Orb Clones

Thinking of making some Orb clones, if not for the sake of the project then for the WAF.

Here's my rough plan, though I'd like to hear any thoughts you guys may have:

Drivers

I'll be using 3" full range drivers. Probably this Tang Band W3-881SJ. The downsides I initially see are the low power handling (15 watts RMS) and the impedance (8 ohm), making it difficult to do a "mod2" knockoff at 8 ohm, though I could add a resister in there if necessary.

If you have any suggestions for a better driver, I'd love to hear them. I'm looking in the $20-50 range.

Enclosure

I'm thinking of using 5" foam balls (here at JoAnn Fabric) as a base. I'll cut one side flat, then use fiberglass fabric and an epoxy resin to provide an exterior shell. (Added bonus: Maybe I'll do a final layer of black fiberglass or carbon fiber for a nice look.) I'll finish it up by hollowing out a majority of the inside , leaving some styrofoam for internal damping, drill two holes in the back for terminals, and add a mounting hole or some other method to attach it to a wall or stand.

I can't figure out how I'm going to secure the speaker to it. I'm thinking of possibly gluing it in, or making some sort of mounting bracket that I can glue on, and have threaded inserts on.

Future

1. I'm thinking if all goes well, I could do a "two way", and make an independent tweeter. Because of space limitations, I'd probably have to go with first-order crossovers for both speakers, but I could set it fairly high (7k?) since the 3" driver will be full range.
2. Upgrade to mod 2 or mod 4
3. 8" Subwoofer? I found 10 and 12" foam balls!

Again, please let me know any thoughts or ideas you might have.

Natedog - Unfortunate name, considering the news, eh? Thanks for the tips. I'd never heard of the baby powder finish coat but I'll definitely give that a try if I go that route.

LTD- I really like your idea of furniture legs. I'll be investigating that further later today. Nice graphics haha.

I could pretty easily route out the inside of the chamber too, then I wouldn't need a plug and I'd have a "unibody" speaker. The only disadvantage I see right now is cost, since the legs are $20 vs $5 + another $5 in materials. But 10 dollars for a lot sturdier cabinet isn't bad at all...who am I to complain?

I was able to find the original manufacturer of the ones you linked to. I can't find anything quite that size from a big box store. The ones you linked have a 6" diameter at the widest point, which seems a bit large for what I want to do. However, I found this one which is a lot closer to what I am looking for. I'll have to flatten it out, maybe with a belt sander.

Having found the original manufacturer, I can specify the wood I want. I'm thinking soft maple; from my guitar days I always liked the sound of maple acoustic guitars, so I figure that's at least a good starting point. Thoughts?

I'm going to be taking a little bit of a different direction. I found a thread over at diyaudio about using Ikea bowls for spherical speakers. I'm going to use some of the 5" bowls. Should be pretty simple this way.

Also, the drivers I originally stated are on back order, and I'd like to get most of this done this weekend. So I ordered these off of Madisound. Due to the high impedance (20 ohm), I'll be using two in parallel.

As far as enclosure size: I am aware that this is a bit small for these drivers. Assuming a thickness of 3/8" (seems reasonable from the picture), I get an internal volume of 0.025 cubic feet, though net volume will be a bit less due to the cutout and volume of the driver, so maybe something more like 0.023 c.f. Using this volume and the values published for that driver, I get a 6dB peak at 216 Hz and a Qtc of about 2.

If I port it, I could do a 3/4" diameter by 1 3/4" length port and reduce the peak to 11 db at 143 Hz, below my crossover frequency. I know the port is a bit small in diameter, but due to enclosure dimensions, I can't really go any larger.

Thoughts? Should I port it?

EDIT: Two in parallel will have separate enclosures (mod 2 style).

Is that the ported or sealed (I assume sealed)? What software are you using?

If I put in a first order high-pass filter at 450 Hz, I can limit the Fsc to 1 dB at 450, and still maintain an F3 of about 130 Hz. I'm not sure if there is software for simulating this (it doesn't appear that WinISD will simulate the filter for me, at least not the free version), however I plugged in all the math in excel and got the following. Setting my crossover at 180 Hz appears to work quite well with this filter. Now, I'm not very experienced in the audio applications of high-pass filters, most my experience is in process control, so I'm not quite sure how accurate my modelling of the filter will be. Anyone have some insight as to how this may actually behave?

EDIT: Detail of my modelling:

Attenuation of frequencies below crossover frequency = 6*log2(450/f)
This equation results in attenuation of 6 dB/octave, as is typical with first order filters
So that
SPL(filtered)=SPL(unfiltered)-Attenuation

4 enclosures = 4 drivers + 8 bowls.

What do you have?

LTD- This will be my first build, so I wouldn't say I shouldn't be doing it haha, but thanks. My education (and career) is in chemical engineering, so I have a pretty strong educational and applied background in mathematics.

What version of WinISD do you have? I just downloaded "WinISD Beta" which has a version number 0.44. Below 200 Hz I'll be crossed over to a subwoofer.


I don't understand what you mean by this.