This article originally appeared in the December 2000 issue of Pro Sound News. Innovations is a monthly column in which different pro audio manufacturers are invited to discuss the thought process behind creating their products of note.
After launching the groundbreaking Axi2050 compression driver, it was clear that a custom-designed horn would be required, enabling the driver to achieve its potential bandwidth of 300 Hz—20 kHz so it could be demonstrated to customers!
At the Frankfurt Pro Light + Sound 2017, Celestion first showed the Axi mounted on the “Big Red Horn.” This horn was a SEOS-type that was off-the-shelf, but paved the way for the creation of bespoke designs and a new mission for the company.
What was particularly notable was the number of people who asked where they could buy a similar horn, or have one designed for them. These weren’t just casual enquiries, as they came from well-respected Pro Audio companies.
It was clear that horn design was a necessary skill for the company to develop further. To its highly skilled R&D team, Celestion added Bjørn Kolbrek, an engineer who had spent an extended period researching horn loudspeakers. (He also recently co-authored the book High Quality Horn Loudspeaker Systems).
The Partnership Principle
Celestion’s approach to R&D frequently involves working closely with engineers from client companies, often over long periods to create innovative solutions that are deployed in new sound reinforcement products.
The Celestion R&D team’s in-depth knowledge of horns and experience of finite element methods resulted in the creation of some very powerful in-house high frequency horn design software.
This enabled Celestion to assist where the customer perhaps lacked the niche expertise for horn design, or where the partner company’s engineers could not devote time to the often long-winded, iterative design process that previously would have been the norm.
Bespoke Horn Design Software
Designing a horn for a specific application requires knowledge and experience, but it is also greatly helped by good simulation tools that are both fast and accurate.
Celestion’s main tool for day-to-day design is similar to Finite Element Analysis (FEA) but each piece—or element—is much more complex than elements used in FEA. This speeds up the simulations to a level where each iteration can be computed in the matter of minutes for three-dimensional horns (compared to several hours for full 3D FEA). The method has been validated using both FEA and measurements—and it works!
A horn design tends to start from a set of specifications and requirements. From these, an initial design can be put together within the software to evaluate what can be achieved within the specified constraints. Measured data can be used for a specific driver, to get an accurate picture of how the driver and horn combination will work.
The specifications can be adjusted or, if the initial results are satisfactory, the fine tuning of the design can begin, balancing the inevitable compromises to achieve the best possible result.
Making the Expertise Accessible
HornWizard has been produced to introduce systems engineers to Celestion’s high frequency horn design capabilities. It offers a simple, quick and freely accessible method of testing the likely validity of actual horn designs.
Users can reliably verify designs, quickly adjust them with different parameters and view the results in a matter of seconds.
It’s been created as a WPA (Web Progressive App) so it can be used on both desktop and mobile devices, accessing our full design software using a simplified parameter set. The app itself doesn’t contain any horn design software; it simply acts as a portal, enabling the user to input parameters, and then returns results to the app interface.
While Horn Wizard is not a complete horn simulator, it uses a simplified method to produce a reasonably accurate estimate of directivity and frequency response. First and foremost, it’s a “reality check” to see if particular specifications can be achieved within specified constraints. It also enables the user to see how different drivers work on the horn, aiding in the driver selection process.
OEM customers can create an account to save and revisit many different designs. Once one or more basic designs that look like they may work have been found, Celestion can then take the design and optimize it to fit the target application.
Ken Weller is the product marketing manager at Celestion in the U.K. He started playing with loudspeaker drivers at the age of 9, got his first job in a Hi-Fi store at the age of 15 and has still yet to escape the world of audio, having previously worked for Tannoy and Bowers & Wilkins.
HornWizard • www.celestion.com/hornwizard