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Getting The Best From Your P.A.

Sounding good with what you've got


HH Mos Fet power amp range.

There's a strong school of thought in the ranks of knowledgeable musicians that the initials P.A. don't actually stand for 'Public Address'. What they really represent are those magic words 'problem area', because that's what building and running a decent P.A. rig is for most bands.

Once you've just about assembled your individual instruments — heaven only knows a complex and expensive enough business on its own — there comes a time when you've got your first serious gigs lined-up and you decide that a P.A. system of some quality is going to be called for.

The question of whether to hire or buy is worthy of an article on its own and there are, of course, a multitude of arguments why you should hire a system to suit the work you're doing, especially if you can get the same rig each time with the same operators who get to know the sound you want. But costs can be high if you hire all the time (frequently more than you're making from many pub and club gigs, as we all realise) and it may be that you will decide to buy your own rig and gradually expand it up towards the sort of level you'll eventually be happy with.

Surprisingly (as far as a lot of bands are concerned) there should come a time when you wake up to the fact that a smaller high quality system, properly used, will actually sound better (much better) than a cheap and nasty powerful one, operated incorrectly. Even modest sized rigs can be coaxed into performing very well, and here are a few suggestions as to how you might get a better sound out of yours. Followed and interpreted with common sense, some of these guidelines might actually stop you wasting money; money which, at a later date, can be spent on worthwhile improvements.

Perhaps the first question to ask yourselves about your P.A. is do you really need to use it at all? What I mean by that is do you need to amplify every instrument in your band? For many pub and club sized gigs the power generated by a fairly decent backline of amps is quite sufficient. Every signal heaved and strained out of your low cost mixer and speakers is another problem for them to have to cope with and it may well be that you'd get a far better sound if you used the P.A. solely for vocals, acoustic instruments (piano, brass, woodwind etc) and let the guitar and bass amps, and maybe the keyboard amps if you have decent quality ones, do the heavy work of shifting frequencies out into the audience. With careful sound balancing before the gig (and during the gig if at all possible) it could be that this will give you a cleaner sound overall than stuffing every available instrument into your mixer. Assuming, however, that you are intent on your P.A. handling all your sounds, the major thing is to watch is your volume level. There is a natural tendency for sound pressure levels to be raised throughout a gig — especially if you're into a fairly dynamic stage act and sound.

Starting at a sound level near the limits of your system, therefore, implies that as your engineer winds up the power towards the end of the set, the clean sound you started with will eventually deteriorate into a mushy mess — leaving your audience with a ringing in the ears — not, perhaps, the best way for you to be remembered, whatever dedicated heavy metal freaks might say!

Jerry Lee Lewis with AKG D330 mike. Inset: Polar diagram for AKG D330BT mike.


An obvious start to getting the best sound from your rig must be the choice of good quality mikes. These needn't cost the Earth but don't try and make do with rubbish — your mike is the vital first link in the audio chain and the extra reliability and sound quality of having a good one will always pay dividends.

Which actual mike you choose is very much up to you and your pocket and ears. The choice of good vocal mikes these days is very wide and there are numerous applications booklets available to help you decide which types to consider. Particularly useful guides are available from AKG, Shure, Audio-Technica and Electro-Voice. About the only golden rule (apart from making certain that you buy the best that you can afford) is to remember that you'll really need a low impedance mike if your cable runs are to be much over about 15ft. to avoid losing all your high frequencies. Use good quality connecting lead, by the way; braided types are best, especially those without spiral windings, which can aid interference noise. Remember also not to use cheap quality three-pin XLR-type or jack connectors either — they aren't worth the trouble! Having got your signal to the mixer in, hopefully, something resembling its original state you next have the problem of grappling with the facilities provided on the desk itself. The temptation for the inexperienced (or just the over-enthusiastic!) engineer is to 'over-play' the mixer, attempting to squeeze every last drop of effect out of the equalisation system provided in an attempt to get the best sound. In fact this rarely pays-off. Most mixers (especially the cheaper types) tend to work best when their facilities are under, rather than over, used.

True, close-miking instruments does tend to alter some of their basic sounds (due to the 'proximity effect' where bass response increases with directional mikes the closer to the sound source they are used) but that's no excuse to whack your Eq controls onto full and then expect a natural sound!

Generally speaking, most small mixers (either proper 'desks' or mixer amps) offer at least three control sections per channel. Remember that each instrument or type of voice (male/female/high/low) has its own character and that your job behind the mixer is to reproduce the sound created by that signal source as faithfully as possible, making up for sound changes caused by close-miking; cutting just a shade of top from vocals to reduce sibilance, adding a bit of mid to them to increase the presence, not trying to make the vocalist sound like someone he or she isn't (desirable though that may sometimes seem!).

Apart from plain old-fashioned distorted and unfaithful sounds, the most common problem bands face with their P.A. systems is that of feedback. The correct and careful use of equalisation can reduce this, as can the use of good quality directional mikes (notably cardioid types). Close-miking instruments will help here too as will, obviously, making sure that your speakers do not mix their sound paths with the pickup areas of the mikes. Make certain that (if humanly possible) you get a pre-gig soundcheck for your band with everything on stage set where it will be during the performance.

Electro-Voice PL77B mike.

Start your soundcheck with the usual individual tests for sound quality and mike placement, especially making certain that there is no amplifier or mixer induced 'clipping' distortion on peaks caused by the equipment straining to reproduce peak levels. Next you can start to use the equalisation you've got. Even a simple two or three control passive type (as found on even the most basic mixer amps) can be used to good effect here. Thankfully modern systems are less prone to feedback than they once were, due to better directivity of mikes and speaker systems and more knowledge on the part of most users. One of the best tips here is to slowly increase the volume of each individual channel until it just begins to feedback.

That feedback can often be switched out then by adjusting the Eq., rather than the fader. Obviously you don't want to alter the sound characteristics of the signal source but you'll usually find that only a small adjustment to the Eq will cure this problem and that'll mean that you are operating your P.A. system at its maximum volume potential — a major gain over merely cutting back level to reduce feedback.

One of the few bad side effects of owning a bigger, more complicated rig is that you then get into the potential feedback nightmare of stage monitors. If feedback is ever going to be a major problem then it's here that you'll find it. Whoever invented the whole concept of the stage monitor must have been a natural-born feedback nut! Think about it and you'll see how it's almost inevitable that stage monitors will generate their sound virtually directly into your mikes — the result? pure feedback! Obviously experience is the best teacher here but there are ways of minimising the problem. One dodge advocated by AKG's expert Norbert Pawera (see the recommended reading list below) is to angle your speakers so that the axes point towards the insensitive side of your mikes. He suggests 180 degrees for cardioid mikes and 135 for hyper-cardioid types.

Assuming that Eq facilities are rather limited on your monitor mixer it may well be that a frequency adjustment to the 'send' won't be possible as it will be in the main mix sent to the front of house. Accordingly, set your levels to the maximum you can get without feedback during the soundcheck, ensuring the overall balance is giving each player the level they need, then reduce each send level to just below the point where feedback sets in. Try covering the mike with your hand too (this helps feedback set in) and then lift the mike on its stand. The cause of the feedback during performance may be mechanically induced or acoustically, and can sometimes be removed by simply shifting the mike around a bit (well, we can all hope, can't we!)

Where instruments are being miked, or players won't be moving the mike around during the gig, make sure that it stays put so that movements don't suddenly induce feedback during mid-set. Tape the stand to the floor and it'll help prevent it being kicked or shifted around by over-excited players!

Dynacord Gigant IIIS P.A. amp.


Of course one of the best answers to feedback problems lies in the purchase (or hire, don't forget) of a decent graphic equaliser. Ideally the main P.A. channels should have access to graphics and so should the monitor channels. The range of graphics on the market these days is enormous but, as usual, you tend to get what you pay for.



"...COMMON PROBLEM WITH P.A. SYSTEMS IS THAT OF FEEDBACK."


Assuming that the guide lines have been followed it remains for us now to look at the much neglected area of the power amp and speaker sections. I'm assuming here, of course, that the mixer you're using is the best you can afford and that it is working properly. This isn't intended to be a guide to buying new gear or better gear — rather using what you have to best advantage — suffice it to say, therefore, that your choice of P.A. mixer (whether it be integral with your amp or not) is vitally important and that it always pays to get the very best you can — maybe even hiring as many different types as possible before buying so as to gain some practical experience about what you want your eventual purchase to do.

Much the same criteria as to the suitability of power amps applies, whether you're talking about separate types or integral ones with small mixers. The main factor must be that you should always try to have enough power on tap to run your amp below its maximum power. Even the finest P.A. amps distort to some degree when run flat-out and so you should always make sure that you have more power on tap than you need if at all possible. Amplifiers driven into 'clipping' start off sounding bad and will often end-up by burning out your speakers' voice coils. The only cure is to use a high powered amp with sufficient 'headroom' (reserve power) so that it doesn't clip at the power levels you need.

This leaves us with speakers. Thankfully the days of the old 4 x 10" or 12" columns are long past (although they can still be pressed into service as makeshift monitors!) and in their place are decent enclosures which are, in most cases, an improvement of one sort or another.

It would be a massive mistake, however, to assume that one P.A. cab is as good as another, however similar they may appear. Construction of enclosures (especially bass and mid types) is an art in itself and a lot can be concealed with applications of vinyl coverings!

Shure PE Series mikes.


Apart from such esoteric considerations as materials, volume of the enclosure, internal acoustic damping and suchlike, obviously the biggest factor in the sound of one cab over another is the type of speaker used and how well matched it is to the requirements of the band and their sound plus the venue. The whole subject of speaker and enclosure design is far too complicated to go in here, but readers will probably be relieved to know that MUSIC U.K. is planning a major feature on the whole subject for the not too distant future. At this stage let's just hint that it'll be something very special and very easy to grasp. For the rest, I'm afraid, you'll have to wait!

One obvious route to improving your P.A. system's sound is to either add enclosures (which is an expensive option and not what this feature is really about, of course) or, perhaps more sensibly, to swap some of the speakers which came with your cabs. Without casting aspersions on most small/mid quality P.A. systems it is true to say that they have been made to compete in a very financially tight market. Obviously this won't usually be done by fitting them with speakers which are actually bad — but it will mean that, on a Pound for Pound basis, most of the speakers used will be of an average quality. Gradually saving-up to replace your speakers with higher quality ones will help enormously.

You might even consider building your own cabs, either to give you a low-cost monitor system or to expand your existing rig. Here you can get invaluable help from some of the better quality speaker manufacturers. Celestion, for example, publish a really first class book on the subject, complete with plans, building instructions and lots of helpful tips. You can get this from most Celestion dealers or (for £1) direct from Celestion. Fane too are, at the time of writing this article, on the verge of publishing a book of speaker enclosure designs and it is to be hoped that, by the time you read this, we'll have seen copies and will be able to tell you about them.

Finally, Electro-Voice publish some really useful literature, and not just on cabinet construction, either. They offer a series called 'The P.A. Bible' which must constitute one of the most useful sources of general help and guidance on PA use we've ever encountered. The 'Bible' has been running for several years now and is worth its weight in gold to anyone using, building or even thinking about P.A. generally.

Going back to your speakers, how you stack them is pretty important too. Assuming that you are using what is the usual minimum these days of three sections (bass, mid and top) the normal practice of stacking them in that order is, generally, the one to follow. Bass sounds tend to be less directional than highs so the bottom of the stack is fine for them. Stacking will also help counteract the problems of volume drop and unpleasant sound concentrations due to overlapping from, say, wide dispersion sounds, colliding and causing phasing problems.

Featured in Celestion handbook (see below)

Experiment with how to angle your P.A. speakers, especially the high frequency ones — don't just stack them all together and expect them to work — find the angles which combine to spread the sound to your audience without phase problems diminishing the sound level and quality. Try to angle those speakers so as to avoid the sound hitting 'live' surfaces like glass in windows, shiny painted walls and suchlike — once these are encountered the sound will split-up and reverberation problems will add more to your sound quality troubles than you can imagine. Try also to check your sound in several places around the venue.

As we said earlier, P.A. can often seem to stand for 'Problem Area' rather than 'Public Address' — but it needn't — the choice is yours. Getting the best from your system is often a matter of skill rather than anything - and it's a skill you can learn, just like any other. Following these tips and learning from other bands and their crews can be a help too — there's no magic involved, just a bit of knowledge, and that's yours for the reading and the asking.

USEFUL NAMES AND ADDRESSES


'Microphone Technique' by Norman Pawera: available from AKG Acoustics Ltd, (Contact Details).
Electro-Voice; distributed by Shuttlesound, (Contact Details).
Shure Mikes: H.W. International Ltd. (Contact Details).
Audio Technica: John Hornby Skewes & Co. Ltd. (Contact Details).
Celestion International. (Contact Details).
Fane Acoustics Ltd, (Contact Details).


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Music UK - Apr 1983

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