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Product Review - AudioSource SW Twelve Subwoofer - July, 1997

By John E. Johnson, Jr.

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AudioSource SW Twelve Subwoofer; Vented box design; One 12" front firing driver, 4 Ohms impedance; Three front 3" ports; 150 watt amplifier with controls on back of enclosure; On/off/auto; Phase shift 00 - 1800 (not variable in between); Variable low pass frequency 40 Hz - 180 Hz; Right/left line level in, right/left line level out (high pass); Right/left speaker level in (spring clips), right/left speaker level out (high pass); Size 16"H x 17"W x 17"D; Weight 36 pounds; Black vinyl finish; $499; AudioSource, Inc., 1327 North Carolan Avenue, Burlingame, California 94010; Phone 415-348-8114; Fax 415-348-8083.

Readers have been asking us to review some modest-priced subwoofers that do the job, so read on to see if the AudioSource SW Twelve could be a "Secrets Recommended" product.

At $499, the Twelve is modestly priced - well within the reach of anyone who needs a subwoofer. And who doesn't!?

The Twelve uses a 12" front-firing driver (with a cup-shaped dust cap - very popular in many low-frequency driver designs these days), and alongside, are three 3" ports. This is rather unique, and it works very well. We could hear none of the vent noise ("chuffing") that occurs with some designs using only one port. Port noise is not really a serious issue, since the main output is so much louder than the noise. But, with the SW Twelve, it is non-existent. The damping material inside the box is kept from coming out of the ports with a small plastic grille covering the rear of each port tube. The grille cloth is stretched over a plastic frame and bowed outward so it will not flap against the enclosure. Another reason that there is no vent noise, is that the Twelve has a sharp dropoff in output below 30 Hz, with a 1 meter test distance and moderate volume setting, and the main output appears to begin at around 40 Hz (see frequency response test below). This is a good idea for a modest subwoofer, since movie sound tracks are designed with low frequency attenuation below about 40 Hz. So, the amplifier concentrates its power delivery where it counts.

We tested the AudioSource SW Twelve with our most potent sound tracks in an AC-3 surround sound system: Toshiba 3006 DVD Player, Yamaha DDP-1 AC-3 Decoder, Yamaha RX-V990 Receiver, Carver AV-705 Power Amplifier, Nordost Cables, Krix Speakers.

Probably 99% of the movies coming out these days have a thunder and lightning storm. "Turbulence" has a storm that a 747 flies right through. "Mars Atacks" has plenty of crashes and booms to test any sub. The Twelve performed admirably. Of course, it does not match the output of the "Big Guys" we have on hand, such as the 15" and 18" units. But it is not supposed to. Our reference subwoofers are all between $1,200 and $2,500. The point is, the Twelve did not break up or sound boomy. In fact, even at full output (the volume control turned all the way up), we could not hear any hard clipping (shutdown or crackle). It is quite an interesting design, since we have been able to get almost every sub we have ever tested to clip hard when turned all the way up, but that is with 20 Hz sine waves. This shows how much amplifier power is required for the really low frequencies. The output at 20 Hz - 25 Hz from a distance of 13 feet to the AudioSource Twelve is probably represented by room gain. We had to turn the sub up to full output in order to achieve 95 dB at 40 Hz with this distance, and audible harmonics were apparent. Diverting mid and deep bass from the mains to the sub can help their amplifiers perform more efficiently too.

Although the Twelve can be set to a crossover of 180 Hz, we usually prefer to set subwoofers at 40 Hz - 70 Hz, depending on the other speakers in the system. This subwoofer is really designed for use with small satellite speakers that begin to drop off below about 80 Hz. In this case, one would set the crossover at about 60 Hz to allow for overlap above this point with the slope below 80 Hz of the satellite speakers. The Twelve is not really for use with full range speakers, such as our Krix Esoterix, which have an 8" woofer in each floor standing enclosure. The Krix respond as deep as the AudioSource Subwoofer. The Twelve added some impact to the overall sound with these speakers, but no further depth. However, when we switched in our AudioControl Rialto Equalizer, to filter the < 90 Hz from the mains, the sub added the necessary low end, and at sufficient volume to satisfy us as movie watchers.

Frequency Response (Room Response), 1 meter, on-axis, grille cloth removed, volume set to 95 dB at 40 Hz, low pass set to 180 Hz :

10 Hz - 0
12.5 Hz - 0
16 Hz - 59.4 dB
20 Hz - 67.0 dB
25 Hz - 67.6 dB
31.5 Hz - 84.7 dB
40 Hz - 95.2 dB
50 Hz - 100.1 dB
63 Hz - 100.9 dB
80 Hz - 101.6 dB
100 Hz - 101.1 dB
125 Hz - 95.0 dB
160 Hz - 95.9 dB

Frequency Response (Room Response), 13 feet, on-axis, grille cloth removed, volume set to 95 dB at 40 Hz, low pass set to 180 Hz:

10 Hz - 59.3 dB
12.5 Hz - 62.9 dB
16 Hz - 67.9 dB
20 Hz - 79.5 dB
25 Hz - 83.6 dB
31.5 Hz - 86.6 dB
40 Hz - 94.8 dB
50 Hz - 94.9 dB
63 Hz - 107.0 dB
80 Hz - 102.7 dB
100 Hz - 101.6 dB
125 Hz - 95.9 dB
160 Hz - 100.3 dB

As you can see, the output falls off sharply below 31.5 Hz with the volume set to achieve 95 dB at 40 Hz and 1 meter to the microphone. The subwoofer plays very loud, but part if this is due to harmonic distortion. Such distortion is not all that objectionable with subwoofers, in fact, far less so than the boominess produced by setting the crossover frequency too high.

So, is the AudioSource Twelve a good performer? Yes, as long as you understand it is built with a specific purpose in mind. It is not made to shake the rafters with 20 Hz thunder or T-Rex foot stomps. But for adding the low frequencies present in most sound tracks, and which would otherwise be missing from a small satellite surround sound speaker system, it is a winner.

John E. Johnson, Jr.
Editor


Copyright 1997 Secrets of Home Theater & High Fidelity
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