# Any comments on my measurements



## eclipse911t (Jan 8, 2013)

Good Evening,

I'm new to the forum and recently purchased a UMIK-1. I took a few measurements and adjusted basic EQ, crossover, and phase (sub). I was hoping you all would be kind enough to have a look at my measurements and let me know if you see any major problems.

You can have a peak at my theater and equipment list here:
http://www.hometheatershack.com/forums/home-theater-room-photos-finished-rooms-only/64735-eclipses-dedicated-theater-room.html#axzz2HncYYYFm

Thank you very much for any guidance.


----------



## hjones4841 (Jan 21, 2009)

Looks really good. Do you have room treatments in there?


----------



## brad (Sep 18, 2012)

I would be more interested to see the un-smoothed or smoothed only 48 material rather than 1/3. Also just low end 10- 400 or so un-smoothed to check any peaks nulls
thanks


----------



## eclipse911t (Jan 8, 2013)

Yes I have room treatments. 17 2'x2' 2" Wedge Foam and 2 16x24 super chunks.


----------



## eclipse911t (Jan 8, 2013)

brad said:


> I would be more interested to see the un-smoothed or smoothed only 48 material rather than 1/3. Also just low end 10- 400 or so un-smoothed to check any peaks nulls
> thanks


Here's the good, bad and ugly. Brad, hopefully this shed some light.

The first one is 1/48 smoothing as suggested. The last two are no smoothing as requested.

Thanks for the feedback thus far.


----------



## brad (Sep 18, 2012)

Ahhhhh.. the nasty peaks and nulls are now exposed for what they are...

The room looks great architecturally, but I would comment, after hanging-out in this forum and over at gearsluts for the past 6 months, you should try to look at the following:

1) I'm no expert, but try to get the attention of Bryan from GIK (and visit their site) and also Realtraps Ethan Winer, as THEY are experts and also hjones4841 can give more insight (and there's quite a few more experts on here) both GIK and Realtraps sites, have a lot of info about how to tame your room... I read most of the 38 pages in this forum to better educate myself, as well as that "Master Handbook of Acoustics" by Everest.

2) I would think the placement of the subs in the room is doing something as they look real close to the wall, also I don't see much broadband bass trapping going-on. You should post the dimensions of your room, so mathematically, you can figure-out the room modes and then match that with your measurements. They will tell you to use absorbing stuff in the corners, for sure (which it looks like you have in the front, but not the rear).

3) I had good luck by using REW to generate a sine wave at the particular frequencies that I had either peaks or nulls and then put my ears around in the room and hear the actual drop-outs or increases in amplitude for the given frequency.

4) What does the waterfall look like when you change it to 300 or 400 ms? I feel you should see more ringing and see the noise floor better, that would help to figure-it out.

5) I'm not sure about everyone else, but I'm in the camp that recommends no EQ until the room is the best you can get it acoustically, so I would measure without eq, then start with speaker placement, then low crossover frequency adjustments and maybe broadband absorbing panels, like your super chunks.
Oh, did I mention broadband absorbing panels?? It is not the same as the foam stuff. 

Remember to measure each time you change something, so you can track what your results are, and only change 1 thing at a time.

my 5cents
looks good, though


----------



## eclipse911t (Jan 8, 2013)

brad said:


> 2) I would think the placement of the subs in the room is doing something as they look real close to the wall, also I don't see much broadband bass trapping going-on. You should post the dimensions of your room, so mathematically, you can figure-out the room modes and then match that with your measurements. They will tell you to use absorbing stuff in the corners, for sure (which it looks like you have in the front, but not the rear).


Here are my dimensions. 255" x 206" x 104"
Unfortunately the width and height are practically double one another.


----------



## jim1961 (Apr 8, 2011)

1) Are you measuring one channel at a time for your measurements? 

2) 2" thick wedgefoam unfortunately isnt broadband. I would move towards 4" OC703 with 4" gaps or 12" pink fluffy for 1st reflections points.

3) Your frequency response comes out to about +/- 11db. This needs to be improved. Shoot for +/-5db or so. More bass traps and thicker better 1st reflection attenuation should help things in this regard.

4) Your waterfalls look pretty good until you get to 40hz. Those too will improve with more bass trapping.

5) Recommend a ETC response. It will tell you important things about your room that FR and Waterfalls cant.


----------



## eclipse911t (Jan 8, 2013)

jim1961 said:


> 1) Are you measuring one channel at a time for your measurements?


I am typically using the front left and subs.



jim1961 said:


> 2) 2" thick wedgefoam unfortunately isnt broadband. I would move towards 4" OC703 with 4" gaps or 12" pink fluffy for 1st reflections points.


I believe the foam is good to about 500Hz. I plan to add additional bass traps, but have no plans to replace the foam. Unfortunately the rear wall-wall corners are not suitable due to the entry door and equipment rack. All of the ceiling-wall corners are on the table for discussion. I have a good local source for mineral wool and would be willing to do super chunks around most of the ceiling-wall corners if you think it's needed. I am quite pleased with things since I've added the super chunks, but am of course looking to improve or I wouldn't be here!



jim1961 said:


> 3) Your frequency response comes out to about +/- 11db. This needs to be improved. Shoot for +/-5db or so. More bass traps and thicker better 1st reflection attenuation should help things in this regard.


The measurements shown are the result of Audyssey MultiEQ XT after being measured in 6 positions. I "can" flatten this one microphone position manually by sacrificing others, but have chosen not to at this point. Is it worthwhile to take measurements without EQ while trying to asses the room? Since I have an AT Screen I am considering taking some near field measurements to compensate for the screen with manual EQ and then have a better ability to work on the room. Is there merit in this?



jim1961 said:


> 4) Your waterfalls look pretty good until you get to 40hz. Those too will improve with more bass trapping
> 
> 5) Recommend a ETC response. It will tell you important things about your room that FR and Waterfalls cant.


Can you really effect 40Hz with a 24x24" corner bass trap?
I'll do some reading on ETC (energy time curve?) response this evening.

A big thanks for all your help!


----------



## jim1961 (Apr 8, 2011)

eclipse911t said:


> I am typically using the front left and subs.
> 
> 
> 
> I believe the foam is good to about 500Hz. I plan to add additional bass traps, but have no plans to replace the foam. Unfortunately the rear wall-wall corners are not suitable due to the entry door and equipment rack. All of the ceiling-wall corners are on the table for discussion. I have a good local source for mineral wool and would be willing to do super chunks around most of the ceiling-wall corners if you think it's needed. I am quite pleased with things since I've added the super chunks, but am of course looking to improve or I wouldn't be here!


2" wedge foams affects frequencies down to 500hz, but only evenly down to 800hz -1k.

Edit: http://www.auralex.com/testdata/test/2wedge.pdf

Reading the above link, you might be led to believe its good to about 500hz. But read more carefully, and the test size they used was 96" x 108", not 24"x 24". Big difference.





eclipse911t said:


> The measurements shown are the result of Audyssey MultiEQ XT after being measured in 6 positions. I "can" flatten this one microphone position manually by sacrificing others, but have chosen not to at this point. Is it worthwhile to take measurements without EQ while trying to asses the room? Since I have an AT Screen I am considering taking some near field measurements to compensate for the screen with manual EQ and then have a better ability to work on the room. Is there merit in this?


I would measure without EQ, otherwise you dont really know what the room itself is doing. The better you can tame the room, the less hard Audyssey has to work. Ideally, one could get the room right enough and not need Audyssey at all. Measurements taken at where you will be listening will be the most relevant.




eclipse911t said:


> Can you really effect 40Hz with a 24x24" corner bass trap?
> I'll do some reading on ETC (energy time curve?) response this evening.
> 
> A big thanks for all your help!


More trapping may not solve <40hz problems, but it may help them some. Doubling up 2 24x24 to make a 24x48 or even a 24x72 would help more. Energy Time Curve, yes. Sometimes also call Envelope Time Curve.


----------



## hjones4841 (Jan 21, 2009)

eclipse911t said:


> Can you really effect 40Hz with a 24x24" corner bass trap?


Not really. Wavelengths are very long at lower frequencies. I put 5 GIK Monster Traps in my 12x20x8 room 3 years ago. It helped greatly above about 60-70Hz or so, but did almost nothing for a 26Hz room mode. IIRC, bpape said some type of large membrane absorber is needed for the lowest bass notes.

Don't get me wrong, the GIK Monster Traps made a HUGE difference in my room, but the laws of physics tells us that treating the lowest bass is a challenge.


----------



## eclipse911t (Jan 8, 2013)

I'm considering 8 additional panels of 3" thick rigid fiberglass on the rear wall. This would put my rear wall at roughly 45% absorption 55% reflective. I'm currently at 8% coverage back there. I am thinking I could use Certainteed CertaPro 3" CB150 for the panels and use a spray adhesive to attach a black muslin for aesthetics directly to the panels. Any experience with this method? 

I'm also considering 12' long super chunks along the wall-ceiling corners down each side of the room filled with 24x24x34 6" thick mineral fiber. 

Do you guys think this would be money well spent? 

I'm currently traveling but will get some good no EQ measurements when I return later this week.

One of my concerns about my current measurements is that I have been using a Dell laptop's built in sound card for the audio output. I'll order a USB extension tonight which will allow for HDMI output of the audio signal to my DTC-9.8.

PS: I'm also eager to pull down the panels and measure the room without them. The chunks are a bit more difficult to remove, so they'll likely stay.

Comments always appreciated.


----------



## brad (Sep 18, 2012)

I would think about spacing the panels off the wall to increase their efficiency, 3" panel + 3" space is like a 6" panel. I would watch the adhesive spray with muslin, as you are creating something that is pretty flammable, I'm not sure if the adhesive impedes the airflow either. You should plan to cover whatever the wall surface needs to flatten the low end, not go by a "percentage." Once that is done you can choose to select fabric or covering that will reflect highs to get your high end back, but I would not make the decision to cover a certain percentage of the surface based on looks or surface area, you need to measure as you add to see what works. If you can make your panels and move them around (before covering them)while you measure that will help you. For low end, thicker is better.


----------



## eclipse911t (Jan 8, 2013)

Here are the no EQ no smoothing plots for the sub and mains. I believe there was an 80Hz crossover on the mains. They roll off at 40ish on their own.

I also posted an ETC response for the front left speaker, but know little about how to interpret it. I can see my RT60 is at roughly 200ms, but haven't a clue if that's good or not. 

I did also run a test on my rears (no sub) and noticed the waterfalls looked much worse on the low end. I'm definitely treating my rear wall with 3" Certainteed Certapro Commercial Board CB150. I'm starting with 7 2'x4' panels high up along the rear wall.

Unfortunately the walk ways in my theater are all specifically 30" wide and will only afford a 2 or 3 inch panel, but not 6".

My next addition will be the two 12' long 34" face super chunks down the side wall-ceiling corners. The materials have been ordered and construction should begin this weekend. I can buy a 4 pack of 24x48x6" SAFB mineral wool for $34. Why not get 3 bags and build these things for about $160 framed, covered and mounted.


----------



## jim1961 (Apr 8, 2011)

Show the ETC out to only say 60ms. Its the early returns that count


----------



## eclipse911t (Jan 8, 2013)

jim1961 said:


> Show the ETC out to only say 60ms. Its the early returns that count


Here we are.


----------



## jim1961 (Apr 8, 2011)

Now I see. Thanks.

I would try to get those reflections arriving in the first 15ms down to -20db. Even -15db would be a noticeable improvement. You have 4 peaks in the -10db range. Most likely 1st reflection points. If you can do this, your FR will smooth out some and you will get clearer images.


----------



## eclipse911t (Jan 8, 2013)

So I did some shuffling and took some additional measurements today. The first I took was the black trace below. 

As you can see in the pictures I have 3 2" Auralex Wedge 2'x2' panels not doing much on the rear wall. I measured the location of my first reflection on the ceiling and simply placed the panels right on top of the diffusor and took the measurement in red.

I then removed my two rear panels and set them on top of the two front panels as shown in the picture below drawn in paint as a grey triangle and the result was the blue trace. I think this proves my theory about needing the wall-ceiling corner super chunks.

My plan for the rear wall is also drawn out below using 7 2'x4' 3" rigid fiberglass 3.0pcf panels.

Is this looking better? Thanks much!


----------



## jim1961 (Apr 8, 2011)

I am having a little problem sorting out what all the colors mean. But if I am getting it right, it looks like some progress has been made. How does it sound in comparison to before?

You still have some areas to deal with, but if in listening you prefer the now to the before, I would treat the remaining peaks.

Nice work!


----------

