Fiberglass Enclosure? (1 Viewer)

[Rich_P]

I've done quite a few car audio installs, and i'd like to try my hand at DIY home speakers. I have a strong urge to make some sort of crazy enclosure. Right now i'm seriously contemplating trying to make a replica of the B&W Nautilus Prestige. Probably not the best idea for my first home speaker enclosure, eh? hehe... what can i say, i like a challenge.

Honestly, i'm not super concerned about the sound quality of these things. Right now i'm looking for mostly aesthetics (by now i probably have a lot of people rolling their eyes!), since i actually already have many thousands of dollars of home theater speakers that i'm satisfied with. That being said, i don't want it to sound HORRIBLE! So here's my first question - what type of material would i use to produce that shell shape? I searched around on this forum and didn't see much talk of fiberglass - which would be (somewhat) easy to form into that shape. Would a fiberglass enclosure on its own be stiff enough? I'm used to reinforcing fiberglass enclosures with MDF or some other material, but that might be difficult with that kind of crazy shape. Any suggestions? Just make it extremely thick walled?

My second question is about the Nautilus itself - can anyone tell me anything about that shape? Is it actually like a spiral tube, or is the shell just an odd shaped single volume? Does it have a port somewhere? I would assume that there's more to it than just its volume - are the exact dimensions and curves crucial to its sound? I understand that my driver selection will obviously affect the exact measurments of everything, but i'm just beginning my planning phase, so i'm looking mostly for general suggestions here. However, if anyone wants to suggest some driver selections totalling under $2k i wouldn't complain! Keep in mind that the cones will be visible, and thus i'm looking for attractive components.

Thanks ahead of time for your help guys...

-Rich

 

[ThomasW]

HERE's a link to a thread that should not only get you inspired, but should answer some of your questions

http://www.diyaudio.com/forums/attac...?postid=234562

 

[Rich_P]

Thanks Thomas! Those are excellent! Maybe i'll contact the guy that originally posted those pictures to see if he can give me a little more in-depth info.

 

[MichaelDDD]

Whoa. You get thousands of cool-points for even thinking about taking on a project like this!

Those spiral-shell shapes are molded somehow...blow molded, maybe?

What you've got there are three separate chambers; good for acoustic separation...no need to "box in" the tweet and the mid from the back wave of the woofer. Definitely different looking! Not my cup of tea, but kudos to you if you can pull it off.

 

[ThomasW]

Those spiral-shell shapes are molded somehow...blow molded, maybe?

Look at the link and you'll see how they were made.

 

[Joe Tilley]

Rich, Fiberglass can be several times stronger than wood at a fraction of thickness or weight. And the cool thing is you can do just about anything with it that you can think up.
I worked for a Company for almost 5 years that built fiberglass plugs & molds for Outboard Marine along with some smaller molds & parts for various other companys. Fiberglass is my favorate material to build with & I myself have thought about building some enclosers with glass like you are. Not something as complex as the B&W's but I have a taste to always be different. The only thing that is stopping me is not knowing how to build the right size encloser for a particular speaker.

 

[Rich_P]

Joe - i love fiberglass too, which is why i want to attempt this! Unfortunately i'm a part owner of two small software companies, and time is something that i DON'T have a lot of. However, if i can get a few products we're working on out the door by the beginning of 2004, i'll probably take a month or two off. Which is why i'm starting to plan now for how to most effeciently waste my time... haha.

At this point i figure i could either do a mold out of foam, or do something similar to the posted link with a frame. I'm more confident in my chances of getting the frame right. Fiberglass really isn't all that expensive, so the fact that i'm not sure if i'll get the dimensions right the first time won't be enough to stop me! Actually, the total VOLUME of the spiral enclosure won't be an issue for me - i can easily have AutoCAD or 3D Studio Max calculate that for me once i've drawn my model. My main concern is whether the length of the spiral / diameter / number of coils etc will have serious effects on the sound. I have a feeling my first attempt is going to sound like hell. I'll keep you all posted on what happens.

 

[DanielGM]

Rich,
The diameter and number of coils shouldn't matter, only the length. The nautilus' use a transmission line design, which cancels the back wave coming out of the driver by absorbing it in those tapered tubes. I can imagine all the tubes are filled with some sort of absorbant foam or padding. The only thing that should matter is that the tube is long enough to ensure that the wave is completely absorbed, longer wavelengths (lower frequencies) require a longer tube, which is why the the tweeter's tube is a lot shorter than the coiled bass tube.

I would do some research into transmission line design, but you should be able to design some excellent enclosures using that design principle and fiberglass construction, I would be interested to hear more updates about your project.

Where in VA are you?

 

[Rich_P]

Thanks Daniel, i'll start my research. Though i still won't be able to really start my models until i've selected drivers...

I'm in the northern VA area. Chantilly to be more specific.

 

[DanielGM]

ahh cool, i'm in fairfax.

 

[Rich_P]

Daniel - you suggested that i check out tansmission line designs. This made sense to me initially. However, don't transmission line designs terminate in a port? These speakers do not appear to be ported - it would seem the port would have to be at the very center of the spiral. Is the port not necessarily required as part of a transmission line design? Or are the B&W nautilus speakers just a spiral sealed chamber?