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Discussion Starter #1
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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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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Discussion Starter #6
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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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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Discussion Starter #9
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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Discussion Starter #11
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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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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Discussion Starter #13
<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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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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Discussion Starter #15
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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"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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Discussion Starter #20
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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