A subwoofer, yesterday
Do I need a subwoofer? This is a question that I have read again and again on AV related forums. It is so common that I thought I'd answer this question once and for all so that anyone who asks can learn whether they do and if so, why!
Usually this question is asked by people that have a surround sound system with powerful bookshelf or large floorstanding speakers. The speakers they have are powerful and produce a lot of bass, so adding a subwoofer doesn't really seem necessary.
However subwoofers aren't just about adding louder bass, or more volume. If your sound system is calibrated correctly, they will complement the rest of the system, without overwhelming anything, providing the lower bass your speakers simply cannot produce.
I have floorstanding speakers. Why would I need a subwoofer?
If you have large floorstanding speakers then you will have speakers that can produce some power. The thing is though, the vast majority of speakers are capable of playing loud bass, but they simply don't reproduce the lowest frequencies that are in a soundtrack or a music track.
We can hear from 20hz up to 20khz. If we take a film soundtrack, then there is a dedicated channel, called the LFE (Low Frequency Effects) channel. This channel is what the subwoofer reproduces. If you don't have a subwoofer, your system will do its best by directing all of the bass to the main speakers. The LFE channel has information in there from about 5hz upwards, all the way up to 120hz. The majority of the action is found in the 20-80hz range, although there is some to be found either side of this in most soundtracks.
This frequency range is where the powerful bass action is. This includes effects such as earthquakes, car doors slamming, guns firing, explosions etc etc. Now to get the full effect from this, which is what you deserve really after buying the film, you need a speaker that is capable of reproducing it. Now even large floorstanding speakers are not capable of reproducing bass anywhere near the 20hz level, never mind below that. Lets take an expensive and very large speaker as an example. This is one I plucked at random from a well regarded manufacturer, Polk. Their flagship LSiM speaker costs $1,999.95 each at time of writing and is by most people's reckoning an expensive and good quality speaker.
Do you need a subwoofer with a pair of these?
Now this big titan of a speaker obviously a good performer. However, even something like this has its limitations. If you look at the tech specs to see what frequency range it can reproduce down to, so the real low stuff, you see that it's -3db point is 38hz. This is the point where the speakers ability to reproduce frequencies below that point start to roll off. The output level of anything below that will be very limited, which will mean that you'll be missing out on the action below that level. These are particularly good speakers remember anyway, your average home speaker, won't perform as well as these do in the low range and even these you can see still aren't able to reproduce really low bass.
Now when you use a subwoofer in conjunction with these, you have the capability to play bass frequencies all the way down to 15-20hz, sometimes lower if it's a really good subwoofer. This allows you to really experience the soundtrack and get the really low bass extension that speakers just can't give you. You also take the strain off the speakers. There is a lot of power expended reproducing the low frequencies, if the speakers have to try to play those as well as bass higher up the range, the sound is never as clean as it is if you take the low bass chore away from the speakers and let the subwoofer take the strain. This gives a better quality sound from the unstressed speakers. The overall effect is a far better sound quality and also one that really gives you some oomph whenever something powerful happens on screen.
So the answer to the question, do you need a subwoofer even though you already have good speakers?
Yes, you do!
If you have any comments, please leave them below.
Thanks for reading.
Rain Defence (author) from UK on June 26, 2014:
I think I get what you're saying, if what you're saying is 'bigger is better' and I agree.
yo on June 23, 2014:
for large speakers you must go to bigger sub or more mutiple subs to make lower frenquency than speakers and somethin to separate the frequency on 20 30hz
Jason R. Manning from Sacramento, California on April 09, 2012:
Nice Job on the hub, great picture of those Polks. Have you seen the latest version from the big man behind Polk Audio and Definitive Technology? The GoldenEar Tritons...pretty neat gear. Though, if they can hit 18hz, then you really don't need a separate sub. Cheers mate.
galaxy1 from Spain on February 08, 2012:
This hub doesn't really say anything and I can't see it helping anyone out in any way.