Start a new document any size you want.

Fill the background with a dark grey color.

Select the shape "Ellipse Tool".
Then while holding down the SHIFT key, draw a round shape.

Then apply this Gradient Overlay style.
(Layer » Layer Style » Gradient Overlay)

Now, still using the ellipse shape tool, Hold down SHIFT and create another round shape, this time slightly smaller than and above the previous shape.

Then apply the following layer styles to this shape.

Bevel and Emboss

Gradient Overlay

Inner Shadow

Once again, create another round shape smaller than the previous, and position it in the centre of the previous.

Then apply these layer styles:

Gradient Overlay

From the shape's tool, select the custom shapes tool:

From that custom shapes, click the shapes drop down:

And select the Circle Thin Frame shape from the drop down. This shape should be in your list, it comes with photoshop.

Then draw this shape onto the image, big enough to cover the edges of the previous shape. Set it's color to #2a2a2a

Now add this layer style to this shape.

Bevel and Emboss

Once again, use the shape tool "Ellipse Tool" to create a smaller circle in the middle of the speaker.

Then add the following layer styles.

Inner Shadow

Gradient Overlay

Now apply the follow layer styles to this tiny shape.

Bevel and Emboss

Gradient Overlay

There we have 1 screw/bolt. Now just duplicate this shape (Right click on the layer on the layers pallette, and select Duplicate Layer), and position it around the speakers like I have.

That's it. if your unsure on some of the steps, you can DOWNLOAD MY PSD FILE and have a closer look.