building a sub box

Well yes I have, I did not listen to them much but from what I remember they sounded pretty good....I had a old lanzar 12 in a sealed box / in a sort of bandpass setup just a single 12 possible a 10 now that I think about it...just a box  with a plexi glass front....sound real good in my car and the amp I had on it was not real big either... plus it was in the trunk...

I have heard and read alot about them good and bad...

Im just not sure how they would sound

well i guess i'll just have to try it and, see everything i hear is that bandpass gives you good clean bass

thanks everyone who has helped me with my questions.

No offence intended, but why would you try something that you know little about? Bandpass is a real quick way to start blowing up speakers, sure the box looks cool but unless properly done, the results are less than desireable. If the bandpass box is properly constructed or for a given response type or vehicle type, then that is great but it is a very careful calculation to get the proper desired results.

A bandpass box means that it is naturally designed to give loud response in a given frequency range, usually around 70hz, the loudest point in the vehicle (usually). It naturally gets rid of sound above and below this tuning frequency, thus bottom end extension is compromised. It does however give an enormous emount of output in the given frequency range. This is a complex box to construct and dangerous to most subs.

A ported enclosure usually plays to a good volume level, quite high actually and plays to a given tuning frequency, usually around 1 octave lower than most bandpass boxes, thus bottem end extension is better, read more sound and lower levels. It is a fairly easy box to construct if the subs will play in this type of box.

A sealed box is a great choice for anyone but the experienced or task specific user. You can be out by a country mile on the box size and still get good or even amaxing results. The smaller the box is the "punchier" the bass gets, the bigger the box is, the deeper the response gets, just add more power for the "punch" to return. (generally speaking) This is a simple box to construct and one of the safest for subs to play in.

A sub need a given amount of air space to play in for specific types of boxes. It is a fairly simple math equation to figure this out. A sub takes up airspace in the box, thus it needs to be added to the enclosure size. The same goes for a port. Remeber to add these to your calculations. Most people will send you to a volume calculator or box program for this, no worries it will do the math for you, except for the displacement of the sub and port, so remember that. Remeber as well that the recommendations are internal volume so you must add length, height, width for the materials used Here is the math should you want to start learning

l x w x h = cubic inches

12" x 12" x 12" = 1728 cu.in = 1 cu.ft  This is your constant.

Any combination of the numbers above will give you the airspace that you need. Make sure that you have adequate height / width / length in the vehicle, next make sure you have the mounting depth of the sub. You can't put a 6" deep sub in a box that can only be 4" deep.

Volume of a port (if I remeber right)    1/2 x pie x radius^2 = displacement of port, add to box.

Rule of thumb for sub (unless stated) .10 cu.ft for a 10" and .12 for a 12" - add to volume.

thanks for the lesson in sub boxes I think you're right i better just stick to sealrd or ported boxes but how do you know what size of port to put in to a box i mean diameter and length.one other thing where in the sub box is the best place to put them?

thanks again for the info