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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => HistoryOfConcertSound.org => Topic started by: John Lackner on August 28, 2013, 01:54:01 PM
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Does anybody lnow anything about the sound system used at the March on Washington?
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Does anybody lnow anything about the sound system used at the March on Washington?
Looking at various photographs of the event, it appears the main PA consisted of a pair of large re-entrant horns mounted on scaffold at around 12 to 15 foot high pointing straight across the Reflecting pool to the Washington Monument. Thread on compression driver re-entrant horns were made by Electro-Voice/University, RCA, and many other companies that looked nearly identical to those in the photo below.
A pair of large re-entrant horns each driven with around 30 watts, fairly typical for "high powered" drivers for that time, would be capable of around 130 dB at one meter.
Given the calm day and the Reflecting Pool avoiding ground absorption that pair of horns could produce around 52 dB at 2048 meters (1.26 miles).
Although 52 dB is a low conversational level, with an attentive audience the PA may have been clearly audible past the Washington Monument.
Other photos show what may be a pair of column speakers (similar to the Shure Vocal Master, though the Vocal master was not introduced until 1968) covering the area around the Lincoln Memorial.
Art Welter
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Does anybody lnow anything about the sound system used at the March on Washington?
The Sound company i cut my teeth on was RCI Sound Systems based in the DC area. For years they had a number of large 70V horns hanging in the ceiling that we brought down occasionally to use for outdoor gigs where appropriate. These horns were acquired when RCI bought out the inventory of another local A/V sound company sometime in the Early 80's. Company legend was that that company [i'm sorry, but i can't remember the name] was the contractor that did sound for the 'i have a dream' speech, and that those horns were the very horns used that day.
The story is too second/third/fifth hand for me to attest to it's truth. But the timeline is right, and the horns were the right vintage and look Identical to the ones in the pictures here. I used to remember the model number of them, but my memory for such details is really poor so i don't remember now.
As far as i know RCI still owns these horns and still uses them on occasion, although i haven't spoken with anyone from their shop in many years.
Riley Casey may be able to fill in the blanks in my story and/or refute my story altogether since he's a long-time DC area operator. Meanwhile, i'll see if i can dig up something that will jog my memory as to what those horns actually were along with the name of the company that they were bought from....
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A 50 watt Bogen and a pair of LH-1s was the rig I used in the early to mid/late 60's. The LH-1 can be more than loud and I would think coverage for the event was more than adequate using those horns.
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A pair of large re-entrant horns each driven with around 30 watts, fairly typical for "high powered" drivers for that time, would be capable of around 130 dB at one meter.
Given the calm day and the Reflecting Pool avoiding ground absorption that pair of horns could produce around 52 dB at 2048 meters (1.26 miles).
The photos in this thread show straight horns with 2 and 4 drivers each:
https://forums.prosoundweb.com/index.php/topic,175960.0.html
The level at 2048 meters (1.26 miles) may have been another 6 dB or so louder than my previous estimate.
I wonder what the movie will be like..
Art