Very large sized planar driver ( 180square feet) ...possible ?

[JinMTVT]

I've posted this in the alternative forum, but i guess it will have more success of beeing answered here.

I have yet to come to some ideas about a driver with a radiating area that would cover a complete section of a wall .. ( searched quite a bit here, and on google )

my idea would be using subwoofer type motors,
to drive some carbon composite structure with laid on mylar or other diaphragm

would use the complete wall section in front of my room

application is of course, only for sub-frequencies
( 100hz less i guess )

wonder if it would be possible,
what kind of problems would it cause
rooms interaction ( no modes fron sides and top/bottom??? )

also if there are some mathematics that could be used to calculate the possiblities

so any links or ideas or comments
( maybe i am just plain stupid and this is an impossible driver ) are welcomed!!!

this came to me as i was trying to understand planar waves generation, and trying to grasp a design ..than thought about ESL diaphramgs ...

also would like to understand how waves coming out of a " moving wall" would be ??

thanks all

[Cloth Ears]

Are you thinking of moving the whole wall (edge-to-edge), or just having it 'flexible' and attaching the motor to the centre (or possibly a number of centres)?

[JinMTVT]

nah , i want it to move completly

probably would install anything from 8 to 16 motors,
spread evenly so they also hold up the wall and allow it to move all together ...

would require some type of sealed/suspension all around..probably bolted or glued to the walls

sice this would operate in IB setup
( garage room will be rear enclosure .. )

with CF using hollow tubes, i could make it seriously light weight since stretched mylar doesn't add much weight for a subwoofer ... i guess

[JinMTVT]

would this make a completly planar wave ?
or would it buldge and mirror out of the side walls?

if pressure can't go anywhere , like in a horn or a tube,
does the wave stabilize or maintain it's pressure over all of the room distance? ( not perfectly i know ..but theoritically ? )

the effect i want to achieve for the sub frequency of my setup, is a serious planar wave bass from front to rear
where i would/could absorb most of it with some 1-3' thick absorber ...

[Cloth Ears]

I was just thinking that you wouldn't need to look at the surround so much if you were only "wobbling it" from the centre. And you wouldn't be putting so much strain on the motors in holding up your 'wall'.

If you've got that much space, have you thought of a seriously huge ribbon, etectrostat or other such planar driver - instead of a traditional motor?

I'd suggest that you should look up the way that line arrays generate waves in a room, as this will essentially be a room-width line array.

[JinMTVT]

well i have still alot to learn about accoustics...
and i will devote more time to this this winter
( now very busy months )

i seriously want to have it all move forward and back,
since any other type of movements wouldn't help in producing a serious planar wave launch,
and thus would require room modal design and treatments for sub frequencies
( wich i am trying to avoid for now )

the assembly could also lay on some roller bearings or tracks...there is no mechanical limits to this type of driver
wich is basically quite simple

still don't have a clue onto how this driver would create the wave in front of it, and it it would do what i'd like it to do!

[broughd]

If you want to move the whole wall, it will need to be stiff or you will get 'cone' breakup distortion... To stiffen the wall will make it heavy, which will mean you will need large motors, and they will need to be very well secured to something heavy like a large lump of concrete... Sounds like something NASA would build, not for HIFI though...


Have you thought of heavily bracing and covering you whole wall in 18" drivers, that would have the effect you are looking for right?

As a rough calc, if you have 64 drivers, it will be up 27db compared to one, and if you pick a driver that can put out say peak 110db at low frequencies, you have 137db and that is before the room gain

DB

[JinMTVT]

there shall be not much room gain if i can accomplish some kind of planar waves ..

then, how can one calculate the breakup frequency of a driver ? i guess it is related to the diameter / size vs frequncy of operatino and its stiffness


then , my backup wall will be all concrete as my house construction is ICF ( all concrete forms from floor to flat roof ) so i will have no problem fixing the motors,
and i'd probably be able to take drastic ways to mount them ..i have all the rights to this section of the house!
( basement garage and service room are all mine!! )

64 drivers are a bit too much
my budget is high for this setup ..
but 64 anything at 100$
adds up quite fast ..

i have the CF ressource as we are R&D with carbon fiber right now ..so this is no cost for me

and i am pretty sure that with a mix of mylar and cf frame
i could get out with some very stiff and lightweight structure ... NASA ain't got nothin on me


the mechanical part of this don't scare me much,
the accoustical does ... i do not have a clue of the behavior this monster would create

keep in mind it would be used for <100hz only!

[sdclc126]

I think you should just try installing a whole bunch of IB subs into the wall.

Using an entire wall as a speaker diaphragm, while intriguing, is IMHO so experimental that the chances of success are remote.

A "wall" of IB subs will give you so much bass you'll feel like you're sitting inside a 32' organ pipe (with proper amplification, that is).

[Ron E]

My suggestion: back up to the beginning and explain what the goals are, or go through the steps that led you to where you are now.