Help needed with REW graphs and room treatments please - AVS Forum
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post #1 of 12 Old 02-25-2013, 07:48 PM - Thread Starter
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I am just getting into the crazy world of REW and sound treatment for my "theater room" that I have been slowly building over the last couple years. I have learned a lot and have made several mistakes along the way but thats what its all about, right. I am to a point now where I'm not sure if I am doing it right or not. I'm sure I have read enough on this forum to completely confuse myself.

The room is 11'7" x 18'3" by 8" tall. The screen wall and the wall to the right are exterior 2x6 constructed and insulated walls. The left wall is full height for 12' and then steps down to 3' tall and it is a 2x4 interior wall with no insulation. Master closet is on the other side of the left wall. The back wall is full height for 8' 2x4 constructed wall with no insulation, then is open for the rest of it for the entrance into the room. There is a bedroom on the other side of this wall that is my office and the closet is in between the theater and the office. Equipment is recessed into the closet wall. More on the construction of the walls later. This room is on the second floor of the home and there is no insulation in the floor but does have 12" of attic insulation above the ceiling of the theater room. A few pictures to help with the visualization.



Definitive Technology Bp 7002 tower speakers with the 12 " subs in the sides. I have since stopped using these subs because I have new sub that is Awesome. not using the Klipsh sub in the picture either. The glass table sneaking into the picture in the bottom right is no longer in the room.



Back wall. not the best placement for the surround speakers and am working on that. The back wall is the closet wall that leads into my office room. You can also see the large opening out of the room.



Here you can see the half wall into the room. I do wish it could be a full height wall with a door but the wife said no way.



The half wall from inside the room. The wife did let me build the full height wall out to the same point as the other wall so the inside of the stair well would be even.

This weekend I was able to take some measurements of the speakers in the room before any treatments or bass traps where installed. I already had the traps built so was easy to install them after making the first set of measurements so as not to change anything else but adding them. I didnt turn off the receiver or even unplug the mic. while doing it to not have any other factors. Here is my first set of measurements from the untreated room. I tried to pay close attention to how the graph are supposed to be configured but I must say there are several different thoughts on the forum so I hope they are the way you all want to see them.

The first one is full range left speaker no treatments no aud.




Full range right speaker no treatments no aud.



Sub no treatments no aud.



All for this post continue in a second. Please hang tight.
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post #2 of 12 Old 02-25-2013, 08:26 PM - Thread Starter
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Then I installed the bass traps I had previously built. I made them floor to ceiling 24"x24" out of the back corner with stacked "white fluffy" insulation from bottom to top with plastic on the back side to contain the fibers and fabric out the outside to match the colors of the theater room. Wife approved of coarse. built like this.





And then installed like this. Sorry for the crappy cell phone picture on this one. Hard to get the pictures with the cell inside the dark room.



I then took some more measurements to see the differance they would make. Now keep in mind this is all with no Audyssey running any correction of any kind.

Here is the sub with no aud and no bass traps installed.




Then with the 3 bass traps installed. There are 3 traps. 2 in the front corners and 1 in the only back corner in the room. all the same size and construction.






Its hard to tell what the traps are doing. I can see from the graphs that it seems to have taken out the sharp drop at about 79hz and smoothed out out some but it didn't do as much as I thought it would but then again I don't know what to be looking for. I think I can see from the waterfall graph that the lower end decays faster then with out the traps? Is this what I should be seeing? I guess I thought it would take out more of the up an down in the db but maybe thats not what they do. Anybody want to chime in on this.

Also based on the full range graphs what are your thoughts on the next step of treatment. I do have some broad band absorbers built in put into the room but I think I am doing them wrong. I have built the 6" thick 20" wide and floor to ceiling to look like columns that would have the same trim mouldings around them as the rest of the room ( crown molding, chair rail and baseboard) I filled them with 3" of OC703 ridged fiberglass insulation from floor to ceiling. Based on the full range graphs are these going to help or hurt my sound in the room. I wanted to do the first reflection, second reflection and then have one more in the back of the room to even out the look like this.



You can see in this picture the 3 column style broad band absorbers and the bass trap in the corner. You can also see the SSA Rumba 12" sub sitting there. More on what I did with placement and the parametric eq later. I dont know much about that stuff yet so I need to learn a bit more before I get into that.

I am very open to ideas on what to do with this room and where to go from here. Thank you for reading through this and if I need to add any more info or change anything just let me know.

Thanks
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post #3 of 12 Old 02-26-2013, 05:20 PM - Thread Starter
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Anybody have any thoughts on my set up. Ill break the questions out here as I think they might be hard to find in the first 2 posts. I really do need some guidance in what direction to take from here.

1) Based on the full range graphs posted first and my room lay out and dimensions what size and thickness of broadband absorbers should I be using?

2) Are the floor to ceiling absorbers with 3" with 3" of space behind them to the wall of OC 703 a good choice or am I way off base with what I have started?

3) Based on the before and after graphs for the sub response and the bass traps installed do my graphs show what I should be expecting to get out of them or do I need to build them differently?

4) Ill add another question here that is not asked above. Are my def tech towers way over complication the room measuring and correcting with the bi-polar design?

5) Is my post to long and windy with way more detail for people to read and care about. Should I break them up a little so its not so confusing and boring to read. Lol?

Thanks for any help you can give.
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post #4 of 12 Old 02-27-2013, 03:55 PM
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Quote:
Originally Posted by cosp600rr View Post

Anybody have any thoughts on my set up. Ill break the questions out here as I think they might be hard to find in the first 2 posts. I really do need some guidance in what direction to take from here.

1) Based on the full range graphs posted first and my room lay out and dimensions what size and thickness of broadband absorbers should I be using?

2) Are the floor to ceiling absorbers with 3" with 3" of space behind them to the wall of OC 703 a good choice or am I way off base with what I have started?

3) Based on the before and after graphs for the sub response and the bass traps installed do my graphs show what I should be expecting to get out of them or do I need to build them differently?

4) Ill add another question here that is not asked above. Are my def tech towers way over complication the room measuring and correcting with the bi-polar design?

5) Is my post to long and windy with way more detail for people to read and care about. Should I break them up a little so its not so confusing and boring to read. Lol?

Thanks for any help you can give.

Hey, well done for taking some measurements, that's a good step in the right direction!

1) You can almost never have too many bass traps. You can definitely have too many broadband absorbers / bass traps though. Without seeing decay time graphs (like T60 over different frequency bands) it's hard to say but I would imagine your room is already on the dry side with a secondary decay tail due to the open plan areas behind / to the side of the room.

2) Good starting point.

3) That's what I would expect, you are not going to get much <100Hz with those types of designs.

I'd start by EQing out that mid-30Hz mode using a good quality parametric EQ and then seeing what's left to deal with in the bass. It would be useful to post a 20-300Hz waterfall or spectrogram for the left / right speakers playing together to see what is going on in the 100-300Hz range.

Master of Minions, Acoustic Frontiers. We specialize in the design and creation of high performance listening rooms, home theaters and project studios for discerning audio/video enthusiasts.
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post #5 of 12 Old 02-27-2013, 05:23 PM - Thread Starter
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Thank you for reading and your reply. Ill see when I can do some more measuring and post what you asked for. I have never measured both speakers together so dont have a graph for that right now.

Im not sure what the T60 graph is. Is that something I can configure in REW with the measurements I already have. Is that the RT60 that is one of the options at the top above along with spl waterfall? If so how do you want it to be configured and I will do it for you.

What type of bass traps do help < 100Hz. Do you think I need to work on that area of the frequency range.

I do have a parametric eq on the sub woofer that seems to work pretty good. I just read the other day that your not supposed the try to take out a dip with it but it good for taking out a peak. Do you find this to be correct?

Thanks
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post #6 of 12 Old 02-27-2013, 05:40 PM
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post #7 of 12 Old 02-27-2013, 05:54 PM
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I probably can't help much with your specific room treatment questions... but would like to add my 2¢ about achieving a smooth frequency response in a given room.

The first and most important step is speaker and listening position placement. Experimenting with those can make dramatic changes to the FR. Unfortunately the scope of placement options can be limited by the practical use of the room. (where doors and access ways are etc) Especially so when it is a HT setup with a large screen to accommodate as well. A screen kind of dictates room orientation and seating position to a degree.

But I still try to achieve a smooth frequency response as possible first with speaker and listening position placement. Next step is bass traps/broadband absorption to help remaining problem areas... then EQ/room correction as the final finishing touch if needed. Getting that big first step as good as possible minimises the amount of work needed in the next corresponding steps. A bad room orientation in that first step can create a lot of problems that means a lot of work is needed in the next steps... and it will never be as good. Needing lots of EQ to help a room is a compromised position to be in as opposed to needing none.

For your situation I don't think you have a lot of scope for placement. You could try moving the speakers a few more feet out into the room or the listening position forward or back a couple of feet either way and see what that does to the frequency response. I think I read that you had said that you had already experimented with sub placement. Good. Just remember speaker and listening position placement is also worth experimenting with. A foot here or there can make quite a difference to a particular null or peak.

..
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post #8 of 12 Old 03-02-2013, 04:50 PM
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I remember this room, we had a short, but nice discussion here, a couple years ago.

I think your absorbers are doing ok.

What's your back wall like?

Have you contemplated a cloud, to address ceiling reflected energy? It would offer more bass damping too.

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post #9 of 12 Old 03-02-2013, 06:35 PM
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The RT60 will tell you how reverberant the room is and whether you are in danger of over-damping it, especially at the high end. There is a Tab in REW for it and you can create it from your existing measurements.

You would ideally like it to be even across the entire frequency range, and around .3.

Bass traps are marginal at low frequencies, and I agree with Ethan about EQing that room mode at 35hz.
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post #10 of 12 Old 03-03-2013, 05:18 AM - Thread Starter
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Quote:
Originally Posted by FOH View Post

I remember this room, we had a short, but nice discussion here, a couple years ago.

I think your absorbers are doing ok.

What's your back wall like?

Have you contemplated a cloud, to address ceiling reflected energy? It would offer more bass damping too.

Wow! Good memory on my thread from a couple years ago. I havent had much chance to work on the room since then but am back at it now. I am going to do the ceiling but wanted to document what the changes are for every step and all the changes I make. Im not sure on the back wall what to do with it yet. I will do something on it just not sure what and how much right now. For now the only thing on the back wall is the bass trap in the corner on the right hand side and even that Im not sure about since the back wall isnt insulated. It seems the low freq. build up a lot since that is technically the next insulated wall. I wonder if It would do any good the do some bass trapping in the office room corners and if it would help the sound in the theater. The other thought was to insulate the closet wall which is the the back wall of the theater. I dont know if this would help or hurt the room. Does an uninsulated interior wall even count as the room boundry for the low freq.?

I will give EQing the 35Hz out and see how that works. I still need to work on the cross over area as I think there is something going on there that needs to be addressed.

Thanks for all your help guys. I is cool we have the ability to gather so much info so easily.
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post #11 of 12 Old 03-03-2013, 10:47 AM
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Yes, knock down that peak, and the sub-to-main issue may likely be an incorrect delay setting between the sub and mains. This is the same as distance. If you manipulate this, you'll likely fix that null in the cross area. That's important, as there's "punch" and impact in that region.

I'd suggest EQ'ing and optimizing the response is the first order of business.

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post #12 of 12 Old 03-03-2013, 04:14 PM - Thread Starter
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I think I will work on the ceiling treatment and possibly the back wall and then EQ the sub and finish it off with re running audyssey and see how that works out. Thanks for all your input.
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