Closed Vs Vented Enclosures

[rollin24's]

Hey,
i have a question wich is a bit wierd :S....
why do people prefer to construct a subwoofer enclosure wich is a closed box rather than a vented, with a vented box u get alot deeper and better bass response i dont understand why people dont like the vented box and prefer the closed box
thx

[morpheus82]

vented enclosures are much more sensitive to misaligned design parameters. Precise mathematical calculations of vent/box parameters are required for alignment with the driver. it's very easy to lose sound quality...

[rollin24's]

yeh but its very rarely for that to happen.... most of the time u are accurate with it

[morpheus82]

also the rolloff at very low frequencies(after the cut) is higher, this means it gives you more power at low, but under it kills the lowest, degrading sound quality...if you can hear the difference!

[Greybeard1]

sealed boxes have typically MUCH lower group delay, and usually sound far tighter and more musical.

sealed boxes have a much shallower rolloff and thus can actually have deeper extension (below Fb) than a vented box. This shallower rolloff better matches typical room gain down low and aids in have the sub match the room better (not so much of a potential low end hump)

sealed boxes don't unload below tuning frequency, unlike vented boxes. Vented boxes often require a subsonic filter to save the driver from damage, which further decreases low-end performance (particularly below Fb... intended) and greatly increases group delay above the already worse group delay of a vented box (unintended and unwanted).

sealed boxes are usually smaller.

sealed boxes are easier to build and much more forgiving of incorrect T/S parameters... tuning is easily altered by changing the amount of stuffing, which allows you to vary box size over a 20-30% range.

lastly... a great quote from Jon Marsh at the HT forum, one which I've found to be accurate with the exception the Infinite baffle (IB) sub, only because I've never heard one

In order of fidelity, here's how sub designs rank:

1) Large IB sub, Qtc 0.4 to 0.5

2) Sealed box sub, with Linkwitz transform

3) Sealed box sub, no Linkwitz transform, Qtc 0.4 to 0.566 range

3) Ported alignment with no peaking and shallow roll off to Fb, (lower Q), ~ -3 to -6 dB at Fb.

4) Conventional ported alignment, maximally flat

5) High order ported sub alignments using EQ- Chebyschev or other alignments

5) PR subs.

GB

[Ron E]

Vented and closed speakers have a different sound. It is hard to explain to one who has not heard several different sealed and vented speakers in the same room. Honestly, when well designed most people will not be able to listen to aspeaker and definitively say - that is ported or that is sealed with a Qtc of x.xxx...

Vented have a lot of advantages. In band power handling, SPL, and distortion near resonance are all superior to sealed boxes. They also reach deeper with the same sized enclosure. Their main disadvantage is poorer transient response and poor power handling below resonance. The transient response issue can be mostly avoided if your vented box is tuned to less than 30Hz or so, because much of the difference in transient response is simply ringing at resonance, and you won't hear 30Hz ringing.

Sealed boxes have better powerhandling below resonance and they have no midrange leakage or port air rushing noise. Sealed boxes can also have a bit of a fool you quality due to their slower rolloff rate. I have some sealed boxes with 55Hz F3 and they go deep enough for most of my purposes.

[planet10]

Originally posted by rollin24's
and better bass response

That is very disputable....

Greybeard did an excellent job of explaining why a sealed box is often quite a bit better than a BR... myself i've not had many BRs in my room that didn't have to be made speriodic to sound OK.

dave

[SmarmyDog]

Other than the statement that 'sealed boxes are usually smaller', Greybeard1 is right on target from a sound quality perspective. I don't know if I'll ever do anything with it, but I do hold a patent (#07068806) to address the size issue.

-Casey Walsh

[jasonsrt4]

Funny, I could not find your patent in the US patent and trademark database.

[SmarmyDog]

Hi:

If you go here:

http://patft.uspto.gov/netahtml/PTO/srchnum.htm

and enter 7,068,806 it should work.

The browser plug-in from alternatiff.com is great for viewing the images.

-Casey