Sound Advice for Agencies
Rapid prototyping through SLA (Stereo Lithography) fabrication gives both the engineers and the customer the ability to hear and see the speakers’ true performance in the early stages of development. An extension of prototyping is the opportunity for a low quantity of speakers to be manufactured. There are two reasons for this low quantity test run: One, it gives the manufacturer a chance to make sure that the manufacturing process didn’t alter the sound. Two, it allows a transit company to build-in loudspeakers to test the sound system in-field and inside transit vehicles.
Quality control is improved if the loudspeaker designer/manufacturer controls the whole process – design, prototyping and manufacturing. Many loudspeaker suppliers can’t promise that control because they only provide design or order fulfillment.
Full or partial control of the entire process is an important consideration in the selection of an integrated design/manufacturing company. At one end of the spectrum are the companies that offer only a limited number of off-the-shelf speakers – not designed for transit application – while other companies perform some design work, but do all manufacturing overseas. Very few offer the advantages of both designing and completing the cycle through manufacturing. Loudspeaker design and manufacturing requires specialized equipment, such as custom magnetizers that can charge large neodymium magnet assemblies and robotic adhesive dispensers of high-performing adhesives that extend the life of loudspeakers.
Finally, the manufacturer should offer thorough testing that includes complete audio measurements and electrical and mechanical testing of every speaker. Today’s top manufacturers are using sophisticated software to objectively test loudspeakers for sensitivity, frequency response, polarity and distortion.
Lowering the Cost
There are four primary ways manufacturers can lower costs to the transit customer:
1. Use R&D software to lower the cost of material used in the loudspeakers.
2. Use test software, which helps to prevent defective products from being installed.
3. Supply an integrated assembly that includes preassembled transformer, speaker, grill and enclosure. Preassembled units lower on-site installation costs substantially.
4. Keep a large in-house inventory of parts to reduce the costs of the short-runs that are critical to many mass transit needs.
Formal quality systems and lean manufacturing practices are other ways to gauge whether a manufacturer is committed to keeping costs low.
Buy America Can Lower Costs
Transit contracts may require that components are Buy America compliant, but cost savings is another reason to look at manufacturers that still build speakers in the United States. Onshore production can reduce total procurement costs through smaller lot sizes for customized speakers, shorter lead times, cost coordination and shorter delivery logistics. Plus there are no duty costs and U.S. Customs delays.
Subjectively listening to each speaker as it comes off the assembly line is one way to be sure that you get the sound you want. Using SoundCheck, the world’s leading audio test and measurement software is faster, more objective and a more reliable way to ensure a loudspeaker sounds exactly as the engineer and customer intended.
Loudspeaker Examples
Vocal clarity inside a bus can be achieved with a speaker just 5 inches in diameter (Fig. 1). The shallow internal depth is only 1.7 inches and it’s rated at 15 watts with a frequency range of 60 to 12,000 Hz.
An extremely shallow exterior bus speaker (Fig. 2) has a total depth of 1.56 inches and proves high performance can come in small packages. Its vinyl-impregnated cloth cone is extremely durable and waterproof; and with its low-cost strontium ferrite magnet this speaker is designed to operate in temperatures as low as -67 F and as high as 185 F. Shown with brushed aluminum grill.
Enhanced by a special vandal-proof grill (Fig. 3) this loudspeaker assembly is built for today’s subways. The cone is constructed of a single piece of vinyl-impregnated cloth and a treated tweeter to handle the condensation that often occurs underground. The entire voice coil area is protected by a sealed-linear design. In fact, in testing this speaker, it has survived 96 hours immersed in water without sound deterioration. Rated at 15 watts, it has a frequency response of 50 Hz to 18,000 Hz.
