[Voncarlos]

Hi All,

I recently rearranged the furniture and audio in my "do-everything-room". This has resulted in a nasty upper-bass bloom/boom and a rather overall unmoving bland sound. The sound was fine in it's previous layout, 90 degrees placement from it's current spot and although it could have benefited from some acoustic wall treatment, I could listen happily. However now, I can't even listen to the music!

The speakers are an open-baffle design that I constructed based on the "GR Research OB-5s". The drivers, x-over components and basic layout come as a kit from "GR Research". See the thread on building these at the GR Research circle here: http://www.audiocircle.com/index.php?topic=59326.0. The top is MTM and the 2 bottom drivers are ported out the back.

I do not have any testing equipment, but I have spent weeks and weeks poring over many acoustic related forums and commercial sites. I could get the SPL app for the iphone if need be.
www.3daudioinc.com
www.johnlsayers.com
www.studiosixdigital.com
http://forum.studiotips.com
http://forums.musicplayer.com
www.gearslutz.com
www.audioholics.com
www.readyacoustics.com
www.gikacoustics.com
www.realtraps.com
www.atsacoustics.com
www.asc-hifi.com
www.ethanwiner.com
www.knaufusa.com
http://www.ethanwiner.com/density.html
http://www.ethanwiner.com/basstrap.html

From what I have read, it seems that one should just treat the corners with bass-traps and then balance out the room walls with specific absorbers or diffusers.
Besides the obvious treatments, I have some concerns about the speakers being OBs, the beam along the left, East, ceiling between areas A and B and the soffit that comes to a stop halfway into the room.

I'm planning to do this DIY, I've already bought 160sqft. of 2 inch 703-plain and 48sqft of 2 inch 703SKF. The 3lb. rigid fiberglass is actually made by Knauf but the term 703 has become the catch-all name for 3lb. rigid fiberglass. Because I couldn't wait to see what the treatment would do, I stuck a sleeve (that's a package of 10 2x4' sheets) of 703 in each corner behind the speakers. Wow! what an improvement! Okay, let's see what happens when I open those sleeves and just make the thickness 6 inches with the front face being a SKF panel and add a single plain 703 to the right wall (West). OMG! The music is so musical! The imaging has taken on an incredible sense of each performer having a aura of silence/blackspace around them! In fact the whole blackspace has gone quieter and I had to turn the volume up. And of course the bass notes are wonderful now, they are tighter and seem to go even lower now. I think the lower notes were there all along, just all muddled together. This is something everyone needs to try!!!
So now I'm a disciple of room treatment and want to do this better. The next few images show the floor-plan, actual views and a layout of the traps I was going to make.

Looking for opinions, thoughts and ideas.

Thanks in advance,
Carlos

Is the third bass trap in area C necessary? Where else should I add some. They will be 2ft. wide, 6 inches deep and go from floor to ceiling and might have an extra 12 inch wide 4 inch deep piece added behind.




The view from my desk and main listening spot.



View from behind the plasma TV.



This was the corner bass-trap design I was going to build but decided against it in favor of making it a 2 piece stand.




And here is a design I was going to stencil on with spray paint.

[Rob Babcock]

Your bibliography is certainly impressive!   But that's the way to do it- find good resources and dive in.  Bass trapping in corners and in the floor/wall and wall/ceiling boundries is a good place to start.  I don't know what that tool is for the iPod, but it's helpful to have some type of instrumentation to measure what you're doing.

[bpape]

I don't know what the previous arrangement was but the current one has a few issues that need to be addressed.

- Lack of left to right symmetry will cause the right speaker to have a different tonal balance and reflection signature than the left one.

- With an OB design, the glass behind the speakers can be a very hard,  harsh sounding surface.  Some absorption/diffusion in front of it would help.

The absorber in area C wont hurt anything certainly.  That said, if you have a finite amount of absorbing material for bass control, I'd likely concentrate on the wall behind the desk and listening area (E).

Bryan

[Big Red Machine]

You are sitting in a tunnel at that desk spot and you can see that the reflections are probably overwhelming the direct sound.  Does it sound better at the couch in front of the desk?  Can you slide the desk up to that spot?  Dimensionally it is not far from my room in size, and I would expect you can master this more with seating placement than sound treatments first.

[laserman]

Why do you still have plastic on the acoustic panels?  IIRC, that will cause the higher frequencies to be reflected instead of passing through the panels.

Rob, Bryan and Pete comments are dead on.  I know Bryan and Pete each have many years of experience under their belts – Bryan as a manufacturer and installer, and Pete as your typical enthusiastic neurotic audiophile looking to squeeze out the best from his system.  Lol

From my experiences (Maggie owner), it became an experiment of placement and patience.  To add to what they said and IIWY, I would also look to add a 2” thick panel with a 2” air gap on the ceiling at the first reflection area.   As Bryan pointed out, the left side needs some special attention.  You may want to have a portable/moveable 4-6” 2’X4” panel to drop in place when you want to listen critically.  The window on the right side may need some attention too.  If you want the light, then instead of thick drapes look into Plantation Shutters with 3” or 4” slats so you can direct the reflection up or down to your listening pleasure.

Remember no two rooms are alike and it just takes experimenting.   

Good luck with your journey.
Lou

[Voncarlos]

Hi, thanks for the comments and info.
The plastic is still on the panels because there's only so much time in the day and while I'm playing with temporary panel placement I don't want to have fiberglass dust all over the room. I just finished one 1st reflection panel today. I am so amazed at what these panels do, that I now want to invest in some measuring equipment to have data to follow.
I think these dipole/box speakers are a different ball of wax and I'm noticing that the bass traps at the front wall are collapsing the soundstage and I have made their angle more shallow to help with that.
I do plan on making some 1st reflection panels on stands so I can move them around.
The French door behind the plasma and the window to the right are covered in double-cell blinds.
I have redrawn the listening spot on the 2D drawing to show it a little more forward from the previous drawing.
And a stitch together photo to show a little more realistic wide view.






Thanks,
Carlos
 

[Voncarlos]

I bought the Radio Shack Sound Level Meter and ran the RealTraps Test Tone CD. Here is the graph profile.
After I plotted this I walked around the room with the RS meter and found the 30hz-40hz and 100hz peaks @ >90+dB along the front wall to ceiling area and the south end of the soffit to ceiling and also the wall/ceiling corner in area C above the bass trap.

I have a PCI SoundBlaster X-Fi sound card in my PC that has a Line in/Mic in (1/8-inch) plug. Can I run Room EQ Wizard with this sound card and RS meter?

[bpape]

As long as the sound card is bi-directional (can play and record at the same time) you can run REW with no problem.

Bryan

[Ethan Winer]

The SoundBlaster X-Fi is bi-directional, though its software control panel can be confusing to configure. Key is setting the record input to come from the physical Line In jack only.

--Ethan

[Voncarlos]

Thank you to everyone and especially to Ethan for making his knowledge and info available online for diy'ers. It's actually fun to see the changes on the "graph/testCD plot as I move the traps around. Can't wait to get the "Room EQ Wizard up and running.
Thanks Again,
Carlos 

[Ethan Winer]

It's actually fun to see the changes on the "graph/testCD plot as I move the traps around.

You can even do that in real time with REW. I wrote up the procedure for an article I plan to put on the RealTraps site very soon. In the mean time, the relevant section is copied below.

--Ethan


It takes REW only ten seconds to do a sweep and show the results, but it's still tedious to move a speaker or bass trap a few inches, measure, display, and repeat. Going back and forth constantly between handling the speaker or bass trap and working your computer gets old very fast. And you have to keep deleting all the intermediate measurements. So to speed up the process I created a small (180 kb) Wave file that contains a sweep ranging from 20 to 400 Hz:

20 to 400 Hz Sweep Tone

Download this file to your computer, then set it to play continuously in Windows Media Player, or any other program that "plays nice" with Windows sound drivers and shares your sound card with other programs. Then switch to REW's Spectrum display (tab) as shown in Figure 5 to view the Real Time Analyzer (RTA).



Figure 5: In the REW Spectrum tab, the red Record button at the lower right
puts REW into its RTA mode and updates the screen continuously.

Set all of the RTA parameters as shown in Figure 5 to get the highest resolution, then click the Record button to enable the RTA display. Next, start the sweep playing in your media player program with the volume fairly loud in the room. Adjust the microphone preamp level until you can see the frequency response graph line on the screen. (You may also need to adjust the Graph Limits dB range to see the entire response line on the screen.) Now you can experiment with speaker placement, or microphone placement, or bass trap locations, and see the result of your changes immediately. Pretty cool!

[Voncarlos]

I've finished building my acoustic absorption panels in various thicknesses from 3" to 6" and I'm quite happy with the improvement in sound and the way they look. I've probably picked the worst sitting location to listen to my system but the acoustic panels have really-really tamed down the over-dominant bass and equaled the soundstage from left to right. These panels have made just as much improvement to the system as adding or replacing a top $$$ component.
To anyone thinking about or hesitant to add acoustic panels, I say, "go ahead"! You will be amazed at the improvement in sound.

Here's the result and how I got there.




I built the panel frames out of OSB (oriented strand board). It accepts staples and screws readily into it's face but not into it's sides. So I added a screw & glue corner post of pine to hold the corners together. The rigid fiberglass sheets come in 2"x2'x4' so it's the inside measurement of the frame to go by.




Here are three 4" panels that will hold two 2"x2'x4' sheets each. So each one of these panels would be considered a 4" acoustic absorption panel.




After the frames are assembled I sanded and rounded the edges with a disc sander. This will keep the burlap from snagging on them and allows it to stretch easier. I laid the frame on the cut burlap and before stretching and stapling I insert one 2" sheet of rigid fiberglass to keep the frame square and keep the sides from pulling in as you stretch the burlap.




On the back side of the panel I tucked in a very shear poly fabric to keep any loose fiberglass from wondering. It doesn't look very shear in the picture but it is. If you look at the top of the picture between the yellow drill and red burlap you can see where there is a piece of shear poly fabric folded over several times, and you can still see through it. You want this piece of fabric to be as acoustically transparent as possible.
The picture below is one panel for the "cloud" ceiling absorption. It doesn't have the hangers at this point because I was still adjusting their temporary placement.



A finished 3" frame filled with a 2" rigid fiberglass panel.




To make the hangers for the cloud, I used 2' cut pieces of wide-flange stucco J-channel. I read this idea from one of the other websites, I think it might have been from an article by Ethan Winer or from his company's website. Someone correct me on this please. Anyway it's a great idea! The stucco J-channel comes 10' long and that allows me to cut five 2' pieces but doesn't allow for bending side tabs to attach it to the frame. So I just cut small tabs from some HVAC sheet metal I have laying around and used sheet metal self-tapping screws to attach.





Here's a close up shot of that. Something I didn't think of at the time, was to leave some OSB material where the tabs connect.
In the end it didn't matter because adding the rigid fiberglass prevents the hanger from twisting.



Hangers in place.








Here is the panel hung in place with some simple screw hooks.
The J-channel allows for side to side adjustment and the metal is thin enough to allow for small fore and aft adjustment as well.



I think they look nice.





And finally, a photo-stitch of the room showing most of the panels.



There are 17 panels . . . so far.
The corners start with a 1' wide x 4" deep piece from floor to ceiling that is uncovered.
In front of that is a 6"x2'x floor to ceiling panel that has a reflective face.
In front of that, on the floor is another 6"x2'x4' panel and on top of that is a 4"x2'x4' panel.

The Cloud is three 4"x2'x4' panels and the two outside panels have a reflective covering(SFK).

All first point panels are single 2"x2'x4' and spaced off the wall by a few inches.

There is also a 6" panel to the right corner out of picture and a 2"x2'x4' panel on the back wall behind the listening spot.

With two of the panels I used Rockwool instead of rigid fiberglass because I had some left over from home remodeling. I would recommend not using Rockwool because it is heavy, flimsy and makes a mess.

Plan on using a lot of staples. For these 17 panels I think I've gone through 5000.

Carlos

[Ethan Winer]

Wow Carlos, that's truly fabulous!

--Ethan

[poseidonsvoice]

People don't realize this but Carlos is an expert builder and finisher. His work is nothing short of amazing on his OB-5 speakers.

Great work as usual Carlos, you've raised the bar, once again.

Anand.

[Big Red Machine]

 

[MaxCast]

Very very nice, Carlos.

[TomW16]

Very cool how you designed and implemented the cloud absorbers on the ceiling.   

[Voncarlos]

To everyone, thank you for your kind comments.
I will probably take down the small corner triangle up by the soffit and install a full panel to run the full 4' length of soffit, I put a temporary one there and could hear an improvement. It was just time to put the panel building aside and move on to other projects.
Thanks Again,

Carlos

[saisunil]

Amazing!
Would love to see before and after frequency plots ...
 
Thanks