Tidbits on building speakers:

This is a difficult hobby. Many beginners want to "go for it" as I did when I started. We want to start with the final product rather than take the journey and run a couple of test cases. This path can can get hard very quickly. Some people throw a lot of money into components and end up with mediocre results. Expensive components alone do not make great speakers and are often harder to tame then less expensive components. I suggest easing into the hobby with a kit so you have a successful first project. Once you have a reference then buy some components and play with different designs. If you are in this for only one round and want the best right off, then a kit is really the only way to go.

You will also need to train your ears. Start with a reference speaker and take time to compare with better speakers. Learn to listen and know why these reference units sound good. A very good cheap choice is the RC-2. Build one of these and you will be trying to better it for some time. There are plenty of other kits but these will provide a solid direction.

Stay within your skill level. A little stretch is OK but don't over do it. If you do want an original looking design, use modeling software and known good drivers. Or use someone else's design and make the box look different (using the same volume). Most of the good builders have tried many drivers and there is a reason unpopular drivers are unpopular. This is the best site for finding kits and drivers: Loudspeaker Design Selection Guide

Modeling

Don't model for a very low f3 (like 30 Hz) with a small (like 6.5") woofer. Computer modeling programs can create a nice looking alignment for almost any woofer if you push them. But a 6.5" just does not move the air to get below 45Hz respectably. Save your self a lot of energy trying to find lost bass on a project with under sized woofers. A good implementation with an f3 of 55Hz will sound a lot better than a poor implementation with an f3 of 30Hz. If you are using a sub then design a speaker for the range above the sub. There are some great mids out there that naturally roll off at 90Hz. Don't kill yourself trying to get the bottom octaves out of a speaker that does not need it.

Don't obsess over the cabinet. If you do some basic planning and your calculations are right, then the cabinet will turn out OK. If the speaker ends up sounding not right and your cabinet is to plan, then you can look to other problems. Remember your drivers may be 10% out of tolerance so don't kill yourself over 1% cabinet tolerance. Build a good cabinet and move on.

Cabinets

Think thrice, measure twice, cut once. I cannot tell you the number of times I have made a carefully measured cut only to find I did the math wrong. Build jigs and stops to cut all pieces at the same time. It is very hard to go back and get the same size after you have reset a saw. You are not as interested in getting a perfect 9" cut as making sure all the pieces are the same size. If you end up with 9-1/8" it is OK if all the pieces are the same size.

Brace your cabinets well. Take this seriously. A well braced cabinet will take a lot of other work out of the speaker building process. A poorly braced cabinet will add sound and you won't know where it is coming from. Some people use ply for bracing and MDF for the walls. This is OK.

Use ¾ MDF and look for the better quality MDF. Home Depot sells a medium quality MDF that will work if that is all you can find. The better quality MDFs are heavier and don't chip as easily. Once you see the better stuff you will recognize it anywhere.

Keep the tweeter close to the woofer. Also keep the tweeter close to the top of the cabinet. There are a bunch of formulas to calculate this but it all comes down to the closer the better. Some people are overlapping tweeters, tucking them behind the woofer.

If you are making a thin tower, make sure the port has space around it. The port has to end 3 from the back wall and have enough air around it to not hinder air volume to the rest of the cabinet. It is OK to put stuffing in the cabinet but don't interrupt the air going to the port.

Hot glue works really well for holding cabinet damping materials, but it burns your hands a lot.

Before you cut anything, dial in your saws. I did not think this was a big deal and used the markings on the saw guides. My first couple of units took forever to match pieces and finish. I found I had to cut extra pieces and then mix and match to get a fit. Then I took a square and dialed in the saws. What a world of difference. Two hours of dialing in saved 10 hours of box work. Dialing in means making sure your saw blades are square to your saw guides.

Buy a Jasper Jig. It will save you the price of the jig in time and frustration on the first project. Cut the driver recess first, then the hole. Leave 1/32 uncut at the bottom of the hole so the router will not slip as you come around to release the center cutout. Then remove the router and punch out the center. The remainder should be thin enough to scrap away.

Some tricks can really cut down on finish work. I build my boxes gluing the sides and top/bottoms together first. Assemble the box with the bracing inside so the brace acts as an alignment guide. If the bracing holds the box in the correct shape then you cut the sides to be a little beyond the top/bottom. When it is dry, use a flush bit on the router to trim the sides for a perfect match. You can do the same with the front and rear baffle. Cut them oversize and just glue them on with the sides all hanging over about 1/8”-1/4". Then trim the excess off with the flush bit. This eliminates a lot of finish work.

Cutting port holes is not a problem. The trick is to glue the port on the back of the baffle with a pilot hole in the middle of the baffle into the port. After the glue is dry, drill a 1" hole in the middle of the port through the pilot hole. Then take a flush bit and bore out the hole to the size of the tube. The flush bit bearing will run along the inside of the tube. Perfect every time.

I have been cutting the driver holes after I put on the veneer. This makes for a cleaner cut with the right amount of space around the driver. Paint the open wood driver holes black so gaps don't show up.

If you do have finish work, use regular wall spackle. Don't use wood putty or any of that stuff. You are covering the thing with veneer and spackle sands a whole lot easier. Use a sanding sealer to make the spackle bond better. This only works with small repairs. Larger fixes need something that bonds better.

I found the McFeely square head finishing screws work really well on MDF. They are long enough and the small head is easy to cover. Pre drilling is a must but with the small head you don't have to countersink. Test this as some people don't like them. I have recently started using a green deck screw from Sears. #7x2". They also work well.

Be careful. I once took a chunk of finger off while cutting veneer. I was cutting while talking to four kids simultaneously. Lucky I was not using the table saw. My loving daughter looks up and sees blood and says; "do we call you lefty now?" Pay attention to your cutting.

Veneering

Veneering is not that hard. Follow four basic steps: practice gluing, practice cutting, test the stain, test the finish. Leave the mistakes on the test piece. I use paper backed veneer and brush-on contact cement in an open area. There are a million other methods but I have had good luck with this:

Paper backed veneer leaves lines at the edges that are a little darker than the stain. Using NBL (No Black Line) veneer will also help but it will add to the cost. I just finished a pair of speakers using the double wood backed veneer. This stuff is a lot heavier than paper backed, is easy to work with and covers most faults.

Cut veneer oversize and put two coats of contact cement on both pieces

To hide the veneer lines glue: bottom first, then back, sides, front, top. This puts the lines in the least visible spots.

Press the veneer on and roll hard with a J-roller to get good contact.

Remember once the glue surfaces touch, they are stuck forever. So align carefully.

Trim with a wallpaper cutter or veneer saw and finish the edge with sand paper.

Sand with 220 grit for the finish.

Stain according to directions. Test first! Be careful with some stain combinations as they will hide nice grain patterns. Once on it is too late!

I have been using Poly finishes with good results. The trick is to use fresh Poly and put it on as thin as you can. I found an artists sponge (or sea sponge) works well. Two very very very thin coats. Did I mention thin?

Check out Lou C's veneer tutorial.

Crossovers

Once you have the unit assembled, do some serious testing. If it is a kit then worry less about it. A fair number of people install drivers out of phase. You really need some testing software to see what is happening. Don't expect lab level accuracy with your measurement system (and don't be fooled into thinking you have it). But a basic test system will take a lot of pain out of the process.

Break in the drivers. I though this was hogwash until I tested it and realized its true. I plug the drivers into a receiver in the basement and play the radio for a couple of days. You can do this while you build the boxes. Just put a capacitor in series with the tweeter and break it in also. New tweeters whistle esses.

I built some Vifa P13/D27s for my daughter. They sounded pretty good but I knew something was a little off. When I finally measured them the plot showed I had a pretty flat response except the tweeters were out of phase (dope slap now) and there was a blank space in the response. I fixed it and later my daughter came running down the stairs "daddy, my CD player doesn't skip any more!" She could hear it too, it was that obvious but I did not know how to link that sound to which problem. I have yet to do to a speaker building event where someone doesn't show up with a driver out of phase. So it is not just me.

Tuning by ear is really hard. I can tell when a speaker is right and when it is not, but *where* is elusive. Measurement software helps train the ear. I use LspCAD, only $129. If I were to start over, I would buy the this amp and mic. I built my mic and amp from scratch but spent almost the same amount as the MM plus a lot of hours.

If your MLS looks great you are probably doing it wrong. Unless you have a lab, your MLS will have wall ticks, floor ticks, ceiling ticks and all sorts of other noise. Find some papers on the web to learn how to help this. But if you get smooth lines you are probably doing something wrong. I would say good looking MLS plots are a sign of poor measurements. A person who does MLS well will get anomalies but they will know what they are and where.

Wait to glue in the XO until a month after you are sure you are done. And maybe not then. Every speaker I have built to date had the final xo installed only to pull it later for more tweaking. Many builders instill the XO on the outside of the box. I don't like that look. I take a hot glue gun and put four pearls of glue on each corner of the XO on the flat side and let cool. Then drill a small screw pilot hole in the middle. Mount the XO by putting a screw in the hole and screwing the XO to the inside back of the speaker behind the woofer. The screw will pull the XO in at the middle and put pressure on the four glue legs. So you end up with five pressure points holding it in with one screw. If you are worried about the screw effecting the coil, then use a brass screw.

Mark all your wires and mark everything. Mark the wires for positive woofer, tweeter and line in. Remember at some point you will only see one end of the wire, so mark the ends away from the xo. I mark the tweeter positive even if I am using a second order needing a reverse phase tweeter. So I hook the wire marked positive to the tweeter negative.

Don't go nuts over internal speaker wire, the runs are short and won't make a lot of difference. Decent quality 16ga will do fine. Do get a decent quality that won't tarnish under the insulation. Don't use stiff wire as it may twist off the tweeter terminals during installation. I buy a 100' roll of decent wire (like PE 14ga sound king or Carol) and have it in the garage. Having the wire around when you need it is well worth the expense. I used to use 12ga but found I cannot hear the difference and 12ga is just too big for many terminals. 14ga is also softer.

Lately a lot of speaker builders have been using those plastic ties to hold down XO components. I have done this and will never glue again. Cut peg board for the base.

Grills

I make my grills out of ½” MDF from Home Depot. It is cheaper and I don't think we need higher quality for the grill. Order those plastic grill clips from PE or Madisound. I ordered some from ACI and they were tighter than everyone else's but I don't know if that is better. When setting this up make sure you are leaving enough room for the grill clips and the offset tweeter. A really cool thing to do is bury magnets under the veneer and use a pin/hole system as guides with the magnets holding the grill.

Cut the grill MDF to the size of the speakers and round the outer edge with a 3/8 round. Then use the Jasper Jig to cut holes larger than the drivers. Trim the holes to a rectangle with a jigsaw. This is fast and accurate. Then trim the inside with a 45 degree bit. Spray the whole thing black so the wood does not show through the grill cloth. I make a little jig to drill a pilot hole for the grill clips. Then place the grills on the speaker and drill through the pilot hole in to the speaker. Then drill the right size holes in the speaker and grill for the clips.

Use hot glue to fasten the cloth because I am not patient. Some people use contact cement or cloth glue. Cut the cloth oversize and place the grill on top of the cloth. Put some hot glue down and pull the cloth across it. Use a putty knife to firm it down. Then cut off the excess.

I have tried this and it really works well: Use 1/8 inch black vinyl screen spline from a screen door and a saw. Cut a groove around the edge of your frame with a regular kerf saw blade. Use hot glue to fill the ends where the blade ran off the grill. Use a screen roller (about $3 at the hardware store) to press the grill cloth into the slot. cut the excess off with a razor along the inside of the grill. Another advantage to this method is it's a lot easier to remove the cloth if the need arises in the future.

Get a decent sub. Take a look at my Home Theater section on this. Basically a good sub really brings a system together. My experience is that you don't need a lot of watts in a sub. 100 watts is plenty and class D amps are fine for subs. A 12" driver will most likely do the job. Where you really need to focus is on the box and driver. I like the sound of a sealed sub a lot better than many ported I have heard. And sealed sub is a great first project. There are a lot of parts and kit ideas out there. You will get great results with a KG5150 amp and one of these drivers: NHT1259 or PE Titanic, or a number of other good units. Look at the LDSG index for more choices.

Be safe!

Copyright: Peter J Smith 2004, Return to www.helarc.com