Need advices, acoustic treatment positioning, please help!

[Webster]

(If you had already read this thread in the past, please skip to the last reply!)

Hey there mates, i hope everybody is fine!

I ask for your help once more, ive got a brand new pair of Dynaudios (which are already arised 16 cm from the table, and with auralex mopad thingies below them), and built some super chunk 6lb mineral wool basstraps, from floor to 3/4 of the total high of the room. But now i bought a box of "Auralex M32 Designer Series Roominator Kit"(1-Square-Foot Acoustic Panels - Carton of 24.), in order to tame those high and mid frequencies because of my REALLY BAD room dimensions and almost non existent acoustic treatment....

Can anyone advice me where to place those 24 foams? I have some ideas, but i prefer to ask the pros in here first! So i dont have to reposition all foams again and again...

Ive read about the 38% rule, but it seems that because of my small room dimensions, the difference between the 38% and 30% is just a few centimeters, i feel that my sweetspot is really norrow (what i mean is that when i move my head a little forward or backward i can REALLY hear the difference of bass cancelation), i would love to place my table a little bit closer to the wall, but the bass traps are huge... what should i do with them? i was thinking in making some smaller basstraps, place the big traps in the bottom and on top (like a sandwich) so i can place my monitor speakers and table in the mid with the smaller basstraps filling the gap so i can place more basstraps on top. Do i explain myself? Sorry for my bad english... If i have to be more specific please tell me!

If i have to move any furniture or anything, please let me know!

Thanks a lot in advance!!!

[BudgetMC]

Read...
Acoustic Treatment and Design for Recording Studios and Listening Rooms

[Webster]

Thanks a lot for answering my friend!! I have indeed read in the past all the info i could from the great Ethan Winer website, REALLY usefull!! But i was asking for some advices, since my room is really complicated because if its small dimensions (and it is ALMOST a cube).

I want to know also if the idea of fitting the studio monitors into the "basstrap sandwich" i mentioned before, could affect to the bass trap efectivity? (since in the mid i would use smaller traps). My only concern, is the monitor speaker´s ventilation, it wont be THAT much... I hope it doesnt get too high, since mineral wool is a thermal isolator... Do you think it would be a mayor problem?

If i dont explain myself clearly, here are some representations of my idea attatched.

I would also love if anyone advice the use of a few (or a lot) of diffusers.
Any advice from the pros, or any gearslut is REALLY apreciated!!!

Thnx a gain!

[Glenn Kuras]

First don't do that bass trap around the speaker thing. It will not work and will only mess things up. Bass trapping needs to go in the corner, NOT around the speakers like that.

It sounds like you started with some pretty good bass trapping, but because of your room size you really are going to need more (like 3 to 4 times more) to help with the low end room modes. The foam you bought will help with the high end but for the problems on the low end it will nothing. The best place for the foam you bought will me on the left, right walls and ceiling in the early reflection points. One thing I do see you need is THICK absorption on the front and back wall to help with the front to back nulls and peaks you are getting. For the front wall I would use 4" mineral wool or rigid fiberglass and place one 2x4 behind each speaker. On the back wall, if you can swing it I would go with 6" 2x4 inch panels (maybe 2 to 3).
As far as the 38% rule, that is only a starting point, which in some rooms it is better to be a little further back or a little further forward. But you don't want to be in the middle of the room or right up to the front wall.

Diffusion?? Sure I would think the back 1/3 of the room on the right and left wall would work just fine. I would say it will be icing on the cake, so don't spend the money on it right now. Focus on more bass trapping and those early reflection points.

Here is a link to a layout you can go by.
http://www.gikacoustics.com/images/room_kit_03.jpg

Glenn

[Webster]

Couldnt be better adviced!

Thanks a lot Glen! Now im using the mirror technique to see which is the exact reflection point, and yes, i will follow your advice! maybe its easier to put more basstraps than moving the table!

Thanks a lot for your advices!
Happy Holidays!

[Ethan Winer]

Originally Posted by Webster

Couldnt be better adviced!

Next time you need to buy acoustic treatment, remember who was nice enough, and knowledgeable enough, to help you.

Way to go Glenn.

--Ethan

[Webster]

Hello there guys! i hope you enjoyed this summer

Well, after a lot of time since my last post, some reading, watching Ethan´s videos, following Ciro´s and of course Glen´s advice, a lot of basstrap building and a hell of a lot of itching and scratching, i finally have most of my traps done and are already positioned where i thought best.

In the first post i didnt show the actual frequency response of my small room, this time i managed to render the frequency response and waterfall graphs (Octave smoothing 1/24) in jpg with REW. All the basstraps are made out of rockwool.

First Test - May 20 2008 (Yellow colored graphs)

It only had 2 huge 60x80cm super chunk 6lb rockwool basstraps on the front corners, covering 3/4 of the total high of the room, plus a little bit of auralex dst on the early reflection points. The listening position was about 4 feet from the front wall. I had a sea of nulls and peaks on the mid and high range, the bass is obviously out of control.

*Note* I think it has a very high NoiseFloor on this test, maybe because i used a lower master volume, and pushed a little bit more the gain on my motu828´s noisy preamp.

Second Test - March 15 2009 (Dark Purple colored graphs)

Added four 2´x´2 - 4"thick @ 6 Lb square basstraps on the back (2 in the top corners. 2 in the center of the back wall), diminished the size of the superchunks on the front (from 60x80cm triangles to 40x60cm) , they where too big and forced me to put my listening position very close to the spooky center of my room, which messed up a lot of the bass, somewhere in the sub, you could feel/listen a huge HOLE, more noticeable by ear than just watching the graphs. A new BIG cloud was added too, thought it would help a little with bass range, but a lot more significally on the mid range. Moved the listening position now to 3.5 feet from the front wall, moved speakers 3" (placed them closer together).

Well, I noted that the 55hz peak, and the 100hz null a was a little worse on the graphs this time, maybe because of the superchunk size reduction. What was interesting, is that the graph was right in some way, but the difference in sound was more noticeable, specially while mixing on the range between 300hz-600hz, the difference was tiny for the eye, but not for my ears, tighter for sure, a big part of the huge HOLE on the bass was gone, thanks to the listening position change i think. I did notice that the bass didnt "hang" too much like in the past, looking at the waterfall graph i could tell that was true, but again, i could listen a lot more difference than i saw in the graphs.

I still had huge combing on the mid range, man, it sucked bigtime... The stereo imaging was aceptable, but it was far from good (Moving your head to the front more than 4" would mean a big difference, leading to extreme frustration sometimes while mixing). I thought repositioning my auralex dst would help, well... MAYBE IT DID help, but i certainly didnt notice any major difference, again, with all due respect, i felt like an idiot for buying these fancy looking foams, definately not for serious mid range trapping, and for that money, i could had built some other 2 or 3 very functional basstraps, just my 2 cents...

Third Test - August 16 2009 (Light Purple colored graphs)

Added two 2´x4´ -2" thick @ 8Lb Broadband traps, three 2´x´4 - 4"@ 8Lb Broadband traps. I changed the position for some traps, so i could re use better my square 2´x´2s somewhere in the room. (I uploaded sketches of the room as it looks like now). Moved the listening position now to 3ft from the front wall, since i thought that would help for the problem i had on the 400hz-600hz range. Moved the speakers 3" each closer to the wall this time, i thought that would help on the 500 hz problem, which i noticed with my radioshack meter, it came from the lateral walls.

Well, for me the difference was mainly on the decay time specially on the low range. The mids are a lot more defined, the stereo imaging is greatly improved, sweet! But some other problems did appear... A HUGE pair of nulls, on the 700hz and around 3800hz, DAMN! A new null on the 400hz appeared, but the huge problem on the 400hz-600hz improved a lot overall.


To fix these new nulls, I tried again with different speaker positions, changing my listening position a bit... nothing really helped that much, of course some minor peaks and nulls got better, other worse, but these pair of nulls on the mid, and the 400hz problem didnt go away, just stayed there, what could be causing these major nulls? I dont really know what to do now...

I was thinking maybe the table, PC keyboard, and my midi keyboard are responsible of this combing on the midrange, what do you guys think? Since i wont be building traps for a while, what should i do with i have right now? Any ideas?


And finally... here is a question for Glen and Ethan, is there any posibility to buy any of your products on south america (Mexico City)? I think the shipment would be outrageous, but maybe youve got a good idea of the costs etc? I would LOVE to buy the traps (Which DO look cool) instead of making my own this time...

Thanks for reading!!!

Any input is apreciated!

PS- Ah! If you ever wondered why, the speakers on the top shelf are a cheapo pair of BX8, just for xbox gaming, i couldnt place a trap stradled in the corner there because of my cloud trap and the speakers, probably some superchunks fit a lot better, but thats a thing for future upgrades...

[Webster]

Anyone? It would be great to know any oppinions, im really stuck with those 2 huge nulls...


Thanks!

[ciro]

I don´t see separated stands for the speakers for up/down adjusts (+ a much better image).In your 2,30m height, speakers (and ears) placed at the "common" 1,15m will excite the 2° harmonic (around 150hz, you see for the graphics).Try adjusting at least speakers height to see if helps a bit.

I have a simiilar issue with two almost identical dimensions (2,80m x 2,65m here).See what I did:

Thick cloud (7"+ gap) plus a trap in the front wall/ceiling corner.Take a look...(everything´s a bit ugly,sorry)
I´m not saying you need a chunk like this, but absorption there(+ the cloud) makes a lot of difference with the terrible "boom" I had at 50hz (more a long decay time than a frequency issue) and other peaks and nulls (130hz peak was strong too).
(This plus more 18 panels spread in the room,sure).

Try a panel in this front wall/ceiling and see if it helps (ex: REW in the "lowest" mode 1M,or a friend helping, much better) and play a bit more with speakers (including height and "back and forth") and your mix position.Stands give you alot of flexibility... (sorry if you already have it).

Take care of lows first,the null around 100hz is a big problem.

Ciro