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post #1 of 105 Old 08-29-2014, 09:27 AM - Thread Starter
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Room Acoustics

New to acoustics - trying to set up a listening room. Have been asking GIK way too many questions so I thought I would post here where no one is obligated to answer unless they want to.

Have about a 12'x24'x7'4" carpeted room, divided by bookcases into a smaller 12x14 room. Ascend CBM170 speakers, Hsu sub, old Yamaha receiver. 90% two channel music, 10% movies.

Became convinced that panels would improve sound more than getting Ascend Sierras. (The next reasonable step up the Ascend ladder. Might still get some Sierras eventually).

Don't want to spend my daughter's college money, and also trying to not annoy my wife with too many acoustic treatments. And I like our listening room - it looks nice. Just doesn't sound so good. Am a bit afraid too many treatments will hurt the aesthetics. Acoustics and visual aesthetics seem inversely related.

So far have the monster bass panel behind my head on back wall (no realistic way to pull the couch away from the wall except for short listening periods). Probably getting 2 Tri Trap corner bass traps next as soon as we can settle on a color (not sure we picked the best color for curtains and monster - but those things can be changed).

Using Gik cause I don't have the time to experiment with building my own. They had good reputation and prices.

Questions I have

1) After the monster bass panel, and tri traps what is the next step? In a small room - more bass traps? Eventually some side reflection panels. One suggestion was a tri trap behind couch, and another thought was a shortened tri trap over book case on ceiling at corner.

2) When can one expect improvement? I think I already hear it since the back wall reflections are helped now. But when does one stop (just for listening - not recording). Will 50% of a studio treatment be reasonable? And what would that be - four or five traps/panels (roughly speaking). The money may run out before reaching 100% nirvana and the space will probably run out before getting 50% there.

Thanks for any replies. Not sure I asked the questions very well.
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post #2 of 105 Old 08-29-2014, 11:05 AM
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Originally Posted by donindc View Post
When can one expect improvement?
Way back when I did the clap test in my room the before and after pretty much sounded like the room in this video. I was very surprised by how much the audio experience improved. Take the test and if the rooms fails add a few panels and try again... repeat as needed.

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post #3 of 105 Old 08-29-2014, 11:31 AM
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Quote:
Originally Posted by donindc View Post
Questions I have

1) After the monster bass panel, and tri traps what is the next step? In a small room - more bass traps? Eventually some side reflection panels. One suggestion was a tri trap behind couch, and another thought was a shortened tri trap over book case on ceiling at corner.

2) When can one expect improvement? I think I already hear it since the back wall reflections are helped now. But when does one stop (just for listening - not recording). Will 50% of a studio treatment be reasonable? And what would that be - four or five traps/panels (roughly speaking). The money may run out before reaching 100% nirvana and the space will probably run out before getting 50% there.

Thanks for any replies. Not sure I asked the questions very well.
Without room measurements and pics, your not giving me enough to make any sensible recommendations. Without such, it would be pure guesswork.

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post #4 of 105 Old 08-29-2014, 11:44 AM - Thread Starter
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Clap Test - there is pretty much no clap echo in the room with rug and furniture. Bass is the bigger problem I think. I watched the video - reminds me of my daughters school.

Pictures attached hopefully. I could try to diagram the room but not sure that would help more. Yes - the blue needs to change I think! Long story that it is better not to go into.

Both GIK and RealTraps say an experienced acoustic technician doesn't need to take measurements, and I have been working with GIK so far. I don't have a microphone and hearing them say that, I haven't bothered to get one. Maybe it would help to get some measurements so I hit the big issues before running out of room to add things.

Thanks
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Last edited by donindc; 08-29-2014 at 12:15 PM. Reason: clarity
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post #5 of 105 Old 08-29-2014, 11:52 AM - Thread Starter
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Thinking I would get rid of that bookcase in middle picture and put two Tri traps there.
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post #6 of 105 Old 08-29-2014, 12:06 PM
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Quote:
Originally Posted by donindc View Post
...Both GIK and RealTraps say an experienced acoustic technician doesn't need to take measurements, and I have been working with GIK so far. I don't have a microphone and hearing them say that, I haven't bothered to get one...
I'd bother to get one.

UMIK-1 from Cross Spectrum Labs (about $100, much less than tuition) and REW (free) and you can see what you are doing.

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post #7 of 105 Old 08-29-2014, 01:55 PM - Thread Starter
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I'd bother to get one.

UMIK-1 from Cross Spectrum Labs (about $100, much less than tuition) and REW (free) and you can see what you are doing.
Thanks
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post #8 of 105 Old 08-29-2014, 02:22 PM
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A little cheaper is the Dayton USB mic

http://www.parts-express.com/dayton-...phone--390-808

You can probably ask in here which (if either) is preferable.

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post #9 of 105 Old 08-29-2014, 09:45 PM - Thread Starter
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I suppose the point is - how can one know how far it is to a destination - unless you know where you are starting from. Trying to get to NYC from Hoboken is much different than from LA.

To some experts the rough dimensions of a room are enough - they seem to know from experience what is needed with just pictures or diagrams.

But if you are of the "trust but verify" school of thought you get a microphone and measure.

Last edited by donindc; 08-31-2014 at 09:12 PM. Reason: grammar
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post #10 of 105 Old 08-29-2014, 10:28 PM
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Originally Posted by donindc View Post
I suppose the point is - how can one know how far it is to a destination - unless you know where you are starting from. Trying to get to NYC from Hoboken is much different than from LA.

To some experts the rough dimensions of a room is enough - they seem to know from experience what is needed with just pictures or diagrams.

But if you are of the "trust but verify" school of thought you get a microphone and measure.
I'm the verify by ear type...
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post #11 of 105 Old 08-31-2014, 09:21 AM - Thread Starter
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I am just new and just dabbling in this so am not arguing a point, but rather asking to learn....

It seems Floyd E Toole is considered one of the most knowledgeable men on room acoustics. He is not against bass traps but doesn't use them in his own home http://www.soundandvision.com/conten...-audio-insider and says that furniture and curtains can do a lot to tame room acoustics

"... I suggest more furniture, or more acoustical treatment, mostly on the side walls. Either or both will be beneficial. In general, surface irregularities - bookcases, display cases, tilted pictures, etc - are useful, as are purchased "diffusers".... A certain amount of absorbing material may be needed if the room is too live, but don't overdo it; excessively dead rooms are not pleasant places in which to spend time. Scattering the sound using furniture or irregular surfaces makes whatever absorption that is in the room work harder, and the sound energy is preserved."

"Of course, all of this and more is explained in my book: "Sound Reproduction", Focal Press 2008."

http://www.axiomaudio.com/boards/ubb...opics/317070/4

(I should note he does see important uses for acoustic treatments in certain rooms - see the link. Also please note - I have not read the book. In it he recommends bass traps for certain setups - from what others on the forum have said)
--------

His former colleague at the NRC, Alan Lofft, goes further:

"The answer (to wayward reflections) to this is to have a reasonable mix of domestic furnishings that reflect and break up sounds as well as providing some absorption. Indeed, a typical North American living room--with carpeted floor, fabric-upholstered furniture, drywalls at the side with some shelves, bookcases, and some fabric window treatments--usually results in a room that works well acoustically for both music and home theater. It's easy to get obsessive about applying special "treatments" to a home theater, in the misguided belief that this will bring huge gains in sound quality."

"And what of "bass traps," those expensive padded cylinders and screens that are sold to naive audiophiles and claimed to absorb problematic standing waves in the low bass? For the most part they don't work, because the wavelengths of low bass frequencies are so large that any "trap" would have to be of ungainly dimensions to become effective. They can be built (there are several in the NRC's listening room) but they are large and ugly. No domestic partner, no matter how tolerant, would put up with them."

"So there you go, Danny Decorators, a little holiday project for the whole family: scatter a few throw cushions about the room to soak those nasty reflections."

http://www.axiomaudio.com/roomacoustics
-----------------

Compare this with the many professional opinions and research that shows that some (most?) people strongly prefer tamed bass and suitably controlled reflections. And reading what many purchasers of these products say - that they make a ton of difference - one is left scratching one's head. Many many satisfied customers with measurements.

Seems that a lot of bass trapping and side reflection taming is not every expert's recommendation. Maybe it is better to measure first, do a little at a time, and not too quickly buy into the recommendations of acoustic treatment companies, but keep an open mind.

In my limited experience and reading, treatment companies like GIK and Real Traps are honest and well informed/experienced dealers who go out of their way to help even folks who are not buying their products - so no slam against them personally. Just noting the difference of expert opinions. Unless I am misunderstanding the above links.

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post #12 of 105 Old 08-31-2014, 08:48 PM
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It seems Floyd E Toole is considered one of the most knowledgeable men on room acoustics. He is not against bass traps but doesn't use them in his own home ...and says that furniture and curtains can do a lot to tame room acoustics
That's what I have in my room and it has zero issues. The only 'treatment' I have is thick textured wallpaper, which is amazingly effective in taming high frequency reflections. Otherwise it's just full carpet, textured ceiling, lots of shelves filled with books, fully curtained windows and upholstered furniture. When you look at pictures of rooms that people complain about they always have vast expanses of bare walls, bare floors and smooth ceilings. I also don't have bass traps. Neither does Carnegie Hall.

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post #13 of 105 Old 08-31-2014, 09:08 PM - Thread Starter
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Thanks, Bill

Zero issues - is your room fairly large?

Where are you in NH? I grew up in Newton, NH.

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post #14 of 105 Old 09-01-2014, 07:25 AM
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Thanks, Bill
Zero issues - is your room fairly large?
Where are you in NH? I grew up in Newton, NH.
My room is 15 x 20 feet. I'm in Laconia. Never heard of Newton, it must be one of those post office and a gas station towns. I once lived in Georges Mills, which fits that description.

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post #15 of 105 Old 09-01-2014, 07:39 AM - Thread Starter
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Ah yes - near Winnipesaukee. Newton is down near Haverhill, Mass. East of Salem.

Small room and no need of acoustic treatment. I guess there are many factors to sound.
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post #16 of 105 Old 09-01-2014, 09:19 AM
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Small room and no need of acoustic treatment. I guess there are many factors to sound.
It's not that my room isn't 'treated', just that all the treatments are part and parcel of the room, rather than add-ons that serve no other purpose. For instance, when I remodeled I used wood fiber ceiling tiles, for their acoustical properties, rather than drywall. I did full carpet rather than wood or tile flooring, for the same reason. The same for the thick textured wallpaper instead of paint. You wouldn't walk into my room and say 'Look at all the sound treatments' but they're there.
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post #17 of 105 Old 09-01-2014, 07:42 PM
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Here's some thoughts from a respected AVS Member: Ethan Winer with a cameo from his wife

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post #18 of 105 Old 09-01-2014, 07:58 PM
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I also don't have bass traps. Neither does Carnegie Hall.
I suspect you really do already know this, as you have always seemed quite knowledgeable, but that is not a valid comparison. The issues and solutions in very large rooms are very different from those of small rooms.
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post #19 of 105 Old 09-02-2014, 06:21 AM
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The issues and solutions in very large rooms are very different from those of small rooms.
There's not as much difference as you might think, the main one being the Schroeder frequency. Boundary interactions that cause problems in small rooms cause the same problems in large rooms. The main reason why a home is much more difficult to deal with is flat surfaces. What you'll find in great venues, ranging from Carnegie Hall to the theaters on Broadway to the Royal Albert Hall, or Shakespeare's Globe Theater, even to the Coliseum in Rome, is the minimal presence of flat surfaces. When flat surfaces aren't present you don't have to apply fixes to the problems that they create.

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post #20 of 105 Old 09-02-2014, 06:49 AM
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Several thoughts:

1. Getting a measurement mic and REW(or equivalent) will be the best money spent if pondering acoustic treatments. It also pays dividends in other areas such as system integration.

2. People most often neglect the budget on speakers for some odd reason. They spend a thousand dollars on an AVR then pump that through garbage speakers. Good speakers should last a lifetime if taken care of, so pony up now and avoid the upgradeitis everyone else suffers and the money thrown away in the process. BTW, I'm not speaking about your speakers specifically, im not familiar with them at all.

3. If you want some serious suggestions post a diagram with dimensions.

4. Unless that partition is fairly significant, your rooms dimensions are multiples of each other 12x24 so you'll likely have some serious modal behavior at ~90Hz multiples. Serious modal problems take a LOT of treatment to address, so unless you want a ton of treatments the best you can do is help those.

My suggestion would be get some measurement capability and measure and treat accordingly. Or if going at it blind, treat all corners with at least 2' span with some bass trapping(faced not BB) and hit your first reflection points with some BB absorption. The first reflection points that would likely pass WAF would be behind the front speakers and side walls. Its unlikely that a cloud will pass WAF. Depending on the distance from back wall it may need treatment also.
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post #21 of 105 Old 09-02-2014, 07:00 AM
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Maybe it is better to measure first, do a little at a time, and not too quickly buy into the recommendations of acoustic treatment companies, but keep an open mind.
Words to live by (and save a fortune).
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post #22 of 105 Old 09-02-2014, 05:51 PM - Thread Starter
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Here's some thoughts from a respected AVS Member: Ethan Winer with a cameo from his wife
Thanks

I appreciate that you didn't send a link to the video with the other woman! Let's keep it G rated.

My feeling is that Ethan knows more about room acoustics than anyone else - outside of maybe whoever is chief engineer at RPG. But he is one of many recognized experts - some of whom have different views. Opposing views both of which are buttressed by science and measurements and double blind tests.
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post #23 of 105 Old 09-02-2014, 06:10 PM - Thread Starter
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1. Getting a measurement mic and REW(or equivalent) will be the best money spent

2. People most often neglect the budget on speakers for some odd reason. .

3. If you want some serious suggestions post a diagram with dimensions.

4. Unless that partition is fairly significant, your rooms dimensions are multiples of each other 12x24 so you'll likely have some serious modal behavior at ~90Hz multiples.
NicksHitachi - thanks for the info - lots to ponder there.

I feel like I have only a limited amount of money and even less space to put up bass traps (really limited on corners that can be treated - even ceiling corners - but maybe with some creativity). I am trying to decide whether it is worth putting $70 toward a microphone I would use only a few times. I guess I could resell it. I think right now it is either the treatments I can fit or better speakers - not both. But the treatments I can fit may be good enough for now. I can add more later when room use changes - or other ideas of how to add traps come to me.

I CAN afford to post a room graph with better measurements - hopefully soon. The partition is not bass proof, I am sure - so maybe I can treat the corners of the other part of the room - good idea. But there is a DAF factor there - daughter approval factor. We gave her that 1/3 of the room for her own space.

I actually think a cloud that matched the ceiling would pass WAF - but wouldn't do much for bass which is the bigger problem as I understand it in small rooms.

Right now there is a GIK monster behind my head in listening position - on back wall. Helps a lot. Two bass traps will be ordered as soon as GIK responds (holiday weekend)- to be placed in the one corner I think could fit them. Other corners have doors or soffits or electrical panels.

Moving the couch out a foot or two doesn't seem to work aesthetically - but I keep looking at that. That would allow a trap in back of the couch which has a foot of air underneath it.

It does seem like there is one camp of experts saying more bass traps - you can't have too many. And the other camp saying that furniture is sometimes good enough.

Thanks for the help! I am trying to use this information.

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I am trying to decide whether it is worth putting $70 toward a microphone I would use only a few times.
Like everything else, it becomes part of the hobby. I use mine "only a few times" every few months.
It seems there's always something to try or to learn. Even if there are things you can't change, understanding your system (which includes the room) will help you get the most out of it.
I would get the mic, remove all the bass traps, and start from scratch. That way, at least, you're putting the stuff you've already bought to best use.

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post #25 of 105 Old 09-02-2014, 08:48 PM - Thread Starter
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I would get the mic, remove all the bass traps, and start from scratch. That way, at least, you're putting the stuff you've already bought to best use.
Thanks. Makes some sense - I guess I am lazy and want an expert to tell me what to do. Then I am frustrated that the experts disagree with each other. LOL

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post #26 of 105 Old 09-02-2014, 08:51 PM
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Be the Expert
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post #27 of 105 Old 09-02-2014, 08:57 PM - Thread Starter
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That makes too much sense!

Who is in your picture, Ray?
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post #28 of 105 Old 09-02-2014, 09:29 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
There's not as much difference as you might think, the main one being the Schroeder frequency. Boundary interactions that cause problems in small rooms cause the same problems in large rooms. The main reason why a home is much more difficult to deal with is flat surfaces. What you'll find in great venues, ranging from Carnegie Hall to the theaters on Broadway to the Royal Albert Hall, or Shakespeare's Globe Theater, even to the Coliseum in Rome, is the minimal presence of flat surfaces. When flat surfaces aren't present you don't have to apply fixes to the problems that they create.

Firstly Carnegie Hall is a multi-performance space venue! It isn’t just one Hall!

I have assumed that you’re referring to the SternAuditorium.

Deducing acoustic similarities between the lower frequency qualities of your space and that of Stern Auditorium, struck me as being impossible, specifically in the context of which you replied.

Stern ‘Auditorium’ has at least 100-times the cubic volume of your acoustic space, and is of an entirely different shape, and comprised ofutterly different absorptive and diffractive qualities.

However, you caused me to pause and do some research: I attempted to fit your statement into, a scientific model, a mathematic model, and a common sense model, but I wasn’t successful. There is no agreement between your statement and that of the aforementioned.

Ultimately, I revisited Schroeder's math, which describes via mathematical proof “the cross-over frequency that marks the transition from the individual resonances of a multimode system to overlapping normal modes, when express as a crossover wavelength, equals – within a numerical constant – the diffuse-field distance in both three- and two-dimensional resonators.”

The math is very specific but may be simplified for practicality in estimating and contrasting such qualities of acoustic spaces, as document by both Toole - 2000 SQRT (T/V), and Everest’s: 11250 SQRT (RT60/V).Both of these approaches provide reasonable, but slight different estimates of modal density; however, Schroeder’s equations are more precise. Regardless of these variants they all share a common denominator of equal weighting V – volume, second only to T-time.

Volume is the underlying factor which traverses all equations, relating to modal density of lower frequency’s and the reverberant qualities ofhigher frequencies!

Therefore, it is physically impossible that the depicted volume deviations between these two spaces could in anyway, what-so-ever, produce a similar modal density – impossible. Therefore just because Stern ‘Auditorium’(2800-seats) doesn’t have / need bass traps, doesn’t suggest that your spaceshouldn’t, either, the math suggests that you should!

I have attached a solid overview of the math and pictures of Stern ‘Auditorium’ as to remove any doubt, in anyone’s mind, that these two acoustic spaces are even remotely comparable, in any way, at any level, from any perspective, etc. They cannot! Not scientifically, not mathematically,not even pictorially!

http://downloads.bbc.co.uk/rd/pubs/reports/1992-08.pdf

http://www.google.ca/url?sa=t&rct=j&...74115972,d.cWc
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Last edited by Garidy; 09-02-2014 at 11:19 PM.
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post #29 of 105 Old 09-02-2014, 09:34 PM
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I have attached a solid overview of the math and pictures ofStern ‘Auditorium’ as to remove any doubt, in anyone’s mind, that these two acoustic spaces are even remotely comparable, in any way, at any level, from anyperspective, etc.
They are both rooms.
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post #30 of 105 Old 09-02-2014, 09:38 PM
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they are both rooms.
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