There are several different isobaric loading configurations to choose from, so which is the right one for you? This has no clear-cut answer. We do not recommend the use of isobaric loading to just anyone...we do not believe that the more subwoofers that you can shoe-horn into any given volume of air produces the best results. In fact, we're sure you've seen plenty of examples to support this line of thinking. So, we only recommend that you consider using isobaric loading if one or more of the following conditions holds true:
1. You have more subwoofers than space to properly utilize them.
The first condition is a common occurence if you decide to change vehicles and keep the sound system or when you out-grow that desire to consume every cubic inch of your vehicle's storage space with subwoofers. You don't want to sell your equipment because you've fallen in love with it, and so you begin to look for any possible way to keep all (After all, it *does* sound impressive to say "Hey, I've got 16 eight-inch woofers in the back of my Jetta"). Since iso-loading allows us to use the same number of subwoofers in half the space, an isobaric loading scheme might prove very attractive here.
2. You have more power than you know what to do with but little space to work with.
The second condition may hold true if you've suddenly acquired a 500W amplifier for your subs and your poor little 150W subwoofer just cannot handle that kind of power. In this case, you might switch from one 150W driver in a 0.625 cubic foot enclosure to four of the same drivers (2 isogroups) in the same sized box. This would bump your effective power handling up to 600W -- which should handle the added power just fine. Of course, you could also simply upgrade to a subwoofer that can handle the power.
3. You have more money than you know what to do with.
The third condition is pretty self-explanatory... you've got money burning a hole in your pocket, and rather than purchase a new set of tires to replace your balding Dunlops, you decide to splurge on stereo equipment and try to put as much stuff into your car as humanly possible.
4. You are a golden-eared tweak who can detect subtle non-linearities in your sub-bass.
The fourth and final condition is a subtlety that most probably won't be familiar with. One of the nice little side effects of using a face-to-face (or back-to-back) loading arragement is the cancellation or driver non-linearities. This will be explored a little later though.
Learn about other Isobaric Enclosure Types:
|"Piggy-back" tunnel load||
|Back-to-back tunnel load||
In short, if you're out to try isobaric loads for reasons such as "It looks cool" or "I heard that they 'hit harder than anything else," then your money would more likely be better spent on something else a little less costly. Of course, we wholeheartedly support those who love to try new things just for the sake of trying out new things or to further their understanding of various subwoofer systems, so don't take what you read here as discouragement...just a fair warning of what to expect.
With all this said and done, let's explore some of the advantages and disadvantages of the "piggy-back" tunnel load, back-to-back tunnel load, the planar load, and the "clamshell" isobaric configurations: