Extreme reverb problems

[Dj Dunc]

Hi all again.

 

I was just watching the school dance dvd, and found that the people that ran the sound and lighting are going to uni. As resident technician (is that good or bad :unsure: ) I thought it would be good to volunteer my services. I was thinking about this ahead (its next year) , but the major major problem is that the venue (our new sportshall approx 10m high by 50 by 30) is a reverb heaven, and when you say something, you hear four echoes :( . I was just wondering if it is possible to somehow put a reverb fx into reverse, and so balances the sound out somehow, or some other way, as it is not viable to bring in sound dampening. All that is amplified is a hundred or so CD tracks, and a radio mic. The speakers are good quality, but non ajustable, as they are in steel guards to stop damage. Any ideas people? :)

 

Thanks

 

Dunc

[Brian]

In a word 'no'; you can electronically make a dead room lively but not the other way around.

[Big Dave]

Unfortunately, unless you apply acoustic treatment to the room, you are stuck with the reverb. However, it is possible to produce reasonable results in highly reverberant venues. There are several London venues that have RT times of between 5-7 seconds that are regularly used for large events and the sound works in there - but there is an art to it.

 

Without more precise details of the system you have and the control you have over it then there is not much more advise I can offer.

[Dj Dunc]

I will be using two cd players / three into a mixing desk through the amp into the sound system that is installed in the hall. there is four speakers, one at each corner of the half of the hall that is used. The amp can be changed, and the whole system will be flexible apart from changing/moving the speakers. Ill have a look at the exact make of the speakers, but the mixer is most likely to be a behringer mx3282a, or a yamaha emx5000. the amp is variable.

[Bobbsy]

I'm not trying to be funny when I tell you that the biggest part of controlling reflections in a room where you can't change the acoustics would be....moving or changing the speakers. There are literally entire books about this topic, but basically the skill is to use speakers with a known/controlled dispersion pattern and point them to hit only the audience and not the reflective surfaces. If you really can't move or change the speakers, then the biggest tool in your arsenal has been taken away from you.

 

Bob

[Soundie]

I guess it sort of depends on the style of music you are working with, but with a long reverb time it is usually a good idea to use the ambience to add to the sound.

 

By that I mean that you keep the level down and think of filling a small space with the re-enforement and then let the acoustic carry the sound.

 

I did an event in the Dome of St Pauls Cathedral a month ago (the reverb time is HUGE, at least 12 seconds I think). I worked really hard to get the level of the speakers just right so that the acoustic of the cathedral could do the rest to carry it and add nice reverb. Needless to say, I didnt use any of my FX unit!

 

The most important thing is to make sure that the people speaking are familiar with the acoustic (they will need to speak slower to be clearly audible) and to use, and trust, your ears in a variety of different seating positions in the room.

[Jivemaster]

Reverb is a property of the room. You have to change the room or the way you put the sound into the room, -speakers and placing. all the line level stuff is irrelevant to the reverb.

 

Sounds like a major investment in acoustic treatment design is called for. Egg crates don't do the job and look rather worse than blue peter.

[Simon Lewis]

From your description, you have a problem with flutter echoes, not just the overall RT60. Some simple large sail type structures can reduce the former. A large area of mid to high frequency absorption will reduce the latter. Unfortunately, this will not give broadband reduction fo RT60 - you may end up with a more "boomy" sounding hall.

 

 

 

Simon

[The Magus]

Your best option would be not to employ the installed speakers at all, and instead to use a temporary / portable system with speakers set up on stands by the DJ - just as a typical mobile disco would be set up.

 

Where a building is very reverberant or has a nasty echoes (as sports halls almost always do) it is inadvisable to have speakers widely spaced - a point source or cluster will minimise the number of reflections, and improve the intelligibility of the sound. If you can't beg / borrow or hire suitable speakers, then I would advise you to use the installed speakers at one end of the building only. Four speakers positioned one at each corner of a large, reverberant building spells acoustic chaos!

[paulears]

Soundies comment about using a venues characteristic sound kind of makes sense. Trouble is that while for music, reverb of the St Pauls type is beneficial, for speech it is dreadful. Churches of all kinds are very difficult venues to make intelligibility of speech work.

 

Sports hall type spaces are much worse because they have parallel walls and ceilings - resonances can be really difficult to work with. Pretty well the most common aid is drapes - the heavier the better. The more you can soak up the better. If your PA 'fires' towards a drape, it will reduce the reflections to some degree, but as has been said, putting in a designed sound system can only help too.

[OB2]

I very recently provided the noisee for a couple of events in york minster - recorded to have the longest reverb time in eroupe (supposeddly) one of the event was a theatre piece and the other was for a service - but with a band playing rather than organ.

what we did was just used LOTS of speakers all running relativly quietly, so the minster would carry a lot, and it worked pretty well, but there was obviously a lot of reverb to argue with, you coudl still hear pretty clearly, one thing I found, it could just be the acoustics of a church/ cathedral rather than a sports hall, but I ended up taking as much of the low freq. out as I could - with out taking away from the warmth of the sound, this was fine for the theatre piece but once I got a band up there, the bass guitar and the drums proved to be a bit more difficult, but again just running it relativly quietly - difficult with over 1000 people all singing along and combating that and the natural reverb was well it was a fun evning anyway!!!

[Andrew C]

Churches of all kinds are very difficult venues to make intelligibility of speech work.

Which is why.........the clergy............all talk................like this. If you see what I mean...

[Simon Lewis]

Long reverberation times are usually seen as one of the main causes of poor speech intelligibility. Although strong late delayed reflections is listed as a secondary cause in Peter Mapp's list below, chronic cases can be more problematic than reverb alone.

 

Here are the primary causes:

 

Sound-system bandwidth

Sound-system frequency response

Loudness

Signal-to-noise ratio

Talker enunciation and rate of speech

Listener acuity

Direct-to-reverberant ratio

 

and the secondary ones:

 

System distortion

System equalization

Uniformity of coverage

Presence of very early reflections

Sound focusing or presence of late or isolated higher-level reflections

Direction of sound arriving at listener

Direction of interfering noise

Gender of talker

Talker vocabulary and context of speech

Talker microphone technique

 

The typical "hierachy" in system design is as follows:

 

Point Source (clusters, arrays, line sources)

Multiple Clusters (Left & Right, Left-Centre-Right)

Cluster plus Satellites (delayed to main source)

Left / Right loudspeakers plus delays

Distributed System (columns / ceiling loudspeakers)

‘Pewback’ systems

Headphones

 

As the reverberation time increases, so the designer is forced to move further down the list!

 

Simon

[Mr.Si]

Here are some links to photos I took (admittedly not the best photos in the world) of an event where I had to provide sound reinforcement in a sports hall. The client wanted the hall so that the long wall was the focal wall with the stage against it. One thing I was glad about was that the blockwork walls were not painted, so they had some porus nature and didn't reflect all frequencies! (this helps).

 

I opted for the lots of small speakers running at less sound level, rather than any form of cluster and trying to make huge amounts of sound level travel a great distance etc. This just wouldn't have been practicable.

 

I have to say, this was the time where I've been happiest with the results I had achieved, which I was suprised to find.

The sound sources were primarily speech, for a Christmas Event, but included another famous Christian singer/songwriter singing along to backing tracks.

 

I hired 8 Shermann VX200s but only used 6 of them in the end and stuck 'em on sticks in useful places while trying not to create obstructions for people's sightlines to the stage. This was in addition to the 2 pairs of my own "lesser" unbranded speakers which were put on sticks at the 2 front corners of the stage. So the Shermanns were on a delay unit and I was able to play around a little with the "HAAS EFFECT".

 

Note to DJ DUNC, - research on the haas effect, for your own benefit.

 

I have to very much agree that in places like sports halls, speaker positioning and the "sound design" are incredibly important.

 

Si

 

P.S. links to my photos are below:

 

Pic 1

 

Pic 2

 

Pic 3

 

Pic 4 - a bit irrelevant to speaker positions but hey, I thought I'd include it :D

[Simon Lewis]

That's JJohn, and I claim my £10....

 

this was the time where I've been happiest with the results I had achieved

 

So the theory works then!!

 

Now for all of you needing a little break from your labours, differentiate between the Haas effect and the Precedence effect.

 

The answer will be of use to the OP!

 

 

Simon