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How Much Airspace Do 6×9 Speakers Need? We Take Scores!

Last Updated on: July 8, 2024

Is this your first time getting (and setting up) speakers or your first time buying ones that are 6×9?

Whichever it may be…

We’re here to guide you.

The entire process of finding the 6×9 speaker box measurements can get pretty tricky, and small differences in some aspects can lead to your subs’ quality and car audio degrading. 

So, let’s talk about the basics, the crucial points, and have all your questions answered. 

Keep reading so we can start.

What Air Space Is

When we talk about air space, we are mainly referring to the “volume” or air space of a speaker’s enclosure. 

Proper air space is essential to your speakers’ audio quality. 

Improper air space just takes away all the potential your subwoofer has from you, not to mention that it can also lead to breakage. 

So the whole idea here is to get the exact amount of air space your model needs. Both insufficient and excessive air space is not suggested; while some claim that these can either increase or decrease bass from your car audio, it’s better to play things safely.

Knowing these beforehand will help in the accuracy of solving for your 6×9 speakers’ box dimensions.

The Formula For The Proper 6×9 Speakers’ Box Dimensions

Before we get started, check first if the speakers you bought came with a user manual that includes instructions on building the subwoofer box. 

If these dimensions aren’t specifically given, then we can proceed. But if it is, follow it regardless of the circumstance.

You may think that unequal dimensions are harder to compute. But here’s how this guide comes into play, we’ve got a hack on computing how much airspace do 6×9 speakers need.

All you have to do is determine the enclosure dimensions (HxWxD), multiply them with each other, and divide the product by “1728”.

This hack works on any speaker of all sizes and dimensions. 

Let’s expand on this:

Step 1: Checking

If you’ve just recently purchased your speakers, you can still search for its user manual (if there are any) and check if there are provided volume requirements for the enclosure.

If you can’t find your manual anymore, you can look for it online by using the speaker’s brand as your keyword.

If you can’t find it, or there isn’t any, then you can proceed with this guide.

Step 2: Measuring

Check out all the possible subwoofer enclosure designs for your speaker, the simplest one is a cube.

In order to determine the volume for this sealed box, you first have to measure the dimensions of your speaker. Specifically its height, width, and depth.

In measuring, make sure to use the best possible unit; in this case, inches. 

You may remeasure multiple times to check the accuracy of your measuring tool and once you’ve finally set on a certain dimension, write it down.

Step 3: Multiplying

Now it’s time to take those measurements and multiply them with each other. Follow the easy formula below:

Height x Width x Depth = n

In the basic rules of multiplication, values can be interchangeable, so you don’t really have to place them in a specific order. The formula above is only provided to remind you to place them in one equation and not solve things two at a time.

Step 4: Dividing

Now that you’ve got that value, we’ll move on to the last step of the computation.

All you have to do is take that number and divide it by the value “1728”. 

The result of this computation is the final value of the airspace your rear speakers need. Remember that this value no longer has inches as its unit but cubic feet instead. 

The Alternatives For 6×9 Speakers’ Box Dimensions

Now, some of us don’t really have the time to go through this whole process or the patience to do the math. There are two things you can do: 

You may use a 6×9 speaker box calculator, these are websites that allow you to input your speaker’s measurements and they’ll do all the solving work just for you. Easy isn’t it?

Or, if the solving process isn’t the only thing you’re not into doing, then you may bring your speakers to a professional and have them build the subwoofer enclosure for you. 

This is an ideal option as it allows you to save time, avoid mistakes and risks, protect your speaker wire, customize your sealed box, and more importantly, know how much it costs to install a sound system in a car!

Frequently Asked Questions

What happens when rear speakers are placed in a box with the wrong dimensions?

Finding the proper dimension for your subwoofer box is a little bit tricky, but very crucial, and here’s why. Too much airspace will directly target your speaker’s limits. As the size of the sealed enclosure increases, the quicker it will be for your speaker to reach its mechanical limits.

On the other hand, too little airspace can lead to your speaker unloading or producing port noise sound. So placing your subs in a box with the wrong dimensions obviously won’t give you the best car audio and sound quality.

Does a bigger ported box provide more bass?

No, not really. Remember that the size of the ported box is proportional to the intensity of the hit. So, the bigger the box, the lower they’ll hit. If ever you try to get a box that’s way too big, it won’t provide more bass but ruin the sound quality instead.

Your 6 by 9 speaker box dimensions must be exact and precise to avoid these risks and produce the best possible sound all the time.

Can two speakers be placed in the same box?

Yes. There wouldn’t be much of a problem or a difference if both speakers are the same, are connected to one input, and shared the same signal. Let’s say both speakers are in a two cubic feet sealed enclosure. They will share the airspace available .and operate as if they are in two separate cubic boxes.


Now that you’ve figured out the proper 6×9 speaker box measurements, it’s time for you to actually make your sub-box and test its sound quality on your rear deck!

If your speakers come with a user manual that instructs you to build the ported enclosure differently, follow that instead. Some speakers are manufactured differently from most models. 

Remember to use the proper materials and never opt for unsafe measures just to save money or time. The surer, the better.

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