FWIW in the late 70s I custom made a PA system for "the" Moscow Circus.
They were Touring South America and not trusting Buenos Aires audiences because of then quite hot "Cold War" nonsense, they only brought basic equipment, no tents, no trailers, intended for our Luna Park, Buenos Aires 12000 seat Madison Square Garden version, for 15 days only
When that turned into chock full capacity 3 months nonstop, they decided to go on National Tour.
They had to rent stuff from three large Argentine Circuses.
Tent was gigantic: each end was made out of regular tent "pizza slices" assembled in a semi circle, space between them was filled with rectangular truck covering type canvas, total "under roof" space was 94 by 45 meters ... and Acoustics was a nightmare.
To boot, we needed a relatively low SPL area "inside" to minimize Artists/Performers microphones acoustic feedback.
Cabinetwise, I had to provide a uniform field for the public, short speaker to ear distance so as to minimize "room" acoustics influence, also because intelligibility suffers in such a huge, multi sound source place, BUT when somebody gets sound "quick" through a short path, brain decodes it and is not much troubled by later arrivals.
So I hung long but narrow columns, wedge shaped, narrow but deep, so they would not visually cover the action, I hung them quite low, one every 8-10 meters all around the performing space.
Each one contained 8 6" by 9" edge to edge mounted whizzer cone paper voice coil "car radio type" speakers which reached quite high, no need for separate tweeters.
Since hindsight is always 20-20 , NOW I know I both made a "distributed line array system" with perfect for the occasion coverage, AND filled them with full range speaker lover approved speakers.
No "magic" involved, I already knew that columns were good in such situations and light voice coil speakers were very accurate and flat by themselves.
Snappy response and voice band intelligibility was a bonus.
Bass response was not enough, but I supplemented each hanging column with a matching 15" woofer under people´s seats.
Sound was very clear and unstressed and people jumped in their seats when Cannon shots or big drum thumps were played he he.
What´s the point of this long digression?
I powered every single column and woofer with a dedicated 100W amp!!!!!!
I initially offered as many as needed 2 x 200W or 2 x 400W amps (think similar to Peavey CS400 and CS800) ... NO WAY, the Russians did not want that: their shows run 24/7 from 13:00 to 23:00 (so ending at 1 AM) so "any failure would be catastrophic" ... no physical time to replace/repair anything so they LOVED my idea of making multiple 100W amplifiers, each narrow "rack" (actually about half rack width) housing 10 of them: 8 in use and 2 as spares, sitting where they would eventually be needed.
I loved Shortwave Listening (SWL) and had experience repairing and modding old WW2 plane radios, so was quite used to the almost cubic aluminum compact case format, and the multi pin plug/socket in the back, so ...
Any failing amp could be swapped instantly, a big plus for them.
They liked it so much, they carried it with them to the next Tour leg: Mexico.
After that I lost track, but like to imagine that somewhere in Russia some old Fahey amp or cabinet is still working 🙂
They were Touring South America and not trusting Buenos Aires audiences because of then quite hot "Cold War" nonsense, they only brought basic equipment, no tents, no trailers, intended for our Luna Park, Buenos Aires 12000 seat Madison Square Garden version, for 15 days only
When that turned into chock full capacity 3 months nonstop, they decided to go on National Tour.
They had to rent stuff from three large Argentine Circuses.
Tent was gigantic: each end was made out of regular tent "pizza slices" assembled in a semi circle, space between them was filled with rectangular truck covering type canvas, total "under roof" space was 94 by 45 meters ... and Acoustics was a nightmare.
To boot, we needed a relatively low SPL area "inside" to minimize Artists/Performers microphones acoustic feedback.
Cabinetwise, I had to provide a uniform field for the public, short speaker to ear distance so as to minimize "room" acoustics influence, also because intelligibility suffers in such a huge, multi sound source place, BUT when somebody gets sound "quick" through a short path, brain decodes it and is not much troubled by later arrivals.
So I hung long but narrow columns, wedge shaped, narrow but deep, so they would not visually cover the action, I hung them quite low, one every 8-10 meters all around the performing space.
Each one contained 8 6" by 9" edge to edge mounted whizzer cone paper voice coil "car radio type" speakers which reached quite high, no need for separate tweeters.
Since hindsight is always 20-20 , NOW I know I both made a "distributed line array system" with perfect for the occasion coverage, AND filled them with full range speaker lover approved speakers.
No "magic" involved, I already knew that columns were good in such situations and light voice coil speakers were very accurate and flat by themselves.
Snappy response and voice band intelligibility was a bonus.
Bass response was not enough, but I supplemented each hanging column with a matching 15" woofer under people´s seats.
Sound was very clear and unstressed and people jumped in their seats when Cannon shots or big drum thumps were played he he.
What´s the point of this long digression?
I powered every single column and woofer with a dedicated 100W amp!!!!!!
I initially offered as many as needed 2 x 200W or 2 x 400W amps (think similar to Peavey CS400 and CS800) ... NO WAY, the Russians did not want that: their shows run 24/7 from 13:00 to 23:00 (so ending at 1 AM) so "any failure would be catastrophic" ... no physical time to replace/repair anything so they LOVED my idea of making multiple 100W amplifiers, each narrow "rack" (actually about half rack width) housing 10 of them: 8 in use and 2 as spares, sitting where they would eventually be needed.
I loved Shortwave Listening (SWL) and had experience repairing and modding old WW2 plane radios, so was quite used to the almost cubic aluminum compact case format, and the multi pin plug/socket in the back, so ...
Any failing amp could be swapped instantly, a big plus for them.
They liked it so much, they carried it with them to the next Tour leg: Mexico.
After that I lost track, but like to imagine that somewhere in Russia some old Fahey amp or cabinet is still working 🙂
High-power amplifiers & speakers have their place, and it's this: output density. Decibels per cubic foot.
Can you achieve the same SPLs using a big pile of horns, and many light-coned drivers each being driven at half their long-term rated power by small amplfiers?
Yes, probably. They did that in the 1960s and 1970s, and sometimes it worked okay.
However, I can do this:
With 6x cabinets in total, each of which I can lift with one hand.
How?
Well, there's 4x subwoofers with a Faital 15HP1060 and 2x main speakers each with 2x Faital Pro 10FH520 and 1x 18Sound ND1460.
Each 15" driver was receiving 1000w peaks, which is a little on the low side for them. Each 10" driver was receiving 1000w peaks, and each tweeter was receiving approx 200w peaks.
Thanks to the magic of class D amplifiers, I ran the whole thing on a single 13A 240v mains power supply, and didn't pop the fuse.
The entire system fits comfortably in the back of a small van - I can also throw in stage monitors, mixing desk, lights, stands, etc etc etc.
The real-world concerns here are output density, power draw, and weight. Saying "just use 20x 100w class AB amps" is all well and good, but it means using lots of low-power speakers, lots of electricity, and a forklift truck to move the amp racks and large stacks of horn-loaded speakers. It goes against all of the priorities of a touring PA system.
Chris
What's the SPL at 30Hz?
If it doesn't take 3 trucks and weigh 16 tonnes, you're doing it wrong... 😀
If it doesn't take 3 trucks and weigh 16 tonnes, you're doing it wrong... 😀
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I was the stage manager when Valve sound system came through the venue I was working at. That thing took up 1/3rd of the available floor area. "Loud" doesn't quite cover it - my vision was blurring from the bass.
Those guys aren't using a bunch of 100w amps, either.
Chris
Those guys aren't using a bunch of 100w amps, either.
Chris