problematic accoustics in a room

[Adi Head]

in a week i'll be screening a video piece i made in a gallery. i'm worried about the accoustics in the room it will be shown. the video will be projected on the wall by a dvd projector and amplified by a pair of small pioneer speakers (not sure of the specifics).

the area of the room is about 12x12 ft. and has a high (13 ft.) dome ceiling. there are no carpets, no furniture. the walls are brick. so as you may imagine there is a noticable echo.

there is no dialog in the soundtrack. only music and effects.

i'm looking for a cheap and simple way to improve the accoustics, so that the aucio doesn't echo and sound a like a mess.

there is a catch, to make it just a bit challenging: the room is of some ancient turkish architecture and therefore i can't drill any holes in the walls.

i'd like to avoide putting a carpet on the floor. but if i don't have any other choice - i might do that.

any suggestions or engenious tips??

thanks!

[Jacques Mersereau]

Carpet on the floor is your easiest helper. I doubt it will fix the problem,
but it will undoubtly help. The only other thing would be to hang
fabric, but from what you said, you'd have to bring in what we call
"pipe and drape". That stuff used in trade shows to
fabric off booths. Upright pipes sit on or screw into bases.
Cross braces lock into the uprights and you hang the fabric.
You can rent pipe and drape in most larger cities.

The stuff we bought here at the U. has 10 ft. uprights and adjustable
cross braces 8-14 feet.

[Andre De Clercq]

Try to get heavy drapes and hang then a couple of inches away from the walls.

[Adi Head]

ok. i'll check out the pipe and drape option. although i'm not sure how easily i'll be able to find heavy drapes. what if i find a way to stick egg cartons on the walls or something? i've seen people use those in home recording studios.
if you come up with any more ideas, i'd be very happy to hear them.

thanks!

[Douglas Spotted Eagle]

Egg crate on studio walls is nothing more than cheap (and ineffective, mostly) diffusion. Pipe and drape is an excellent and potentially artistic option. Bodies in seats will make a huge difference. So will heat. Warm air absorbs considerably more sound than cool air. (Ever notice how much more clear sound is in the winter?)
Hanging a flag from the ceiling is another cheap option. From there, it starts to get more complicated and a lot less cheap.

Not that anyone has mentioned it, but no matter what, do NOT put eggcrate foam on the walls. Illegal, and dangerous as hell.

[Adi Head]

ok. thanks for the advice. i'll go look for drapes.
as far as heating up the place: unfortunately, if i turn off the a/c during summer days in israel, i won't have to worry about accoustics at all, because no one will be there to hear it.

thanks.
adi

[Bruce S. Yarock]

How about an equalizer?

[Douglas Spotted Eagle]

An EQ isn't going to do much for room bounce, if anything at all. An EQ will allow for the sound system to be tightened, and should be part of the overall master system, however.
Pipe and drape 6" from the wall will be the lowest impact, lowest cost bounce-detractor.

[Jacques Mersereau]

If do anything like this in someone else's place,
you want a solution that the "house" will like and
approve. Pipe and drape doesn't hurt anything and looks good.
A bit of work in setup, but with a room this size
you can put it up and take it down in 15 minutes with two people.
We many times we use a broom to set the cross braces so you don't even
need a ladder, though advised. I'd check with the "house" to see if
you can borrow a ladder from them.

Make sure you get a good long "sample" of the room's 'silence.'
Later on you may need it for noise reduction software sampling
and making nice smooth noise floor fades were none exists due to
hard editing.

[Andre De Clercq]

An equalyser can only optimize a small area in a reflective room, and make other areas's worse. So no no for an equaliser in yr case.

[Douglas Spotted Eagle]

>>>So no no for an equaliser in yr case.<<<
Here, I have to disagree. The room's architecture could, and likely will, reflect some frequencies more loudly than others, and amplify contents of the audio that may not be balanced. An EQ, used to cut those out of balance frequencies, can be a great tool. This is exactly part of what an EQ is designed for, to tune a sound system to a room's tuning, making them more compatible.
Using an EQ to boost a group or large set of frequencies may be problematic, but using an EQ to compensate for room imbalance and deficiencies in the overall sound system is not only common, but generally required, depending on a number of variables.

[Adi Head]

thanks for all the help and advice. i actually think i can get an EQ hooked up there.
jacques, i didn't quite get what you said about recording a sample of the room's silence. i do that when recording sound in a room, but i don't understand how this could be useful in PLAYING an already completed video work in the room.

thanks again everyone for all the help!! :-)

[Andre De Clercq]

Non anechoic rooms show different reflection (and audible reveberations if large enough)patterns. Good room acoustics are supposed to show a certain amount of reflectivity. The higher frequencies mostly (if the walls are not too "hard") are diffuse reflections and if there is not sufficient diffuse reflection this can be compensated by an equalizer (or just treble setting). The lower frequencies (below cut off) are hard and show up as standing waves. That kind of unwanted acoustic pressure situations that show up in specific zones can be compensated only for the specific zone and make the other zones worse. If one is listening in a zone where a specific acoustical frequency is too high, one can lower this acoustic overpressure by an equalizer but the zone where there was no overpressure will lower too and specific frquencies will be missing in the latter case. So no equalizer if the listening zone is not specified and very limited. B.t.w. that's the big issue w.r.t. the microphone equaliser feedback methods.

[Jacques Mersereau]

<<<-- Originally posted by Adi Head : thanks for all the help and advice. i actually think i can get an EQ hooked up there.
jacques, i didn't quite get what you said about recording a sample of the room's silence. i do that when recording sound in a room, but i don't understand how this could be useful in PLAYING an already completed video work in the room.

thanks again everyone for all the help!! :-) -->>>

My bad. I thought you were also video taping.

[Giroud Francois]

the common approach is to put 2 loudspeaker and use power to fit the need. This works well in open air or when the power can be strong enough to cover the echo.
in you case, you could get an excellent sound by setting several loudspeaker at low power.
the cost of loudspeaker for PCs is affordable enough to get several pairs of them and the fact they are (most of time) amplified, can ensure you that a minimum of additional hardware will be necessary. each level loudspeaker can be adjusted and they are small/light enough to be mounted on a small pole, so no wall drilling will be necessary.
Two 5.1 system could even be better as they provide usually a better bass loudspeaker (and gives ou 10 loudspeaker at once)