Trouble Reading Blueprints For Fostex Recommended Enclosure

[kelticwizard]

Here are the blueprints for the recommended enclosure for the Fostex FE207E. Below is the Side View.

The prints specify that 21mm building material was involved. If you notice, the top specs say 320mm for outside front-to-back measurements, 313mm for outside front-to-back minus some small piece. The bottom measures 250mm from inside the front baffle to the outside of the back wall.

Inother words, the only difference between the 313mm top measurement and the 250mm bottom measurement should be one thickness of building material-which is 21 inches. Yet the thickness is in fact three times that, even though the plans do not seem to reflect three thicknesses of building material for the baffle.

Please help. I am trying to calculate the internal volume of the double chamber bass reflex, so that I can understand the double chamber principle better and apply it to other speakers.

[herm]

Wizard,

It looks like the 250mm dimension should not go to the
back, it should go to the (2) x 21 line.

Make the internal dimension 250. Add 21 for the front
and (2) times 21 for the back and you get the 313mm.
Add that 7 mm trim and you get 320, right?

At least t looks that way to me! But I've been drinking..

herm

[kelticwizard]

You might have been drinking, but what you are saying is probably the case.

Usually dimensions are either outside dimensions or inside dimensions. Up to now, I have not seen a dimension given which goes from the inside of the baffle to the outside of the back.

The numbers would work if you assume that is the error.

You're probably correct, but I think some of our members have surely built this Fostex recommended enclosure and I would like them to confirm.

Incidentally, I am not really building this enclosure. It is just that I am having difficulty getting anything like a smooth response from any of the sims I do for that style of double chamber reflex, so I am examining a successful one and then trying to scale it to other woofers.