port placement for dual sub setup

[Jhensley209]

Whats the best port location for an enclosure for 2 12" subs in a trunk car? I heard center port was the best but im not sure and would like to learn which is better?

[ckeeler11]

port and sub on the same plane works the best. Port location on that plane usually does not make a difference.

[fecupe2001]

port and sub on the same plane works the best. Port location on that plane usually does not make a difference.

Not really bro, definitely don´t agree with ya on this one, port location on the same plane is not a constant, and port location on the same plane does make a difference, specially when the box is too wide and a sub is too far away from the port , cheers!

[DLHgn]

port and sub on the same plane works the best. Port location on that plane usually does not make a difference.

Not really bro, definitely don´t agree with ya on this one, port location on the same plane is not a constant, and port location on the same plane does make a difference, specially when the box is too wide and a sub is too far away from the port , cheers!

How does this affect the SPL? I'm just curious to know the specifics if you happen to know yourself.

[fecupe2001]

Some cars LOVE port in other directions , depends on how you manage to turn the cabin into a 6th order bandpass

For the port placement on the same plane, if it´s for music, generally speaking the port on the center manages to have a good airflow, less cancelations and few other things, when you have the port on one side, the sub that´s further away tends to bottom out a little bit and causes sometimes some cancelations (not a constant of course), also, that port on one side makes the car louder to one of the sides in front of the car wich is good if you care about score or demoing to the passenger side, port on the center sounds pretty similar on both sides.

Once again, not constants at all, that doesn´t exist on car audio if you ask me, also, sorry about my english, long time without practicing it

[Krakin]

It has to do with acoustics.

You have many factors, but for stating just a few of them:

The closer your port is to your driver(s) the higher your output will be at the tuned frequency of the port.

The location of the port mouth will change your response due to the reflection of frequencies off your baffle.

The location will change what your edge diffraction will be.

There are obvious limitations you can get for your port area based on where your port is on your baffle.

Lots of things to do with acoustics based off of objects in your enviroment, so your spatial loading will be different. For purely SPL reasons you would want your spatial loading to have the smallest angle from the port (think of a megaphone, this has a very small angle) to increase the acoustical load driven from the driver(s).

For some visual examples here is a Sundown SA-12 D4 in a the generic box suggestions that Sundown provides with the port next to the speaker and away from the speaker.

Mind there isn't any outside acoustical factors considered in these examples, but could be if you knew how to measure your car's gain.

System 1 and 2 Baffles:

The responses of both designs.

System 1:

System 2:

It is kind of difficult to see because of the line thickness depicting the system output in decibels, but the first system has around a 3 dB increase in output at the tuned frequency.

This is equivalent to the average difference of going from the 600W that these are modeled with to making system 2 have a 1,200W signal from the amplifier.

[Krakin]

Just because this is about two subs I redid my example with two speakers and moved the common mic to a location of [1m,1m,1m] from the baffle.

[DLHgn]

It has to do with acoustics.

You have many factors, but for stating just a few of them:

The closer your port is to your driver(s) the higher your output will be at the tuned frequency of the port.

The location of the port mouth will change your response due to the reflection of frequencies off your baffle.

The location will change what your edge diffraction will be.

There are obvious limitations you can get for your port area based on where your port is on your baffle.

Lots of things to do with acoustics based off of objects in your enviroment, so your spatial loading will be different. For purely SPL reasons you would want your spatial loading to have the smallest angle from the port (think of a megaphone, this has a very small angle) to increase the acoustical load driven from the driver(s).

For some visual examples here is a Sundown SA-12 D4 in a the generic box suggestions that Sundown provides with the port next to the speaker and away from the speaker.

Mind there isn't any outside acoustical factors considered in these examples, but could be if you knew how to measure your car's gain.

System 1 and 2 Baffles:

The responses of both designs.

System 1:

System 2:

It is kind of difficult to see because of the line thickness depicting the system output in decibels, but the first system has around a 3 dB increase in output at the tuned frequency.

This is equivalent to the average difference of going from the 600W that these are modeled with to making system 2 have a 1,200W signal from the amplifier.

Thanks for that Krakin. That's the kind of response I was looking for. In depth enough for me to get an insight into but not complicated enough for me to really have to stop and think about it.

[DLHgn]

double post. Sorry

[Krakin]

Thanks for that Krakin. That's the kind of response I was looking for. In depth enough for me to get an insight into but not complicated enough for me to really have to stop and think about it.

Remember though that the response is largely due to the location of the mic as well, if I was measuring the response from the bottom of the box the second system in both examples has the louder response. Then if you increase the distance away from the box the systems start to get closer responses to each other.