Sound and loudspeaker construction problems
Human is capable of hearing audible sound in the frequency range between 20Hz – 20kHz. The lower the frequency is, the longer the wavelength is. The wavelength of audible sound is between about 16 meters (50 feet) to less than 1,6 centimeter (less than one inch). If we had powerful sound source that could handle around 100.000W in audible frequency range it would have been piece of cake. Though, a loudspeaker with these specifications is not able to design and that´s why the modern sound reinforcement systems consist of many loudspeakers that have to cooperate together. Here is a rule of thumb that tells us the distance among sound sources should not be bigger than two thirds of wavelength of the highest produced frequency. If we do not follow this rule there’s going to be certain spots in which the waves of the given frequency from both sources subtract and in result they can’t be heard. This rule stated above can be followed without a hitch at lower frequencies because each of the loudspeakers is easy to situate up to 1 meter from each other. In addition we are able to use this rule in directioning of low frequency energy (It will be detailed later). However major difference is in the middle and high frequencies. A treble loudspeaker can’t be positioned in the way so that its distance from the others would be less than 1 cm. These troubles can be solved partially by not allowing treble drivers to tamper with one another. Horns (wave–guides) meet this purpose. These devices are funnelish extendors attached to loudspeakers that limit the radiation of the loudspeaker only to exact defined direction. Wave–guides designing is the toughest task at audio industry nowadays. Major part plays a material selection, shape, surface, measurement and a computer simulation. Just a few worldwide manufactories are capable of designing the state–of–the–art technology of waveguides. A badly constructed horn is sure to damage the sound of even the greatest and the most powerful loudspeaker.
Why audience complains about the sound of your venues?
Everyone that pays a ticket to your venue expects spectacular sound either standing nearby the stage or sitting in the side box or in the last tier in third balcony, no matter where the venture is taking the place – you can imagine whatever place you like – such as at a hockey hall, in a meadow or in a gothic cathedral. Everyone that goes to see their favorite star awaits that sound they hear will approach studio CD quality. All these cases are sort of hard to accomplish and these are ideals that can be just approached. OteSound deals with sound design preferably. We choose for you the best configuration possible with the help of Meyer sound components (line-source, point-source, point-destination and/or its combination) for the main PA and we use necessary fill loudspeakers (front-fill, in-fill, side-fill, delay-fill, etc) so that the sound was wherever the listeners were they and nowhere else. That complex system needs a special measurement instrument and especially an experienced engineer that makes the opposite physical laws come along together. The result you should reach is that the minimum of listeners will complain about the sound in your venue.
DEALINGS WITH LOW FREQUENCIES
Option no. 1 – GRADIENT (CARDIOID) CONFIGURATION:
Add loudspeaker at both sides and turn it backwards to the stage. The fact that the sound is subtracted at the stage and added at the auditorium is achieved by using multichannel loudspeaker processor. This setup doesn’t solve the dead spots in the auditorium, but it helps significantly decrease noise level at the stage. This way, the overall sound is much clearer, the PA system is less vulnerable to acoustic feedback and musicians feel more comfortable.
Option no. 2 – END-FIREING:
Set loudspeakers into a line in the way that the rear ones emit their sound energy into the front ones. All in all it’s able to achieve the similar outcome as with cardioid configuration. Rear-fireing configuration is capable to get a little higher sound pressure than the cardioid configuration does. But it has one drawback – a larger space demands.
Option no. 3 – GRADIENT LINE ARRAY:
Place loudspeakers side by side in the middle of the stage. This arrangement uses minimum loudspeaker spacing so that they act like one source. There’s a big advantage – no dead spots are occurring.
Turn 2nd and 5th loudspeaker in the opposite direction and get the effect of cardioid configuration. This way, stage almost gets rid of the ballast sound. This is considered to be an ideal solution. Although, there is a down side here, naturally. Sound pressure level in an auditorium is lower and there’s a demand for a lot of space and there’re problems with PA/SUB crossover aligment.
High-frequency drivers can’t be placed too tight so that dead spots won’t occur.
Horns help us to deal with this issue. Horns do not allow the treble drivers to tamper with one another.
A number of wide horizontal coverage loudspeakers placed not far from one another in order to increase system volume level is a common widespread mistake. Because this way the treble loudspeakers are being affected by each other. There’s going to be certain spots in which the waves of the given frequency from all sources are subtracted or added and as a result the sound coverage is very uneven.
Here is a comparison with four pieces widespread loudspeakers and Meyer JM-1P system. Power capability of both systems are aprrox. 10 000W.