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PostPosted: Tue Jul 02, 2019 2:24 am 
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Location: Santiago, Chile
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I haven't been on the forum for a bit - for a good reason: I've been building the left and right speaker soffits
Nice! They are looking very "beefy", which is good! You want them tough and rigid.

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* Would Roxul 3" safe-n-sound work too in places, or must it all be OC 703?
Yep, that should be fine. The specs are reasonably similar.

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I need to download REW soon and start the learning curve. I expect it will be necessary to buy a suitable mic. I need to research that.
Not sure if you've seen this thread, but I cover mic selection, and also sound level meter selection: How to calibrate and use REW to test and tune your room acoustics

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Here's a photo of the soffit progress. I haven't framed in the spaces between yet.
What's your plans for mounting the speaker itself?


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PostPosted: Thu Jul 11, 2019 11:52 am 
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Location: Salem, Oregon, USA
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Not sure if you've seen this thread, but I cover mic selection, and also sound level meter selection: How to calibrate and use REW to test and tune your room acoustics

Yes, I have the link and will soon be digging in. Thanks! So glad to have this to start out with, since I am soon to enter into the "scary" acoustics phase, being green on this.
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What's your plans for mounting the speaker itself?

It's funny you should ask! I've been building the speaker mounts and just finished the assemblies yesterday.
You may recall we talked about that at length quite a while back and I've had the design ready to go since a year ago. This should refresh your memory:
Here is the drawing of the assembly, using plywood and sorbothane pads. There are T-nuts embedded on the right and left assemblies in order to "dial" in the compression with the bolt:
Attachment:
Spkr_suspension_10Jul2019_A.jpg

It is attached to the soffit shelf like this (speaker missing for viewing):
Attachment:
Spkr_suspension_10Jul2019_B.jpg

With speaker:
Attachment:
Spkr_suspension_10Jul2019_C.jpg

...and here's the real deal as of last night (on kitchen counter on blocks):
Attachment:
20190709_221852.jpg

I used nylock nuts with washers and found that I needed to put them on both sides of the top and bottom pieces to keep things straight and inline. The amount of compression on the top verses the bottom sorbothane hemispheres (different quantities and sizes) worked out nicely with the specified range of 20 to 30% compression. I was very pleased. Dialing it in was a bit tedious, but not hard.
After a couple of calls to the engineer at Sorbothane a year ago, I had selected a combination of two sizes that put me in the right ballpark. For below the speaker, I had to take into account the weight of the speaker and the expected pressure from the top absorber. It turned out to require five smaller pads to work out. The sides are the same as the top. It was neat to see that the compression ratios of top and bottom actually worked out as expected.


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PostPosted: Thu Jul 11, 2019 3:56 pm 
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Looks like it should work! :thu: That's not exactly the way I do it, but not far off...

Have you tested it yet? Play loud music, with plenty of low bass content, and check the wood panels for vibration, with your fingertips.

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PostPosted: Fri Jul 12, 2019 12:24 am 
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Looks like it should work! :thu: That's not exactly the way I do it, but not far off...

I borrowed from barefoot's design and used threaded rods and bolts rather than a strap to hold things down. I liked his idea because it lends itself pretty good to make it easier to replace the speakers some day down the road without tearing the whole front end out of the control room.
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Play loud music, with plenty of low bass content, and check the wood panels for vibration, with your fingertips.

Good idea. I will do that.

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PostPosted: Sat Sep 07, 2019 3:36 pm 
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Hi Stuart,
I have a partner who is going to work with me and get through the learning curve on REW. Right out of the chute, we're not understanding how to even hook up the loopback to calibrate. I feel really stupid for asking, :oops: but after a couple of hours of reading through both your instructions and REW help files, we are really confused:
For a typical calibration in my 2-channel system (no sub), would I hook up TWO cables from speaker output L & R to input 1 & 2? You're probably going to roll your eyes over this! :roll:

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PostPosted: Sun Sep 08, 2019 1:26 am 
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For the soundcard calibration, you hook up a simple cable that goes from either the left speaker output OR the right speaker output of your sound card, directly back in to the line input channel of your sound card (where you will connect the mic later). That's all!

This is not applicable if you use a USB mic: only if you use a proper audio interlace device (what the REW manual calls a "soundcard").

Also, do check that you have the latest version of REW installed: the current version is 5.20 Beta 23.

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PostPosted: Sun Sep 08, 2019 2:27 pm 
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Thanks Stuart! I have my elderly Dad's funeral to arrange this week and then we will go to work on it. I really appreciate your quick response. :)

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PostPosted: Fri Oct 18, 2019 5:06 pm 
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Care to share the calculations you did for the Sorbothane pads?

Greg

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PostPosted: Mon Nov 18, 2019 2:37 pm 
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Greg,
My profuse apologies. My world has been hectic between work, family matters, keeping the home running and ..... then there's the studio! I have been out of the country for a while too. I didn't get onto the forum until now. The good news is, we figured out how to ring the control room for the first time and also built a pedestal in the back of the control room that will raise up the rear couch a ways. More on that later.

Quote:
Care to share the calculations you did for the Sorbothane pads?

To answer your question, I retraced my steps on that, since I seem to have lost my notes.
My speakers weigh 29 lb, 13oz (15.5kg), so let's say 30 lbs each.
Here is the 2018 product guide from Sorbothane: https://www.sorbothane.com/Data/Sites/3 ... ne-SPG.pdf
I was advised by Sorbothane to use hemispheres. He apparently gets a fair amount of speaker isolation calls. If I recall, I think he recommended a "duro" value of 30.
I realized that for the bottom pads, I will have to account for the weight of the speaker as well as the downward weight of the top pad.
For the top and sides, I chose part number 0510150-30-10, which has a diameter of 2.5", height of 1.25" and a load range of 25 to 35 lbs.
Adding the 30-lb speaker weight and the mid-range top pad pressure (also 30 lbs) I realized I had to find an array of bottom pads that would be within range with 60 lbs. That worked out by using five of part number 0510141-30-10. Each pad has a load range of 11 to 16 lbs. Dividing 60 lbs by four pads yields 15 lbs (near the top of the range), so I used five pads, which puts it at 12 lbs each (on the lower side of the range).
In the real application, I found that the compression worked out pretty nicely. I was prepared to remove one pad if the compression on the top and bottom weren't both near 20 to 30%, but it didn't turn out to be a big deal.
The side pads are the same as the top. It was a no-brainer - just dial in the amount of compression.
All of the hemisphere pads cost me $67.90 with a couple of each size extra. They only came in 4-packs.
Hope this is useful info. I ain't no expert, you know! :wink:

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PostPosted: Mon Nov 18, 2019 5:27 pm 
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That all makes sense to me! Thanks so much for sharing.

I really look forward to your couch riser posts!

Greg

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PostPosted: Wed Nov 20, 2019 3:21 pm 
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Here's the details of the couch pedestal:
Attachment:
20191001_211130.jpg

We used 2x10 pressure treated lumber. First, we cut and assembled the outer circumference and anchored it to the concrete floor. Next we sealed all around the inside, between the joints and along the floor with silicone seal. Next we spread a visquine plastic sheet. Lastly, the middle cross pieces were put in. We cut two pieces of 3/4" plywood to fit, but did not attach yet. At this point, I took opportunity to have the floor installed. Now all the flooring is installed in the entire studio.
Attachment:
20191104_185557.jpg

I enlisted a few energetic youth who are waiting anxiously for a recording studio (all are excellent musicians - one with a degree in music). We took a bunch of junk bricks and cinder blocks to fill in as much as possible. Then ...
Attachment:
20191111_201110.jpg

... filled it with medium grade (dry) sand and ...
Attachment:
20191116_151410.jpg

,,, screwed the lid down. The front will be lined with MDF and the top will be covered with a short-pyle commercial carpet remnant, I expect. It will be covered by the couch except a little on the sides. Everything behind the couch will be bass trap, of course.
Attachment:
20191009_220322.jpg
Here's another angle through the sound room window. Now I need to draw the details of the back bass trap and hangers. Then I can order the homosote and the 2" fiberglass OC703 for both the front and back of the control room.


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PostPosted: Wed Nov 20, 2019 3:29 pm 
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Oh, I almost forgot. I added a little detail to the flooring you might think is novel:
Attachment:
20191009_220358.jpg
Take a close look at this picture of the flooring. It is directly in front of the pedestal. You can see two round inlays - one at the top of the pic and another below. They mark the focus point of the speaker and the sweet spot. I got some free samples flooring pieces of the same style, but different color, from Home Depot. I carefully embedded these into the floor for a permanent mark of these important points. I had to practice a few times with scrap pieces before we installed the floor.


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PostPosted: Sat Nov 23, 2019 6:47 am 
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Awesome stuff!!!! Keep us posted please!

Greg

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PostPosted: Thu Nov 28, 2019 5:00 pm 
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I got started drawing the back bass trap for the control room. The most difficult part right now is getting around the slope of the ceiling. It drops about 10 inches in 2 1/2 feet. Since I have a corner control room configuration, that causes a weird angle on my ceiling, which is unsymmetrical. I knew it would come back and haunt me and now I'm facing it. This is what I came up with:
Attachment:
Rear_Trap_A.jpg

I added a black line where the ceiling takes the downturn. Here's a more-vertical view to get a better picture:
Attachment:
Rear_Trap_B.jpg

So, you see that I have resorted to turning the hangers 45 degrees to accommodate the ceiling angle. I saw someone else did the same thing on the forum (for difference reasons), but can't find it now. Is this crazy? Will it impede the bass trap by such a steep angle with respect to the speakers? If so, I'm going to have to get very creative, putting weird-shaped tops to the hangers and then figure a way to hang them straight from a slanting rod overhead.
What think ye?
-Ron


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PostPosted: Thu Nov 28, 2019 7:55 pm 
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why not try something different and more effective.

Attachment:
Corner_1.JPG


This is the math.

Attachment:
excel_1.JPG


Vertical slots are more effective at absorbing low end and they diffuse the high end

here's them in action.

https://www.johnlsayers.com/Pages/Image ... trol_1.jpg

and in this corner control room.

https://www.johnlsayers.com/Pages/Image ... r_slot.JPG



cheers
john


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