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Discussion Starter #1
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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Discussion Starter #2 (Edited)
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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Discussion Starter #3 (Edited)
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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Discussion Starter #6 (Edited)
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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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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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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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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Discussion Starter #10
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.


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. :confused:

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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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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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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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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Discussion Starter #14
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.

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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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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I still dont understand the whole fuss about flat frequency responses? to me flat is dead.
 

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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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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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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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