Tips for servicing your speakers

by Andrew Bishop

Great reputations can take decades to build but losing sound at a gig due to no servicing of your equipment can cost you dearly.

On the face of it, you might wonder why speakers need servicing at all, but think of a loudspeaker as a motor - it has moving parts and they will need checking for wear and tear and, just as importantly, so do the boxes they come in!

First, remove the grilles and check all the driver bolts are tight (tighten the speaker woofer retaining bolts in the same way you tighten the nuts on a car wheel) especially subwoofer drivers that take a pounding. Tighten the driver so that the foam behind the basket is compressed and then another half a turn. Go easy on chipboard or MDF baffle material, plywood will take more. You will hear the spiked captive tee nut biting into the wood. If you cannot get the tee nut to bite remake the holes and twist the driver slightly so that you are fixing to fresh wood.

Blow out any dust with a compressor or vacuum cleaner. With both hands, splay your fingers wide and gently, evenly press down, 3 times on the paper cone on the driver about 5mm and listen for any noise. If it's scratching you may have a tired driver call Andrew on 01765 698233 for advice.

When you have done this, check the foam gasket between the cabinet and the grill is in good shape, if not you can replace this with a sticky-backed foam strip (often used at a draft or window excluder) and replace the grill and ensure it is screwed on tight and that there's no movement likely to produce rattles when the speakers are powered. Next, take the backs or handles off and look at all the internal fastenings. Are they secure? Every time an enclosure is taken out of storage, put in a vehicle, transported to a gig, unloaded and stacked then driven at high volume, it is subject to changes in temperature, humidity, and constant vibration. So check all the screws and bolts to make sure they are tight. Look at the connections. Are the wires firmly soldered? Are there any signs of corrosion on soldered joints? There shouldn't be and they should be properly re-soldered if there are.

Fortunately, crossovers and other electronic devices more or less look after themselves until they develop a fault, in which case they may need professionally replacing, but the same isn't quite as true of loudspeakers. You may have seen bed manufacturers telling you that any bed that has had eight or so years of use should be replaced due to wear and tear? Well, I wouldn't put a fixed lifespan on a loudspeaker but it will wear out, eventually - especially if it is driven by an amplifier clipping into a distortion or if it is being by being driven with far more power than it was designed to handle, in which case you can expect trouble sooner rather than later!

However, even a correctly driven loudspeaker will eventually show signs of wear. The most common problem is with the speaker's suspension. Typically, a suspension system includes a fabric spider at the rear and the (usually foam) speaker surround. Put simply, the spider connects the diaphragm to the frame, while the foam suspension keeps the diaphragm centered and enables it to work like a piston, in effect pumping air. There isn't much you can do in the way of servicing a speaker but do look for deterioration in the speaker surround, which is easily visible.

Even the speaker's paper cone is subject to wear and tear through a phenomenon some experts call 'roaring'. This is due to the natural degradation of paper which takes place over time as the fibres are subjected to stress and variations in moisture (one of the many reasons why you shouldn't store your speakers in a damp environment!). Wear and tear on the cones and suspension tends to be either catastrophic, which you will immediately notice, or so gradual that you may not realise it has happened until it strikes you that your system just doesn't sound as good a sit used to, or if you get the chance to do an A/B comparison with a brand new example. Professional hire companies often retire their speakers after 5 years of hard use and replace them with new ones, or at least have their speakers refurbished. BishopSound replacement speakers are very affordable and well worth considering as replacements for ageing systems that have started to sound tired and past their best!

The newer the driver the crisper the sound! The paper cone starts to decompose from the day it is made, it's biodegradable.

Finally, and most importantly, don't forget PAT testing (it stands for Portable Appliance Testing) which is a legal requirement in the UK. Under these rules, electrical equipment used in commercial applications must be tested for safety. There are few hard and fast rules for when and how this must be done but commercial venues are increasingly likely to require that all electronic equipment used in them must have been PAT tested and that will include amplifiers, mixers and powered speakers. You can find out more on this subject on the Health and Safety Executive's website here: The last thing you want is to turn up at a gig (it could be a club, a pub or a council-owned hall) to find that 'Health and Safety' won't let you set up because you can't prove your system has been PAT tested.

Therefore, in summary, here are the Top 5 PA Speaker Service Tasks

1. Disconnect the speaker from power or amplifiers and remove grills and tighten speaker bolts in the same way you tighten a wheel nut on a car.

2. Blow out any dust, especially in the horn where the HF compression driver is located.

3. Remove handles and backplates blow out any dust or debris and check all connections.

4. Remake the driver connections as oxidation can occur on bare cable ends.

5. Replace all handles, backplates, and grill ensuring every nut bolt and screw is tight and PAT test.

Finally, once you've checked everything inside and reassured yourself, it's worth taking a look at the outside of your cabs and trying to repair dings and scrapes so that your kit looks as professional and polished as it should.

Later this year BishopSound is introducing a uniquely formulated spray paint for refurbishing our enclosures - but more of that later!