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-   -   ¿Sealed or Ported? (http://www.diyaudio.com/forums/car-audio/41269-sealed-ported.html)

eXn 21st September 2004 12:14 AM

¿Sealed or Ported?
 
In your own oppinion do you prefer sealed or ported sub boxes?

SupraGuy 21st September 2004 04:51 AM

Sealed.

Sealed boxes offer fewer variables, and tend to be more predictable in a car environment particularly. They offer faster transient response, and to boot take up less room and are easier to build.

Ported boxes technically offer lower distortion, and don't have the nasty habbit of leaving my subs at high excursion whenever I drive up or down some of the long hills that I've been known to drive over. (I can get out of the car at the top of a hill, get out and open the back of the car and SEE the subs pushed out for about a minute or so after I get to the top. That box is SEALED. -- I can't watch it happen if I've been playing music while driving though.) Ported boxes are also more efficient down to the tuning frequency, below which response drops off much faster than with a sealed box.

Over all, the advantages of the sealed boxes heavily outweigh the drawbacks, but that's to me. I'm not looking for a few extra dB of efficiency, and the music that I listen to is better enhanced by something with a fast transient response, and smooth rolloff into both the subsonic and midbass.

BillFitzmaurice 26th September 2004 01:32 PM

Horns. With sensitivity 10dB higher than direct radiator boxes they sound twice as loud and are clean beyond belief. The only drawback is you have to build your own.

offroadbum 27th September 2004 06:53 PM

Ported=less power to move air,boxes are colse to twice the size of sealed,and more boom
Sealed=more accurate,smaller box.

Myself i perfer sealed.

their are so many variables in taste of music and the environment
that your listening in.like pickups seem to work better with small drivers in sealed boxs.autos with trunks seems to work well with large drivers in ported boxes.hatchbacks does well with either.

If your wanting recommendation give a little bit more info and maybe someone will be able to help you out.
Donnie

BillFitzmaurice 27th September 2004 07:55 PM

Quote:

Ported=less power to move air,boxes are colse to twice the size of sealed,and more boom
Actually the inverse is true; to achieve the same response with the same driver a ported box will usually be far smaller; that's the reason for the popularity of ported boxes; if the opposite were true no one would use them. Model a woofer response in WinISD for both cases and 90% of the time the vented box is smaller than sealed to reach the same f3.

offroadbum 27th September 2004 09:38 PM

Bill
I`m not disputing what you saying,I just usually build what the factory recommends.As a matter a fact I`m look at a fact sheet for an 8" car audio driver,they recomend .38cft for sealed and.75cft for ported.
Now the f3 is very different,the sealed is 63hz and ported beinng 35hz.

BillFitzmaurice 27th September 2004 10:13 PM

Quote:

Now the f3 is very different,the sealed is 63hz and ported beinng 35hz
Precisely. Now consider this: a sealed box rolls off at 12dB/octave below f3, so assuming the two alignments have the same base SPL the sealed box in this case will be down 12dB below F3 at 31.5 Hz, and compared to the vented box will be quite anemic. In the average home that would be very poor response (and should tell you why Auto Subs don't always work well outside of their intended environment). But both boxes are subject to cabin gain at 12dB per octave at any frequency where the longest interior dimension is less than 1/2 wavelength; at 8 feet for the average car that means from 70 Hz. Now which sounds better in a car?

The sealed, as despite its higher f3 the cabin gain balances that out, while the vented gets too high an SPL in the bottom end. It's not being sealed that makes it better, but in this case where a higher f3 is desired sealed in a small box does the trick. Vented in a small box wouldn't work as well as VBs rolloff at 24dB/octave below f3, so cabin gain would be inadequate to balance that out.

SupraGuy 27th September 2004 11:39 PM

And the long and short of it is that a sealed box in a car audio environment is typically superior to a ported one.

I actually carefully measured cabin gain in my car before designing my box, then designed the parameters for the subwoofers to give me an inverse of the cabin gain curve. I actually made the boxes smaller than the manufacturer recommendation, and in free air they'd be pretty weak. In the car their f3 is about 23Hz, although there is a slight "bump" at 40Hz.

Since this thread is in the "Car Audio" forum, I assumed that the question referred to a car audio installation. Take advantage of cabin gain. :)

In a home environment, a properly designed ported box will give you more bass extension, and lower distortion (Although somewhat weaker transient response) and is generally a winner.

One thing to be aware of with ported boxes is that response falls much more sharply below tuning frequency, as does power handling. As such, your ported box with an f3 of 34Hz isn't going to work as well as even my small sealed boxes at 25Hz, let alone 20Hz. While mine will be weak, the ported box will be weaker, and it would actually endanger the woofer to attempt to drive it at those frequencies.

Of course, in the end, this is my opinion. A car sound system is a collection of trade-offs, and unless someone ccomes up with clear and convincing proof of one or the other type of enclosure being superior in all respects, people will continue to have their own opinions and choices.

eXn 28th September 2004 12:12 AM

What is f3 and what exactly is the horn. Is that just for subs or can u put other speakers in it because on the website it mentions tweeters.

BillFitzmaurice 28th September 2004 01:12 AM

Quote:

unless someone comes up with clear and convincing proof of one or the other type of enclosure being superior in all respects
That would still be a horn. It does suffer from being larger than most autosub boxes at 14x14x32 inches, though that's certainly not larger than any other autosub boxes by any means. http://www.billfitzmaurice.com/plans.../auto_tuba.jpg

http://billfitzmaurice.com/plans/images/autotuba.jpg


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