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Listening Room Configuration and Treatment

RayDunzl

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#21
Is Iverson an older guy who bought his house before the tech boom? You'd probably have to be a hundred-millionaire or billionaire now to afford that place if it is located, as I suspect from the view, in the hilly area around Silicon Valley.
I suspect this is the house.

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Dialectic

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#22

Thomas savage

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#23
Not creepy at all, Ray! I was just speculating on whether the guy was a tech billionaire, not asking where his house is.
Give ray 24 hours and we can examine the contents of the bins ..
 

Dialectic

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#27

Dialectic

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#28
Good thoughts from @Ron Texas and @Soniclife Whatever you choose, just make sure the setup is symmetrical (use a tape measure and/or laser distance measure down to 1/4" tolerance if you can). The 8c's do very well when placed almost up against whatever front wall you choose. <40cm is good, 30cm even better, as this is what they are designed for :) Unless there is a special requirement for BAACH, I would go with the equilateral triangle.

REW's room simulator is a good one and there are others like: http://www.hunecke.de/en/calculators/loudspeakers.html and https://amcoustics.com/tools/amroc

But there is no substitute for setting up and measuring the room with REW. I presume you have a measurement mic?

Aside from frequency response, REW has a plethora of views to help you better understand your room acoustics:

Waterfall view: will show you modal decay of low frequencies below the rooms transition frequency - ideally all low frequencies should decay at the same rate (but never will :). If you require bass traps, put them in the 4 corners of the room for maximum effectiveness.

Energy Time Curve (ETC): will show you the rooms early reflections for the first 40ms - rule of thumb, the reflections should be ~-15 dB down from the direct sound over that time period.

RT60 - while technically there is no reverb time in small room acoustics, REW has a good algorithm (Topt) for small rooms and this measure is useful above the rooms transition frequency to get an idea of how dead or live the room is. A nice flat response from 300Hz to 10 kHz will yield a neutral sounding room. Typical RT60 Topt ranges for small room acoustics is around 200 to 400ms. Note it is better to have a more lively room than a dead one. Most folks overdo it on the absorption rather than using diffusion. A overly absorbent room takes the life out of the music.

Those 3 basic measurements will help tune your room up. DSP, like in my sig, can shape the frequency response to a spec or taste. It may be you can get away with a few on-board PEQ filters, but like any physical room, below Schroeder is going to have it's ups and downs in frequency response.

I find https://www.atsacoustics.com/ offers quality products at an affordable price.

Once setup and system measured, share the REW .mdat and we can sort you out wrt to passive room treatments.

Good luck!
Thank you very much for this information! I have a cheap Behringer measurement mic, which seems to work fine. (I also have a relative who owns a pair of Earthworks QTC 40s that I may be able to use if he visits.) I will set up the system and share those as soon as we are in the house.
I will not, however, be able to share photos if folks will be able to figure out exactly where we live!
 

Dialectic

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#29
We are in the house now, and I've been able to position the Dutch & Dutch 8Cs on the short wall, adjust the 8Cs' boundary settings accordingly, and take some REW measurements, accessible here. I would be grateful for any ideas about room treatment.

Thank you all!
 

mitchco

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#30
@Dialectic I had a look at your measurements. Was the sweep output low? Do you have an SPL meter by any chance?

Is this a bare room? The frequency response shows room modes at 30, 54 and 90 Hz with some disturbance at 180 Hz and 435 Hz. You could use the onboard 8c PEQ's to tap those down a bit...

The ETC is pretty good in the sense of the reflections are down below -15 dB as compared to the direct sound, but they don't decay over time. Still the same peaky level to 40ms.

The RT60 or Topt shows relatively even decay, except the values are in the 600 to 750 ms range. I would have to do some math, but I suspect that for your size room, it should be roughly be about 1/2 that, like in the 300 to 400m ms range. So broad band absorption would bring down the overall decays time.

The Waterfall graph confirms the room modes down low. While you can use PEQ to bring down the peaks a bit, the long low end resonances are going to be a bit more difficult to deal with. The issue is that bass traps don't work so well below a room's transition frequency, like 100Hz and they are not surgical in nature as they also damp outside there intended usage. However, I have an idea I can share with you on that later.

Can you tell us more about your room or a pic or two?
 

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Dialectic

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#31
@Dialectic I had a look at your measurements. Was the sweep output low? Do you have an SPL meter by any chance?

Is this a bare room? The frequency response shows room modes at 30, 54 and 90 Hz with some disturbance at 180 Hz and 435 Hz. You could use the onboard 8c PEQ's to tap those down a bit...

The ETC is pretty good in the sense of the reflections are down below -15 dB as compared to the direct sound, but they don't decay over time. Still the same peaky level to 40ms.

The RT60 or Topt shows relatively even decay, except the values are in the 600 to 750 ms range. I would have to do some math, but I suspect that for your size room, it should be roughly be about 1/2 that, like in the 300 to 400m ms range. So broad band absorption would bring down the overall decays time.

The Waterfall graph confirms the room modes down low. While you can use PEQ to bring down the peaks a bit, the long low end resonances are going to be a bit more difficult to deal with. The issue is that bass traps don't work so well below a room's transition frequency, like 100Hz and they are not surgical in nature as they also damp outside there intended usage. However, I have an idea I can share with you on that later.

Can you tell us more about your room or a pic or two?
Thank you @mitchco!

At the risk of having @RayDunzl pinpoint my location and post my address for all to see, I'm attaching a photo of the room along with a floorplan (incl. dimensions). It's essentially a bare room right now. The floor has wall-to-wall carpeting and a very thick shag rug over it. The wall material is mostly regular drywall.

Measurements of the speakers were taken with some of that reflective stuff out of the way and with the shag rug pulled up to the front of the speaker stands.

The speakers are, suboptimally, on the wall with the door, which requires them to be positioned relatively close together. Because I'm using BACCH, I don't think that the narrow speaker placement will pose problems in terms of image width, and once the room is treated, this placement may help with sidewall reflections. I will get the white console thing out from between the speakers soon, but for now, it's where my listening computer will go.

I realize the little window to the left may pose problems with reflections.

I can pull the speakers out from the front wall, but I've put them there for now to take advantage of the 8Cs' rear woofers.

The sweep output is pretty loud, but I always get low-ish levels when using my Behringer ECM8000 with RME Babyface Pro as preamp. The mic was positioned around my intended listening position, a bit less than 2m from the loudspeakers. I intend to do most or all of my listening to the 8Cs in the nearfield.

Thank you again!
 

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mitchco

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#32
Awesome! Lots of fun. Sure, you could use a "room treatment" package for sure. If you could swing it, I would put the biggest bass traps within reason in the 4 corners of your room. Then absorb up the walls a bit. I use wide band absorber panels in my room 4' x 2' x 2", (4" would have been better) to reduce the overall wide-band decay time. Not too much as you don't want a dead sounding room. Someone needs to work out the Sabine equation to determine how much...

With that in place, then you can take another measurement and get into some 8c PEQ's below 500 Hz as they will be different with the acoustic package in place. Also we can look at that low frequency decay time (i.e. below 100 Hz) to see if it is still really long or not. If so, then there is a special DSP software plugin product that can assist, if you can use VST plugins.

Wrt sweep output. Understood, if it is loud in the room, but low on the measurement, typically means more mic gain required from the Babyface Pro. May need to look into that...
 

Juhazi

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#33
My room and placement - on the long wall. Listening spot is too close to back wall, but the chair is movable


 
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RayDunzl

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#34
Wrt sweep output. Understood, if it is loud in the room, but low on the measurement, typically means more mic gain required from the Babyface Pro. May need to look into that...
REW could be the culprit too.

"Calibrating the SPL Reading
Valid readings are not displayed until SPL Calibration has been carried out. The SPL reading may be calibrated against an external SPL meter or SPL calibrator by pressing the Calibrate button. The text on the button and the SPL meter digits are red if the meter has not been calibrated. If the soundcard input is altered in the REW soundcard preferences, or if the input levels are altered, it will be necessary to re-calibrate the SPL meter reading."

The above applies when using something other than a UMIK-1.

"Equipment Needed

The first requirement is a way to capture the test signal. There are a few options:
A USB microphone that comes with a calibration file. Such a mic can be used for low frequency or full range measurements. If the cal file also has sensitivity data in a format REW recognises, it can also act as a calibrated SPL meter. The MiniDSP UMIK-1 is recommended and has calibration data in an REW-friendly format, see www.minidsp.com.

An alternative to a USB mic is an SPL meter with a line level analogue output. The Radio Shack meter is perfectly adequate for low frequency room acoustics work, either the analogue or digital display version. The Galaxy CM-140 meter has better tracking of the C-weight curve and better behaviour above subwoofer frequencies than the RS meter, but is more expensive. Calibration files for the various models of the RS meter and the CM-140 can be found in the Downloads area of the Equalization | Calibration forum at www.hometheatershack.com/forums/
RS Analog SPL MeterRS Analog SPL MeterRS Analog SPL Meter

A final option is an analog microphone, but most mics will require a preamplifier to produce line level and to supply the mic with phantom power. An SPL meter is still ideally required to provide a reference SPL figure against which to calibrate REW's SPL display. For full range measurements the mic must be calibrated for accurate results."
 
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Juhazi

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#35
Dialectic, if I was you I would set the speakers on the long wall - now your triangle is very narrow. I prefer equilateral triangle

RT is high, furniture and perhaps room treatment is needed. The room is rectangular with straight walls which is easy for modes! The window on one side wall will give different balance of reflected sound, but not much really. Run test sweep from each speaker individually, it will tell more about symmetry and reflections/modes. Mic height in your measurement looks to be higher than your ear level when seated? Vertical reflections and modes must not be forgotten!

Your response has three mode peaks. That's better than one huge peak! Play pink noise and use REW's RTA (continuous) measurement, take the mic in your hand and move the mic around the room - you can locate mode peaks and nulls this way easily.
 
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RayDunzl

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#36
I'd set up the room more like this:

Speakers on the other wall, seating in the middle.

The door crowds the other end of the room.

Could have a table or desk or whatever on that end,

Window over the gear (if centered) gives something to look at (maybe)

1573631536561.png
 

Bjorn

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#37
Someone needs to work out the Sabine equation to determine how much...
It's well known by small room acoustical experts that reverberation time or a "diffuse field" doesn't exist in a small room. If one is using this as a guide in treatment of this room, the result isn't going to be good.

FIY: Even in large rooms with something close to a isotropic sound field there can be 20% miscalculation when using RTx.
 

Dialectic

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#38
I'd set up the room more like this:

Speakers on the other wall, seating in the middle.

The door crowds the other end of the room.

Could have a table or desk or whatever on that end,

Window over the gear (if centered) gives something to look at (maybe)

View attachment 38684
I can't put the speakers at the other end of the room: by design, the floor is not level, with the water main to the entire house entering at the floor on that side.
 

Dialectic

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#39
Awesome! Lots of fun. Sure, you could use a "room treatment" package for sure. If you could swing it, I would put the biggest bass traps within reason in the 4 corners of your room. Then absorb up the walls a bit. I use wide band absorber panels in my room 4' x 2' x 2", (4" would have been better) to reduce the overall wide-band decay time. Not too much as you don't want a dead sounding room. Someone needs to work out the Sabine equation to determine how much...

With that in place, then you can take another measurement and get into some 8c PEQ's below 500 Hz as they will be different with the acoustic package in place. Also we can look at that low frequency decay time (i.e. below 100 Hz) to see if it is still really long or not. If so, then there is a special DSP software plugin product that can assist, if you can use VST plugins.

Wrt sweep output. Understood, if it is loud in the room, but low on the measurement, typically means more mic gain required from the Babyface Pro. May need to look into that...
Thanks @mitchco, I need to play with the Babyface Pro interface. Part of the issue is that it is auto-configured by BACCH software, and that configuration is complex enough that I don't want to play with it. (I always bypass BACCH processing when measuring.)

I will set some parametric EQ in the 8Cs this weekend and take some more sweeps.

In terms of room treatment packages, what brands are recommended? I'm most familiar with Ethan Winer's RealTraps, which have the advantage (from my perspective) of being available with stands--I'd prefer not to mount treatment to the wall.

Thank you again!
 

March Audio

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#40
2 subs would be an easy way to deal with the low modes.

I agree with Mitch that the RT is high at 700ms, and makes sense from the pictures where the walls are bare and no furniture. Personally I cant stand highly reverberant rooms. Just putting objects and furniture in the room will bring this down as they will diffuse, but you might still may want some treatments. Just be careful no to over absorb. Balance this with diffusion.

Just for info I have used Vicoustic products previously.
 
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