# Why do people deviate from the recommended enclosure dimension



## joms

As per JL Audio, the recommended net internal volume of the JL 12W7 in a sealed enclosure is 1.375 cuft. However, i've read from various forum sites that most people do not follow the JL specs but rather make the box larger. Why is this so? Some of them say that the JL recommended enclosure is just for general use. But what other parameters do they consider? If it's a 1-cabin vehicle, do the parameters change such that the box should be bigger/smaller?

In short, what are the variables that affects the box size in such a way that it should be bigger/smaller than the recommended enclosure. 

My subs = JL 12W7
Amp = JL HD750/1 (750w rms)
Box = Sealed
System = tuned for SQL


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## skydeaner

Well just sticking to the sealed box idea in your example to keep things as simple as possible. Going with a larger box will produce a lower -3db point or a "boomier" sound as some might put it. Going with a smaller than recommended box will have a higher -3db point *f3*, and sound "tighter" or less boomy. The one they recommend will probably be somewhere int he middle so it appeals to the most people possible. 

I hope this answers your question somewhat. I tried to put it in plain english. The -3db point is what most people consider the lowest frequency a sub can play acceptably. It is the point where the frequency the subwoofer is putting out is half as loud as the rest of the frequencies it is playing. Anything lower than the f3 point is all downhill and keeps getting quieter as the frequency goes down.


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## rexroadj

The reason for the deviation is pretty much the exact reason why so many people dont use the passives that come with component sets.......A lot of it has to do with placement, needs (what is it needed for, really lows or an all around presence, etc...) power, cabin gain, etc......There are a ton of reasons. Companys give you box specs for "typical" situations. Well since there are so many different types of vehicles.... theres no such thing. I will say that most often the recommended enclosure values work quite well. If your not experienced enough or dont have the tools to figure out some of the reasons for deviations then your better off just going with the recommended specs. (I am not saying your not capable of doing more customized work)


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## 5Speed

Also most seen in ported applications, sometimes the recommended enclosure size and tuning leaves a lot to be desired based on Physical size allocated for the enclosure inside the vehicle, Intended output, and the type of music someone intends to listen to on the subwoofer.

I generally go as large as i can with my enclosures and tune them slightly lower then others as I prefer to listen to R&B and Rap which has worked perfect for me.


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## HertzGuy

What specifications do I look for in a subwoofer to tune a box too?
Say I want to tune a box to 32Hz, how do I know the sub will work efficiently at this frequency?


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## richg101

its good to have a driver with similar fs freq as the frequency you want to tune the box to. on paper this often means the box will be as flat as possible while going as low as the driver is happy doing. applying a 12db high pass that the same frequency will also help and will (on paper) lower your f3 by as much as 10hz in some cases.


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## audiogodz1

Because there is no "perfect". The box dimensions are a baseline. You can tune a car, you can tune a box, but you can't tuna fish.


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## Angrywhopper

The only reason I would ever go smaller than recommended is a space issue. Many people don't want to give up the space that a recommended size box would take.


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## gijoe

2 reasons, first the cabin of the vehicle will change the sound and car A will sound different from car B with the same sub/box combo.

The second reason, and probably the most influential is that this is CAR audio. Nobody wants a sub that needs a huge box to sound it's best in their car. I think most subs would benefit from a bigger box than the manufacturer recommends but if manufactures give you specs for the perfect sounding box they will be big and customers will be encouraged to shop other brands.


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