# A pair of Hawthorne Audio Sterling Duets. (Open Baffle)



## Bob in St. Louis

Hey, you guys wanna see me build some open baffle speakers?
I'm posting this piggy-back on the build thread on the manufactures site, so I could be called a fanboy shill, but I thought you might like to see some sawdust.

Anyway..... Here goes.....

Tony, A local St. Louis fella had lurked long enough on the HawthorneAudio site that he contacted me about listening to my system. Seem after hearing us (fanboys) chat about it, he was interested in hearing the Sterlings Duets for himself. So of course I brought him into my home and gave him a big tall glass of Hawthorne Audio kool-ade. :heehee:

So here is Tony's build thread.... 

We chose (my favorite) three layer of 3/4" Russian Baltic Birch with a sand fill. Darrel Hawthorne will be building the XO's and shipping them to me later. I'll be building Tony an enclosure to house the XO unit as well as the Keiga plate amps (one for each speaker).
The new twist to this one, is that Tony has chosen to use a veneer, which is new to me. But fortunately, he's trusting enough of my abilities to see what I can come up with. Not sure what type of wood veneer we'll have, that comes later.

Here's what we've got so far, with a couple captions:

Four sheets of 5'x5'x3/4" Russian Baltic Birch:









Rough cuts for the speakers six layers of plywood and the XO/Amp box:
{Note; if it looks like I cut the end of some of those a bit crooked, that angle happens to be exaclty 12.5 degrees. More on that later.}









A photo of the right and left channel middle layers with the markings that will be hollowed out later to accept the sand fill:









The six layers for the two speakers:









The layers stacked:









Here's a bunch of photos from the work today, mainly dealing with the "T-Nuts" and what they are _(I've been asked privately what a t-nuts is, and how it works)._ That being said, the pictures mainly focus on those and what's up with them. There's also noticable progress on the project as a whole though....of course.  

The first pic is a test fit of the two 15" drivers. Of course, now would be a good time to know if they don't fit.
Notice the R1, R2, R3.....The "R" is "Right speaker" and the number is it's position in the layers.
- Number 1 is the face (front) of the speaker.
- Number 2 will be the one that is hollowed out for the sand. Middle.
- Number 3 is the back.










Next up, the t-nuts, their location, how they're pre-drilled and what a t-nut looks like in general.










Here's the t-nut in place, before it's been drawn down into the wood.
In the background are the pieces of wood that will be the front plates that will house the amps and crossovers. This is the piece of wood that will attach to the speaker baffle directly, and hold the two together.
After that, I'll just shut up, stop talking and show a few pictures. They should speak for themselves.













































This one needs a few words.....
The heads of the t-nuts are not flush, and in a situation where the t-nut must "disappear" totally, 100% on both sides, you have to give the layer behind it some room.
The easiest way to do that would be to use a paddle bit so the head of the t-nut has a "void" to go into.
That can be done on the piece of wood the t-nut goes into, or the piece of wood that will be meshing with the t-nut, whichever you prefer.
Personally, I like to leave as much material as possible for the t-nut to attach to. If you cut a bunch of wood out to accomidate the t-nut, you've weakend the material. And if you're using expensive material like this, that would be a shame. 


















Time to blow the saw dust away, get things cleaned up (yes, I actually do vacuum the floor of the workshop before I do this)









In the previous picture, I put layer #2 on top of layer #3, and traced around the openings.......(scroll back up a bit)
These open areas will NOT receive glue during the next step.......(now scroll down)
The zig-zag pencil marks will not get glue.
Also note, that I didn't get too close to the opening of the where the driver will mount to. No glue will (ever) be needed there.









Alright, now we're getting somewhere.
It's glue time, so my priority here was just that, not taking pictures.
Bam









No man has ever died with too many clamps.
Done for the weekend. See you next Saturday. Buh Bye......


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## StereoClarity

We always LOVE to see sawdust!


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## tshifrin

Beautiful workmanship;
Thanks for the write-up, I look forward to the ongoing...

Tom (also in St. Louis)


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## Bob in St. Louis

StereoClarity said:


> We always LOVE to see sawdust!


Thank you! 

Tom, Here there fellow St. Louisian! :wave:
I see you're a new member on "AC" too. You new to AC? Have you seen the St. Louis area on AC?

Bob - 63051


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## tshifrin

Bob, Hi there!
Yeah, I'm new to everywhere related to speaker building, 'cause I'm new to the whole speaker building thing, and very interested in learning this stuff. So thank you for the encouragement you give by your reply, and for the write-up I can learn from.
I admit to being much more interested in the audio stuff than in the woodworking stuff. But speaker design can't be studied without knowledge of the cabinets (or in this case, OB's), so I'm following these threads to learn what I can. I think I'm in way over my head, but I'll keep swimming!
I'm starting with Alden's Speaker Building 201, and the stickys of various forums (Parts Express, Hometheatershack, Audiocircle, etc.) to learn the basics. Your suggestions are welcome; you obviously know what you're doing. 
I don't want to highjack this thread further, but you're welcome to pm me if you have some comments about the basics or how best to learn them. And I'll definitely be following this build!

Tom- 63146


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## Bob in St. Louis

Thanks Tom. No worries about the off topic, it's all good. Ask away!

The St. Louis area guys hang out  >> HERE << to keep an eye on the local events. Sign up in the welcome thread, and make yourself known. We'll get you in the houses for some tunes and such. Before you know it, you'll be making sawdust of your own. :flex:

Bob


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## Owen Bartley

Tom, you might also want to check out the Loudspeaker Design Cookbook. It can be a bit of a bear to read at times , but I learned a lot from it.

Bob, those are looking good. I can't wait to see how the sand fill fits in, and how the veneer turns out!


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## tshifrin

Thanks Owen; I actually started with Dickason's book, but found it assumed I knew more than I do. "201" seems to be a good starting primer for me, and then I'll follow with the LDCookbook.

And thanks Bob, for the link. Let me get a bit more learning under my belt before I jump into the company of you guys. I'll follow the threads, but I'd feel under-water trying to keep up with your conversations in real time. I would like to attend some listening sessions though, so maybe I should just take the plunge...

A rainy day in the Lou, and I wish I owned more tools... a good "book larnin' day.

Tom


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## Bob in St. Louis

Owen, thank you very much for the complement. Funny you mention how'd you'd like to see the sand fill, cause I have some more pictures for ya! 

Tom, Yea, we need to get you to some of the get-togethers. There's usually a dry spell about this time of year due to the holidays. I've not seen you pop into the STL area yet. Might help folks welcome you, if they know about you, ya know? haha

Ok, here we go....
A friend and neighbor of mine that also builds speakers gave me a heads-up about a material that he's proven works better than sand to dampen and absorb the vibrations. Since he's running a business building spekaers, he asked that I not tell what the "secret sauce" happens to be. However gave me permission to show the build pictures with the promise that I plug his companys name "Vapor Audio".
Now I have permission to show pictures of the material. :lol: 

One baffle layed down, cavities up, mounds of "special secret material" in them.









Ran a straight edge across to get everything layed flat. I walk around the baffle with a rubber mallet gently tapping the edges to help settle the material, otherwise after time the speakers vibrations would settle the material to the point where there would be open void.









Wood glue has been troweled on









Clamp time


















After both baffles have been filled, and sealed up, I put one on top of the other and clamp them both over night. If I had enough clamps, I wouldn't have to do it this way.
The notebook paper in between is a "just in case" some glue gets between the two speakers. That would suck. 










And final picture shows the profile after I ran the baffles across the table saw. I did the chamfer on the sides and top, front and back. Not the bottom.


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## Owen Bartley

Hey, lucky me! I've never built anything with a material-filled cavity, but those look sweet. When I saw your chamfers I got confused and thought you must have made a mistake doing the backs as well... then I remembered that these are open baffle and felt stupid.


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## Bob in St. Louis

Owen Bartley said:


> Hey, lucky me! I've never built anything with a material-filled cavity, but those look sweet. When I saw your chamfers I got confused and thought you must have made a mistake doing the backs as well... then I remembered that these are open baffle and felt stupid.


Hey, no worries Owen. I feel that way quite often. :rofl2:
Thank you for the complement!

Bob


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## tshifrin

The secret sand looks like what I get when I try to grill a steak; what with my ADD I'm easily distracted; now I have a use for that!
Okay, I see 2 woofer type holes, but you mention a crossover- are they to play in different ranges?

And again: Beautiful workmanship!

Tom


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## Bob in St. Louis

<mental note to self; Never eat BBQ at Tom's house> :whistling:

The top driver is the 15" Hawthorne Audio Sterling Silver Iris. It's a coaxial, so there's a 1" Radian tweeter screwed into the back of the 15" midwoofer. The crossover ("XO") network only affects the interaction of these two drivers.
The bottom driver will be the 15" Hawthorne Audio "Augie", that's the "bass augmenting" driver. The only XO these drivers see will be what the plate amp actively cuts them off it. There's no passive XO.

Hope that helps Tom.
Bob


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## tshifrin

Invitation: My bbq rocks! But then I usually use a smoker and a dry rub for that; the flavors are awesome.

And Thank you, kind sir, that does help. Those look like very interesting speakers. I've never heard IB speakers; the closest I've heard are my Maggies, and that's different. I'll keep following...

Tom


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## Bob in St. Louis

Oh, see....now you're just pushing my buttons. 
I've got threads dedicated to smoking meat. Yea buddy. :T

"IB" (infinite baffle) is way different than "OB" (open baffle).
The biggest difference between the two, is that IB, the rear wave "goes away". Generally to an attic space or the like. 
OB, the rear wave bounces off the front wall of your room and hits you just milliseconds after the front wave does, thereby giving all that wonderful imaging they do (like Maggies).

Bob


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## tshifrin

"OB, the rear wave bounces off the front wall of your room and hits you just milliseconds after the front wave does, thereby giving all that wonderful imaging they do (like Maggies)."

Yeah, that makes much more sense for a full range speaker. I hit the wrong letter, these aren't IB, they're OB. And helps me understand why you would dress the rear edge of the baffle as well as the front. 
Thanks for this write-up. The whole world, from acoustics to dinner.

Tom


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## Bob in St. Louis

The "Pelin Burl" veneer has arrived. Four near identical sheets.


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## tshifrin

Wow, is that ever handsome! And to think it will look even better with speaker holes cut in...

Tom


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## Bob in St. Louis

Yes indeed Tom!
I can't wait to see a finish on it.

Bob


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## Bob in St. Louis

Ok....about done for the day.
I've built the surrounds that will house the amps and crossovers. I then test fit them on the baffles to make sure everybody is going to end up lining up together with a nice snug fit. 

In their clamps:









The rough surrounds without the clamps. They are about 15" x 17" x 6" tall.









The surround up next to it's new friend, the baffle:









Test fit of the amp in the surround:









And bolted it to the baffle:









Front view:









Rear view:


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## tshifrin

Hey Bob, what kind of amp is that? And I don't see a hole for wires, but I'm assuming the crossover lives in the space next to the amp?
You're obviously very good at woodworking, to "knock out" stuff this pretty!

Tom


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## Bob in St. Louis

Hey Tom!
> HERE'S < a link to the Keiga 300 Watt Plate Amp.

There will be a hole for wires. In fact, I'll be making a chase for the (lower Augie drivers) wires to run in. Too much time and effort into making a chase for the (upper) Sterling wires to run in, and the guy I'm building these for wasn't that worried about it.
Someday, If I ever get around to building myself another pair, the wires will be part of the build from step one.
I hate seeing wires dangling. :foottap:

The 5.5" x 11" crossover will set next to the amp.
Although, in hindsight......I should have made them symmetrical, instead of "identical", if you catch my drift. :whistling:

When you coming over Tom? :T
Bob


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## tshifrin

Wow, I've arrived- an invite from a fellow speaker builder, albeit one much more practiced!
I have out-of-town guests through the weekend, so perhaps the next weekend? A visit would be so nice; I could hear what these sound like.
If it's not breaking forum rules; which dealership are you with? I'm a car amateur; member of the BMW CCA, PCA, Audi CC- I instruct at the club schools at Gateway, and the teen Street Survival program.

Back to the speakers: the plate amp is for the woofers? or the whole side? (I'll have to look more on the Hawthorne site for details; the concept is interesting to me. I'd like to hear yours...)

Have a safe New Year!
Tom


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## Bob in St. Louis

The amp for the single 15" driver, the "Augie" as it's called. Each speaker has one, so there are two amps.

Another amp will drive the top two 15" Sterling Silver Iris coaxial drivers. Those are the ones that will use the crossover that'll be mounted in the base next to the amp. I don't have pics of the crossovers yet.

I'm at the Volvo Saab dealer....(yea....Saab..... :help

I worked at Gateway (half a lifetime ago) before it was redone. We may know some of the same people.
I've also got a boy that just turned 13, so you can imagine my eyebrows raising when I read the Teen Street thing. haha

The weekend after next I may have to work, so that one may not be a good one. 
Bob


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## tshifrin

Perhaps you know Rick Ramsey, across the street at WC BMW? A good buddy!
Mom's Saab is (only occasionally, when I can't handle it) a guest of your shop, although it's been a few years. She has a '95, and all in all, I like it- she can fit her whole condo in the hatch (less the kitchen sink).

I look forward to a visit, whenever is best for you; at the moment, I'm underemployed, er, um, "have a very flexible schedule." I have a bunch more questions, but I'll just save them for a face-to-face.

Best,
Tom


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## Bob in St. Louis

The name sounds familiar, but don't know the man. 
We'll get you in here soon, no worries.

Bob


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## Bob in St. Louis

Not too much done this weekend (one of you know why...... :twisted: :wink: )
But these are plywood braces. The original thought process was to have 1"x1.5" welded rectangular metal tubing (think race car chassis), but when we couldn't find anybody to do it, I thought I'd make a quick plywood mockup version and see what it looks like. So this was mainly for Tony's benefit.


The amp boxes are primed, which is why they're white.


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## tshifrin

Bob, check out Izzyscustomcages.com, he's a local member of the BMW CCA, etc. who does really nice race-car cage fabrication. I'm sure he can make some stands for you. 

Tom


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## Bob in St. Louis

Thanks Tom.
But it looks like the fella is interested enough in what I built, and the stability it provides that he's relaxed a bit on the metal issue.
He made a choice tonight that he wants four Baltic birch braces, much like the photo, but taller.

Money talks. 
Bob


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## daddywoofdawg

Maybe it's the photos, maybe I don't understand what's going on,but won't the amps be in the way of the drivers in the bottom holes?


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## Bob in St. Louis

Yea, it's the photo's. I've measured and made test fits. It's close, but will fit.


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## Bob in St. Louis

Didn't get too much finished this weekend. Today was about all I had to get much done, and one of "those" audio guys came over. 
Of course we had to drink, listen, chat, etc..etc..etc...ha ha

So....
With regard to the bases.....
I got some sanding finished. Another coat of primer, some more sanding, a bit of spot putty, sanding, and another coat of primer and more sanding......

Also, there's been a few emails and PM's about the clearance between the driver magnet and the amp, so I thought I'd shoot a (fuzzy) picture.
That's about one honest inch between the magnet and the heat sinks of the amp.

That's about the best I can do with regard to progress for the weekend.
My son's 13th Birthday party is tomorrow, so no sawdust will be flying until next weekend.

Cheers.


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## daddywoofdawg

does heat from the amp affect driver preformace?seems like itwould get hot that close.I don't know, I'm a noob.


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## tshifrin

I don't want to put words in Bob's mouth, but daddywoofdawg, there are 2 big points to remember re: your concern about heat... keep in mind that if the amp is working hard enough to get warm, that the voice coil will be even warmer simply from current flow, so it's built to handle the heat, and that the movement of the cone will provide some air moving around the amp fins--- all in all, I think it balances out, temp wise.

Bob, another weekend approaches, and the weather says inside work is appropriate, so keep on keeping on...
These are really beautiful! I'd love to have a listen.

Tom


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## daddywoofdawg

oK,I have learn something, thank you for teaching.


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## Bob in St. Louis

Well....I suppose it's time to pull back the curtain, just a bit...... 
This is the back of the first baffle. Step one of many in the veneering process. The chamfers take quite a bit of time to do, a lot of steps involved for each angle. 
We've done the back, and first 45 degree angles on the sides. The "ends" and "tops" did not receive glue.

On this particular baffle, I've done the trimming, rough sanding, and quick wipe down to remove the dust and shine things up a bit.
This weekend (and probably next) will consist of veneering each and every individual angle, one at a time, with trimming and sanding in between.

So ..... here are my teaser photos, until (most likely) next weekend.
I gave the Pelin Burl a quick, moist wipe down for the pictures.


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## Bob in St. Louis

Tom,
Sounds like you've got things covered. haha
Well said on the temperature issue. That big magnet will keep the amp temps away from the VC (voice coil), and visa versa. Shouldn't be a problem.

Bob


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## bambino

Great job with the craftmanship! And nice work shop as well:T


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## zero the hero

beautiful work!


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## Bob in St. Louis

Thank you guys for the complements!!!!

Got a bit more accomplished this weekend and thought I post a few more pictures.

First up....
The thin sheets of veneer (that are almost five feet long and 22" wide) need to be soaked with a wood softening chemical and pressed. These have been pressed for several days ....granted, longer than needed, but that will do nothing but make our lives easier later down the road. It's hard to press something that large, but the sheets are wrapped in wax paper (so the moisture doesn't get sucked out), then every piece of large plywood I have is placed on top, then all the heavy boxes of speaker parts are placed on them, and finally, a few 2"x4"'s and clamps to squeeze them into submission. 
You can see a bit of the veneer peeking out, in the lower left of the photo.










I don't have any photo's of the actual veneering process (yet....since it's being done at another fellows house), but after the veneer/vacuum press, here's what comes out.
The darker areas are where I've soaked the driver cutouts so I can run a razor blade through it without as much 'chipping' of the wood. 
The baffles are three layers of plywood thick. It is necessary to place the driver cutouts back in the holes so the vacuum press doesn't shatter the veneer. 
Note to self: Next time, veneer first, then do the router work. Ugh...

That's about enough typing for tonight, the rest of the pictures should speak for themselves. 

























































Tony requested the side braces be taller, and with a radius inside the 'crotch' area.
Here's the second prototype, on the left. He didn't care much for the first generation on the right. 












That's enough for this weekend..... "Bob out".....


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## Bob in St. Louis

Here's a couple rare, mid-week, photo's.

First picture is doing double duty. I had to locate the t-nuts and clean out the residual glue from the veneering process (note the bolts).
And second...in order to ensure a perfect 90 degree sanding surface of the thin side bevel for the next layer of veneer, I made a (as perfect as I can) sanding block.
I lined the bottom horizontal surface of the block with slick packing tape to act as a "sled" to ease the sliding across the wood work surface. 
Next, I attached sandpaper to the vertical face. Instead of regular sand paper that wears out quickly, I used the belt from a belt sander. 
It lasts much longer, and requires an occasional quick blast of air to clean and unclog the abrasive surface.











And just to tease Tony, a shot of the back with the base attached.
I didn't notice until just now, the camera focused on the background instead of the speaker.
Sorry about that.


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## black_z

Looking good!!


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## tshifrin

I like all the fine detail in your account of the build; I'm learning a lot.
Fine work!

Tom


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## Bob in St. Louis

Thanks fellas! :bigsmile:


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## Bob in St. Louis

Wow, it's been a month....Well, sanding isn't much fun, very glamorous, nor is it worth taking pictures of. But to prove I've actually been doing something, here's what they look like after final sand, and after one coat of Linseed Oil.

I'll admit to touching them more than I should, if you catch my drift. 

Bob


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## studiotech

Oh man, those look excellent. Almost like they're carved out of solid wood the way you wrapped the veneer.

No plans for a rear leg support of some sort? Once I added mine, it stabilized the baffle nicely.

Greg


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## Bob in St. Louis

Thank you for the complement Greg!
Check out the last picture on page four. The leg on the left will be the one we're using. 

Bob


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## Bob in St. Louis

Nothing ground breaking, as layering coats and sanding in between isn't much to look at from one step to the next, but I have made progress on the bases.
So here's a few pictures of the bases and the baffles. The baffles in the pictures are sanded and awaiting their next layer, so if they're dull and splotchy, that's why.


I've been compartmentalizing the cavities on the bases. Each cavity has it own purpose. The large one holds the amp and will be 'backfilled' with sand. The next largest will support the crossover and willl also be filled with sand. The next is 100% sand. The two smallest will be "open" and void. There needs to be access to the bolts that attach the baffle to the base. Obviously, we don't want sand leaking from one cavity to another, much less on Tony's carpet, hence the massive amounts of glue on the seams. Not only is each piece of wood glued and nailed, but then glued again with the nasty looking stuff you see here. This is the inside of the bottom and if all goes well, will never see the light of day after final assembly.










Here is the "cap" for the base. This will hold the sand in. I'll be using single sided foam tape (Speaker tape) as a gasket to help hold all the sand where it needs to be. The 2.5" holes are so I can stick a ratchet in there to tighten the bolts.




















The "base for the base". This is where the 2" spike will attach to the t-nuts and support the entire structure.
At this point, everything you see that's white, or plywood will be painted black when all is said and done.


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## tshifrin

This work of art is not what I expected when I started following this thread.
Fine work; simply awesome.

Tom


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## bambino

The veneer on the baffle's is very professional looking, again, great job and can't wait for a final pic.:T


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## Bob in St. Louis

Thank you very much fellas! :bigsmile:
This project has taken much longer than I expected. I can't wait to see the final pics either! :rofl2:

Bob


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## Bob in St. Louis

Update....

The bases tip the scales at 63 pounds each. For perspective, my 8 year old daughter is 52 pounds. I do not enjoy carrying these around the shop. 
When I'm older, I think I'll build smaller speakers. I dread moving these when they're finished!!

Here the baffle are swinging from my basement ceiling (note the wires), drying from (yet another) coat of pretty juice. 
In the background the painted bases sit in pieces on the workbench waiting to be filled with sand, amps and crossovers.









Here's one base filled and leveled with sand, and the other almost filled:









Once filled with sand, I clean the base where the gasket will go, and place it on the mating surface:









Then I capped the bases, and place them on the platform. The platform has the 2" brass spikes:
All that remains is to wrap up the pretty stuff on the baffles, mount the drivers, mate the baffles to the bases and wire them up!


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## Bob in St. Louis




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## Bob in St. Louis

Thanks jtemp!  

We have ignition in speakerland.  

Here's the new speakers next to my old (plain) speakers.........















































Here's a few shots of a David Gilmour Bluray concert. No particular reason I took this many pictures, I guess "just because I can".....I suppose. haha
But the speakers look and sound pretty good playing Mr. Gilmour, if I do say so myself.
I'll listen to them until next weekend, run them through their paces to make sure there are no squeeks, rattles, or buzzes.
Everything from classical, to Diana Krall, to Harry Connick Jr., to Mettalica, to Skrillex will be played.

Then I deliver them.....<sad face>


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## Bob in St. Louis

The speakers have been delivered. Shipping (in my truck) was uneventful, which was one of my worries. Picking them up to load and unload was not much fun at all though. 
Here's a few shots of Tony's room. 

In the first pic, you can see the speakers they're replacing (with the Indy 500 in the background)
I think it's neat to see the light shine through the back of the driver:










Here's Tony wiring them up. Of course I had my camera in hand, so a shot of Tony's bum seemed like something that needed to be done. ha ha
Otherwise known as....."_A view of the typical audiophile in his natural environment_":










And the last picture. The view Tony has been wanting to see for a VERY long time now. And with that, we'll put and end to the pictures and this project. 
Thanks for following along and for all the kind comments:


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