705 as broadband? how broad we talkin?

[raticusfortuna]

greets,

i've moved into a new room for mixing and the past few months have been translation he11. i've been lucky in past rooms and just a few room tweaks got my mixes translating.

i have met my match with this new room and actually have to get past the 'guess and pray' approach. many stickys and searches later i think i've got the gist of how to go about this -

1. very basic room treatment and proper equipment placement.
2. do room analysis.
3. adjust and analyze, adjust and analyze, followed by adjustments and analysis.

I'm just digging into '1' and have downloaded REW 5.0 for '2'. (working with REW is the intimidating part of all this.)

THE QUESTION -
in this first step of setting up the room to have something to analyze. i have 9 bass traps each made of 4" of an OC 705 type panel. (2'x4', 6lb density, no foil). are these traps too thick and dense at this point to be broadband? how does this type of trap effect the higher FQ's and will i need additional absorption just aimed at the high end?

i have about 20 1'x1' inch thick auralex wedgie panels. i though these might prove useful. i've been informed recently that they will be, in that i have enough of these to wash my car until about 2015.


thanks for your help,
raticus


here's some facts about the variables -
room size - L9'xW7'xH8'
monitors - bluesky 2.1 prodesk (so there's a sub)
most obvious problem - bass null throughout room
construction - wood floor, 2 walls paneled, 2 walls sheet rock, pressed wood fiber tiles for ceiling.

[Jens Eklund]

Originally Posted by raticusfortuna

THE QUESTION -
in this first step of setting up the room to have something to analyze. i have 9 bass traps each made of 4" of an OC 705 type panel. (2'x4', 6lb density, no foil). are these traps too thick and dense at this point to be broadband?

4" (gap or no gap) is not considered a bass trap simply because it will not absorb bass efficiently. If velocity based absorber, it needs to be a lot thicker and preferably with an air-gap:

http://www.gearslutz.com/board/6749988-post7.html

[takman]

spend time on REW forum on theater shack.

you are going to have to learn the program. Sorry, no way around this.

you cant just take some measurements, post them on here, and say "heres my graphs..what do i do?" Well, you could actually........A lot of guys try that, but they dont get much in responses.....

Knowing how to present the graphs correctly is key too. I see a lot of guys post a waterfall showing the entire spectrum 20-20,000hz...when for that particular graph, we are only interested in say 400hz and lower. These are usually people who dont want to spend time on it, just looking for an easy answer....

Read the help section in REW. The graphs we are most interested in is the ETC, waterfall, frequency response. you need to understand what you are looking at.....

its not as difficult as it may seem, just time consuming..

[raticusfortuna]

Originally Posted by Jens Eklund

4" (gap or no gap) is not considered a bass trap simply because it will not absorb bass efficiently. If velocity based absorber, it needs to be a lot thicker and preferably with an air-gap:

http://www.gearslutz.com/board/6749988-post7.html

thanks jens,
obviously wishful thinking on my part to call these bass traps.

i'll set these up for my first points of reflection and then attempt to wrap my head around the analysis software.

would a 4" gap for the first reflection points help significantly or are the gaps mostly for bass traps?

raticus

[raticusfortuna]

Originally Posted by takman

spend time on REW forum on theater shack.

you are going to have to learn the program. Sorry, no way around this.

you cant just take some measurements, post them on here, and say "heres my graphs..what do i do?" Well, you could actually........A lot of guys try that, but they dont get much in responses.....

Knowing how to present the graphs correctly is key too. I see a lot of guys post a waterfall showing the entire spectrum 20-20,000hz...when for that particular graph, we are only interested in say 400hz and lower. These are usually people who dont want to spend time on it, just looking for an easy answer....

Read the help section in REW. The graphs we are most interested in is the ETC, waterfall, frequency response. you need to understand what you are looking at.....

its not as difficult as it may seem, just time consuming..

takman,
seriously, thanks for showing me the lay of the land in all this. i'm definitely at the stage where i don't know how much i don't know. .... and there is a lot to not know about this stuff. ignorance and the internet..... a dangerous combination.

...off to become REWliterate. wish me luck.
raticus

[localhost127]

Originally Posted by Jens Eklund

4" (gap or no gap) is not considered a bass trap simply because it will not absorb bass efficiently. If velocity based absorber, it needs to be a lot thicker and preferably with an air-gap:

http://www.gearslutz.com/board/6749988-post7.html

Jens,
what if he were to place the porous absorbers horizontally in the corners (48" width, 24" height) - should be fairly easy for him to test with if he has enough to stack floor to ceiling, and the big increase in air-gap should provide much more LF trapping. im interested to see the results!

[Jens Eklund]

Assuming the modal issues are primarily in the horizontal plane and not very low in frequency, it might work.

[localhost127]

Originally Posted by raticusfortuna

thanks jens,
obviously wishful thinking on my part to call these bass traps.

i'll set these up for my first points of reflection and then attempt to wrap my head around the analysis software.

would a 4" gap for the first reflection points help significantly or are the gaps mostly for bass traps?

raticus

be aware the absorber will have a reflection coefficient. you may be better off with OC703 at the first reflection points, but you can easily determine whether they are truly absorbing the entire specular early reflections (and whether energy is grazing or reflecting off the panel) by using the ETC response in Room EQ Wizard (measuring one speaker at a time).

4" material + 4" air-gap should do nicely, but you can confirm with the ETC. you could even try a 2" air gap if real estate is important. the ETC will detail whether the reflection is being attenuated to your desired requirements (and increase air-gap, angle of incidence (angle the panel), or increase material as needed).

[localhost127]

Originally Posted by Jens Eklund

Assuming the modal issues are primarily in the horizontal plane and not very low in frequency, it might work.

got it - thanks,

[DanDan]

raticus, it would be useful to have room dimensions and what each boundary is made of. e.g. Concrete, sheetrock, wood.
Also in what way are the mixes not translating. Are they coming out bass heavy or too bright?
You can see what such sheets of 705 are capable of doing at
Rigid fiberglass density tests
Do note that such materials have greatly enhanced behaviour at LF in corners.
Acoustics Forum • View topic - Corner Absorption Comparision test
Slightly thicker panels, 6inch, mostly without airgaps are capable of this
YouTube - ‪Hearing is Believing - The Ultimate Small Mixing & Mastering Room‬‏

Nine four inch traps is not a lot. Be it porous or other, it usually takes a helluva lot of bass trapping to make an impression on small room LF problems.
As it stands, put eight of them straddling the corners. The last one could be used as a cloud.
The foam should work fine for early reflection control at HF.
I would mount it on an open frame. A garden growing frame or such.
This will allow a gap behind it of say 2-4 inches.

Or you could use the nine to created an RFZ and do full size SuperChunks, floor to ceiling in all corners. The Modex Corner and PrimaCoustic MaxTrap look pretty powerful to me also.

Elsewhere Gernot is working on DIY VPR type traps. Initial results are amazing.
You can buy these. Modex Plates, and Modex Broadband.

DD

[raticusfortuna]

DD,

great stuff, many thanks. the many possible uses for what i do have is very helpful and has curbed my need to panic. i'll be pouring over those links tonight.


a few months ago i said to myself 'i think i should spend a few days getting my acoustics together'. 3 months later.........woof. still an absolute beginner.

i am very proud of the fact that i did include my dimentions and wall composition in my post! i may not have absorbed (now that is sad) the science of acoustics but i'm getting better at posting about it. (i'll take any small victory at this point.)

without compensating from getting used to the room, the bass ends up boomy and without definition. and there's a hole where part of my mids should be. (in between the low mids and the high mids it seems).

thanks for posting
raticus

Originally Posted by DanDan

raticus, it would be useful to have room dimensions and what each boundary is made of. e.g. Concrete, sheetrock, wood.
Also in what way are the mixes not translating. Are they coming out bass heavy or too bright?
You can see what such sheets of 705 are capable of doing at
Rigid fiberglass density tests
Do note that such materials have greatly enhanced behaviour at LF in corners.
Acoustics Forum • View topic - Corner Absorption Comparision test
Slightly thicker panels, 6inch, mostly without airgaps are capable of this
YouTube - ‪Hearing is Believing - The Ultimate Small Mixing & Mastering Room‬‏

Nine four inch traps is not a lot. Be it porous or other, it usually takes a helluva lot of bass trapping to make an impression on small room LF problems.
As it stands, put eight of them straddling the corners. The last one could be used as a cloud.
The foam should work fine for early reflection control at HF.
I would mount it on an open frame. A garden growing frame or such.
This will allow a gap behind it of say 2-4 inches.

Or you could use the nine to created an RFZ and do full size SuperChunks, floor to ceiling in all corners. The Modex Corner and PrimaCoustic MaxTrap look pretty powerful to me also.

Elsewhere Gernot is working on DIY VPR type traps. Initial results are amazing.
You can buy these. Modex Plates, and Modex Broadband.

DD

[musikmaschine]

Originally Posted by takman

spend time on REW forum on theater shack.

you are going to have to learn the program. Sorry, no way around this.

you cant just take some measurements, post them on here, and say "heres my graphs..what do i do?" Well, you could actually........A lot of guys try that, but they dont get much in responses.....

Knowing how to present the graphs correctly is key too. I see a lot of guys post a waterfall showing the entire spectrum 20-20,000hz...when for that particular graph, we are only interested in say 400hz and lower. These are usually people who dont want to spend time on it, just looking for an easy answer....

Read the help section in REW. The graphs we are most interested in is the ETC, waterfall, frequency response. you need to understand what you are looking at.....

its not as difficult as it may seem, just time consuming..

I tried starting on the path with REQ yesterday but i couldn't get past the sound card calibration part.

[DanDan]

My apologies raticus, glossed over the info at the bottom of your post.
Lots of 'soft' boundaries for the LF to pass through.
Bass light room. Two subs would give you more power and other great options in terms of placing them to advantage.
Even the one gives scope for experiment.
Do a search on multiple subs, I think there is stuff at the Genelec site.
Great exercise on sub integration at the ETF site.
GS Tiny is good on this.
Don't be afraid to play with the crossover point to thicken the low mid, and the bass level to, well, hear bass.
When measuring with REW etc. please be aware that flat is not a goal that delivers translating mixes. See Understanding RTA at studiotips.com
That curve works.
musik, I don't think sound card or SPL calibration is mandatory.
Fire the thing up and play with it. Get subtle later.
http://www.gearslutz.com/board/studi...er-v2-1-a.html

DD

[musikmaschine]

Thanks DanDan! All i wanted to do was see if the panels i bought are absorbing low frequencies before turning them into traps.

[raticusfortuna]

DD,

any idea why eathan w. uses two bass traps flat against the wall, as opposed to straddling the corner, in his ultimate mix and master video that you linked?



raticus

[Glenn Kuras]

Originally Posted by raticusfortuna

DD,

any idea why eathan w. uses two bass traps flat against the wall, as opposed to straddling the corner, in his ultimate mix and master video that you linked?



raticus

I believe to just save room. Putting 2 in the corner flat is about the same performance as 1 straddled. BTW more about bass traps and how they work.
How Bass Traps Work. Acoustic Panels and Bass Traps.

[raticusfortuna]

glenn,

traffic jam vs. 10 miles of bad road.......got it!

you guys rock........he11, maybe even polka!
raticus

Originally Posted by Glenn Kuras

I believe to just save room. Putting 2 in the corner flat is about the same performance as 1 straddled. BTW more about bass traps and how they work.
How Bass Traps Work. Acoustic Panels and Bass Traps.