My Room Acoustics Part 2

Some background reading..............if you like............. http://medicine.jrank.org/pages/777/Hearing-Auditory-performance.html Three Acoustical Issues that Room Correction Can’t Correct http://www.hifizine.com/2010/09/the-three-acoustical-issues-a-room-correction-product-can%E2%80%99t-actually-correct/ In a nutshell............ Issue number 1: place a subwoofer at the corners of the room. To reduce the problem of speaker boundary interference response(SBIR for short). /I choose to have 1 subwoofer each in the front section of the room, 1 on the left corner and 1 more on the right corner. /That's will be 2 subwoofers specifically used to for this purpose and not doing the main task of reproducing enough bass contents to add to the sound of the main speakers. This helps explain 1 of several reasons for the introduction of additional subwoofers for the sole purpose of reproducing bass contents to emerge with those of produce by the main speakers, ie. integrate the bass contents. A total of 7 subwoofers are in placed at the time of writing. Issue number 2: reduce/control of early sound reflections from the many surfaces of the room relative to those direct sound from the speakers. /Work out a suitable combination of direct and reflected sound for that particular small room with acoustic treatments. The level of reflections can only be controlled through appropriate use of absorption or diffusion or by selecting speakers. /I choose the use of the ceiling treatments for a small room and at the 1st reflection point from the position of the speakers. And the choice of speakers happens to be very unorthodox. Issue number 3: rt60 cannot apply in a small listening room. The decay time of the room can only be brought to the level needed for high quality sound reproduction through appropriate decorative choices, furnishings and the use of acoustic treatment.............. /A simple hand clap will tell! Reduce the long reverberation time to bring up the sound quality, by reducing any overlapping of sound to perceive much readily the time gaps between individual sounds if any.

My Room Acoustics

Ceiling treatment behind listener It's not often one writes about his/her own hifi setup, details of the gears or even about the room where most part of the listening are done. However, after all a blog is like one's diary in which case a written records of one's hifi journey, seems quite proper, irrespective of whether any readers may or may not like what he/she reads or find the article not of any use at all, or even at times deemed offending to some particular readers!  From listener's position What I have in mind is a brief write up of my hifi journey in room acoustics. It may not be any readers' idea of room acoustics, and may even be deemed doubtful as to its effectiveness for the purpose of enhancing the listening pleasure of any listeners in the room! No 2 ears are the same, so probably no 2 persons could agree on what he/she may perceived of the sound. And lastly I'm not here to suggest that having a room made acoustically 'comfortable' for even a brief period of listening can replace the need for really good sounding hifi equipments and any ancillaries used with those hifi gears! So if one thinks getting the best equipments one could afford is the first and foremost the most important factor over room acoustics or nevermind the room acoustics, and the need for room acoustics treatments are not that important to him, there is no need to argue on this till the cows come home. It's your listening time, you could do whatever 'floats your boat'!

My involvements with room acoustics started with the need to address the already bad echoes and bass sound in my 8ft by 14ft smallish room with a sloping ceiling. The cross section of which depicts the shape of a true trapezium! There I was deciding to live with the disturbing sound from the system's playback, or do something about it! Doing something would seems to, going to take forever........a really daunting idea, and really frightening at that time!!! So it was decided, at some time 3 years ago, that I would do the surface treatments of the ceiling as there isn't enough floor space in the room to do anything really significant. Neither could I do anything much to the walls of the room because of the width of the room, though the first reflection points in the room as regards to the placement of the speakers have to be addressed properly, accurately or not, I thought that may be another issue.

Off I went to collect recyclable materials of cardboard, pieces of wood and even foams made from different materials, from electrical shops, and asked friends for these recyclable stuffs. When I have gathered enough of these materials, it was time to sit down to look at them and to get ideas and raked thru the brain for any useful data and information. Took about a couple of weeks of material collections and doing google search of information on room acoustics to finally come up with some idea of doing ceiling treatments. Then the need to have those designs hold up to the ceiling permanently, and came up with the idea of using very thin metal wires to hold them against the ceiling surface, and should be removable in the event of wrong placement or the wrong design and to even cover the worst of my thoughts, to have them removed and reused in the event that I have to shift house!!!

  

Side panels: Composite design

So after much experimentations, with design and choice of placements, finally came up with a design that was kept till this day. All in all it took just about 100 manhours to complete the task of doing the ceiling treatments. So far the room could now 'support' the use of multiple subwoofers reasonably well(meaning it's just about tolerable), I could do better if I had tried other ways, but there is no way to find out now for sure, I thought. So ended the 1 major project I have ever undertaken, and I considered it 1 big step for me along the way of my hifi journey.


 Written by Uncle Vic

SAT bass trap 2- diy bass trap

Update SAT bass trap

Somkeone ask me why you use 6 ply of carpet instead of 5,7 or 8 ply. Good question,actually it need a mass of 1.49kg/m2.
Here is the calculation:
The panel surface

1.74 x 0.29 = 0.5046 m2,
1.49 x 0.5046 = 0.75kg



I have weight 1 ply of carpet is around 145gram(less10% to minus the excess)=130.5 gram

So 750 gram/130.5 = 5.74 ply,
So round it up around 6 ply.

I have try out 3 ply carpet at first and it is not working.6 ply give me more satisfactory result. Sometimes we really need to do calculation to cut down the trial and error.
On the 1st version i can varying the depth of the bass absorber panel.
I found that the result is close what i have calculated out.

KLau