A Sound Renovation for the Green Room - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 68 Old 02-24-17, 01:13 PM Thread Starter
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A Sound Renovation for the Green Room

You may have come across my "Green Room" threads on this site, and let me tell you: I long for a proper HT with projector, 100+ inch screen, and multiple rows of seating. Until then I can't think of a better way to enjoy what I have than to improve on the sound. Believe me when I say I realize how much improvement the visual aspects need, but that's a derailment destined for another thread.

I'm rearranging my HT room to accommodate the matching center to my mains, so the upgrade bug hit and I just had to get proper HT seating, too! All that led to designing a new layout minus extra furniture and clutter to take maximum advantage of the limited space in my 9 x 13 foot room.
And space IS limited because 12 album crates have to stay by WAF decree
Bless her heart, though; she did let me take over almost every room in the house with audio gear and acoustic treatments.

Now, some if not most of you would agree those massive speakers have no business in that small space, and you'd be right. Their performance is compromised, but not so much they can't develop convincing SS&I. It just takes more attention to detail. Which brings us to the point of this thread: I would like to graduate from REW frequency-domain basics (FR and XO phase) to time-domain analysis and correction (IR, ETC, and EGD). I don't have specific questions at this point, but wanted to start a thread to collect my thoughts - and hopefully your feedback - in one place.

I plan to start my journey from self-proclaimed freshman to sophomore ( ) REW user by trying to identify:
  • the best out of three possible subwoofer locations
  • the worst reflections
  • the best number/combo of bass and broadband traps

So welcome to my thread. I think you'll enjoy it as much as I hope to!
Here are some links to other threads which contributed to my progress:

.
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Last edited by Lumen; 03-10-17 at 09:00 AM. Reason: Added more links to related threads and changed "REW freshman" to "self-proclaimed REW freshman"
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post #2 of 68 Old 02-24-17, 01:35 PM
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Re: A Sound Renovation for the Green Room

Quote:
Lumen wrote: View Post
You may have come across my "Green Room" threads on this site, and let me tell you: I long for a proper HT with projector, 100+ inch screen, and multiple rows of seating. Until then I can't think of a better way to enjoy what I have than to improve on the sound. Believe me when I say I realize how much improvement the visual aspects need, but that's a derailment destined for another thread.

I'm rearranging my HT room to accommodate the matching center to my mains, so the upgrade bug hit and I just had to get proper HT seating, too! All that led to designing a new layout minus extra furniture and clutter to take maximum advantage of the limited space in my 9 x 13 foot room.
And space IS limited because 12 album crates have to stay by WAF decree
Bless her heart, though; she did let me take over almost every room in the house with audio gear and acoustic treatments.

Now, some if not most of you would agree those massive speakers have no business in that small space, and you'd be right. Their performance is compromised, but not so much they can't develop convincing SS&I. It just takes more attention to detail. Which brings us to the point of this thread: I would like to graduate from REW frequency-domain basics (FR and XO phase) to time-domain analysis and correction (IR, ETC, and EGD). I don't have specific questions at this point, but wanted to start a thread to collect my thoughts - and hopefully your feedback - in one place.

I plan to start my journey from freshman to sophomore ( ) REW user by trying to identify:
  • the best out of three possible subwoofer locations
  • the worst reflections
  • the best number/combo of bass and broadband traps

So welcome to my thread. I think you'll enjoy it as much as I hope to!
Goody! Carry on!
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post #3 of 68 Old 02-25-17, 12:03 AM Thread Starter
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Re: A Sound Renovation for the Green Room

The most important part of my intro is missing. I'm such a people-person.
I can't say it any better than cadet did in Post #3 here:
"If you could provide any details I'd greatly appreciate any feedback eager to learn & if someone like yourself is willing to help. I'm all ears."

.
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post #4 of 68 Old 02-25-17, 09:50 AM Thread Starter
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Re: Eeek... Wife Moving at Light Speed!

In preparation for speaker/LP positioning, I've been reviewing AudiocRaver's HTS 2ch Speaker Setup Guide for a Deep Soundstage. Following his advice for first-time use, I chose "The Simple Way," whose first step is to pick a spot for the LP. But in so doing, some immediate questions were raised:

ISSUES & QUESTIONS
  1. With respect to the LP, the back "wall" is effectively made up of album crates.
  2. But w.r.t. room modes, is the back wall the face of the filled album crates, or is it the physical room boundary? I think the albums provide more absorption than reflection or diffusion, so their presence essentially creates an irregular-shaped room, correct?
  3. Considering the seat back protrudes over my ears by about 3 inches, doesn't that place the back wall there instead of at either 1 or 2 above? I imagine the answer lies in the spirit of the method: uncompromised placement, which includes unobstructed listening.

So knowing I can only throw a thick blanket over the back of the seat to ameliorate those reflections, and assuming the back wall is at the front face of the filled crates, choosing a spot for the LP went something like this:
  • 0.25ft = Worst-case distance required between seat and wall for full recline (worst case: inconsequential?)
  • 1.17ft = Best-case distance required behind seat for album crate (best case)
  • 1.42ft = Worst-case distance required behind seat for sub (worst-case: possible location not in stone)
  • 3.00ft = Minimum recommended distance from back wall to center of head
  • 4.67ft = Distance between room's physical back wall and center of head (sum of previous worst-case quantities)
  • 8.58ft = C = (13.25 - 4.67)ft.

Therefore,
dimension "A" = C / 2.4 = 3.6ft
dimension "B" = A x 1.4 = 5.0ft

A Sound Renovation for the Green Room-ss-i-setup-1.jpg

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post #5 of 68 Old 02-25-17, 12:53 PM Thread Starter
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Re: Eeek... Wife Moving at Light Speed!

...(continued from last post)...
Calculation results are approximate until seats arrive!

Because the room is small, the previously derived quantities aren't practical. Separating the speakers by only 5ft on-center, would visually encroach on the display area. What's more, the speakers would be much too close to the seats to allow comfortable ingress/egress. No worries, though, as the guide is quite flexible and has a contingency plan: just determine A, B, and C the best you can given a fixed LP or speaker location. The guide tells us that dimension "C" is not super critical, but that the C/A ratio of 2.4 helps reduce room mode interaction. So in the following calcs, I reduced LP distance to the back wall by a couple feet (increased distance to front wall), and kept the same average ratio of C/A=2.4:
10.6ft = C = Previous value plus 2 feet
dimension "A" = C / 2.4 = 4.4ft
dimension "B" = A x 1.4 = 6.2ft

That's obviously going in the right direction.
The speakers now clear the line-of-sight to the display, but are still not far enough away to fully recline the seats.
For that I'll need Amin=6ft, which now dictates:
C = 13.25 room length - (1.42 sub width behind seat + 0.25 recliner clearance) = 11.58ft
and
C / A = 1.93, which is still within the acceptable range.

So far, so good until we notice this pushes the speaker roughly a foot from the front wall - not a desirable condition from an SBIR perspective. And it also precludes using my tube traps in the corners (should they become needed). Am I approaching this the correct way so far?

.
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post #6 of 68 Old 02-26-17, 10:50 AM
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Re: A Sound Renovation for the Green Room

Ummmmm. Yes?
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post #7 of 68 Old 02-26-17, 11:21 AM
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Re: A Sound Renovation for the Green Room

The correct way is always some set of compromises that still gives a good result.

My own listening area is far from perfect, even far from symmetrical, but still sounds amazing, in my opinion. So the correct way is going to be the way that makes best use of available resources and gets the best sound possible.


One might prioritize like:
  1. spkr and LP placement for convenience AND good sound
  2. symmetry of direct and desired first/early reflection paths
  3. treatment of all unwanted first/early reflection paths
  4. bass trap treatment
    1. for general LF absorption (easier)
    2. for frequency-specific treatment (harder)
  5. Dirac Live
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post #8 of 68 Old 02-26-17, 11:26 AM
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Re: A Sound Renovation for the Green Room

Ummm No ??

As I mentioned earlier kinda, it seems you are doing your best to work with the stuff you have but it seems a bit like trying to fit a C5 cargo plane into a Submarine. It might could be done but to what end. Upon reading your post several times I think it comes down to placing your chairs in the room at the back wall and then fitting or removing everything else so as to provide you with the sound you like....as best can be expected of course.

It seems obvious you and your wife like to watch movies together so FIRST and FOREMOST make the room fit your hobby not the other way around. If album racks have to move out, so be it, if the equipment has to be moved forward...so be it. Ensure that the room is comfortable for the Lumen family and use placement and your dirac to make the sound acceptable or even likeable. I am not sure where you sub should end up, i thought the right side near the front wall seemed very good but with the larger speakers it may need to go against the wall which will increase the bottom end which again may require an adjustment.

Remember that when you get in a pickle trying to plan this layout, just ask us and we will confuse you even more.

Good Listening

Jack

"For those who believe no proof is needed for those who don't believe no proof is possible"
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post #9 of 68 Old 02-27-17, 10:30 AM Thread Starter
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Re: A Sound Renovation for the Green Room

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AudiocRaver wrote: View Post
The correct way is always some set of compromises that still gives a good result.

My own listening area is far from perfect, even far from symmetrical, but still sounds amazing, in my opinion. So the correct way is going to be the way that makes best use of available resources and gets the best sound possible.

One might prioritize like:
  1. spkr and LP placement for convenience AND good sound
  2. symmetry of direct and desired first/early reflection paths
  3. treatment of all unwanted first/early reflection paths
  4. bass trap treatment
    1. for general LF absorption (easier)
    2. for frequency-specific treatment (harder)
  5. Dirac Live
I like the way you think! Your high standards lend me no doubt you've synergistically tuned your system/room. Thanks for spelling out the priorities for me. I'm eager to get started with the nuts and bolts of working with reflections, and will try my best not to shortchange intermediate steps. Speaking of reflections, I revisited your Psycho Pillow thread and am intrigued. I'd rank introducing Psycho Pillow last in the list of priorities. But not because its unimportant; rather, because it's no substitute for careful setup as I'm sure you'd agree. Incidentally, what material would you use if you started from scratch without the Acousta-Stuf material from the LXmini?

As far as I know, identifying reflections is not as straightforward as the mirror or string "tricks" would have one first believe. There are measurement tools (like REW) that can generate plots that make identification easier, but require skill in execution and interpretation - something I hope to someday achieve. Energy Time Curve and Excess Group Delay plots come to mind. Could you please tell me a little more about identifying first/early reflections? Maybe provide a summary like you did for the set-up priorities? As an aside, I'm familiar with the mirror trick - but that just confirms a reflection's existence, not it's desirability. To identify all reflections, you'd have to cover the whole room in reflective tape (lol)!

.
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post #10 of 68 Old 02-27-17, 10:52 AM
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Re: A Sound Renovation for the Green Room

Quote:
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I like the way you think! Your high standards lend me no doubt you've synergistically tuned your system/room. Thanks for spelling out the priorities for me. I'm eager to get started with the nuts and bolts of working with reflections, and will try my best not to shortchange intermediate steps. Speaking of reflections, I revisited your Psycho Pillow thread and am intrigued. I'd rank introducing Psycho Pillow last in the list of priorities. But not because its unimportant; rather, because it's no substitute for careful setup as I'm sure you'd agree. Incidentally, what material would you use if you started from scratch without the Acousta-Stuf material from the LXmini?

As far as I know, identifying reflections is not as straightforward as the mirror or string "tricks" would have one first believe. There are measurement tools (like REW) that can generate plots that make identification easier, but require skill in execution and interpretation - something I hope to someday achieve. Energy Time Curve and Excess Group Delay plots come to mind. Could you please tell me a little more about identifying first/early reflections? Maybe provide a summary like you did for the set-up priorities? As an aside, I'm familiar with the mirror trick - but that just confirms a reflection's existence, not it's desirability. To identify all reflections, you'd have to cover the whole room in reflective tape (lol)!
The Psycho Pillow fill is simply pillow poly fill stuffing from a craft store, in a mesh laundry bag. You can scrunch (an audiophile term) it as needed for best result.

The idea on reflections is to determine the kind you want and the kind you don't want, carefully work with the timing of the wanted ones, and absorb/diffuse the ones not wanted in a way that does not disrupt imaging. First reflections only, after that, the delay is generally enough that imaging is not affected. The first part involves careful measurements, first physically with a tape or laser distance measurer, then refining with REW and a mic. The second kind are eyeballed, because that is good enough. See where they appear most likely and use panels on those surfaces - ensuring that ALL diffused reflections are aimed AWAY from the LP.
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