Acoustic Room treatments

Sir,

All the houses / apartments in India are made with Bricks / Cement / Motor etc. Yes they are 'hard surfaces'
You will need to put in a lot of carpets and rugs on the floor.

With regards the low frequencies, if you are to use the N805 [B & W] then you may not have a problem with bass load or boom. The 'Book Shelf' has an FS of 42.
http://www.bowers-wilkins.com/display.aspx?infid=1153&terid=1259

Just put some diffusers on the rear and side walls and you will be OK.

I am a believer in diffusers in place of absorbers.

More later.

Thanks for the reply Bhagwan69,
Yes you are right - I do not anticipate too much bass frequency problems with my 805's which will reside in my audio only system, but I was more concerned with my HT wherein I will have a SVS 20-39 PC ultra sub that goes down to 20hz at 100 db and can be tuned to go down further. I used 4 bass traps in my room here in the US to tame the reinforcement of my room mode at 25- 30 hz. Unfortunately the traps were big and bulky and would not fit in my shipment.
Well if there is nothing available in the market then there is always the DIY option. I hope fibre glass insulation is easy to find in the market. If so is should be quite easy to build a bass trap.
Thx. Sid

Murthy in Bangalore makes a variety of room accoustic treatment items under the Finnese brand.
Prithvi who deals in them will be able to provide you with deatils.

sidvee schrieb:

Yes you are right - I do not anticipate too much bass frequency problems with my 805's which will reside in my audio only system, SVS 20-39 PC ultra sub that goes down to 20hz at 100 db and can be tuned to go down further. I used 4 bass traps in my room here in the US to tame the reinforcement of my room mode at 25- 30 hz. Unfortunately the traps were big and bulky and would not fit in my shipment.

Sir, for your music only, there shall be no 'bass' issues what so ever.

However, with your HT, there are 2 ways of looking at it;
Either you tune your subs to play only till 35 Hzs.
Alternately live with the problems, since 20 to 30 cycles have wave lengths that are 30 to 40 feet long. To tame that you will need bass traps that are at least 4 to 6 feet deep. This you can never manage in any apartment in India [except a mansion / bungalow].

Essentially you need a lot of enery between 50 & 100 cycles while watching movies. Except for Dinasour and the likes, most movies do not have anything that plays below 35 cycles.

However, what I have mentioned are only suggestions, I am not fully sure of the facts, so if I have made some wrong statements, please do excuse [& suggest correct facts] !

Hi Bhagwan69,
Please see attached:
http://www.acousticsciences.com/tubetrap-flyer.pdf
A 20" dia. tube trap can absorb upto 30hz and beyond. In theory you are right but I believe the tubular nature of the tube trap facilitates low frequncy absorption. I used to have 4 of these in my home theater room and 2 smaller one in my audio room. When I measured frequency response before and after, the low frequency room response of my HT smoothened out nicely and the impact of action movies was literally gut wrenching in that you could fell the bass course through your body.
Also in most of the newer action movies a lot of action/excitement is in the 35 -25 hz range U571 for instance (http://www.svsound.com/questions-faqs.cfm#moviedemos). The preceding site will show you waterfall plots of bass heavy scenes.
.If one cannot experience that than a lot of the impact IMHO is lost. Also for music listening, the smaller traps smooth out the frequency in the 40 hz and above category providing a better bass foundation (with more pitch definition). Music rooms will also benefit from adding absorption to first reflection points along the wall and ceiling though these will not absorb below 50 hz (in most cases)
So in summary I reiterate that sound treatements are a critical part of any HT or music room though they are not widely used. As always, these are my views and opinions and not absolute facts, but one is welcome to experiment.

Any el-cheapo suugestions? Can rugs or thick turkish towels make any difference?

Hi zhopuday,
Addition of rugs thick wall decorations will definitely help but these will absorb only the higher frequency sounds 400 hz - above. What I have noticed is that to get any meaningful lower frequncy absorption one has to use stuff like fibre glass, thick cotton batting covered with acoustically transparent material like burlap (gunny sacks). In fact one can make simple but effective treatments with these materials - only problem would be finish - there a lot of DIY panels - google it and you will see a lot of projects.
Finally to absorb low frequency one has to have tube traps like the ones discussed below but there are DIy examples of tube traps also.
Thx.
Sid

I personally recommend empty speaker boxes with 1 of the lids kept opun.
Basically, any cardboard or thin 6 to 8 mm ply loosely places in any bigger enclosure will make great low frequency absorber.

However, in my limited experiance, I have found all this to work till 40 - 50 cycles. The 20 to 30 - 35 cycle bass is very very difficult to absorb. specially if you mention 100 dB of sound pressure level, man God Help You !!! There will be a lot of 'energy' in the room. You see in the states the walls and partitions are made of wood, and they move and dissapate the energy. In India the material is B & M [Brick & Motor], hence B & M will only reflect the energy back.
I have always faced a problem, if you find some DIY solution that has a WAF [Wife Acceptancy Factor] of 6/10 + please do shre it with me !!! I would be truly very very thankful !!!

Dear Bhagwan,

I am just thinking aloud.

Will it be possible to make use of the space above the false ceiling as a bass trap. The false ceiling should be thin enough to allow LF to pass through and we can fill up the space above with large quantities of sound absorbent material which in turn will convert the sound energy into heat. The ceiling can be divided to suitable length for freq to be corrected.

Regards
Anil

Like Jeeves mentioned, get in touch with Murthy. PM Prithvi for contact details. This gentleman has been making bass traps here in Bangalore for a long time now. He can help you out with any kind of room treatment.