I was asked to propose a solution to reduce echos in a large event hall measuring 70 feet long by 60 feet wide with ceiling height 14 feet( I have never done anything of this sort before). The room will be used for seminars & presentations for 100-200 people seated or standing. The flooring is made of vitrified tiles/ceramic tiles and the 4 walls are made of some kind of highly reflective paint. The ceiling is PoP with 12 feet long concealed ducts for AC .The echo is uncontrollable.

They are running on a very tight budget, so covering the entire floor with carpeting seems very expensive, so is acoustic panels.The ceiling is also off limits due to AC vents & lighting.

For a start i am proposing that tall indoor potted plants be placed in all the 4 corners. Then cover the first 1/3rd of the walls(toward the front ,near the stage area) from top to bottom with thick velvet curtains, and see if the echo reduces. If it doesn't do much, then repeat towards the back 1/3rd. Is there any other approach to handle this?

Also I have a choice of proposing either 15-20 in ceiling speakers(bose or QSC) covering the entire area for speech,light music &video / OR 4 point speakers(like bose S1 pro in a single loop) in the 4 corners mounted on 6-8 feet high poles. Which of the 2 solutions will be better for echo reduction? Ill be using a 3-4 wireless MIC setup without any DSP for feedback cancellation. Will it be an issue? or do i have to compulsorily use a DSP?

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    I second Laurence’s answer. If you are stuck with this start with the curtains in the back, not the front. The back is where the real echoes come from. The front is where early reflections come from which can be annoying but don’t seem to be the primary concern in this case. – Todd Wilcox Sep 13 '19 at 17:21
  • Maybe you could record the sound of the room as is, and analyze that to check whether there's reverb or echo, and what the problematic frequencies are. This may tell you whether to treat the floor-ceiling or side-side or front-back walls, and whether it needs absorption and/or dispersion. – Your Uncle Bob Sep 13 '19 at 17:38
  • @YourUncleBob - you're going to have to do a lot of separate recordings with mics in different locations to ascertain that. – Tim Sep 13 '19 at 17:39
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    This seems like a very constrained situation. Are you approaching it as a musician or speaker, or as an audio engineer or structural acoustics engineer? My first suggestion would be to cover the walls in some type of soft carpet like wall covering, someone mentioned curtains. If the room is full the people will cover the floor so that's not as big a problem. Is there fixed seating, desks or tables, or would the room be set up different for each event? That will drive solutions as they can be different for each situation. – ggcg Sep 13 '19 at 18:22
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    Also ceiling speakers will be better than regular mains for controlling the sound field, but I’m not sure how you would buy, install, and maintain them on a tight budget. If you can afford feedback cancellation, then you should get it. Basically, the budget will control the quality of the system. If you spend less, you’re going to get less. If you hire pros and buy quality equipment and have it professionally installed, you’ll get a much better system and much better sound. There are no shortcuts and no secret cheap ways to DIY this. – Todd Wilcox Sep 13 '19 at 21:22

I don't think the potted plants will make much difference. The curtains might, but material thick enough to make any difference won't be cheap.

Personally, unless I was an experienced acoustical engineer I'd run a mile from this one. You're in danger of not only failing to improve the sound but even making it worse. You might soak up a lot of the high frequencies leaving nasty lf reflections.

The classic approach to amplification in impossibly reverberant spaces is to use lots of small speakers. It can work in a traditional church where there are lots of pillars to put speakers ON. Not so much use in an open space.

The modern approach might be a line array system. Sound can be focussed at the audience, not wasted towards the ceiling. Again, not cheap.

I repeat, unless you're an expert, steer clear of this one!

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  • Sensible move. Could be chasing rainbows. Would cost way more than budget. +1. Searching for an 'anti-echo chamber'. I've believed for a long time now that there must be a way of producing a 'wall' of anti sound (Such as could be used in open plan offices (what a joke)) and one of those pointed in the right direction/s would do the trick. – Tim Sep 13 '19 at 17:41
  • The future might be in 'silent' systems. Half the audience probably carry personal Bluetooth headphones or earpods already. We already have standardisation on the 'hearing aid loop'. This just needs to be extended. – Laurence Payne Sep 13 '19 at 17:58
  • Yup. +1 My first thought before I even got as far as your answer was "Get a pro." This sounds too big & too much guesswork for a DIY project. It could end up costing several thousand for absolutely no discernible improvement whatsoever. Or you might fix it with a sloped rear stud wall for a couple of hundred… you'll never know without a pro. – Tetsujin Sep 13 '19 at 19:41

To do this correctly you'll need to do acoustic analysis of the room including reverberation times of the offending frequencies. When you have that information you can design and construct bass traps and diffusers to address the problems discovered in your analysis. It is possible to do this kind of thing if you are given a reasonable budget and are willing to study and learn, but often just coming at the problem with nothing more than your imagination will prove to be a waste of time and money. I'm not trying to discourage you if it's something you want to learn about. There are methods that work quite well, but there are no real easy answers and you will need to know what you're doing. Best of luck.

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Perhaps you could use a combination of diffusers in addition to the sound sound absorbing stuff. I don't know much about these (I just read enough acoustics to set up a small dance band) as they were only developed during the 1970s.

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