Box size and power handling

[Cj Kumz]

Hey mates. Okey we all know a smaller box equals more power handling and bigger boxes means less power handling. Now question is when they recommend an optimum box size say 4ft3 for a 15'' 2000rms sub, does this mean if you go less than 4 cubes to get APPROXIMATELY the same performance with a bigger box but with less power (e.g 1500rms on 5ft3) or smaller (e.g 2500rms on 3.5ft3)??

[youngbass98]

It depends on what the sub is rated at not in general size of the sub

[Triticum Agricolam]

It's not that simple. Ported boxes increase output around the tuning frequency. The larger the box the more boost you get, but only over a limited frequency range.

[Krakin]

You also need to know the difference between mechanical and thermal power handling. Increasing a box size will lower MECHANICAL handling, yet no matter the box size the thermal handling of a coil stays relatively close to each other.

[Cj Kumz]

Ok so the box size is to do with the mechanical handling and not the thermal power handling right. I just wanted to know if I was safe running 2000 rms on my DD 9515 in 5.5ft3 box. I should be ok??

[Triticum Agricolam]

Right, the box restricts cone movement, thus making it harder to reach the mechanical limit of the sub. The size/design of the box determines just how much and at what frequencies it will restrict cone movement. The larger the box, the less restriction.

[Cj Kumz]

Right, the box restricts cone movement, thus making it harder to reach the mechanical limit of the sub. The size/design of the box determines just how much and at what frequencies it will restrict cone movement. The larger the box, the less restriction.

So low frequencies are better off in a smaller box due to higher excursion. Thanks a lot I think I have got the hung of it

[Triticum Agricolam]

So low frequencies are better off in a smaller box due to higher excursion. Thanks a lot I think I have got the hung of it

No, you are going to have less low output in a smaller box. The port is what gives you your low end boost in output, by making the box smaller you are going to have less boost. Also in ported boxes higher excursion does not = more output. At the tuning frequency you are going to have very little cone movement, but your output can be the highest, depending on the design of the box.

Here is a picture to help illustrate what I'm talking about:

The green line is a 9515 in a large (8 cube) box, and the yellow in a 9515 in a small (3 cube) box. Both are tuned to 32 Hz. As you can see the size of the box just increases the amount of boost you get around tuning. Above 50 Hz there is no difference since all the output is from the cone at those frequencies and above.

With ported boxes you have to decide what you are trying to accomplish. If all you care about is getting loud at a limited range of frequencies then you tune the box to that frequency and make it as big as you can fit. But if you care about how it sounds on music and want to have even sounding bass there definitely is a "right" size and tuning.