Darbari part 2: the enclosures

I decided to go for a two-box enclosure design, as shown below. The woofer enclosure is shown below.

I am building a second enclosure for the midrange and tweeter. This one will be placed on top of the woofer. The upper enclosure will look like this:

As you can see, the upper enclosure is narrower than the woofer enclosure, but they have the same depth. I intend to align the front baffles of the two enclosures and center the upper enclosure laterally.

Modelling the woofer in its enclosure gives an interesting picture. The enclosure is about 141 litres. Unibox says that this box, sealed, gives a modeled response something like this:

Modeled response of woofer in its enclosure

We are getting an Fb of 34 Hz, an F3 of 47 Hz, and a Q of 0.54. All in all, a beautiful underdamped enclosure which will not give me the deepest theoretical bass but will give me tight transients with no boominess (save that which will be added by room modes). It is likely that if I get this behaviour after measurements, I may not apply any Linkwitz Transform to the woofer at all.

Internally, the woofer enclosure has the kind of bracing I prefer -- strong 20mm plywood fitted edgeways to the side walls from the inside, every few inches. Also note the three-sheet-thick front baffle. I prefer very solid front baffles, to ensure that there is zero radiation of spurious vibrations from the front. In the Asawari, I have used two-sheet front baffles, and they have been absolutely dead. Here, partly for greater strength to hold the 10" woofer, I have used three sheets.

Since the woofer box is fairly large, it became easy to design an internal bracing structure which would be assembled as a separate sub-assembly, with strong Araldite-based internal joins. This sub-assembly could then be placed inside the box, and the walls could be screwed down to the bracing, together with some more Araldite.

So, the internal bracing for the woofer box is made of the following types of pieces:

The upper enclosure internals look like this:

The front baffle has two sheets of MDF. There is a separate sealed tweeter chamber. I have started this practice from the Asawari II onwards, once I realised that the tweeter's front plate vibrates very slightly in the Asawari Mark I, due to the back wave of the midbass drivers.

As is evident, I am using 45-degree cuts on corners and edges to give the enclosures a slightly less boxy appearance. For the tweeter, the cuts will also serve to reduce edge diffraction.

In the upper enclosure, I am hoping that the back wave from the midrange will be dissipated in the rear of the enclosure and not bounce back to the cone with as much force as in the case of a rectangular box. I intend to fill the midrange enclosure with Dacron fibre only at the two rear corners, i.e. at top and bottom. The rest of the enclosure will be empty.

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