Hand Made Skin Drum

Tube enclosures are very efficient enclosures for bass creation and subwoofer applications. If you think about it, tribes used to use hollow logs and tube shapes to create their ancient drums. To this day, with advanced technology, acoustic modeling, and ‘if you can dream it , we can build it’ machining, we still have circular drums. Think about it, have you ever seen a square bass drum before ?

Now there are two reasons that a tube is very efficient at creating and amplifying bass frequencies:

1. A tube matched to the size of the drum surface (the drum skin) or in our case to the size of the subwoofer has it’s entire surface area in contact with the subwoofer surface.

So, any motion in the subwoofer, moves the entire air column in the tube, this is unlike a square shaped enclosure that allows for stagnant air to be trapped or turbulent in the corners of the subwoofer enclosure, a phenomenon that can create enclosure noise and bass distortion.

2. In a tube shaped enclosure, no two surfaces are parallel to each other except for the tube end plates (one of which has the subwoofer mounted to it). This prevents any standing waves of any frequency to exist inside the enclosure and is the primary reason a tube system requires less power (is more efficient) to create more base.If the enclosure were to resonate internally due to the parallel faces creating standing waves, then the subwoofer would have to overcome the pressure of these standing waves to create it’s own pressure waves in accordance with the music. This energy is wasted by the subwoofer and requires a higher power amplifier to create the same level of loudness.

If you’ve seen certain subwoofer boxes that are fairly deep (deep enough to create audible internal standing waves) you’ll find the front panel of the subwoofer box is mounted at an angle which prevents the same internal resonance phenomenon from occurring in a typical box enclosure.

Now here’s a product that takes advantage of this design:

Bazooka BTA 8100

The bazooka BTA8100 stands for Bass Tube with Amplifier 100watts. The BTA8100 uses a dual voice coil 8″ subwoofer powered by a  ’small’ two channel 100 watt RMS amplifier (also verified by the 7 amp fuse on a 14 volt system), that can peak at 200 watts momentarily to create a significant amount of bass from a very small enclosure.

The way the Bazooka bass tube creates such a big boom from a small enclosure is that it:

1. Uses a bass tube which is very power efficient
2. Focuses all of the energy on a very narrow frequency range of 35 to 85hz leaving out midbass and subsonic frequencies and focusing all the power on where most music ‘booms’ which is a pretty efficient way to add bass that most people will appreciate.
3. Uses a ported enclosure to further amplify the system response around the bass port tuned resonant frequency by 3+ db as per a typical ported system.
4. Brings the bass port all the way to the front to exit in the same plane as the subwoofer, usually a bassport tuned for a 1/4 wavelength and exiting in the same plane as the original speaker driver helps improve the subwoofer’s response in a vented or ported system to bring it closer to the response of a sealed system, while having the 3db gain advantage of the ported design.

Now we know the bass tube is 18.5″ long and so the length of the enclosure is double that (as the wave travels from the subwoofer surface, to the rear faceplate and backfowards to the port exit) of 37″. In free air, with no internal padding, at 30*C this 37″ corresponds to 1/4 of a 148″ wavelength which corresponds to a tuned frequency of 93hz which is very close to the highest cross over frequency of the 85hz low pass filter.

So the result of all of this efficiency, design and bass reflex tube tuning is an impressive 102dB sensitivity at 1W @ 1 meter.

Being a 100W RMS system, this system is best used in an open cabin such as in a hatchback or behind the rear seats of a Jeep. This allows the bass to travel easier into the compartment than it would if the system was installed in a sealed trunk in a sedan.

One thing Bazooka recommends to improve further improve how hard the system hits is to ‘corner load’ the subwoofer by installing the subwoofer (and the bass port) in a way where it is playing into the corner of the rear hatch or trunk area about 3″ to 5″ from the walls. Typically a subwoofer is rated (to 102dB in our example) by placing it in an open space and measuring it’s sound pressure, using 1 watt of power, with the microphone or pressure meter 1 meter away. This arrangement allows the subwoofer to play bass in all directions in 360 degrees of space.

Corner loading reflects half to 3 quarters of the sound wave to play in the opposite direction giving a bass boost.

By corner loading a subwoofer (and placing it in the corner), half of the audio is played out into space while the other half is reflected off of the wall (the corner) and played into the SAME space. What this does is that it allows both halves of the sound (the primary wave and the reflected wave) to stack up on top of each other giving between 6 and 12dB of additional bass gain using corner loading and room gain.

So what is the best application for this bass tube?

Because of how well the Bazooka tube is designed you will typically find TWO types of reviews on the internet for it:

1. WE HATE IT!

   The reason some people hate the bazooka tube is that it does not perform like a larger 15″ subwoofer in a 3 cubic foot enclosure. The bazooka tube does not play subsonic bass (typical of some genres of music) nor does it play good midbass in the 125 to 500hz region. So people that buy the Bazooka tube with the expectation that it is the same as having a full custom subwoofer box in their trunk, that they will be able to rattle the doors off of their car, or that they will be able to rumble the guy next to them at the stop light with 16 hz subsonic frequencies will be dissapointed.

2. WE LOVE IT!

   The people that love the Bazooka tube love that it is portable and easy to install and remove. Think of a Jeep Wrangler owner that loves to take his car apart, take the top off, remove the doors, take it in the mud, have a bass tube in the back that you can install and uninstall in no time. Have a plastic bass tube that isn’t carpeted that you can get wet or muddied (Bazooka even sells marine bass tubes that you really don’t have to worry about with water , rain and the elements).

   Or maybe you have a sound system that is completely flat on the low end and has no bass what so ever ? You want a quick , cheap, and very effective solution at adding some boom to your ride. Enough boom to be noticeable, to dramatically increase your enjoyment and your listening experience and something that your passangers will defiantely notice. At the same time you’re not looking to shatter glass, break any SPL competition records, or have your bass heard anywhere OUTSIDE of your cabin.If you’re this kind of person, you will love the bass tube, as it compliments your factory speaker arrangement (which typically does well for midbass, midrange and treble if you already have high quality speakers in there), and it will fill out the missing POWER in your music.

Here’s a great video of a larger application of a tube subwoofer

It’s really important to understand how a product works, and what it’s designed for, to get the most out of it and to know what to expect with it …

Note: Click here to get your Bazooka Subwoofer Tube and get $70.00 off!

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