Dmak

<p><font color="#000081" size="3"></font>
Dmak</font></b>
<a href="http://131.107.68.28/a4.org/registry/details.asp?car=1149"><img src="http://www.home.earthlink.net/~gbss/DHRE.gif"BORDER=0></a>
</a>

eh-fow

Bandpass is good if you want noise, but it seriously boosts a specific frequency depending on how the box is "tuned" which can sound a bit wierd if you are going for SQ.<p>Dan
99 1.8TQMSX K04 Santorin
<a href="http://registry.audiworld.com/audi/registry/details.asp?car=1564"><img src="http://pictureposter.audiworld.com/AudiWorldPics/2000/dh-sig.gif"></a>
<a href="http://a4q.tripod.com">a4q.tripod.com</a> -- My site

audimods

<p>2000 A4 1.8TQMS

siberian

Sealed= overall best sound quality, but least efficient.. (don't worry about that- just get a good sub and amp and it's a non-issue)

Band Pass= most efficient, thus potentially the loudest, but sound quality can GREATLY suffer. Unless your soul purpose is to win an SPL competition, I'd eliminate this one right out of the gate.

Ported= Sacrifice some sound quality and "tightness" in the bass for a little more volume. The boost in volume occurs at the frequency that the port is tuned to.

Side note- my last system had a ported box... it sounded okay... but it displayed a bit of a surge in loudness whenever the music happened to hit the frequency it was tuned to. (I think it was like 45hz if memory serves me correctl..... By comparison, my sealed box on my new system sounds noticeably tighter.

D.T.Sealy

That is a brave statement to make, but it is a true statement that no one on this forum, or in the world, for that matter, can dispute. There is no best, it is a simple matter of preference and maximizing the performance of a woofer to fit your needs.

A sealed enclosure, aka acoustic suspension, are the simplest of enclosures to build. A sealed box lends itself to good control over the driver, due to the air behind the cone acting as a spring, or suspension for the driver. They are also the most forgiving as far as volume calculations are concerned. The smaller the enclosure the greater the increase to the resonant frequency and to the Qtc, the strength of resonance.

A Ported enclosure, aka vented, is merely a sealed enclosure with a tuned port. A vented box provides some great advantages over a sealed box. A vented box may increase the low frequency output by twice that of a comparable sealed box. Also, you can have a greater degree of control over the driver than with a sealed box. I know everyone will disagree, so I'll go ahead and defend that claim. This is only true above the tuning frequency. A sealed box uses the internal air suspension to control the driver. One may think then that it would be impossible for the vented box to have greater driver control than a sealed, since there is a constant gaping hole in the enclosure. Since the enclosure is vented, the compressed air attempts to escape the enclosure, through the vent tube. A pressure gradient starts traveling outward through the port. Then the speaker changes directions and starts traveling outward. The combination of the pressure gradient traveling outward and the speaker traveling outward creates a vacuum, which would not exist in a sealed enclosure. But wait! There's more! Now the pressure gradient changes directions and starts moving inward, likewise, the driver's diaphragm changes direction and moves inward. Now we have created more pressure in the enclosure than there would have been inside the sealed box with the same driver. Thus, we have achieved a higher level of control! This control is dependent upon the enclosure's tuning frequency. If the frequency of the signal being fed to the driver is lower than the tuning frequency, then the driver is changing directions at a slow enough rate to allow the pressure gradient to be blown out of the port and all control is lost. However, if the tuning frequency is too low, you end up with a relatively weak bass response. If you are planning on using high end subs and high power, I would consider using a low frequency cutoff, such a crossover high-pass for the subs low end, or tune down the lowest frequencies with an EQ, to achieve the best possible performance.

A bandpass is a highly misunderstood creature, thus it is usually incorrectly utilized. A bandpass is nothing more than the combination of sealed and vented enclosures, or the combination of two vented enclosures. Yes, the are other combination that use more than two enclosure, but honestly, who wants to get into all of the complication of building one for the car. Leave that for Bose to do for the home products. Bandpass enclosures allow you to use the enclosure as a crossover. That was there original purpose. Thus the name bandpass. Usually in cars, they are incorrectly designed, and they function as distortion maskers. You can't hear your poor little woofer flopping all over the place and you want the bass louder, so you keep cranking it until it simply falls apart, or the voice coil gets completely dislodged from its gap. They can be very cool, if designed properly though. I had a isobaric bandpass with four 8" subs in my trunk, with the two internal chambers vented through my rear deck. Thus, no disgusting trunk rattles. I would prefer a good sealed or vented design over these enclosures though. Mine was simply for display; it's trunk wall was plexi and internal walls were mirrored.

As far as power handling is concerned, the enclosure won't make much difference at realistic levels. If you are considering runnning a single low power handling sub with ten times it peak power rating, then ask about that. Or better yet, ask yourself what you're hoping to accomplish by doing so. However I will say this: A vented and bandpass will be the most susceptible to power-caused failures, if they are designed improperly. You won't hear the problem with the bandpass, and the speaker will flop around in them both if tuned incorrectly, rendering their design advantages useless. The transient response will be great from both sealed and vented enclosures, once again, if they are designed correctly. Transient peaks will sound 'slow, muddy, and weak' if the sealed box is too large, the vented box is tuned incorrectly, the driver is in the wrong box type or there is too little power available.

This has been long enough already, so I'll spare you my transmission line and horn loaded enclosure speeches. I hope that all of this has provent that there is indeed no best, it is simply a matter of taste, need and goals. I hear people griping constantly about there subs sounding horrible and they are using poorly constructed boxes and suffer from any/all of the above problems. Good bass reponse only occurs with woofer control. Control is a function of the entire sub system: the driver, enclosure, amplifier, and the input signal. Thanks for reading!

CARYB

<p><a href="http://registry.audiworld.com/audi/registry/details.asp?car=2176 ">
<img SRC="http://pictureposter.audiworld.com/AudiWorldPics/2000/Audi-Signature-3.jpg" BORDER=0></a>

<a href="http://pages.prodigy.net/cary-b/">
HomePage

Dmak

<p><font color="#000081" size="3"></font>
Dmak</font></b>
<a href="http://131.107.68.28/a4.org/registry/details.asp?car=1149"><img src="http://www.home.earthlink.net/~gbss/DHRE.gif"BORDER=0></a>
</a>

Dmak

<p><font color="#000081" size="3"></font>
Dmak</font></b>
<a href="http://131.107.68.28/a4.org/registry/details.asp?car=1149"><img src="http://www.home.earthlink.net/~gbss/DHRE.gif"BORDER=0></a>
</a>

Mr T

HMM
Synopsis
Sealed- most accurate,least distortion. Flattest response
vented- more efficient, but in a smaller range of
frequencies.]


so depends on what u want.

u can kinda lump all the vented designs into one catagory (bass reflex, 5,6,7 etc band bass) the higher the order of bandpass the more 'peaky" the response--i.e. it becomes basically more tuned to one specific frequency.

Another way of looking at it is the band width vs efficency (a 'product' rating)

the flatter the response, the less efficient, the more efficient, the narrower the frequency range the system will produce.

Also remember less efficient requires--more power for same volume.

Building yourself??
Sealed is easiest to get predictable response. In my opinion (0.02) you CANNOT possibly design a vented enclosure without a LOT of equipment, calculations etc. (esp high order) The design is too succeptable to errors in calculations, misalignment, etc.

above is all things being more or less equal, etc
Tonnes more detail, things to consider:
phase distortion
which drivers--a driver should be chosen to match the target enclosure. Poor matching=poor system.
Physical--Size
Location,etc
and then there are the esoteric enclosures
--ever seen a 15" sub in a concrete horn enclosure???

HTH.

I can recommend a couple of good short books.

1996 a4 2.8 qm 12v

Mr T

3 American Sound 12" subs in a Monte Carlo, Circa late 70's.
I have no idea why, but it was clean and tight.
fluke?