bump.

 

IMHO I think it goes like this -

6.5-8 (Single Driver)

Goals: Louder in-car than out. With high travel 8" subs (Sundown) however in a small interior environment (B segment compact or pickup truck) it will be loud in and out of the car given enough wattage.

Large cars and SUV's will tend to swallow the output of smaller subs and be plenty loud inside but only noticeable if by an open window.

10-12 (Single Driver)

Goals: Frequency extension and because of just physics it will play louder in comparison to a single 8" driver.

That said, Audiophiles want to hear notes below 30 Hz. The truth is for most people there isn't much going on down there. At least not enough to give up
cargo space.

Again IMHO 10" or 12" driver in a 1.0 cubic or less sound marginally good, not ideal.

For those that listen mainly to rock without exaggerated bass (think Metallica) the high F3 will be okay to them. But if their teenager gets in and wants to hear "Snap Yo Fingers" they will walk away disappointed especially if they have good earphones, ear buds or have experienced true stereo sound with bass reflex speakers.

I say either run 10's or 12's right, don't complain about air space and power them properly and you won't be disappointed.

If you look in the Infinity/JBL 8" thread, you'll see somebody is running a couple of 8"s in the center console of his truck as mid-bass and runs larger subs for sub-bass (below 60hz).

You can also run two different sized drivers -

If your not interested in a killing people decibel level, and are more interested in awesome sound quality you can put the woofers in different size boxes. So for example say you have 4 cubic feet in total and 2 woofers, instead of putting each in a 2 cubic foot box, make one side 1 cubic foot and the other in a 3 cubic foot box, this will make the 1st woofer will better play the high pitched bass from 60 to 200 hertz, the other will better play the superdeep 20 to 50 hertz bass. This will happen automatically without any additional equalizers, crossovers or filters from your amplifiers. Your total db level will go down, but your sound quality will go way up. Even better would be to port tune the 2nd larger box from 18 to 26 hertz for that vibration bass. In general you can make 1 side from 2 times bigger or 3 times bigger than the other. So for example say you have X cubic feet in total, then the small side is X divided by 4 = (X/4) cubic feet, then the rest of the box is for the other woofer.

Source - www.makeitlouder.com

As I said running a single mid-bass driver is not unheard of, just not common as running a stereo pair and running two close together to maximize cone area.

I think localizing might become an issue, so that is something you might have to keep in mind or make sure you have a pair of mid-range drivers that play down to 100-200 Hz with some authority upfront.

 

The sound waves produced by a speaker are no different based on the size of the speaker. Saying "Large cars and SUV's will tend to swallow the output of smaller subs and be plenty loud inside but only noticeable if by an open window." is just plain false.

If the SPL is the same (whether from a 5" woofer or a 15" woofer) the vehicle won't do anything different to the sound from the smaller woofer than the larger one. Displacement dictates SPL. If an 8" driver has massive excursion and high power handling, it's very possible that it could be louder than a 15" with weak excursion and low power handling. This isn't the norm, but it's absolutely possible. If a set amount of power is available, the sensitivity of the driver should be considered.

Generally speaking, the only reason to go with a smaller woofer is because of size. You may be able to fit two 8"s (one in each corner) but only one 10". In this case, the 8"s would likely be best because they would have more displacement. If size isn't an issue and all other things are equal (which only works theoretically, a bigger driver typically has heavier parts, which change the parameters) then yes, the bigger driver will be better.

The real problem is that there is rarely a situation when "all things are equal." Power handling, total displacement, sensitivity, optimal enclosure size, and other variable will dictate which speaker is going to be best/louder.

 

There is a design trade off with speakers: Consider a speaker like a weight on a spring with a shock absorber. The cone size determines how much air it moves for a given excursion, and all else being equal, a larger cone means more air displacement means louder, however all things are rarely equal.

A few design factors:
2 main constraints:
The heavier the moving mass, the lower the resonant frequency.
The stiffer the spring, the higher the resonant frequency. Compliance is the inverse of stiffness.
Stiffer and heavier take more power to move, therefore less efficient.


Total stiffness is the combined stiffness of the speaker plus the compressibility of the air in the box. Speaker stiffness is determined by the materials of the surround and the spider. These parts also absorb energy and give the speaker damping or Mechanical Q factor. The resistance of the voice coil also absorbs energy and determines Electrical Q. Total Q or Damping is a measure of how much the speaker continues to vibrate after signal is removed. Q is often a design factor that effects sound quality such as boominess or tightness of bass. There is an optimum Q level for best sound quality.

How much a speaker can move mechanically is called excursion and is determined by the surround and spider construction as well as the length of the voice coil in the magnetic field.


Larger cone area also means making it out of a stronger material and maybe heavier that prevents physical distortion of the cone and what is called cone breakup, or a vibrating mode that is other than simply in and out. The cone is not perfectly stiff and even if it doesn't break up much the small flexing may also absorb energy and contribute to overall Q. This absorbing of energy may also help to dampen these unwanted resonance modes. Some of the best midrange speakers are still made out of paper because of their combination of strength and damping!

When you put the speaker in a sealed box you are increasing the overall spring and therefore increasing the resonant frequency. If you make a speaker very stiff to start with, then adding the box will have less effect on the total spring and therefore have a lower increase in resonant frequency. Stiffness is usually given by the Vas number. The stiffness expressed in the equivalent volume of air. The lower the stiffer.

So there are all sorts of trade offs that mean even in the same product line, a larger speaker is never just louder than its smaller brother. It will sound different!

For example: Consider the Alpine type R vs Type S.
The Type R is made to work in a smaller sealed box. This means it has a stiffer suspension. To compensate for that and keep a low resonant frequency it has to be heavier too. This means also a stronger constructed surround and spider. This affects the damping. To try to compensate for stiffer and heavier they put a larger magnet, thus more expensive. The R is also supposed to be louder overall, therefore larger excursion. this also means stronger surround and longer voice coil.
The extra power needed also means thicker voice coil wire therefore also heavier. Plus more engineering to get air moving around the voice coil to remove heat.
Extra power means more heat, which means the voice coil heats up and resistance increases...thus reducing the current, and power for the same applied voltage and therefore the force generated and also affecting the damping! This is called thermal compression!

You see. it is not simply a matter of making a speaker larger diameter to make it sound louder...

Seems like 10 or 12 inch subwoofers result in a certain sweet spot, or optimum performance.