Hello,
I am recently building Fostex Fe126En in BK-12M enclosures, as my first DIY project.
However, the physics part (the travelling of the sound wave, to be precise) is the one that I am not strong in.
So I have a few questions regarding the reflection of the soundwave (on the surfaces), and how much of the importance it has to overall quality.
1. The material/covering of the inner surface of the enclosure:
In the original build of BK-12M (KIT) the plywood is used: The Madisound Speaker Store
However, I am using MDF, which already has some priming on in (please see the image: imgur: the simple image sharer), so should I consider covering ALL the inner walls with a thin acousting stuffing additionaly to the two suggested stuffings (the suggested ones are provided here: http://www.madisound.com/pdf/bk12m-cab.pdf), or the reflectivness of primed MDF is only for the better, compared to plywood, and I should leave it as it is (e.g. no additional thin covering)?
For the inner walls I saw some thin material applied in some places of the inner walls of the enclosures in some of DIY projects (for example: _1015529-800x800_zpsf204c4db.jpg Photo by chad1376 | Photobucket), so I was wondering, why not cover all the inside?
2. The second question is more general: when (in the inside of the eclosure) the good reflectivness of a sound is a good thing, and when it should be avoided? Or in a more simple manner: in which parts (of the BK-12M build, if the special example is needed) I should try to decrease the reflectivness (additional stuffing and so on) and in which parts I would try to increase it?
3. And finaly... In the KIT, the hole for the speaker is widened in the inner side (compared to the diameter in the outer side). Is that important and why?
I know, that some general testing would solve the problem, however, the glueing and then unglueing the thin material on the inner walls might cause some additional problems (like glue, which would be left behind and so on).
Many thanks in advance,
Fortaz
I am recently building Fostex Fe126En in BK-12M enclosures, as my first DIY project.
However, the physics part (the travelling of the sound wave, to be precise) is the one that I am not strong in.
So I have a few questions regarding the reflection of the soundwave (on the surfaces), and how much of the importance it has to overall quality.
1. The material/covering of the inner surface of the enclosure:
In the original build of BK-12M (KIT) the plywood is used: The Madisound Speaker Store
However, I am using MDF, which already has some priming on in (please see the image: imgur: the simple image sharer), so should I consider covering ALL the inner walls with a thin acousting stuffing additionaly to the two suggested stuffings (the suggested ones are provided here: http://www.madisound.com/pdf/bk12m-cab.pdf), or the reflectivness of primed MDF is only for the better, compared to plywood, and I should leave it as it is (e.g. no additional thin covering)?
For the inner walls I saw some thin material applied in some places of the inner walls of the enclosures in some of DIY projects (for example: _1015529-800x800_zpsf204c4db.jpg Photo by chad1376 | Photobucket), so I was wondering, why not cover all the inside?
2. The second question is more general: when (in the inside of the eclosure) the good reflectivness of a sound is a good thing, and when it should be avoided? Or in a more simple manner: in which parts (of the BK-12M build, if the special example is needed) I should try to decrease the reflectivness (additional stuffing and so on) and in which parts I would try to increase it?
3. And finaly... In the KIT, the hole for the speaker is widened in the inner side (compared to the diameter in the outer side). Is that important and why?
I know, that some general testing would solve the problem, however, the glueing and then unglueing the thin material on the inner walls might cause some additional problems (like glue, which would be left behind and so on).
Many thanks in advance,
Fortaz
Acoustic lining will not help fight the downsides of using MDF. You'll need to user thicker material, more bracing,orcoat the MDFin something tostiffen it (epoxy or fiberglass resin, plastic laminate...) or a combination.
You live right in the backyard of where Baltic Birch ply is made, you can't get any?
dave
You live right in the backyard of where Baltic Birch ply is made, you can't get any?
dave
As to the other question regarding "enlargement" of the rear side of driver cut-out: yes that's very helpful in reducing cavity resonances and very early diffractions when front mounting small diameter FR drivers on baffles as thick as 3/4", or the nominal metric equivalent of 18-19mm.
I wouldn't surface mount any of the Fostex 3 -4" drivers on material thicker than 9mm without as deep a chamfer as the bearing clearance on my router bit would allow.
As to BB vs MDF, it's the much higher stiffness per unit of thickness that serves the purpose here, and IINM the designer of the BK12 had that quality in mind when detailing the enclosure
I wouldn't surface mount any of the Fostex 3 -4" drivers on material thicker than 9mm without as deep a chamfer as the bearing clearance on my router bit would allow.
As to BB vs MDF, it's the much higher stiffness per unit of thickness that serves the purpose here, and IINM the designer of the BK12 had that quality in mind when detailing the enclosure
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Many thanks for the answers, I really appreciate them.
Unfortunately, I already have MDF cut-outs, and the plywood was not an option as per design issues in the room
The answer to the question NO3 is really clear, and I will make a larger as possible widening of the inner hole.
However, the questions 1+2 are left a bit open...
I fully understand, that MDF worse than PlyWood because of the thickness (I read about it numerous articles).
However, I really do not understand the general idea of the way how sound wave travels (because in some places the stuffing is added, and in some it is not - how are these places picked?), e.g. when you need a good reflection properties, and when you don't?
For example here: _1015529-800x800_zpsf204c4db.jpg Photo by chad1376 | Photobucket the white stuff is the recommended one, however, the red one is additional (plywood is used, as recommended).
So why wouldn't you want to cover ALL the inner walls with red material?
E.g. I am not asking about how to reduce downsides of MDF as material. I am asking if I should bother about the fact that the inner walls of my enclosure are mirror-like (very reflective) - not like ply wood.
To simplify the question, let's say I would use plywood, which is covered with reflective paint on both sides - how would (if, at all) I want to fix this (removing paint is not an option)? Wadding/linning? But in which parts? Everywhere? Or it would not have any effect?
Unfortunately, I already have MDF cut-outs, and the plywood was not an option as per design issues in the room
The answer to the question NO3 is really clear, and I will make a larger as possible widening of the inner hole.
However, the questions 1+2 are left a bit open...
I fully understand, that MDF worse than PlyWood because of the thickness (I read about it numerous articles).
However, I really do not understand the general idea of the way how sound wave travels (because in some places the stuffing is added, and in some it is not - how are these places picked?), e.g. when you need a good reflection properties, and when you don't?
For example here: _1015529-800x800_zpsf204c4db.jpg Photo by chad1376 | Photobucket the white stuff is the recommended one, however, the red one is additional (plywood is used, as recommended).
So why wouldn't you want to cover ALL the inner walls with red material?
E.g. I am not asking about how to reduce downsides of MDF as material. I am asking if I should bother about the fact that the inner walls of my enclosure are mirror-like (very reflective) - not like ply wood.
To simplify the question, let's say I would use plywood, which is covered with reflective paint on both sides - how would (if, at all) I want to fix this (removing paint is not an option)? Wadding/linning? But in which parts? Everywhere? Or it would not have any effect?
If I might second guess the designer ( Scott), it's the BB/"Apple" ply's stiffness that serves the purpose here - thickness / mass are not always an attribute.
I did build a pair of the BK12s a while back, but to be completely honest, can't remember how much if any panel wadding and or acoustic fibre fill was used. If Dave still has them kicking around, he might take a peek.
If anything like the dozens of other BLH types I've made, at least a layer of 1/2" or so material on the back & maybe top wall of driver chamber?
Any particular reason why the plywood would be painted, or what "design" issues would preclude its use?
I did build a pair of the BK12s a while back, but to be completely honest, can't remember how much if any panel wadding and or acoustic fibre fill was used. If Dave still has them kicking around, he might take a peek.
If anything like the dozens of other BLH types I've made, at least a layer of 1/2" or so material on the back & maybe top wall of driver chamber?
Any particular reason why the plywood would be painted, or what "design" issues would preclude its use?
Right; they're intended for birch ply or similar so panel resonance is basically insignificant & no panel damping specified or needed. The pdf http://www.madisound.com/pdf/bk12m-cab.pdf sets the driver chamber as damped & a lighter layer around the vertical bend at the top of the box. This can be altered to lining the top, back, bottom & one side of the driver chamber with ultratouch, acoustic fiberglass or similar, & the top around that bend with the same. Adjust to suit your own preference from there. All you're wanting to do is absorb the unwanted higher frequencies from passing through the horn -it doesn't take much.
polyfluff in the air cavity, nothing else IIRC.
Thay are still here, and can be had for Madisound flat-pak price with EnABLed drivers.
Thank you.
By "design" I mean, that the interior of my home really asks for glossy white fasades to dominate - I would not be able to achieve it with ply. But that's more of an offtopic here, I have no way around it.
Additionally to lining I will try to add some additional bracing inside.
This one is really helpfull, thank you.
Will try to do just that - add the lining to all the possible places inside the chamber except one sides, yes?
There are more than a few commercial speakers that use high gloss plastic laminate ( "Formica" / "Arborite" etc) to achieve that look. There are solid color-through versions that won't leave the brownish to black line on exposed edges of normal P-Lam
And with appropriate sanding / filling and the correct choice of high solid fill primers and finish paint, you can achieve a high gloss paint finish on plywood as well.
That said, why not depart from that look altogether, and go for the look of real wood on the speakers? They'll call attention to themselves sonically, why not let them make a statement of visual counterpoint as well?
And with appropriate sanding / filling and the correct choice of high solid fill primers and finish paint, you can achieve a high gloss paint finish on plywood as well.
That said, why not depart from that look altogether, and go for the look of real wood on the speakers? They'll call attention to themselves sonically, why not let them make a statement of visual counterpoint as well?
Thanks, Chris.
This is my first DIY, so the MDF was the easiest solution as per input/result ratio (at least I assume).
I have some plans for the wooden thing, tho, that you mentioned - hope this one will be my second: the so called attention-seekers on my desktop - but those will be only small (50cm in high, tops) speakers.
Still, this one is only in the books, and for BK-12M I already have cut-outs (in MDF, though).
This is my first DIY, so the MDF was the easiest solution as per input/result ratio (at least I assume).
I have some plans for the wooden thing, tho, that you mentioned - hope this one will be my second: the so called attention-seekers on my desktop - but those will be only small (50cm in high, tops) speakers.
Still, this one is only in the books, and for BK-12M I already have cut-outs (in MDF, though).
Sorry, if it is not educated question, but how does the laminate (which is sound-reflective) help to overcome the short-comings of MDF?
Fortaz
It's not about just "sound reflective " characteristics, but the stiffness of the composite layers . Plastic laminate ( particularly the thicker "general purpose" grade) will help in that area, but having built more than a few hundred pairs of speakers over the past few years, I've concluded that for my own purposes the lower cost of MDF is not a price I'm willing to pay.
MDF seems like the final solution at first. And we think thicker is better. I'm not sure anything but experience will teach otherwise. It's the downside of the alleged "scientific method." That is, in the dumbest case, only one factor will be considered at a time. Like going to a doctor in the USA. So if plywood is stiffer yet better damped, all at once, and lighter, whoa! Too much at once! And then to say that a gloss finish can be done on ply? Stop it! Wait...cheaper at BigBox. That's the ticket.
Forgive the attitude; I got sucked in myself. MDF will do for beginners.
Forgive the attitude; I got sucked in myself. MDF will do for beginners.
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