How To Buy Subwoofers

A subwoofer reproduces the audible low frequency sound. Sometimes it is called LFE (Low Frequency Effects) channel. A good subwoofer can shake you up and make you feel the sound. But a very few people bother much about the type and quality of it. Here is a checklist to pick the right one for you.

Step 1

Is it powered? The subwoofers can be passive or powered. The powered (active) subwoofer need separate power supply whereas the passive subwoofer doesn't. The passive subwoofer is driven directly by the amplifier/ AV receiver.

The sound effect of a subwoofer depends on the power delivered to it. For the passive subwoofer this power is limited to the maximum power output by the amplifier/AV receiver.

But, the case is different for the powered one. The powered subwoofer typically has a built-in amplifier and can deliver better sound effect as it draws enough power from external power supply and does not draw much power from the amplifier/receiver. It has another advantage also. The amplifier can deliver most of its power to other speakers as it doesn't have to deliver much power to the subwoofer. Hence the powered subwoofer is the better option.

Step 2

Does it contain a port or radiator? Some subwoofers contain an additional port that gives better bass response than a completely sealed enclosure. Some other subwoofers do not contain a port but have a passive radiator. This passive radiator in addition to the speaker improves the precision of sound.

Step 3

Which Size? Subwoofers are measured by the size of their drivers. They are measured in inches. The most common sizes are 8", 10", 12", 15" and 18". The less common sizes are 5.5", 7", and 20".

The 8" is the smallest of the basic sizes. 10" subwoofer is less common and available with a few amplifiers. Many 10" subwoofers cost similar to 12". 12" is probably the most common and ideal subwoofer size. 15" is more expensive than 12" subwoofers and is suited for very large halls. 15" may be big for ordinary home theaters.

If you have small surround speakers of size 4-inches, go for small 8-inch subwoofer. If you have larger surround speakers, buy a larger subwoofer with size 10- to 12-inch. 12-inch is sufficient for rooms of size less than 1500 cubic feet.

Step 4

Is it matched? Some subwoofers may not perform well with other speakers made by a different manufacturer. In that case, try to connect the matched models of the subwoofer of the same manufacturer.

Step 5

How much power rating? Do not rely on the 'dynamic' or PMPO (Peak Music Power Output or Peak Momentary Performance Output) ratings. If you want to gauge the real power capabilities, compare the 'continuous' or RMS (Root Mean Square) power ratings expressed in 'watts'.

The power level requirement varies according to the person as well as the size of the room. So choose the rated power level according to your interest and the room size where you’re going to place it. However, power rating within the range of 75-150 watts is enough for a good home theatre. The subwoofer must be able to handle the rated power level of amplifier.

Step 6

Side firing / front firing or floor firing: Side firing subwoofers have either one or multiple drivers that fire to the side. Most of them have only one large driver in the front, and a bass port in the back. As bass port is on the back, keep it near the wall or in the corner with its front facing you. It's because the bass reflects off the walls and you get a more powerful and better sounding response. It is best suited for small rooms.

Floor firing subwoofers have a driver that faces the ground. So instead of firing towards you, the subwoofer simply fires the bass towards the ground. This actually fills the whole room with nearly the same amount of bass and better blended with music from other speakers. But it needs very hard surfaces or hard wood on the floor for best performance. Carpets on floor affect the performance of this type of subwoofer.

Dual-firing subwoofers usually contain a side firing driver, and a floor firing driver. The side firing driver will blast bass directly at you, while the floor firing driver will fill the room with bass. A dual-firing subwoofer can give off superb smooth bass, but are very expensive. Sometimes it gives better response when placed directly behind your viewing area.

Step 7

Where to place it? The subwoofer can be placed anywhere in the room. However, the overall performance depends on the room size, wall finish, floor type, furnishings etc. The best place of a subwoofer is between the two front speaker pair. If there is a centre speaker, place the subwoofer to the left or right of the centre speaker. You can also place the subwoofer to the front corner of the room. Adjust the phase control on the subwoofer to get the best overall sound effect in the room.

Step 8

What is crossover frequency? It is the cut-off frequency of the subwoofer. Got it? It means that the subwoofer reproduces only sound below this crossover frequency. The sound above this frequency is delivered by other speakers in the system. Many AV receivers have internal crossover settings for your subwoofer related to the size of other speakers. It helps to split the bass load with main speakers as the subwoofer need only produce the very lowest bass frequencies. A good subwoofer has crossover frequency typically around 80 Hz. This frequency is usually set slightly above the lowest frequencies produced by the main speakers, by trial and error.

Some subwoofers have the option of selecting the cross-over frequency from a range of values. You can try different settings that suit the whole system. The manual may give you some insight on how to set the crossover for the particular subwoofer.

Avoid setting the crossover frequency too low or high. Setting it too low may create a gap between the frequencies between the subwoofer and the main speakers. Setting it high will force the subwoofer to make sounds that it is not designed to do and makes the sound filthy. If you have a big main speaker that has good bass response, then 60-80 Hz is good. If you have small speakers of size less than 8" then 80-120 Hz is better.

Step 9

Phase control: The phase control helps the sound waves coming from the subwoofer get synchronized with those from your main speakers.

Follow these simple steps to set the phase control.

  • Reverse the connections on your main speakers (connect the black wire to the red terminal and the red wire to the black terminal).
  • Be seated in your normal listening position and play some music with good bass line.
  • Get help from somebody to adjust the phase control on the subwoofer until you hear the least amount of bass.
  • Leave the phase control setting there.
  • Change the speaker connections and connect the speaker wires correctly. Now you will hearmostofthebass from your subwoofer.

If the bass frequencies from the main speakers are cancelled by that from the subwoofer, then change the phase 180 degrees to eliminate it.

If your subwoofer doesn't have a phase control, then place it very close to one the main speaker so that the sound gets synchronized.

Whether shielded: Do not keep any unshielded speaker or subwoofer near a TV of CRT type. Unshielded speaker will create a magnetic field which almost destroys TV's picture tube . If you have CRT type TV and plan to place the speakers near to it, then buy only shielded speakers.

Check before you buy. It is important to test the subwoofer and other speakers in the system before you buy. Carry some best DVDs or CDs that have a lot of bass music to test various subwoofers before choosing the right one for you.


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