Getting the best results from foldback systems.

Getting the best results from foldback systems.

If you are a musician who is likely to play on a stage with a substantial fold back system this could be one of the most significant articles you will ever read.

It is very important that musicians understand the limitations of fold back systems so their expectations are contained within the limits of the system they are using.

If they are able to acquire a similar sensitivity to the sound engineer as to exactly what is going on, then they will be on the same wavelength as the monitor engineer who is sometimes attempting to do the impossible. He has a hideous job to do and believe me that is no exaggeration at all.

The fold back system has to compete with the backline equipment which often tends to be extremely loud. So loud in fact it has been measured in some cases to be over 125 decibels! The threshold of pain is said to be around 118 db, so 125 db is very dangerous indeed and easily capable of causing permanent hearing damage and serious tinnitus. Tinnitus, (a continuous ringing in the ears) has been known to cause severe depression and in some cases has even led to the sufferer committing suicide. Musicians who are rightly concerned about this affliction wear earplugs in an effort to avoid hearing damage which is somewhat weird. Why turn up to dangerous levels in the first place? It simply doesn’t make sense!

Having said all this, you need to try to understand the unfortunate relationship that microphones have with loudspeaker enclosures. They don’t like each other at all!

Between the microphone and the loudspeaker is a thing called an amplifier and this device causes gain. If the gain tries to rise above a gain of "one" which is also known as unity, feedback will inevitably occur.

In order to maximise the available level, the monitor engineer has to rely on devices called graphic equalisers to flatten the frequency response so there are no peaks. Peaks cause feedback so we try to eliminate them if possible. They are caused by the microphones and loudspeakers themselves and also the environments characteristics.

Once the system has been equalised the monitor engineer works out how far up he can push the volume level before feedback occurs. He then has to contend with the backline level and hope it doesn’t alter once the band starts playing.

Sometimes singers like to take the microphone out of the clip and hand hold it as part of their visual act. This of course makes changes to the environment that often results in peaks that come and go with the movement of the mic. The worst of which occur when the mic is pointed directly at the wedge. This is a huge no! Not only can this blow horn fuses instantly but it can also permanently damage cone speakers through excessive heat. The uneducated don’t think about this and almost never have to pay for the damage that results.

Altering the dynamics is another serious issue. Often the system is right on the verge of feedback so if the level of the backline increases, the vocalists may no longer be able to hear enough fold back to stay in tune and pitch correctly. The monitor engineer is forced to try to squeeze more level out of an already over pushed fold back system and a painful burst of feedback is the result. He then gets abused by the vocalist who does not understand the situation due to ignorance. It is impossible to achieve the impossible.

During the setup the stage crew will try to ensure all the microphones are facing away from the monitor loudspeakers. Sometimes this is difficult as in the case of drum mics because they all face inwards so at least one must end up facing towards the drum fill. The answer is not to fold this mic back and if it is only the floor tom mic this won’t really matter.

Holding the mic correctly can also help reduce the incidence of feedback. The microphone characteristics are seriously altered when a vocalist wraps his hands around the mics pop filter. He may think it looks cool but the practice is stupid and can cause feedback at any time without warning.

Keeping the mic close to the lips without actually eating it can raise the vocal volume level without increasing the risk of feedback. However when the mic is pushed against the mouth low frequency overload can occur making the voice sound muddy, boomy and undefined.

Positioning the floor wedges correctly makes a big difference to their output efficiency. They should if possible be square on to the recipient or "on axis" as it is correctly stated. If you can see the horn behind the grill, the performer using that wedge should be looking directly into it. Any angular setting should be avoided, either forward or back or side to side.

If you have control over the equaliser settings a bright sound will project more clearly than a dull or more bassy sound but care needs to be taken with high frequency boost because if overdone it will cause serious feedback. It is better to cut the lows than boost the highs.

Most high quality wedges with a 1 or 2 inch horn and a 12 or a 15 inch cone speaker can easily achieve an output of over 130db at 1 metre and they can exceed the threshold of pain with an input of only 8 watts! Professionals would normally drive a bi-amped wedge with a power amp capable of producing 1000 watts RMS per channel or more. We do this to avoid the clipping or distortion which can damage our loudspeakers, so you can imagine what this combination can do to the delicate components of the human ear. It doesn’t bear thinking about.

In this situation ear plugs are essential hardware and anyone not wearing them is literally committing hearing suicide!

Acoustic drummers are without doubt the prime cause of all monitor difficulties and are also the only ones who can remedy them most effectively. All they have to do is back off.

The drummer’s intensity, causes the bass player to lift his volume so he can hear himself. Most bass players stand next to the drum kit and synchronise themselves with the drum beat. This is good; this is what rhythm sections are meant to do. This is what makes a band sound tight. No problems here but if the bassist can’t hear himself, then this is where all the problems originate. THIS IS WHERE THE VICIUOS CIRCLE ALL STARTS! The supposed solution is for everyone to turn up! The end result is permanent hearing DAMAGE!

Or you could get lucky and just suffer a lifetime of tinnitus!

 


Stage Sound Enterprises

Stage Sound Enterprises Ltd
Unit 4-77 Porana Road, Glenfield, North Shore, New Zealand
Phone: 09 444 8776 Email: info@soundman.co.nz
Opening Hours: Mon-Fri 9 AM to 6 PM