# Need more bass trapping? Waterfall graph and pics inside



## jlird808 (Nov 2, 2010)

I hate posting vague acoustic questions like this but I'm a lil concerned about the low end in my L shaped room.









I do have about 6" of rigid fiberglass in the corners behind my daw about 4.5' tall (the white panels in the below pic with the auralex wedges sitting on top)










Here's my room and panel layout layout. It's 16ft from the wall behind my daw to the wall behind me. My ceilings are 11' high! I have a large 3" thick cloud hanging over my head thats lowered about a foot off the ceiling. That is NOT bass trapping behind the TV.









Any recommendations? Sometimes I wish I'd built superchunks instead. I thought the fat sofa in the middle of the room with the lowered cloud would absorb some low end too.

Thanks!


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## Wayne A. Pflughaupt (Apr 13, 2006)

Hi jlird,

Waterfall graphs are only useful for the bass frequencies, about 300 Hz and under. 

The best way to tell if your bass traps are making any improvement in low frequency decay times is to take “before and after” readings – i.e. a baseline with no traps in the room, and a second measurement after they have been installed. It’s best to do this during the same REW session, unless you’re sure you can take the “after” reading later with the same calibration levels as the first. It helps to know at what frequencies the traps are supposed to be effective; hopefully the manufacturer gave you some kind of information on that. IIR they don’t effect below ~60 Hz, and even that takes a lot and/or very large traps.

Regards,
Wayne


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## jlird808 (Nov 2, 2010)

Thanks!!

Here's the revised waterfall. From other waterfalls Ive seen I think this is pretty bad at some freq right? 300ms is the appropriate decay time setting I'm assuming.








I have ppl coming over to track in a lil bit so I cant go moving around acoustic panels just now but I will definitely try that!

So really, rigid fiberglass bass trapping doesnt affect much below 60hz? My panels were constructed, supposedly by a company that ripped off Owens Corning's recipe lol and then got shut down. Ive sold/given some away to some studio veterans and two of them told me it was equivalent with OC705. One guy said to weigh a panel and then I could tell if it was closer to 703 or 705 but I havent done it yet (theyre in storage). In other words, Im not sure what freq theyre supposed to be effective unfortunately :dontknow:

Thanks for the info and I'll update later!!


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## paulspencer (May 11, 2007)

You can get a good result from rigid fibreglass well below 60 Hz. In fact even with foam if big enough. Looking at your waterfall I would say there is a fair amount of improvement possible. You could put another big trap where you have a bookshelf as well as a bulkhead trap. I've noticed with foam and rigid fibreglass traps, when sufficiently large, you can see improvement down to about 25 Hz which is quite a bit lower than you might expect. 

This is an example of "enough" bass trapping:










(Ignoring of course the noise floor, you can see the rapid and even decay free of ringing and the fact that peaks have a fairly low Q. Couple more examples here:

http://redspade-audio.blogspot.com/2010/12/bass-trap-measurements.html

More info here:
http://www.hifizine.com/2011/09/bass-integration-guide-part-2/


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## jlird808 (Nov 2, 2010)

Wow Paul Ive actually read that Redspade article and had it bookmarked for about a week now...didnt know u were on HTS!! That's me that made the last comment on the Hifizine article as well! 

Yeah I was thinking of going super fat in the corner behind the TV and on the bookshelf as they dont even have to be angled. They could be square or rectangular (is that what u guys call bulkheads?) at around 12" x 14" thick of 705 and would go up to or close to the ceiling.

I actually plugged my rear ports yesterday which brought a significant drop below 80hz, most significantly around 39hz (around 10db). It may have been a little too much though and Im gonna play around with half-plugging the hole etc and using the RTA to watch the results.

Thanks for the help!!!


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## jlird808 (Nov 2, 2010)

Sweet....I pulled my desk out and my monitors forward off the wall about a foot more and got this:









Still got a ways to go but this makes me feel better lol


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## localhost127 (Jan 2, 2011)

jlird808 said:


> Yeah I was thinking of going super fat in the corner behind the TV and on the bookshelf as they dont even have to be angled. They could be square or rectangular (is that what u guys call bulkheads?) at around *12" x 14" thick of 705 *and would go up to or close to the ceiling.


at that thick, you do not want to use 705 but instead a material with low flow-resistivity such as pink fluffy attic insulation (loosely filled).

htp://i.imgur.com/TUKpT.jpg


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## jlird808 (Nov 2, 2010)

localhost127 said:


> at that thick, you do not want to use 705 but instead a material with low flow-resistivity such as pink fluffy attic insulation (loosely filled).
> 
> htp://i.imgur.com/TUKpT.jpg


Yep...Ive just been reading about that on other forums too...if I wanna catch those low freq I should consider building a superchunk right?

Here's my issue though. From what Ive read, the minimum size required for a superchunk to be effective is 24"x17"x17". I was planning on buying R30 rolls that are 16" wide. I guess they would come out to 22.5"x16"x16". Though I'd have a bit less depth, my ceilings are also 10.5' high and I can go ALL THE WAY UP. 

The alternative is to buy the 23" wide R30's and slice off 5" or so off the entire side and basically toss it. It just seems like a pain in the to cut all that fiberglass off, I'll probably need hardcore shears too. I can't really go past 25.5"x18"x18" due to space limitations.

Should I be ok with the 22.5"x16"x16"? I would probably put it in the corner on the left side behind my desktop, again, from floor to ceiling.

Thanks...hope this makes sense!


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## jlird808 (Nov 2, 2010)

I've also heard differing view points on loosely stuffing fluffy pink stuff in the air gaps behind the corner panels that I do have. 

Any thoughts?


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## localhost127 (Jan 2, 2011)

a change in acoustic impedance will result in a reflection:

some of hannes' commentary may be of assistance to you:

http://www.gearslutz.com/board/6328646-post88.html

http://www.gearslutz.com/board/6281432-post46.html

http://www.gearslutz.com/board/1913176-post29.html


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