acoustics advise needed

[emreyazgin]

I have a nasty problem in my bedroom (i mean soundwise ) I am no acoustician, just general knowledge from articles books and the introductory course at sae. With my limited knowledge i did a sine sweep test, i put a cardioid condenser mic nearly to the same position where i listen to my speakers and recorded the sine sweep output from speakers. The result is as in the mp3 attached.

- Nasty 145 hz it looks like mount everest @ that freq!
- Some null points at two other frequencies, i guess 200

Of course i know that there are limitations for this kind of test due to mic coloration or speaker coloration, what i used is nt1a and tannoy reveal 5a's.

The room is as in the image attached.

Any ideas to improve the situation (of course hiring a new place etc is not appicable to me..i am a student, so i can't treat the room heavily as well..)


Thanks a lot!!

[Ethan Winer]

emrey,

> The room is as in the image attached. Any ideas to improve the situation <

You need bass traps and other acoustic treatment. But especially bass traps, and as many as you can manage. I also suggest you rotate your setup so you're facing the window on the right. This puts the wall behind you further back, and also makes things more symmetrical left and right. And slide the wardrobe back too if you can. It can be on that wall, but it's best behind your head.

The drawing below shows an ideal way to set up the speakers and listening position in a room like that. For more information on room treatment see my Acoustics FAQ:

www.ethanwiner.com/acoustics.html

--Ethan

[emreyazgin]

for 145 hz i guess i need something like a 1/4 of wavelength of 145hz deep bass trap?? does the bass trap have to be on the floor? what if i put it to the corner where the bed is? there is a big space on the ceiling on top of the bed.

[emreyazgin]

wow, hey is that your article?? i was reading it yesterday!! i got the sine sweep test idea from your website!..its a great site..thanks for that

[tINY]

145 Hz, huh? I bet you have an 8 foot ceiling.

That would give you stong resonances at about 70, 140 and 210 Hz....





-tINY

[emreyazgin]

the ceiling is about 2.5 meters..

the big resonance is at 145 hz and other harmonics, and there are some nearly null points as well...its soo nasty...

[narco]

2.5 meters = 8.2 feet.

well done tINY go to the head of the class

follow ethans advise and definitely check out his forum, it has all the answers, except the meaning of life, but I'd bet he's working on that one too

oh, and if you've got a pc and a omni condenser check out the demo software at http://www.etfacoustic.com/ for measuring more accurately, the demo is all you need for basic use

narco

[emreyazgin]

how come you can guess the height of the room without knowing the W and L and just a resonance freq?

[emreyazgin]

i already downloaded EFT, its a great piece of software, but i need to buy the licence for sine sweep test and a for couple of more functions..money money money

[emreyazgin]

this is the rooms response to a 20-200 hz sine sweep...its the worst room ever i guess..im gonna try to build a bass trap and see what happens

[tomdarude]

Originally Posted by narco

..... it has all the answers, except the meaning of life, but I'd bet he's working on that one too
narco

it´s 42 !


think I read it somewhere in ethan´s faq´s, too

[Glenn Kuras]

Originally Posted by emreyazgin

this is the rooms response to a 20-200 hz sine sweep...its the worst room ever i guess..im gonna try to build a bass trap and see what happens

wow if that was a roller coast that would be one hell of a ride.
As Ethan said you may want to change your mix position to fire the speakers down the longest wall, but if you can not I would put as many bass traps as your could stand in that room. Starting with the front two corners floor to ceiling and treat the back corners also. You many want to put a few on the back wall. Then at that point I would build or buy panels for the first reflections in the room. Don't forget about the ceiling!


Glenn

[Dog_Chao_Chao]

Originally Posted by tINY

145 Hz, huh? I bet you have an 8 foot ceiling.

That would give you stong resonances at about 70, 140 and 210 Hz....





-tINY

My freqs too. Want can I do to the ceiling?

[tINY]

Not a lot of options with an 8 foot ceiling.

You can try changing the height of your speakers. The reason that you don't see a big resonance at 70 Hz is that your speakers are probably close to half way between the ceiling and floor and are unable to excite that one. If you move the speakers away from the midpoint of the floor and ceiling, you may excite the 140Hz stuff less.

If you own the space, and there is room above, you can put some membrane or slot traps in the ceiling. Or, better yet, take out the current ceiling and put in a cathederal-type ceiling with an interier pitch of at least 2/12.

You could probably mount some woofers on the ceiling and use an LPF and a delay and get some releif, but that's pretty extreme too.

Lot's of bass trapping in the corners is the easiest thing and probably the right thing to do if you can't move to a bigger room yet....



-tINY

[tINY]

Alright - I just went to the house of Ethan...

Looks like the Soffit Traps from Real Traps might be just the ticket. They're a bit pricey at $50/foot and I doubt Ethan is going to give up the secrets on this one....




-tINY

[emreyazgin]

Now i got how you got 8ft...the first room mode..just the reflection from speaker to ceiling then back..considering the speaker is approx. sitting in the halfway between ceiling and floor..clever :)

Originally Posted by tINY

Not a lot of options with an 8 foot ceiling.

You can try changing the height of your speakers. The reason that you don't see a big resonance at 70 Hz is that your speakers are probably close to half way between the ceiling and floor and are unable to excite that one. If you move the speakers away from the midpoint of the floor and ceiling, you may excite the 140Hz stuff less.

If you own the space, and there is room above, you can put some membrane or slot traps in the ceiling. Or, better yet, take out the current ceiling and put in a cathederal-type ceiling with an interier pitch of at least 2/12.

You could probably mount some woofers on the ceiling and use an LPF and a delay and get some releif, but that's pretty extreme too.

Lot's of bass trapping in the corners is the easiest thing and probably the right thing to do if you can't move to a bigger room yet....



-tINY

[emreyazgin]

any ideas why in all absorption coefficient reference charts there are values bigger than 1.0 ??

ex: http://www.marktaw.com/recording/Aco...Calculato.html

[Ethan Winer]

> any ideas why in all absorption coefficient reference charts there are values bigger than 1.0 ?? <

See the article Measuring Absorption on my company's web site which explains this in detail:

www.realtraps.com/art_measure.htm

--Ethan

[Ethan Winer]

tINY,

> They're a bit pricey at $50/foot <

Just so you'll know, we generally discount these, so most people pay less than that.

--Ethan

[Glenn Kuras]

Originally Posted by emreyazgin

any ideas why in all absorption coefficient reference charts there are values bigger than 1.0 ??

ex: http://www.marktaw.com/recording/Aco...Calculato.html

It is a few things but the biggest is sound comes in from the sides and hits the panel. Also the panel is spaced of the wall which helps a lot. That is part of the reason I jump up and down about NOT putting wooden sides on and spacing them off the wall..

Glenn