[arthurs]

Brian (brj), I'm not sure if you would absolutely have to have them fixed to a base if you have batting or insulation wrapped around them for spacing, enough to make it snug inside.  The 1.5" wall thickness in the 16 and 22" are pretty sturdy and don't move much even when given a good knock, the 9" may be another story, but I don't plan on them being moved around much once they're dialed in....looks like a long weekend ahead with all this information floating around for us to test out, wear long sleeves and bring your work gloves....

[brj]

I'm not sure if you would absolutely have to have them fixed to a base if you have batting or insulation wrapped around them for spacing, enough to make it snug inside.  The 1.5" wall thickness in the 16 and 22" are pretty sturdy and don't move much even when given a good knock, the 9" may be another story, but I don't plan on them being moved around much once they're dialed in....

I was mostly thinking about having them anchored while stuffing them.  I'm guessing that as you try to stuff one side, the interior tubes will move to the other, etc..  Having the tubes liquid nailed to a simple piece of MDF would probably make this easier.  I'm sure we can make it work either way, however.

looks like a long weekend ahead with all this information floating around for us to test out, wear long sleeves and bring your work gloves....

I think I'd better pick up another pair, as my current ones have perforated backs for ventilation - perfect places for fiberglass to penetrate and drive me nuts for days!

[Daygloworange]

Guys,

I commend you on your efforts, and for sharing your findings. Thanks! 

Cheers

[bpape]

Definitely pull the facing off the inner pieces.  

The reason the 703 works somewhat better is that it (IMO) the denser material does a couple of things:

- It can actually vibrate like a drum head pushing and reflect some of the waves back into the room.
- At shallow angles of attack, higher frequencies can actually skip off like a rock on water
- The gaps in the material compared to the wavelengths we're speaking of can be too resistive and not really let the sound get in easily to be absorbed.

You can acutally look at 701 and see that to a point, it does even better yet.  But, it loses it's advantage much higher in the spectrum and isn't nearly as rigid for structural strength, wrapping, etc.  703 is kind of the happy medium for performance for the dollar.

Now, with mineral wool, the structure is a bit different and not NEARLY as uniform as spun fiberglass.  8lb density can be used very effectively and still provide good HF absorbtion while a 4" thickness is as good or better than 703 - but 703 is MUCH easier to work with.  For reflection points, stick with 2.5 or 4.5lb density.  If you're going solid or thicker on bass absorbers, use 4.5lb.

Bryan

[arthurs]

anyone who wants to volunteer to come by and help Brian and I stuff and move tubes around for measurements this weekend, make yourself known....I'll let you bring the beer...

[brj]

And after that, the inside of my house could use a coat of paint!  Heck, I'd even supply the beer for that... after the painting was done, of course! 

[Ethan Winer]

Guys,

I'm swamped so I'll be brief with just a few comments:

50Hz wavelength is approximately 10 feet so to have a trap centered and filtering at that would require one that is approximately 30" in diameter.

My Frequency / Distance Calculator says 22'7" but your logic is impeccable.

At double the density, the 705 doesn't seem to do a heck of a lot more compared to the 703, in fact, it seems to do less at times in the low frequency region. Or am I reading something wrong?

Take all such data with a large grain of salt. Labs tests vary by 50 percent at 125 Hz, and even more below that. Not that standard data goes much below that anyway. See this:

www.ethanwiner.com/density/density.html

--Ethan

[bpape]

You're correct Ethan - had the halfwave in my head for some reason.  So, at 22' approx, the quarter wave would be about 5'.

Bryan

[marvda1]

had a great time art, but it's nice to get back to listening to music after 6+ hours of sweep tones
marvin

[arthurs]

It was a long, but interesting, day Marvin, thanks for your help....

It was also nice seeing the Cowboys lose....

Brian, Marvin and I are going to collect our thoughts on the great pipe cover experiment (so far) and post something in the next couple of days....

[zybar]

It was a long, but interesting, day Marvin, thanks for your help....

It was also nice seeing the Cowboys lose....

Brian, Marvin and I are going to collect our thoughts on the great pipe cover experiment (so far) and post something in the next couple of days....

Acoutics isn't a lot of fun, but I am sure that was time well spent.

Looking forward to hearing about the results.

George

[arthurs]

It was time very well spent, but a real pain to be sure...and as Marvin said, 6 hours of sweep tones gets a little tedious after about an hour   

We made some real strides with the room though, which is good...

and I'll say it again, it's two pretty good friends who would spend that kind of time and hassle helping a buddy out...thanks Marvin and Brian!