What is the main difference between a subwoofer and a woofer ?
Does it have to do with the box ?

Think of a subwoofer as a woofer in a box with an adjustable crossover. Put that woofer in a speaker with a fixed crossover and you have a woofer in a loudspeaker.

Also, the point of a true home theatre subwoofer is to play LFE -- Low Frequency Effects. Not so much for sound, but to cause the room to rumble with an explosion, for example. Generally, woofers found in satellite speakers, paired with a tweeter, don't play frequencies this low.

The box has a lot to do with it, yes, as the shape of a subwoofer is meant to amplify the bass acoustically, although floorstanding speakers tend to have similar designs as well, afaik.

Basically they are the same but what do you mean when you say adjustable crossover ?

Let's look at this in terms of the language. "Sub" means below or beneath. Then a sub-woofer would seemingly be a woofer below or beneath the "woofer." How could that be?? By reproducing sounds of a lower Herz. This is indeed the fact.

Lets take a small example, suppose I have two woofers of same ratings, one I decide to built inside a box togheter with a midrange and a tweeter, whilst the other woofer I would be putting it alone in a box (subwoofer)

Finally the two woofers produce same sound but eventually low frequencies would be in favour since an adittional (subwoofer) is present.

Correct me if i'm wrong.

What isn't clear to me is that a subwoofer would have an adjustable croosover whilst the other woofer would have a fixed one ?

Can you explain this better ?

It was always my understanding that a subwoofer was supposed to reproduce frequencies below what a standard woofer could normally handle. I would suppose that would mean anything below about 20hz.

I'm not sure if it is this way in practice.

You can think of a crossover as a lowpass / highpass. If you have a regular speaker, with a woofer and a tweeter, there is a crossover in there that forces all frequencies below the crossover point to the woofer, and all frequencies higher than the crossover go to the tweeter.

Some subwoofers allow you to connect all your speakers to it, and the subwoofer sends the speakers all the frequencies above its crossover point. If you're not connecting your speakers, the subwoofer simply plays frequencies below the crossover, and ignores the rest. Subwoofers also include a knob to adjust the crossover frequency, so you can set which frequencies will be played by the subwoofer. You might also be able to adjust the subwoofer crossover on your receiver.

This is what is meant by an adjustable crossover. You can adjust the frequencies it plays. In a regular speaker, the crossover is set at the factory, and is not adjustable.

Basically, a woofer is able to reproduce bass and a subwoofer is able to reproduce subbass. It seems obvious but with what I red in this topic...
Actually, a woofer in a loudspeaker is able to go down properly to around 45hz and not 20 hz as mentioned indybrett above. In fact, 20 hz is very low and I don’t know a sub able to go really down to 20 hz (except genelec).
Below 45 hz, the woofer and the amplifier isn’t enough, especially with a LFE signal.
That’s why we need a sub. A sub ain’t a woofer in a separate box. First, the size of the sub is generally bigger than a woofer because you need more surfaces to reproduce subbass. Second, the power needed for subbass is bigger than for the others frequencies. Therefore, a subwoofer needs a cross and a separate amplifier. The great advantage is to relief the traditional circuit (amp+speakers) from the most demanding signal (subbass).

What advantages would you have by adjusting the frequency ?

Have looked at this http://www.mandalaynet.com/newpits1250s.html
this woofer is able to get down to 20 hz obviously it may be used as a subwoofer if you decide to.



If a woofer isn't able to reach a very low frequency will it distort ?

A woofer able to get down to 20 hz isn't suffiscient.
Is it still at 0 db at this frequency? Probably not.
Is it able to fill the room and therefore to be feeled (you don't really hear at this frequency)?

In the best case, you have a roll off so you won’t hear the subbass, otherwise it will be distorted and if it not used separately, it will pump and distort the upper range.

If this is insufficient then give me the adequate subwoofer (woofer)

Thanks

What's your budget?

1000$ max

A woofer is a low frequency drive unit in a speaker system. The designer of the system knows (we hope!) what the optimum crossover frequency is, so it's fixed in the speaker system's internal crossover.

A subwoofer, as a separate low frequency device, is likely to be coupled with a range of differing speaker systems. The optimum crossover frequency (and slope) that achieves the most seamless integration varies depending on the speaker system the subwoofer is being used with. Hence the need for the crossover characteristics of the subwoofer to be adjustable.

Do you mean that a subwoofer is capable of adjusting its own frequency, thus increasing more power and clearance. A fixed woofer together with a tweeter and midrange would have a fixed frequency for each device (tweeter etc).

Is this right ?

Not exactly. The subwoofer doesn't adjust it's own frequency. You can adjust the frequency using a knob on the unit. The subwoofer has no way of knowing the audio characteristics of a speaker that it is usually not even connected to.

You should find infos on the following forum. This is the part dedicated to sub:
http://www.avforums.com/forums/forumdisplay.php?f=127
Cheers

What do you mean by this ?

A subwoofer is a speaker in a box where the design is optimized for the frequency range below that of a normal woofer, or with some range of overlap. Making low frequencies is hard work, with just the signal below 100 hz taking about half the power. Sending that signal to a subwoofer with a separate power amp relieves the main system and often greatly improves the sound overal.

If you want a 1k$ sub, get an SVS PB12-ISD/2. I've got its bigger brother, the PB12-Plus/2, and it's phenominal. I can get bass hits of over 120dB's during the 'heartbeat' scene in Return Of The King. Also, I've got my sub to output about 110dB at 16hz =]

SVS makes some monster subs, both in terms of output and size, so be aware of how large they are before you get it. the PB12plus/2 weighs in at 140lbs.

http://www.svsubwoofers.com/subs_pb12_isd_2.htm

I would think you'd be hard pressed to find a sub with greater output and linearity at that price.

If one is willing to design/assemble their own subwoofer, they could exceed the commercially available equipment in performance of an equivalent cost.

-Chris

The subwoofer frequency crossover on better units is adjustable so that the sub can compliment the woofer built into the speaker. Speaker internal crossovers are usually fixed these days.

I think there is a lot of misinformation in this thread in a few respects.. The woofer built into a speaker will frequently begin to roll offf arounf 40hz, ie drop below -3db. It depends on the design a bit, whether bass reflex or ported, but more on the internal volume of the speaker.

So if your speaker is rolling off 3db at 40hz,you should set your sub to start kicking in at that
same rolloff point.

For a subwoofer to reach 20 hz it will require a substantial box size to prevent bass doubling,and this is frequently impractical in a bookshelf system so an outboard component is required.

Beware of speakers that claim low bass performance in a bookshelf or small volume system. The designers are forced to make compromises that destroy the quality of the bass.

Anyone who has heard a good subwoofer will understand this immediately.

If you want to check out a decent sub for under a grand Canadian, look at the Paradigm PS 1000 or PS 1200. Very powerful and controlled.

But what is the reason that a speakers's crossover is fixed and the (seperate) subwoofer's crossover is adjustable ?

I don't know for sure. I am guessing that it is to provide optimal performance for driver and box combination.

When I was selling stereo stuff,there were still lots of people around that put a lot of stock in big boomy bass.

Good monitors now make no attempt to do this and roll off around 45hz. Its almost as if they are expecting a sub to be purchased as well.

Sorry I don't have a better answer.

WmAx: If you can design a sub that can beat that for linearity, otuput, and behavior [amp runs outta juice before the woofer can bottom, so it's basically unbreakable] for 400$, I'd like to see that. I'm sure you can get more output, but the other two, I'm not too sure on. Be sure and factor in your construction time in the cost, and also make sure that it looks at least as nice.


=]

I know DIY has its places, but for 400$, this is a damn great sub, and a shit-ton load easier and nicer looking.

There are usually 2 adjustments for subs
1. Level/volume
2. Xover frequency
IMHO these are provided to give (at the listening position)
1. In-phase response at the frequency where the sub roll-off meets the main speaker rolls-off
2. Minimise interference ( eg ripple/combing) effects.

The effective bass-response of the main unit is difficult to control in a room, so the sub is provided with adjustment to match the lf of the main. In practise the 2 adjustments are used to give the smoothest response possible at the listening position.

A sub which provides high-pass output for the main speaker is preferred because the response should be better controlled & the main doesn't have to work in the range of the sub (theoritically lower distortion).

rgds

In simple words you mean that the small control panel present on most active subs uses an adjustable crossover to change settings depending the room and music type right, whilst other woofers built toghether with tweeters etc have a fixed crossover which may not be set.

Correct me if i'm wrong.

1. Yes : adjust for room & main speaker
2. No : music type is not involved

With music type I meant that if you were looking to play techno you would defenetly want to appreciate that deep bass involved thus increasing the subwoofer's volume (crossover). On the other hand if you were to listen to just some classic music you would only need little bass but more clean treble.