- When sound waves enter a microphone, the pressure creates vibrations on a diaphragm.
Attached to the diaphragm is a coil winding positioned in a magnetic field. This is basically just like a speaker – only in reverse.
- Vibration of the diaphragm causes movement of the coil in the magnetic field that creates voltage.
- This voltage is modified and amplified at various stages and only becomes sound again when applied to the voice-coil windings of a speaker.
- Application of voltage to the speaker coil windings creates movement in the magnetic field and vibrates the speaker cone (or diaphragm), which creates sound pressure level.
This is a somewhat simplified version of what happens, but the important point is that in any sound system, Hi-Fi or pro-audio, what is being processed is electricity, not sound. Every component in a system is sensitive to input voltage and the voltage level it outputs has a direct impact on the next device in the signal chain. Too high a voltage at any input stage is harmful to the system. The result is poor sound quality and, eventually, component damage.
Speaker Hospital has all the necessary electronic test devices to run a full operational analysis of any sound system. We can test and read systems at every point in the signal chain and provide a full written report of the results. This information can be used to optimise the performance of any sound system and help avoid damage and unnecessary repair costs.
Six months later, the same client was back with his speakers in a similar condition to the first time. This time, we suggested he bring in his amp and pre-amp as well. Even though neither unit had faulted, we knew something had to be wrong for this damage to occur again.
The amp and pre-amp were of the same brand, and he had purchased the entire system at once as a “matched system”. We inspected both units and found evidence of the previous amp repair. Although non-original parts had been used, they were of the correct values, and the work had been done well. Neither unit, when inspected individually, had a problem.
However, when operated together, our analysis showed that setting the pre-amp volume control past one o’clock produced a distorted ‘square-wave’ output signal. This is what had caused his power-amp to fail in the first place and was also the cause of both occasions of speaker component damage. For this particular pre-amp, the ‘full’ volume setting was actually at halfway – allowing for varying volume levels of program material without distortion.
The client went away with a fully functional sound system, once again, but this time he also knew exactly where his maximum settings were. It was well over a year before we heard from him again and that was a phone call to say that the system was functioning perfectly, sounding great and when he wanted it loud he got it louder and cleaner than ever before – with no damage.
The first thing we ascertained was that his D. J. mixing desk was wired to output + on pin 3 of the balanced connection. As the rest of the system was made to receive + on pin 2, this meant his rig was operating with a reversed polarity. His speakers, therefore, were moving backwards when they should have been moving forwards. The result, in terms of sound, being a lack of impact (or ‘punch’), he was running his mixer output ‘hotter’ (i.e. outputting more voltage) than his power amp wanted to receive. This was ‘clipping’ his power amp and causing the speaker damage.
Once we re-wired his desk output to deliver correct polarity we were able to show him his optimised settings for that system. The result was all the punch and impact that had been missing before was achieved with the system running cooler than before. We haven’t seen any speaker repairs from that client since. Excluding unfortunate accidents, he should get a long working life out of his speakers which means more profit for his business.
Having read the above examples, you may well ask why a speaker repair company would provide a service that mean less repair work in the future. The answer is simply:
- This service is not free.
- Pro-audio equipment has a hard life and, due to normal wear and tear, repair will be necessary from time to time.
- We have a commitment to quality sound.