Is vent volume included in total enclosure volume?

[BananaLegs]

As per the title. When designing an enclosure, do I include the volume of the vent in the total volume of the enclosure, or is it separate?

For example, if I needed a 10 litre enclosure for woofer x, and I design it as a 9 litre box with a 1 litre vent, does this measure as a 10 litre enclosure, or a 9?

 

[Galu]

I think it is safe to say that, with most vented box calculators, you simply enter the box volume (Vb).

There's one proviso though. The vent volume (Vv) should be small compared to the box volume. I read that Vv must be no larger than 10% of Vb.

If I'm wrong, the expert speaker designers will now be keen to put me right! 🙂

 

[5th element]

The vent and the volume occupied by the driver chassis etc, is not included in the total volume.

 

[ASPERGER67]

Same question as the initial one !
Is the Vent considered as a 'Volume in the Volume' ? Or the vent volume has to be added to the initial volume calculated for a specific Driver ?

Thanks ;-)

 

[AllenB]

As 5th element says, it's best to consider it separate.

 

[Dave R]

There's a nice sketch here (scroll down the page).
https://www.diysubwoofers.org/faq.html

 

[Pano]

You need to subtract the vent and driver volumes from your gross box volume to get the effective box volume.

That’s easy with the drivers (if you know what it is) but you might not know up front for the vents.

 

[planet10]

driver volumes from your gross box volume

I have done this calculation in detail for a large number of the drivers i use and in almost all cases the extra volume from properly chamfering the backside (the red bit) of the driver cutout is pretty close to the loss of volume from the driver being in the box. You mileage may differ, particualrily with big woofers.

dave

 

[6L6]

@planet10 That is a great observation! Completely logical but not something that is immediately obvious.

👍

 

[mhenschel]

I don't know if this needs to be clarified or not but is this right?:
The internal calculated volume per the alignment does not include the vent size;
Since you could just tack the vent onto the outside of the enclosure, if you choose to "internalize" it you need to add that volume to the enclosure volume to determine the correct box dimensions to accommodate both correctly.

 

[Pano]

That is correct.

 

[AllenB]

Well said 6L6.

 

[WhiteDragon]

fancy terms are gross and net volume

the driver and ports displace or remove available volume

so the box needs to be made larger to make up what is displaced.

 

[ASPERGER67]

Ok
I needed that info for a 'reverse engenering' to calculate an inside volume of a Gallien krueger RBH 115 Bass cabinet, and the spécial shape of that cab make it kinda 'tricky' - spécialy to calculate the exact quantity of Wood (3/4 Plywood) - I think I will get it close but not exact....
Thanks

 

[ASPERGER67]

😉As 5th element says, it's best to consider it separate.

 

[ASPERGER67]

👍