The material is pretty thin and very flexible so I think it's a good idea to either strengthen it as much as possible using multiple layers and bracing. I used quite a few layers of fibreglass, sand and fibreglass resin and fillite powder with fibreglass resin before applying a 10mm layer of felt to the inside. Effectively, I built up lots of sealed layers inside the cabinets.
I can actually stand on the sides and bounce up and down without any movement (that took some courage to try though
)
I think applying some kind of resin or water proofer is a good plan because I guess bendy MDF is pretty good at absorbing moisture because of its large surface area plus the MDF isn’t that hard (compact?) compared to other MDF I’ve used.
One thing I'd like to try is applying resin to the outer layer and then a layer of soft silicone or similar followed by other internal layers to give structural rigidity which should isolate the outer skin nicely.
From what I can tell there isn't any appreciable resonance and I don't get any type of MDF signature colouration, certainly not compared to other speakers I built. I think the project was successful, well, within realms of any goals I’m likely to be able to achieve anyway.
All I need to do now is stop listening to them so I can finish painting them
I can actually stand on the sides and bounce up and down without any movement (that took some courage to try though
)I think applying some kind of resin or water proofer is a good plan because I guess bendy MDF is pretty good at absorbing moisture because of its large surface area plus the MDF isn’t that hard (compact?) compared to other MDF I’ve used.
One thing I'd like to try is applying resin to the outer layer and then a layer of soft silicone or similar followed by other internal layers to give structural rigidity which should isolate the outer skin nicely.
From what I can tell there isn't any appreciable resonance and I don't get any type of MDF signature colouration, certainly not compared to other speakers I built. I think the project was successful, well, within realms of any goals I’m likely to be able to achieve anyway.
All I need to do now is stop listening to them so I can finish painting them
I used bendy MDF for my main speakers, (pics in the UK diyfest thread somewhere). Firstly I tried using two layers separated by about 2cm, then filling the void with expanding foam. Unsuccessful as the foam failed to fill the gaps properly. Then I rebuilt them and filled the void with dry sand, but that didn't seem to reduce the resonance that much. For the third, and final attempt, I used one layer, smooth side in, then rendered the outside with 3/4" sand and cement render, with added PVA for grip and crack resistance. That was finished with faux aluminum chequerplate flooring vinyl, resulting in a completely dead box.
I didn't say you did or didn't have any knowledge about high end car audio. But from your statement about using a car installer as a reference and a rolls eyes, it could be inferred that either you think down on car guys, or know little about them, or you are a snob.
But since you brought it up, what do you know about high end car audio and installation?
But since you brought it up, what do you know about high end car audio and installation?
MJL21193 said:
winslow said:
I am a bit of a snob, that's for sure.
Here's what I know about high end car audio installers: If they are willing to used kerfed plywood to create a curved panel to use for an enclosure, they are either lazy or prefer to do things the wrong way.
I have used kerfed panels many times in the past in my line of work, but I've never used one for a speaker. Curved panels are best made with thin solid layers, glued and built up to the desired thickness.
Layers have bettr damping properties than either voids (kerfs unfilled) or inconsistant material (kerfs filled with gunk)
How's that?
MJL21193 said:I am a bit of a snob, that's for sure.
Here's what I know about high end car audio installers: If they are willing to used kerfed plywood to create a curved panel to use for an enclosure, they are either lazy or prefer to do things the wrong way.
I have used kerfed panels many times in the past in my line of work, but I've never used one for a speaker. Curved panels are best made with thin solid layers, glued and built up to the desired thickness.
Layers have bettr damping properties than either voids (kerfs unfilled) or inconsistant material (kerfs filled with gunk)
How's that?
But John, where did I state that the tape I watched showed the installer using plywood? Go back and reassess the post. I never stated such.
In fact, the tape clearly shows the installer using MDF, making individual crosscuts with the table saw, making a loose fit, then mixing and applying Bondo before using a brad gun to attach the kerfed piece to the frame. Then he neatly scraped off the excess Bondo that has bled out from the squeezed cuts.
If you did not see the tape you could not begin to understand just how solid, and neat, the kerfed wall would become. The job was Very Professional and looked a million dollars. Plus it was rock solid.
I'm a firm believer in using bondo filler for kerfed cuttings. I can't think of a better means of engineering a solid rounded wall, and I stand by my assessment. clearly the fellow making the tape was a genuine expert.
What more can I say?
If you liked the NAME stuff, then you would really dig the Select Products videos. I had nearly all of the NAME tapes back in 94 or so...they were pretty good for the time, especially since there was no internet to ask questions on and the pros weren't giving out any of their tips. NAME started going downhill when the internet started growing.
And if you want to check out the Select Products videos (skip the wood working and basic router ones), then rent them at http://smartflix.com/
They have a TON of DVDs to rent on pretty much about any subject you can think of.
And if you want to check out the Select Products videos (skip the wood working and basic router ones), then rent them at http://smartflix.com/
They have a TON of DVDs to rent on pretty much about any subject you can think of.
John L said:
Hi John,
I think I can begin to understand. This subject isn't over my head, friend. Without bragging, I think it's fair to say that my knowledge on box construction methods is extensive.
I meant kerfed material, be it plywood, MDF, whatever.
A better means to "engineer" a solid rounded wall would be the method I described above.
MJL21193 said:
I am a bit of a snob, that's for sure.
Here's what I know about high end car audio installers: If they are willing to used kerfed plywood to create a curved panel to use for an enclosure, they are either lazy or prefer to do things the wrong way.
I have used kerfed panels many times in the past in my line of work, but I've never used one for a speaker. Curved panels are best made with thin solid layers, glued and built up to the desired thickness.
Layers have bettr damping properties than either voids (kerfs unfilled) or inconsistant material (kerfs filled with gunk)
How's that?
Regardless of the car audio. John, are you talking about laminating either wiggle board or 1/8 layers of plywood?
I am not actually familiar with the term “hardboard”, unless you are referring to a thin lumber.
“Depending on the radius” is the key fraise here.
I think the question here really is where this material is beneficial. I think it is and it gives you better flexibility compare to other materials. The thing is, what do we do about kerf cuts? I’ll experiment with the leftovers after my job is finished and see what I can sandwich in between besides wiggle board (bendable luan plywood, usually 3/8. so we are on the same page).
Just of the subject. I usually do laminations by building “father” frame with the internal radius (or S contour) of the expected shape and laminate it in the vacuum press.
“Depending on the radius” is the key fraise here.
I think the question here really is where this material is beneficial. I think it is and it gives you better flexibility compare to other materials. The thing is, what do we do about kerf cuts? I’ll experiment with the leftovers after my job is finished and see what I can sandwich in between besides wiggle board (bendable luan plywood, usually 3/8. so we are on the same page).
Just of the subject. I usually do laminations by building “father” frame with the internal radius (or S contour) of the expected shape and laminate it in the vacuum press.
R-Carpenter said:
Hardboard is Masonite - High density fiberboard (HDF).
I'm not crazy about the density of wiggle board or the typical luan plywood. 1/8" door skin (luan) is not bad but expensive.
Best results from hardboard IMO. First building the "frame" of the box (front sub baffle, back, top, bottom and the intermediate braces) provides the form to bend the material around. Taking the time to build a reverse frame, to clamp each layer on, makes tight glue joints if you don't have vacuum bag (I don't).
R-Carpenter said:
Ok, you're going to have to be more specific here. what is GF-20? I googled it and all I came up with was arthritus stuff.
Another thing: I don't remember you contributing there with your knowledge base. Nobody knows everything. We all have our Real specialties, but can't be great at everything. Now, if you want to know all about jumping out of airplanes, or how to take someone out at 750+ metres, you've come to the right place.
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