Question on what port length to use on a pair of audiomobile EVO 8's.

[miniSQ]

I have asked this of Audiomobile, but to be honest the answers are a bit vague. So maybe someone could model for me?

The gross size of the box is 1.2 cuft and i figure port, drivers and bracing will be .1 or so. So net volume of 1.1 cuft

They are saying 2-3" port is acceptable and 10-11" range will lead to 35-26 hz tuning. And then followed that up with saying 3" port 12" long would be fine. So i am not quite ready to seal up the box.

I am planning to use a 3" flared aeroport with a 90 degree elbow inside the box. I'm just not sure how long to make it. Maybe 12" is right...but i would like some reassurance. I am using a pair of D4 subs in a single ported box.

Fs-30hz
VAS-15.1 L
QES-.44
QMS-7.7
Qts-.41
Sd-32/206
Re-1.6ohms
.Cms-250
Znom-D4
Le-.94
Mms-112.0g
.No- 09

[Hillbilly SQ]

3" aeroport at full length should do the job nicely for tuning. I'd be afraid of it chuffing at higher volume though but stepping up to a 4" would put you at about 31". It will give you a 29-30hz tune. The port is 17" at full length if memory serves.

[miniSQ]

3" aeroport at full length should do the job nicely for tuning. I'd be afraid of it chuffing at higher volume though but stepping up to a 4" would put you at about 31". It will give you a 29-30hz tune. The port is 17" at full length if memory serves.

I measured the 90 elbow as being 5", plus the full kit, i thought would be too long. So i wanted to chop that 5" off the straight tube and end up around 15" total

4" wont fit in the box i built.

[Holmz]

3" aeroport at full length should do the job nicely for tuning. I'd be afraid of it chuffing at higher volume though but stepping up to a 4" would put you at about 31". It will give you a 29-30hz tune. The port is 17" at full length if memory serves.

^That^ sounds right.

With a box that small in volume, there is only one way to realistically get very low tuning...

Respectfully,
~ The PR department

[JCsAudio]

I have asked this of Audiomobile, but to be honest the answers are a bit vague. So maybe someone could model for me?

The gross size of the box is 1.2 cuft and i figure port, drivers and bracing will be .1 or so. So net volume of 1.1 cuft

They are saying 2-3" port is acceptable and 10-11" range will lead to 35-26 hz tuning. And then followed that up with saying 3" port 12" long would be fine. So i am not quite ready to seal up the box.

I am planning to use a 3" flared aeroport with a 90 degree elbow inside the box. I'm just not sure how long to make it. Maybe 12" is right...but i would like some reassurance. I am using a pair of D4 subs in a single ported box.

Fs-30hz
VAS-15.1 L
QES-.44
QMS-7.7
Qts-.41
Sd-32/206
Re-1.6ohms
.Cms-250
Znom-D4
Le-.94
Mms-112.0g
.No- 09

MiniSQ, send me the box dimensions you want and I’ll model it for you with cut sheets, port length, and type along with other pertinent information like vent velocities and cone displacement. I can do it late tomorrow or Saturday. I can send it to you as a PDF so you can build right from it. I highly recommend using a precision flared port from Parts Express for the best SPL and SQ potential, although a slot port ~ 16 sq inch’s works nice in tight spaces with a low tune.

[miniSQ]

MiniSQ, send me the box dimensions you want and I’ll model it for you with cut sheets, port length, and type along with other pertinent information like vent velocities and cone displacement. I can do it late tomorrow or Saturday. I can send it to you as a PDF so you can build right from it. I highly recommend using a precision flared port from Parts Express for the best SPL and SQ potential, although a slot port ~ 16 sq inch’s works nice in tight spaces with a low tune.

I have the box cut and built, and the flared port. i looked again and its a precision flaired port, not an aeroport flared port. Internal dimensions of the box...40 3/4 long x 9 deep x 5 5/8 high. Chose the size because it basically cut it self out of a drop of 3/4" baltic birch i had that was 50x30 and my car width wad 42 1/4.

[Hillbilly SQ]

Since you already have the port you may as well try just the one at full length and see what happens but make sure you put it in a place where you could add a second one. I think Parts Express sells parts to extend ports to as long as you want within reason so you could do a pair of 3" ports at 34" or enlarge the hole and do a single 4" port at 30".

[miniSQ]

Since you already have the port you may as well try just the one at full length and see what happens but make sure you put it in a place where you could add a second one. I think Parts Express sells parts to extend ports to as long as you want within reason so you could do a pair of 3" ports at 34" or enlarge the hole and do a single 4" port at 30".

You can't fit a 4" port in a 1 cuft box lol. and you definitely can't fit 2 3" ports either.

[JCsAudio]

I have the box cut and built, and the flared port. i looked again and its a precision flaired port, not an aeroport flared port. Internal dimensions of the box...40 3/4 long x 9 deep x 5 5/8 high. Chose the size because it basically cut it self out of a drop of 3/4" baltic birch i had that was 50x30 and my car width wad 42 1/4.

Mini, Please see attached PDF's. One is with a 2" (red) flared port and the other with 3" flared port (yellow). The 2" flared port vent velocities are too high so use the 3". I used a single full 3/4" x 9" x 5.625" piece for bracing in the model assuming you will have two of those that size that are hogged out to 50% of that total area for air flow through them. I used 400 watts per Automobile for power.


Automobile EVO 8 with 2 inch port.pdf
Automobile EVO 8 with 3 inch port (yellow).pdf

[miniSQ]

Mini, Please see attached PDF's. One is with a 2" (red) flared port and the other with 3" flared port (yellow). The 2" flared port vent velocities are too high so use the 3". I used a single full 3/4" x 9" x 5.625" piece for bracing in the model assuming you will have two of those that size that are hogged out to 50% of that total area for air flow through them. I used 400 watts per Automobile for power.


Automobile EVO 8 with 2 inch port.pdf
Automobile EVO 8 with 3 inch port (yellow).pdf

Awesome thanks!! I am not sure i can get all the way to 19" on the port length. I am working on it tonight and i think 14" is all thats going to fit. I assume that will raise the tuning a bit but still be acceptable? I have only 1 internal brace that is hogged out about 60-70 %. But i have a 1" baffle, and the wall with the port is 2 layers of BB, so that is 1.5" and i will do some external bracing on the bottom too. But i am not opposed to moving the internal brace to make room for a 19" port if you think it will make a huge difference ins SQ