Have you considered Correx. Link below to just one of many sellers on ebay. I have some EAR Primary Drive open baffles that use this as the baffle for the bass driver. These particular speakers have their flaws due to the design of the mounting of the bass driver, but may be of use for your intended application?
Yellow fluted correx board for out door signage and display. 10 Sheets A1 | eBay
Yellow fluted correx board for out door signage and display. 10 Sheets A1 | eBay
No, I hadn't, thanks for the suggestion. Whilst it could be curved in one direction, not so much in the other. The PVC sheet I have a sample of (table top protector) has similar issues although it does have a small degree of flex/stretch in both directions simultaneously. The mass loaded vinyl I linked too could be better in that regard, I don't know.
The transmission loss reduces at low frequencies because the material is starting to move; where in a cabinet application it would be doing the "passive radiator" effect described earlier.
I suppose the trick would be to cross over a cabinet made from such material to another before this happens. Picking a number out of the air, say 100Hz, one could make that part of a speaker out of rigid material, the "top" part out of "passive radiance problem if used at low frequencies" type material. Where it hopefully would not radiate sound offensively - or do it less than the same geometry made out of rigid stuff.
OK - I'm itchin' to make a Metronome enclosure out of 1/2" sheet rubber stall mat. Constructed from wood, I bet you could use it as a musical instrument (with the bottom wide-open) struck with a mallet in a samba marching band. I think the tapered geometry would lend itself well to a resulting semi-rigid structure. Particularly if just the narrower parts were constructed with some dense yet flexible material - and the wider bottom panels were rigid.
Just my pipedream.
I suppose the trick would be to cross over a cabinet made from such material to another before this happens. Picking a number out of the air, say 100Hz, one could make that part of a speaker out of rigid material, the "top" part out of "passive radiance problem if used at low frequencies" type material. Where it hopefully would not radiate sound offensively - or do it less than the same geometry made out of rigid stuff.
OK - I'm itchin' to make a Metronome enclosure out of 1/2" sheet rubber stall mat. Constructed from wood, I bet you could use it as a musical instrument (with the bottom wide-open) struck with a mallet in a samba marching band. I think the tapered geometry would lend itself well to a resulting semi-rigid structure. Particularly if just the narrower parts were constructed with some dense yet flexible material - and the wider bottom panels were rigid.
Just my pipedream.
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I've a cork tiled floor, it's a great material, very versatile
I wonder what it's transmission loss is like..........
As a non resonant surface, yes, but I am thinking to use something as an acoustic barrier, ie actual enclosure or baffle, maybe for an open baffle speaker.
The MLV compares quite well to plywood, except thick ply is more linear
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It's a corking good number no doubt!I've a cork tiled floor, it's a great material, very versatile
FWIW and somewhat related, in the early 80´s I was asked to design and build a large PA system for the Moscow Circus.
They were on Tour in Buenos Aires for the first time after decades, they expected mild success, way back then they were "the evil Russians", so did not carry the full complement of trucks, wagons, huge PA system, etc. since they would perform for 2 weeks only, inside Luna Park, our Madison Square Garden venue, so they used the "house" PA system.
Blockbuster success, so they decided to go on tour but could not stop and wait 2 to 4 weeks for "hardware" being packed and shipped from Russia.
Their Plan B was to rent stuff from local circuses.
Round tents are made out of "pizza slice" sections made out of HEAVY waterproof canvas. (hint hint)
They rented two large ones, which they spread to make two semicircular ones ... 95 meters apart , joined by truck spec canvas rectangles.
Tent covered space was 50 by 95 meters ... half a city block.
Acoustics inside a "closed space enclosed by flappy walls" was ... weird, to put it mildly. Now you see why in mention it in this thread.
Much worse than "free air" which at least is "flat", here some frequencies bounced (some mid highs), some were absorbed "normally", some were stopped dead in their tracks (probably where wall "would" have resonated if they had not been so overdamped), guess some wall sections worked as Bass traps.
Sound was weird, unintelligible, and classic EQ compensations (high treble boost, "smiley" EQ curve) did not work well, so they called me, I was the "go to" guy for "impossible" situations.
I didn´t have good "room acoustics measurement" stuff available way back then, only crude pink noise + octave display which was too broad to be of any use, besides "static" measurements didn´t ell even half the story, and a system whose brand I don´t remember now, which basically sent one loud click per second, filtered results through a "blue noise" filter (reverse pink noise curve) and displayed room response ... but which would not be available until 10/15 days later.
So I applied "Plan B", clapped my hands at different places in that cavernous site and trusted my ears ..... what else?
Which told me frequency and time response was a mess, better avoid wall/"room" influence.
Another problem was that inside the performer´s area SPL had to be relatively low, to minimize feedback problems with clown lapel mikes and the like.
I designed a system where everybody was within 10/15 meters from a sound source so they got strong "first wavefront" direct sound which provided intelligibility, and wild poorly reflected sound arrived too late to mess things much.
I built 24 **narrow** columns, triangle section, each with 8 * 6x9" whizzer cone speakers, mounted end to end so column was only 18 cm wide, 2 meter high, 50 cm deep, and they hanged from ceiling structure.
All evenly distributed around that rounded rectangle area , hanging quite low so as to be near people´s heads, but being narrow and long they did not cover much of the action, and slightly moving head right or left made them "disappear".
Also distributed 24 * 15" woofers under the seats, to cover for cannon shots, deepen drumrolls, give body to prerecorded Cossack choirs, etc.
Each column or subwoofer was powered by its own plug-in module 100W amp, 2 blocks of 30 amps, so when one failed it could be immediately replaced.
No real "maintenance" time available since shows run 24/7 from 13 to 23 Hs (and extra 11 Hs shows on Saturdays and Sundays).
I´m proud to say they were very happy with the system, and took it with them to Mexico, their next Tour leg.
And what was their "regular" PA System, which I successfully replaced?
Conceptually a similar solution, a US made one , which looks like a giant golf ball, surface covered in speakers and with horns between them, which hangs from the middle of the tent and sends out a spheric expanding wavefront which doesn´t care much about walls or ouside Acoustics.
Comrades were no fools, they also used Revox tape machines for background music, AKG hand microphones, Sennheiser radio mikes, etc.
I think the original "golf ball" was designed for Indianapolis car races and similar places.
Back to the thread subject: flexible enclosure "walls"?: AVOID them, they are a MESS.
Pick predictable rigid walls or open baffles, nothing in between.
They were on Tour in Buenos Aires for the first time after decades, they expected mild success, way back then they were "the evil Russians", so did not carry the full complement of trucks, wagons, huge PA system, etc. since they would perform for 2 weeks only, inside Luna Park, our Madison Square Garden venue, so they used the "house" PA system.
Blockbuster success, so they decided to go on tour but could not stop and wait 2 to 4 weeks for "hardware" being packed and shipped from Russia.
Their Plan B was to rent stuff from local circuses.
Round tents are made out of "pizza slice" sections made out of HEAVY waterproof canvas. (hint hint
)They rented two large ones, which they spread to make two semicircular ones ... 95 meters apart
, joined by truck spec canvas rectangles.Tent covered space was 50 by 95 meters ... half a city block.
Acoustics inside a "closed space enclosed by flappy walls" was ... weird, to put it mildly. Now you see why in mention it in this thread.
Much worse than "free air" which at least is "flat", here some frequencies bounced (some mid highs), some were absorbed "normally", some were stopped dead in their tracks (probably where wall "would" have resonated if they had not been so overdamped), guess some wall sections worked as Bass traps.
Sound was weird, unintelligible, and classic EQ compensations (high treble boost, "smiley" EQ curve) did not work well, so they called me, I was the "go to" guy for "impossible" situations.
I didn´t have good "room acoustics measurement" stuff available way back then, only crude pink noise + octave display which was too broad to be of any use, besides "static" measurements didn´t ell even half the story, and a system whose brand I don´t remember now, which basically sent one loud click per second, filtered results through a "blue noise" filter (reverse pink noise curve) and displayed room response ... but which would not be available until 10/15 days later.
So I applied "Plan B", clapped my hands at different places in that cavernous site and trusted my ears ..... what else?
Which told me frequency and time response was a mess, better avoid wall/"room" influence.
Another problem was that inside the performer´s area SPL had to be relatively low, to minimize feedback problems with clown lapel mikes and the like.
I designed a system where everybody was within 10/15 meters from a sound source so they got strong "first wavefront" direct sound which provided intelligibility, and wild poorly reflected sound arrived too late to mess things much.
I built 24 **narrow** columns, triangle section, each with 8 * 6x9" whizzer cone speakers, mounted end to end so column was only 18 cm wide, 2 meter high, 50 cm deep, and they hanged from ceiling structure.
All evenly distributed around that rounded rectangle area , hanging quite low so as to be near people´s heads, but being narrow and long they did not cover much of the action, and slightly moving head right or left made them "disappear".
Also distributed 24 * 15" woofers under the seats, to cover for cannon shots, deepen drumrolls, give body to prerecorded Cossack choirs, etc.
Each column or subwoofer was powered by its own plug-in module 100W amp, 2 blocks of 30 amps, so when one failed it could be immediately replaced.
No real "maintenance" time available since shows run 24/7 from 13 to 23 Hs (and extra 11 Hs shows on Saturdays and Sundays).
I´m proud to say they were very happy with the system, and took it with them to Mexico, their next Tour leg.
And what was their "regular" PA System, which I successfully replaced?
Conceptually a similar solution, a US made one
, which looks like a giant golf ball, surface covered in speakers and with horns between them, which hangs from the middle of the tent and sends out a spheric expanding wavefront which doesn´t care much about walls or ouside Acoustics. Comrades were no fools, they also used Revox tape machines for background music, AKG hand microphones, Sennheiser radio mikes, etc.
I think the original "golf ball" was designed for Indianapolis car races and similar places.
Back to the thread subject: flexible enclosure "walls"?: AVOID them, they are a MESS.
Pick predictable rigid walls or open baffles, nothing in between.
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