Disclaimer

Features

Materials

Constrution

Performance

Pictures

Disclaimer I know I will get Emails from some of you "audio experts" regarding things that I may have done incorrect or should not have done at all. I am not a speaker building expert; this is only the second time I have built a speaker. I am open to "suggestive" critisim, and welcome it. Please read the full article before sending design comments...I may have mentioned it already :-) All the information here is to the best of my knowledge. Almost all the information here was gathered from reverse engineering. A lot of the details were not recorded during the construction stage, so some figures (like exact port placement) may not be 100% accurate. If a measurement is absolutly critical, and I was not sure of it, it will be noted in the description. Things like exact bracing lenghts cannot be determined beacuse sometimes a 1x1" brace is not exacly 1x1". You have to use some common sense and use my numbers as a reference for this. All MDF cuts are exact, but bracing and finish are not. This is not meant to be the ultimate subwoofer, but a great alternative for those seeking a (although large) subwoofer that reaches down to below 25Hz and costs only a fraction of what one would pay for of similiar quality at retail prices. There are a few design elements that can be improved upon. I only had access to the woodworking tools for a few days, so some things were rushed (like cross bracing). These are all mentioned later. I only had access to Perfect Box 4.5 to use as a design reference. Screen shots of the frequency response etc are from PB4.5. There are certainly more advanced and accurate programs that could have been used. Send me your comments! I'd love to get some feedback on what others think about the Monolith. Email me at [email protected]

Features Swan 305 12" 200 Watt RMS driver (Driver Specs) Paramount Pictures Subwoofer Amplifier (Amp details) Front firing Ported design Dual 3" diameter ports tuned to 23Hz Minus 3dB point at 25Hz (F3) Line and speaker level inputs Active low pass filter (60Hz - 120Hz) Weight: Over 100 Lbs

Materials 4x8' sheet 1" thick medium density fiber board (MDF) 1x1" pine (or hardwood for best results) 20 ft or so Silcone chaulking Yellow Carpenters glue 2 3"x14.85" PVC Pipe or PNR Ports 2-3 good hand fulls of 2" long Dry wall screws 4x8' sheet 1/4" pine...or Hardwood (if you want to finish the outside) Swan 305 Driver from Madisound ParaPix amp from Apex Jr. Molex stake pin connectors (Apex has them) 48VCT Xformer Part #600-0191 (MECI)

Building The Mononith

Before cutting your 4X8' sheet of MDF, be sure to correctly lay out the position of the cuts to ensure you minimize waste and guarantee enough room for all the pieces needed. Cut the Monolith pieces first, and there should be enough scraps for the Parapix box. You will need the following pieces cut as follows:

Monolith Enclosure

Description	Measurment	Quantity
Top/Bottom	20 x 20"	2
Sides	18 x 26"	2
Front/Back	20 x 26"	2

Parapix Housing

Description	Measurment	Quantity
Sides	13 x 3.75"	2
Back	13 x 6.8"	1
Top	4.75 x 6.8"	1

Throughout all of the construction stages, continuilly check to make sure ALL corners are square. This is very important. If they are not, you will end up with a very messy box. Pre-drill all of the holes, counter sink holes to hide the screw heads (not neccesary for Parapix box..can't see it anyway), glue all the edges, assemble and screw in the dry wall screws. For more precission, use clamps to hold pieces together while assembling. Before any piece is screwed, make sure it fits perfectly, tiny difference is hight etc will cause the box to go off square. Wipe away excess glue that is squished out with a damp towel.

The first thing to build is the housing for the Paramount Pictures Subwoofer amplifier. Using the four pieces cut earlier, assemble the housing as depicted by the following CG Image 1. The measurments in the CG Image are to indicate the piece of MDF, not actual box measurements. Actual box measurments are (LxWxH) 6.8 x 4.75 x 14".

Before we start building the Monolith, we must reconize that not all people will want to finish the outside of the enclosure. If you do, you will have to wait before you cut the holes for the ports until after the finish is attached, unless you have access to some very reliable and accurate tools. However, the driver hole should be cut now.

The hole for the SWAN 305 driver is going to be located just below the middle of the Monolith enclosure. Driver placement does not have to be exact, but I used a center position of 11.5" from the bottom of the 20x26" sheet. Find the center width (10") and measure up 11.5" from the bottom. I just traced the hole from the box the driver came in.

With regards to the ports, it would be to hard to perfectly align three holes (2 ports, 1 driver)cut into 2 different layers (MDF and pine finish). Wait until the pine is glued on, then cut the port holes. This is risky, you only have the one chance to do it right. If you can, use a hole saw that is used to cut holes for PVC pipe. I used a jig saw without any trouble. If you are not putting on a finish, you should cut the port and LED holes now. Advance to the ports and LED description. If you are finishing the outside, the ports and LED hole will be cut later.

For the Monolith box, start with one 20 x 20" (top or Bottom) and the 20 x 26" you cut the driver hole in. Lay the 20x20" flat and attach the 20x26" to the 20x20" so that the 20x26" sits on top of the 20x20". Note that the driver hole in the front piece is not directly in the center, but is closer to the botom. Rotate the front so that driver hole is farthest away from the bottom sheet. This is because the bottom is actually going to end up being the top when the Monolith is complete. Later, the ParaPix enclosure will be mounted on the present bottom, and the orientation of the front/back must be that the fronts driver is low, and the backs ParaPix is high. The screws should be spaced about 3 inches apart. Next, Attach a side (18x26") to secure the bottom and the front. View the CG layout for a clearer picture. Attach the other side so that now only the back and top are open.

Now we must secure the Parapix box to the bottom (actually the top). Turn the partially completed Monolith box on its side so that the front is facing up and the exposed back is on the bottom. Slide the 2nd 20x26" (back) into place but do not fasten it. Get in a position so that you are looking down into the box through the opening where the top should be. Clamp the back into place to make sure it does not move (do not screw it!). Now, slide the Parapix box into position (bottom center) so that the Monolith's walls complete the walls of the Parapix box. Hold it in tight and trace its outline with a sharp pencil on all sides. The traced outline on the Monolith's back will be cut out to allow the insertion of the amp, and the outline on the bottom will serve as a guide when securing the Ppix box to the Monolith. Before you cut out the section from the back, remember that you must measure in 1" from the trace, or the hole will be 1" to big on all sides. If it were possible, you would have wanted to trace from inside the Parapix box, not the outside. Do not cut the hole until the Parapix box is attached to the bottom. This way, it is easier to correct any missalignments.View the CG Image 2 of theParapix box attached to the Monolith, with the side removed for visibility. Reproduce to trace on the bottom piece of MDF to its other side (the actual bottom that rests on the floor). With the Partially completed Monolith box still on its side, the back still temporaily in position, and Parapix outline on both sides of the bottom, put the Parapix box in place and have a friend hold it there firmly so you can drill your holes (2 for each of three sides...6 in total) from the very bottom, using the trace as a guide. Glue and screw it in place. Now stand it up and you should have a view from the behind that looks like CG Image 3. Note that there is a 1" space for the back piece of MDF.

The back piece of MDF can now be cut, after it is confirmed that the original trace is still valid. If so, remove the rectangle. Now you can put it in place, drill the holes, counter sink, glue and screw. Don't forget to screw up from the bottom, as well as into the Parapix box. Screwing into the Parapix box serves a double purpose. First, It does the obvious of tightening the seal between the amp box and the back wall, but it also makes the Parapix Box act as a brace for the back wall. A view from the behind and front of my Monolith. Note: due to poor layout in the original cutting of my 4x8' sheet of MDF, I did not have enough MDF for a 2nd 20x26" sheet, so I had to use three separate pieces.

Before the top goes on, the bracing must be put in place. There should be some improvement here upon the present bracing of my Monolith. I will first explain the details of mine, and then how to improve it and why. It is up to you to decide which route to take. When I braced my Monolith, I glued a 1x1" brace along every corner, for the full lenght of the seem. Glue was applied liberally to all sides that made contact to someting (ie another brace or MDF). The problem with this is that there is little to no support for the middle of the walls. It is important to keep the middle's braced to prevent the box from bowing outward (like a ball). This outward expansion will lower the effective output of the Subwoofer. Therefore, I would suggest some sort of "+" brace, in addition to the 1x1" brace, that secures the middle of the walls to the middle of their adjactent walls. View CG Image 4 for an idea of what I mean. You will have to work around the ports, driver and the ParaPix housing. View the CG Image5 of the Pre-bracing Monolith (ports are inserted for the sake of visualization, as with the bottom being removed and the top being secured).

Now, just put the top on and turn it upside down. What we refered to as the bottom was in fact the top. You want the Parapix enclosure near the top so you can access it easily. Also, the ports on the bottom need the open space to ensure proper tunning. View the CG Image 6 of the almost complete Monoltith.

It is now time for the finish. I used 1/4" pine only because it was the least expensive. It would have been preferable to use a hardwood because pine is soft and dings easy. Pine, from what I hear stains better though. The stain/polyeurathane coating will help stiffin and protect the finish. Just as you cut your MDF, you will need to do the same except you must add to all sides enough space so you can mitre the edges (45 degree angle cut). This will hide the edges of the finish. I cannot give you exact measurments here because my 1/4" pine was not really 1/4". If it were, it would be just a matter of adding 1/4" to all sides. I did not finish the bottom because it would never be seen. Once the 5 sides are cut, they are ready to be glued to the Monoliths exterior. Special care must be taken when gluing the finish on to make sure that it is attached square. I applied one piece at a time. I first laid down scraps of MDF and then the finish on top (glue side up). I laid the Monolith on the finish so its own weight would help disperse the pressure evenly. Make sure it is aligned right before it settles!!!. If you have lots of clamps, it would be best to use them...perhaps do all the sides at once using scraps of wood and long bar clamps to get pressure on the body of the finish . If you plan to counter sink the driver so that it is level with the outside of the finish (not resting on top), you can either use a router and go around the driver hole after the finish is attached (to make a 1/2" deep or so groove for the driver to drop into), or if you are like me and do not have the right router bit to do this, you will have to settle for making the driver hole in the finish only larger before it is glued on and just have the driver drop a distance of the thickness of the finish (1/4"). Hope that makes sense. So, if you are using a router (the best way) , glue the front on now and cut the driver hole later (in the finish... already cut in MDF) then router. If you do not have a router, take the piece of finish and put it in place (it would be best to have at least one side glued on so that the front has something to help keep it aligned) and clamp it there without glue...remember to use scraps under the clamp feet so you do not ding your finish!. Drill a pilot hole then cut out the driver hole to the same size as the one in the MDF. Remove the piece of finish and drop the driver in. Trace around the driver and then cut this out. Now the driver should slip through the hole. Once the finish is glued on, the driver will drop through the finish and hit the MDF. Here is a picture of my Monolith just before staining. Note the large driver hole in the finish for the driver to rest in. View pre-stain pic.

Now we can cut the port holes for the 3" diameter PVC (you may want to use PNR ports from a mail order store like Crutchfield. or MCM Electronics. Each port has to be 14.85" long. The ports are located below the driver hole at 4.8" from the the bottom (the real bottom now that it is turned upside down...er, right side up) and 5.8" from either side. Note: these measurements are from the post-finish Monolith, so when measuring up 4.8" from the bottom of the front, the front now includes the extra 1" from each top/bottom sheet (the front is now 28" high, not 26"). For those who are not putting a finish on, and advanced here, you must not include the 1" for the bottom sheet because it is not attached yet. Thus, just measure up 3.8" and over 5.55" (5.8"-0.25"...finish) from either side. There is no finish on the bottom, which is why it was not considered when measuring up, as it is when measuring from the sides.

As with the ports, the LED hole should be drilled now if you are not putting a finish on. If you are finishing the outside, drill the hole when you do the ports. The "power on" LED hole is located directly between the ports. I had to extend the LED wire so it would reach from the back to the front. I drilled two holes in the ParaPix housing for the driver and LED wires. I made the holes small enough so they would fit tight in the hole, and then sealed it with hot glue. Here is a pic. The LED has a lip on the bottom that extends around the perimiter of the bulb. I shaved this off to allow the tightest fit in the hole. I forget the exact drill size, but just try a few on a piece of scrap. Once it was in place, I filled the back in with hot glue. Do not glue it in until the finish is stained or the plain MDF is painted etc. It should be the last thing you do before mounting the driver. For those who are not putting a finish on, and advanced to this point, return to the previous section. RETURN

The Monoliths frequency response curve is very flat. It's smooth fall off has a -3dB of 25Hz and a -10dB of 17Hz. Using a sine wave down from 150-20Hz, the Sub would resonate (room acoustics) at around 50 Hz and 30 Hz. Below 30 Hz made stuff in the kitchen rattle and vibrate :-) Remember this curve does not account for a +12dB boost at 33.5Hz that is built into the ParaPix.

Again, this reflects the Monoliths flat response curve. Relatively consistent at 111dB from 35-85 Hz and an appreiciable 108dB at -3dB of 25Hz.

Max SPL of 112dB and max displacement frequency at 20Hz.

Jerry Lynds
Halifax, Nova Scotia
Canada