It's a saw which blade does not rotate but oscillates instead. It's much safer and got two main advantages, if it touches the skin, the skin isn't instantly cut because of the much lower velocity and the elasticity of the skin, it's only moved a few mm back and forth. Because it doesn't rotate it can't build up as much kinetic energy like a circular saw and moves just a short distance, it can't kick back like a circular saw.
It looks often like this.
It got another practical advantage, you can cut flush at a surface, or do a dive cut which you can't with most other saws.
What about about placing the eva in place and then wrapping some thin linoneaum or other type of "veneer" around it?
Google "oscillating saw". They are handy for many things.
On the edge roundness, here is an interesting article/study, although it is using a planar dipole, it helped me understand the effect and the importance of varying the distance from the driver to the edge treatment. Maybe you are already aware of it.
ALSR - The RD75 Dipole Baffle Study - Table of Contents
Well, they can't replace each other in any way. They are cheap (well, the Bosch maybe not 🙄), I've seen them for below 25 bucks, I'm sure everyone who builds speakers can afford them. 😉 They are extremely handy if you have to change/cut something in an existing speaker enclosure.
Just use MDF and a router table with the proper bit. PVC is likely going to add discoloration to the sound especially if it is left open on the ends as it will be a resonate chamber. It's good for prof of concept or in this case moding a commercial speaker but there are much better ways of rounding over speaker cabs if your making them from scratch. The one draw back is the price of a decent quality router bit for doing 2" round overs. They can get real pricey.
And a router big enough to swing it. If you can afford the enclosure width for a 2" radius, (aren't looking for a min-width baffle, as many are) then a bevel is effectively equivalent to a roundover, maybe the tiniest smidge less so, and is done just fine on a tablesaw or with a circular saw and straight edge.
I imagine that any kind of saw is going to get grabbed when PVC gets cut through longways on one side from all the inward clamping tension it has. Probably only the circular saw or table saw risk kickbacks (which can be WAY dangerous) from that, but you may find yourself prying the cutting thing out from the clamping pipe tension. Cutting about half way through one side, then halfway through the opposite side of the pipe, then back to the first side, then maybe back and forth a few times more, will reduce the amount of the clamp. When I did it (successfully, finally) I bolted the pipe onto a thick square wooden post and used that to align the cut to one place and flip to the opposite side.
After all that, then you find how much of pain it is to attach or glue PVC to wood. PVC doesn't like most glues and PVC pipe "glue" doesn't do anything to wood.
After all that, then you find how much of pain it is to attach or glue PVC to wood. PVC doesn't like most glues and PVC pipe "glue" doesn't do anything to wood.
And that's warning #2 in this thread. Bill ain't kidding. I near lost my manhood on a tablesaw kickback some years ago, and that was just regular ply. Safety first, and PVC is not a fun material to work with.
Yup. My adventure was a big bruise that I persevered through for a couple of years, then came down with all the symptoms of a particularly deadly cancer with bad prognosis. Months of prep then major surgery, but finally found to not have cancer but instead a blocked bile duct from internal scarring. The surgery and pain meds messed me up pretty badly, ending with me having to retire early. Couldn't stay awake at my desk for full days so gave up. It wasn't until a few years back when I was working with a table saw and remembered the drama with the PVC and where it hit me when it kicked back and I realized what the cause probably was.
So, don't do anything as stupid as I did!
So, don't do anything as stupid as I did!
That's an amazing, and frightening story. Mine was a function of carelessness and a **** poor workspace (tiny porch area, building big speakers). I don't think there's been any lasting effect, though I haven't tried to sire any children since the event. Now that I own a home I can operate with more room to work, which helps with safety.
There are better ways to roundover a DIY cabinet, but it has nothing to do with any potential resonance of the uncapped PVC. I measured with and without the PVC stuffed and found no difference. I also stuck a mic in the PVC to look for any narrowband resonance... still nothing. Both ends open to the same space, with the same pressure (at least at low frequencies). The other ways of making roundovers are "better" purely for aesthetic reasons. The advantage of PVC is that it can be added to a finished speaker, and it's completely reversible if you strap it on, rather than glue it on.
The major point of the project was to show the importance of the large roundover by having a version with and without it that could be compared. How you get there is entirely up to you.
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It's easy to cut on a table saw. You just have to screw it to a squared piece of lumber like a 2" x 4". The 2 X 4 has to be a little longer than the PVC you are cutting and the PVC needs to be a bit longer than you need so you can put one screw at each end of the PVC to attach it to the 2 X 4 and cut to final length later.
You just put the 2 X 4 against the fence and the PVC next to it. Then drill one hole on one end and attach it with a screw where the PVC touches the wood. Now do the other side and you are ready to cut. This is also the only way you are going to get straight cuts. Just cut through one wall at a time keeping the blade up just high enough to make it through and you shouldn't have any problems with kick back. But always respect the table saw because it can hurt you faster then any other tool in the shop. I've been using them for the last 35 years and still have all my fingers.
I understood the point of the project. You had a commercial speaker that you modified to demonstrate the effectiveness of large round overs. I wasn't being critical of your project or your use of PVC as it where. My comment was directed more at everyone else who where talking about using PVC for large round overs in new cabs. It can be difficult making 2" round overs out of MDF if you don't know how to do it and/or don't have the necessary tools so I can understand it.
But as far as resonance goes PVC isn't very damped. So how can it not have a resonant frequency somewhere in the audible band? You say you looked for narrow band resonances and didn't find any hun? That's surprising. What did you do just run loud sine wave sweeps to see if you could get it to ring?
Of course any resonances if they did show could be damped easily enough.
I have used, paper tubes for concrete, e.g.
https://www.homedepot.com/p/SAKRETE...PIPHorizontal2_rr-_-100324386-_-100321209-_-N
Kindest regards,
M
https://www.homedepot.com/p/SAKRETE...PIPHorizontal2_rr-_-100324386-_-100321209-_-N
Kindest regards,
M
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