I use a jasper circle cutting jig. It is not the greatest tool, but it is a tool, and it does work. It requires the user to insert a steel pin into the jig, and into the workpiece every time a pass is made. For the above tweeter hole, the correct pin setting was 2 15/16". When I flipped over the baffle, I inserted the pin into the 3 15/16" pin hole by mistake.
@hifijim: Good Work and also epic that you put time into explaining all the stuff you. DIY when it is best.
Maybe a bit late to the party, but I would also put some effort into sealing the tweeter from the bass, in regards to Air.
I have not seen experiments to confirm it, but Im almost certain most if not all tweeters with sealed backchamber also by design let Air out/in.
Nail-gun I would think is very fast fixing the Wood. I have also used the trick with cutting nails off to avoid the whole thing sliding. My experience is that sometimes stuff Can still slide during the glueing.
Last summer I tested using dowels and even though that requires a bit more effort , I Can say that was the first time I experienced COMPLETE stress free glueing!
Maybe a bit late to the party, but I would also put some effort into sealing the tweeter from the bass, in regards to Air.
I have not seen experiments to confirm it, but Im almost certain most if not all tweeters with sealed backchamber also by design let Air out/in.
Nail-gun I would think is very fast fixing the Wood. I have also used the trick with cutting nails off to avoid the whole thing sliding. My experience is that sometimes stuff Can still slide during the glueing.
Last summer I tested using dowels and even though that requires a bit more effort , I Can say that was the first time I experienced COMPLETE stress free glueing!
Thanks for your thoughts.
Whenever I am concerned about alignment while glueing, I use temporary screws. I first clamp the joint (no glue) and position it exactly the way I want it. In the case of an outer baffle, I have carefully cut the panel to be exactly the size I need, including any slight non-orthogonal corners or non-parallel edges. I want it to fit exactly flush. After carefully clamping it down, I will drill 4 pilot holes, and run 4 screws with washers. Then I back the screws out, but leave the points exposed by 1/8 inch (3mm). During glue up, I let the screws find their holes, and carefully press the panel in place, then run the screws into place, but not tight. I then clamp everything up, and slowly, alternatingly, tighten each clamp a little at a time, and also tighten the screws slowly. The goal is to get even, smooth, simultaneous squeeze out on all sides. When the clamps are removed, the screws are also removed, leaving a small hole to be filled later.
This technique is common in boat building. It is not often used in furniture making or cabinet making, but really there is no downside as long as the sheet material is going to be covered in paint or veneered. It is easier than dowels, and the positioning is very precise. Only in cases where the plywood's outer veneer layer is going to be finished off is this method no good.
j.
Whenever I am concerned about alignment while glueing, I use temporary screws. I first clamp the joint (no glue) and position it exactly the way I want it. In the case of an outer baffle, I have carefully cut the panel to be exactly the size I need, including any slight non-orthogonal corners or non-parallel edges. I want it to fit exactly flush. After carefully clamping it down, I will drill 4 pilot holes, and run 4 screws with washers. Then I back the screws out, but leave the points exposed by 1/8 inch (3mm). During glue up, I let the screws find their holes, and carefully press the panel in place, then run the screws into place, but not tight. I then clamp everything up, and slowly, alternatingly, tighten each clamp a little at a time, and also tighten the screws slowly. The goal is to get even, smooth, simultaneous squeeze out on all sides. When the clamps are removed, the screws are also removed, leaving a small hole to be filled later.
This technique is common in boat building. It is not often used in furniture making or cabinet making, but really there is no downside as long as the sheet material is going to be covered in paint or veneered. It is easier than dowels, and the positioning is very precise. Only in cases where the plywood's outer veneer layer is going to be finished off is this method no good.
j.
Back in post 229 I said that when the time came to cut tapered bevels, I would take a lot of photos and explain how I do it.
https://www.diyaudio.com/community/threads/compact-low-cost-active-3-way-speaker.402812/post-7454511
The first time I did tapered bevels, I was building a tower speaker. I learned a lot from that experience. The way I cut bevels now reflects the lessons learned from that project.
https://www.diyaudio.com/community/threads/new-project-tower-3-way-with-twin-8s.378223/post-7048860
I am sure that other people do a better, more efficient job of machining tapered bevels. This is the method that seems to work best for me, given my tools and my skills.
Bevel design
The bevels are designed to have 51 mm (2 inch) of width around the tweeter. The bevel angle relative to the front baffle is 35 degrees. This matches the prototype I tested back in post 314
https://www.diyaudio.com/community/threads/compact-low-cost-active-3-way-speaker.402812/post-7471898
The side tapered bevel begins at the top of woofer recess hole and extends to the top of the cabinet, a length of 355 mm.
I find it very helpful to mark the cabinet with all cut lines for the side and top bevels.
Making the jig
The table saw blade will be set at an angle of 35 degrees. The cabinet will be pushed through the saw on its side. The cabinet angle relative to the fence is 8 degrees.
Tan-1 (51/355) = 8 degrees
A jig is made that incorporates an 8 degree angle. I used some scrap plywood. To layout the angle with precision, I draw a right triangle on the with a leg of 355 mm and a leg of 51 mm. I find this much more accurate than trying to replicate the angle with a protractor.
L-brackets are used to attach the jig to the back of the cabinet. Roundhead screws with washers are used so that the jig can be adjusted against the cabinet back for a snug fit.
j.
https://www.diyaudio.com/community/threads/compact-low-cost-active-3-way-speaker.402812/post-7454511
The first time I did tapered bevels, I was building a tower speaker. I learned a lot from that experience. The way I cut bevels now reflects the lessons learned from that project.
https://www.diyaudio.com/community/threads/new-project-tower-3-way-with-twin-8s.378223/post-7048860
I am sure that other people do a better, more efficient job of machining tapered bevels. This is the method that seems to work best for me, given my tools and my skills.
Bevel design
The bevels are designed to have 51 mm (2 inch) of width around the tweeter. The bevel angle relative to the front baffle is 35 degrees. This matches the prototype I tested back in post 314
https://www.diyaudio.com/community/threads/compact-low-cost-active-3-way-speaker.402812/post-7471898
The side tapered bevel begins at the top of woofer recess hole and extends to the top of the cabinet, a length of 355 mm.
I find it very helpful to mark the cabinet with all cut lines for the side and top bevels.
Making the jig
The table saw blade will be set at an angle of 35 degrees. The cabinet will be pushed through the saw on its side. The cabinet angle relative to the fence is 8 degrees.
Tan-1 (51/355) = 8 degrees
A jig is made that incorporates an 8 degree angle. I used some scrap plywood. To layout the angle with precision, I draw a right triangle on the with a leg of 355 mm and a leg of 51 mm. I find this much more accurate than trying to replicate the angle with a protractor.
L-brackets are used to attach the jig to the back of the cabinet. Roundhead screws with washers are used so that the jig can be adjusted against the cabinet back for a snug fit.
j.
Setting up the saw
Before using the saw to cut large heavy workpieces (like an assembled cabinet), I apply wax to the table saw fence and table to minimize friction.
I set the saw blade to 35 degrees and raise it to its maximum height. I make a lot of practice pushes through the saw (blade fully retracted) to make sure the jig clears the fence, and there is no opportunity for anything to get caught up or pushed out of alignment. No part of the cabinet should touch the fence, only the jig touches the fence. I also carefully arrange my outfeed and infeed rollers to support the cabinet as it goes into, and comes out of, the saw.
Cutting the tapered bevels
I attached the jig to the back of the speaker. The left hand bevel is cut by placing the left side of the cabinet against the table, baffle facing the blade. The cabinet is fed into the blade bottom first. This means the blade starts by cutting the thinnest section of wood, but finishes by cutting the thickest.
When cutting the right hand bevel, the jig must be attached to the opposite side of the cabinet, and the jig itself must be flipped over and the L brackets attached to the opposite side. The right side of the cabinet is against the table, and the cabinet is fed into the blade top first. This means the blade starts by cutting the thickest section, and finishes by cutting the thinnest section.
I do not attempt to cut the full bevel in a single pass. My saw is very “old school” and it has no CNC features or any sort of precision measurement system built in. I mark lines on the work piece, and then I cut to the line. In the case of a big complex cut such as this, I slowly “walk” myself up to the line by making a series of cuts. I start by cutting about ½ of the cut width, and then carefully examining the finished cut to be certain everything is lining up. If there is an alignment or setup problem, I usually will have plenty of remaining cabinet material to make adjustments and continue. I continue to progress with deeper cuts, about ¼ inch at a time (6 mm). The final cut should be less than the width of the blade, and this ensures the smoothest possible cut.
It is absolutely critical that the jig maintain contact with the fence during the entire operation. It takes some force to push the cabinet through the blade, and it is easy to accidently push things out of alignment. It is best to practice pushing the cabinet across the saw table before using the blade.
Cutting the top bevel
The top bevel is easier than the tapered side bevels, although it looks more intimidating. The speaker is placed top down against the table surface, with the baffle facing the blade. No jig is used, and the back of the cabinet is against the fence, and the bevel cut is parallel to the baffle. Once again I recommend practicing the motion first, and then making a first cut that is only half depth. Then walking up to the final cut line.
Why cut the top bevel last? When cutting the right hand tapered bevel, the top of the speaker goes in first. If the top bevel has already been cut, it would be very difficult to see the mark lines and position the line up to the saw blade. So I do the bevels first.
My final resulting cuts are close to the mark line, but not exact. This process is very sensitive to the angle of the jig, and how closely it matches the design angle. However, it is not so important that the actual cuts match the intended design, only that all four cuts are the same, and in this case I was successful.
j.
Before using the saw to cut large heavy workpieces (like an assembled cabinet), I apply wax to the table saw fence and table to minimize friction.
I set the saw blade to 35 degrees and raise it to its maximum height. I make a lot of practice pushes through the saw (blade fully retracted) to make sure the jig clears the fence, and there is no opportunity for anything to get caught up or pushed out of alignment. No part of the cabinet should touch the fence, only the jig touches the fence. I also carefully arrange my outfeed and infeed rollers to support the cabinet as it goes into, and comes out of, the saw.
Cutting the tapered bevels
I attached the jig to the back of the speaker. The left hand bevel is cut by placing the left side of the cabinet against the table, baffle facing the blade. The cabinet is fed into the blade bottom first. This means the blade starts by cutting the thinnest section of wood, but finishes by cutting the thickest.
When cutting the right hand bevel, the jig must be attached to the opposite side of the cabinet, and the jig itself must be flipped over and the L brackets attached to the opposite side. The right side of the cabinet is against the table, and the cabinet is fed into the blade top first. This means the blade starts by cutting the thickest section, and finishes by cutting the thinnest section.
I do not attempt to cut the full bevel in a single pass. My saw is very “old school” and it has no CNC features or any sort of precision measurement system built in. I mark lines on the work piece, and then I cut to the line. In the case of a big complex cut such as this, I slowly “walk” myself up to the line by making a series of cuts. I start by cutting about ½ of the cut width, and then carefully examining the finished cut to be certain everything is lining up. If there is an alignment or setup problem, I usually will have plenty of remaining cabinet material to make adjustments and continue. I continue to progress with deeper cuts, about ¼ inch at a time (6 mm). The final cut should be less than the width of the blade, and this ensures the smoothest possible cut.
It is absolutely critical that the jig maintain contact with the fence during the entire operation. It takes some force to push the cabinet through the blade, and it is easy to accidently push things out of alignment. It is best to practice pushing the cabinet across the saw table before using the blade.
Cutting the top bevel
The top bevel is easier than the tapered side bevels, although it looks more intimidating. The speaker is placed top down against the table surface, with the baffle facing the blade. No jig is used, and the back of the cabinet is against the fence, and the bevel cut is parallel to the baffle. Once again I recommend practicing the motion first, and then making a first cut that is only half depth. Then walking up to the final cut line.
Why cut the top bevel last? When cutting the right hand tapered bevel, the top of the speaker goes in first. If the top bevel has already been cut, it would be very difficult to see the mark lines and position the line up to the saw blade. So I do the bevels first.
My final resulting cuts are close to the mark line, but not exact. This process is very sensitive to the angle of the jig, and how closely it matches the design angle. However, it is not so important that the actual cuts match the intended design, only that all four cuts are the same, and in this case I was successful.
j.
Jim,
I notice that the butyl sheets are still pleated and showing creases in your cabinet. Have you roll-pressed them into the cabinet yet? Many manufacturers of butyl sheets put pleats in their product so the user can know that enough force has been applied when the pleats are rolled out. When dealing with a materials that has an uneven surface like wood, I would recommend using a metal corrugated roller like this one:
https://www.amazon.com/Norsmic-Dead...lpcontext&ref_=fplfs&smid=A3LR7MTFDFPOY1&th=1
Cheers and thanks for the excellent write up!
Those pleat markings you see in the photo are mostly a trick of the light. I pressed them down, but some markings are still visible in the right light.
For some panels, I rolled/pressed them flat, but other panels I used a 3 lb hammer and a block of wood and pounded the material to get a good bond. The hammer method does not completely remove the crease marks, but it does give great adhesion.
j.
For some panels, I rolled/pressed them flat, but other panels I used a 3 lb hammer and a block of wood and pounded the material to get a good bond. The hammer method does not completely remove the crease marks, but it does give great adhesion.
j.
Absolutely they do Jim!
Now; If you are interested in capturin you workflow as you navigate through VituixCAD2, please start a conversation with me,
We can work together on producing a series of videos that can be recorded and put onto Udemy or YouTube assist others.
And to to get your voice narration and capture for mouse movements whilst you work on VituixCAD2, well feature is already built into Windows!
I still feel as though I am learning something new every time I do a simulation with VituixCad2... I feel I do not have the expertise or experience to make a Vcad video.
But it is something to keep in mind for ... someday perhaps...
I added an index and a sketch to the original post #1.
I have been thinking about what I might do with these speakers once they are built/tested/developed. I don't have a place for them in my main listening area, and I already have nice speakers in my office. I think the primary use for these will be easily portable speakers, but the secondary duty will be to provide high quality sound in my basement workshop.
Given the workshop environment, being loaded in and out of cars, trucked around town, I decided on a simple utilitarian finish. I painted them with kitchen cabinet paint. The color is a dark blue, but not quite navy blue. I did not use a sanding sealer, I just smoothed out some dents/scratches/marks with spackling compound and sanded with 100 grit paper. I applied 4 coats, using a small foam roller.
I have been thinking about what I might do with these speakers once they are built/tested/developed. I don't have a place for them in my main listening area, and I already have nice speakers in my office. I think the primary use for these will be easily portable speakers, but the secondary duty will be to provide high quality sound in my basement workshop.
Given the workshop environment, being loaded in and out of cars, trucked around town, I decided on a simple utilitarian finish. I painted them with kitchen cabinet paint. The color is a dark blue, but not quite navy blue. I did not use a sanding sealer, I just smoothed out some dents/scratches/marks with spackling compound and sanded with 100 grit paper. I applied 4 coats, using a small foam roller.
Classic! First building something, than thinking what actually to do with them , hahahaYou muricans have an interesting concept about "portability" haha
They are starting to look nice btw!
As I said in my first post
As far as portable... in my mind, if something can be carried by two people, it is portable... If something can be caried by one person, it is easily portable.
Truth is... I love bass. I just can't figure out how to get 99 dB SPL at 40 Hz from a micro-sized cabinet.
That is the whole impetus for this project... Something that others could use as a model for their own project.
As far as portable... in my mind, if something can be carried by two people, it is portable... If something can be caried by one person, it is easily portable.
Truth is... I love bass. I just can't figure out how to get 99 dB SPL at 40 Hz from a micro-sized cabinet.
@hifijim I have a woodworking question about the alignment of the top and side bevels with the top rectangular cabinet corners: If the cuts for the top and side bevels were the same distance from the each side and top at the upper corners, And the angle was the same, would the bevel line up perfectly with the rectangular cabinet corners? Is that consistently achievable, or if not, is that a practical reason to make the bevelcorners slightly offset from the rectangular cabinet corners?
Thanks, Six.
P.S. I’m looking forward to reading how you integrate the drivers, hybrid XO and MiniDSP. I’m doing a similar experiment with my 33 years old B&W DM640’s.
Thanks, Six.
P.S. I’m looking forward to reading how you integrate the drivers, hybrid XO and MiniDSP. I’m doing a similar experiment with my 33 years old B&W DM640’s.
When it comes to tapered bevels, every cabinet geometry / tweeter location is different, so it is difficult to come up with universal rules.
Certainly it is possible that the top bevel mates up with the side bevels such that the top panel (the roof) is completely square, rather than having clipped corners. With my geometry, the top bevel angle would be increased from 35 degrees to 45 degrees. This means the top bevel would be 51 mm width and 51 mm deep, and it would meet up with the tapered side bevels. Every cabinet would be different, so we would have to work out the geometry for each case.
The hard part would be controlling the angles during machining so that these bevels match up exactly... If they don't match up exactly, it will look stupid, it will look like a mistake. With productionized jigs in a manufacturing environment, this is possible. With CNC, this is possible. With the way I do things in my shop... I have my doubts.
Certainly it is possible that the top bevel mates up with the side bevels such that the top panel (the roof) is completely square, rather than having clipped corners. With my geometry, the top bevel angle would be increased from 35 degrees to 45 degrees. This means the top bevel would be 51 mm width and 51 mm deep, and it would meet up with the tapered side bevels. Every cabinet would be different, so we would have to work out the geometry for each case.
The hard part would be controlling the angles during machining so that these bevels match up exactly... If they don't match up exactly, it will look stupid, it will look like a mistake. With productionized jigs in a manufacturing environment, this is possible. With CNC, this is possible. With the way I do things in my shop... I have my doubts.