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DIY construction methods of hang-able acoustic panels (not fixed frames) - Page 4

post #91 of 137
5/2/11 at 7:34pm
Quote:
Originally Posted by aackthpt View Post

I wasn't referring to your stuff localhost127, I was referring to testing the AT transparency that mtbdudex was doing

ahh, my mistake as well.

and i might note (regarding mtb's testing), when it comes to broadband absorption of specular energy (reflections), we shouldn't be measuring frequency response - but instead use the ETC to measure total specular energy at a reflection point before, and after the broadband absorption has been placed. since ETC is frequency independent, this will tell us how much the overall reflection has been attenuated. we don't care about absorption of specific frequencies. this is to attenuate early reflections, so all we care about is the total energy of the reflection and if the broadband absorber satisfied the requirements (e.g. attenuate signal -20dB of the original signal).

this is a must read regarding different types of fabric:
http://www.gearslutz.com/board/bass-...absorbers.html

specifically, this post:
http://www.gearslutz.com/board/6424136-post4.html
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post #92 of 137
5/2/11 at 8:06pm
It just came to me a moment ago that SPL only doesn't account for all energy in an acoustical system as you say. Comparing ETC is one route to fix that. I believe another is to compare phase as well as SPL.

I know I don't have a complete grasp of control theory and this whole thing of phasors and such (need some study!) but I think I do recall needing both to completely characterize the behavior of a system.

I haven't completely reviewed the threads to which you linked, but I do think that SAC is suggesting to run the ETC in a scenario wherein the panels are placed on the wall in the room, which is a bit of a different setup than mtb's with the sound firing through the material under test. Such a test (of a specific reflection present / not present rather than mtb's looking for sound passed through or not) would definitely give you the actual needed information but has the disadvantage (I think) that it is not possible in practice to window the analysis (to see the frequencies reflected / absorbed) while maintaining enough frequency resolution to be useful.

But then the question "How much sound at a certain frequency goes through this material" is a different one from "What is the performance of an absorbent panel faced with X fabric vs Y fabric vs bare". The first actually has the advantage that one could use a material testing well as a grille cloth too. I think that's an intriguing idea, actually. Anyway, the answer always depends on the question asked!

I think if you just ran an ETC with mtb's setup, you might be able to compare the height of the initial response (if the software isn't normalizing) but since most energy is in low frequencies there could probably be a high-ish HF reflectivity and/or absorption and not see a large difference.

I think we run into the issue here of whether it is better to test a system as a whole or to reduce the system down into component parts and test them individually. Both have merit in a given situation, and ideally both would probably be done.
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post #93 of 137
5/3/11 at 8:21am
Quote:
Originally Posted by aackthpt View Post

I haven't completely reviewed the threads to which you linked, but I do think that SAC is suggesting to run the ETC in a scenario wherein the panels are placed on the wall in the room, which is a bit of a different setup than mtb's with the sound firing through the material under test. Such a test (of a specific reflection present / not present rather than mtb's looking for sound passed through or not) would definitely give you the actual needed information but has the disadvantage (I think) that it is not possible in practice to window the analysis (to see the frequencies reflected / absorbed) while maintaining enough frequency resolution to be useful.

i think the question that needs to be asked, is why are we measuring the frequency response of a broadband panel (meant to absorb/attenuate early specular reflections), to determine if a particular fabric bears any change??

broadband absorption should *only* be placed at areas of incident energy that will be reflected towards the listening position within the ISD. (ignoring bass traps/LF modal issues - an entirely different approach).

we do not care about removing/absorbing XdB energy at Y frequency from the room. we are discussing specular reflections, which should not be broken down by frequency.

absorption isn't to be placed blindly in a room unless there is a specific need to address specular energy at that particular location (measured within the time domain).

i dont believe testing the frequency response of different 'fabrics' on a broadband (specular) absorber panel is necessarily relevant. the ETC is the tool that will display whether *any* energy is not being attenuated to the design requirement (and making it to the listening position). and thus, thicker absorption can be placed, the panel can be mounted differently to change the angle of incidence, or the absorption could be spaced further from the wall --- and retested via ETC to verify the broadband absorber is performing to combat the problem it was procured for.


again, i recommend anyone interested to read this post:
http://www.gearslutz.com/board/6424136-post4.html
as well as the rest of that thread.

Quote:
But then the question "How much sound at a certain frequency goes through this material" is a different one from "What is the performance of an absorbent panel faced with X fabric vs Y fabric vs bare". The first actually has the advantage that one could use a material testing well as a grille cloth too. I think that's an intriguing idea, actually. Anyway, the answer always depends on the question asked!

I think if you just ran an ETC with mtb's setup, you might be able to compare the height of the initial response (if the software isn't normalizing) but since most energy is in low frequencies there could probably be a high-ish HF reflectivity and/or absorption and not see a large difference.

the initial response (direct signal from speaker --> ears) will not change.
we can place a fabric on the broadband absorber, measure pre- and post- via the ETC, and see if there is suddenly any energy being reflected from the absorber. we don't care if the fabric has a change in absorption at a particular frequency or even a freq range. we only care about the total energy (independent of frequency) that is reflected and thus will combine at the listening position with the original signal.

angle of incidence is very important! and mtb's test regarding the 'reflectivity' of one particular fabric will not necessarily translate to another user's room, as angle of incident will vary. we also must bear in mind the absorber itself (without fabric) will tend to reflect (e.g OC703).

Quote:
I think we run into the issue here of whether it is better to test a system as a whole or to reduce the system down into component parts and test them individually. Both have merit in a given situation, and ideally both would probably be done.

when it comes to specular energy (reflections), we measure with ETC one speaker at a time - so we can realize and then attack the specific reflection points that are impeding the ISD from each sound source (speaker).

if anyone has anything to add or correct, please chime in!
but i think spending so much time and energy on the frequency response for sonic energy that functions as rays is not entirely relevant during the treatment process. fixing the issues in the time-domain will generally solve the frequency response problems for us. absorbing first reflection points attenuates the reflection that would otherwise combine at the listening position with the original signal constructively and destructively, to impede on us the most conventional frequency response issues (e.g. comb-filtering). by addressing specular energy via the time-domain (and ETC) --- this will likely solve the bulk of the freq response issues.

one can then use the frequency response (waterfall) from 0-300hz, and begin to address modal and decay issues for the sonic energy that functions as waves.
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post #94 of 137
5/3/11 at 9:19am
Quote:
Originally Posted by localhost127 View Post

i think the question that needs to be asked, is why are we measuring the frequency response of a broadband panel (meant to absorb/attenuate early specular reflections), to determine if a particular fabric bears any change??

I agree that's a good question. I noted the possible use of the fabric as grille cloth to point out that the testing done isn't actually answering that question. But I think that the testing mtb is doing has value, because I could see people wanting grille cloth printed with pretty pictures to stretch over surrounds installed in columns or for false walls - anywhere that accurate direct sound through the fabric is desired.

Quote:
Originally Posted by localhost127 View Post

... mtb's test regarding the 'reflectivity' of one particular fabric will not necessarily translate to another user's room, as angle of incident will vary.

On the other hand I am sure the idea was that if he can prove a fabric acoustically transparent at a range of incidence angles (he tested normal/45/60), that the incidence angle then is not an important factor in performance of a device as its covering is concerned. This point of view could have its utility.

It's also worth noting that using ETC is beyond 99% of DIY type / amateur's capabilities or level of interest and time to spend on acoustics. They just want some simple guidelines on how to treat their rooms, and there's nothing wrong with that. It's perfectly workable and as long as they don't get exposed to too much broscience it produces a result that fits the purposes of their listening space. It's not as though anyone reading the DIY thread is working on acoustics at Skywalker Sound.
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post #95 of 137
5/3/11 at 10:46am
Quote:
Originally Posted by aackthpt View Post

It's also worth noting that using ETC is beyond 99% of DIY type / amateur's capabilities or level of interest and time to spend on acoustics. They just want some simple guidelines on how to treat their rooms, and there's nothing wrong with that. It's perfectly workable and as long as they don't get exposed to too much broscience it produces a result that fits the purposes of their listening space. It's not as though anyone reading the DIY thread is working on acoustics at Skywalker Sound.

i have to respectfully disagree. if a user is 'capable' of measuring the frequency response via sine sweep, then they can just as easily measure ETC.

can an automotive performance tuner give tuning advice over the phone without measurements of the engine? would we expect one to?

browsing through these forums, there doesn't seem to be any lack of measurements (or enthusiasm for measurements) regarding the freq response. there is no reason why we cannot except people to also perform ETC when they are looking to address issues outside of the LF/modal region. especially when those same people may be looking to cure specular freq response issues --- and may not even realize that the ETC tool (in the time-domain) can likely solve the bulk of their freq response problems!

tell me - if a user goes through the time, energy, money, trouble, etc, to build their own broadband panels, how do they know for certain they are placed properly? the mirror trick is a rough estimate. the only way to know for sure if the panels are placed correctly and are attenuating the reflection to the desired requirements (eg -20dB) for the entire listening position (which could be quite large) - is to verify via ETC, one speaker at a time.

users are expressing interest in room treatments, DIY, etc. we need to encourage that measurements are equally as important as the treatments themselves. measurements should be taken prior to procuring treatments, so one knows the specific issues they need to combat. measurements need to be taken again after treatment has been placed, to verify the original problem has been addressed!. measurements also help us test to verify we have placed the treatments in areas where they are most effective.

without measurements, we seem to have this sweeping generalizations regarding absorption. look how many users are treating entire walls with absorption. absorption needs to be surgically placed only at required areas. the object is not to create a dead room! and even worse, we have some who have installed insulation across their entire wall(s), but then also only do so with insufficient thickness in order to absorb the full range of specular reflections! a measurement would quickly show this. why would one want to suck all of the HF energy out of the room, and leave the mid/lower specular energy free to cause interference? this is a prime example when people install (for example) 1" OC703 covering their entire wall.

while one can assume all reflections points via a mirror and place broadband absorption at sidewall, ceiling, rear wall early reflection points, they may not even be aware that there are other areas of incident that are equally destructive (coffee table), until they can measure with an ETC.

if a user is also applying diffusion (which many seem to do), then the decay trail of the ETC becomes another visual aid to determine how the energy is decaying within the room.

yes, there are many who are not in a position to take measurements (nor they may simply not care) --- but that shouldn't stop us from exploring the proper effectiveness of troubleshooting and applying treatment to combat specific issues within a room - and communicating this throughout the community.
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post #96 of 137
5/3/11 at 11:08am
localhost....what software do you use to make measurements with (REW?). I would like to understand proper way to set up a sweep for an ETC (I use REW).
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post #97 of 137
5/3/11 at 1:23pm
Quote:
Originally Posted by localhost127 View Post

i have to respectfully disagree. if a user is 'capable' of measuring the frequency response via sine sweep, then they can just as easily measure ETC.

Actually we don't disagree, I just have a softer spot for the ideal vs. the practical.

All tools have their uses; it is just a matter of applying the appropriate tool for the specific purpose.
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post #98 of 137
5/9/11 at 4:36pm
Thread Starter 
aackthpt, localhost127, fotto....I missed your comments in this thread.

I'm willing to learn and improve my knowledge and capability based on your comments.

aackthpt (John) is coming to the HEMI meet @ my home we are having this Saturday 14th, we will discuss this then as info sharing for all members who will be there.
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post #99 of 137
5/9/11 at 4:46pm
Thread Starter 
Quote:
Originally Posted by localhost127 View Post

mtbdudex,
very nice work on the corner chunks
i dont believe i saw any waterfall plots? if you really want to see how effective the corner chunks can be, take watefall plots (0-300hz, 0-500ms) and that will give you a good idea of the modal ringing that was cured and what still needs to be addressed. freq response is only one part of the story! time domain will tell you more.
cheers,

I saved the measurements, so I can generate the waterfall plots also, will do and post again.

Quote:
Originally Posted by aackthpt View Post

Your graphs aren't going to show any difference below about 850 Hz since that is roughly the frequency corresponding to 16" wavelength. Below that will just refract right around it. Someone did a test on Gearslutz like this (though with a different aim, like trying to figure out absorption for a material or something), and Ethan suggested the only accurate way to do this all the way down is to make a door of the material and mount it in a wall then run this type of test (after the guy got roundly and obtusely beaten down by SAC, heh). I can find the thread in my info stash if you'd like.

That said, great testing! I may want to use this stuff for some of my panels, so thank you for leading the way on testing it! This test method is awesome, and would be very useful for whatever sort of fabric was under consideration.

When I chose fabrics, I went to the fabric store with someone else, and not only chose one that I could breathe freely through, but also one that preserves the sound of my voice well when I speak through it. I figure that is a pretty decent fabric store test of AT.

Hopefully I didn't miss this from before: how are you removing reflections from the analysis? Tight (really tight) windows?

And did you use any sort of reflective facing on your chunk-style corner bass dampers?

I placed kraft paper on the front of my bass traps to block mid-hi freq:
Bottom corner traps:


Upper corner traps:
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post #100 of 137
5/10/11 at 5:19am
looks great! did you go with 24" or 34" faced corner chunks?
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post #101 of 137
5/10/11 at 9:54am
Thread Starter 
Quote:
Originally Posted by localhost127 View Post

looks great! did you go with 24" or 34" faced corner chunks?


As someone once said "Go big or go home!"
Fortuantely I had room for the 34" x 24" x 24" chunks in back of my 2nd row seats, can I say they are big!
And the lower's while "moveable" the OC705 is very heavy.
50lbs for the OC705 + 2 boards / 3 thd rods gotta put each one in the 65lb zone.
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post #102 of 137
5/10/11 at 10:47am
Quote:
Originally Posted by mtbdudex View Post

As someone once said "Go big or go home!"
Fortuantely I had room for the 34" x 24" x 24" chunks in back of my 2nd row seats, can I say they are big!
And the lower's while "moveable" the OC705 is very heavy.
50lbs for the OC705 + 2 boards / 3 thd rods gotta put each one in the 65lb zone.

wonderful
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post #103 of 137
6/19/11 at 5:19am
Thread Starter 
A quick re-cap on my Front wall corner superchunk with "green" material, these were built 4/2011 thru 6/2011...slow but steady:

Cutting lots and lots of 24" x 24" x 34" triangles....nice to have non-itchy stuff.


Made a mid-support from 3/4" OSB to hold 2/3's of them 36" off the floor.
I did this as part of my front fabric mounting strategy as mid-support of the drywall corner edging and also just in case I ever wanted to tuck a sub there for whatever reason.


Top ones stacked, this is how it was for the 5/14 HEMI meet.


Post meet work, I realized the front wall speaker wires and side wall subwoofer coax needed to be moved....when building the HT I did not know about bass traps.
Cut and re-locate to 29" from the corner....use scrap wood as backer....tape/mud/paint....everything takes time.....


Instead of making a fabric frame, I used drywall corner edge and wrapped the fabric behind that.
Bend them from 90deg to 45deg by hand, went ok.
Also, used kraft paper to reflect mid/hi freq like my other bass traps, just cut and tuck tight.


The fabric was cut with 4" extra top/bottom, and 2.5" each side.
Initially I pinned the top for hanging, then tucked that under the ceiling.


Used plastic putty knife to tuck the sides.
I designed the drywall edge to be 1/8" off the wall, and then tucked the fabric behind that and the cut triangles.
A decent friction fit that stretched taught.

Done and absorbing some of those reflecting LFE!


This method was easy to do, an alternative to making the fabric frame and mounting that.
Yes, I took measurements and will post them.
2nd row is almost deal flat across the LFE zone, 1st row not as good.

I also did freq listening of sub test tones with the RS db meter to grasp the chart to real life, a worthwhile thing to do, helps tie graphs to sound.
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post #104 of 137
6/22/11 at 3:26pm
Ingenious framing method for the superchunk, Mike. I'm not familiar with the drywall corner you are using, but I presume it has some attachment method to make sort of a ready made frame given the smoothness on the front. How is the frame held to the wall?

Eagerly awaiting waterfalls!
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post #105 of 137
6/23/11 at 5:44am
Thread Starter 
Quote:
Originally Posted by aackthpt View Post

Ingenious framing method for the superchunk, Mike. I'm not familiar with the drywall corner you are using, but I presume it has some attachment method to make sort of a ready made frame given the smoothness on the front. How is the frame held to the wall?

Eagerly awaiting waterfalls!

Thx John - I try to simplify construction, and those drywall corner paper beads seemed natural to form a quick/simple edge.
People with minimual tools and basic DIY skills can easily do same method.
http://www.usg.com/sheetrock-paper-f...rner-bead.html
http://www.lowes.com/ProductDisplay?...llow&cId=PDIO1


I forgot to take picts in mid-steps, here's what I did:

Concept is the burlap is tucked all around - and held in, so I needed to be able to have it friction fitted by some appropriate gap on the sides, I swagged at 1/8" to 3/16".

Along top I was going to simply compress the superchunk from ceiling, and along bottom same superchunk to carpet, fabric tucked there.

For the sides, needed to mount the wall metal corner paper beads to achieve the gap.

Wood block basic attachments making:
a) I had some leftover 2" x 3" wood (1 1/2 x 2 1/2), cut them 8" long, (4) pieces
b) Put 45deg on one side (kept grain so when attached via screw the wood would not split) to fit inside the drywall edge
c) pre-drilled 2 clearance holes for 2 1/2" drywall screw, 3" from 45 deg edge and 1 1/2" from flat edge
>>3" from 45deg edge so I could tuck the fabric behind the block w/o hitting the screw

Attaching wood blocks to side walls:
d) Attaching the (4) attachment pieces:
-I wanted gap of 1/8" -3/16" the drywall edge to side walls, so used 2 washers as shims
-the floor ones, I mounted not tight to carpet, knowing I wanted to tuck material under it, I had the plastic scraper so used that as gage for location
-I attached wood blocks to the drywall via those plastic 50lb drywall anchors, first by screwing 2 1/2" drywall screw thru the (2) holes in the wood blocks, then attach drywall anchor into those holes, then re-attaching now using secure drywall anchors
-the ceiling ones, I mounted 2 rows of superchunk below the ceiling, knowing I wanted to compress the superchunk as I tucked the fabric between it and the ceiling
>Of course, I had to notch out the superchunk for these 8" long wood mtg pieces

Attaching drywall edging to wood blocks:
-re-shapped the 90deg corner beads to 45deg by hand, just gently squeeze up/down until its 45deg. (having one of those plastic framing angles is handy as you do this, or use one of the mtg blocks prior to attaching to wall)
-attached the corner paper beads to the (4) just made attachment pieces via small wood screw, also I had that mid support @ 36", so attached there as well to control any bowing. Its head does NOT show thru the burlap. Pre-drill the paper bead by hand holding them in position, noting where to drill, remove and drill small clearance holes.

Pict shows that, RED circle are 4 attachment for corner bead, and BLUE circle also attached for stability/bow control (it did not bow, and the wrapping of fabric side-side actually pulled everything together in tension, but still if I did not have that would have made 6 attachments)


Gosh I'm getting too wordy, sorry, but thats how I did it.
I played with this idea in my mind for a while, actually had the materials prior to the 5/14 HEMI meet but ran out of time to do this.
(you probably saw them while in the utility room looking at the IB sub backside, they were leaning up against the wall there next to the fabric test stand)

Acoustic measurements:
The 24" iMac I use for acoustic measurements is back in my wifes craft room, she's heavily into using it for various projects with her Klic-N-Kut , so I can't do any acoustic measurements until maybe July 4 weekend.
Now that I got my calibrated Behringer ECM8000 mic I'll re-do quite a few measurements.
-Freq plots and waterfalls for LFE (below 200hz) - lets see how thos broadband bass traps are really doing
-Freq plots and ETC for mid-hid (above 200hz) - confirm the side/ceiling panels
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post #106 of 137
6/24/11 at 1:58pm
Thread Starter 
Picture is worth 1000 words.....
I apoligize for wordiness above, this simple pict should help visualize what I described above, hey excel can be useful for quick sketch...
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post #107 of 137
6/25/11 at 8:27am
Ahh OK, the part that _I_ didn't understand before was how the angle was held to the wood. So the wood pieces have a small gap to the wall and the angle hooks behind them. That's a great method... possibly better than the previous winner from this guy on HTshack ( http://www.hometheatershack.com/foru...-finished.html ) as I like the idea of hooking it over the wall-attached wood bits better than the idea of industrial velcro, strong as it may be. Especially, as you say, with the fabric pulling the frame in a favorable direction to help it hold tighter to the wall blocks! Also very cool that the fabric is removable. I'd probably have to line the thin fabric I'm using in my theatre for it to be thick enough to hold, but this is almost easier, and significantly more reworkable, than the usual staple-stretching.

OK so one more question since I wasn't very direct: how are the vertical pieces of corner bead attached to the horizontal pieces of corner bead?
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post #108 of 137
6/25/11 at 11:33am
Thread Starter 
Quote:
Originally Posted by aackthpt View Post

Ahh OK, the part that _I_ didn't understand before was how the angle was held to the wood. So the wood pieces have a small gap to the wall and the angle hooks behind them. That's a great method... possibly better than the previous winner from this guy on HTshack ( http://www.hometheatershack.com/foru...-finished.html ) as I like the idea of hooking it over the wall-attached wood bits better than the idea of industrial velcro, strong as it may be. Especially, as you say, with the fabric pulling the frame in a favorable direction to help it hold tighter to the wall blocks! Also very cool that the fabric is removable. I'd probably have to line the thin fabric I'm using in my theatre for it to be thick enough to hold, but this is almost easier, and significantly more reworkable, than the usual staple-stretching.

OK so one more question since I wasn't very direct: how are the vertical pieces of corner bead attached to the horizontal pieces of corner bead?

John - There are no horizontal corner beads at ceiling or floor.
The fabric is just tucked between the triangle superchunks there.

The bottom has the weight of the above pieces, so that holds great.

The top, it was the starting point so I put 5 pins to hold the fabric initially, with 4" overlap to tuck between the superchunk and the ceiling, removed those pins when all done.
I had leftover absorbent material, so I put that 2 rows down from the ceiling between a row of superchunk, just 3" in at the front face, to put a little more pressure upward onto the ceiling, but since the sides hold the fabric so well all you have to do it stick the fabric between the ceiling and top superchunk.

I never saw that HTShack method, many ways to skin a cat - or build a corner broadband bass trap.
Guess I could post a cliff notes of my method there....I get REW from HTS.
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post #109 of 137
6/25/11 at 5:19pm
Whoa. OK I just figured it out, you have the paper tucked between layers there. It looks like galvanized steel verticals on the sides and horizontal pieces connecting them in the one picture. Finally I put two and two together and realize that is your fluffy... it all makes sense now! I must not have read very well, given that I only just now realized you screwed the corner bead to the wood blocks on the walls. I was too stuck in the mindset of that installation to which I linked. Your method seems easier than constructing a separate frame for sure, and is even more easily disassembled to make changes than I'd initially realized. Cool!

Now... have to finally decide to finish mine! I have a somewhat unusual solution to my situation, assuming it works.
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post #110 of 137
7/1/11 at 7:32am
Thread Starter 
From prior post:
Quote:


Acoustic measurements:
The 24" iMac I use for acoustic measurements is back in my wifes craft room, she's heavily into using it for various projects with her Klic-N-Kut , so I can't do any acoustic measurements until maybe July 4 weekend.
Now that I got my calibrated Behringer ECM8000 mic I'll re-do quite a few measurements.
-Freq plots and waterfalls for LFE (below 200hz) - lets see how thos broadband bass traps are really doing
-Freq plots and ETC for mid-hid (above 200hz) - confirm the side/ceiling panels

I have vacation day today Fri 7/1, re-staining the exterior of the log home, wife/kids at all day summer camp stuff...so before I went outside decided to take some Acoustic measurements 10-200Hz bass.
As reference for seat layout:


Set-up:
REW5, calibrated Mic, running thru the Ext IN.
No Eq and no Audyssey.
This is pure Raw in room IB sub response with the acoustic treatments/room interactions showing themselves.
I also use 1/12 smoothing for LFE plots to show peaks/nulls, when doing 200hz-20khz then I use 1/3 smoothing.

In real world listening I run 80hz xover also.
The fronts R/C/L in Audyssey show as Large, but I set them to small with 80hz xover.

Nearfield + 1st row seats + avg:
Only change is mic moved from seat 1-4 position, so room modes show themself here...


Nearfield +2nd row seats + avg:
Only change is mic moved from seat 5-8 position, room length mode 30hz peak shows here...and it is what it is, besides that pretty consistent in 2nd row.
It's the best row for LFE.


This is a comparison of 1st row vs 2nd row.
With my RS SPL meter I can notice about 4-5db or so more in the 2nd row than the 1st row.
Tested with the infamous KFP skadoosh scene.
When the volume is @ ref level, 0db, and the EP2500 is NOT running "hot" - calibrated norm (EP2500 gain at 12 oclock/ 24 on scale), I get 113db in 1st row and 117db in 2nd row.
When I run the EP2500 full HOT (34 on scale) I got 124db in 2nd row and 119db in 1st row.


Waterfall charts to show decay time.

IB sub 1" nearfield waterfall:
(that 60hz is ac hum, the iMac is plugged into front wall circuit and I forgot to turn off the screen lights above, did it after taking this measurement)


IB sub 1st row-seat#1 waterfall:


IB sub 2nd row-seat#6 waterfall:



Overall I'm really satisfied with the above, broadband bass treatments really do work!
I never did make a upper triangle bass trap for the front RH wall/ceiling corner above the IB sub, and most likely will not, even though I have enough acoustic material to do so.
Based on the above I think I've approached the "diminishing returns point" on bass trapping/control with the corner porus treatments I'm using.

Also, I've stopped using the FBQ2496 for EQ, and just use Audyssey.

I'll run the IB sub thru the Denon 4308CI and show how Audyssey tweaks the bass at some future time, now gotta get doing some outside working.
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post #111 of 137
10/6/11 at 3:58pm
Quote:
Originally Posted by mtbdudex View Post

Got the samples in from Spoonflower last night, simply I was blown away by the picture quality!

Same test as before, I added the Spoonflower to the bottom, also a few from ats acoustics as comparison.

I did the breath test, comparing the Spoonflower material vs the ats acoustic sample pack I have http://www.atsacoustics.com/item--St...ack--1034.html

Subjective rating via breath test:
1) Spoonflower fabric passed more air than the ats acoustic sample I had for the microsuede
2) Spoonflower fabric passed same air - or slightly easier - as the ats acoustic sample cotton weave sample
3) The ats acoustic burlap definitely passed the breath test the most.

Picture quality comparison:
(these are all my original photos, so I can compare them)

This is w/o flash with HT lights on about 50%:


Pict with flash (white balance set according for each shot):


These close ups are all straight from my T1i camera, RAW format w/o any post processing added.
#1 ; the detail in the craters is fantastic, nearly same as original


#2 ; this racoon fine fur detail again quite good


#3 ; the star trails kept streaks and the star colors


#4 ; this B-17 shot in B&W was to see how it fared for B&W....really good


#5a ; tree @ night via spoonflower


#5b tree @ night (blocky weave from local supplier)


#6 reflection test - passed with flying colors!
The cotton weave has less sheen.


Ding - ding - ding: we have a clear winner! Spoonflower .
(Thx luma for pointing them out)

Very impressed with the picture quality, color matching seems spot on, much detail is there, only the star field with the 5 meteorites proved too much for their process to reproduce.

I will take objective freq comparisions later, however I see absolutely no reason not to recommend the spoonflower fabric and process for anyone looking to have Acoustic transparent artwork for their acoustic treatment panel covers.

[edit 3-9-2011: use their Quilting Weight Cotton, http://www.spoonflower.com/spoonflower_fabrics]

Just discovered this thread. Wow! Very nice work. I was looking at Spoonflower to maybe replace some posters I have in my dedicated room. My kids love the posters but I would like them to be less reflective and disappear when the PJ is on. Can you elaborate how these look "in movie"? Any reflections at all?
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post #112 of 137
10/6/11 at 6:03pm
I built 4 for my room. No reflection from them at all.
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post #113 of 137
10/6/11 at 6:48pm
Quote:
Originally Posted by xzener View Post

I built 4 for my room. No reflection from them at all.

Excellent. That is what I was hoping to hear.
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post #114 of 137
12/18/11 at 5:30am
Thread Starter 
I had "leftovers" acoustic material from what I did earlier this year, sitting in my utility room for months.
Wanted to improve the 1st row bass to be more consistent across seat-seat.

Yesterday (Saturday Dec-17) I built a broadband bass trap that goes above my screen.
Basically 2' wide x 4' long panels that straddle the front wall/ceiling space.
I wanted a bigger trap, but due to the screen height and front lights this is as big as possible.
(LH side already has "big" superchunk style trap, 34" x 24" x 24", and RH side is IB subwoofer)

Construction method:
Bonded kraft paper to the front, and mounted them with just air gap for now.
I've got a roll of pink fluffy fiberglass that later I will put behind each one.
My plan is simply put a paper coated drywall corner edge on the top/ceiling edge, and then roll/fold the green burlap for a seemless look like I did the LH trap.

Over Christmas break, when I get back to the ETC measurement/analysis I've been doing, will also take measurements of the room condition as newly installed and then install pink fluffy behind and see what improvements there are.
I realize not "by the book" of having the same gas flow resistivity porous material for a broadband bass trap, but since I had the materials lying around if some "free" improvements can be had why not.
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post #115 of 137
12/30/11 at 10:59pm
Quote:
Originally Posted by mtbdudex View Post

if some "free" improvements can be had why not.

Agreed! Now the question is.... did it work? Measurements or it didn't!
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post #116 of 137
12/31/11 at 9:59am
Thread Starter 
Quote:
Originally Posted by aackthpt View Post

Agreed! Now the question is.... did it work? Measurements or it didn't!

Hey John - Happy New year.
I'll post measurements later, simply it slightly reduced the modal ringing/decay time, but absolutely did not help flatten my 1st few nulls.
For now, I'm done on the bass freq region, will look at specific freq membrane trap as the gearslutz forum is actively doing.
You are right, the big 6' wide opening on the RH wall rear portion is acting as a huge bass trap (good thing).
Possible a Spring/Summer 2012 thing for me to install the dual french doors there.

Also, I'll have to update the ETC thread in the acoustics forum as well, I got the loop-back measurements working (duh, easy) and spend a few hours this morning in the rabbit hole, I mean on the hobby....
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post #117 of 137
12/31/11 at 10:13am
Thread Starter 
Follow-up to an earlier post in this thread related to spoonflower fabric and it's acoustic transparency , Objective AT freq fabric testing - Part I


First, I'm open to re-doing this testing outside in the spring to eliminate any room reflections/effects.
I can see some errors in my actual test method, but hey I'm free labor doing this on the fly.

[edit Jan-2]
What I could have easily done while doing ETC measurements was this:
a) Take ETC of LH speaker as baseline
b) Temp Add 1/4 ply board to LH panels, take ETC
c) Temp Add spoonflower fabric to LH panels, take ETC

Compare to see differences.
Repeat for CTR, RH to see different angles of incidence related effects....


There has been some posts related to the spoonflower fabric and its usage for cover in porus absorbers - concern is it may block frequencies due to its picture printing process, I took a decent picture and zoomed into it for detail:


crop of detail:



It appears each thread is dyed, not printed - which will block/reflect frequencies, and as I got the fabric wet and scrubbed it nothing came out.
(I'll call spoonflower tech support on this)
I'll cut the sample in half, and run it with the wash a few times to see if anything degrades.
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post #118 of 137
1/1/12 at 7:24pm
Thread Starter 
First, Happy New Years!

Measurements - it did happen!
All below are just my IB sub via Ext In w/o any EQ at all, just to see room response.
(I did also take some IB + Mains, which are set at 80hz xover for mains and 120hz as LPF for the IB, those are not posted below, TMI for this post purpose)
Here is base with the "free" above screen traps w/o pink fluffy, this Dec 17th


I took measurements, then added pink fluffy to the void, Dec 27



As stated, the freq response did not improve at all, just the modal ringing slightly, very slightly....most of my LFE is around 300ms, so actually pretty decent
July 1, no trap above screen (saved these from earlier)


Dec-27 trap added above screen without and with pink fluffy freq chart, slightly better at 155hz (which I'm not looking here due to the mains will change that portion)

Dec-27 trap added above screen without and with pink fluffy H20 chart


Dec-30
what I did also find is for my 1st row very dependent on where I put the mic in height position. ie, seat up ear height vs seat down ear height.



2nd row is negligible for height mode change.
Seats 5- 8 all have almost the below response.



Conclusion(s):
1) I'm "done" with adding/tweaking broadband bass porous absorbers in my HT room, overall quite happy - and my wife told me "time to enjoy it!", she's right
2) 2nd row definitely has much smoother bass response, and a nice "house curve"
3) 1st row, if I want to improve the pesky nulls between 30-50hz will need a more advanced strategy, possible membrane absorbers, tbd at this time.
That will be HT acoustics version 1.5 task after more reading/research here and gearslutz, along with some old fashioned book reading.
4) It is important to take LFE readings at the seat up and seat down position (mine are almost 18" different), as well as side-side positions in the seat to grasp each seats response and your strategy.
Also, play sine wave at your trouble nulls and use RS SPL to hear and measure the diff as you go up/down, side/side, and fore/aft to get a understanding of the wave mechanics at play.
That gives intuitive feeling for the issue(s) instead of just graphs/chart/numbers.
5) I'm really curious when I add the double french doors to the HT, and close off the 6' wide opening (huge bass trap now), how the modes will change, and while not obvious now the bass trap above the screen may come into play more then......Summer 2012 thing
6) Knowing now that I got actual almost "nothing" from doing this, would I have done it anyway back then.....possibly I'd wait till the double french doors were installed and see if they caused major null issues.
But, doing this also increased my knowledge of my specific room "issues", so as a hobby part of the learning and tweaking.
7) It's been said before, but I'll repeat:
Label all your measurements immediately!
Taking so many you quickly get lost in them, even when being systematic about the order, if you take 2-3 then you may mis-label one when trying to do in bulk.

This thread has almost reached its conclusion.
I'll add a re-cap to post #1, with some links to portions in the thread for ease of finding stuff.

One thing, when I started about 1 year ago, using pink fluffy for broadband bass super chunks was not widely know here @ AVS, that seemed to be led by gearslutz forum.
For sake of best practices and best cost approach solution, the approach for members in the future should take that into account, and be summarized with the appropriate calculators (localhost127 may have a summary in a post, I'll find that and link it )
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post #119 of 137
1/2/12 at 5:44am
Thread Starter 
Side excursion, since I had the spare OC703 out, I put the sheets on both my acoustic clouds and took measurements.
Was curious if any additional freq smoothing at my 1st row seat nulls.
(was also working on better understanding of the bass management in my Denon AVR-4308CI, various xover of mains and LPF of IB sub to see how the blending occurred)

Baseline:
both clouds are 4" OC703, 12" from the ceiling - 8" air gap, so the added 2" gave 6" OC703 with 6" airgap.
Mains xover 80hz, LPF for IB sub 120hz.
This iPhone4 pict shows the additional 2" OC703 simply placed on top of the existing 4" green burlap wrapped acoustic clouds.



As many here say, "Measurements or it did not happen", so here they are:
(I use 1/12 octave smoothing for bass measurements to truly see the issue)

Really no improvement seen in seats 1 or 2, virtually identical.


Slight improvement in seat 4 (4db @ 90hz) and seat 3 (3db@ 155hz)


For all practical purposes, no improvement in modal ringing, which was not expected as learned from the front screen wall top bass trap exercise I did earlier.


Conclusion:
As is, there is no reason to have 6" of OC703 in my acoustic clouds for improving the 1st row bass null issues.

side comment/inquiry:
While we use 1/12 octave smoothing to see bass issues clearly and decide how to address them, do our ears "hear" that tight or is 1/3 octave smoothing representative of what our ears hear??
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post #120 of 137
1/10/12 at 8:33am
Just wanted to say thanks for posting all this, it's been a great read
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