Am I on the right track -� Is Knauf 3.0 PCF Insulation Board correct ???

[john4618]

Ive been reading and reading about room treatments and heres what Im going to do to start:

1. Put one 12 diameter by 3 foot high bass trap behind each of my front RF-7s. (The traps will be DIY per Jon Risch and Adam Salisbury plans.)

2. Put one 12 diameter by 3 foot high bass trap in each rear wall corner.

3. Centered on front wall, put one 1 x 2 x 4 sheet of Knauf 3.0 PCF FSK Insulation Board mounted directly to wall. (covered with burlap or Guilford acoustical cloth)

4. Centered on rear wall, put one 1 x 2 x 4 sheet of Knauf 3.0 PCF FSK Insulation Board mounted directly to wall.

5. At RC-7 reflection point on ceiling, put one 1 x 2 x 4 sheet of Knauf 3.0 PCF FSK Insulation Board mounted directly to wall.

6. My room is L-shaped so I have no left side front wall, but at the RF-7 reflection point on the right side front wall, put one 1 x 2 x 4 sheet of Knauf 3.0 PCF FSK Insulation Board

Am I on the right track to start - and then experiment from this point on ???

Critical Question: Is the 1 thick x 2 x 4 Knauf 3.0 PCF FSK Insulation Board the correct board to get ??? The coefficients are: 125=.21, 250=.63, 500=.84, 1000=.93, 2000=.51, 4000=.22. Where I live it is impossible to buy any kind/brand of rigid fiberglass insulation board, but I found a Knauf dealer that will ship it to me so I want to be absolutely sure that I order the proper board.

Any help and guidance is appreciated.

[michael hurd]

Without knowing what the deficiencies are in the room to start, it is kind of hard to make a game plan. I am in the same boat as well, as I do not have a real time analyzer and calibrated mic. To start, adding absorption in the vertical corners is a good thing. Also treating the first reflection points are a good thing. The key is to address broadband absorption and also have diffusion to breakup standing waves.

To answer your other question, the 1" thick board is a poor choice in the fact that it is too thin to be of any use in the low frequencies, unless you have a whole bundle in the corners. Also, it's absorption co-efficients are not that uniform, meaning it will absorb 1khz a lot better than 4 khz or 250 hz.

Not to get you down, it would work better than no treatment, but I would check around some more. I purchased a bundle ( 32 sq ft ) of 4" thick Roxul rxl 40 rock wool insulation for $ 40 cdn, and to treat the lowest freqencies, I would even have to stack it thick ( 2-3 layers ) in the corners.

http://www.roxul.com/graphics/rx-na/canada/products/rxl_board/rxl40.pdf

As you can see, the roxul product has a more uniform absorbtion across the same test frequencies.

I had my sister, who is a seamstress and owns a costume shop, sew me up some covers out of a polyester stretch knit. I then proceeded to roll and stretch these thin covers over the insulation to contain any loose fibres and also make them look a little better. The edges look a little wavy, so I may have to make a frame for the outside, to look a little more professional.

[michael hurd]

On the roxul website, they have a U.S. section and also a "where to buy" page. All you need to do is to fill out a little information, and they will e-mail you with addresses and ph #'s of the resellers nearest you.

Owens corning makes a similar, comparable product, but you would have to sell your first born, as they are much more expensive. I purchased the Roxul product from a high volume industrial supplier, rather than a small hardware or retail store. You may also check near you at an industrial / commercial place. Hope this helps!

[john4618]

What size are the covers your sister made for you ???

And you're using them how/where - you hung them on the walls and/or the corners ???

What about your ceiling ???

And I'm guessing they are working well for you ???

[michael hurd]

The covers are 2 feet by 4 feet, sewn into a pocket 4" thick, like a pillow case. The other end is hand sewn shut, stretching the polyester and sewing ( requires 2 sets of hands ). I have the exact measurements here, it was a trial and error to get enough tension on the material to eliminate future sag. The third cover was the best fit.

I will be hanging up the other panels soon, I really wish that I had a digital camera. As of right now, I have to take a regular picture and then have a cd made when they are developed, so I can post them.

I am hanging them vertically in the corners, with another one at the wall/ceiling junction at the front of the room.

[michael hurd]

To make a slipcover for a single 4" thick 2 foot X 4 foot panel, you need 1 1/2 meters of material. I used 100% polyester knit, that is similar to the grill cloth on the reference series speakers. It tends to stretch in one direction a little more than the other, so keep that in mind.

The normal width of fabric bolts here is 150 cm ( 60 in ). The smallest width that you could use for a cover is 115 cm ( 44 -45 in ). Measurements that we arrived at through trial and error were 58 1/2" X 44". The dimentions are purposly on the small side, so that the covers are tight, with no extra fabric. ( My sister explained that they will stretch slightly, and possibly loosen )

The covers were sewn with a serger, which simultaneously cuts and sews a 5 thread locking stitch.

Order of assembly as follows -

1. Sew side seam only cutting off 1/4"

2. Sew seam that will form one end of the cover

3. 45 degree corner cut, @ 3 1/2" drawing line ( serger cuts extra, so this marked line ends up to be 3 3/4" - 4"

4. Stretch the cover, and very carefully roll and work it down over the insulation.

5. Stretch all slack to open end, then hand sew seam closed ( requires 4 hands )

[michael hurd]

Normal pricing for the material I purchased is $ 9.99 cdn/m, however I just happened by when there was a 50% off sale, so I paid $ 4.98/m. My sister, who is an employee of the fabric store, buys for a whole lot less than even I did.

If you can get some er, umm... slave labour, then you can build covers for less than $ 10 cdn each. Of course, it's family, so i'll pay sooner or later.

[john4618]

Thanks Michael - I'm now understanding better the need for more uniform co-efficients at all frequencies. Unfortunately, since these panels are going into my living room I cant use 4 thick, so Im going to review the co-efficients of the Knauf 2 panels tonight to see if they are more uniform.

Another possible option is hiring Rives Audio. They claim to be able to get your room acoustically near-perfect without huge panels and such in the room (it will still look like a living room, not a sound studio with huge panels everywhere) but this is at a price of $900 for their designing and engineering plans, and then I would do the actual work in the living room myself has anyone used Rives design services ??? Is it worth the $900 cost ???

[michael hurd]

You can check out options and get professional consulting free. Check out www.auralex.com. They have a form that you fill out and fax in, then they will give you free advise. Then it is up to you as to what options and avenues you take.

[john4618]

Thanks Michael - I just filled out and faxed the room analysis forms to Auralex, so I'm looking forward to see what they come up with.