Kairos

[richidoo]

Also building ported boxes to see how that sounds, it will reduce woofer excursion at LF to allow louder playing.  Also trying reducing the baffle step correction to get some more headroom before bottoming. They will be happier with bass drivers.

[Bob in St. Louis]

Since you've got 2" to work with, how about two layers of BB ply with sand in between.
like a "box in a box".

Regarding the Panzerholz, I've done extensive research to find a dealer (a couple years ago) to no avail. I even had a forum buddy ("Thunderbrick") visit some hardware stores in Germany while he was over there. In the end, I gave up. I'd greatly appreciate a link to the dealer you're referring to. 

Bob

[richidoo]

Thanks Bob! You reminded me that I already thought about sand about 2 months ago, based on your success with it, and already designed a box like that. I think that is the best route.

These are the dealers I have found for Panzerholz. It is made in Germany by the Delignit company. You might find more sellers if you search Delignit. There's not much searcing just Panzelholz, just a bunch of high end audio links.  

http://www.ltlewis.co.uk/b15.htm  UK
http://powerstreamindustries.com/autosport-wearply.asp   NC
http://bkbindustrial.com/  Canada

The NC seller tops out at 1/2" thick, but that's thick enough for how you build!

[Bob in St. Louis]

Glad I could help Rich.

I've wondered about the sand fill thing. I was thinking about mixing in a 50:50 of sand, and some form of soft mushy bead. Like a rubber pellet type thing. In my mind, I see the dampening effects of that mixed with sand being better than just sand.

Thanks for the Panzerholz information. 

Bob

[richidoo]

Interesting idea about the rubber beads. I was thinking about Green Glue being a great damping material, but I don't think it could be used with sand. I did remember an old idea I had about laminating several layers of thin wood sheet together with green glue. I once did it with two pieces of 3/4" greenglued together. It worked pretty well. But more layers of thinner wood would probably work better. Lightweight layers should damp easier than heavy, but stiffness suffers with thin wood. Hence the invention of carbon fiber! No I'm not making CF speakers, at least not yet...

So how should I go about making this sand cabinet?   Should I build a frame along the edges, and glue on the thin wood panels? Or just glue together the panels on edges without a frame, with one layer of continuous sand all around the speaker?

Do I need small cube wood blocking between the panels to keep them from bulging out from the sand/gravity pressure? Would those connections diminish the damping of the sand? I guess 1/4" wood is stiff enough to hold up some dry sand without flexing too much.

How do I handle the horizontal panel at the top? The sand will only damp the bottom (interior) surface. I was thinking I could slant the top panel 15 degrees to that there would only be a small undamped air bubble at the very top corner after sand settles.

Should I make all the panels open to each other so that the sand flows in from the top, or make separate sand filled panels  that glue together?

Thanks for any advice, oh sand-master - or anyone else!!
Rich

[Bob in St. Louis]

It wouldn't be too hard to built, basically each speaker would consist of building two boxes, but might be hard for me to explain....
Let's see. To keep it simple, let's say we're building a cube that consist of nice round numbers.

Build the inner box; 10"x10"x10"
Space strips of 1"x1" wood all the way around the box.
Built the outer box 12"x12"x12" (remember, it's 12" on all outside dimensions, because of the one inch thick strips on all sides).

Leave the top panel off. Fill with sand. tap with rubber mallet to help settle sand, refill as necessary. Install top.

Where the wires come through, install a 1" thick block that's 2"x2". You can then safely drill two holes from the outside all the way into the interior without drilling into the sand cavity.

Where the drivers mount, build a simple box out of the 1"x1" strips of wood. Attach to the face of the inner box.

Glue all strips to ensure the sand doesn't come out.

I can link you to some of my build threads where I did sand fill in some of my baffles if you'd like.

There was a fellow that built a very large subwoofer and used the method of sand fill I'm referring to with those spacer strips. I'll see if I can find it, but it's been a while since I saw it.

[Bob in St. Louis]

Can't believe I found it that quick.
Check >>this thread<<, that should give you an idea of the "box in a box", with sand in between.

[richidoo]

Thanks Bob, that makes sense.

What do you think about mixing the sand into casting epoxy and pouring that between the walls? "Epoxy Granite" or "mineral casting." It's supposed to damp the vibes very well, originally used on machine tools to damp metal vibes during ultra-precision machining. Same concept as "cultured marble."

[Bob in St. Louis]

I know that's what Vapor does (because I 'busted him') while he was doing it. 
So there's some merit to, for sure.

The thought behind the sand being "free' and able to move, is that the vibrations created by the drivers will cause the sand particles to resonate, thereby absorbing the vibrations.
That's the way Hawthorne and GR Research do it.

So....Who is doing it the correct way??

[richidoo]

I was hoping you would tell me!

I think the correct way is the cheaper and easier way - dry sand! Casting epoxy is expaaaaansive!

[Bob in St. Louis]

I think the correct way is the cheaper and easier way - dry sand! Casting epoxy is expaaaaansive!

"Yes", that is the way I do it, and the exact reason why I do it that way.  

Although, my opinion will be poo-poo'd, as I'm not a real speaker builder, but I have slept in a Holiday Inn Express.  

Bob

p.s. By the way....I fixed the link in post #51 to the sand filled sub from GR Research.

[_Scotty_]

We know Abbie is the speaker builder in the family.
Scotty

[Bob in St. Louis]

The legacy I've created precedes me. 

[richidoo]

Bumping this back to life for an update, if anybody cares.

I found the cause of the mid bass blurring that I mentioned above. It was resonance in the woofer coil. I connected the amp to the midwoofer directly and the problem disappeared. The problem was some resonance in the crossover circuit due to the high Q of the series woofer coil. A friend advised me to put a damping resistor across the coil to reduce the Q of the coil and stop any ringing it might have. It took a few tries to find the resistor value that did not alter the woofer voltage at the crossover freq, but I did find it and the woofer sounds clearer and calmer now. It is easier to concentrate on the music, there was a busyness, clatter that the coil damping has removed. The blooming of voices at 200Hz is mostly gone. What remains I can now hear, due to the added clarity, is just proximity effect from cardioid mics. Before it just sounded like distortion that could be coming from anywhere.

But I really liked how the woofer responded to the direct connect to the amp. The SB acoustics Satori woofer combined with Sol's I-60 amp with JPS Superconductor wire between them was impressive. No wonder this the Wilson's new main midrange driver. The bass control and overall clarity was much better than with the passive crossover, even though I am using huge 10ga coil. So I'm gonna try some active crossover experiments with the speakers. I'll start a new thread for that when I get something happening.

I also designed a new floor-standing box for the Kairos, which has Qtc of .5. I like tight bass and I cannot lie. I also bought some 11" woofers to build a 3 way version and I have the box designed for that too. Active crossovers will make developing a 3way easier in some ways, and give me some benefits that passive crossovers can't touch, but I'm drawn to the challenge of doing a 3 way passive crossover also. Just pipe dreaming now.

[StereoNut]

You never cease to amaze me Richidoo.   Whenever to start up that next project, please take lots of pix along the way.

SN