Nautilus Junior - easy full range loudspeakers

I’m talking about these:

attachment.php


attachment.php


attachment.php


They were born as an answer to various needs:
• to improve the ugly audio of the flat TV
• to reuse the very good Audax full range speakers that I used in a previous project
• to avoid, if possible, the classical squared shape that the female part of my family doesn’t like that much

As for this last point, as the round shape was already used ( please look at this thread
How to build simple, cheap, high WAF, full range speakers with Ikea woodden bowls )

attachment.php


I got inspiration from:

attachment.php


Everyone knows them, I suppose, but a little bit too ambitious as a target. So, I found something like:

attachment.php


attachment.php


but, again, too complicated. Till I found:

attachment.php


rather simple, but I needed a 3D printer: I don’t have. Anyway, the idea was outlined …

Further information and pics in next posts ( if someone is interested in … ).

Ciao.
Luca – Monza - Italy

Next episode: how to draw the spiral
 

Attachments

  • 1 in impianto.jpg
    1 in impianto.jpg
    119.2 KB · Views: 914
  • 2 fronte sopra.jpg
    2 fronte sopra.jpg
    77.7 KB · Views: 1,033
  • 3 fronte retro.jpg
    3 fronte retro.jpg
    152.7 KB · Views: 958
  • casse in impianto.jpg
    casse in impianto.jpg
    192.5 KB · Views: 938
  • 5 Nautilus.jpg
    5 Nautilus.jpg
    42 KB · Views: 882
  • 6 bichiocciola.jpg
    6 bichiocciola.jpg
    44.8 KB · Views: 886
  • 7 scorpioni.jpg
    7 scorpioni.jpg
    82.6 KB · Views: 864
  • 8 chiocciola seria.jpg
    8 chiocciola seria.jpg
    85.2 KB · Views: 908
Last edited:
How to draw the spiral

We need to draw a spiral on the sides of these speakers.

Basically we have two kinds of spiral ( all the information on the web, of course ):

• logarithmic spiral ( also known as golden or Fibonacci spiral ) that grows in dimensions quite quickly, so you’ll have less coils and a shorter duct

• plain spiral, with constant grow, that allows you to have longer ducts

My choice was the first, as it’s quite easy to draw ( please look here:

La spirale logaritmica

in Italian sorry, but you don’t need to read everything: go to the bottom of the page and look at the drawings. The length of the radius follows the Fibonacci chain: 1, 2, 3, 5, 8, 13, 21, 34, … ).

To draw it, I used sheets with little squares, tied together with tape, then transposed the drawing to the wooden board ( 16 mm MDF ) with carbon paper.

attachment.php


attachment.php


Ciao.

Next episode: cutting the boards.
 

Attachments

  • 9 disegno su legno con carta carbone.jpg
    9 disegno su legno con carta carbone.jpg
    137.7 KB · Views: 796
  • 10 MDF disegnato.jpg
    10 MDF disegnato.jpg
    137.6 KB · Views: 759
Cutting the baords

Nothing particular to say: I used a jigsaw to cut 2 16 mm MDF boards tied together at a time, to be sure that the sides of the same speaker have the same curvature.

attachment.php


attachment.php


Then I dug the curl of the spiral with a chisel and smoothed it with a spherical file.

attachment.php


attachment.php


For the speaker flange, I used 7 mm plywood. 2 boards each speaker, glued togheter: the first with a larger circular hole to contain the driver, the second with a smaller hole to support the driver with 4 screws.

attachment.php


Ciao.
Next episode: bending the wood ( a flop … )
 

Attachments

  • 11 taglio legno doppio.jpg
    11 taglio legno doppio.jpg
    177.4 KB · Views: 654
  • 12 legno tagliato.jpg
    12 legno tagliato.jpg
    187.4 KB · Views: 637
  • 13 scavo ricciolo.jpg
    13 scavo ricciolo.jpg
    145.6 KB · Views: 638
  • 14 smussatura ricciolo.jpg
    14 smussatura ricciolo.jpg
    123.6 KB · Views: 655
  • 15 taglio cerchio.jpg
    15 taglio cerchio.jpg
    161 KB · Views: 639
How do you decide the volume of the spiral for a particular driver? And then how do you measure the volume of the enclosure?

I'd like to try something with a bit of a challenge and this has always intrigued me.

I have seen decoration for the Autumn season that are similarly shaped: corncucopias. It might be interesting to find driver for some of these.

Thanks,
Mike
 
Last edited:
Founder of XSA-Labs
Joined 2012
Paid Member
It’s a sealed rear chamber designed to absorb the back wave. So design as if making a sealed box driver. There is tradeoff for deeper extension vs providing enough acoustic suspension to reduce effects of over excursion. You can model that with sealed box simulator and TS parameters. Or not worry about it too much and use a high pass filter so that a woofer or sub handles the bass. Volume of final spiral can be measured using some dry goods like beans, rice, etc. add until it fills and then pour into known volume container. Or estimate by dimensions and subtract a percentage for the rounded parts.
 
Bending the wood ( a flop … )

I wanted to use wood for the front and rear curved walls.

On the web you can find many ways to bend tables, generally based on steam, water, transversal cuts filled with glue, etc. …

I tried various of them, with not satisfying results: the boards of plywood ( the wet MDF always breaks ), even full wet, tended to crack, because of the strength necessary to bend them to such curvatures, and the curvatures obtained were quite random, never accurate, even with a sort of template.

attachment.php


attachment.php


attachment.php


The transversal cuts filled with glue were not good too: there was always a cut deeper than the others that caused the board to break.

Maybe the only way could have been to put the wet boards between two templates as high as the speakers are wide, with big clamps to tighten: too complicated.

An alternative is to cut the boards in little transversal laths and put them in place one after the other, but the final surface wouldn’t be as smooth as with a single board.
So, which solution ? In the next post.

Ciao.
Next episode: aluminum and foam
 
Hi Xrk.

Yes, I kept the wood 3 days into water before working it.

I didn't know the existence of bendable plywood before now. Maybe it would have been quite useful. The only drawback I can see, after a quick look on the web, is that is sold only in large ( and expensive ) sheets.

Thanks a lot, as usual.

L.
 
Aluminum and foam

Well, pictures are self explaining: thin aluminum sheet ( 0.4 mm ) tied to the vertical walls with glue and nails, kept in the right curvature with tape before connecting the other wall.

Tip: better to drill the holes for the nails before connecting the sheet to the wood, you’ll work more comfortably.

attachment.php


To dampen the sound reflections, I glued foam sheets, 1 cm thick, inside ( thanks Xrk for your projects, they inspired me ).

attachment.php


The internal curl was made with foam, too: small laths tied together with glue and paper tape.

attachment.php


attachment.php


Before closing all with the other wall and driver flange, put the damping material and the cat. 5 cable.

attachment.php


Ciao.

Next episode: filling the holes with stucco.
 

Attachments

  • 18 deformazione lastre con nastro.jpg
    18 deformazione lastre con nastro.jpg
    140.5 KB · Views: 356
  • 19 incollaggio polistirolo.jpg
    19 incollaggio polistirolo.jpg
    150.1 KB · Views: 358
  • 20 prima del fonoassorbente 4.jpg
    20 prima del fonoassorbente 4.jpg
    127 KB · Views: 368
  • 20b pre fonoassorbente 5.jpg
    20b pre fonoassorbente 5.jpg
    157.3 KB · Views: 347
  • 21 fonoassorbente.jpg
    21 fonoassorbente.jpg
    99.8 KB · Views: 357
Filling the holes with stucco

Again nothing particular to say: just use stucco ( or whatever you like ) to fill all the slots that invariably happen when different materials and surfaces are tied together.

Don’t forget to put a generous amount also on the heads of the nails that fasten the aluminum sheets, so they will be hidden and won’t “spring up” in next processings.

attachment.php


attachment.php


Then smooth everything with sandpaper.

In this phase it’s possible to paint the external curls with spray paint or other. It’s not necessary to stay precisely inside the curl: next working will hide inaccuracies.

Ciao.

Next episode: covering with adhesive vinyl sheets.
 

Attachments

  • 22 stucco pre copertura.jpg
    22 stucco pre copertura.jpg
    111.6 KB · Views: 302
  • 23 stucco pre copertura 2.jpg
    23 stucco pre copertura 2.jpg
    120.2 KB · Views: 309
Last edited:
Covering with adhesive vinyl sheets

Why vinyl sheets rather than an ordinary paint ? Because I never got satisfying results by painting wood, MDF specially.

So for those who, like me, have not a great skill in painting wood:

• vinyl sheet provide a great choice of colours and designs. My choice was for cherry tree like, that matched with the furniture of my living room

• you’ll be more comfortable if you cover front and rear first, than the side walls

attachment.php


• the most difficult job is to cover the curved edges, where the vinyl tends to curl up. Here You can cut the edge of the vinyl transversally all along the edge ( please see pic )

attachment.php


or tie the vinyl in small “crests” all along theedge, then cut them with a knife

attachment.php


• as for the driver hole, cutting the vinyl in slices will leave some segments uncovered

attachment.php


attachment.php


cover them with small pieces of vinyl.

attachment.php


• then, uncover the external curls from the vinyl that hide them, taking ita way with a knife

attachment.php


I tell you that it’s difficult to obtain a good result on the first try. If so, don’t be lazy: take away all the vinyl and restart again: you’ll get more satisfaction.

Al last, you can solder the cat. 5 wire to the driver: I’m used to connect the 4 white cables to the – ( black ) pin, and the 4 coloured ones to the + ( red ) pin.

attachment.php


Ciao.
Next episode: the basement.
 

Attachments

  • 24 fianco pre copertura 2.jpg
    24 fianco pre copertura 2.jpg
    123.7 KB · Views: 275
  • 25 spicchi laterali incompleti.jpg
    25 spicchi laterali incompleti.jpg
    115.3 KB · Views: 277
  • 26 creste vinile.jpg
    26 creste vinile.jpg
    127.2 KB · Views: 261
  • 27 foro speaker pre copertura.jpg
    27 foro speaker pre copertura.jpg
    121.9 KB · Views: 269
  • 28 foro speaker a spicchi.jpg
    28 foro speaker a spicchi.jpg
    117.9 KB · Views: 270
  • 29a foro speaker ricoperto.jpg
    29a foro speaker ricoperto.jpg
    67.7 KB · Views: 268
  • 30 cassa senza speaker.jpg
    30 cassa senza speaker.jpg
    123.5 KB · Views: 268
  • 31 cavi e speaker pre saldatura.jpg
    31 cavi e speaker pre saldatura.jpg
    134.4 KB · Views: 264
The basement

I just used a wooden board, a little bit larger than the speaker to improve stability, then drilled the holes for screws, cable, binding posts and support feet. These ones are just ordinary knobs for drawers, tied to the board by double thread screws.

attachment.php


The basement is covered with marble-like vinyl, to give impression of weight and firmness. Covering here is quite simple, as there are not curved surfaces.

attachment.php


The speaker is connected by 4 long screws, 2 each vertical wall, then you can solder the wire to the binding posts ( 4 white cables to -, black, and 4 coloured to +, red ).

attachment.php


Ciao.

Next ( and last ) episode: the protection covers.
 

Attachments

  • 32 base e piedini e viti.jpg
    32 base e piedini e viti.jpg
    91.1 KB · Views: 236
  • 33 base ricoperta sopra.jpg
    33 base ricoperta sopra.jpg
    113.3 KB · Views: 230
  • 34 base cassa dal basso.jpg
    34 base cassa dal basso.jpg
    112.6 KB · Views: 228