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post #1 of 73 Old 07-24-2015, 02:46 PM - Thread Starter
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Pro Designed Room - Measurements Before/During/After Treatments

I'll try to skip the rambling and get straight to the details. I have a dedicated HT that is nearing completion. Here's a link to my build thread in case you're interested. I contracted both Erskine Group (originally) and Nyal Mellor of Acoustic Frontiers (final design) to do the acoustic treatment plan, and I have already purchased the treatments spec'ed by Nyal, but have not installed them yet.

I would like to get a comprehensive set of before, during, and after measurements of my room as I go from untreated to fully treated. This seems like an area where there is very little information available on the boards (at least I haven't see it if it does exist). My treatment plan includes both DIY absorption and engineered panels for diffusion, so this should be more useful in understanding the benefits (if any) of engineered treatments as opposed to just narrow/broadband absorption.

The problem: I have no experience measuring and tweaking an acoustic space. If I'm going to invest the time to measure this in pieces rather than just install all my treatments and go from there, I'd like to make sure I do it so that the community gets the most value from it. To do that, i will need some guidance from those of you more experienced in order to make sure I'm measuring things correctly as well as to develop a strategy for adding the treatments in the correct order.

Finally, I expect this to move rather slowly. My HT is my hobby, and there are a lot of other things in my life that take priority. So I only have so much time I can put into it each day. Fortunately, the hardest part is done. That is, I have the room, I have (most) of the equipment, and I already have ALL of my treatments available. So it really comes down to finding time to actually install a portion of the treatments followed by measuring the results.

Here's how I'd like to lay out the opening posts.

Post 1 - Introduction (you've made it through that part already)
Post 2 - Layout of my room and my acoustic plan
Post 3 - Testing strategy (I need a lot of help with this!)
Post 4 - Results (how did each set of treatments impact the space?)
Post 5 - Conclusions (what did we learn? Anything we can improve on? Was it worth it?)
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post #2 of 73 Old 07-24-2015, 02:46 PM - Thread Starter
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Here is a layout of the room in question.



It's a big room as far as home theaters go, but modest from a budget standpoint. Equipment list is as follows:

LCR - DIYSG Fusion 15s (V2)
Surrounds - DIYSG Volt 8s (NOTE: I'm using a side array, meaning two rows of side surrounds in addition to the surround backs)
Subs - Two (2) lilWreckers
AVR - Currently a Marantz SR5008
Surround Amps - Two (2) Sherbourn PT 3-750 amps
Sub Amps - iNuke 6000
PJ - Sony VPL-HW40ES
A-Lens - Panamporph UH-480
Screen - 160" Wide 2.37:1 Seymour AV Curved
DSP - miniDSP (still deciding which flavor to go with here)


Here's the part I'm sure any of you reading are interested in. Below is my acoustic plan provided by Nyal at Acoustic Frontiers. Here's a free plug for Nyal - He was great to work with. He answered countless questions about this and provided a plan tailored specifically to my needs. Since I was on a VERY tight budget, a lot of what he provided is just conceptual information, and he left the construction details up to me. That way I didn't have to pay him to do the CAD work on something I can build pretty easily (e.g. the baffle wall).




Nyal typically provides more detailed baffle wall drawings but was willing to give me just the details of what needs to go where in order to keep costs down. Again, I know how to build this sort of stuff, I just needed someone with the acoustic knowledge to tell me where it should go. Nyal's flexibility with this really helped me stretch my dollar!





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Pro Designed Room - Measurements Before/During/After Treatments.

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post #3 of 73 Old 07-24-2015, 02:47 PM - Thread Starter
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I would like to use this post to lay out a testing strategy. I'm envisioning an outline that points out the major steps along the way. Something like:
  1. In-room speaker measurements
    Sub
    LCR
    Surrounds
  2. Bare room measurements
  3. Sub Optimization
  4. LCR Toe Optimization
  5. Absorption/bass trapping
  6. Ceiling diffusion
  7. Front row side wall slat diffusors
  8. Engineered side wall diffusors
  9. Baffle wall

The list above is just a placeholder for now, but I would really like to get this ironed out before I move ahead.

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post #4 of 73 Old 07-24-2015, 02:47 PM - Thread Starter
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the first measurements are in this post. Hoping for feedback on how to tweak the process to make it consistent for each set of measurements.

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post #5 of 73 Old 07-24-2015, 02:47 PM - Thread Starter
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post #6 of 73 Old 07-24-2015, 02:48 PM - Thread Starter
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For those of you interested, this is the current state of the room. Again, it's functional, but I have no acoustic treatments in place other than the carpet and a small pile of cotton batt insulation in the back corner.



I did my first REW sweep last week. When I say first, I mean this is the first time I've ever used the software to do a sweep. To start things off, I decided to do a quick LF sweep to see how the subs looked. I'm not sure if the axis scaling is typical, or if there is a preferred way to present the data. I'm still working my way through the REW tutorial. That said, there's a pretty clear dip in the response, that I suspect is due to both axial modes (around 5 Hz) and some tangential modes (around 48 Hz). I may be able to smooth out the tangential modes by flipping one of the subs, but I'm still not sure how to deal with the axial mode. I don't want to add the Helmholtz trap until the end, and I think it's a stretch to get enough porous absorption in the room to deal with a dip at frequencies that low. I've got about 2' of space in the back corner that I could use for trapping, but I'm still not sure it would be enough.


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post #7 of 73 Old 07-25-2015, 12:40 PM
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RT60, STI and %ALcons are 3 measurements used to determine the success of room treatments.
REW doesn't do STI and %ALcons

http://www.mcsquared.com/alcons.htm




The 3d waterfall plot and FR chart are useful as well.

I think you will notice that most of the improvements will be to frequencies that are above 1khz.
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post #8 of 73 Old 07-25-2015, 12:44 PM
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I would recommend against applying absorption to the backwall, you mostly want diffusion back there, as the sound is already at its weakest point back there and absorbing it will kill those sounds dead.

You want to concentrate the absorption to the area between you and the speakers, not nearly so much behind the speaker or behind you; as that is where the reflective sounds are at their strongest.

There is a value called critical-distance, this is the distance where the direct sound will still be able to "over-power" the reflections/echoes/distortion. Where this distance stops is where those reflective angles need to be absorbed or diffused more than the prior.

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post #9 of 73 Old 07-25-2015, 12:51 PM
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Parallel surfaces will reinforce echoes the worst, however you don't need to treat both sides of both walls, you only need to treat one of the two. That is a trick that can be used to save you money and increase effective-treating area while not making the room totally dead or throwing extra panels where they aren't really needed.
I'd recommend it even if you could afford to put it on both sides or if you OCD is commanding you to.

A clap-test is a simple way to see if there are any severe echoey parallel wall surfaces that need more attention.
You want the clap to sound like a clap, not sound like the wall is clapping back at you, but not sounding totally dead either. The porridge temperature needs to be just-right

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post #10 of 73 Old 07-25-2015, 07:14 PM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
RT60, STI and %ALcons are 3 measurements used to determine the success of room treatments.
REW doesn't do STI and %ALcons

........ snip ......



The 3d waterfall plot and FR chart are useful as well.

I think you will notice that most of the improvements will be to frequencies that are above 1khz.
Interesting, I'll have to look more into this. This is the first time I've run across %ALcons in my reading.


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Originally Posted by BassThatHz View Post
I would recommend against applying absorption to the backwall, you mostly want diffusion back there, as the sound is already at its weakest point back there and absorbing it will kill those sounds dead.

You want to concentrate the absorption to the area between you and the speakers, not nearly so much behind the speaker or behind you; as that is where the reflective sounds are at their strongest.

There is a value called critical-distance, this is the distance where the direct sound will still be able to "over-power" the reflections/echoes/distortion. Where this distance stops is where those reflective angles need to be absorbed or diffused more than the prior.
I essentially have two professional designs that both recommended absorption on the back wall with a small amount of diffusion. I've seen recommendations for diffusion on the back walls as you mentioned, and the only thing I can think of is the back row (the bar seating) is too close to the back wall to allow the sound field to reintegrate (not sure that is the right term) with any sort of aggressive diffusion back there.

Similarly with the absorption/diffusion on the side walls. Both of my layouts recommended a combination of absorption and diffusion/diffraction on the side walls.

This is part of the reason I contracted to have the room designed for me, from an acoustic standpoint at least. I've been reading about this and planning this room since c. 2008, and there are so many variables and interactions to consider that I finally decided it was worth it to pay someone to sort it out.

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Originally Posted by BassThatHz View Post
Parallel surfaces will reinforce echoes the worst, however you don't need to treat both sides of both walls, you only need to treat one of the two. That is a trick that can be used to save you money and increase effective-treating area while not making the room totally dead or throwing extra panels where they aren't really needed.
I'd recommend it even if you could afford to put it on both sides or if you OCD is commanding you to.

A clap-test is a simple way to see if there are any severe echoey parallel wall surfaces that need more attention.
You want the clap to sound like a clap, not sound like the wall is clapping back at you, but not sounding totally dead either. The porridge temperature needs to be just-right
I'm not sure if this is what you're getting at, but there are flutter echo treatments in the room (dark green on the side elevation). Between those, the diffusors, and the absorption, there are few parallel surfaces that are untreated above the wainscoting. I suppose the floor and ceiling would be the worst offenders, but the carpet will help with that.

Thanks for the feedback! Any thoughts on the order that treatments should be installed to get the most benefit out of measuring in phases, or is this a pointless endeavor?

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post #11 of 73 Old 07-26-2015, 06:51 PM
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Mixing is fine.
Most of the benefits will be in treating the sides and ceiling. I'd start there.

This is highly speaker dependent. Measure your speakers outside or nearfield to get an idea what the response looks like without the room influencing it at all.
Then put it in an untreated room and measure how bad it gets.

That will give you your best and worst graphs. A treated room will be somewhere in between those two extremes.
The difference in the smoothness of the frequency response and decay rate/RT60 should be fairly obvious.

What isn't so intuitive is how adjusting the quantity and placement of those panels will make you like the sound more.

That said, any amount of treatments, of any kind, is bound to make a positive effect (stopping short of a totally-dead room...) It is reasonably-hard to get much worse than an untreated room.
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post #12 of 73 Old 07-27-2015, 10:47 AM
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From time to time I see dire warnings about making a room "totally dead."

I would be interested to see if anyone has actually, measurably achieved this, or how close they might have approached it.

Maybe this is best left for another thread.
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post #13 of 73 Old 07-27-2015, 11:28 AM
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Quote:
Originally Posted by J_P_A View Post
I would like to use this post to lay out a testing strategy. I'm envisioning an outline that points out the major steps along the way. Something like:
  1. In-room speaker measurements
    Sub
    LCR
    Surrounds
  2. Bare room measurements
  3. Sub Optimization
  4. LCR Toe Optimization
  5. Absorption/bass trapping
  6. Ceiling diffusion
  7. Front row side wall slat diffusors
  8. Engineered side wall diffusors
  9. Baffle wall
The list above is just a placeholder for now, but I would really like to get this ironed out before I move ahead.
You are forgetting measuring with/without seats and other furniture somewhere in that list.
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post #14 of 73 Old 07-27-2015, 11:51 AM - Thread Starter
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Quote:
Originally Posted by PrimeTime View Post
From time to time I see dire warnings about making a room "totally dead."

I would be interested to see if anyone has actually, measurably achieved this, or how close they might have approached it.

Maybe this is best left for another thread.
Interesting you bring this up. From my conversations with Nyal, he expects this room to be slightly over damped due to its geometry.

Quote:
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You are forgetting measuring with/without seats and other furniture somewhere in that list.
Good point. This might be difficult for me to do. Generally it's tough for me to get help moving stuff around in the house. I'll have to see what I can do about this. I think it would certainly be a good point of reference.

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post #15 of 73 Old 07-27-2015, 01:21 PM
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Quote:
Originally Posted by PrimeTime View Post
From time to time I see dire warnings about making a room "totally dead."
I would be interested to see if anyone has actually, measurably achieved this, or how close they might have approached it.
My room has 40% coverage with 4inch thick of absorption and I love the sound. How much more I'd be able to stuff in there is unknown, but I'm probably approaching that point.
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post #16 of 73 Old 07-27-2015, 01:40 PM
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I still dont understand the whole fuss about flat frequency responses? to me flat is dead.

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post #17 of 73 Old 07-27-2015, 02:03 PM
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I still dont understand the whole fuss about flat frequency responses? to me flat is dead.
Many times, when people say flat, what they really mean is smooth.

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post #18 of 73 Old 07-27-2015, 02:59 PM
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One of the recent, supposedly exhaustive worldwide Harman surveys, after digestion and statistical gymnastics, concluded that many people like to turn the TREBLE control from straight up to eleven o'clock, and the BASS control up to two o'clock.

Which led their apostles to proclaim, breathlessly, that "Flat is dead."

(....yawn....)
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post #19 of 73 Old 07-27-2015, 03:34 PM
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I spent thousands of dollars calibrating the car stereo world with expensive calibrative tools like audiocontrol analyzers and eq's and soundproofing and you name it. pink noise this and frequency thats...I wasnt impressed with flat is all im saying. but maybe i am confused with all this. I just use my ears now. moving my speakers a 1/2 in one way or another I can hear what it does to the imaging and spl. all I am saying is that once you get your equipment setup, you should be able to dial in what sounds better than before with your remote control. we are in an advanced world where sitting in the sweetspot with your remote is all you need for great sound. unless of course all you care about is what a computer tells you to do/robot...

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post #20 of 73 Old 07-27-2015, 06:05 PM
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Human ears work differently than measurement mics do.
What is flat to the mic is unflat to the ear.

The ear is insensitive to bass and hyper-sensitive to 4khz; so sensitive that you can supposedly hear -5db @ 4khz, but it takes 65db to hear 25hz.


On a linear scale your ears are 20,000 times more sensitive to 4khz than 100hz.
20db is a 100 fold increase in power/wattage.

So 1watt of 1khz sounds as loud as 1-10kW at 90hz.

Your ear is flattest at 97db (it changes with SPL.)
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post #21 of 73 Old 07-27-2015, 06:28 PM
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Which is why Audyssey's Dynamic EQ is so nice. It works to adjust the EQ over frequency to create a constant perceived volume depending on where you set the master volume.
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"Dynamic EQ"?

Used to be called Loudness. In the better units it was a filter connected to a tap on the Volume potentiometer. (That's before potentiometers were replaced with buttons.) Elegant, and effective.

The 3.5-kHz peak sensitivity is not that significant as it is baked into most performance, recording and playback SPL levels. To the extent that it is, IMO it is largely responsible for the recent trend of HF de-emphasis.

The "official" recognition of bass boosting hearkens back to an Eighties drawing in Audio Magazine: Two guys sitting at Fifth Row Center at the symphony; one says to the other, "Not enough bass."

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Quote:
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"Dynamic EQ"?

Used to be called Loudness. In the better units it was a filter connected to a tap on the Volume potentiometer. (That's before potentiometers were replaced with buttons.) Elegant, and effective.
Audyssey's Dynamic EQ is vastly more sophisticated than the "loudness" control found on equipment of years ago. It works very well for people not listening at reference.
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post #24 of 73 Old 07-28-2015, 01:25 PM
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^^ Doubtful.

Tapped potentiometers (expensive, noisy when aging) ceased to be used possibly before you were born. The most elaborate Loudness circuits (Fisher) featured an additional concentric multiswitch to align for system sensitivity and what is now called "House Curves."

The old tube car radios used a dial cord to tune stations. Simple, tactile feedback that the driver could perform without looking to see exactly which Mode it was in. Superior to the Up/Down tuning that replaced it with membrane switches, a million logic transistors and code. For cost reasons, natch.

Do not conflate complexity with sophistication.
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post #25 of 73 Old 01-10-2016, 03:15 PM - Thread Starter
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I know it's been a while, but this is still something I'm planning to do. I'm about halfway done with my fabric panels, then I'll be able to start with measurements.

One thing I've been thinking about is how to deal with calibration in a way that would offer a fair comparison before/after treatments. My receiver has Audyssey, but the results are not good. For now I've been running it with just level and distances set, and like that better than what Audyssey does.

I'm not confident in my ability to calibrate the system well, and don't want to pay someone to do it every time I add another treatment. With that in mind, I'm seriously considering one of the miniDSP 88A units with Dirac Live. I'm not sure how good the cal would be compared to a pro cal, or even me doing a calibration with my limited knowledge. I'd like to hear feedback on this if anyone has it.

The advantage of using Dirac to do the EQ is it would eliminate calibration as a variable. At least to the extent possible. Any thoughts? I'm excited about getting to the point where I can do some measurements and start tweaking things!

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Turn the EQ stuff off. It will interfere with the acoustical measurements of the room/treatments/system.

Luckily deactivating EQ is easy, it can be done at any time, as can reactivating it.
What isn't so easy is forgetting to take initial measurements of your untreated room as a base-line, and then having to take down and remove all the treatments. EEK!

The CSL calibrated UMIK-1 are very accurate IMO. The non-calibrated UMIK's directly from miniDSP are worthless for what the OP is trying to achieve.
http://cross-spectrum.com/measuremen...ated_umik.html

Keep in mind that a good mic will cost the OP $500-2000, and then getting it professionally calibrated costs extra. Sky is the limit when it comes to quality.

The CSL UMIK's are worth many multiples of what you actually pay.

I wouldn't even bother with EQ until after all your treatments are in place. It is a complete waste of time and money.
Heck, in a perfect world you wouldn't use EQ at all. (Ideally...)
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post #27 of 73 Old 01-11-2016, 08:14 AM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
Turn the EQ stuff off. It will interfere with the acoustical measurements of the room/treatments/system.

Luckily deactivating EQ is easy, it can be done at any time, as can reactivating it.
What isn't so easy is forgetting to take initial measurements of your untreated room as a base-line, and then having to take down and remove all the treatments. EEK!

The CSL calibrated UMIK-1 are very accurate IMO. The non-calibrated UMIK's directly from miniDSP are worthless for what the OP is trying to achieve.
http://cross-spectrum.com/measuremen...ated_umik.html

Keep in mind that a good mic will cost the OP $500-2000, and then getting it professionally calibrated costs extra. Sky is the limit when it comes to quality.

The CSL UMIK's are worth many multiples of what you actually pay.

I wouldn't even bother with EQ until after all your treatments are in place. It is a complete waste of time and money.
Heck, in a perfect world you wouldn't use EQ at all. (Ideally...)
I agree. However, this is an exercise that I hope will help others decide whether or not professional treatments/design is worthwhile. The idea being I can show a progression of how a typical room might change with various optimizations. Something like
  1. Bare room - No EQ and no treatments
  2. Bare room - with EQ
  3. Treatment Level 1 - No EQ, with one one set of treatments.
  4. Treatment Level 1 - With EQ, one set of treatments.
  5. etc.
  6. etc.
I have a CSL calibrated UMM-1. I don't intend to spend big money on a calibration rig. Just items that a hobbyist would have at their disposal. CSL mic + REW. Again, this exercise is intended to give the average joe that wants to build a home theater some idea of what to expect if they decide to add treatments or enlist the help of a professional (and to help me decide whether or not it was money well spent on my part ).

Dude, are you made of leprechauns? Cause that was awesome!
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post #28 of 73 Old 01-11-2016, 12:54 PM
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I wouldn't bother with EQ till you are done- if at all. You probably wont need it.

BassThatHz knows his stuff. (We have likely read the same books it seems.)

Between installs you will have to reset the channel SPL for each because sound power in the room will be reduced at the MLP as absorption is added. (If you intend to watch material before you are done.)

I did the same idea in my space and measured before carpet, after, added sofa, added first reflection absorption etc. etc. It was fun and I learned a lot about just how much it takes to bring the T60 down from where it starts. Adding carpet brought the general decay time down from 1.5s to just over 0.5s. Big change. The largest measurable changes were in the decay times and ETC plots. Frequency response was location dependent and generally smoother at all seats after treatment. One thing I noticed was not all treatments produced measurable changes in plots- but a definite improvement when listening. Adding diffusion makes subtle changes to plots, but very pleasant and appreciable spatial changes when listening.

I wish you the best with how it turns out! Your space looks like an HTOTM contender. Cool stuff.
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post #29 of 73 Old 01-11-2016, 01:43 PM
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Lightbulb

It's critical that the measuring microphone be in precisely the same place for both the Before and After measurements. If the microphone is even half an inch away in any direction the comparison will not be valid. You'll still have somewhat useful information, but not a direct comparison. As proof, the graph below was measured in a home-size room at two locations only four inches away.

--Ethan

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post #30 of 73 Old 01-11-2016, 01:52 PM - Thread Starter
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Quote:
Originally Posted by Serenity_now View Post
...... Your space looks like an HTOTM contender. Cool stuff.
Biggest compliment ever on AVS!!! That would be awesome, but we'll have to wait and see

Quote:
Originally Posted by Ethan Winer View Post
It's critical that the measuring microphone be in precisely the same place for both the Before and After measurements. If the microphone is even half an inch away in any direction the comparison will not be valid. You'll still have somewhat useful information, but not a direct comparison. As proof, the graph below was measured in a home-size room at two locations only four inches away.

--Ethan
..........
Good info. This raises a question for me. I've always been of the opinion that if you can't measure it, then you can't hear it. Those plots are almost the opposite If the plots above are representative of what I hear, then wouldn't that indicate I should hear drastic changes in the sound when I move even slightly in my chair?

EDIT: The follow up question to this will be whether or not there is another way to measure that will be more representative of what I actually hear.

Thanks again!

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