Power Handling?

[RebelDogg 10+ year member]

I was looking at Kickers web site at the manual for the CVX 12" (mine is coming in UPS Thursday) at the enclosure specs.

I noticed that the compact sealed says 1ft^3 Power Handling = 750rms; SealedSQ (Maximum Enclosure) 4.6ft^3 Power Handling = 300rms.

I have a thin grasp on this, but I don't really get it. I know it has something to do with the tuning and size of the box and how much power the sub can handle in certain frequencies... or something.

But if (for example) I went with the maximum enclosure, does that mean it's pointless to use a 750w amp? Do you only need a 300w amp? And how does the speaker draw less power from the amp just because of the box size?

Also, does the sub draw power from the amp or does the amp dictate the power to the sub? By that I mean is the amp sitting there with X watts waiting for the sub to say give me Y amount now, or does the amp continually send it's full load to the sub? Because if that's the case I really don't get the whole power handling thing.

P. S.

I'd appreciate a straight answer, but if someone has a link to some reading material that'd be cool, too.

Thanks.

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[Hydrastas 10+ year member]

i have an experience with a sub that i pushed at 150wrms in a sealed enclosure, threw it in a bandpass box with the same power and it blew out magic smoke in seconds.

 

[T3mpest 10+ year member]

I was looking at Kickers web site at the manual for the CVX 12" (mine is coming in UPS Thursday) at the enclosure specs.
I noticed that the compact sealed says 1ft^3 Power Handling = 750rms; SealedSQ (Maximum Enclosure) 4.6ft^3 Power Handling = 300rms.

I have a thin grasp on this, but I don't really get it. I know it has something to do with the tuning and size of the box and how much power the sub can handle in certain frequencies... or something.

But if (for example) I went with the maximum enclosure, does that mean it's pointless to use a 750w amp? Do you only need a 300w amp? And how does the speaker draw less power from the amp just because of the box size?

Also, does the sub draw power from the amp or does the amp dictate the power to the sub? By that I mean is the amp sitting there with X watts waiting for the sub to say give me Y amount now, or does the amp continually send it's full load to the sub? Because if that's the case I really don't get the whole power handling thing.

P. S.

I'd appreciate a straight answer, but if someone has a link to some reading material that'd be cool, too.

Thanks.

IT comes down to effeciency. The point of of adding power is to make the subwoofer cone move further. Put more power on the sub, magnetic strength increases, cone moves further. However, the box has some affect here. The inside of the box is filled with air. This air acts as a spring when the cone moves back and forth. A smaller box will pressurize easier, keeping more force on the back of the cone. This extra force makes the sub less effecient. It has to work harder to move the same distance. A bigger box has less of a damping effect on the cones movement, so less power will be needed to get the same excursion.

 

[RebelDogg 10+ year member]

Thanks, T3mpest. That makes a lot of sense.

So does that mean that a bigger box with a less powerful amp would be louder?

I. E. CVX 12" in MaxSQ box (4.6^3) with a 400w amp would be louder/lower than a Compact (1^3) with a 750w amp. But the smaller one would have tighter bass, but wouldn't hit the lows as well. Seems wrong to me... I'm about to buy a ZX750.1 tonight, that's why I'm curious as to if I'm wasting money. I've already got a ZX400.1 pushing my old sub right now.

 

[T3mpest 10+ year member]

hard saying on if it would be louder or not. A smaller box will peak higher and more abruptly than a bigger box, which may make it seem louder overall. A bigger box will have more output/watt at lower frequencies especially, but a smaller hump in frequency response. One thing to keep in mind with power is this. You have to double power to gain 3dbs. That's assuming the sub actually increases linearly, very few do. Usually once they get up to a certain temp they become very ineffecient, you gain very little by adding more power. In most cases a good sized box will trump power IMO. You can throw as much power on a driver as you want, if it's in the wrong box size you still won't get what you want out of it necessarily.

 

[RebelDogg 10+ year member]

So if I get this zx750.1 tonight (CVX 12"s are 750wRMS) and put it in a box somewhere in the middle of the specs in the CVX manual (b/t 1.0ft and 4.6ft, say 2.5) do you think I run risk of damaging the sub? I mean, is there some way to know if you are sending more power than your box would allow? Such as distortion/clipping. Or do you just wait until you see smoke?

I think I want to order the new amp. If I make the box somewhere in the middle, I think I'll need more than 400w to get the most out of it anyway. But I don't want to kill my sh1t right off because I'm a bit of a 'tard.

P. S.

If you double your power to gain 3dB's, that means that there is only a 3-4dB difference between the max/compact enclosures. Not as much as I thought. But the "thump" factor is what you really change, I guess.

P.P. S. no offence to 'tards. I'm not prejudiced. Some of my best friends are 'tards. All of them, in fact.

 

[helotaxi 5,000+ posts]

The amp sends power to the sub based on a combination of the input signal to the amp and the gain setting. The power handling isn't how much the sub "draws" it's how much it can take before it blows.

The reason that the sub can handle less power in the larger enclosure has to do with the amount of control that the air in the box exerts on the cone of the sub. Think of it as percentages. Relate the change in the volume of air caused by the movement of the sub's cone as a percentage of the total volume of air in the box. Since a change in volume causes a change in pressure, the greater the percentage of volume change, the greater the change in pressure. This change in pressure effectively adds to the moving mass of the driver and limits the amount that the motor can move the cone, thus requiring more power to get the cone to reach its mechanical limits.

Very few companies actually address mechanical limits on their subs and its relation to the enclosure. Kicker is one of hte very few that does so.

There will be a difference in peak output between the small and large enclosure, but not really as a result of the power increase. Doubling the power gets you a 3 dB increase if everything else remains the same. If you change the box, everything isn't the same. When talking about SPL from a sealed enclosure cone excursion is really all that matters. If the sub reaches its max excursion on 300w in the larger box but it takes 750w to reach max excursion in the smaller one, that means that the larger box is more efficient. This is related in Hoffman's Iron Law which states you can have two of efficiency, low freq extension or a small enclosure. If you have a limited amount of power but an "unlimited" amount of space, the logical trade is to give up having a small enclosure for the sake of efficiency to get the most out of that limited power.

 

[JeffM 10+ year member]

What size of sealed box would go well with a 12' CVX?

 

[TeoTorriatte 10+ year member]

FYI -- Kicker's recommended box sizes for the CVX drivers are not consistent with the alignments they recommend for their other drivers. They just copied and pasted the 1.0-4.6 cu ft range from the CVR recommendations, even though their T/S parameters are very different.

Given the CVX parameters, I wouldn't go any larger than 1 cu ft sealed for a 12" -- and a zx750.1 would be about a perfect match for that combo.

Specs (some calc'd by BB6P)...

Name: CVX12 (4 ohm)

Type: Standard one-way driver

Company: Kicker

Comment: CompVX series

No. of Drivers = 1

Dual voice coils = parallel

Fs = 27.6 Hz

Qms = 9.526

Vas = 63.18 liters

Cms = 0.158 mm/N

Mms = 210.9 g

Rms = 3.831 kg/s

Xmax = 15.4 mm

Xmech = 23.1 mm

P-Dia = 259.9 mm

Sd = 531 sq.cm

P-Vd = 0.817 liters

Qes = 0.396

Re = 1.655 ohms

Z = 2 ohms

BL = 12.43 Tm

Pe = 750 watts

Qts = 0.38

no = 0.323 %

1-W SPL = 87.15 dB

2.83-V SPL = 94.09 dB

 

[RebelDogg 10+ year member]

I'm building 2.4^3 for mine.

 

[TeoTorriatte 10+ year member]

I'm building 2.4^3 for mine.

It should handle 750W pretty good in that box... down to about 30 Hz, anyways. So you may want to turn the subsonic filter on if you plan to crank up music with a lot of low frq. content (pipe organ, synth, etc).