Contour Enthusiasts Group Archives Forums Modifications Audio Isobaric loading

Does anybody do this anymore? Seemed popular years ago but it seems to have fallen out of favor. What were supposed to the advantages of this?

They were used so you could use only half the enclosure space. It would cut the VAS in half.

Still quite popular in Home Theater. Check out:
http://home.att.net/~kloneaudio/page21.html

Isobaric push-pull designs also greatly reduce second order harmonic distortions due to the cancellation of asymmetric nonlinearities between the two drivers.

The only drawback that I can think of is a reduction of midrange frequency response - which is probably a non-issue if all you're interested in is a subwoofer.

-Wes
98 SE Sport

Isobaric lost favor in the car audio market right around 1994 or 1995 when the solobaric was designed. It was the first sub to add mass to the cone (which simulated an isobaric design) to lower the Fs and allow a much smaller box than was tradionally seen. The problem was that it had the same effect as an isobaric design in that it lost a substantial amount of effeciency. It was a marketing strategy that payed off, because companies like JL, MTX, etc soon followed with similar designs all with lower effeciency.

Obviously the biggest advantage to the design is that 2 speakers will fit into a box 1/2 the size of a single woofer. If space is at a premium, it's still a viable alternative, you just need to realize that you will need 2x the power and 2x the woofers to get the same output as a single woofer.

Wjang is correct in some cases. It depends greatly on the design. The application that uses two woofers to reduce second order harmonic distortion most effectively is a sealed subwoofer design like M & K push pull home theater subs that aren't isobaric but do have the cone pointing out on one subwoofer and the magnet pointing out on the other.

Aaron, that wasn't an isobaric design, that was an infinite baffle.

Oh, yeah. But it's still popular in HT because of SAF of size limitations. My brother has 8 IB boxes of 16 12" drivers in his theater. But that had nothing to do with SAF.

Is your sister in law looking for a new husband? j/k

Here is a link that might give you some good info:
JL Audio Isobarik Tutorial
It gives some Pro's and Con's of different configurations.

If you ever get to see his house, you'd think so. But, for some reason she puts up with him. I'm not sure what that is yet but I need to find out and use it.