1st i have to say that horizontal braces break the rule i use that subpanels should have higher aspect ratio than the starting panel. But if you are going to ignore that (and even if you don’t) the brace gives you one more thing to screw into.
Not something i have any use for… they increas emass without adding any stifness.
dave
That's a lamination of stacked ply. I also like that look, but it is extremely wasteful, both in material and cutting time.
If you want that look without so much waste, there's this excellent looking stuff (made in Melbourne):
MAXI Edge Plywood Panels
I dunno the cost, but am guessing it is quite high.
Attachments
Is this because damping pads are unimportant, those bitumen pads are ineffective at damping, the mass does more harm than the damping does good, or perhaps something else?
So, I shouldn't use Bitumen pads at all then?.
I have got the amp parts coming in next week, which is another thing I'm going to build, So hopefully I can get this done soon as well.
Also, I may just use 18mm thick Birch ply all the way around, the CNC place I will use can only cut upto 32mm.
I have got the amp parts coming in next week, which is another thing I'm going to build, So hopefully I can get this done soon as well.
Also, I may just use 18mm thick Birch ply all the way around, the CNC place I will use can only cut upto 32mm.
That is for you to decide. You have been given contradictory advice which is not exactly a surprise on an internet forum. Given your lack of knowledge about the subject area how are you going to decide what is nonsense and what, if anything, is sensible? Some of it has to be nonsense if it is contradictory.
Thicker is both stiffer and heavier but the increase in stiffness is greater and the frequency of the resonances will be raised. If you use well designed bracing then for a given increase in mass the frequency of the lowest resonances can be raised more. If you use poorly designed bracing then it can have the opposite effect.
At this stage I think I'l have to go with 18mm thick Birch Ply for all sides, Since I can't find that many places selling Birch Ply in Custom Cut Sizes.
I had a look at the Leto Bamboo Ply mentioned by HollowBoy.
The Bamboo Ply they have though, specifically the 19mm thick one, is only shown as being 3 ply. Much less than the 13 ply Birch Plywood one I can also get locally.
Would the low ply count of the Leto Bamboo ply make it unsuitable, or since they are different types of woods is this not a fair comparison?
If this is so, I would be very intersted in using this as an alternative to the Russian Birch Ply, as I prefer the look of it, although this may not be possible as It would most likely be significantly expensive, even more so than the birch plywood.
The Local CNC cutting business in my area, also supply materials needed to CNC, with the Leto Bamboo Plywood being one of them.
I had a look at the Leto Bamboo Ply mentioned by HollowBoy.
The Bamboo Ply they have though, specifically the 19mm thick one, is only shown as being 3 ply. Much less than the 13 ply Birch Plywood one I can also get locally.
Would the low ply count of the Leto Bamboo ply make it unsuitable, or since they are different types of woods is this not a fair comparison?
If this is so, I would be very intersted in using this as an alternative to the Russian Birch Ply, as I prefer the look of it, although this may not be possible as It would most likely be significantly expensive, even more so than the birch plywood.
The Local CNC cutting business in my area, also supply materials needed to CNC, with the Leto Bamboo Plywood being one of them.
Is that with or without a double thickness for the front baffle?
Is that with or without damping pads?
Ken - I've used lots of different types of sheet good materials for loudspeaker enclosures during the past almost 20yrs, from MDF to Bamboo ply, and I think if you look at the block / stave core fabrication * of the 3 ply bamboo, you'll see there's a lot of rigidity and stability built in to the very high count of glue joints, and the fact that bamboo is pretty stiff material to start with. I can certainly remember growing up with bamboo garden rakes that would last many more seasons than the thin metal tined ones - even when stored in a unventilated garden shed.
*This technique has even been used for hard and softwood plywood in the past, but there's probably much lower production cost and higher yield from logs with the rotary sliced veneers used in more conventional plywoods.
By whatever name you choose to call it, the high ply count BB types are to my mind a better material for speaker boxes than MDF, PB, the stranded wheatboard that was trendy a few years back, OSB etc. However, AFAIC, the 3 layer 3/4" bamboo plywood is an even superior product, but not inexpensive.
*This technique has even been used for hard and softwood plywood in the past, but there's probably much lower production cost and higher yield from logs with the rotary sliced veneers used in more conventional plywoods.
By whatever name you choose to call it, the high ply count BB types are to my mind a better material for speaker boxes than MDF, PB, the stranded wheatboard that was trendy a few years back, OSB etc. However, AFAIC, the 3 layer 3/4" bamboo plywood is an even superior product, but not inexpensive.
At this stage I think I'll go with 18mm for the front baffle as well as the sides.
Could go with 36mm, but the place that does CNC can only cut up to 32mm, 36mm would also mean having a deeper cabinet and I don't really want it to get to much bigger than it already is.
I'm very intrested in that Leto Bamboo plywood, but I guess I'll have to wait for a quote to know the true cost of it, I get the feeling its Likely to be significantly more expensive than even Birch Plywood.
With regards to damping, Instead of using Bitumen pads, Would it be better/easier to use bitumen paint (its also cheaper)
Ormonoid 500ml Bitumen Paint | Bunnings Warehouse
I also need a replacement for the closed cell foam I originally chose.
Would any open cell foam do?.
Shop | Foamland
Can possibly get some sort of convoluted open cell mattress foam, but I think they come in pretty thick sizes, (25mm or more).
I want to get the rest of the things needed locally, I don't want to be stuck waiting as I would hopefully like to get my build started sometime later this week.
I have replaced the 3 Vertical Braces I had previously with 3 Horizontal Braces.
One is just below the woofer with another one just above it. The 3rd one is between the mid range and tweeter cutout.
They all run the full length of the interior cabinet.
Have also done a small chamfer on the woofer cutout hole on the back of the baffle, but couldn't really make a substantial one, since there isn't much clearance/room to install the horizontal braces in the first place.
Sorry If I'm causing confusing/frustration with my posts, It's nearly 4am here In Aus, and because of that I'm to tired to go back through all the previous posts, so If I'm repeating myself or not following advice given before, please excuse me.
Could go with 36mm, but the place that does CNC can only cut up to 32mm, 36mm would also mean having a deeper cabinet and I don't really want it to get to much bigger than it already is.
I'm very intrested in that Leto Bamboo plywood, but I guess I'll have to wait for a quote to know the true cost of it, I get the feeling its Likely to be significantly more expensive than even Birch Plywood.
With regards to damping, Instead of using Bitumen pads, Would it be better/easier to use bitumen paint (its also cheaper)
Ormonoid 500ml Bitumen Paint | Bunnings Warehouse
I also need a replacement for the closed cell foam I originally chose.
Would any open cell foam do?.
Shop | Foamland
Can possibly get some sort of convoluted open cell mattress foam, but I think they come in pretty thick sizes, (25mm or more).
I want to get the rest of the things needed locally, I don't want to be stuck waiting as I would hopefully like to get my build started sometime later this week.
I have replaced the 3 Vertical Braces I had previously with 3 Horizontal Braces.
One is just below the woofer with another one just above it. The 3rd one is between the mid range and tweeter cutout.
They all run the full length of the interior cabinet.
Have also done a small chamfer on the woofer cutout hole on the back of the baffle, but couldn't really make a substantial one, since there isn't much clearance/room to install the horizontal braces in the first place.
Sorry If I'm causing confusing/frustration with my posts, It's nearly 4am here In Aus, and because of that I'm to tired to go back through all the previous posts, so If I'm repeating myself or not following advice given before, please excuse me.
Why would you need to CNC anything other 18mm? It takes no effort to stick two pieces of wood together. Stiffening the front baffle is possibly the only thing that is not in dispute by anyone. But make sure the midwoofer is adequately chamfered.
The thicker the better with extensional damping. It also needs to be fairly stiff to dissipate much energy. Soft and rubbery will do little.
The effectiveness of acoustic damping material varies quite a lot. In your case you do not need highly effective but you do need it in the right place if you are to absorb the lowest internal cabinet modes, keep the midrange frequencies out of the port and not interfere with the air flow in the port. I would be tempted to experiment with what you have and only buy something else if you cannot get it to work well.
Not sure the upper one will be of much benefit but then again it is hard to see it doing any harm. If the wood would be waste anyway and it looks more symmetrical then why not. Give the midwoofer room even if you need to cutout a section to accommodate the midrange.
All the bamboo plywood we have used has had a similar block core 3 layer structure. The middle layer can’t really be called a ply. This structure is similar to honrycomb aluminum/fiberglass sheets, basically an extended i-beam kind of structure. What is very important is the stiffness of the outer, sandwich veneers. The stranded varieties have tremendous stiffness, the vertical grain versions less so, and the horizontal grain the poorest. The Stranded varieties represent the best panel material we have used to date and is highly recommended. The only downside is its high density which means it weighs a lot.
We are just now trying to find sources for some for a client build. What is available is limited and the cost is high. I wish we had a Leto here.
dave
To clarify Dave's above post - there's more than enough confusion in the terminologies used in the trades, both in generic descriptions used on the front-lines (by fabricators), and by various manufacturers / distributors.
The only stranded bamboo plywood I've ever used is solid block/stave core construction as seen here - from Cali Bamboo's site, but same type as Plyboo Neopolitan.
There is also fully stranded fabrication - which I've never used, and may not be as widely available, or in the same range of size / thicknesses.
What for me is important is that not all suppliers offer all patterns / colours in the same sheet / panel sizes - some are as small as 30x72", 48x72" is another common size, while 4x8 would normally be my choice. This only matters if you're concerned about contiguous pattern/grain matching around the perimeter of an enclosure - which happens to be one of the few of my personal fetishes that is safe to discuss publicly.
The only stranded bamboo plywood I've ever used is solid block/stave core construction as seen here - from Cali Bamboo's site, but same type as Plyboo Neopolitan.
There is also fully stranded fabrication - which I've never used, and may not be as widely available, or in the same range of size / thicknesses.
What for me is important is that not all suppliers offer all patterns / colours in the same sheet / panel sizes - some are as small as 30x72", 48x72" is another common size, while 4x8 would normally be my choice. This only matters if you're concerned about contiguous pattern/grain matching around the perimeter of an enclosure - which happens to be one of the few of my personal fetishes that is safe to discuss publicly.
It may be best to ask their local reseller for prices:
Joinery Supplies Tasmania: Derwent Park and Invermay
In Melbourns, Plyco list the prices (online) for some of the sizes. It is $425 for the 19mm strand woven. That's not insane, but is a bit much for me.
Personally, I'd opt for a base layer of sturdy but aesthetically humble plywood ($30-75) and then make it pretty with a 5mm skin of the strand woven bamboo ($150).
Leto cover exactly this in their FAQ:
"Can 5mm thick, single ply bamboo veneer be applied (laminated) to different material such as MDF or birch?"
A couple of these small $31 sheets (or similar) would be enough for your project.
Bamboo Laserply - Natural – Plyco
I love that this is called 'sandwich theory'.
Off-topic: what would be a good filler, if one wanted to use sandwich construction to make large, lightweight boxes?
I did a trial with 3mm MDF as the 'bread', and polystyrene panel as the filler. It seemed promising.
If I were to do a 'real' build with this tech, I'd upgrade to a construction ply for the skin, but dunno about the fill layer.
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