Better sound with various sub sizes?

[Junglist]

Since subs range from 8 inch to 18 inch or whatever, will you get a better sound having, say, an 8 inch AND a 14 inch for example, or some other combination? Or would one 12 inch be better? If two different sizes are better than one, what would the best combo be? What's the benefit of a twin sub setup with two identical subs? I've seen that a lot.

As a side note, my head unit has a setting for mono or stereo on the sub but I thought bass wasn't directional.

[bengould]

As a side note, my head unit has a setting for mono or stereo on the sub but I thought bass wasn't directional

Will be because the Left and Right channels of a song are slightly different, This feature will combine the signal at the head unit so both "halves" of the RCA lead get the same signal and therefore both "halves" of the amp channel get the same signal. Bridging the output does kind of the same job, but done at the headunit will probably give a "slight" improvement in sound quality.

Can't give much advice on sizes, I just went for the theory that two 12" would probably do. .

[fonzooorooo]

Bass is effectively not directional - but with digital media, there's no reason not to record it panned left or right. (Heavy bass recorded panned hard left/right makes the needle skip on vinyl, so it became the norm in studios to pan it all to the centre.)The harmonic content of the note is then also panned. A left and right sub is therefore technically correct... but you'll probably never hear the difference!

Sizes of driver:
It's all about the amount of air that's shifted by the driver. That and the resonant frequency.
There are myths floating about relating to the "speed" of bass delivery being "slower" from larger drivers... but it's proven there's no truth in that!

There are also practicality issues... an 18" needs a huge box... as do 2x15"s etc...

To use the ends of the spectrum to explain: For the same input level, assuming the same excursion of the cone of the driver, an 18" will shift more air than an 8"... To move the same amount of air the 8" needs to have a much greater excursion.
The frequency response of larger drivers tends to have a lower high end, so the harmonic content they deliver is more limited... BUT... this is completely irrelevant in a true sub, as it's being crossed over so low, and generally on a steep crossover.

A lower resonant frequency in the driver means that given a siilarly designed cabinet for large and small drivers, a larger driver will be able to play lower.

In practice, the decision is more about how loud the system is to play... If it needs to go massively loud, 15"s, 18"s, or pairs/quads of 12"s (additional 10 Hz of LF extension for each doubling of the number of drivers) is the only way... Trying ot use a single 8" or similar would require a HUGE driver excursion.

That help?

[Nate]

as an aside: i have been meaning to experiment making a sub using small speakers. the idea is that you wire up a large array of small (<4") speakers and they give the equivalent area of cone as one (or more) larger speakers, whilst in theory giving better response as the cones can move faster due to their small mass. i got the idea from a pair of old column speakers i used to own, that had twelve 6" drivers in each. i've never been quite bored enough to try it though

[Junglist]

Very interesting (if you're a geek, which I am). What I was essentially wondering though was, since Larger drivers deal with lows better and smaller ones slightly higher frequencies, would the sound improve if I swapped my 10 inch for an 8 and a 12 for example? Or would the 8 be wasted and just replacing it with a 12 makes more sense? I'm getting a 12 anyway as it's in a box that's been calculated specifically for it whereas my 10 is just in an off-the-shelf jobby.

[fonzooorooo]

Very interesting (if you're a geek, which I am). What I was essentially wondering though was, since Larger drivers deal with lows better and smaller ones slightly higher frequencies, would the sound improve if I swapped my 10 inch for an 8 and a 12 for example? Or would the 8 be wasted and just replacing it with a 12 makes more sense? I'm getting a 12 anyway as it's in a box that's been calculated specifically for it whereas my 10 is just in an off-the-shelf jobby.

If you're crossing over at 90 or so Hz, the 8"'d be a waste of time. Using 6 1/2"s or 8"s as bass mids would be more useful, as the response would be more accutare down to the 90 Hz crossover point.
Unless you were thinking of a 4 way system, using the 8" between 80 and 150 Hz? You'd start to notice the directionality of the bass by the top end of that pitch range though... hence why you wouldn't cross the 12" over at 150 Hz (The response could still be flat up to there, depending on box design)

[fonzooorooo]

as an aside: i have been meaning to experiment making a sub using small speakers. the idea is that you wire up a large array of small (<4") speakers and they give the equivalent area of cone as one (or more) larger speakers, whilst in theory giving better response as the cones can move faster due to their small mass. i got the idea from a pair of old column speakers i used to own, that had twelve 6" drivers in each. i've never been quite bored enough to try it though

Works for Bose... and apparenty the Phil Jones bass instrument cabs are good too, which use the same concept.
If the Fs of the 4" is 80 Hz or so (it often is somewhere up there), a pair would drop that to 70 Hz, 4 to 60 Hz, 8 to 50 Hz, 16 to 40 Hz, and if you wanted true sub bass, you'd be looking at 32 drivers to get down to 30 Hz. Though there's nothing to stop that being in an isobaric cab. .... and using drivers with a lower Fs would mean you'd need fewer multiples... You know you want to!

[Nate]

as an aside: i have been meaning to experiment making a sub using small speakers. the idea is that you wire up a large array of small (<4") speakers and they give the equivalent area of cone as one (or more) larger speakers, whilst in theory giving better response as the cones can move faster due to their small mass. i got the idea from a pair of old column speakers i used to own, that had twelve 6" drivers in each. i've never been quite bored enough to try it though

Works for Bose... and apparenty the Phil Jones bass instrument cabs are good too, which use the same concept.
If the Fs of the 4" is 80 Hz or so (it often is somewhere up there), a pair would drop that to 70 Hz, 4 to 60 Hz, 8 to 50 Hz, 16 to 40 Hz, and if you wanted true sub bass, you'd be looking at 32 drivers to get down to 30 Hz. Though there's nothing to stop that being in an isobaric cab. .... and using drivers with a lower Fs would mean you'd need fewer multiples... You know you want to!

where the idea started was from wondering if you could get a decent sound from something like this http://www.maplin.co.uk/miniature-loudspeakers-3273 and i was thinking probably using 64 or 128 of them in a single enclosure. i figure you should be able to make a full range cab with no crossover needed. obviously this theory was based heavily on beer