Install for new sports hall

[mcpfc]

Hi we have a new large sports hall and are about to add a sound system.

We have had lots of varying advice to either: dot lots of small speakers around or go wireless or use a few strategically placed good quality speakers all of these options centrally controlled.

My question is: can anybody recommend a way to go, I understand detailed advice is impossible from my query or is it simply a question of taste vs budget?

Any help much appreciated.

[bruce]

What's the sound system for? Event commentary? Safety evacuation? Zumba (etc) classes? Performance space?

[MarkPAman]

What is the system for? Announcements, speeches, background music, discos, bands, something else?

[bruce]

is there an echo in here? :)

 

(for a sports hall, that's an extremely relevant comment...)

[paulears]

Reflective sports spaces often use a centre cluster - certainly the really nasty places like ice hockey rinks and that kind of place do. Personally I hate multi speaker systems in these kinds of spaces, unless they all have very tight dispersion, and the best ones work well for speech, but musically sound pretty horrible.

[J Pearce]

Paul's comments are worth observing, in a reflective acoustic with a high RT60 and many hard delays a centre cluster pushing all sound out from one coherent source is often far more successful and intelligible than lots of speakers round the outside introducing more echoes.

 

First work out what the system is for, then where you can hang or affix speakers. Work from there.

[Simon Lewis]

My heart sank a little at the words "we have a new large sports hall and are about to add a sound system". Given you are a FE college, let's hope that your designers/builders have followed BB93 or Acoustic Performance Standards for the priority schools building programme, and that the upper limit for the indoor ambient noise level is 40 dB L_Aeq,30min and mid band RT60 is less than 2 seconds. The 1.5 seconds cited in the 2003 edition of BB93 would have been nicer though...

 

Presuming that speech is the prime requirement, if your space is relatively benign acoustically, then the central cluster approach mentioned above can work well, as can a properly designed and set up distributed system. If you have longer RT60 or problems with flutter echo then I would suggest that acoustic treatment (absorption and diffusion) will be as useful as any PA specification, but that you will need to typically increase directivity, reduce loudspeaker to listener distance, ensure even coverage and reduce unnecessary excitation of the reverberant soundfield.

 

So what is the new hall like, and what do you need to achieve?

 

 

 

[kerry davies]

The college spends £44 million on a rebuild and then asks BR to sort out an acoustic problem?

 

Too much gone on the champers for the grand opening, then?

 

Simon has a break coming up, send him a cheque.

[Bobbsy]

Frankly, I'd probably pass this hot potato to somebody else and not even try. Sports halls are notoriously difficult to design systems for and, even with high budgets and highly qualified acoustic consultants, often barely manage intelligibility much less "good" sound.

 

If you must do it, I'd investigate Paul's idea of a centre cluster. What I wouldn't do is lots of little speakers--the more out of time echoes you have floating around, the harder it will be to understand what is being said.

[Simon Lewis]

What I wouldn't do is lots of little speakers--the more out of time echoes you have floating around, the harder it will be to understand what is being said.

 

This is a good maxim - and indeed, one of the equations for calculating intelligibility includes "number of speakers". There are some caveats though... A distributed system may provide some advantage if It is possible to significantly decrease the speaker - listener distance and provide more focussed coverage. There is also the issue that in highly reverberant environments, the usual directional sources (column arrays etc.) may not add as much improvement as predicted. This has certainly been observed by Arup in their work on sound systems for London Underground.

 

The real answer is to ensure the acoustics are suitable first (there is guidance in the standards I referred to). If this has not been followed then all bets are off. If the room cannot be treated, my preference is then to use digital directivity to provide the required intelligibility at listener level, although this could be of comparable cost to carrying out the remedial acoustical work...

[paulears]

It does strike me that the downside to your quest for putting in a sound system that will satisfy the users needs is simply going to be budget. It's going to be a significant capital cost, and unlikely to be within a departmental budget. Even thinking of wireless suggests that cabling has been identified as an issue, when, if this is the case, no thought at all as to infrastructure was designed in at the build stage. If the architect and college team forgot to design it in, a system that has quality and intelligibility is going to be a consultant job, because of the cost implication. If you spend £100 on a system that doesn't work, you can redeploy it somewhere else. Spend 30 grand and it's for good!

[laolu]

I'm not so sure why the "many small speakers" approach gets the thumbs down here. In large churches with tons of hall and echo this approach often leads to a quite intelligible speech coverage. Whereas I've heard center clusters in sports arenas (mostly flown up in the ceiling) that sound awful, for speech and even more so for music.

 

I agree, however, with the poster above on the point of budget: a decent PA is often the last concern the planners have. Sad.

[paulears]

The lots of small speaker approach does work - but only when it puts a single source within a short path to the ears of the listeners, and the next loudspeaker , because of the inverse square law, is perceived as much quieter. The problems arise when listeners hear multiple speakers at different distances at levels closer in level - and the column speakers common in churches can often do this. The time delay begins to impact on intelligibility. This gets worse as reflections also provide strong sound sources. In typical churches, all these things seems to conspire or assist - which one is often down to decent planning or luck! If they are drawn out on paper or viewed on a screen you can often see how the supporting columns often used to carry the speakers, can also serve to block sections of the listeners from a direct path to another speaker. The worst places to sit are often near the aisles, because you can see lots of speakers, and if you can see them .......... quite a few now subscribe to the single cluster speaker system too, with a central speaker cluster, but often these just can't be used if the building is architecturally significant, or just looks nice! In practice you have a choice in the midrange and HF - you can have a conical dispersion pattern, or as in a column, have a wide and height limited version. These, plus sound treatment to try to stop the room spoiling things are really the only tools. Selecting the right combinations is the skill.

[Bobbsy]

Indeed.

 

As Paul sums up nicely, the "lots of small speakers" approach can work in situations where you can carefully plan the spacing to get one speaker close to a block of crowd/congregation and the next speakers far enough away for the inverse square law to make them very quiet. It also works best where you can keep levels nice and low.

 

This makes it work quite well in churches, particularly older ones with, for example, lots of pillars. I've also used similar for front fills or under balcony fills in theatre situations--a row of tiny speakers outputting a low SPL.

 

However, any of this is much more difficult in a sports hall. These tend to have 4 walls and a high ceiling--with no place in front of spectators to hang speakers, at least not close enough to keep levels down. Wall mounting puts the sound source behind the spectators, something I try to avoid.

 

Frankly, I'd rather put hot pokers in my eyes than do a system for a sports hall though...

[paulears]

Anybody attempting to put their name on a sports hall install is on a hiding to nothing. To get a perspective that everyone can understand. Stick a portable stereo on the floor, in the middle, turn it up with some speech content and let everyone involved with funding the system hear the room, before you plan anything. Only then can you guarantee that they will appreciate what you have done when complete after spending thousands of pounds on something that still sounds poo, but just a little less than what the original did!