To port or not to port?

[technofreak]

Hey guys (and girls)

I've been confused by people who I guess think they know what they're talking about but dont really. It's regarding sub boxes.
I've been told that for tighter more controlled bass you'd like to port your box and for a deeper bass to have the box sealed. On the other hand I've been told you get deeper bass with a ported box and a tighter bass with a sealed box.

What's true? Someone help me out let me know what you guys have done or what you guys know so I can make a more informed decision. If you think you know what you're talking about but don't really know, don't post a reply. Thanks.

[Dogo]

sealed is tighter. much tigher.
definitely go with sealed unless you know very well what you're doing
( including the physics of sound and wave reflection )

porting can sound good but you have to design the box very carefully and specifically to the sub that you are using in it. it is NOT the kind of thing you can just go and buy a pre-made box and expect it to sound good.

a well designed ported box will be louder than a sealed but like I said, only if designed carefully.

I reccomend a sealed single 12" . like most things in car audio - get quality not quantity.
ie get one good 12" , not 2 x 10"

also in regards to sub boxes - dont face a box forwards or backwards up upwards etc just because someone tells you to. Try each way and play the range of music that you listen to, and you will know when it sounds 'right' to you

[technofreak]

hey I studied sound heaps in vce physics.. did really well in that topic too. i know heaps about sound and wave composition, reflection, diffraction etc. How would I know to apply it to a box though? and how exactly does a ported box work? why is the port better? or why does it make it louder?

[Pernod]

Based on my experience the key thing defining whether you port or not is the sub you buy.
I am currently running a Cerwin Vega 12" - it rocks it its custom box, but when it was in a seald box for a couple of weeks it was crap! Basically the sub is specifically manafactured to be ported.
In contrast a mate put a port into his 12" pioneer (i think) and it was so crap he ended up putting it back into the original sealed box.

I'm not by any means a pro on this, but my understanding is... (Disclaimer - this could well be wrong because I'm used to only dealing with ported subs in theatre situations).
Basically a seal box ensures there is always a roughly constant pressure behind the sub. This restricts the movement, but also allows for a tighter sound as the sub isn't moving as far and always has a pressure/vacume pulling it towards its neutral point (ie, if the sub is in, the pressure in the sox goes up, pushing it out again. If the sub is out, the pressure in the box drops pulling it back in - thus it has a quicker response time).

A port allows the air to be displaced out of the box, giving the sub further travel. My understanding is that this gives a clearer sound as the sub has no external force on it, however it requires more power (as it has no natural pressure helping it respond to the initial punch) and a slightly different design of sub. Ported boxes also require alot more care to make them sound right as they are more sensitive to bad design.

Whether or not my understanding is correct or not, I know one thing, find out the manafactures recommended box size, port etc and stick to it (if possible).

Hope this helps? And if anyone can correct my understanding then I'd love to find out the real difference... I'm used to working in larger areas than a car so sealed subs are something new to me ;-)

[technofreak]

i have a mate who has 2 12" subs in a single sealed box running off one amp. both subs are single voice coil. They're powerful, but to the tune of hardstyles, the bass seems almost like it's lagging. It's not matching up with the music its out of beat. And then it might match and phase out again. what could be causing this? I dont want that to happen to my setup so if anyone an shed some light on this issue it would be great, for my mate too!

thanks

[Dogo]

hard to tell without seeing the box/subs etc

but I think the problem may be that the box is a single enclosure design
ie it has one large space inside.

the problem with this is that the waves from the 2 subs are colliding and clashing against each other. this not only does horrible things to sound quality and the movement of the waves ( hence the delay ) but if the phase is offset, they can cancel each other out as well.

to fix that just get him to stick a wall down the centre of the box, dividing it in 2 so that each sub has its own compartment.
he could do this temporarily held in with a few nails or screws as long as he fills the holes afterwards.

also if he's running the subs in stereo get him to run them both mono off the same channel

ie don't use a left and right sub , have them both playing off the same channel.

it would also be worth checking that the enclosure volume for each sub is close to the manufacturer's reccomendation.


of course it could also be the subs themselves - 'powerful' subs can move large distances but not necessarily react quickly. some are more designed for a continuous drone in spl and not for punching bass notes

[Nate]

Originally Posted by Dogo

sealed is tighter. much tigher.
definitely go with sealed unless you know very well what you're doing

IMO deffinately go a sealed box ... you can easily in a couple of hours go from a blank piece of paper to a finished box with the right tools... just take your time to get the size right and you will be fine

Originally Posted by Dogo

also in regards to sub boxes - dont face a box forwards or backwards up upwards etc just because someone tells you to. Try each way and play the range of music that you listen to, and you will know when it sounds 'right' to you

what i did to over come this problem but to not waist boot space or wood ... was the build the front and back faces of the boxs to the same angle as the back of the seats (effectively a triangle with the top cut off) /'''\ (for the BG i think it was 65 degrees) so that way i could rotate the boxes any which direction i like and still have them hard up against the back seat.

[twilightprotege]

it all depends on the sub. pure and simple. my sub can handle a pretty small ported box fine, however if you put a different sub in their it wont work. i would suggest working out how much space you can use for a box then find a sub not the other way around.

however, download this awesome program and play : http://www.linearteam.org/winisd.html

[Pernod]

Originally Posted by twilightprotege

i would suggest working out how much space you can use for a box then find a sub not the other way around.

Thats good advice - My Vega fills 1/3-1/2 of the boot. It didn't matter in my old car, but in the lantis the boots a bit smaller!
(Not a big issue for me as there is only 2 of us, but I'm sure it would make a big difference to some!)

[Zed]

So do you have a sub already or are you currently looking for one?

Every sub has a set of T-S specs that will determine what sort of box (sealed/ported/bandpass) would suit it and also how big the box needs to be, as well as size and number of ports if going down the vented route. Some subs will suit only sealed boxes, others only ported, and others again you can run in either type of box.

I'd suggest having a browse through one of the car audio forums - www.caraudioaustralia.com - and searching for topics on box design. It's been discussed many times in the past over there.

In regards to your mate's 2 x 12" setup, on top of what Dogo has said about making sure the subs playing mono signals and in phase with each other, the subs also need to be in phase with the rest of the speakers in the system. The crossover point for the subs is important as well, as having the low pass filter point at too high a frequency can also contribute to slow, lagging bass.