The Minions

[Soundslike]

Re: The Minions

Not much to see, just yet. I'm waiting for a bit of body filler I smeared on them to cure. It would appear that I didn't add enough catalyst.

[Leroy R]

Re: The Minions

I'm clearly going to have to get better with body filler. I tried to use it for the first time today on a pair of the Overnight Sensations I am building and not sure I gained anything from it. The first batch I made was too much and most of it hardened before I could use it. I sized the second batch better. Most of it sanded back off and I'm not sure what I gained from it. It didn't seal the end grain of the mdf or hide the seams. Had to sand the first coat of primer off, because there were scratches showing in the body filler. A lot of hassle for little return.

[Soundslike]

Re: The Minions

I'm not trying to promote any particular process, but for me, the resin/body filler process is worth doing. On the other hand, if a builder has a process that produces results they're happy with, and it's easier for them than using resin and body filler, then it probably doesn't make sense to go through the trouble of working with the resins, fillers, and catalysts. It can introduce new complications, such as the ones you described, or the problem I'm coping with (too little catalyst and slow cure). The process I'm using does produce benefits -- whether they are worth the effort is an individual decision. I coat the entire box with fiberglass resin, diluted about 40% with acetone. That hardens and seals the MDF very well -- it completely solves the exposed ends problem. But it also leaves a surface that will need sanding to eliminate brush strokes, or at least get them down to a level that can be filled with primer. Once that's done, you have a much harder surface that can be finished to the same level of quality as you see on cars.

You've probably read the strings where various builders have described their preferred finishing methods. There are lots of different options and many of these builders have been very successful.

I should mention that I don't consider myself yet to have achieved proficiency with the resin/body filler process. Like all finishing materials, experience is needed before I'll be at the point where I can confidently predict I won't encounter any problems. But in my opinion, and I believe in the opinion of the guys that build the custom car installations for a living, fiberglass, resin, and body filler will produce a superior result, if done correctly. I recently posted a question about dealing with sandpaper clogging (when sanding resin) on a fiberglass forum. It surprised me to learn that no one had a ready answer to the problem. From that, I've concluded that clogging is something you can expect to encounter to some degree, any time you use resin. The suggested way to deal with the problem I got back from a very knowledgeable poster on the forum, was to spray the resin on, using something called a "dump gun" (They're $119 at one Internet site) That's followed by a more easily sanded material -- a poly primer, if I recall correctly. The idea is to avoid the need to sand the resin altogether. I'll probably try this method, but I can readily see that this "solution" is probably much more bother than the average builder is willing to take on, just to avoid sandpaper clogging.

Veneering is probably an easier way to get a good looking result.

[Leroy R]

Re: The Minions

I'll have to try the resin next. I was a bit frustrated yesterday. On top of what I described above, I dropped one of the boxes on the garage floor right after applying the first coat of paint. This caused a few minor dents and messed up the paint. I tried to feather out the edges of the paint where it was messed up, but now that they are finished, you can still see the damaged areas. It's going to have to do as I am not going to sand them all the way down and start over.

[Mikers]

Re: The Minions

I coat the entire box with fiberglass resin, diluted about 40% with acetone.

40% acetone? Could be your curing problem, I thought 30% was pushing it.

If you live where it is hot and sunny (25C +) I suggest leaving the box in the sun for an afternoon, covered in black if you can. Give it a good bakeout. This will shrink it. Do it between resin and filler.

[bungelow_ed]

Re: The Minions

Are you all talking about resin or epoxy? I haven't worked with resin in 20yrs, but have much more recent experience with epoxies used in boat building.

Epoxy tends to develop an "amine blush", a waxy surface build -up that can clog sandpaper. One of the way to deal with amine is to use a cabinet scrapper.

The scrapper takes off the amine and levels small imperfections, read brush strokes, fish eyes, and dust/insects. Sanding, if needed goes a lot better after scrapping.

I am especially fond of System Three because it mixes in a 2:1 ratio, is readily available and well supported. As I recall System Three used to sell an inexpensive small kit for first time users. They also sell a body filler and cross-linked high build primer that is tough as nails when cured. BTW, I have no connection with System Three, yadda, yadda, yadda.....

[Mikers]

Re: The Minions

its fiberglass resin

forgot, another thing you can try is to back scrape with a razor blade before sanding. Scrape it enough that you get the shine off, then it will sand better. (by back scraping I'm referring to going over the surface with the razor angled backwards so it doesn't dig in)

[Leroy R]

Re: The Minions

Well I couldn't leave it. The baffle took most of the paint damage when it fell so I sanded it down and repainted the baffle. Not perfect, but looks a lot better.

[Crayborn]

Re: The Minions

Ordered the parts today to make a set of Minions with dual drivers. Will let you know how it goes.

[michiganpat]

Re: The Minions

since the -3db of the ported enclosure is a little north of 100hz, would it be a good idea to toss a big NPE in series to attenuate the low frequency stuff out? using the impedance plot provided by PE and an online calculator, a 100uF NPE in series would provide a butterworth 1st order high-pass of around 80-100hz, wouldn't it? since you're on the upside of the impedance spike, not sure what the shape of that high pass would actually give you, though, since impedance goes from ~11ohm at ~50hz, to 20ohm at ~95hz, spiking to it looks like over 40hz at ~150hz, down to ~8ohm by about 500hz....

http://www.parts-express.com/pdf/299-249s.pdf

thinking about trying these drivers in my car, as I don't have very good options for speaker placement since I don't want to cut any panels (1976 duster with a fold down rear seat)

[ameuba10]

Re: The Minions

I was just crunching some numbers and these little guys and came up with a little trapezoidal enclosures for dual minion computer/ipod speakers. Using 1/4" material I got:

Height: 8"
Width: 3"
Depth (top): 3"
Depth (bottom): 4"

2-.5" ports 2 5/8" Long

If I'm right, this should give you .027cuft/.768L tuned to ~115Hz.

Should be able to be built using some $5 1/4" 2'X2' and $2 PVC

Paired up with a T amp, this should have you a nice set of computer or ipod speakers. This was a 'quick and dirty' calculation so someone please let me know if I'm off somewhere.

[Crayborn]

Re: The Minions

Any one run the numbers for a dual set up in a square box?

[Mikers]

Re: The Minions

What about 4 of these in a mini line array for an outside patio speaker? 3.5" x 3.5"x 16" ?

Would you want 4 compartments or just one long box? What would you do for porting?

I think it would be perfect for mounting in a corner close to the eave (single story house), angled down about 15-20 degrees.

Thoughts?

[Leroy R]

Re: The Minions

If you go back a page in this thread, I built a 4 driver cabinet. I built it so that I could play each pair independently or as all 4 together, because people had asked about both versions. I have a 3" compartment between the two driver compartments for the wiring. If that compartment wasn't there and you just had all 4 drivers in the same compartment, your dimensions would be 3.5" x 3.5" x 12.5" externally using 1/4" mdf. I think I would port them for patio use to get as much low end as I could. You might also consider Ed's build. He used this driver with the 4" Tymphany buyout and should be getting significantly more low end. http://techtalk.parts-express.com/sh...d.php?t=225362 Another concern I would have with using these outdoors, is that they are paper cones so you'd have to make sure they don't get wet.

[Mikers]

Re: The Minions

thanks

I like the 3" size and it's not for hifi, just background noise.

thanks for clearing up your center channel

what size port would you use for 4 in one box?

Thanks