Fiberglass question

davejcb · « **on:** 8 Jul 2004, 04:11 am »

Still trying to source some fiberglass here, most places have a minimum on special orders (6lb/ft3). I've found a local outfit that carries 8 lbs/ft3[/b] panels!

Here are the 6lbs/ft3 panel specs.

Here are the 8lbs/ft3 panel specs.

I'm basically wondering if going over 705-FRK density is overboard, as I haven't seen any mention of it being used. Seems like 4" of 8lbs/ft3 with FRK in the corners would give really good low bass absorbtion, any drawbacks?

Thanks!

Ethan Winer · « **Reply #1 on:** 8 Jul 2004, 03:08 pm »

Dave,

> I'm basically wondering if going over 705-FRK density is overboard <

No, that 8 pound stuff is fine. Go for it.

--Ethan

davejcb · « **Reply #2 on:** 9 Jul 2004, 04:47 pm »

So many choices!

1 - 3lbs/ft3 2" FSK, able to double it up to 4"
2 - 8lbs/ft3 4" plain, of this stuff
3 - 8lbs/ft3 4" FSK, of this sutff

The saleslady at Roxul basically told me anything in the regular RXL fiberglass (same as Owens 703/705) had a 100 bag minumum with FSK, but that 3rd fiberglass didn't, but she didn't know the difference of it from the RXL-80. Waiting for a call from a tech guy to answer.

Ethan, can you see anything wrong with that 3rd fiberglass? Seems like I could order any amount in 8lbs/ft3 4" FSK, be nice. Which would you pick?

Thanks!

davejcb · « **Reply #3 on:** 9 Jul 2004, 05:02 pm »

Just spoke to the tech guy, said the only difference was in the "nominal" density, that the RHT actually came in at ~5.9lbs/ft3.

Oh, and one more thing - he mentionned they sell rockwool, not fiberglass. What is the difference?

So would you double up on 703, go plain 4" 8lbs, or FSK 4" ~6lbs? Seems like that 3rd one would work out to be similar to 705-FRK?

ooheadsoo · « **Reply #4 on:** 9 Jul 2004, 07:51 pm »

I hope you don't mind my hopping in your thread. I was wondering if it was worth it to buy the 6pcf stuff. It costs twice as much, after all.

davejcb · « **Reply #5 on:** 9 Jul 2004, 08:05 pm »

If it's literally twice as much then I wouldn't think so, if you look at the absorption coefficients of 703 vs. 705 (6lbs/ft3), 705 isn't that much better than 703.

ooheadsoo · « **Reply #6 on:** 9 Jul 2004, 08:07 pm »

Yeah I know...the key is that last 125hz value

I actually have a big peak there at 120-160hz that I'm currently correcting with equalization.

Ethan Winer · « **Reply #7 on:** 10 Jul 2004, 01:04 pm »

Dave,

> can you see anything wrong with that 3rd fiberglass? <

Nope, go for it. And your choice of 4 inches thick is perfect.

> they sell rockwool, not fiberglass. What is the difference? <

One is made from glass fibers and the other from ground up rocks. Or something close to that. In practice they do the same thing.

As for 3 pcf versus 6 pcf, this has been hotly debated lately. The short answer is that data reported as octave bands (too coarse) and no lower than 125 Hz (not low enough) hides the difference, which is all below 125 Hz. Tests I paid for in a real lab showed that 705 is as much as 40% better than 703 below 125 Hz.

--Ethan

davejcb · « **Reply #8 on:** 10 Jul 2004, 08:41 pm »

I had a feeling there was more to it than > 125hz... Thanks Ethan!

ooheadsoo · « **Reply #9 on:** 10 Jul 2004, 08:53 pm »

Too bad I already bought the 3lb stuff. Oh well, saved me money, which I don't have a lot of...I have to buy it in bulk around these parts and money is tight

davejcb · « **Reply #10 on:** 10 Jul 2004, 09:02 pm »

If you wouldn't mind, would you post results once you've trapped your corners?

Thanks!

ooheadsoo · « **Reply #11 on:** 10 Jul 2004, 09:18 pm »

Actually, the person responsible for decor would throw a fit if I trapped the corners. Right now, I'm focusing on handling reflections. Any bass trapping I get is incidental

If you see the picture of my system, you can see I'm flush up against the front and left wall. I haven't framed anything up yet but I set the panels roughly into place. The clap test difference is quite large. Lots of ringing on the other side of my room hehe. Obviously the room could use more treating that I can't afford (pain in the wallet and pain from *ahem*.)

Imaging has definitely cleared up. I'm loving it. Instruments are coming through clearer in focus and location than before. I fancy hearing some depth now. There was never much to speak of before the panels. They would sound like they're supposed to be farther back but...they weren't. I haven't listened to all my problematic imaging music yet mostly because I never wrote down which ones they were, but I haven't really had much confusion over where an instrument was placed yet. If cables rated a 5 on a scale of 1-10 on the level of change a tweak gives you, this would definitely rate a 10 in my book. The change in the clap test, at least, is blatantly obvious. No one could miss that.

As for bass, I can't really speak on that subject because I've been tweaking my subwoofer lately in the last couple of days. I don't know if I can contribute the current bass I'm hearing to the panels or my tweaking.

davejcb · « **Reply #12 on:** 11 Jul 2004, 12:21 am »

Any pictures of the panel mounting?

ooheadsoo · « **Reply #13 on:** 11 Jul 2004, 12:23 am »

Did you mean the finished panel or construction pics? I've only finished one panel so far, took me about 70 minutes not counting interruptions. I guess I don't work very fast when it comes to these kind of things

Actually, I haven't figured out my mounting method yet since I haven't decided for sure where I will place them exactly.

What I have so far:
Left is an unfinished panel with a light brown/beige burlap draped over it.
Center is the finished panel unmounted.
Right is a raw panel.

davejcb · « **Reply #14 on:** 11 Jul 2004, 01:21 am »

How far back are you listening in that setup? Seems like a small place...

ooheadsoo · « **Reply #15 on:** 11 Jul 2004, 01:36 am »

Nearfield - about 3-4 feet. The room is medium sized, I'm just stuck in the corner. There's no way I can seriously rearrange things at the moment.

Rob Babcock · « **Reply #16 on:** 11 Jul 2004, 01:44 am »

Jeez, I'd cover that raw panel!

Glass is not only itchy & uncomforable if it contacts your skin, it's a serious health hazzard if it's inhaled. And it can shed.

ooheadsoo · « **Reply #17 on:** 11 Jul 2004, 01:46 am »

I worked with fiberglass a lot in high school a long time ago. It's not that bad

Hehe, yeah, it's covered now anyway. I think I'll post my construction pics in a separate thread. I call them the "Ghetto Panels."