Building the XT-8 Line Arrays

One completed enclosure, minus the back panel, ready for finishing

It all starts when the UPS guy delivers three boxes of drivers, which contain 16 Vifa XT18WO09 woofers and 16 Fountek JP2 ribbon tweeters. The drivers alone weigh more than 100#.

When the drivers arrive it's time to go out and buy some mdf. This project requires three 3/4" panels and one 1" panel (for the baffles). It's best to have the lumber yard crosscut them about two inches longer than you will need; mdf is very heavy and this makes them much easier to carry.

Finally it's time to cut up some mdf. The panels for one enclosure are pictured in the background getting a test fit.

A closer view. The long panel inside the enclosure is a brace that runs longitudinally across the full width of the enclosure about 6' behind the drivers. Cutouts will be made behind each woofer.

Marking the cutouts for braces that will be placed between each second woofer. These are not called for in the plans, but braces like this have worked so well in other tall speaker projects that I decided to add them to the XT8 enclosures.

Measure twice, cut once. The cutouts for these woofers need to be precise, so it's best to do some trial cutouts and recesses on a piece of scrap mdf. Here I have done two and set one woofer into the hole - a perfect fit!

The final template with three woofer cutouts and a partial tweeter cutout that will accommodate three tweeters. Everytning fits, so it's on to the real baffles.

Preparing to draw out the woofer center points on one of the 1" mdf baffles.

One of two completed mirror image baffles. Cutting the driver holes and recesses is the most tedious and demanding part of the process, and the messiest by far. If you make a mistake here, often your only option is to get another mdf sheet and start over. Whew! I'm so glad that part is behind me!

The completed braces with a chamfer (45 degree angle) cut into the circumference of each hole to reduce internal reflections. The solid section of each brace will form the back panel for a separate chamber behind the array of eight tweeters. Thesse braces are placed about 6" behind the front baffle with the holes aligned with the drivers.

A completed enclosure, minus the back panel, in clamps.

WIth all the internal braces installed, minus the back panel.

A close up photo which reveals the internal bracing. The vertical brace extends the full width and height of the enclosure and has a hole behind each driver. It's purpose is to form the back panel of a separate tweeter subenclosure (which eliminated the need for air tight tweeter installation) and to brace the deep (14" for sealed version, 18" for ported shown here) side panels. I also added a cut-out horizontal brace, shown through the lower driver hole, between each second woofer.

Back view. The lower part of the enclosure is a separate chamber for the crossover

Same view but with back panel in place and one port inserted for a test fit. A 1/4" mdf panel will cover the crossover access hole.

OOPS! Mid Course Correction - Rick Craig pointed out that it would be better if each two-woofer section, with its own port, were isolated from the others. So here's a view of the interior after the addition of some covers for the openings between the woofer sections.

Attachng the baffle to the other enclosure. Hint: Clamp it near the four corners so that it overlaps the sides all around. Drill the pilot holes for the screws while it's clamped (or it may move while you're drilling). Remove it, apply glue, screw down tightly, wait until dry. Then (yet to be done with this one) you can use your router with a trim bit to trim it flush with the sides for a professional looking fit.

Glued in place with screws around the perimeter and clamps between the woofer and tweetere cutouts. The screws will be removed and the holes filled with wood putty after the glue has set.

Installing the eggcrate foam damping material

A completed enclosure ready for finishing

The finishing begins by filling the screw holes with wood putty. This is an especially important step in the process if the enclosure is to be painted. The putty shrinks while drying and a second application and sanding will be necessary to make the holes completely invisible. Paint, especially if it's dark and/or glossy, is even less forgiving of little mistakes than a woman who has caught her man in bed with her best friend.

The front baffles are painted, so it's time to buy the cherry veneer for the sides. (That red looks good on a small speaker, but after seeing it on these large enclosures I changed my mind and painted them black).

The completed speakers