RobWells said:
Chris and i don't agree on this yet. If i can get away with it i like to build cabs out of 1/2" plywood (with laminate inside & out if i'm really doing to town). Chris likes thicker materials because they are easier to work with. And a thick layer of veneer is easier than a skinny one so he often ends up with 1 1/4" - 1 1/2" walls.
One of the boxes i built out of 1/2" HDF made a step backwards sonicly (but a HUGE leap forward cosmetically) when Chris added a 1/2" layer of veneered ply. The sonic issues are fixable, i'd NEVER be able to make as pretty a box.
dave
cabinet thickness
Rob:
Yup, 120 net litres is not small .
I've never personally built anything thicker than 1.5" (38mm)- for several reasons:
Weight - mass damping is certainly one of the easiest methods to achieve low resonance enclosures, but (at least in this time/space continuum) mass generally means weight. Sooner or later someone has to move the BMF, and my back is not getting any younger.
Efficacy - I'm not altogether convinced that sheer mass is the best way to treat resonant energy at all frequencies.
Several experiments with sealed and ported enclosures using skeletal bracing (once again I'd cite B&W matrix enclosures as the best example) of stiff material, and even simplified constrained layers have proven very interesting
For example 3/4" Baltic birch is much stiffer than MDF and when used for internal bracing, will transmit physical vibrations to the exterior walls faster and with less attenuation than a similar structure in MDF. ( So is 1/2" steel, but the BB is considerably lighter
)
Irregularly spacing and rebating the bracing tightly into the cabinet walls will break the external walls into a series of smaller panel areas, each with a different resonant frequency, and lower individual amplitude than a single panel of the same total area. The result should be a more random spectrum of resonances, some of which are above the Res Fr of the nominal enclosure, and therefore not as easily excited.
that's the theory anyway
Cosmetics - as Dave from that numbered Planet would attest, I spend at least as much time dealing with making it purdy as in making it "technically" sound ( the advantage of using someone else's design, is that you don't have to do much math, and if it sound good and looks great you're both a craftsman and a genius, and if not - well " It's not MY design "
BTW Dave: the cherry ply on the little pyramids was only 1/4" (6mm), but it's interesting how much difference you heard, and I'm getting closer to your way of thinking - I still use veneer cause I just hate plastic laminate ( not working with it, just the look - it's only one step above mac-tac. )
As I've been gravitating recently to the less is more "mostly full range" camp, (thanks of course to Lance for the impetus and source of parts) the drivers are getting smaller and fewer. The scale of an enclosure to the driver has an aesthetic appeal to me, - it's hard to describe, but you can feel it when the size is just right.
Rob:
Yup, 120 net litres is not small .
I've never personally built anything thicker than 1.5" (38mm)- for several reasons:
Weight - mass damping is certainly one of the easiest methods to achieve low resonance enclosures, but (at least in this time/space continuum) mass generally means weight. Sooner or later someone has to move the BMF, and my back is not getting any younger.
Efficacy - I'm not altogether convinced that sheer mass is the best way to treat resonant energy at all frequencies.
Several experiments with sealed and ported enclosures using skeletal bracing (once again I'd cite B&W matrix enclosures as the best example) of stiff material, and even simplified constrained layers have proven very interesting
For example 3/4" Baltic birch is much stiffer than MDF and when used for internal bracing, will transmit physical vibrations to the exterior walls faster and with less attenuation than a similar structure in MDF. ( So is 1/2" steel, but the BB is considerably lighter
) Irregularly spacing and rebating the bracing tightly into the cabinet walls will break the external walls into a series of smaller panel areas, each with a different resonant frequency, and lower individual amplitude than a single panel of the same total area. The result should be a more random spectrum of resonances, some of which are above the Res Fr of the nominal enclosure, and therefore not as easily excited.
that's the theory anyway
Cosmetics - as Dave from that numbered Planet would attest, I spend at least as much time dealing with making it purdy as in making it "technically" sound ( the advantage of using someone else's design, is that you don't have to do much math, and if it sound good and looks great you're both a craftsman and a genius, and if not - well " It's not MY design "
BTW Dave: the cherry ply on the little pyramids was only 1/4" (6mm), but it's interesting how much difference you heard, and I'm getting closer to your way of thinking - I still use veneer cause I just hate plastic laminate ( not working with it, just the look - it's only one step above mac-tac. )
As I've been gravitating recently to the less is more "mostly full range" camp, (thanks of course to Lance for the impetus and source of parts) the drivers are getting smaller and fewer. The scale of an enclosure to the driver has an aesthetic appeal to me, - it's hard to describe, but you can feel it when the size is just right.
120 liters is what I used for my sub.
30" wide, 24" deep, 18" high. 2xSV12 from Audio Concepts.
I used 30mm MDF but braced the box as best I could before sacrificing too much box volume. The baffle was 18mm/30mm sandwich.
I try to take the "mad" approach. As much thickness and as much bracing as WAF will allow.
The object of using bent MDF is to pre stress the wood and make it stiffer. Then I will use about 6 internal H braces to break up the cabinet to smaller panels.
One reason I was looking at a lead - MDF sandwich was to add mass to the box. but Andy or Dave told me to forget it. why I dont know?
Lastly I have used egg crate foam and glass wool to damp the cabinet internally. Now I think I will use a combination. egg crate foam on the walls (2" thick) and glass wool on the bracing.
Any suggesstions?
regards
navin
30" wide, 24" deep, 18" high. 2xSV12 from Audio Concepts.
I used 30mm MDF but braced the box as best I could before sacrificing too much box volume. The baffle was 18mm/30mm sandwich.
I try to take the "mad" approach. As much thickness and as much bracing as WAF will allow.
The object of using bent MDF is to pre stress the wood and make it stiffer. Then I will use about 6 internal H braces to break up the cabinet to smaller panels.
One reason I was looking at a lead - MDF sandwich was to add mass to the box. but Andy or Dave told me to forget it. why I dont know?
Lastly I have used egg crate foam and glass wool to damp the cabinet internally. Now I think I will use a combination. egg crate foam on the walls (2" thick) and glass wool on the bracing.
Any suggesstions?
regards
navin
navin said:
More mass pushes the resonant frequencies of the panels down, exactly the opposite of what you are trying to do by making the panels rigid. A lower panel resonance is also easier to excite.
The light/stiff/small panel resonance technique aims to push any resonances high enuff that they are very hard to excite.
When you divide panels you also want to do it such that they are long, thin, & all different sizes.
dave
"way better" is best but does not allow other braces to coexist.
I intend to use 6 A braces at irregular heights and 4 B braces along each corner. and lots of smaller "way better" braces between the 6 A braces.
The A braces are sort of H shaped and actually are made by taking 18mm MDF and cutting 4 holes in it like the way Theil does for it's 3.6 see...
http://www.thielaudio.com/THIEL_Web/Pages/d&e.html
http://www.thielaudio.com/THIEL_Web/Pages/tour.html
regards
navin
I intend to use 6 A braces at irregular heights and 4 B braces along each corner. and lots of smaller "way better" braces between the 6 A braces.
The A braces are sort of H shaped and actually are made by taking 18mm MDF and cutting 4 holes in it like the way Theil does for it's 3.6 see...
http://www.thielaudio.com/THIEL_Web/Pages/d&e.html
http://www.thielaudio.com/THIEL_Web/Pages/tour.html
regards
navin
getting stiff
Navin - no matter how many layers, I don't think you'll never get an MDF assembly as stiff as a high quality plywood (Baltic Birch/apple-ply), even with the engineered stress of curving the panels. Of course this is much easier to achieve with flat panels than something curved like the Amati's.
The internal structure of MDF core is a combination of numerous non-continuous milled fibres of various lengths, finer wood particles and substantial amounts of binder resin. It's just too internally damped. The exact mix, size and quality of ingredients, and the tempering of the finished surface can vary substantially amoung brands and grades of board. But I digress
Someone has mentioned in one of the forum threads the approach of vertically stacking a series of flat layers cut to the desired shape(s). Think of those new computer "topographic"(?) X-ray scans that slice the body into a series of virtual layers.
You can create almost any internal structure imaginable just by size and location of openings in each successive layer.
Internal bracing and dividers can be fabricated by cutting holes in each layer, or leaving blank.
This approach applies as easily to MDF as plywood, but in either case WEAR A DUST MASK , and take frequent fresh air breaks. Both will produce copious amounts of "sneezing powder", but resin content of MDF is much more toxic.
If you have a decent router ( 3hp would be nice) and carbide flush trim cutter, it's not difficult to machine the necessary stack of parts using a template, in a matter of a few hours. Glue strips of plastic laminate to all edges of the template on which the cutter bearing will ride. (The machined raw edges of MDF are particularly soft and will gouge very quickly, resulting in variations of cut parts.)
Make a jig for a drill press to machine at least 2 indexing holes in each piece, which can be dowelled.
Once all parts are machined and dry fit tested, there's no reason why it couldn't be assembled in a single glue-up.
I should try this some time
Navin - no matter how many layers, I don't think you'll never get an MDF assembly as stiff as a high quality plywood (Baltic Birch/apple-ply), even with the engineered stress of curving the panels. Of course this is much easier to achieve with flat panels than something curved like the Amati's.
The internal structure of MDF core is a combination of numerous non-continuous milled fibres of various lengths, finer wood particles and substantial amounts of binder resin. It's just too internally damped. The exact mix, size and quality of ingredients, and the tempering of the finished surface can vary substantially amoung brands and grades of board. But I digress
Someone has mentioned in one of the forum threads the approach of vertically stacking a series of flat layers cut to the desired shape(s). Think of those new computer "topographic"(?) X-ray scans that slice the body into a series of virtual layers.
You can create almost any internal structure imaginable just by size and location of openings in each successive layer.
Internal bracing and dividers can be fabricated by cutting holes in each layer, or leaving blank.
This approach applies as easily to MDF as plywood, but in either case WEAR A DUST MASK , and take frequent fresh air breaks. Both will produce copious amounts of "sneezing powder", but resin content of MDF is much more toxic.
If you have a decent router ( 3hp would be nice) and carbide flush trim cutter, it's not difficult to machine the necessary stack of parts using a template, in a matter of a few
hours. Glue strips of plastic laminate to all edges of the template on which the cutter bearing will ride. (The machined raw edges of MDF are particularly soft and will gouge very quickly, resulting in variations of cut parts.) Make a jig for a drill press to machine at least 2 indexing holes in each piece, which can be dowelled.
Once all parts are machined and dry fit tested, there's no reason why it couldn't be assembled in a single glue-up.
I should try this some time
" Someone has mentioned in one of the forum threads the approach of vertically stacking a series of flat layers cut to the desired shape(s). Think of those new computer "topographic"(?) X-ray scans that slice the body into a series of virtual layers.
You can create almost any internal structure imaginable just by size and location of openings in each successive layer.
Internal bracing and dividers can be fabricated by cutting holes in each layer, or leaving blank. "
That's me
I have changed the plan slightly as I was playing with the shape on the cad at work today, and I cant go to a small point at the back as I lose too much internal volume....
I've decided on a "rectangular with bowed walls" type thing - internally flat front, 2 long bowed sides and a bowed back. All made out of layers - just ordered 4 sheets of 38mm mdf today (££ouch!)
footprint should be about 650 deep, 350 - 450 - 350 wide and 700 high. Am gonna put a seperate cylindrical mid enclosure above, with seperate tweeter above that...
bracing will be a random affair using an X type thing cut into the layers
Rob
You can create almost any internal structure imaginable just by size and location of openings in each successive layer.
Internal bracing and dividers can be fabricated by cutting holes in each layer, or leaving blank. "
That's me
I have changed the plan slightly as I was playing with the shape on the cad at work today, and I cant go to a small point at the back as I lose too much internal volume....
I've decided on a "rectangular with bowed walls" type thing - internally flat front, 2 long bowed sides and a bowed back. All made out of layers - just ordered 4 sheets of 38mm mdf today (££ouch!)
footprint should be about 650 deep, 350 - 450 - 350 wide and 700 high. Am gonna put a seperate cylindrical mid enclosure above, with seperate tweeter above that...
bracing will be a random affair using an X type thing cut into the layers
Rob
RobWells said:
in response to your earlier post, don't forget that a properly executed elliptical shape can be much stiffer and less resonant than any "rectalinear" enclosure of the same internal volume, and with the same amount of bracing, will incorporate less material.
just not as easy to build in your garage - access to CADCAM/CNC, automated clamping or vacuum presses would be nice
As Dave has hinted elsewhere in this thread, we are converging on the leaner/stiffer approach - strategic bracing and "just enough" material. Just for fun, try this sometime on something like a small full-ranger ( RS40-1197 BD pipe for example)
chris b: 1. why does everyone use MDF? I dont mind using ply but I thought mdf with its random structure was more suitable for speaker cabinets. ply is far easier to work with.
i have access to reasonable quality marine ply. I can easily use this. it is in fact cheaper than MDF!
regards
navin
i have access to reasonable quality marine ply. I can easily use this. it is in fact cheaper than MDF!
regards
navin
navin said:
MDF is easier to machine, usually costs less, and ties in with the heavily damped school of box-building (bigger is better camp). The plywood you need is void-free & many plys.
Hornet uses 1.5mm veneers for build-your-own shaped "plywood" technology.
Similar would be Cedar/West System.
dave
I find ply easier to work with but was afraid the ply would open up. what I mean is that the various plys within a 25mm ply sheet would open up. ply is a lot easier to bend.
void free ply? ok lets see if I can get that here. what I can get is what they call marine ply (which also claims to be termite free).
if i get void free ply 18mm or more should I use that instead?
regards
navin
void free ply? ok lets see if I can get that here. what I can get is what they call marine ply (which also claims to be termite free).
if i get void free ply 18mm or more should I use that instead?
regards
navin
final thougths...(lets nail this coffin)
final thoughts...
cabinet: 48"H
curved sides 4mm (16"x48") MDF x 3 layers (additional layers will be added if 12mm feels not stiff enough). speaker is 10" at baffle, expandig to 10.5 to 11" at widest point and tapering to 3" at rear (a la Sonus Faber Amati mentioned before); baflfle: 18mm MDF x 2 layers; rear: 18mm MDF (2 layers if nesscary)
bracing: 6 18mm MDF board with holes at irruglar intervals (a la Thiel Loudspeakers) and 1"x1" posts along each (side-baffle and side-rear) corner.
damping: 2" egg crate foam on walls, 1" thick sheets of glass wool on bracing.
isolation: tweeter mounted on neoprene rubber sheet, 8" having independant baffle.
difraction compensation: part compensation from 8" (upper bass), parrt compensation from baffle being rounded off (a la Theil)
drivers: Emience 8" (repaired cone) near floor, 6" woofer at top of cabinet and tweeter just below 6". Top 1/4 of cabinet is independant box.
ideas rejected: lead sheet between layers of MDF (no reason expect it was suggested by someone I think knows more than me and weighs 4 stone more )
ideas being toyed with: fiberglass between layers (outside will be veneered so no need to fiberglass the outside)
XO:
series XO as suggested by Andy G.
If anyone has any suggestions please do so now or forever odl your peace (or piece whichever you want to look at it)
final thoughts...
cabinet: 48"H
curved sides 4mm (16"x48") MDF x 3 layers (additional layers will be added if 12mm feels not stiff enough). speaker is 10" at baffle, expandig to 10.5 to 11" at widest point and tapering to 3" at rear (a la Sonus Faber Amati mentioned before); baflfle: 18mm MDF x 2 layers; rear: 18mm MDF (2 layers if nesscary)
bracing: 6 18mm MDF board with holes at irruglar intervals (a la Thiel Loudspeakers) and 1"x1" posts along each (side-baffle and side-rear) corner.
damping: 2" egg crate foam on walls, 1" thick sheets of glass wool on bracing.
isolation: tweeter mounted on neoprene rubber sheet, 8" having independant baffle.
difraction compensation: part compensation from 8" (upper bass), parrt compensation from baffle being rounded off (a la Theil)
drivers: Emience 8" (repaired cone) near floor, 6" woofer at top of cabinet and tweeter just below 6". Top 1/4 of cabinet is independant box.
ideas rejected: lead sheet between layers of MDF (no reason expect it was suggested by someone I think knows more than me and weighs 4 stone more
)ideas being toyed with: fiberglass between layers (outside will be veneered so no need to fiberglass the outside)
XO:
series XO as suggested by Andy G.
If anyone has any suggestions please do so now or forever odl your peace (or piece whichever you want to look at it)
Advice?
Navin, dear boy, you have to know that you'll only receive the best "I told you so" advice after the project is completed
In all seriousness, since I started DIY speaker building I've second guessed the results so often, even after extensive research, (conflicting) expert consultation, and detailed drafting of plans,that I could fill a small room with the "not quite right"
In fact, I actually have, come to think of it.
"This is a song that never ends........"
But really, seriously, it would appear from the evolution of this thread that you've firmed up your concept of this project. Good luck, and if you have access to the equipment, it'd be nice to see photos or sketches.
Navin, dear boy, you have to know that you'll only receive the best "I told you so" advice after the project is completed
In all seriousness, since I started DIY speaker building I've second guessed the results so often, even after extensive research, (conflicting) expert consultation, and detailed drafting of plans,that I could fill a small room with the "not quite right"
In fact, I actually have, come to think of it.
"This is a song that never ends........"
But really, seriously, it would appear from the evolution of this thread that you've firmed up your concept of this project. Good luck, and if you have access to the equipment, it'd be nice to see photos or sketches.
Hi again, chaps..
I dunno if this would be better carried on on a new thread, as Navin seems pretty finalised on his design.
I've drawn up the layers thing properly and an elipsical one looks do-able just a bit large (727mm deep 720mm high and 320-420-80mmradius at back) volume allowing for bracing is around 120L.
What I wanted to ask you guys is whether you think I should use plywood for the braces rather than mdf. Would the stiffness help?
I'm gonna put 2 across the width with holes cut out(to brace the sides), plus 3 built into the layers(to brace front to back, and help the other braces too)
I can draw up a crappy drawing on paint if it helps, or post a shot from the cad at work on monday..
Cheers
Rob
btw Navin - good luck on your project , I hope it all goes well
I dunno if this would be better carried on on a new thread, as Navin seems pretty finalised on his design.
I've drawn up the layers thing properly and an elipsical one looks do-able just a bit large (727mm deep 720mm high and 320-420-80mmradius at back) volume allowing for bracing is around 120L.
What I wanted to ask you guys is whether you think I should use plywood for the braces rather than mdf. Would the stiffness help?
I'm gonna put 2 across the width with holes cut out(to brace the sides), plus 3 built into the layers(to brace front to back, and help the other braces too)
I can draw up a crappy drawing on paint if it helps, or post a shot from the cad at work on monday..
Cheers
Rob
btw Navin - good luck on your project , I hope it all goes well
hi chrisb, navin & rob !
Chris: I don't know if i have ever seen pics of any of your curved cabinets. Any chance of showing or point me to some pics please. I always love to SEE how other people are doing things. (a picture paints a 1000 words)
Navin and Rob !! you better make darn sure you take LOTS of pics during construction. PLEASE!!! (or I'll have to send the boys round !!)
Chris: I don't know if i have ever seen pics of any of your curved cabinets. Any chance of showing or point me to some pics please. I always love to SEE how other people are doing things. (a picture paints a 1000 words)
Navin and Rob !! you better make darn sure you take LOTS of pics during construction. PLEASE!!! (or I'll have to send the boys round !!)
i will make pics.
this is my first speaker since I got a digtial camera.
only dont expect progress too fast. i got a day job from mon-sat, wife, kid, active social life, and am also renovating a new place for us to move into. these speakers will be at the new place.
we will still have the old place (where the SS 8546-9900) speakers will be. the new place will be better for my wife.
Once these speakers are done I will tear down the 8546-9900 speakers and rebuild them with better carpentry skills. I might rebuild the subs (2X12 per channel) too.
cheers and thanks a lot. if I disappear for a while just remember I am in the shop.
you guys can still use email though.
regards
navin
this is my first speaker since I got a digtial camera.
only dont expect progress too fast. i got a day job from mon-sat, wife, kid, active social life, and am also renovating a new place for us to move into. these speakers will be at the new place.
we will still have the old place (where the SS 8546-9900) speakers will be. the new place will be better for my wife.
Once these speakers are done I will tear down the 8546-9900 speakers and rebuild them with better carpentry skills. I might rebuild the subs (2X12 per channel) too.
cheers and thanks a lot. if I disappear for a while just remember I am in the shop.
you guys can still use email though.
regards
navin
Re: hi chrisb, navin & rob !
Hello Andy,
Will do - only prob is I will use a normal camera, and get the photos developed onto cd-rom. This will take some time, as I am building these after work, and doing it in stages.
Ordering the box stuffing, spikes, cable, posts and last 2 s-speak bass units on monday - will have everything to begin construction then.....
Rob
btw, any thoughts on the ply vs mdf bracing anyone?
Navin and Rob !! you better make darn sure you take LOTS of pics during construction. PLEASE!!! (or I'll have to send the boys round !!)
Hello Andy,
Will do - only prob is I will use a normal camera, and get the photos developed onto cd-rom. This will take some time, as I am building these after work, and doing it in stages.
Ordering the box stuffing, spikes, cable, posts and last 2 s-speak bass units on monday - will have everything to begin construction then.....
Rob
btw, any thoughts on the ply vs mdf bracing anyone?
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