Use an Isobaric Subwoofer Configuration to Save Space and Increase Quality of your Bass

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isobaricAlthough this type of subject is not limited to car audio, it is generally the most common scenario that would involve the need to save on speaker-box space, etc.

Many folks that are wanting hard-hitting bass in their ride, generally think that big amps, big subwoofers, big box = big boom. Well, maybe so, but we don’t always have the trunk space of a large family car or the behind-the-seat air space of a van, either.

I used to be big into the car audio sound systems for a few years (right after High School), have built many speaker boxes (ported, sealed… even helped build bandpass boxes with Plexiglas windows, and so on), and I only had to resort to an Isobaric configuration one time, during all of that, but many folks may be interested in this extra option.

Okay, for one, I must say that the bigger the box does not by any means equal louder bass. Big, sealed boxes commonly hit at a lower frequency and have better quality overall, but as for finding your highest db (decibel) potential, is about finding the perfect-sized box for the frequency that you want to peak at. For example, some people may prefer a tighter, more punchy bass that hits harder at a higher frequency – if you mainly┬álisten to hard rock, for example. On the other hand, a person who listens to rap may prefer a much lower frequency of bass, ya know, the kind that vibrates your seat even when you can’t even hear it. The human ear can only hear so low of a frequency (same applies to extremely high megahertz), so when you build a box that hits below the frequency of human hearing, it feels weird, to say the least (I’ve witnessed it before).

Anyway, they sell books for scientifically building the perfect box for your subwoofers, but that is not the primary subject of this post. Oh, if you are interested in such things, follow the link “Loudspeaker Design Cookbook,” and grab yourself a copy, today.

At any rate, I’m about to quickly go over the Isobaric configuration, its pros and cons, and why or when you should use it…

The main reason a normal person would want to use an Isobaric subwoofer configuration, also known as the “push-pull” subwoofer setup, is to cut your required box size literally in half, as you can divide the air space by 2, when using this method! Hey, that’s pretty dang good, if you require a 4.0 cubic foot box in a hatchback, and can get it cut down to a pleasant 2.0 cubic foot, eh?
The configuration is very simple, it’s just that you have to double your amount of subwoofers. In less words, we will turn two Subs into 1.
As you can tell by the image above, the push-pull effect can only be achieved if one of the subwoofers are wired in reverse. So, hook one sub up as normal, positive to positive, negative to negative, and the other Sub in reverse, such as positive wire to negative post of speaker and vice versa.

With two subwoofer cones acting as one, you have just created a “Super Subwoofer,” so to speak. By science, with the way this works, the required air space to basically operate at the same level as one, has been cut in half; presto! Since the opposing speaker that is facing inwards toward the other has been wired with a reversed polarity, you get the push-pull effect as when one pulls back, the other cone pushes forward; simple stuff here!

Now, lets get to the heart of the matter, as to the pros and cons and what type of situations would call for an Isobaric configuration.

Cons: Well, for one, you must have twice as many subwoofers to perform this and, depending on the brand name, this could cost a fair amount of extra money. Overall, per the amount of energy and/or power your amplifier puts out, Isobaric setups are not as efficient as single Sub units are.

Pros: I suppose one of my favorite aspects of an Isobaric setup is the lowered amount of distortion. Unless you have poor quality speakers and amps, this configuration sounds great and provides a tight, clean bass sound! The main Pro for this type of configuration is, of course, the box size is cut in half, which is great if you are short for room but still want some bump involved in your sound system.

In closing, here are the times when a person may need to resort to an Isobaric installation process:

When you have a very tight space in your vehicle, trunk, etc., and would like to have the sound of 2 subwoofers but only have room for one or have 4 Subs and only have room for 2, and so on.
If you have the extra money and have more Subwoofers than brains (just kidding) and would just like to enjoy the enhanced quality and less distortion that Isobaric sound systems have and/or have the time and funds to experiment with different options, etc.
If you have several low-quality subwoofers that you don’t want to throw away, but would like to find a way to make them sound semi-decent.
If you have a big amp with a lot of extra power to spare, and you are looking for a way to “amp it up” without excessive amounts of distortion.
If you are just seeking a tighter hitting thump and more accurate bass sounds for your sound system, and have the extra Subs and a powerful enough amplifier to work with.

So as you can see, many of y’all can do without this configuration, but there will be times that using this Isobaric Subwoofer Configuration to Save Space and Increase Quality of your Bass, will be the best option.


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