ZDT 3.5 Curved Cabinet Build

[Mark_1042]

First off, let me start this by sending out a huge thanks to John Krutke for this design and the huge contribution he has made to the diy speaker building community, and to all the great designers on this forum and forum contributors who have helped make this hobby what it is today. Also, another thank you to the forum members (Hdale and oneplustwo) who answered my PM’s and specific questions I have had, this forum has really been great.

With all the curved cab build threads around here lately, I had almost considered not doing a build thread for these, but since I’ve got the pictures I figured why not. Besides, it allows me to actually contribute something to the forum, and I don’t think you can ever have too much information when doing a curved cabinet build. For most of the users here some of the information in this thread is pretty basic, but it is meant to be directed more toward first-time builders (like me). Hopefully it will help any readers who may be looking to do a similar build and run into the some of the same hang-ups. I’m trying to make this as comprehensive as I can so if you all have anything to add along the way, it would be great if you chime in.

I’ll try not to bore you too much with the details, but I’ll start with a little bit of background on how I got here. This journey started sometime last summer, when after years of going without a proper home stereo I decided to go out and see what the electronics stores had to offer. My last system was a 4.0 surround sound system (if that tells you anything about its age) with American Acoustic speakers and dual 12 inch woofers in the fronts – big speakers (or “monkey coffins” as John Krutke calls them ). Certainly a good set of speakers in their day, and really the best that I’ve owned up to this point, but they had outlived their prime long before they were retired.

So, I shopped around and finally decided to buy a pair of Polk RTi A7’s and a matching surround sound system. Needless to say, that was a mistake. I think my old American Acoustic speakers sounded better than those “Hi-Fi” Polks. So I returned the Polks, but the one thing I fell in love over the week that I had them was the curved cabinets. In my opinion, the sound from these speakers was next to horrible, but the cabinets were very impressive.

Anyway, eventually I made up my mind to go the DIY route, and decided that the ZDT 3.5’s would be my first set of speakers. The ZDT 3.5’s met both of my requirements: they were a 3-way speaker (or 3.5 actually) and offered a matching center channel, they were designed by a reputable designer, and although I would prefer my listening space to be a little larger, it can still meet the minimum listening distance of 2 meters as recommended by Zaph. Also, the lobing in this design does not require that the baffles be tilted – this would allow me to do a curved cabinet build without too much complexity.

I’ve got some plans drawn up on Autodesk Inventor that hopefully I’ll be adding to this post at a later date.

[Mark_1042]

So as I mentioned in my first post, this thread will be directed toward beginners so some of the information here is not foreign to the regular forum users.

I'll mostly be covering the assembly steps here and won't be including the steps required for cutting the parts, but will be leaving this post open if I want to add more detail about that later.

And once again, I'm trying to make this as comprehensive as I can so please feel free to "chime in" with any tips or additional details that I have missed.

[Mark_1042]

I’m actually a bit further along than what I’ll be posting here, but starting from the beginning of the assembly steps-

Parts For the Frame (or “Skeleton”):

For all the flat panels I’ll be using ¾” MDF, with a double thick baffle. Pictured below (from left to right) are all the parts for one of the frames: rear panel, inner baffle panel, outer baffle panel, and shelf braces. I numbered the front/rear panels (the ones having the dado cuts) so that the panels which were cut from the same sheet of MDF would be kept together. This ensures that the dado cuts will be in the exact same places along the length of the board; so given that all of the shelf braces are the exact same size and all the dado cuts are square and of the same depth, everything should square up nicely when assembled.

[Mark_1042]

Dry Fitting the Parts:

I cut dados for each of the shelf braces, but the top and bottom panels will be butt joints. I must have messed up the template for the top and bottom panels because they ended being a little too big, and I’ll have to trim a little off to make them fit. Also note that before doing the dry fitting steps shown here, I took all the shelf braces, clamped them together, and sanded the edges to ensure the edge surfaces were nice and flat and that all the shelf braces were the same size. You’ll also want to drill your cable holes at this point and holes for mounting the crossover boards, since it will be more difficult to do after assembly.



One of the things which I found to be important when doing the dry fitting is to make sure the edges of the shelf braces line up with the edges of the front and rear panels. The points where the red arrows are below, where the shelf brace and panel meet, should line up perfectly. This way when you bend the panels over the sides there will be no air gaps and you’ll have nice contact all the way across the glue joint.



I used a circular saw instead of a table saw to cut my panels, so the cuts weren’t the most accurate and the front/rear panels were kind of wide in some spots. To fix them I sanded them back or ran the saw over them again to straighten them out and make sure they lined up correctly with the edges of the shelf braces, as shown above. I also managed to curve the saw in a little bit at the end of one of my cuts and cut into the corner of one of the baffle panels. To fix it I glued a piece of 1/8" hardboard to the edge (pictured below) and re-cut it to straighten it out. I was tempted to just slap a little Bondo on it at first, but the curved side panels will be glued on at this point so there will be a significant amount of stress here, and I certainly don’t want any of the layers to come apart.

(Note that I added a third clamp for the middle section, but left it out for the picture. Alternatively, I could have also used a small piece of plywood as a clamping caul.)

[Mark_1042]

Gluing Up the Frame:

Since I’m using a double thick baffle, I’ll be leaving the outer baffle panel off for now, and will be attaching it after I have done the sides.

[Mark_1042]

Making a Clamping Caul For Attaching the Side Panels:

For my side panels I’m using 6 layers of 1/8” hardboard for a total thickness of 3/4”. The hardboard requires a significant amount of pressure to hold it in position while the glue sets. I’ve seen a few different methods for doing this – in one of the more recent build threads somebody used bags of salt to hold the panels down, but the most common method I’ve seen is using ratchet straps and clamping cauls. For this project I made a custom clamping caul, an idea I got from someone at the PE forum. The wedge-shaped wood strips along the sides act to put more pressure on the edges of the panels when you’re clamping them down.



The wood strips which I used to make the clamping caul were pieces of oak trim which I found in the “for sale” bin at Menards. I ripped them down to make them a little more narrow so they wouldn’t prevent a large portion of the caul from bending. The profile of the trim I used, before and after I cut it down, is shown below. You can use any kind of wedge-shaped trim, but at $1.99 for a six foot length this was the cheapest stuff I could find.



After I ripped it down, I took off the tops of the rounded “humps” with a block plane, flipped it over and glued it to a piece of hardboard which was wide enough to fit over one of the side panels. To find the width which the caul needed to be, I took a piece of string and ran it across the side of the speaker from front to back, then measured its length and added 1/4”.



I glued my wood strips down using epoxy, but I’m pretty sure that was a waste and that you could get by just using some Titebond wood glue. Whatever you decide to use, if the hardboard (or Masonite) you’re using is tempered masonite, its probably best to sand off the shiny surface before gluing anything down.

[Mark_1042]

Prep Work for Sides:

For this build I’m using 1/8” hardboard to do the sides, and it comes in a couple different varieties. The stuff I usually see at Menards has a smooth side and a rough side, but the stuff I’m using here is smooth on both sides and goes by the name “tempered masonite.” Before I did any gluing, I sanded down both sides of the panels to take off the smooth surface and provide a better surface for the glue to adhere to. Pictured below are the side panels (left side=sanded, right side=unsanded). I cut the panels about 3/4” to 1”oversize in both directions so I would have a little bit of overhang when strapping the panels down. I later found this to be a little too much overhang and decided to cut the panels a bit smaller. Also note, since MDF and hardboard contain some nasty chemicals, I recommend wearing a mask when working with it and keeping little kids out of the area.



Material Options:

Some other materials that can be used for the sides are bendable plywood or just normal ply, but I’m not sure if you could get a good bending radius with normal ply (unless you go with 1/8” maybe). I’ve read that the bendable plywood is easier to bend than hardboard so you may be able to get a tighter bend radius, but its more expensive. The bend radius for these speakers is 33" and it was not too difficult making this bend with the hardboard.

Originally I was planning to do this project using all Baltic Birch plywood, but the stuff is pricey and will put a major dent in your bank account. After building my center channel with BB ply, I decided to go with MDF/hardboard for the towers to cut costs. Not only is it cheaper, but apart from the dust it creates I find it to be a little easier to work with. When I was looking at using BB ply, I found some 1/8” sheets at Woodcraft which seemed to be easy to bend and probably could have been used for the sides. Cost wise it would have been much more expensive: for the side panels alone, I think the BB ply would have cost about $160, but with the hardboard it was only about $45 for both speakers.

[Mark_1042]

Checking The Fit of the Side Panels:

Obviously the front and rear panels need to have the edges cut at an angle, so when they are mated with the shelf braces there’s a nice smooth curve to glue the side panels to:





To find the cutting angles I used Autodesk Inventor, but Inventor is a professional drafting program and unless you have access to it at school or work it is expensive to buy – so a lot of builders use Google Sketch-Up instead. Its freeware and I think you can use it to calculate these angles and do the drawings needed. Inventor was available to me and I know how to use it (not so much Google Sketch-Up), so I used Inventor to find the angles.

I saw one build at the PE forum where the builder had made these cuts at too much of an angle and this caused a great deal of difficulty when he was trying to glue the side panels on. With this being my first build, and to avoid any difficulties in this area, I decided to cut the angles just a little bit shallower than what the drawing had called for. So the interior width of the panels where the same as they were in the drawing, but the exterior width was a little bit larger than what was spec’ed in the drawing. This way, if necessary, I could just increase the angle by removing material.

So, to check the accuracy of the angles and see how good the side panels would fit on, I cut a narrow strip of the hardboard and held it around the curve. As you can see in the pictures below, the drawings were correct and I needed to remove a little bit of material on the rear panels to get a steeper angle. By the red arrow, you can see there’s a small gap where the shelf brace meets the rear panel. It might not have been a huge issue, but I didn’t want there to be any waviness or gaps in the glue joint. The angles cut on the front panel look like they will be fine, and should give me the correct baffle width.

Removing the extra material wasn’t difficult; I just drew a line on the outer face of the panel and knocked the edge back to the line with a block plane and some sandpaper, while trying to make sure to keep the edge face flat. I didn’t have to take off much, only 1/32 of an inch IIRC, but it seemed like it made a big difference.

[Mark_1042]

Gluing on the Side Panels:

Its best to do a dry run with your clamps and caul to make sure everything works as planned before adding any glue. I’ve been told that Titebond II has a working time of about 15 minutes but I tend to think it is even less than that – maybe 10 minutes at most. For each panel, before adding any glue I lay out all my straps in position so I can add the glue and clamp it down as quickly as possible. I also found it necessary to use another piece of wood as an additional caul to hold the middle section of the panel down, as you can see in the picture below.



Once you get the process down its really a cinch. After I lay out the straps, spread out the glue, and put the panel and caul on, I start by clamping the front edge of in place with a couple bar clamps, using a second piece of the same trim I used to make the caul along the lower edge, so the clamps have flat (parallel) surfaces to clamp on to. Then just check to make sure you have a slight overhang along all the edges and tighten down the ratchet straps. With Titebond II, I gave each panel about 6 hours to cure (thanks Hdale for the tip) before removing the straps and adding the next panel.

For the first panel, which gets glued only to the frame, the glue joint area is smaller so I decided to use some 60 minute epoxy to attach that panel and then used Titebond II for all the panels after that. I know its probably overkill, but it just seemed to me like there would be a lot of stress on the glue joints of that first layer, and $15 isn’t much for a little peace of mind.

[Mark_1042]

Check to make sure each panel is down tight:

After strapping each panel down, its best to look around the edge of the panel and make sure there aren’t any gaps and that the whole panel is down tight. It sounds obvious but sometimes the gaps can be small and don’t stand out. If you can push down on a part of the panel and it moves you probably need to get it down tighter.

On one of my speakers, when I got to the outer layers I noticed a small gap on one of the ends that I almost let slip by. It turns out that down the entire length of the panel there was a gap. Its difficult to see in this picture but it gives you an idea of how easy it could have been to miss it – it might not be completely obvious looking at it but pushing down on the panel you could clearly see that it was not strapped down tight:



I think the issue that was causing the loose section of panel was the overhang of the other panels below it. I cut the panels slightly larger as I got toward the outer layers, and the extra overhang was pushing against the straps, causing the straps to pull on the edge of the caul at more of an angle rather than straight down (see first picture, below). Pushing another piece of wood in under the straps fixed the problem (second picture):

[Mark_1042]

Trimming Off Excess Material:

After all the panels were on, I trimmed off the overhanging material. This was covered in one of the recent build threads, but the overhang on the front/back edges can be trimmed off using a straight cut bit. I used double sided tape to position a strip of 1”X2” on the front and back panels, and this allowed me to come down on the overhang with a 1/2” straight cut bit. For the extra material on the top/bottom edges, a flush trim bit can be used. I don’t have any picture of these steps, but I’ll try to get some and add them later.

A picture of a speaker with one of the sides done is below. The side is currently only five layers thick – I decided to wait to put the final layer on until after the baffle is attached, this way the sides will be one solid piece and there will be no seams. I’m also leaving the other side open for now because I want to add some damping materials and cut the port holes before closing it up.

[Hank]

Good work and documentation, Mark! Will you be veneering these?

[Mark_1042]

Good work and documentation, Mark! Will you be veneering these?

Thanks Hank. Yep, the veneer will be quartersawn white oak, but I've been trying to match the color to a TV console and have been having some difficulty doing it - so the stain hasn't been picked out yet.

[Hank]

My 1 1/2 cents: I quite using stain years ago - we never got to a good working relationship. I changed to dye - there are several brands and types (mainly either water or alcohol based). I use Solarlux: http://www.woodcraft.com/product/200...gany-pint.aspx
I applies SO much better (for me, at least) than stain. You might see if they have a color close to what you're looking for, then try it at various levels of thinning on some veneer scrap. Just a thought - and you probably already know this.

[Mark_1042]

My 1 1/2 cents: I quite using stain years ago - we never got to a good working relationship. I changed to dye - there are several brands and types (mainly either water or alcohol based). I use Solarlux: http://www.woodcraft.com/product/200...gany-pint.aspx
I applies SO much better (for me, at least) than stain. You might see if they have a color close to what you're looking for, then try it at various levels of thinning on some veneer scrap. Just a thought - and you probably already know this.

No, that's awesome, thanks for the tip. I've actually been thinking of going that route but wasn't sure if I'd get better results. It certainly seems like its worth a shot.

On wood finishing with stain, believe me I'm in the same boat. If stain mixing was similar to paint mixing in any way I think I might have better luck with it. With the amount of work I've put into these speakers, I'm definitley determined to get the finish right.

[oneplustwo]

Looks nice! This will surely be a bar setting build! Much nicer than my hack job. Looking forward to seeing more.

[Hdale85]

A lot of people prefer dyes over stains. You can even just dye the clear coat and apply it without actually dying the wood.

[technodanvan]

Great pictorial! I'm slowly getting to the point of doing this myself, I'll be sure to check in early and often to avoid mistakes.

I'm a bit concerned with sanding the edge of the baffle to match the curve - and to have that same 'bevel' extend the length of the baffle without high and low areas. Did you just do it by hand or did you have some tool to help with that?

[CADman_ks]

... Besides, it allows me to actually contribute something to the forum, and I don’t think you can ever have too much information when doing a curved cabinet build. For most of the users here some of the information in this thread is pretty basic, but it is meant to be directed more toward first-time builders (like me). Hopefully it will help any readers who may be looking to do a similar build and run into the some of the same hang-ups. I’m trying to make this as comprehensive as I can so if you all have anything to add along the way, it would be great if you chime in.

GREAT! documentation BTW! I think that you're right that it never hurts to have TOO much information. Sometimes, even spelling out the painfully obvious to people about how to do something helps someone "figure" something out that they have been struggling with. Keep it coming!

...

On wood finishing with stain, believe me I'm in the same boat. If stain mixing was similar to paint mixing in any way I think I might have better luck with it. With the amount of work I've put into these speakers, I'm definitley determined to get the finish right.

Here's something that just bolsters your first comment about helping others. I personally have had GREAT luck mixing stain, but others haven't. So there's two different camps there. For the people who have struggled with it, it sounds like dye might be a decent option. Also, as someone who has had success with mixing stain, it makes me think that maybe using dye might be a technique that I want to explore at some point as well. Sounds like there could be some benefit there as well.

It never hurts to have more than one technique in the tool box arsenal...

[Mark_1042]

Great pictorial! I'm slowly getting to the point of doing this myself, I'll be sure to check in early and often to avoid mistakes.

I'm a bit concerned with sanding the edge of the baffle to match the curve - and to have that same 'bevel' extend the length of the baffle without high and low areas. Did you just do it by hand or did you have some tool to help with that?

Hey Dan - yeah, I was also a little concerned about using hand tools on the edge of the front/rear panels, but I didn't find it to be too difficult. I just drew a line on the outer face of the panel so I knew where I wanted to end up, and brought it close the line using a block plane (just a cheap Stanley one from Menards).

When I was bringing it close to the line, I held the plane at an angle so it was only taking material off near the outer face. Then when I got it where I wanted it, I flattened the plane out against the end to take the remaining material off the center of the end face. If you look through the slit in the plane by the blade, you can see where it is taking the material off, so that provides a good way to make sure its not removing material where you don't want it to. Then once I got it as close to flat as I could get it I just sanded it the rest of the way.

Its a little tedious, and it seemed easy on the first speaker I did but was a little more difficult on the second. It seemed like a safe way to do it for me, since I didn't really trust the angle setting on my saw. An angle finder is also useful for checking your angles and making sure they're where you want them to be and are both the same.

I was a little intimidated about doing a curved cabinet build myself, but so far the assembly is going better than I had expected. I think the biggest battle is making sure the frame is accurate, and once that is done putting the side panels on is fairly simple. If you decide to do some I'm sure you'll love them, just picking up the one I've got half done, its pretty sweet. Really solid, and a little heavier than I had expected.

[Mark_1042]

GREAT! documentation BTW! I think that you're right that it never hurts to have TOO much information. Sometimes, even spelling out the painfully obvious to people about how to do something helps someone "figure" something out that they have been struggling with. Keep it coming!

Thanks CADman, I wasn't sure if I was going a little over the top with all the detail. :B If I see something laid out in detail, I know it gives me a little more confidence going into it, so hopefully this thread will do that for anyone who is considering doing a similar build.

Here's something that just bolsters your first comment about helping others. I personally have had GREAT luck mixing stain, but others haven't. So there's two different camps there. For the people who have struggled with it, it sounds like dye might be a decent option. Also, as someone who has had success with mixing stain, it makes me think that maybe using dye might be a technique that I want to explore at some point as well. Sounds like there could be some benefit there as well.

It never hurts to have more than one technique in the tool box arsenal...

Right on. At least someone is good with mixing stain. :B Actually, I think I've got a color that I'm willing to go with now, but it was certainly a painful process. But like you say, I'd still like to try using dyes because I've never done it before and I'd like to see what kind of effects they can give you.

[Mark_1042]

Looks nice! This will surely be a bar setting build! Much nicer than my hack job. Looking forward to seeing more.

Thanks, I almost missed your post there. I forgot to mention, I really like your SR71's. It may be a while before I do another build, but I've definitely got my eye on the SR71's for my next project.

A lot of people prefer dyes over stains. You can even just dye the clear coat and apply it without actually dying the wood.

I've been thinking about doing a tinted topcoat, I may be able to get by with one of the stain mixes I've got now though.

I've probably been a little too picky with the color, but I'm trying to avoid what happened with my subwoofer - I thought I had a match but once I stained it and looked at it from a distance, it turned out to off quite a bit.

[Mark_1042]

I started with the second speaker and with the first panel I had some difficulties getting the straps down tight enough, so I used some of the 1 x 2's I had sitting around as some extra cauls. That still didn't get it down tight enough though, so I stuffed some shims in underneath the straps and that eliminated all the gaps I was seeing down the center of the panel.

There's a limit to how tight you can get the straps using just the ratchet mechanism, they were tight to the point where I couldn't get another click out of them, but still not tight enough to hold the panel down without any gaps. Really a stroke of luck that I happened to have a pack of shims. I'm not really sure why this panel was so difficult to tighten down, the shelf braces looked good but maybe they're a little out of line. Whatever the case, the shims really helped.

[Mark_1042]

Great pictorial! I'm slowly getting to the point of doing this myself, I'll be sure to check in early and often to avoid mistakes.

I'm a bit concerned with sanding the edge of the baffle to match the curve - and to have that same 'bevel' extend the length of the baffle without high and low areas. Did you just do it by hand or did you have some tool to help with that?

Hey Dan - yeah, I was also a little concerned about using hand tools on the edge of the front/rear panels, but I didn't find it to be too difficult. I just drew a line on the outer face of the panel so I knew where I wanted to end up, and brought it close the line using a block plane (just a cheap Stanley one from Menards).

When I was bringing it close to the line, I held the plane at an angle so it was only taking material off near the outer face. Then when I got it where I wanted it, I flattened the plane out against the end to take the remaining material off the center of the end face. If you look through the slit in the plane by the blade, you can see where it is taking the material off, so that provides a good way to make sure its not removing material where you don't want it to. Then once I got it as close to flat as I could get it I just sanded it the rest of the way.

Its a little tedious, and it seemed easy on the first speaker I did but was a little more difficult on the second. It seemed like a safe way to do it for me, since I didn't really trust the angle setting on my saw. An angle finder is also useful for checking your angles and making sure they're where you want them to be and are both the same.

I was a little intimidated about doing a curved cabinet build myself, but so far the assembly is going better than I had expected. I think the biggest battle is making sure the frame is accurate, and once that is done putting the side panels on is fairly simple. If you decide to do some I'm sure you'll love them, just picking up the one I've got half done, its pretty sweet. Really solid, and a little heavier than I had expected.

Dan -

I should also add, there's been plenty of people here who seem to have gotten good results just cutting the angles with a saw (I'm sure you've seen the build threads). I was actually able to get pretty good accuracy with my circular saw, and its just a cheap Chicago tools model from Harbor Frieght. From what I can tell, the angles are only off by a few degrees when comparing the setting on the saw to the measurements I get with the angle finder.

I just did it this way because I wanted to avoid taking off too much material and I felt like it gave me a little more control, but YMMV. Perhaps some other people here will be able to offer you better advice.

[Steve Manning]

For setting up angles on my table saw I recently purchased one of these guys http://www.amazon.com/General-Tools-.../dp/B00563TLSI well worth the $24. Lets you set up your blade to 10th's of a degree.

Build is looking good Mark .... I had toyed with building my curved Modula MTM's in a similar fashion, went the slower more painful stacked lam route instead.

[CADman_ks]

For setting up angles on my table saw I recently purchased one of these guys http://www.amazon.com/General-Tools-.../dp/B00563TLSI well worth the $24. Lets you set up your blade to 10th's of a degree.

...

That's a NICE tool, right there, and the price isn't bad at all. I might have to buy one of those myself...

[Mark_1042]

That's a NICE tool, right there, and the price isn't bad at all. I might have to buy one of those myself...

I agree, that's a handy little tool Steve.

Thanks for the compliments on the build, it looks like yours is coming along quite well.

[Mark_1042]

Some updates to post. I didn't get as much done on these over the weekend as I would have liked. I'm hoping I can get the cabs done and ready for veneer by this weekend. If I don't get them done within the next week, it may be a month or two before I can find the time to get back at them. Oh well, I'd rather take my time with them than rush through it and make a mistake. Plus I don't really enjoy it when I feel like I'm in a hurry.

[Mark_1042]

A few odds and ends I had to take care of before beginning to close the speakers up. In the original plan I had two dowels running through the shelf braces and down the entire height of the speakers, but later deemed it to be unnecessary so decided to scrap that idea. To make up for the volume of the dowels I added some panel bracing instead. I didn’t put too much thought or planning into it, I just tried to keep it irregular and asymmetric.

I don’t have the original CAD file, but the internal volume should be within 10 cubic inches of what is called for in the plan on Zaph’s website. If I get around to it I'd like to make a new CAD file, just for grins.

[Mark_1042]

I also routed the holes for the port tubes. I liked lcobur’s method of putting a layer of hardboard on all the outer surfaces, like he did in his Ansonica build, so I decided to do it with my build as well. It should provide a nice flat surface to apply the veneer to when all is said and done. So the hardboard layer shown in the pics below isn’t glued on, I’ll be gluing it on when the other side of the speakers is completed.

Ahhh, I love the look of freshly routed port holes. :B

[Mark_1042]

I also added some Sonic Barrier lightweight vinyl to some of the panels. Eh, to be honest, I'm almost embarassed that I bought this stuff. It doesn’t seem to make any difference in a knock test, if it will actually make an audible difference when the speakers are playing, who knows. I'm thinking this stuff is probably better for auto applications and damping thin metal panels on computers and whatnot. For this application, I'm thinking its probably money which would have been better spent elsewhere.

Personally, I find different damping materials and techniques to be rather interesting, so I’ll be saving some of this stuff to play around with in the future and see what kind of results I can get. I’m thinking it might do well as a constrained layer; but there are probably other, less expensive materials which could be used for that as well.

[Mark_1042]

The Crossovers:

Ah, now for the fun stuff. I put the crossovers on 2 separate boards: one for the tweeter and midrange, the other for the woofers. The lower woofer has an additional iron core inductor (a.k.a. the “sledgehammer”) which I chose to mount in the chamber behind the woofer, so it is not shown here.

[Mark_1042]

The crossover chamber with the crossovers installed and all the wiring done. I also installed the sledgehammer behind the lower woofer.

[CADman_ks]

The Crossovers:

Ah, now for the fun stuff. I put the crossovers on 2 separate boards: one for the tweeter and midrange, the other for the woofers. The lower woofer has an additional iron core inductor (a.k.a. the “sledgehammer”) which I chose to mount in the chamber behind the woofer, so it is not shown here.
...]

Nice lookin' boards!

I look at a LOT of other peoples boards, and I think that I have tended to make mine WAY to small! I pile a lot of stuff in a smaller space! LOL...

I wouldn't how to work with all of that space!!! :T

[Mark_1042]

Nice lookin' boards!

I look at a LOT of other peoples boards, and I think that I have tended to make mine WAY to small! I pile a lot of stuff in a smaller space! LOL...

I wouldn't how to work with all of that space!!! :T

Thanks for the praise CADman. The wiring isn't as neat as I would have liked but I think it all worked out pretty good.

I know what you mean about packing components in, I had to do it with the center channel. I had plenty of space for these crossovers so decided to use it, and it definitely makes things easier when planning the layout. Getting a lot of components into a small space is more of an art. :B

[CADman_ks]

... Getting a lot of components into a small space is more of an art. :B

Art is maybe a relative term.

Maybe more like a pain-in-the-art... :twisted:

[Mark_1042]

Art is maybe a relative term.

Maybe more like a pain-in-the-art... :twisted:

Right, perhaps quotes should have been used... its an "art."

Pain-in-the-art would be my feelings on it, too.

[Mark_1042]

I've got a few more pics of these that I still need to upload. Progress has been slow, I've been doing the sanding and routing outdoors and the weather hasn't been very agreeable lately. One of them is just about finished, though.

[technodanvan]

Any updates Mark? I'm excited to see how these turn out.

[Mark_1042]

Any updates Mark? I'm excited to see how these turn out.

Thanks Dan, I've been slacking on uploading the pictures for these. Both speakers should be ready for veneer by the end of the weekend, pictures of the progress are on their way.

[Mark_1042]

Here's a pic of the damping material I added before closing up the cabs. I get the feeling I'm going to be wishing that I had done this with both speakers, on the other one I only added the damping materials to the lowest chamber since I knew it would be the most difficult spot to get at once the speakers were closed up.

Being a ported design I decided to go with Ultratouch Denim insulation. It fiberglass-free, and gets excellent sound absorption coefficients on Bob Gold's web page. Still some messy stuff though.

[Mark_1042]

The other side of each speaker was built up the same as the first, I ended up using the "shim method" for almost all of the panels I put on. It seemed like using the shims was the only way to ensure that everything was tight enough; it gave me that extra little bit of clamping force after the straps were tightened down as far as the rachets would allow. One of the speakers seems to have a gap between 2 of the layers - one section makes a higher pitched sound when knocking on it compared to knocking on the same spot on the other speaker, but that happened before I started using the shims and I haven't had any problems since. I'm not too worried about the void, it still seems to be structurally sound, and hopefully it won't have a noticable effect on the sound.

After putting 5 layers of harboard on each side I added the (outer) baffle. I already had centerlines marked from when I routed the holes for the drivers, and just marked a centerline on the cabinets to help line them up during clamping. The baffles were initially cut oversized and I cut them down to size once I had the rest of the cabinets built up. After adding the baffles, I'll add the final layer of hardboard to the sides, rear, and top.

[Mark_1042]

A pic of one of the speakers with the baffle on, and a little bit of bondo added to smooth out the top:

[basshunter]

Dimensions

I’m actually a bit further along than what I’ll be posting here, but starting from the beginning of the assembly steps-

Parts For the Frame (or “Skeleton”):

For all the flat panels I’ll be using ¾” MDF, with a double thick baffle. Pictured below (from left to right) are all the parts for one of the frames: rear panel, inner baffle panel, outer baffle panel, and shelf braces. I numbered the front/rear panels (the ones having the dado cuts) so that the panels which were cut from the same sheet of MDF would be kept together. This ensures that the dado cuts will be in the exact same places along the length of the board; so given that all of the shelf braces are the exact same size and all the dado cuts are square and of the same depth, everything should square up nicely when assembled.

I am contemplating a similar build and would like some additional info, if you would share. What are the dimensions of the forms? I think you mentioned somewhere the sides were based on a 33" radius? What are the interior dimensions of the widths of the front and back, and what is the depth?

Thanks

[Mark_1042]

I am contemplating a similar build and would like some additional info, if you would share. What are the dimensions of the forms? I think you mentioned somewhere the sides were based on a 33" radius? What are the interior dimensions of the widths of the front and back, and what is the depth?

Thanks

Sorry I'm a little late getting to this.

Yep, the sides are a 33" radius, and the center of the radius is about 3" (perpendicular distance) back from the front. So the sides actually curve out a little bit before curving back in. The following aren't exact dimensions, but the front panel (the interior one with the dado cuts in it) is about 7.5" wide, and the rear panel interior width is about 5". Overall, the speakers are about 14" deep and 10" wide at their widest point. The interior depth is about a foot. (14" exterior depth, minus 1.5" for the double thick baffle and .75" for the rear panel = 11.75")

If you want some more precise dimensions you can drop me a PM, and I can send you some of the plans, although I modified things slightly along the way. They're some decent sized speakers though, and pretty heavy.