Flared ports and dual vented / sealed design

[Dave Bullet]

I'd like to build a sub enclosure that is both a vented and sealed design. I thought a "lazy" way to do this is use a steel pipe for the port - with a thread so I can cap it (hence turning it into a dual purpose enclosure).

The reason I want to do the above is to experiment - plus - if I want to switch between freq. extension for HT or better transient response for music - its as easy as cap off / cap on

Two questions:
1. Does using a flared port (the most common I've seen) improve the quality of sound? (or does it just allow you to use a narrower diameter without "chuffing")

2. Does using a steel pipe (assuming I can get one about 4" + for a 12" driver) make sense? I'd need to extend it out of the box so I could pop a cap on it when required....

Hey - if I use a plug instead of a cap - at high SPL I could aim it at the dog

(No animals were harmed - even in a virtual way, in the making of this post)

I'd appreciate any advice.

Thanks,
Dave.

 

[navin]

use a steel pipe for the port - with a thread so I can cap it (hence turning it into a dual purpose enclosure).

1. a steel pipe might resonate. it might sense to damp that resonance with felt

2. the box volume required for most drivers is diferent for bass reflex and sealed if you are looking at "standard" alignments. Since is most cases bass reflex boxes are larger than sealed boxes you can dodge this "bullet" by aiming for a low Qts (try to stick between 0.5 and 0.7) for the sealed box. I wold see what size of box is needed for Qts of 0.5 and see if a bass relfex box can be built within that size (plus the volume fo the port).

flared ports are primarilt used to reduce air speed at the mouth and hence reduce chuffing. reducing chuffing improves the quality of the sound emanating from the port. Still it makes sense to use the largest dia port you can fit in your box and flare that. You can never have too little chuffing.

A steel pipe should work. The lenght of pipe whether it is in the box or out of the box is the same. in short it does not matter if the pipe is in the box or out.

if you are using a loose plug and expecting to use teh port as a cannon dont expct the plug to fly out . it will most probably drop to the floor about 2-3" in front of the speaker

hope this helps.

 

[Dave Bullet]

Thanks Navin.

I presume there is "no harm" in going to big for a sealed enclosure? - well it effectively turns into an IB.

I suppose with the increase in box compliance (assuming I've got that the right way around) you are relying on the driver motor assembly and amplifier for cone control - rather than air in the sealed box.

Does that cause a problem? (or are you saying as long as the Q stays above 0.5 in the box design when sealed - it should be ok?)

Thanks,
Dave.

 

[navin]

keep the qts less than 0.5 for the sealed box. if this box in not big enough for a ported box U will need to add a partition the box that can make it small or large.