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Construction Guide 3

Before you can attach the top to your cabinet you must make sure that all the miters and joins are at the same level. I find the belt sander the best tool to do this with.

Next you need to get the top and lay it down on the cabinet. Make sure that all the corners are in alignment and then take a pencil and draw round inside the cabinet. This will give you a marked out piece of wood that looks like the base. Do the same as you did with the base by drilling the clearance holes and making the countersinks on both sides. Put the deeper countersinks on the outside of the top and the shallower ones underneath where the top joins the rest of the cabinet.

Apply glue to all the panels as shown above. Finally the best bit, where you get to put the top on the cab, just align it up and screw it down. Use the same amount of screws and in the same place as you did for the base. Use a damp cloth to wipe away all the excess glue before it dries. Do this for the inside and outside of the cab.

After the cabinet has dried overnight it's time to start finishing it. First use a belt sander to level off any end panels that stick proud. If you have a panel that went really wrong and is over 2 mm proud then you can make it flush by using a router with a trimming bit. Sand with a orbital sander after using a trimming bit.

Next fill in all the screw holes with a two part car body filler. Don't use wood filler as it's too soft and leaves indents after you sand the filled holes. Sand all the holes using a orbital sander and finally by hand using a 200 grit paper.

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Now you are ready to go round the whole cab with your router with a round over bit installed. You don't have to make a big round over, around 6 mm (1/4") is good. Any more than this and you will be hitting the screws. Rounding over gives a very professional finish to a cabinet and is easy to do. If you don't own a router make it the next thing you buy.

You should have noticed in the photo with the router that I even rounded over the edges of the door and the connector hole. The connector hole is made by cutting a 75 mm (3") hole in the center of the door and gluing and screwing a larger square of wood over the hole. The photo above shows how this looks. Then use a 25 mm (1") flat bit, or ideally a forsner bit in a pillar drill to make the hole in the center of the square piece of wood for the speakon. I use the speakons with the big round flange as they give a good seal. Use a silicone sealant before you screw the speakon in place. It's also a good idea to use 6 mm countersunk Allen bolts and tee nuts to hold the door on. Wood screws are ok the first time you screw the door shut, but if you have to undo the door and screw it back down you will find that the screws do not hold.

Staple 100 mm (4") of glass fiber to one side of each wall inside the rear chamber. Don't put stuffing on all the sides of the chamber as it will be too much. It's enough to have it on each opposing side only. There are three bits of glass fiber in the rear chamber of this bandpass cab and that's was about the right amount. As it was a bandpass cabinet I also put two small pieces of glass fiber in the front chamber. Don't put any stuffing in the front chambers of horns or their horn paths. Staple the glass fiber down well, use staples every 80 to 90 mm and staple it down at the center of the piece of fiber as well. You can see in the photo above that the 100 mm's of fiber is quite flat, this is what you are after. You don't want the stuffing to be 100 mm thick inside the chamber. Use standard 100 mm thick R40 fiber glass, the stuff you would normally insulate your loft with.

Another photo of the inside of the rear chamber before the stuffing was added to the side walls. You can see the staples that hold down the center of the glass fiber.

Were nearly there. Last thing to do is to put the door sealant foam around the door frame. Insert the driver and bolt it in using 6 mm Allen bolts and solider the wire to the speakon and connect it to the driver. Use good quality cable of at least 4 mm sq cross sectional area. If you are building bandpass type cabinets then remember to wire the driver out of phase. So put the Positive cable to the black terminal and the negative cable to the red terminal of the driver. For some reason I have found that bandpass cabinets work better when driven with reverse polarity. If you are using JBL drivers then connect the + to the red an the - to the black terminals of the driver. JBL drivers are reverse polarity or positive current to red terminal causes the cone to go inwards and not outwards, which is the other way round to most other drivers.

Sit down with a nice glass of 1966 premium champagne and play lots of bass heavy music. Drive the new cabinet with at least 3000 watts and sit well back. Play until ear drums rupture or neighbors try to stab you.

Get arrested by police for annoying the neighbors within a 3 mile radius and do your time for being a mental bass creator. Have fun.

Please note that the plan for the cabinet shown in this guide will not be put on this site. So please donít email me and ask for the plan. The cabinet is of the bandpass type. The front chamber port is flared, this does not make it a horn, it is just a bandpass cab with a flared front port.


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