Build home-made cells

Do-able, provided you have access to a large milling machine.

First of all, you will find tons of useful information in the file here below (“Loudspeaker and headphone handbook”), in chapter written by Baxandall (3.4).

Note that several procedures are described here, since there were several trials: drill first then apply conductive paint second, or the opposite ? Thus, read the full page and make up your mind.

Home made bass cell
Dust cover is home made as well (wrinkles will disappear after final heating)
Note at bottom the conductive solder-able 3M 1183 tape (wrinkles will disappear after final heating)
Start point for home made bass cell: rigid PVC, 2mm
Plastic primer applied on all surface, external side only
2 layers of carbon paint (not enough !)
Ready for 2 layers of paint + varnish. Soldering area protected by tape
Soldering area + bridge
Paint and varnish applied
Connection area
Start point for home made treble cell: rigid PVC, 2mm
Probe area, opposite to soldering area
Outer side, ready for primer, paint, varnish
Ready for primer, inner side
3 connections holes drilled, enlarged, plastic primer then conductive paint applied
Plastic primer then conductive paint applied
First layer of insulation paint applied, except over the 3 holes plus locations where spacers will be glued
Drilling done. Still lacking: final layer of insulation paint (both sides) + varnish
Outer side painted after drilling
Improved version of drilling for connection area, seen from inside. “-0.1mm” is for compensating thickness of conductive tape
Home made treble cell vs re-built one
Still the same home made vs another rebuilt

Notes/check list:

  • Use rigid PVC 2mm and 0.5mm, “unplasticized”. Although for treble 2mm is a bit too much: see Baxandall
  • Drill at 12500tr/min with quality bits. 1/8inch for holes, 4mm for screws
  • if using mylar film, use annealing (heat under tension), or apply heating after glueing it
  • Each stripe of conductive paint should measure around 30kOhm (use large probes). You can use Kontakt 35 (copper) or 33 (graphite). Several layers are required. If not conductive enough, you can first add a stripe of conductive tape on the outter side and puncture.
  • Let the coating dry enough time to avoid sticking it to the stator

Notes for bass cells:

  • Apply one layer of plastic primer, 2 layers or more of graphit 33, add the conductive tape (link between the 3 bands and connection area), 2 layers of paint (for bumpers), possibly varnish, then drill holes
  • install spacers (2 of them already painted with graphit), drill holes for screws and rivets. Enlarge those for rivets on inner side. Install conductive tape for polarization and rivets
  • For the 2 long external conductive stripes, use standard aluminium tape, and install them first. For all others, use 3M 1183

Notes for treble cells:

  • Positions spacers to mark painting area
  • Drill 3 holes in stators for connections and enlarge down to 1.0mm. You may do the same thing on the other side to check connectivity easily later. Drill a narrow path (depth 0.1mm) to add conductive tape
  • Apply one layer of plastic primer, 2 layers or more of graphit 33, stripes of conductive tape, 1 layer of paint on both sides (except over the 3+3 holes), drill
  • install spacers. Attention: see special chapter on polarisation. Indeed treble cells have a hidden conductive web
  • Enlarge the 2 holes used for polarisation
  • then second layer of paint (on both sides, still except over the 3+3 enlarged holes), then varnish KF 1282 (especially on internal side), install connectors and rivets used for polarisation
  • Alternatively drill holes first then apply various layers of paint: make up your own mind !

Illustration for alternative solution: drill first, apply conductive paint second:

Zoom on stripe of conductive tape applied outside to help reaching overall resistance target
Using here Kontakt 35 (copper). Slightly better than Kontakt 33: no need to add a stripe of conductive paint on the outside. But more expensive: 200ml is what you need for one treble cell

Install rivets for connectors and polarisation:

  • Apply stripes of conductive tape 3M 1183, on both sides
  • Puncture them (a cross with a cutter) then insert rivet from both sides
  • fix rivet and solder it to the tape on the outer side
Conductive tape installed, punctured (inner side)
Conductive tape installed, punctured (outer side)
Rivet installed
Rivet soldered
Seen from inner side once completed

Open questions:

  • paint bass dust cover or not ? All sources say this is cosmetic only. My theory: this adds weight and thus might filter somehow
  • (…)

Treble cell polarisation web

This is a detail I noticed lately. There is a hidden layer of conductive paint below the paint, below the damping paper, on the spacers. Supply is tightly connected to this layer. Diaphragm of bass cells is directly connected to supply. For treble cell, this is indirect, and this is named capacitive charging.

Measuring hidden conductive layer under the paint
With the probes set like this, I measure 2kOhm
yes, there is a hidden conductive layer under the paint, on the spacers
Creation of a polarization web

Then added paper stripes: low value insulation and damping