Magic enclosure volume that gives your subwoofer a deep bass extension!

We all love bass and bass provides completeness to the music.

First some basics about bass.

The bass frequencies usually lie in the range 20-250 hz filtered using low pass subwoofer filter. Woofer and subwoofers are used to produce these frequencies.

Subwoofers are a category of speakers that produce very low frequencies in the range 20-80 hz or sometimes till 120hz. Subwoofers are the one that produce deep bass.

Just as designing a speaker needs working out encolsure volume using t/s parameters, subwoofers also need some work on calculating the enclosure volume using t/s parameters.

Some subwoofers may not have these t/s parameters in their manufacturer specification sheet.

In such cases the following table comes in handy.

Speaker Size	Subwoofer crossover @ 120hz		Subwoofer crossover @ 120hz		Subwoofer crossover @ 80hz		Subwoofer crossover @ 80hz
Inches	Cu.feet	Cu.inch	Cu.feet	Cu.inch	Cu.feet	Cu.inch	Cu.feet	Cu.inch
5.25	0.26
6.5	0.32	552.96
8	0.395	682.56	1.58	2730.34	0.89	1537.92
10	0.498	860.544	1.99	3438.2	1.12	1935.36
12			2.39	4129.92	1.349	2331.072	5.365	9270.72
15			3	5184			6.72	11612.16
18			3.6	6220.8			8.1	13996.8

Note: The above dimension works great for sealed enclosures only. Make sure you add extra volume depending on the size of the speaker magnet and side wall damping.

Tricks to choose crossover frequency and subwoofer driver resonance selection

• For a 120 hz crossover frequency, go for a driver with fs (driver resonance) around 28-35hz or 15hz.
• For a 80hz crossover frequency, go for a driver with fs around 17-23hz.
• For subwoofer diameter below 8 inches go for a 120hz crossover frequency and driver fs around 40-45hz.

The fs i mean here is the free air resonance.

The above two tricks can make your subwoofer sound more attractive with good transient response. Swaping the crossover freqency and driver resonance may cause peaks and dips in the transient response.