A lot of time and energy is required when designing a loudspeaker. The manufacturer must ensure that the desired sound quality exactly meets the speaker’s intended application. From specifying what materials will be utilized, to conducting tests and measurements of the speaker, there are several steps required before it leaves the design lab.
Every design decision impacts how a transducer reacts when it is energized. If the speaker is not vibrating correctly, or vibrating in a strange way, then it will produce unintended, arbitrary sounds that will affect what the listener hears. A laser scanning vibrometer allows for the engineering team to see how the speaker is reacting during its intended use, helping to create an optimal final product.
Design and Testing
The laser scanning vibrometer measures how the speaker cone, transducer, and enclosures are behaving and what happens when sound is emitted from them. It does this by playing a frequency sweep through the speaker, while using a laser to measure point by point and atop the speaker part being scanned. This data is then reconstructed into a 3D model to see how the speaker is reacting at every frequency.
Distributed by Klippel, the laser sensors are based on the optical triangulation principle. Once the laser impacts the object, the light rays that reflect from the target object, impact a position sensing device (PSD). This reflected light will vary depending on the displacement of the target object. By looking at the light fluctuations, the sensor can then measure the displacement of the target object. If anomalies are encountered the speaker will then undergo design changes before it is released to production. Product consistency is critical for quality sound.
Speaking of sound quality, transducer soft parts can distort in unexpected ways and can present as ripples, twists, rocking imbalances or a buckling movement within the speaker's diaphragm, surrounds or spiders. Laser scanning helps the engineering team take a deeper look at what is happening and at what frequency. While material distortion is an inherent property of any transducer's soft parts, it must be ensured that those anomalies are happening at frequencies that are not critical to the sound quality of the speaker's intended use. Additionally laser scanning is used to verify the consistency of manufactured parts from one batch to another. Without consistency, delivering great sound quality on a regular basis becomes impossible.
Performance Testing and Measurement
Each speaker application has its own required level of testing and measurement. Ask your speaker manufacturer if they integrate laser scanning as part of their RnD and quality process. At MISCO, not only do we employ laser scanning, our labs also employ these exceptional tools in our quest for consistently great sound quality and value:
Klippel analyzer systems
Klippel Near Field Scanner (NFS) for anechoic measurements
Klippel SCN and Near Field Add-on for 2pi measurements
Klippel vacuum chambers for testing micro speakers and tweeters
Oversized IEC Baffle to test large woofers
5m x 5m filled and grouted concrete wall for infinite baffle measurements
SoundCheck software at End of Line (EOL) and for Quality Control
True Technologies for automated life and durability testing
TestEquity Humidity and Temperature Chamber
Download our Loudspeaker 101 Guide to learn even more about the inner workings of speakers.