# My screen wall - Not buried for long



## thewire (Jun 28, 2007)

I thought I would share my progress I have been making with digging out the other side of my screen wall. When they dug out our foundation they could not get up the hill so they dumped the stone, concrete, and gravel onto my HT. I have been monitoring the results in REW. 

Here is how the area looked to start with.










Here is how it looks so far. :bigsmile:


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## eugovector (Sep 4, 2006)

So, are you predicting that digging out the back side of the wall will affect your HT in some way?


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## thewire (Jun 28, 2007)

Honestly I just don't know, but it can't hurt. The STC of underground concrete and non underground concrete is different and since half my screen wall was more underground the other side, I expect them to be more equal in STC after I have dig up the wall some. The results so far is that the more I dig up, the more sound I hear from the HT. The area vibrates from low frequencies including the dirt and such in front of the wall. If I press my ear up to it I can make out what voices are saying. In REW so far I have measured improved decay, and smoothed response in all seats in the front row, which I check from time to time. I am unsure also which part of the measurement would be valid or not in the case if there would be a particular interpretation to reading them.


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## eugovector (Sep 4, 2006)

Hmm, sounds interesting. Please post the graphs if you have time.


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## thewire (Jun 28, 2007)

Yes I can do that I have lots of free time. I moved my subwoofers a couple inches during a couple of them to make them symetrical against the wall, but I did a couple where I did not move the mic and the results were the same. I will do some today without the mic moving again. I have removed one rather large stone and made about a dozen trips down my yard to the lake to dump gravel. Really my screen wall was about the equivalant to a 5ft thick concrete wall. I will show a pic of most of these I have removed later also. I think they will be used to continue the stone/concrete walls that we have been building around the property to make one of the recent paths.

Here are measurements of the changes so far.

*This is the filter I use*










This is the first left seat before changes, I have others but this one I have uploaded. I will try some overlays of each seat once I am done. These give a pretty good idea of what is going on. I had ringing so long I could not measure it before I did some changes to room treatments. These are after moving the room treatments again. There is no way moving my subs improved decay that much. I tried for hours with it before I began the digging.










_Moved some drivers about an inch towards the screenwall for these. Purple is before and green is after. Purple is before and blue is after in the others._

*Right seat*










*Left seat*










More progress -

*Left seat*










*Right seat*










_More progress again - moved the subs one inch away from the wall to match left and right._

*Left*










*Right*










*Left2*










*Right2*










*Left2 Decay Previous*










*Left2 Decay Recent*


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## thewire (Jun 28, 2007)

Seats are [left2][right2], and then the two in the back row not tested since the wall changes.​


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## eugovector (Sep 4, 2006)

Yes, I would say that you do not want to move the sub or the mic if you are trying to measure the effect of digging out the other side of you wall. Moving the mic or sub will have a drastic effect on your response.


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## thewire (Jun 28, 2007)

The placement of the mic is pretty simple now so at least the next measurement should be more accurate. I align the mic centered in the headrest at level with the top of the seat leaning the tripod against the seats. In the single time I measured without moving a mic, I did see the same effect as what I measure since moving the subs, but I agree something was not reflected accuratly in the previous measurements with moving the subs. It takes so long to move the area out that leaving the battery on the mic running is not an option at this time. To reveal any differences, I will make an example of moving the mic in each direction one inch and see what happens. Even when I do not move the mic however, ringing that shows on the graphs changes each time. I try to measure over and over until I get one that matches most closely to the previous, and show that. I have covered a ton of progress since the last graph shown above. I can't decide which seat to leave the mic at. I will again turn it off/on without moving it. The right seat measures worst so I have thought about leaving it there. The trouble is I want to be sure that each seat is alright or I will be stopping. If only I had more mics.


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## thewire (Jun 28, 2007)

I will try a before and after test while I move most of what is just gravel I have moved out of the way. That should be a short time enough for me to leave the mic on also, then compare results again.


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## thewire (Jun 28, 2007)

I will leave the mic at my right2 seat, which I find is most difficult to treat second to the right seat which is pretty treatable by comparison of simply adding absorption to the ceiling. Here is three measurements without moving the mic. To get to the 80 setting I need to make 5 clicks (note to self). The first is before moving gravel, the second is after 5 buckets of gravel removed and the third is after 10 removed. Nothing was running except my televsion and fan up stairs.

*Start right2 continued*










*5 buckets continued*










*10 buckets continued*










*Overlay continued*










It seems to continue digging is still the clear winner.


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## thewire (Jun 28, 2007)

With todays progress the 9.0dB headroom went to 8.9dB on the first two mesurements I took. This is the fourth one I took that measured 9.0dB again. The actual target would be 78dB so far, so I will check again if this level has changed any, which it usually does when I see something like that occur. The dip at around 60Hz has gone up and so has some other areas. The ringing does not look much different. I forgot to save yesterdays measurements. The difference is very slight, but I have yet to check the other seats again so not sure if much happened.

*Lower Scale Graph*










*Standard Graph*


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## thewire (Jun 28, 2007)

I am going to stop digging because it is simply to dangerous to continue going. I will get some final measurements of the changes but it not going to be exact because I have been watching some movies. I also need to do some cleaning. I am satisfied each side of my wall is close to being the same.


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## thewire (Jun 28, 2007)

Here is just some of the stones left after the dig. The gravel and dirt went into the lake.










Here is the area dug out.










These are the results of digging out the area, before placing back miscelaneous storage items that currently go in there. Some overlays are results first, some are prior results first.

*Right Final*










*Right Final No Overlay*










*Right2 Final*










*Left2 Final*










*Left Final*










*Left Final No Overlay*










It looks slightly better and some may be a result of inaccuracies mentioned before, but some changes are a result of sound escaping.

What next as far as the very low frequency ringing? Besides moving the rear couch again some, I think the best improvement I could make now would be to replace the non solid core steel door with one that is solid. Then I would of course need some more absorption in the ceiling again. With that I think I could get under 600ms and within +-4dB at the very least for each seat in the front row. There is also the matter of fine tunning the front wall area and rear wall area as well for the subwoofer range. Here are measurements I took using a time delay exe file to left click the start measurement in REW, while I lean against the steel door.

*Right Door Pressure*










*Right2 Door Pressure*










*Left2 Door Pressure*










*Left Door Pressure*










I hope anyone learned as much as I did.


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## Andysu (May 8, 2008)

LOL are you feeling all right today? :coocoo::bigsmile: This reminds me of the strange guy in War of the Worlds digging a hole in the basement.
_Not my blood! Not my blood. We’re the resist Ray. Not my blood!_










I think you should get out more because most million pound multiplex screens will in someway have a small degree of leakage that may be heard most times. I think the percentage is low off, the top of head I think its but don’t quote around 4%.

Why not just fill the hole up with poured concrete. That way it will withstand a Real nuclear blast!

_Not my blood! Not my blood. We’re the resist Ray. Not my blood!_:bigsmile:

I couldn’t see the microphone in the pictures? 

Did you place the microphone on the opposite side of the wall.


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