Isobaric Applications
Isobaric configurations are not the magic fix for enclosure design. Correctly used, this application does offer some benefits, but at a price. The term Isobaric is Greek in origin. "Iso" meaning constant and "Barik" meaning pressure defines the operational characteristics of this use of multiple woofers. The air space between the to woofers remains a constant pressure and the result is a single drive unit with dual motor assemblies. Figure 10 The difference between a single woofer and an isobaric pair of woofers are...
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of the isobaric pair of woofers is half that of a single woofer. Fs
of the system remains the same. The
maximum output capability is the same a single woofer in as enclosure
that is twice the size. The
efficiency of the system is 50% of a single woofer. The
electrical power handling of the system is double that of a single woofer. The
mechanical power handling (X-Max) of the system is the same of a single
woofer. The
moving mass of the system is doubled. |
There are several performance differences between a single woofer and an isobaric pair of woofers. Following is a brief description.
The required volume for a sealed enclosure is half that
of a single woofer.
If
you need to increase the output of an existing enclosure using a single woofer
but need to maintain the same frequency response,
addition 3 additional woofer (to create two isobaric pairs) will
increase the output by 6 dB if the power is available.
When
using a vented enclosure of 3 or more cubic feet, an isobaric system will
reduce the required volume by half. For enclosure
volumes less than 3 cubic feet, it is important to consider the needed
length of the vent.
Two major trade-offs when using isobaric configurations is required vent length and cost versus performance. As the enclosure volume decreases the required vent length increases exponentially. The isobaric configuration reduces the required box volume in half. This results in a drastic increase in vent length required. The increase in cost is a perspective issue. Not so good for the consumer but great for the dealer.
There are different ways to configure isobaric applications. Following are the different configurations and the performance characteristics of each different style.
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Magnet
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