Quantity vs. Size (Subwoofers)

[zingo]

I am interested in building a subwoofer box for my car. My issue is I do not know which design I want to go with. There is the classic design of the 2 12" (or 10"s) drivers that sounds good and are loud. But, I am interested in making a box that holds 8 6.5" drivers. I feel that with that many woofers, even though they are small, they could be loud, and hopfully pretty bassy.

The driver I found is the GOLDWOOD GW-S650/4
http://www.partsexpress.com/pe/showd...number=290-308

The driver looks like it can go deep enough and that many drivers can move a lot of air. I will be using a 1200w RF amp and I will be wiring the drivers at 4 Ohm, 2 channel in a sealed box.

Please give me your ideas on this.

[richie00boy]

Go for the two bigger drivers. It will go deeper if you pick the right drive unit and be cheaper.

[oPossum]

A pair of 12s will typically be much more efficient than 8 6s in the lowest octave (20 to 40 Hz). Probably by as much as 6 dB, so you would only need 1/4 the amp power to drive the 12s to the same SPL.

[NaftaliG]

A pair of 12s will typically be much more efficient than 8 6s in the lowest octave (20 to 40 Hz). Probably by as much as 6 dB, so you would only need 1/4 the amp power to drive the 12s to the same SPL.

I totally believe this is true, sorry if I seem like a thread jacker, but Possum, can you explain how and why that works out? Perhaps point me to something to read. Understanding this concept would be supremely helpful to me.

Thanks,
NaftaliG

[Safe_Cracker]

I believe one RE sx15 in a 4 cf ported enclosure liek the one down below would get you 150db. Polo..

[sr20dem0n]

Originally posted by NaftaliG


I totally believe this is true, sorry if I seem like a thread jacker, but Possum, can you explain how and why that works out? Perhaps point me to something to read. Understanding this concept would be supremely helpful to me.

Thanks,
NaftaliG

For a given alignment, the point where the response starts to rolloff is direcly proportional to the resonant frequency (Fs) of the sub. Without getting too in-depth, if you hold everything else constant then the Fs of the speaker will decrease as you increase moving mass (by using, say, a larger cone). Other parameters of the speaker (like the suspension) can be adjusted to counteract this drop in Fs, however this is a pretty steady trend that you'll see all over the place. A larger speaker will almost always have a lower Fs, which, by definition, will allow it to play lower before rolling off in a given alignment.


IMO it's always best to go with a single sub of the largest size you need, are willing to afford, or can give up space for. Using multiple, smaller speakers will lower the overall efficiency almost every time AND increase cost, with no added benefits (other than lots of small speakers "looks cool"). You have to buy multiple subs (costs more), you end up with similar total displacement (similar output), you need more amplifier power (costs more, hurts the car's electrical system more), and you typically sacrifice some low end. No benefits at all really...

[Una]

Originally posted by sr20dem0n

<snip>

IMO it's always best to go with a single sub of the largest size you need, are willing to afford, or can give up space for. Using multiple, smaller speakers will lower the overall efficiency almost every time AND increase cost, with no added benefits (other than lots of small speakers "looks cool"). You have to buy multiple subs (costs more), you end up with similar total displacement (similar output), you need more amplifier power (costs more, hurts the car's electrical system more), and you typically sacrifice some low end. No benefits at all really...

Im gonna have to agree.

Years ago, when I had more income then common sence, I went down the "lets use an absurd number of smaller woofers" road.
Everything said above is completely true.
To get a good response I needed a seemingly nonsensical fourth order lowpass of 30hz, insane amounts of power amp, and massive electrical upgrades because the insane power amp made the engine stall every time a 20hz note came around.
Thats not even getting into the sheer weight of so many drivers.

On the other hand, now that all thats done with, it does sound good, and looks really cool

[Ocelaris]

Just to be a devil's advocate...

Are two drivers ever more efficient than 1? Or what about using a passive radiator? Somwhere I had heard using multiple drivers increased efficiency. Is this correct in any sense? For example in an MTM bookshelf speaker?

[oPossum]

Two will be more effiecient than one when the driver size is the same. For example two 12s will be a bit more efficient than one 12 and also have a bit less distortion at the same SPL. The box must also double in size for this to be true. The efficiency of a (sub)woofer system is greatly influenced by the size of the box. Larger is more efficient - assuming proper match of driver to box. A large speaker in a too small box will not perform well. A small speaker in a very large box can be quite efficient, but it must be designed for this type of use. Most small speakers are not well suited to use in large boxes because people want large speakers in small boxes, not small speakers in large boxes.

Using passive radiators or ports allows greater efficiency in a small box, but only for a relatively narrow range of frequencies.

[Safe_Cracker]

This is only true if the surrounding spaces are unlimited. I have seen where people try to stick one too many boxes and subs into a trunk of a vehicle only to decrease efficiency. Take my car for instance, I have a 2001 Pontiac Grand Prix (GTP) I would say it is a 4 body tunk, lol now I have an RE sx15 sub in a 4 cf ported enclosure. Now I could add a second box and amp but without the proper space, because the trunk will totally be crowded the two subs will not perform as efficiently as one WITH the proper amount of space. The air actually gets trapped inside of the trunk with no way to get out so the energy is transmitted more quickly to the vehicles body panels (big waste). This is more true for trunk vehicle, that's why I envy the guys with hatch backs. Polo..