MDF is hard?
dense - certainly, and I've got scars to attest that the heat tempered surface is hard enough to hold a sharp enough edge to do serious damage to flesh, but once that layer's removed by sanding, the underlying core is soft enough to easily be crushed and cut edges can be scratched with a fingernail; and rigid? not so much
Hmmm... That heat tempered surface fooled me. So, only sharp-edged cuts advisable in MDF?
From what I've seen, there should be a chamfer (is that the correct term?) on the back edge of the mounting hole cutout to allow a little air flow around the basket. If I round off that edge, is it likely to crumble?
I have some leftovers from "Handy Panels" from Home Depot. Avoid at all costs?
Or maybe just worth experimenting with...
There are bamboo 'butcher block' cutting boards in all the dollar stores...
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From what I've seen, there should be a chamfer (is that the correct term?) on the back edge of the mounting hole cutout to allow a little air flow around the basket. If I round off that edge, is it likely to crumble?
I have some leftovers from "Handy Panels" from Home Depot. Avoid at all costs?
Or maybe just worth experimenting with...
There are bamboo 'butcher block' cutting boards in all the dollar stores...
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In Bernie's case he loves to work in solid. He started with the fir because it has been aging for some 70 years + (it was his hardwood gloor).
The comparison of Mar-Ken12T in fir vrs plywood had the fir showing a bit of (euphoruc) colouration the ply did not have. But cosmetic appeal/WAF!!!
We now also have locust, yew and now western red cedar boxes. The cedar are very interesting.
Bernie is talking about yellow cedar next (yellow cedar is not a cedar)
dave
Bamboo is very good. Butcher block is a step up from flooring but not up to the lowest grade of plywood.
dave
Without stepping on the soap box, I avoid MDF for speaker enclosures whenever possible - it's not without advantages from a manufacturing / finishing point of view - great machine-ability compared to plywoods, and for that matter a lot of solid soft or hardwoods, but sonically even chipboard ( i.e. particle board - remember "K3"?) "sounds better". I exclusively use quality multiple layer plywood - i.e. Baltic/Russian/Finnish birch, Appleply, Murphy Hardwood Multiply - and no doubt there are other regionally distributed brand names.
Unsupported thin and highly profiled edges on MDF are prone to breakage - what I was trying to point out is that only a very thin layer under the tempered surface of even the best quality MDF is hard. Also be aware that not all MDF panels are engineered or created equal - from Fire-rated to moisture resistant to ultra-lite to super cheap quality, the mechanical properties can vary significantly.
This driver has that wonderful Fs of 35.386 which drives down the EBP to 86.3.......making it suitable to be run in a sealed...I got .3222311...Cubic feet for sealed. Great driver that can go either way!
On the wood front...I'll harp again on my favorite wood that most nations cannot get due to export laws here. Quebracho AKA "Axe Breaker" (Colorado red) An "Ironwood" that grows almost exclusively down here. It has export restrictions here but we have it for firewood....go figure. I will be using it for my tube-amp base....as if my amp won't weigh enough. Try to hammer a nail in the stuff(Used for outdoor fenceposts)...it gets in about 6mm & bends your nail, irregardless how big a nail you use!
_____________________________________________________Rick.........
On the wood front...I'll harp again on my favorite wood that most nations cannot get due to export laws here. Quebracho AKA "Axe Breaker" (Colorado red) An "Ironwood" that grows almost exclusively down here. It has export restrictions here but we have it for firewood....go figure. I will be using it for my tube-amp base....as if my amp won't weigh enough. Try to hammer a nail in the stuff(Used for outdoor fenceposts)...it gets in about 6mm & bends your nail, irregardless how big a nail you use!
_____________________________________________________Rick.........
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so how is it on high speed tooling, and what are movement /shrinkage properties like for making a speaker box?
The Home Depot' near me carry a very good quality ply that i would put against the baltic birch 5' x 5' I have bought. I have cut up 3 sheets of it in both 1/2" and 3/4", and have yet to find an air pocket. Yet to find anything like it at lowes. the 1/2" is $40 compared to $90-$110 for baltic birch and you get more on top of that. It is not likely that you will build just one pair. I use either 3/4" ply or solid lumber for baffles. FYI, I do not have 1/100th the experience of any of these other guys, but i have yet to hear a significant difference if cabinet is well made and braced.
Machine tooling really is the only way to work this stuff. I tried rounding off some corners with a flat rasp....Hah! The stuff just laughed at me. Next I tried a grinding wheel, a benchtop variety, standard type. The wood refused to "remove" itself from the parent material, it just sat there & 'burned'.
Check the properties of the stuff, there are sites which will give you statistics, I believe it is No.2 on the weight rating, a tight grain, a deep gorgeous red, somewhat Walnut type color....but the grain is tighter.
There is an outlet down the street here that is adjacent to a larger "woodstore"......it's almost as if it is the stuff is premium...deserving of its own stores to sell the stuff. A 100mm..X100mm X 2M post runs ya some 90 Pesos, or $20+ USD. I consider that outstanding considering its peers.....seen some Ebony in bulk lately??
I would love for someone outside of my country....that I can communicate with....have me send out a chunk for someone to work on.....Someone with some tooling. Any ideas??
___________________________________________________Rick.........
got a close up picture of laminated "edge grain"?
my situation is somewhat reversed, and of course trade pricing on materials can demonstrate the mark-up / profit margins at retail level - for shop grade 5x5ft 18mm Baltic Birch I'm paying $42, for Murphy Hardwoods 18mm mult-iply 4x8 C2 W1S $84 --very nice stuff, and for some breakouts actually better yield than the 5x5s
as for not hearing the differences that bracing can make - others may well have different anecdotes to share
quoted with permission from a recent builder of the following enclosures:
These are Eminence 12TAs - it's the "in an apartment" that really got me - best part of 3 4x8 or 4 5x5 sheets in this pair - and I wouldn't even want to think about the cost of veneering.
Attachments
The bracing i am referencing is that which is suggested by Dave in his plans and i completely agree about the benefits. My comment is directed at the idea that we spend a smaller percentage of money achieving 85% of the gain, and a much larger amount dialing in the last 15%.
As the happy & proud owner of the 12LTA monster above I can confirm each unit is 1.5 2440x1220mm sheets of 18mm 13 layer baltic birch - 75lb per sheet
I think baltic birch is specified as it is almost guaranteed to be voidless and so enables you to build happy in that knowledge. If the structure is riddled with pockets of random sizes between different laminations you could get all sorts of issues, not least the density of your board isn't what was originally specified fo the design.
bracing might stiffen up the cabinet but that is not going to make much difference if each wall is singing its own tune
My motto - 'always follow the maker instructions 100% - who wants 93% of the finished product?'
do you mean 85% is the brace & damping and 15% is the cabinet?
I think baltic birch is specified as it is almost guaranteed to be voidless and so enables you to build happy in that knowledge. If the structure is riddled with pockets of random sizes between different laminations you could get all sorts of issues, not least the density of your board isn't what was originally specified fo the design.
bracing might stiffen up the cabinet but that is not going to make much difference if each wall is singing its own tune
My motto - 'always follow the maker instructions 100% - who wants 93% of the finished product?'
do you mean 85% is the brace & damping and 15% is the cabinet?
$275 in timber (£59 per sheet x3 inc.VAT) for mine. To save some money I'd have to use 25mm MDF for the same rigidity thats 121lb a sheet. My speakers already weigh over 100lb each with 1.5 sheets of 18mm ply
I think I understand you now.
You'd be hard pressed to work it differently and end up spending a fair amount remedying/correcting - extra bracing etc screwing up the internal volume & air movement etc etc
Dave & Chris' designs are 'whole package' designs. I would feel I had done them (and myself) a disservice if I hadn't followed the design to the letter and at the very least would be wondering what they 'should' sound like
I think I understand you now.
You'd be hard pressed to work it differently and end up spending a fair amount remedying/correcting - extra bracing etc screwing up the internal volume & air movement etc etc
Dave & Chris' designs are 'whole package' designs. I would feel I had done them (and myself) a disservice if I hadn't followed the design to the letter and at the very least would be wondering what they 'should' sound like
I don't think you'll find a lower cost, equal quality ply, even when taking cost effectiveness into account. BB is slow grown, nearly 100% void free, with the highest face quality (mine are A/BB), very high dimensional stability, and i think the most laminations for thickness. How much we are willing to spend on our projects however is a personal matter - and possibly getting it past the other half
I'm in the do it once, do right camp. These may well be my last speaker so I spec'ed it as I wanted. I personally see no point compromising on quality/cost in construction and then trying to make up for it by spending more money & time when it could have been done right first time - that to me is an exercise in futility. But again - How much we are willing to spend on our projects however is a personal matter
Under no circumstances is this to be taken personally - it's my point of view, mine, all mine
I'm in the do it once, do right camp. These may well be my last speaker
so I spec'ed it as I wanted. I personally see no point compromising on quality/cost in construction and then trying to make up for it by spending more money & time when it could have been done right first time - that to me is an exercise in futility. But again - How much we are willing to spend on our projects however is a personal matterUnder no circumstances is this to be taken personally - it's my point of view, mine, all mine
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