Wayback: 1997 Firebird quad-isobaric, all-passive hatch-eater (and it's precursor)

[geolemon]

I only have a scan of some physical photographs - of an actual driveway install - these pics are literally in my mother's garage since I wouldn't have a garage of my own yet... I would have been 21 or 22 years old here. You can see from the scrap pile in the background that I did a bunch of installs in this garage over the years prior.

A few things you can spot if you look at the pictures closely:

• A single Soundstream 2 channel amp powers everything, using the passive crossover network I built on either side, to send the lows to the sub, and highs to the front - with enough components to manage the wattage.
• The amp is mounted on a floating piece of 3/4" acrylic, back-lit with a blue neon motorcycle license plate frame hidden under the amp in a cutout in the glass.
• The amp/crossover rack is covered by a thin plexiglass cover, with a JL logo cut out of it for heat to rise to escape the amp - there's two small hidden fans on each side blowing in, forcing the air out the JL logo.
• There's a 3/4" acrylic window behind the four subs that play into the interior, covering but displaying the four subs inside the enclosure.
• Those eight subwoofers are actually installed in an isobaric arrangement -
  
  • four below with only about 4 cu.ft sealed - roughly what two of these subs would use
  • Four above with the magnets in a completely sealed coupling chamber - all that does is use air to couple these four subs with the four subs below. It's technically the same as doing a clamshell isobaric where you mount two subs face-to-face, but you don't need to wire one sub out of phase this way.

For those who don't know - isobaric was something we did back in the day to let a sub play low in a small box. Usually, you'd clamshell two subs face-to-face and wire one out-of-phase so that the cones moved in unison rather than fight each other. The air coupled between actually couples them, and without explaining "why" - you get the full performance of a single subwoofer in an ideal enclosure, but in half the enclosure size. So, if you had a subwoofer that needed 2 cu.ft., you could do that... or you could buy two of them, clamshell them, and get the exact same performance in a 1 cu.ft. box.
...or in this case, the exact same performance as four 12's sealed in 8 cu.ft. ideally - well, he definitely didn't have room for that, so... 4 isobaric pair in 4 cu.ft.

Kicker's Solobaric was born from the Isobaric principle that was popular in the late 90's - some smart engineer decided to try to use a double the moving mass (like having two cones) and just about double the motor strength (like having two actual motors) to achieve a "small box sub" in a single subwoofer. And today - basically you can't buy a sub that doesn't follow this formula.

I don't recall what component set we used up front, but it was a 2 way 6.5" component set with the speaker and tweeter in the factory locations. I believe we retained the rear speakers off head unit power, for some subtle rear fill. I don't recall what head unit was in here either - they had those GM 1.5 DIN units. Might have been the same Pioneer model that my best buddy who had a Z28 Camaro had in his.


I wish I had construction shots of this one - I love how clean and simple that box appears from the outside looking in, because the actual construction of that box was complex.

But at least I have this - maybe better than build shots - the box PRIOR to this one:
Even more dated fun - this red box in the top two photos USED to be in the deep well of this car's hatch. If you are familiar with Camaros and Firebirds of the 90's, you'll understand how it fit into the well - it was rear-firing. The port looks tiny but I don't believe it chuffed - back then these subs didn't have much displacement. Pretty sure they are original 10W1's, JL's least expensive back then.
That was the first install I did for this guy, at least 2 years prior.

Talk about a dated finish - anyone else old enough to remember when faux finishes were cool?

The green one was actually for an 80-something land-barge station wagon that a buddy of mine had, which had one of those rear-facing fold-down seats in the gigantic hatch area. This green box was built to fit into that tub where the precursor-to-third-row-seats folded down into.
...guess what? It's also isobaric. It's a bandpass box, one sub in the "front" chamber, the other in the "rear", both vented (you can see in the second pic), and in this case with them wired out of phase so the air in the coupling chamber is static also. The subs aren't permanently in there... but I sure don't remember what the hell kind of weird engineering I did to allow them to be removed.