Natalie P towers, with a twist

[Ricci]

Really interested to see how you construct the bends of the side panels. Can you explain it? Looks like it's going to be very challenging.

[jr1414]

From what I remember, he will be using bendable plywood for the sides, with the front and rear baffles acting as a form to bend them over. Bendable plywood is pretty neat stuff, although not inexpensive by any means.

[mrstampe]

what he said

[Ricci]

Will it relax into the curvature of the baffles over time, or will the ply tend to want to straighten out? Just wondering.

[mrstampe]

Bendable plywood is very compliant and can be purchased in two varieties -- one that bends on the long/verticle axis of a 4'x8' sheet, and the other bends on the short/horizontal axis. Its construction is based on a flexible wood core (unknown type) and exterior laminated layers oriented horizontally if bending horizontally; vertically, if bending vertically.

I bought the horizontally bendable 3/8" ply at $33 per 4'x8' sheet. So as jr1414 described, the front baffle and rear wall will serve as forms to which the very flexible bendable ply will be glued and tacked with pneumatic staples. The ply will take almost whatever shape I give it and will remain solidly in place by being fixed to the MDF front and rear forms. Each side will require two 3/8" sheets with liberal glue for the entire mating surface of the ply sheets, so as to avoid resonant layers or airspaces. Since my side dimensions are 11 3/4" x 40", I can get 8 pieces out of one sheet of ply -- all in all, a pretty cheap way to go.

Keep in mind, this is a big experiment. I've never used this material before, but it should work.

[Owen Bartley]

Mark, very cool design ideas for this project. I'm interested to hear how the bendable ply is to work with and see how it all turns out. I've always really liked the multi-layer laminated idea, but it must cost a fortune, be a pain to do right, and waste a ton of material. Still, the integrated bracing must be incredible.

[JCD]

Ok, two things..

Most importantly, it's been FAR too long with out an update.. specifically with pictures.

Second is regards to the following statement you made:

Then using my handheld router with a Jasper circle jig, a pin placed in the desired radius jig hole and also into the midpoint of each driver location. Mounting plate recesses are routed first. Then, the cutouts are are routed through the baffles. The appropriate router bit for this operation is called a spiral upcut -- best source: MLCS.

Why not a plunge cutting straight bit? Also, after reading the description on MLCS, I got turned around as to which would be better, a downard spiral vs the upward spiral. The upward gets rid of the debris, but the downward seems to be able to plunge better. Again, I got all turned around reading the difference between the two.

JCD

[mrstampe]

JCD wrote:

Ok, two things..

Most importantly, it's been FAR too long with out an update.. specifically with pictures.

I couldn't agree more! I hope to apply the bendable sides to my front and rear face forms sometime this week. Keep an eye out for that.

Second is regards to the following statement you made:

Why not a plunge cutting straight bit? Also, after reading the description on MLCS, I got turned around as to which would be better, a downard spiral vs the upward spiral. The upward gets rid of the debris, but the downward seems to be able to plunge better. Again, I got all turned around reading the difference between the two.

JCD

You can usually accomplish the same thing in woodworking with multiple different tools. In this case, I would recommend the first two of three bit choices:

#1 Spiral Upcut bit -- Best choice for this application for two reasons. As you noted, cut wood particles are ejected out of a dado recess (eg. recess for driver mounting lip) to avoid clogging . Also, it's designed to shave the wood as it cuts your form rather than cutting/chipping -- this is more important when duplicated hardwood forms from template, but never a bad idea. The finished surface tends to be smoother than when cut with choice #2.

#2 Plunge cutting straight bit -- Not a bad second choice if you're working with MDF or softer woods. This one is a rare bird, though. Most straight bits do not have the extra cutters on their ends to plunge. (MLCS comes through again) A standard straight bit will NOT work. The negatives are that it cuts/chips rather than shaves, and it does not direct debris out of the way.

#3 Spiral Downcut bit -- While it may be easier to control plunge speed through hardwood with the downcut (b/c the cutting edge opposes your downward plunge force, instead of self-feeding like the upcut), it can get choked on all the shavings that that are directing into your plunge hole. Okay for shallow routing, but not for deep plunging.

Hope that helps.

[JCD]

mrstampe wrote:

#1 Spiral Upcut bit -- Best choice for this application for two reasons. As you noted, cut wood particles are ejected out of a dado recess (eg. recess for driver mounting lip) to avoid clogging . Also, it's designed to shave the wood as it cuts your form rather than cutting/chipping -- this is more important when duplicated hardwood forms from template, but never a bad idea. The finished surface tends to be smoother than when cut with choice #2.

#2 Plunge cutting straight bit -- Not a bad second choice if you're working with MDF or softer woods. This one is a rare bird, though. Most straight bits do not have the extra cutters on their ends to plunge. (MLCS comes through again) A standard straight bit will NOT work. The negatives are that it cuts/chips rather than shaves, and it does not direct debris out of the way.

#3 Spiral Downcut bit -- While it may be easier to control plunge speed through hardwood with the downcut (b/c the cutting edge opposes your downward plunge force, instead of self-feeding like the upcut), it can get choked on all the shavings that that are directing into your plunge hole. Okay for shallow routing, but not for deep plunging.

Hope that helps.

Thanks for the reply and detailed explanations! Before posting my question here, I had e-mailed MLCS with basically the same question. Their response was to use the spiral downcut -- however, based on your response, I don't think they took into account the "lip" required to flush mount the speaker.

I do have a follow up q for you if you have the time -- when you use the spiral upcut, do you have to drill a starter hole to the required depth first? Or can you plunge down adequately with the spiral upcut bit? Also, what size bit do you use?

Oh, and I'm an MDF guy if that changes any of your answers.

Thanks for the info and I can't WAIT to see how your project progresses.

JCD

[mrstampe]

JCD wrote:

I do have a follow up q for you if you have the time -- when you use the spiral upcut, do you have to drill a starter hole to the required depth first? Or can you plunge down adequately with the spiral upcut bit? Also, what size bit do you use?

JCD

I used a 3/8" spiral upcut. No pilot hole is necessary, as this bit mimics a drill bit in its design. It was a compromise in size, having to be small enough to make a full-thickness bore in one pass and using the same bit for two shallow passes of different radii to form the lip. The 1/2" bit might have allowed one pass for the lip, but that's 33% more wood dust to throw around on the full-thickness cuts. Again, there's more than one way to skin this cat (so to speak).

[mrstampe]

Okay, I'm going to jump ahead a few steps, then come back to explain the details later...

I've wired the crossover boards and assembled one of the towers, except one of the wavy sides. I have to keep it open to stuff insulation, install the x-overs and to wire everything up. I've learned a lot from the first one, so the second one will go together much easier. That will be the one I chronicle step-by-step with pics.

Any thoughts or suggestions? Will I need post-assembly access to the x-over compartment? I'm open to any advice.

[Anthony]

Usually, the crossover is mounted in one of the driver sections, or a big cup/plate is used on the back so that the crossover can be pulled out. I've also seen fake bottoms with the crossover there, disguised as a stand -- just flip the speaker over to access it.

Hope this helps some.

Lookin' good!

[Jason Schultz]

I like how you've assembled the xo componants on the board. I will do mine like this next time.

[mrstampe]

DAYTON REFERENCE SERIES DRIVERS ON SALE!!
If you've considered building these Natalie Ps or other Dayton RS speakers, BUY NOW! PartsExpress has the major RS drivers marked 20% off this week only.

RS28A 1 1/4" aluminum tweeter $38 (reg $49)
RS180 7" shielded driver $33 (reg $41)
RS225 8" shielded driver $42 (reg $53)
and more...

[jeremy7]

thanks for the heads up mrstampe