Mapping out some Speedsters

[technodanvan]

Before getting into this I'd like to put out a huge "thank you" to the community here for helping so many in this hobby. You've been a wealth of knowledge for many and I hope to continue with this for many years to come. I get a lot of satisfaction from both the woodworking and the music itself, and the only thing holding me back from building more is the lack of space in my apartment. After I knock out a few more of these (full Statement-based HT setup, RS225-based monitors, at least two different full-range TLs, and at least one other monitor setup) I hope to get into the design phase myself.

In any case, this isn't my first rodeo but this IS the first time I've really sat down for an extensive planning stage before heading into a project. I have a few questions on a couple things related to Paul C's Speedster design, and I'm looking for input on some of the more aesthetic qualities as well.

Background:I used to listen to a lot of music in college while sitting at my desk. My first DIY speakers were used there as well as my first 'separate' two channel amp (an H/K Citation 16 that I got for a steal...then sold like an idiot *sigh*). Since then I have moved those speakers over to the TV and just use some little Creative speakers for the computer. They work fine for videogames, Youtube, and Hulu, but I have found that I listen to less music as a result. I just can't seem to find the time to sit down at my main system particularly often since I'm usually working on something.

So I started looking around for some monitors that might work well in a near-field sort of environment. I very, very much wanted to try out the Statement monitors. However, one of the criteria I have for this system is it 'may' need to work well in the middle of a room. While I'm not entirely certain of the precise location my new desk will go, I'd like to prepare for the future. After reading up on the Statement Monitors I determined that:

1. They wouldn't be particularly suited for near-field listening
2. They would either be sitting too far away from the back wall (desk in center of room) or too close to it (desk next to wall) for them to be particularly effective
3. They would be really, really big on a desk anyway

So I continued my search. I looked at many large monitors that probably would have sufficed but I found that what i really wanted was something small. While having deep, quality bass is important to me, I can also live with speakers that don't necessarily produce it all themselves. I happen to be in the planning stages of said 'executive desk' and there is a LOT of empty room behind the drawers. Enough so that one or more 8" subwoofers (*cough* probably four of these *cough*) will easily fit.

Despite the fact I'm pretty familiar with Paul's website I didn't actually find the Speedster design until a day or two into my search. They fit my criteria for a number of reasons, with a few special ones to boot:

1. They're about as compact as DIY speakers get
2. The bass extension should suffice even without a subwoofer
3. I get to try out a Fountek ribbon tweeter without the cost of the Statements
4. They should work moderately well in a near-field environment
5. They should work moderately well against a wall or in the center of the room, though obviously with less bass extension depending on the location
6. They also look cool, which is probably most important to anyone else.

So I busted out my wallet and started buying things. I considered the package deal at Meniscus Audio but decided i wanted to try out some more expensive caps, inductors, etc, etc this time around. Given the relatively low parts count the increased cost wasn't too substantial and it made sense at the time, plus I didn't go crazy with the super-elite ultra expensive stuff - this is only a $40 driver after all. Now I'm planning on making both to see what differences I can really hear. I haven't bought the standard components yet but will with my next order from Parts Express.

I should point out that I ended up buying the Fountek NeoCD1.0 at Meniscus anyone as it was sold out everywhere else. Absolutely fantastic service there, and there was free candy in my box! After about 2 seconds of hesitation (didn't my mom tell me to never take candy from a stranger?) I ate it. I'm still here so I guess they're pretty legit.

So anyway - entering the design phase of this thing. I'm going to make another post just so these don't get long...hope nobody minds.

[technodanvan]

Design Phase:

Ah, we're back. Now what my design phase typically consists of is printing whatever drawings are provided and heading north to use the woodshop at Luke AFB (we don't have one at Davis-Monthan *sigh*). Fantastic place, has every tool you'd ever need and the retired MSgt who runs it is an absolutely great guy.

Anyway, the downside of this is that most of the 'planning' actually happens when I'm at the shop. Which basically means I waste a few hours of my day before starting to cut any wood. Now, this is somewhat helpful so i can see everything laid out in front of me, but it has an additional downside of not predicting some obviously preventable problems.

You're probably thinking: "what flippin' problem could you have? The box is about as simple as it gets..."

Well, I can never do anything simple. First off, I wanted to use rabbets all around. Never done that before, but I just wanted to try it out on a project that probably doesn't need the extra strength before moving on to something more complex.

Also, since these may end up being in the middle of the room I want the back to look just as good as the front. Of particular interest to me is the port. I purchased a plastic one from Parts-Express (which is, presumably, the same one in the Meniscus Audio package) and while I'm sure it functions just fine it doesn't really have a great look to it. Additionally, I've never used any of the 'simple' ports and have always made my own with PVC and a roundover bit. Lastly, there was almost no curve on the back end.

I'd like for the port to be something of a feature on the back, a first-draft rough sample can be seen below:

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There have been some changes since then that I am working on today. Basically, the idea is to have the main box constructed on 1/2 Birch plywood with maple veneer, then have cherry accents in some places. The port itself would be PVC but it would be glued into a nice chunk of cherry and bolted in place using chrome socket-head bolts and hurricane nuts. I have considered flaring the internal side as well, though I question how much room I have in there.

I may make a cherry terminal plate as well, not sure on that. If you have any input there by all means let me know!

Ideally, I would simply have cherry surrounding the driver and tweeter, but given the small size of the baffle I don't think I'll be able to do that. I initially planned on having the entire baffle constructed of 3/4" cherry...but I feel like the final look would maybe be a bit much. I would appreciate any thoughts on that as well. I'll stick with the plan for the time being, but since I intend to make the baffle removable it shouldn't be a terribly critical thing to make another if necessary.

The one place I do have serious concerns is with the crossover. It is not difficult to construct but there are serious space constraints:

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The crossover shown contains actual measured components I have on my desk. Initially I had wanted to mount it on a removable back but there really isn't enough room. In the picture above it 'would' fit, but I also intend to line the walls with 1/2" thick matting...which of course will reduce the amount of room I have even further. It is too large to set on the bottom, and the sides really wouldn't have any more room than the back since the port limits how high you can go.

Paul said these could be made slightly taller and the drivers spaced out so they don't overlap, but I want to keep the original dimensions as much as possible. The extra height might give me more room to work with, but I'm not certain it's necessary.

I'm thinking of making this a sort of 'double decker' crossover. I'm visualizing two small 1/4" birch panels around 4" x 4" square and connected around 3" apart with dowel rods. Sort of a cube with crossover parts both inside it and on top of it. It could either rest on the bottom, or I could add some dadoed pieces on the sides that it could just slide into with a stopped on the back and wingnut on the front to keep the thing from moving.

Anyway, I need to get back to Sketchup to see what I can do with this thing. It'll be over-engineered and I probably won't be able to build the dang thing, but I'm going to get it right this time!

[JonMarsh]

I should point out that I ended up buying the Fountek NeoCD1.0 at Meniscus anyone as it was sold out everywhere else. Absolutely fantastic service there, and there was free candy in my box! After about 2 seconds of hesitation (didn't my mom tell me to never take candy from a stranger?) I ate it. I'm still here so I guess they're pretty legit.

Hey, I got some nice caramels in my latest Meniscus order received this week, four more of the Transducer Labs N26c. Also some optional grills to use on the tweeters.

They've been pretty good at getting some of the more obscure things, and I think they're the best source for the Transducer Labs parts in the US- glad you could get the Fountek parts you were looking for from them.

[technodanvan]

Hey, I got some nice caramels in my latest Meniscus order received this week, four more of the Transducer Labs N26c. Also some optional grills to use on the tweeters.

They've been pretty good at getting some of the more obscure things, and I think they're the best source for the Transducer Labs parts in the US- glad you could get the Fountek parts you were looking for from them.

I've gotta say I'm pretty pleased with their selection. They certainly don't carry everything I need but they have a sprinkling of interesting things I just wouldn't think to look for elsewhere. Also, I like that they will unwind inductors to get oddball values - it seems this is a free service but I'll know for sure tomorrow.

No complaints on the free caramels either.

I'll be placing another order shortly for more things I don't really need, kind of excited about the candy. And the guy stuff, of course.

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After doing some more sizing in Sketchup I'm really, really glad I didn't just try to wing these cabinets. Most of the speakers I've built have been floorstanders so space for a crossover hasn't ever really been an issue. The more I'm looking at it the more I think I'll look at resizing the cabinet a bit. As much as I want to maintain the integrity of the original design it just doesn't look like it'll happen.

To add to the issue, creating my own port necessitates common-use PVC. I generally buy the 'black' variant so it looks a bit better (in my own head) when you see it. In this case, the only size I could find had an ID of about 1 9/16". To get the same tuning I'm looking at a length about half an inch longer than originally called for. Not really a huge issue as that would fit, but I have some concerns about the volume. I need to crunch some numbers to be sure, but an empty box (minus port volume) gives me around 0.05 cubic feet of room to work with. I'm betting the drivers and crossover take at least twice that.

So thoughts on how to best increase the volume while maximizing the space for the crossover? I see the two options below:

1. Increase overall depth for the box by 3/4-1". Pros: Would keep the same look as the front, may give me enough room to keep some little pieces of bracing in there with the crossover on the side in the bottom half, behind the woofer. Cons: May look a little goofy being essentially 'square' when viewed from the side.

2. Increase overall height of the box by about an inch, but give it all that height below the driver and keep the current spacing. Pros: I like the look of the 4" driver overlapping the tweeter so I'd kind of like to maintain that look. Additionally (and more importantly) by increasing the height of the driver I can make it clear most components without issue, giving me the entire bottom piece of the cabinet to work with for the crossover. This 'should' be more than enough. I think this is my preferred way, though of course a combination of the two may be doable as well. Cons: Um...it'd be a little taller? If it looked a bit goofy I suppose could always space the driver down by half an inch to 'hide' the extra height, but that would somewhat defeat the purpose of doing this in the first place.

However, I have another question to go along with those above: I recently reread a few guides on inductor placement. Everything that I have read seems reasonable and doable, but I didn't really see any warning about how an inductor may be affected by the magnetic field of an unshielded driver. In large boxes this obviously shouldn't be an issue, but in a confined space such as this I could have one or two within 2-3 inches of the driver if I don't plan around it. The field itself should be pointed in the same direction the driver is facing (if I remember basic physics correctly... *sigh* ops: ) so should I avoid that orientation with an inductor?

Or should I just not sweat about the small things, build the damn speakers and enjoy listening to some tunes already?

[technodanvan]

Well I ended up increasing the height by an inch but maintaining the original spacing. I also remodeled the box in WinISD and decided to go with two 1" ports ~4.5" long in place of the original. Since they are slightly smaller than my original plan I can put them a bit higher, thus freeing up a little more room in the lower half of the cabinet. This coupled with increasing the width and depth slightly should give ample (ish) room for my crossover to fit.

I have no idea how to round off edges of circles in Sketchup, but the ports will have a 1/2" roundover on both ends, assuming I build these things in the right order.

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Some will probably say I have far too many ribs in there and I absolutely agree given the relatively small size of the driver. I'm including them mostly to test my own ability in measuring thrice and making everything fit together for future projects. The increased size of the cabinet makes up for the lost space. That said, it is supposed to be a helluva 4" driver.

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The back of the speaker and the front baffle with be 3/4" thick instead of 1/2". On the back, this is solely due to creating my own ports. I wanted to have enough room to have a nice roundover back there, especially since the ports are small. For the front, I just feel more comfortable having a thick baffle, regardless of the speaker size. I have not decided if it will be permanent or removable.

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I like the idea of a removable baffle, but to me it defeats the point of having a strong, well-built speaker as there is no way that 4-8 bolts will give the same box integrity of one that is completely glued together. There are benefits of having the baffle removable of course, I just haven't decided.

[technodanvan]

Small update...design is still in flux as I flip-flop as much as any politician does, but I've cut some wood at least!

I decided that instead of a 2 channel computer system I will go with a full 5 channels. The Emotiva UPA-500 caught my eye last week and I already own a UMC-1 that I won't need once the XMC-1 debuts so it sort of makes sense. Of course now I have two monoblocks and a DAC I don't know what to do with...perhaps the beginnings of a music room? It's too big to be a bedroom thing, I think.

So anyway, I'm in the process of making 4 Speedsters now...and am considering either doing a 5th or trying my hand at modifying the design for a horizontal center channel. I bought enough drivers to do either so I guess we'll see, there's no real hurry since the Fountek is still sold out everywhere.

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All sides are 1/2" Baltic Birch, baffle and internal bracing is 3/4" BB. I would have gone for thinner stuff but I had a chunk of 3/4" that was too curved for any large pieces but is useable for this stuff, so whatever. I'm considering going a bit thicker on the baffle in order to gain a little bit of room for the crossovers inside...we'll see what a mockup looks like in a couple weeks.

Anyway, still moving in the right direction on this I think. Even with the planning done in Sketchup I managed to cut a bunch of pieces at the wrong width, but it will work out anyway since I initially widened them for my design. I'm not pleased that it happened but given how long it has been since I've actually cut anything it was certainly bound to. I will work with it.

I am now in the process of sticking some foam on all of the inside surfaces so I don't have to do it after construction. After that...well I guess I'll need to get back to the shop, because cutting these pieces is going to be interesting. I'll probably omit the crossover supports and glue them on separately in order to save myself some pain.

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I think the port piece will actually be harder, I'll show it here if/when I can get it modeled in Sketchup - it's similar to that shown in the second post though. Pretty sure I'm going to lose a finger to a router when making them.

[technodanvan]

On a TOTALLY unrelated note...what kind of wood do you guys think would go with a nice candy apple red finish and chrome hardware? This picture on Paul's site (along with the name of the speakers) has directed my finished look.

I'm thinking a light wood - would maple look good?

Anyway, the port end will be made out of such a wood, and I'm thinking of either veneering the front or doing some sort of laminated hardwood baffle of the same stuff.

Thoughts?

[technodanvan]

Making slight progress on the skeleton for the design, I'm hoping to make real progress in the next week.

The box is pretty much holding itself together at this point, no gluing has been done yet. I need to be careful in the order I do things otherwise the port won't go in as it's sort of part of the structure.

You can sort of see the grooves I cut for a (hopefully) removable crossover board. Obviously I elected to do something simpler than what I did in Sketchup...for practical reasons, as well as safety ones.

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