Basic Installation Advice

[Johnno]

I work in a school. A few years ago before I started there the school got some audio company to improve the school hall audio. They did this by hanging a 110W Carlsbro rock-and-roll style speaker cab either side of the proscenium. That was it. I understand they charged the school quite a bit for it. And since the cabs hang over the stairs leading onto the stage anyone taller than 5ft 5in (me for one!) risks banging their head on the darn things. Also by being on the proscenium wall they are behind anyone using a mic on the stage apron. I'd like to say that I'd appreciate some feedback on this but I already get plenty, ** laughs out loud **.

 

Anyway, that's water under the bridge and I need to address the future.

 

As a temporary no-cost measure I'm going to move the speakers forward of the stage.

 

What I'd like to know though is what sort of sound system I should be thinking about. Our hall is about fifty feet by sixty-six, sixteen of which is the stage, and it has an eighteen foot deeply ribbed ceiling. What sort of price would I be looking at for a competent installation engineer to come and measure the hall's acoustics and specify something that would work?

 

I hesitate to mention Bose (£££££££££££££££££££££££££££££££££££££££££££££££ ;) ) but I went to see my darling daughter singing in a concert at the local Sally Annie hall and their (Bose) installation sounded glorious. You could hear every word. Verily doth the Lord reward the faithful with mighty PA! The speakers looked sexy too, a sort of curvy white box.

[paulears]

Plenty of people seem to have a kind of seizure when people menation Bose, but I'm not one. They do have a characteristic sound, and people do seem to love it or hate it, but they have some great products - I guess the one thing they aren't is rock and roll, and they do need careful set up to stop people accidentally abusing them.

 

To be fair, the 'bung a pair of disco cabs up on the pros wall' is very common in schools, and often is all they really need. The questions that arise are these.

 

A decent acoustics survey will show lots of hard parallel surfaces. Acoustic treatment will be required. The budget for the consultant and treatment will be expensive, and a teacher will say "the old one sounded good enough to me - why don't we just buy another set and stick them the other end instead?" All around the table nod, and the technician gets the job of adding equipment that make the problem worse. That really does happen - lots!

 

What benefits will a better system bring?

 

How long will it last?

 

Do we need specialist skills to keep it working.

 

 

Schools are very different from any other typical user.

 

One word of warning. Beware any 'consultant' who can supply kit - not a good start, as they'll have favourites, or preferred brands, or other similar bias.

 

Many schools, if they have the height, would benefit from a centre cluster, rather than wide spaced boxes - but fixing it, without a suitable beam at the right point may be awkward - hence why wall brackets are so popular!

[Bobbsy]

Sorry...be with you in a moment. I'm just busy having my anti-Bose seizure!

 

Ah, I feel better now.

 

Right. Paulears has given some good advice. It will likely be a hard sell, but your best bet will be an truly independent consultant. Beware anyone who can actually sell you gear...he's a salesman, not a consultant. The real consultant will be able to evaluate your needs and your room (and your budget!) and write a specification you can send off to installers for quotes. He can then help you evaluate the responses and, if required, even project manage the job.

 

As for details of what you need, that's pretty nearly impossible without seeing the room. However, in general terms, there's a big difference between professional speakers and generic Carlsbro-type things. Pro speakers have known, published dispersion angles which control (at least at higher frequencies) where the sound goes. By specifying them properly and then aiming then accurately, you can ensure good coverage of the whole audience but keep most of the sound off the stage, walls and ceiling. Couple this with some acoustic treatment of the room and the improvement will be stunning.

 

As for how long a good installation will last and what care it needs, well "it depends". In a school install, probably the biggest issue is keeping the student "Head of Sound" away from things! Properly installed and pointed, the speakers shouldn't need touching. Similarly, if the system includes room EQ (see some other threads about whether or not this is a good thing!) that should be locked away once adjusted and not touced either. Given those two things (and properly specced amps/speakers with adequate protection circuits) and there's no reason things shouldn't last for years. My very first system (Celestion speakers and some ancient Crown amps) is still working fine after more than 25 years...despite a lot of humping around.

 

One site that may provide you with some ammo when you hit the "why do we need it" wall might be THIS ONE. Don't be put off by the reference to churches...the same basic principles apply to what you want to do and Jim Brown is a respected professional in the industry (albeit in Chicago so not much good for your job!).

 

Good luck!

 

Bob

[Johnno]

Thanks for those comments.

 

The school Head is aware of the problems we're having with sound and so I should get managerial support (not to be confused with managerial money).

 

Unauthorised dabbling is not likely to be a problem.

 

The Drama Queen wanted me to set up another pair of speakers at the rear of the hall pointing forwards for the last show she staged. To make it louder, she said.

 

If it really is just a case of spec'ing a couple of better speakers I can do that myself and put money saved towards better gear. I thought a pro audio chap might be useful as the present setup suffers from unintelligibility. Unless it's just my old untrained ears

[Bobbsy]

If it really is just a case of spec'ing a couple of better speakers I can do that myself and put money saved towards better gear. I thought a pro audio chap might be useful as the present setup suffers from unintelligibility. Unless it's just my old untrained ears

 

Er no. Better speakers will certainly be part of it but just buying two different speakers is NOT the solution.

 

As Paulears said, acoustic treatment of the room is likely involved, as is working out the safe engineering required to position and hang the speakers you end up with.

 

Depending on the size of your room, the sort of pro (i.e. directional) speaker I mentioned will almost certainly require multiple boxes, each precisely aimed to cover it's own specific part of the audience. The calculations for working this out are not for beginners. Once you get into multiple boxes, you're into the realm of speaker controllers which have to be set up properly. Oh, and as your existing speakers are only 110W boxes, you will probably need new amps too.

 

Sorry if I wasn't clear, but my previous post wasn't saying "buy better speakers". I was encouraging your idea of an independent consultant.

 

Bob

[Beanzy]

For my tupenn'orth, I agree with Bobbsy. More speakers but smaller target areas will give your audience a much more comfortable listening experience, with everyone receiving approximately the same volume across the venue. The problems most people find with the small/many approach is that you'll need to design the wiring and layout to take account of interference patterns, reflections/delays and higher cost. As the volumes will be proportionately lower the reflections can be sorted easily enough by the acoustic treatment of the room, curtains and drapes etc. The interference patterns can be attenuated with local baffling 'flags' close to the unwanted source to attenuate sound travelling towards the desired source. As the system will not be pumping out large volumes you suffer less from feedback

 

A system like this will be more expensive than the single amp big speakers solutions normally used, & how do you convince them that you'd get rid of the existing speakers? However there is a real advantage for those putting on the show in that the audience reaction in a venue like this remains much more audible. This can help make the whole venue seem more intimate than a large speaker high-volume system. In its simplest form you can go for the church approach, where the speakers are mounted in evenly spaced rows projecting at roughly 45degrees towards the rear of the venue, but mount them at a convinging level so it's not doing a 'Dr.Bob' (the muppets) and coming down from on high. Comedy club and pub venues really benefit from this approach too, with the added advantage that you can provide zones with different audio levels.

[saturnx21]

Hi all

 

Being an installer myself the first thing I would need to know is what you would be likly to use the pa for, also there are many ways of geting round the acustics problem but the simplest and cheapest is to arrange "sails" in certain locations. it must also be considerd that the suggestions of multiple cabs mounted in arrays would probably be best it is likly to be very expensive.

 

oh and when I quote for an install I dont just sell thye customer the highest priced kit! I find it much better to sell them the best compromise between the best equipment and cost this way I get much better customer satisfaction and more contracts arrive through word of mouth!!!

 

hope that makes sense as its bin a long day!!!! :P