problematic accoustics in a room
 

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!

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.

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

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!

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.

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

How about an equalizer?

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.

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.

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.

>>>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.

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!! :-)

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.

<<<-- 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.

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)

Good idea Francois! Maybe low freq response could be a bit down with these small/cheap speakers, but reflectivity problems will be greatly solved.

Actually, a single sub with one of the sets would probably turn the trick. Distributive is better, but does occupy more space and could be a cabling mess.
We did an event recently in Sydney, where industrial Velcro was used to hold extremely small speakers on microphone stands with a bit of heavy cardboard attached to it. Worked quite well.

this is usually working well in place like museum ,church or other high reflective and silent room.
The only problem is that you can not usually keep up with a noisy and compact crowd because power is not available.
For the bass, you could be surprised by the ability of these small boxes to generate earthquake rumble (don't forget , they are designed for game).
My preference goes to the Logitech Z-640, others models usually have a too metallic sound.

let's see if i understand what you're saying. about the multiple speakers at low power... do you mean that if i hook up an additional pair of cheap PC speakers to the receiver in addition to my pair of 100W pioneer speakers, i could improve the sound?

by the way, the receiver has a 5.1 speaker system. how exactly do i connect PC speakers to that?

adi.

I do not know what you mean by 100W loudspeaker, but if it is real professional equipment rated 100W RMS, this is huge the room you described.
The proposal of having multiple low power loudspeaker includes the fact that you are not using the 100W installation system (or set it up to play very low).
5.1 pc system have the big disadvantage that few of them comes with other input than 3 minijack well suited for pc output, less for other 5.1 devices like DVD players (usually coax or optical).

<<<-- Originally posted by Giroud Francois : I do not know what you mean by 100W loudspeaker, but if it is real professional equipment rated 100W RMS, this is huge the room you described.
-->>>

Pardon? Not hardly. Wattage and volume are not necessarily related at all. More wattage in the amplifier simply means more headroom so that the system may operate more efficiently. Particularly computer speakers, which have horrible efficiency ratings anyway.
Moreover, you're not likely going to find a system that would fall into the "professional" category that's only 100 watts RMS.

Regarding the 5.1 speakers, I'd forget about the center and rear speaks, and rather use "Y" cables to feed additional systems. You don't have to worry much about impedance mismatches because you're not loading down an amplifier, although your more lengthy runs will induce noise into the system. Quality of cable and presence of noise-generating sources will determine just how much noise.
The best way to manage this at all is to set it up in your living room beforehand, work with the cables, and find out more for yourself. While many folks here in the forum have various experiences with this sort of scenario, it's also likely that you're going to end up still figuring your specific need out on your own, and since none of us are there, you need to know what you've got before you get there.

ok douglas. could you please just explain what Y cables are?