Western Electric - Wide Range
- Ceri Thomas
- 18 hours ago
- 4 min read
Updated: 2 hours ago
The Western Electric Wide Range was a huge commercial cinema speaker, released in ...
1931
To set the scene, the best selling car in the US that year was the beautiful Ford Model A, which cost around $500:
The Empire State Building, which was the world's tallest building at the time was completed.
And the most popular cinema film that year was the famous 'Frankenstein':
US cinema attendance was rapidly rising, but just about to be knocked by the after effects of the Wall Street Crash of October 1929 and the more general Great Depression.
Cinema Speaker Design
With cinema attendance very high already and rising rapidly, there was plenty of money to be made in the cinema industry.
This coupled with the fact that cinema sound reproduction was underwhelming at the time meant there was a lot of interest in improving the technology.
From an evolutionary point of view the Wide Range sat between the Western Electric 12A/13A (1927) and game changing Shearer Horn (1935).
The Western Electric 12A/13A, which set the standard prior to the Wide Range had a relatively narrow frequency response of 100Hz to 5kHz and a relatively low maximum sound pressure level (SPL).
Part of the reason for the latter was the drive unit powering the lower-mid horn (13A) was the WE555 compression driver, which though a very good unit for the time, had a diaphragm of only 2" in diameter with limited excursion capabilities:
Wide Range overview
The Wide Range set out to both extend the frequency range and increase the system max SPL versus the 12A/13A.
It was a 3-way system, as opposed to the 2-way 12A/13A, additionally making a step forward by using a 1st order passive crossover.
It consisted of a small horn loaded tweeter section, a large horn loaded midrange section and a large open baffle bass section.
We'll run through each section individually ....
15A Mid Horn
The anchor point of the Wide Range was the 15A horn, which was a slightly scaled up version of the 12A horn, still using the WE555 compression driver. It's frequency range was broadly 100Hz to 3kHz.
The 15A like the 12A was an exponential horn design:
Bostwick High Frequency Horn
The Wide Range used a dedicated tweeter horn running from 3kHz to 10kHz, called the '596'. This was a patented design by Mr Bostwick of Bell Laboratories.
Below you can see a prototype 596:
The patent shows a design very similar to a modern bullet tweeter with an exponential flare and phase plug:
Open Baffle Bass
The choice of open baffle for the bass section today seems surprising. For those not familiar with the concept, it's basically a speaker drive unit mounted to a baffle, but without the standard box that encloses it.
You can see the same concept in the Jamo 909 high-end domestic speaker below:
The quality of bass from an open baffle configuration is excellent, but the BIG issue is that you get sound cancellation where sound from one side of the drive unit diaphragm meets the other.
This limits the efficiency and max SPL of the system. Hardly what you needed when in the 1930's you had limited amplifier power and drive units with limited excursion capability.
Two better routes would have been to horn-load the bass (given both the tweeter and mid were horn loaded), or bass reflex / port. Unfortunately, the patent for the first ported speaker was filed a year after the Wide Range was introduced, in 1932 by Albert L. Thuras of Bell Laboratories (U.S. Patent 1,869,178).
System Achilles Heel
As we've just discussed, the open baffle bass was a problem, but the bigger issue with the system was time alignment (or lack there of)!
The picture below shows the concept. Here the sound from the tweeter would arrive first, followed by the sound of the mid and then the bass. But in the Wide Range the bass would arrive first, then the treble and then the mid.
In modern day PA you would just apply varying time delays in Digital Signal Processing (DSP) to each section to ensure all the sound arrived at the listeners ears at the same time. But alas there was no such thing in 1931 or a general awareness of the issue.
Consequently, the sound from the Wide Range was a bit of a mess and most noticeably the listener would hear a 'tap' twice. First from the bass section and then from the mid section.
Revolution
So the Wide Range was actually quite a flawed solution. There were some good bits like the addition of a high frequency horn and a passive crossover, but the open baffle bass was limiting and the lack of time alignment fatal.
Roll on the Shearer Horn from 1935, which resolved both issues and represented a significant step forward. We'll cover this in the next post :)
Outro
Thanks for taking the time to read this blog post and I hope you enjoyed it.
If you have an comments, questions or suggestions, please just comment below or email me at ceri@enton-green.com
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