how bad is having your subs in too big a box?

[GreenLantern747 10+ year member]

ok, so i measured the prefab box i have for my subs.... it's almost a cu ft over the recommend specs for a sealed box... just wondering how bad that would be for the subs? i'm assumeing that it'll decrease the subs output maybe? any thoughts?

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[cpierce 5,000+ posts]

Ditch the prefab

 

[Chevyaudio 5,000+ posts]

Its not that bad, but i would deffinatly try to build either a new sealed or ported enclosure.

 

[audioholic 5,000+ posts]

ok, so i measured the prefab box i have for my subs.... it's almost a cu ft over the recommend specs for a sealed box... just wondering how bad that would be for the subs? i'm assumeing that it'll decrease the subs output maybe? any thoughts?

No, it will in fact increase output. A larger air space means more air to compress inside the box as the cone moves, which means less resistance on the cone, which means more cone movement allowed, which means more output (whew). It will also shift the response curve lower, your output will/would be quite 'bottom heavy'. You also run the risk of bottoming out the sub, because as I said above, there is less resistance on the sub's cone motion than it was designed for, therefore pushing it beyond its movement limits becomes that much easier.
But there's good news, fixing an overly large sealed box is easy, just throw some bricks in it! But seriously, just take a piece of wood (or combination of smaller pieces) that will take up the apropriate amount of air space (1 cu foot in this case) and your enclosure volume problem will be fixed. But make sure to properly mount the new piece(s) of wood down (screw them in), so they don't bounce around in there.

 

[80INCHES 5,000+ posts]

break up that prefab box and put it the fireplace as firewood

80

 

[GreenLantern747 10+ year member]

i am planning on building the new box, just needs to be designed... working on that.. just wanted to know if it'd be harming them or what...

 

[audioholic 5,000+ posts]

i am planning on building the new box, just needs to be designed... working on that.. just wanted to know if it'd be harming them or what...

Yes, you could harm your sub(s), depending on the power put on it/them.

 

[Termlab 10+ year member]

whats wrong with a prefab SEALED box??? can anybody even tell me why you would recommend throwing it away?

i wouldnt recommend a prefab PORTED box... but sealed?? honestly...

 

[GreenLantern747 10+ year member]

well i've worked it out to 2.8 cu ft (before taking the subs vol. out) and the reccomended is 1.3~2.5 cu ft... so i guess its not all that far off... but it is big and ulgy.

 

[audioholic 5,000+ posts]

whats wrong with a prefab SEALED box??? can anybody even tell me why you would recommend throwing it away?

i wouldnt recommend a prefab PORTED box... but sealed?? honestly...

I dont think anyone was suggesting there was anything wrong with the box other than being too large. I think you are possibly just reading too much into the fact that they referred to the box as 'the prefab'. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

If its of the apropriate size/shape and construction quality, there's nothing wrong with a prefab sealed box. But then, the same could be said of a prefab ported box as well, they are just a bit harder tp find in the 'apropriate' dimensions as they also having a tuning factor to consider.

 

[cpierce 5,000+ posts]

I dont think anyone was suggesting there was anything wrong with the box other than being too large. I think you are possibly just reading too much into the fact that they referred to the box as 'the prefab'. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
If its of the apropriate size/shape and construction quality, there's nothing wrong with a prefab sealed box. But then, the same could be said of a prefab ported box as well, they are just a bit harder tp find in the 'apropriate' dimensions as they also having a tuning factor to consider.

//content.invisioncic.com/y282845/emoticons/yes.gif.2d6d3882a589966b8145fbc57db57f33.gif When I said prefab I meant his box...next time I will re-word it //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[Justinw303 10+ year member]

While we're on the subject of box sizes, I have a question.

I've heard that the bigger the box size, the less power a sub can handle. So the question is, if you have a sub ratedn at ___ watts RMS, and the recomended sealed box sizes are something like .5 - 1.25 ft^3, can you still run the sub at the same RMS wattage in the largest box size as in the smallest one?

 

[stones 10+ year member]

Your ear should be able to tell you when the sub has maxed out, reduce the gain or volume appropriatly.

heres some tidbits on sealed boxes and sub output-

4.2    How does speaker sensitivity affect real world SPL? Will a higher
      sensitivity give me a larger SPL? [MS]                      
========================================================================

When it comes to mids and highs, efficiency (sensitivity) is a fairly
good indicator of output differences at the same power level.  When it
comes to subwoofer performance, the driver's sensitivity is irrelevant
unless you are also specifying a box volume.

An efficient sub requires a larger box to achieve equivalent extension
to a less efficient sub.  In a small box, the less efficient sub will
actually be LOUDER at low frequencies at the SAME POWER as the more
efficient sub.

Linear excursion is a very good indicator of ultimate output capability
(given sufficient power to drive the speaker to that point.)  To make
sound you must move air; therefore, the more air you move, the more
sound you make. When comparing two speakers of equal surface area, the
one with greater excursion capability will play louder given sufficient
power.

 

[audioholic 5,000+ posts]

While we're on the subject of box sizes, I have a question.
I've heard that the bigger the box size, the less power a sub can handle. So the question is, if you have a sub ratedn at ___ watts RMS, and the recomended sealed box sizes are something like .5 - 1.25 ft^3, can you still run the sub at the same RMS wattage in the largest box size as in the smallest one?

As I said in an above reply, the bigger the box, the bigger the 'air cusion' on the sub, the easier it is to move the cone (more air to compress = easier to compress). So yes, logic would dictate that if its now easier to fully excurt your speaker's cone, power handling (mechanically) would be lower. But, this is a good thing, as less power is required for a given cone excursion (and thus, output level).

 

[squeak9798 5,000+ posts]

No, it will in fact increase output. A larger air space means more air to compress inside the box as the cone moves, which means less resistance on the cone, which means more cone movement allowed, which means more output (whew). It will also shift the response curve lower, your output will/would be quite 'bottom heavy'. You also run the risk of bottoming out the sub, because as I said above, there is less resistance on the sub's cone motion than it was designed for, therefore pushing it beyond its movement limits becomes that much easier.

Well, not sure if I should agree or disagree with you here.

A bigger box will have less overall output; but may have more output at lower frequencies due to it's increased low frequency extension. But, if you go too big, you'll loose both overall output and low frequency output (extension).

Here's a good graph to visually explain it: