Speaker cabinet: what's the right filler for my finish

[LesPaul1]

I'm building a small speaker cabinet for a bass amplifier, and it's made of 12mm softwood ply. I'm going to finish it with Duratex paint, which is a water - based paint for speaker cabinets. Some cracks needs to be filled in and I'm concern this might impair paint adhesion. In the website I found the advice

"MDF and plywood will readily accept DuraTex. Some resin, epoxy, plastic and solvent-based wood fillers will impair adhesion over the filled area. Hint: If you do use plastic/solvented fillers, a thin coat of PVA glue can be brushed over the affected zone, this will help seal any solvents, and prime the surface, significantly improving adhesion in these problem areas"

Can I use the regular Ronseal wood filler (acrylic resin and water)? Even better, can I use wood glue in places as a filler and sand it? I'm just a little confused around plastic, epoxy, solvent, acrylic :?

I heard that a mixture of half water and half wood glue can be used to seal wood before the finish, is it correct?

Thanks!

 

[Droogs]

If you are worried then use Isopon (car filler) and then once sanded to around 400 apply a couple of layers of thin shellac. Once dry it will be completely neutral and will not react to any primer/paint you then put on top of it

hth

 

[DBT85]

I asume Droogs that that stuff is the same as pretty much all the other 2 part hard in under 10 minute fillers? They all seem to smell the same at least :lol:

I've used Tetrion Powerfil on MDF boxing in and on walls for stuff and sanded back and painted it with emulsion and water based gloss just fine. Beautiful finish on it. Tho it's rock hard mind.

LesPaul, may I ask why you opted for 12mm ply for the sub rather than MDF?

 

[Droogs]

pretty much, Isopon is the brand I've used since the 8-'s and is sold in the states and elsewhere as Bondo. If you want to go real old school you can use plaster of Paris as the filler. the main thing is to make sure you use a primer that is appropriate for the final paint you want to put on.

 

[sunnybob]

Ply is a bit "bouncy" for a speaker cabinet. you will need to sound deaden a lot if you want good base.

 

[Eric The Viking]

Ply is a bit "bouncy" for a speaker cabinet. you will need to sound deaden a lot if you want good base.

Rot.

It all depends on the design. I've got a non-ported bass cab here based on a Wilmslow Audio design from the 1970s. Made mostly to their spec, it's 1/2" ply and has a Fane 15" driver, is one-person luggable, and quite practical.

You could shove fibreglass insulation inside if you like as it's cheap (honestly can't remember if I did after all these years), but at those wavelengths it will do very little: an open bottom E string is 32Hz (approx.), which is a wavelength of about 33.5ft. That's way too long to cause standing waves in that context.

Note that the huge horn-loaded cabs popular for stage rigs and PA use are that way mainly to reduce the amplifier power requirements. They are very peaky in frequency response, and even they usually can't manage a 16ft-long labyrinth (which, IIRC, you'd need to get 3dB of output improvement over infinite baffle on the E-string).

Hopefully XY Mosian will pick up on this, as he used to work in loudspeakers - he can probably explain it better than me.

 

[Eric The Viking]

[edit] Of course I'm talking about musical instrument speakers.

If you mean HiFi cabs, all bets are off, as there are any number of ways of mucking about with the bass. That said, again, absorption in the cabinet really doesn't have effect on the extreme bass. It doesn't work at those frequencies.

 

[xy mosian]

I think you have it all covered there Eric.
In the end is the sound acceptable to you? As for finish, well that is for those more experienced than me. Although I have to say that I have seen wood filler fall out of cabinets simply because it was not an adhesive filler.
xy