/3 octave warble tone or pink noise and using my ears to find the nodes and modes. Doh!!!!

I still would love a little insight on the spectrograms and if I am posting the MDAT files properly.
Old 29th January 2017
  #9
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akebrake's Avatar
 

Measurements

Quote:
Originally Posted by philsaudio View Post
... Yes isn't it interesting how when I get a new toy (REW) my brain goes dead regarding what I knew as the only way in the past, playing a 1/3 octave warble tone or pink noise and using my ears to find the nodes and modes. Doh!!!!
Agree! REW is fantastic and comes with a nice pricetag also...

Quote:
I still would love a little insight on the spectrograms and if I am posting the MDAT files properly
Your mdats are fine!
Pic 1 shows your measured position dependent FR. Worse at lower frequencies. Several measurements overlayed/ level adjusted with psycoacoustic smoothing applied.

A listener is quite forgiving when moving around in a room. A measurement mic is not.
We are used to ignore the room to a large extent when listening. (adaption!)

Resolution
REW captures the room Impulse Response in the microphone position only.
Then you can display this measurement in many different ways.
In the Frequency domain, Time domain or a combination of the two, depending on what you like to investigate.

REW defaults are meant for steady state (room mode) investigation of FR and Waterfall & Spectrogram with high 2Hz frequency resolution.
E.g. IR-window= 0.5 s long! (1/2 Hz ) means that Room Modes will show up quite well.
ETC default is an unfiltered (hi time resolution) "specular" reflection plot.

A filtered ETC (pic 3) shows that reflections after around 7 ft are 4 dB stronger than the direct sound...


Spectrogram is like watching a waterfall ”from above” with somewhat increased level information. (dB contours)
That means it’s a bit easier to spot differencies in decay rate (e.g. how fast modes decay). Still a compromize between frequency and time which are the inverse of each other.
Y still have to keep Time or Frequency RESOLUTION in your mind! Which one are you investigating?
Is it a steady state FR (long IR window = fast changes will not show) or is it a Time Response ? (A shorter IR window means: long wavelength will not show)

Personally I like the normalized Wavelet Spectrogram with gradually shorter IR window towards higher frequencies. (pic 2)

Hope that helps


PS Even if you can’t upload gigantic mdat files to GS… (≈10MB restriction)
After downloading Y can save a compilation of several mdats in one display just by drag & drop into a new plot. (like pic 1)
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-phils-diff-pos-test-1.jpg   Woodridge Studio Acoustic treatments (REW)-phils-sweet-sp-wavelet-1-24.jpg   Woodridge Studio Acoustic treatments (REW)-phils-filtered-etc-250-hz.jpg  
Old 30th January 2017
  #10
Quote:
Originally Posted by akebrake View Post
Agree! REW is fantastic and comes with a nice pricetag also...



REW defaults are meant for steady state (room mode) investigation of FR and Waterfall & Spectrogram with high 2Hz frequency resolution.
E.g. IR-window= 0.5 s long! (1/2 Hz ) means that Room Modes will show up quite well.
ETC default is an unfiltered (hi time resolution) "specular" reflection plot.

A filtered ETC (pic 3) shows that reflections after around 7 ft are 4 dB stronger than the direct sound...

1

Thanks Akebrake.

I am wondering a little more about this fact you point out.

I presume that the distance is a function of time after signal launch. Is that correct?

So at that time / distance the peak could be somehow a function of:

the time the signal launched from the speaker took to bounce off the front wall and reflect back to the speaker launch point?

The L and R and Sub speakers are 7 foot from the listening position?

The ceiling to floor are a little more than 7 feet apart?

What can I conclude from this measurement?


Thanks again.
Old 1st February 2017
  #11
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akebrake's Avatar
 

Quote:
Originally Posted by philsaudio View Post
Thanks Akebrake.

I am wondering a little more about this fact you point out.
You're welcome! Before going deeper into analyzis...

I second JWL's comment about reflecting surfaces close to your sweet spot and speakers.

And yes, you need more measurements but with Separate speakers.

I suggest:
1: Move the favorite tracking/ mixing spkr pair close to the front wall.
2. Move the sweet spot closer to these speakers. Like in my REW simulation.
3. Find the smoothest bass response by adjusting spkr /listening pos.
see this thread
https://www.gearslutz.com/board/stud...l#post10141263


4. Add bass trapping! As large and deep as possible on the rear wall and side walls and a cloud.

If that is not an option at all...may be some digital ”Room Correction” or electronic bass trap will help (I have no experience with that)

Good luck!

Ake
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-close-wall-png.jpg  
Old 4th February 2017
  #12
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akebrake's Avatar
 

Path Length Difference

Quote:
Originally Posted by philsaudio View Post
...
the time the signal launched from the speaker took to bounce off the front wall and reflect back to the speaker launch point? .
IMHO its better to take the microphone as our reference.

1. Signal launch from the speaker towards the measuring mic and reflecting surfaces around the room.

2. Wavefront encounters the measuring microphone after a ”Time Of Flight”. (TOF) We usually call this (first) arrival our reference time ”T0” (T-zero)
Note: TOF is often not showed in ETC plots


3. First strong reflection arrives 3.49 ms "late"… (after Direct).
Note: Different example below.

Acousticians often call this: Path Length Difference, ”PLD”
e.g. The difference in arrival time (travel) between a strong Reflection and Direct.

When that path equals ½ wavelength you got the first cancellation in a combfilter.
A SBIR null if you like…

Math: 565/ 3.49 = 162 Hz. Will create a possible dip in that frequency band in combination with modes…

EDIT: Legend:
”565”= speed of sound / 2 ; ”3,49”= PLD in ft. (REW cursor value. Imp units)
Metric: 172 = speed of sound/2 ; ”1,2” = PLD in meter (REW Cursor value)
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-etc-pld-png.jpg  

Last edited by akebrake; 5th February 2017 at 03:39 PM.. Reason: added info
Old 5th February 2017
  #13
Refined Mission and Methods

I have taken measures to assure that the next measurements I make will be more accurate. Why? Because I plan to add some bass trapping and then recheck them.


First step is to limit the number of measurement locations
to a couple of manageable ones. I have determined that what really matters to me is to have reliable accurate sound in the mixing location. The rest of the room is not so important to be accurate as it is just for pleasure listening and at first impression the "stereo" sounds great in the room everywhere.

With this in mind I picked two locations to focus in on:
  • Position A would be sitting back in the rolling chair slid back so the back of the chair is agains the couch.
  • Position B would be sitting at the desk, hands on the keyboard leaning back in the chair.

Next I will only be addressing two of the four speaker systems, limiting to the ones I routinely mix on;
  • the 3way+sub system and
  • the little pentagons with the single full range, crossoverless, 3" Tangband drivers.

I firstly used my Radio Shack SPL meter to find the exact center between the left and right speakers. The center line between the 3 ways and the pentagons is offset by two inches or so due to placement restrictions of the pentagons. I had to use the RS meter over REW because I could not readily see the dip with the Behringer ECM8000 but it was very visible with the RS meter. I put the RS meter on a tripod stand and hung a plum bob (made from an Airsoft AEG motor) on it to mark the exact position of the center null on the concrete floor with a magic marker. (see photos)

I created a test signal (files attached) using Cubase; to find the center null with the RS SLM. It is simply correlated full range pink noise with the left and right channel inverted. I made it by printing the mono noise from the Cubase signal generator on one track, duplicating the track, inverting the polarity on one of them and then mixing them down with each track panned hard to the L and R. The 12dB or more dip is easily visible when the SLM is in the center null. I marked several points on the floor and then drew a line for each of the two speakers. Points A and B were then selected based on chair position. The mic is at 42 inches, my ear height in the chair.

It is interesting that the noise file does not cancel out when listening in headphones. Perhaps this is why I can not tell when I am in the null with my ears.

Also interesting about the Radio Shack and Behringer mics? I can easily find the null with the RS but not the Behringer. The microphone on the RS is way bigger than the Behringer mic. Perhaps I am not patient or precise enough to guide the MIC. The RS meter responds very fast and with no latency.
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-ecm-8000-plum-3050-mic.jpg   Woodridge Studio Acoustic treatments (REW)-aeg-motor-plum-bob-.jpg   Woodridge Studio Acoustic treatments (REW)-rs-slm-plum-bob-attachment..jpg   Woodridge Studio Acoustic treatments (REW)-rs-slm-plum-bob.jpg  
Attached Files

Pink Corololated LandR out of phase-15sec-441-16bit - .wav (2.23 MB, 1942 views)

Pink Corololated LandR out of phase-1 min MP3-320K-.mp3 (2.29 MB, 1632 views)

Old 5th February 2017
  #14
Before Measurements. Position A - 3 WAY -

These are measurements taken Feb 4 2017 before the round of additional treatments.

Position A 42" from floor.
Attached Files
File Type: mdat 3w-left-pos-A.mdat (2.35 MB, 61 views) File Type: mdat 3w-right-pos-A.mdat (2.31 MB, 50 views) File Type: mdat 3w-Aura Sub-pos-A.mdat (517.2 KB, 50 views) File Type: mdat 3w-L+R mono-pos-A.mdat (2.33 MB, 80 views)
Old 5th February 2017
  #15
Before Measurements. Position B - 3 WAY -

Here are the same measurements taken from position B, at the desk position on Feb 4 2017, before the next round of acoustic treatments.

3 way speaker system.
Attached Files
File Type: mdat 3W-RT posB.mdat (3.14 MB, 56 views) File Type: mdat 3W-Aura only PosB.mdat (743.7 KB, 56 views) File Type: mdat 3W-L+Rmono+Aura posB.mdat (3.13 MB, 51 views) File Type: mdat 3W-Lt +RT Mono posB.mdat (3.12 MB, 57 views) File Type: mdat 3W-LT posB.mdat (3.13 MB, 61 views)
Old 5th February 2017
  #16
Tang Band 3" bamboo PENTAGON full range Position B

Measured on the centerline of the Pentagon which is a 1 5/8 inches to the right of the centerline of the 3 ways.
Attached Files
File Type: mdat TB3_-PosC(B)- LT.mdat (3.11 MB, 56 views) File Type: mdat TB3_-PosC(B)- LT+RTm.mdat (3.12 MB, 56 views) File Type: mdat TB3_-PosC(B)- RT.mdat (3.11 MB, 56 views)
Old 5th February 2017
  #17
Adding Bass Traps.

gonna put some hereGreat, I just put six more at the hottest bass build up spots. I put the bags in the little concrete half room because the bass build up from the sub cal tone in REW had mad buildup there. I hear a lot of build up along that back wall where I can perhaps put a bass trap of sorts in the junction of it and the ceiling/floor above. Putting a trap in the wall behind the console not so easy.

Woodridge Studio Acoustic treatments (REW)-ws-handrawn-2005-floorplan-bass-modes-feb-9-2017.jpg



The biggest build up was in this corner. I had one of the insulation bags there and I added 3 more along side of the original one and then one on top straddleing the two walls and the top.
Bags of Insulation Blankets - open or unopen?-photo-feb-06-4-49-38-pm.jpg



I put the other two bags on the wall and in the corner behind the Aura sub. It is that MDF box on the bottom left. These were the two BIG HOT SPOTS when I listened to the REW sub calibration signal. The bags cut down that mode node quite some bit.

Bags of Insulation Blankets - open or unopen?-photo-feb-06-4-49-57-pm.jpg



There is still some bass build up along that back wall. I have this space above the concrete foundation wall in the rafters. The rafters are 2x10 and 10" deep. I am not too concerned with sound leaking up into the rooms above. I am looking at this space as a nice spot for a bass trap of some kind. Not sure what would be the best solution up there but I need more bass trapping if I am going to get rid of the 60 Hz floor to ceiling antinode at ear height.
Bags of Insulation Blankets - open or unopen?-photo-feb-06-4-50-12-pm.jpg

Bags of Insulation Blankets - open or unopen?-photo-feb-06-4-50-38-pm.jpg
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-photo-feb-05-4-54-45-pm.jpg   Woodridge Studio Acoustic treatments (REW)-ws-handrawn-2005-floorplan-bass-modes-feb-9-2017.jpg  
Old 5th February 2017
  #18
Bass Trap Treatment 3-7-2017

11 more of those bags of R15 pink fluffy later. Now I have 16 bags total in the room.
  • I put floor to ceiling "BLOWIN CHUNKS" in the corners where I heard the loudest buildup of the REW sub cal tone.
  • I put a "bass trap" up in the rafters along the ceiling to wall boundary in most all the places where there was buildup. That is mostly the concrete wall to floor above.
Here is the step by step:

I sawed 15" off the folded over end of the bag with a serrated knife. This gave me 5 folded over 30" blankets in the one end and ten individual 30" blankets wrapped like an open ended burrito in the other.

Expand the Burrito..... Because of how big this thing is going to get when I pop open the factory safe-n-sound bag I had to use extra large, clear, garbage bags so I could tie off the top and enclose all the fiberglass. To make life easy I slid the burrito into the garbage bag before slicing it open. It was easy to control the expansion by pointing the knife into the fiberglass and cutting inward. If you are careful, the bag can be controlled to open in a "C" shape which facilitates stuffing it into a corner with an air gap space all the way in the back.Woodridge Studio Acoustic treatments (REW)-expand-bag-.jpg

Stack the Bags......The bags shown here are held in by a shelf but other stacks are almost self supporting if I wedge them floor to ceiling.


Conceal the new bass trap by wrapping it in fabric. I use a black el cheepo sheet from wallmart. It is just stuffed around the bags. Below in this corner are some more unfaced rolls I put in there years ago. I sewed up the fabric nicely so those will remain as is.


The corner volume was unused. It butts up to the left side of a desk and is under a fold up table I screwed an over sized malimine (sp) surface too.
Woodridge Studio Acoustic treatments (REW)-ws-corner-under-desk-arrie-1-track-may-04-2-31-36-pm.jpg


Bind the Boundry I built a bass trap along the top of the concrete wall and below the subfloor above. After a few experiments I found it was pretty easy to make two 15"x 15"x13" (1.5#cuft) fiberglass bags: I put one in the end of the factory bag and the other in clear plastic garbage bags. To hold them tightly in place I stapled some old CAT5 wire using my air nailer and used that to keep them tightly in the corners.


Repeat I kept putting the 1.5#/cuft traps along the ceiling back concrete wall boundry then along the stucco wall to ceiling boundry then along the live room to controll room ceiling boundry. I listened along the way as I kept extending this long bass trap by faith and was surprised that I did not hear any kind of "big " difference in the bass until I got 3/4 of the way around the room then it was like all of a sudden it was clearly and plainly audible. Holy cow was this bass tight.
Woodridge Studio Acoustic treatments (REW)-ws-control-room-after-bass-traps-3-7-2017.jpg

Next as shown in the diagram above I put 7" pink fluffy strips with 2" airgap between the ceiling and the top of the pink fluffy (in bags) where the light rectangles are, and a little more around the ceiling SBIR areas I found with a mirror. ..... I did not stop where the diagram ends, I kept building the bass trap along the ceiling to wall boundary behind the desk and by the big black obstruction and then some.
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-ws-control-room-after-bass-traps-3-7-2017.jpg   Woodridge Studio Acoustic treatments (REW)-cut-bag.jpg   Woodridge Studio Acoustic treatments (REW)-fifteen-cube.jpg   Woodridge Studio Acoustic treatments (REW)-expand-bag-.jpg   Woodridge Studio Acoustic treatments (REW)-stack-bags.jpg  

Woodridge Studio Acoustic treatments (REW)-sheet-bags.jpg   Woodridge Studio Acoustic treatments (REW)-ws-corner-under-desk-arrie-1-track-may-04-2-31-36-pm.jpg   Woodridge Studio Acoustic treatments (REW)-2017-03-03-11.34.56.jpg   Woodridge Studio Acoustic treatments (REW)-2017-03-04-16.47.12.jpg   Woodridge Studio Acoustic treatments (REW)-2017-03-05-13.16.09-1.jpg  

Woodridge Studio Acoustic treatments (REW)-photo-mar-02-5-33-06-pm.jpg   Woodridge Studio Acoustic treatments (REW)-2017-03-04-16.47.46.jpg   Woodridge Studio Acoustic treatments (REW)-photo-mar-02-5-33-49-pm.jpg  
Old 5th February 2017
  #19
3way pos B after
Old 5th February 2017
  #20
pentagon position b after
Old 20th February 2017
  #21
Using Accelerometer to find vibration frequencies on my back wall

I find the room mode section of REW very interesting.

I am interested in resurrecting the accelerometer so I can get a read on what are the primary vibration frequencies on my back wall behind my speakers...ie what frequencies is that wall absorbing. If it works well maybe I will use it to test some panel absorbers I am thinking of building into my rafters.

I had an accelerometer from my speaker building days. It is the Measurement Specialties ACH-01-03.


If you study the data sheet you will noticed they have reality and the new alternate reality ( thanks to Kelly Ann for this new perspective) pinouts. The ones on my drawing below are the correct ones.

This circuit biases up the transistor in the accelerometer. The output is very low and high(er) impedance so it needs to go into an instrument input. I connect the BNC output to an ART ProMPA instrument input and gain it up there then patch that into REW.

I am finding that if I turn up the sound for the channel connected to the accelerometer it sounds like a microphonic microphone. It also is very susceptible to 60Hz power hum pick up. It is surprising how many of my walls have power wiring. I think I am going to have to turn off every beaker in the house when I take measurements if I have any hope of getting that hum out.



I used an old Airsoft AEG battery to power the circuit but a 9v battery should do the trick.

```````````````````````````````````````````````````````````UPDATE````````````````````
I spend the day with my new accerelometer toy using it with my new Rectum-Spanalizer yippie kiyae MF.

The accelerometer itself reacts like a cheap microphonic mic that comes with a $10 Karyoke machine.

The PS unit and interface is humless until I plug the accelerometer in. It could probabily work well as a power line sniffer , check before you drill/cut kind of tool.

I moved it around a bit and kept seeing a few frequecies when nothing is present. This snapshot shows them. Anything that has not died out after 5 seconds is some kind of residule noise from the accelerometer. Not Good.

What you are seeing below is the accelerometer hanging from its cord not attached to anything. It is in the center of the room at least 5' from any power.



The next image is with the accelerometer attached to the drywall interior wall in the back of the house. The other side of this wall is outdoors. There was less hum coming from this spot. In the picture I have the control image superemposed on the measurement. The measurement in a way looks the same as the control. Pretty suspicious.



I have also attached the MDAT files from a few measurements taken with my rig.
Attached Files
File Type: mdat accelerometer Slab- control AC4.mdat (735.2 KB, 49 views) File Type: mdat ACH-01 hanging 3_ control.mdat (735.3 KB, 52 views) File Type: mdat live rm near door LR1.mdat (757.9 KB, 47 views) File Type: mdat live rm near door LR2.mdat (766.9 KB, 46 views) File Type: mdat liverm-wall by porch LR3.mdat (739.3 KB, 59 views) File Type: mdat liverm-wall by porch LR4.mdat (737.1 KB, 48 views)
Old 22nd February 2017
  #22
Not to obsess over that which you can not change.

I am posting this here to remind me not to get too obsessive about things I can not fix. I have exactly these two problem DanDan mentions. A hole a 50-70 because my listening position is halfway between the ceiling to floor and wall to wall in a room antinode and at double that frequency (143hz) I where have a room mode.
Thanks DanDan

Quote:
Originally Posted by DanDan View Post
https://www.gearslutz.com/board/9038508-post24.html

A full blown article on this topic is on my ToDo list. Basically a rigorous test procedure that tries all combinations. All ergonomically locations.
A client did this, including height, spreadsheet and all that. He got a truly excellent result. There was one location including height with a corresponding listening spot, which was vastly superior.
For now I believe that each speaker(s) location has it's own corresponding optimum listening position. I don't think you can really just find or nominate a generic best listener spot. But I haven't really tested that view rigorously.
Does the optimum listener spot shift much with speaker moves?

A couple of other bullet points.
We typically sit at or around half height placing the speaker in the null of the first vertical mode, and in the peak of the second. So for an eight foot ceiling, a hole at 70Hz and a boost at 140Hz.
Also, we typically sit in the middle of the width, so again a null at say 50-60Hz and a boost around 100Hz.
So, a double hole in the response around the Kick drum area and then a big boomy boost above that. Nice.


Placing the speaker sideways or upside down can sometime relocate the woofer an advantage. (Yes upside down, take a look at Mission speakers). But the big point here is the elephant in the room. Thin side reflection traps and a thin cloud will do nothing about this doubled problem.

DD
Boy oh boyo, can't we see the hole at 70 and the peak at 140 in my room measurement here.
Old 23rd February 2017
  #23
Sleuthing the accelerometer noise floor.

Here are some of the points measured above in post 21, but with the power in the entire house turned off, with exception of one short outlet near the breaker panel and a couple of extensions from that panel to my REW5.1 DAW and what was necessary to excite the room and measure response.

I find the new reading for the accelerometer hanging by its cord in the middle of the room with the power turned off promising and confounding at the same time. Note how the 60Hz interference is not present here.

The strong 60 Hz "buzz" is in other power off (NOAC) measurements but not as strong as it was in the previous round of accelerometer readings with the power on.

Woodridge Studio Acoustic treatments (REW)-acceleromenter-control-spectrum-hanging-noac.jpg
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-acceleromenter-control-spectrum-hanging-noac.jpg  
Attached Files
File Type: mdat Control -hang3in pwr off.mdat (832.2 KB, 51 views) File Type: mdat Control concrete spkr.mdat (797.9 KB, 50 views) File Type: mdat Control concrete spkr2.mdat (775.0 KB, 109 views) File Type: mdat Control concrete spkr3.mdat (842.4 KB, 61 views) File Type: mdat LiveRm-bath-eye NOAC.mdat (747.0 KB, 60 views) File Type: mdat LiveRm-bath-knee NOA.mdat (752.7 KB, 48 views) File Type: mdat LvRm-RedBB-NOAC.mdat (737.9 KB, 46 views) File Type: mdat LvRm-RedEye-NOAC.mdat (739.4 KB, 57 views) File Type: mdat LvRm-RedKnee-NOAC.mdat (740.2 KB, 56 views) File Type: mdat LvRm-under skyline-NOA.mdat (736.7 KB, 56 views) File Type: mdat subfloor AC5.mdat (742.1 KB, 50 views)
Old 27th February 2017
  #24
What have I been doing all these years??????????

Revision: I have determined that I swapped polarity when I moved the sub amp to a new location a couple of months ago not ten years ago. Whew! I did notice something awry which is probably when I went on this recent journey but the end result is really been worth it.


I am still getting to know my new rectum-spanalizer - Room Equalization Wizard. Remember; I went through all this room tuning 10 years ago with my old rectum-spanalizer Liberty Audio Suite. I was so happy I left alone for 10 years, with exception of moving the amps around last year when I got a new computer and the Presonus studio live (soundcard/mixer).

My quest is to have consistent REW measurements from day to day place to place. So I have been calibrating and writing test procedures.

To test my measurement prowess I centered the mic, doing left then right individually then averaging them with REW and comparing that to left and right together. Next I added the sub to the mix - averaging the sub with Lt and Rt in REW, but but something was not right. The real measurement was not matching up with the REW averaged plot from the three individual Lt Rt and Sub.

I was thinking maybe this is the sub crossover going to high and was going to start messing with it having marked where all the knobs were homed from 10 years ago. But before I started messing with the knobs I threw the polarity reverse on the sub amp and holy macaroni batman.

Woodridge Studio Acoustic treatments (REW)-pos-3w-lt-rt-sub-out-phase.jpg

I hate to think of myself as such a dolt to not notice this problem but............. I want to think that when I moved the amps around last year I swapped polarity on the speaker wires and it has not been this way that long but ...I am old and am still probing the depths of my stupidity.

Off I go now to find where real problems could exist and be fixed. If this graph is any indicator I know I can much more easily fix a hole at 200-300 than a messed up bass with a hole at 60Hz

I put all the mdats in the file named Position new measurements.mdat The eight individual mdats are also included. These measurements were done after I piled the bass traps in the back room. They are still of sorts the BEFORE measurements.

Stay tuned.
Attached Thumbnails
Woodridge Studio Acoustic treatments (REW)-pos-3w-lt-rt-sub-out-phase.jpg  
Attached Files
File Type: mdat PosA LT 3w only.mdat (753.0 KB, 54 views) File Type: mdat PosA LT_ Rt 3w.mdat (742.8 KB, 91 views) File Type: mdat PosA LTonly avg RTonly.mdat (17.8 KB, 57 views) File Type: mdat PosA Lt-RT-SUB avg.mdat (17.9 KB, 53 views) File Type: mdat PosA LT-RT-sub.mdat (727.8 KB, 58 views) File Type: mdat PosA LT-RT-sub-180sub.mdat (746.6 KB, 43 views) File Type: mdat PosA Rt 3w only.mdat (732.9 KB, 49 views) File Type: mdat PosA sub only.mdat (738.6 KB, 55 views) File Type: mdat Position A new measurements.mdat (4.35 MB, 58 views)

Last edited by philsaudio; 25th March 2017 at 09:48 PM.. Reason: Determined just when I flipped polarity
Old 1st March 2017
  #25
The improvement in musical enjoyment I got by changing the sub polarity far exceeds any expectations I hoped for when I embarked on this decades room tuning revisitation. I am still not sure if I have had the polarity wrong for 10 years or perhaps mucked it up last year when moving amps and stuff around when I upgraded my computer and got the Presonus studio live.


Now I am burdened again with the task of revisiting my music collection and kicking myself to the beat. Oh woe is me.

The sub really shines on records like:
Bela Fleck and the Flecktones.....Flight of the cosmic hippo.
Soul Coughing - El Oso.
Old 30th September 2019
  #26
Gear Head
 

so do u think leaving the insulation unopened and stacking in the corner, is effective at bass trapping?
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