Natalie P towers, with a twist

[mrstampe]

After a lot of reading and advice from fellow Shacksters, I’ve decided to start out my 5.1 DIY surround with a set of Natalie P floor standing left and right channels. Eventually, these may move to the rear if I decide to build Dayton TMWWs for L/R and a Dayton WTMW center. Also, an SDX15 sub is in the works.

I plan to build the ported 50L version of the Nat Ps, but I’d like to put a twist on the design… or maybe a bend. I’m reasonably experienced in woodworking, though this would be my first try at panel bending. This can be accomplished by form pressing thin laminates into thicker panels, by saw-scoring MDF or Baltic Birch, by stacking “polylam” walls, or buying manufactured bendable ply. I'm not married to these plans, so I am open to creative ideas other than the standard rectangle.


See a few sketchup ideas at the end.


Bending techniques…

form bending


scored


bendable ply


translam




Questions:

1) The Swerve preserves the intended Nat P baffle dimensions, but the Vibe and the Wave are instead widen to 10” on average with curved edges. Will this affect the sonic qualities of the speaker?
2) Does anyone have experience with these bending techniques? Any advice?
3) Some building the 50L towers seem to prefer a higher tune (6” long, 3” diameter port = ? tune) to the designers recommendation of an 11” long, 3” diameter port for a 28Hz tune. Any thoughts on that?
4) Which design do you prefer?

[BoomieMCT]

Keep us posted on this. I love curved cabinets! I think one of the pictures you posted was cut in layers and glued, not bend wood.

As far as the baffles - making wider baffles will lower the point where baffle loss begins and may affect your crossover. This is not too hard to compensate for in the crossover with a little patience.

Also, I think the "wave" is the best design - but they all look great!

[ktaillon]

I like the wave the best also! I've been thinking about curved sides also, I was planning on using multiple thin (1/4) pieces of plywood.

I also through together a rounded back speaker..



Here's a different shape speaker, I just started work on these.


Or here is one that I haven't built yet(the wife thing)



You can see other pics at the link below...

[Anthony]

Cool designs. Keep us posted. (sorry I have nothing else to offer in terms of insight here )

[mlwebb]

re tuning, I just finished a pair with JonM's original crossovers (otherwise same speaker as the Nat P's, also 50 l towers, and I started with 3" precision ports with a 7" length (plus flare allowance), which according to winISD is a tuning of 34hz (not incl room) and they sound great. I am going to try a little shorter, 6-6.5 and see if it brings the 40-50 hz spl up a little.

[mrstampe]

mlwebb wrote:

re tuning, I just finished a pair with JonM's original crossovers (otherwise same speaker as the Nat P's, also 50 l towers, and I started with 3" precision ports with a 7" length (plus flare allowance), which according to winISD is a tuning of 34hz (not incl room) and they sound great. I am going to try a little shorter, 6-6.5 and see if it brings the 40-50 hz spl up a little.

Hey Michael, welcome to the Shack! You'll find some great discussions here with impressively knowledgible people. Regarding your Natalie P towers, we'd love to see them. You could either post a quick photo in this thread, or even better, you could start a new thread describing your goals, building process, several pics of its progression and your impressions of the outcome. It would also be interesting to get your evaluation of how the Nat P changes by increasing the tune (shortening the port). Thanks for joining my build discussion, and I'll look forward to seeing you around the Shack!

[Rodny Alvarez]

I like the wave,

The bendable plywood would be the easiest to build, they have two types of bendable, so make sure you get the right one (birch bendable plywood)

[bonehead848]

Wave FTW! The bendable ply would be the easiest but these high level mtm builds really can throw out a lot of bass. Is braced bendable ply really strong enough?

[mlwebb]

Well, I tried the six vs seven inch port, (36hz, vs 34hz box tuning), and listening to a few single tracks (from Acoustic Alchemy to Rolling Stones sympathy for the devil, a couple beatles tunes, a country song (Fred Eaglesmith) and a little Joe Cocker), with sub off, no measurement equip but old ears, and I think I'll stick with the six inch port for a while. It seems to give a little more umph to the bass drum, guitar low notes. I think Jon originally tuned the smaller box version to 32-33 hz, so its worth trying a few port lengths to see what works with your room, and whether a sub will be used. They go very loud comfortably, not that I really crank them often, and sound very good. Sure you will be happy with yours

Here's a picture of mine, design(pdf) and finished(jpg)
http://www.mlwebb.com/pdf/mtm2f.pdf



I consider myself a pretty experienced woodworker (new to speakerbuilding), and as for curves, the stack laminating looks bulletproof, but an awful lot of work, absent a cnc. My vote would go for making your braces the permanent form for laminating two or three layers of bending ply, with titebond III, a narrow crown air stapler, and a paint roller for gluing the laminations. And watch how tight of radius your trying to bend, I've had my share of glue up madness, when the wood won't behave, the glue is drying, the clamps are all wrong somehow....

For curves, I like to draw them in a vector illustration program, and print them out fullsize for templates, not just for construction ease, but it is easier to get a curve that will bend naturally.

I will be interested in watching your progress.

[mrstampe]

Hey michael, that's a great looking speaker!

I think I'm leaning toward the Nat P Wave and possibly done in verticle polylam layout. In that case, the finish would be polyurethane over BB verticle layers on the wavy sides and a nice complementary veneer on the baffle. I just wonder if all of those verticle wavy lines would accentuate the curves or be too distracting? If I'm not going to see the polylam layers, I may opt for one of the other methods.

Rough dimensions would be as follows: H40" x W10" x D12", curve wavelength 20" and amplitude 1/2" --> If the sidewall were a soundwave, that corresponds to a audio frequency of 675Hz! Also an internal volume of 56L before driver, bracing and port subtraction.

Also, a higher tune or even a sealed enclosure for the mains may be easier to mate with that SDX15 sub in the planning stages. Any suggestions as to how best to tune and cross mains to the sub?

Thanks for all of the advice!

[jeremy7]

great thread. I also vote for the wave. Ive never built any curved speakers, but have been putting a lot of thought into it lately. Im curious if the curved sides on the inside will also help with internal standing waves.

[mrstampe]

Insulating the cabinet should aleviate most standing waves, but if any are left, the continuously waving sidewalls are still "in phase" with each other and technically still parallel. The front-to-rear standing waves will likely still be the most prominent, if any.

[Geoff St. Germain]

As far as building techniques for curved cabinets, here are my thoughts. I've done what is basically form bending and built up the sides using 1/8" MDF to 3/4" total thickness. This technique is a lot of work, but not as much as the translam technique. Translam is good is you don't mind all the work and all of the waste. You could use it to make more complex curves more easily, though I don't know how well it would work for this project. Scoring is an interesting technique. I've tried it and will be using it on the towers I'll be building in the spring. Issues with the technique are that there is a risk of the thin areas breaking as well as the material developing more of a series of bends look to it rather than a continuous curve. When I do it, I'll probably do a 5/8" scoring and then overlay a piece of 1/8" MDF.

[DRB]

Wow, my Natalies are just run-of-the-mill rectangular solids. I wish I had more skill and patience.

[mrstampe]

I've been out of town for a while, and work/military obligations will keep me busy for the next week or so. After that, the Nat P Wave project will begin. Any additional advice before I start?

[DRB]

I've been out of town for a while, and work/military obligations will keep me busy for the next week or so. After that, the Nat P Wave project will begin. Any additional advice before I start?

Measure twice, cut once?

Good luck. Even though mine don't look great, they sound good to me.

[Sprtex]

Hey Ray,

Could you start a new thread with pics of your Nat P's? A lot of us are no where near the level as Mark and others where carpentry skills are concerned, and we could probably learn a lot from your design and finish. I'd like to see your work if you have time to post it.

Mark, let me know what I can do to help you with your build when you're back from training.

Tony

[DRB]

we could probably learn a lot from your design and finish.

Things to be learned from my Natalie P's:

1)You need proper tools. Power saws are essential. MDF and jig saws are not real friendly.

2)Laminate, like paint, will not hide all flaws under it.

3)Bondo is your friend.

4)Hand sanding sucks. It is not a replacement for 1).

My Nat's are structurally sound and they sound good. But they are lacking in the beauty department. The fact that they are all black makes them look like those slabs in "2001: A Space Odyssey".

[bonehead848]

DRB wrote:

4)Hand sanding sucks. It is not a replacement for 1).

HAHA, I learned the same thing after my first build!

[Exocer]

Very nice! I wish i had gone with the curved sides myself...

[mrstampe]

The Natlie P Wave build begins!!

To summarize the final build plan:
Design: Natalie P MTM
Cabinet: floor standing 50 liter (10" x 12" x 40" exterior)
Waves: wavy sidewalls formed with bendable ply
Port tuning: to be determined
Prefinish: Bondo seams and open grain, sand and seal
Finish: piano black lacquer (if I can figure it out)


Step 1: transfer waves to template
I laid out verticle lines for front baffle and rear wall on 1/4" hardboard as follows: midline left to midline right margins 8 1/2", as well as 1/2" deviation line to left and 0.5" deviation to right for both walls. Then at 5" intervals, I marked out points along the wave at left dev line --> midline --> right dev line --> midline, and so on. Finally, I used an adjustable ship curve tool ($20 at Rockler.com) to trace the curves based on the layout points. (this will all become clearer in the Step 3 picture)




Step 2: cut out template
Since my bandsaw conveniently fried just before this project began, I resorted to my jigsaw -- very slow going and not as accurate, but it gave me a decent rough result. I then sanded to my lines using a drillpress drum-sanding kit ($12 at Rockler.com).




Step 3: transfer template to 3/4" MDF, cut
I applied my template to MDF board with double-sided tape, traced the outline, and cut out by jigsaw. Since I already had a relatively smooth template curve, there was no need for sanding. I just used a bearing-guided flush router bit on a router table. The bearing moves smoothly along the template, while the flush bit duplicates the curve in the MDF baffles.

[DRB]

Having the right tools (and knowing how to use them) is everything. I suggest you continue to document your progress for the edification of others.

[JCD]