Dual Inifinity sub with alpha-8 minion build

[mummykicks]

It's only about 6 months late, but I finally finished my HT mains & subs build after a workbench and woodworking shop setup in my garage derailed me. Woodworking is right after boating as far as expensive hobbies go, but it fills the time nicely lol. Not sure how much I'd have to spend for commercial speakers that match these, but I'm guessing it still isn't enough to cover my shop expenditures.

The subs came in at about $200-$220 each as I paid $67 for the drivers and about $125 for the dayton 250W plate amps I have on these beasts. Based on the modeling, and the fact that I've got two of these I could never see pushing more than 150W through these guys, so I think the 250W amps are more than sufficient.

The alpha minions were $206 each from http://www.diysoundgroup.com/wavegui...lpha8-kit.html
Everything is made from 3/4" mdf, and I added an internal brace (same size as the top & bottom of the minion) with cut-outs between the woofer & compression driver.
Top section of the minion is stuffed with polyfill, bottom is lined with the denim insulation (which is great stuff) I got from HD. I put damping sheets on the minion walls.
Woofers have the sides lined with denim insulation and the mid section lightly filled.

The diamond stiffeners in the woofers are PL'd in place. My rebuilt wharfdale's are now doing duty as surrounds, which is overkill, but it does effectively give me 2 more sub woofers in the room, albeit at reduced volume.



IMG_0294

Sub I designed. Here is what the internals look like:

SUB

In the end I didn't add the little corner gussets, and I'm glad I didn't because when it came time to stuff it having those corners clear made it much easier. Port is 19" or so long 4" dia abs (because it's black) pipe. Everything is doweled, screwed and glued.


image
Unibox modeling:


infinity - 3


inifinity - 4

I've got CAD drawings of everything that I can send as pdf's if anyone is interested in building these.
They are still breaking in, but watching avatar last night I was hearing details in the soundtrack that I haven't heard before, like the beads in the female leads dreads clicking together. So great clarity and all kinds of boom from the subs.

[kenny_k]

Re: Dual Inifinity sub with alpha-8 minion build

Good looking build. Did you use duratex?

[tc]

Re: Dual Inifinity sub with alpha-8 minion build

Those are sweet looking Kenny! Would be very interested in hearing your impressions of the Alpha-8's.

[Jay1]

Re: Dual Inifinity sub with alpha-8 minion build

Great setup, nice job!

[mummykicks]

Re: Dual Inifinity sub with alpha-8 minion build

Good looking build. Did you use duratex?

No, but I should have. Even with like 3 coats of primer and several top coats I still have an uneven finish that matches my spray pattern. Maybe more coats would improve it, but some textured finish is the way to go if you don't have a paint booth and a good spray system.

I haven't got a whole lot of time listening to music with these, but there is a surprising amount of bass from these given all the people commenting that these need a sub. I was playing around with my sub-gain in my AVR while listening to some steely dan type stuff (the bass was very prominent) and was wondering why I wasn't hearing much change. Went and looked at my plate amp and it was off!
The one thing I did find was that some of my old CD's are basically trash now. Good recordings sound great, bad ones sound bad...

Now I was doing 7 ch stereo mode, and my surrounds have 10" woofers in them (used to be my mains) so they helped fill in the low end a bit, but even when I switched to 2 ch it still didn't lack much in the bass dept.

I certainly don't need more output, as my comfortable volume level is -10db from where it was before according to my avr volume levels. I think you'd need a really huge room before a 12" or a 15" system would make a difference IMO.

[Hollywood]

Re: Dual Inifinity sub with alpha-8 minion build

Nice job,

Any reason you went with 2 cheaper subs over 1 more $$?

Are you running a center? doesn't look like it, how you finding that?

I have 2 Minions waiting to be built, am thinking to order 3rd for a center.

Cheers

[isaeagle4031]

Re: Dual Inifinity sub with alpha-8 minion build

The Infinity subs are great subs, regardless of price. Very versatile. Using one expensive sub vs 2 lower priced units is not always the best way to go. Using 2 subs in separate locations will also help to reduce or eliminate room nulls.

[clearwaterms]

Re: Dual Inifinity sub with alpha-8 minion build

Mummy,

What are you doing to cross over between the lows and highs? Are you just using the LFE output on your AVR to cross the devices?

[mummykicks]

Re: Dual Inifinity sub with alpha-8 minion build

Nice job,

Any reason you went with 2 cheaper subs over 1 more $$?

Are you running a center? doesn't look like it, how you finding that?

I have 2 Minions waiting to be built, am thinking to order 3rd for a center.

Cheers

For one thing I've got a 7.2 avr. For another I needed to get the minions up to ear level, so I sized the height of the subs to do that. Also, multiple subs help eliminate room modes.
My center channel is actually a Zvox 580 that's just below the tv. I bought that prior to discovering DIY audio, and before I got an AVR. Rather than try to sell it I just went up in price until I got an avr with pre-outs for the center channel (I was also toying with the idea of doing a mini-dsp at some point, so the pre-outs would come in handy). I connect the center pre-out to the zvox input, since it's got internal amps.
Which in hindsight wasn't a bad configuration, since my avr only needs to drive the mains and surrounds, with the mains being high sensitivity, it really doesn't have to work hard at all. -30db on the avr volume is about as loud as I'd ever watch a movie, and loud enough that you need almost have to shout to get a person 3 feet away to hear you. High sensitivity really rules for HT IMO.
I watched a few movies sitting on the left basically right where the right speaker is pointing but about 3' from the left speaker, which would normally be a pretty crappy area to sit, but it sounded just as good as it does in the normal 'sweet spot' centered on the speakers.
If I were you I'd build the 2 minions and try them out without a center channel first, you might be surprised.

clearwaterms - I'm using the sub outputs on my avr, and currently have it crossed at 100hz just because I want the subs more involved, but 80hz is probably fine as well.

[Hollywood]

Re: Dual Inifinity sub with alpha-8 minion build

Thanks mummykicks,

think i'll go with the 2 Infinity subs in 1.25cft sealed, instead of 1 sub(TC Epic 12"/2cft sealed/500w amp was planned), the room is open plan 6m x 6.8m(kitchen/dining/lounge area) so the 2 subs should work the room better, in theory. 70/30 music/movies

The TV will be wall mounted, and whilst I can fit a 3rd Minion under it, it would mean the bottom of the TV would have to be 1m high from the floor, and I'm trying to keep it at .8m. So a horizontal center would be better, I hate having to look up at a Tv.

thanks again

[Thumper Tom]

Re: Dual Inifinity sub with alpha-8 minion build

.

[Hollywood]

Re: Dual Inifinity sub with alpha-8 minion build

Hey mummykicks, finally got my set up nearly done,

http://www.diysoundgroup.com/forum/index.php?topic=401.0