Effect from front baffle material?

[roddyama]

Forgive my poor electrics skills, but what does the Q mean? My elecronics learning book says "A quality factor describing how closely a practical coil or capacitor approaches the characteristics of an ideal component." Umn, different things, right?

Notch filters I know though. I work with them every day

The "Q" is just a number that allow us to quantify our discussion about a filter, whether it be an electrical or mechanical filter. The higher the Q, the narrower the band of frequencies it will affect, and the greater the effect (in magnitude) at the affected frequencies.

That was, and still is, the idea. And to cure the problems involved with that, you clamp the plate tightly to the baffle and add absorbing materials in between I take it?

You will want to allow the damping of the base material to damp the metal as well. To do this you will have to "bond" the metal to the base material as intimately as possible. If you use glue and screws (prefered), the glue, IMO, should cover the entire surface and be of a type that dries hard (like epoxy). Soft setting glue (like silicon) will allow the metal to vibrate.

 

[Oscar]

You will want to allow the damping of the base material to damp the metal as well. To do this you will have to "bond" the metal to the base material as intimately as possible. If you use glue and screws (prefered), the glue, IMO, should cover the entire surface and be of a type that dries hard (like epoxy). Soft setting glue (like silicon) will allow the metal to vibrate.

So your advice is to not put any damping material between the aluminum sheet and the baffle? Are there any purple people around who want to argue with that statement?

 

[purplepeople]

You will want to allow the damping of the base material to damp the metal as well. To do this you will have to "bond" the metal to the base material as intimately as possible. If you use glue and screws (prefered), the glue, IMO, should cover the entire surface and be of a type that dries hard (like epoxy). Soft setting glue (like silicon) will allow the metal to vibrate.

So your advice is to not put any damping material between the aluminum sheet and the baffle? Are there any purple people around who want to argue with that statement?

Hi all,

Been migrained for the last 2 days. Can you say The Sound of Silence!

Material is funny stuff, so to speak. (Couldn't help it - don't tell the mods!)

I believe the general consensus is that speaker cabinets are supposed to be as non-resonant as we can make them - a kind of anechoic chamber.

We typically do this by building them as rigid as possible so as to prevent them from reacting to the pressures created by the drivers, then stuffing them with various fibres to prevent internal reflections due to the rigidity and finally, removing outside corners with all sorts of dangerous rotary tools to minimize diffraction of pressure waves that do make it out of the box.

If you epoxy a sheet of metal to the baffle, even one as relatively dead as aluminum, you can only make the whole assembly stronger and thus more rigid. My thinking is that since this will prevent more wall flex, there will be even less motion reaching the outside surface to be emanated by the cabinet. If you do this, you should think about adding more stuffing to deal with the extra energy in the waves reflected internally.

If you use a damping material, like silicone or neoprene, to some extent you have de-coupled the mechanics of the MDF from the aluminum. There will be some transfer of energy but the elastomeric effects of the soft layer will damp what little is trying to get through.

The reason I don't go for more rigid is that, in general, MDF is plenty for the purpose and any extra added by the aluminum needs to be checked by adding more stuffing. The soft approach is less likely to add "effects" and will still serve the cosmetic purpose. Think of it like a shock absorber removing the energy of the waves.

Of course, I haven't dealt with return reflections from the walls back to the baffle front and there can be some effects there, but in general, the energy that returns is quite small by comparison and is delayed by at least 10ms so we often don't blur these with the original sounds.

ensen.