Should I add a port to my small sealed sub woofer box?

[bigron81]

Folks need some suggestions on the following.

Head unit is a boss bvcp9685A. It has a non fading mono sub pre amp out. I have an RCA lead from sub out into a 1x2 patch cable connected to rear 2 speaker channels on my Soundstream PN.4 520d amp. My single 4 ohm Kenwood 3005 sub woofer is bridged.
I got a custom made sealed sub box made to be put in front of the rear seat of my car. Its dimensions are fairly compact. with 15 inches height and width and 9 inches depth.
Settings/gains have been checked. I am just not getting any bass. The same sub amp combo in my other car blows my mirrors. I do have a proper full sized sub box in the other car.
I think I ended up with a very compact sub box. Will porting this box make any difference or not?
Views/suggestions.

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[Bobbytwonames 5,000+ posts]

You need to get a ported box built to the specs of your sub. I'm not sure which vehicle you are working with, but it may end up in a different location.

 

[Dynasty76088]

The owner's manual has box sizes with port sizes for 3 different size boxes.

https://pdf.crutchfieldonline.com/ImageBank/v20030420113200/Manuals/113/113W3005.PDF

Your box if it's 3/4" MDF comes to about .8 ft3 before sub displacement which is 1/2 the recommended sealed size. Correct size should give you a couple more db and ported another 3 or so, big difference.

 

[Jeffdachef 5,000+ posts]

Folks need some suggestions on the following.

Head unit is a boss bvcp9685A. It has a non fading mono sub pre amp out. I have an RCA lead from sub out into a 1x2 patch cable connected to rear 2 speaker channels on my Soundstream PN.4 520d amp. My single 4 ohm Kenwood 3005 sub woofer is bridged.
I got a custom made sealed sub box made to be put in front of the rear seat of my car. Its dimensions are fairly compact. with 15 inches height and width and 9 inches depth.
Settings/gains have been checked. I am just not getting any bass. The same sub amp combo in my other car blows my mirrors. I do have a proper full sized sub box in the other car.
I think I ended up with a very compact sub box. Will porting this box make any difference or not?
Views/suggestions.

where the box is at and how the sub is firing means everything on output. If you are getting zero output in this car and a lot of output in another car, its 3 things.

Your box positioning and orientation is horrible causing phase cancellation which literally results in negative bass. It needs to face away from you and bounce towards a solid wall around 4 inches away from the wall. No reflective wall means no reflective wave that builds into proper sound and sound pressure. Your vehicle acoustics may be different from the other car as well.

Other is the head unit since its a boss, might have a fake RCA output rating which means no matter how you set your gains, you never will get full power out of your amp. You need a true 4 volt sub pre-out, it makes that big of a difference.

Then your sealed box is way too small, space makes bass. Of course the other two are way more important than this factor because even with an inferior box, you should still get some bass. From what you say, it sounds like you have negative amounts of bass which is definitely either signal or phase cancellation.

 

[Jeffdachef 5,000+ posts]

to answer your original question about porting the box. ABSOLUTELY NOT. ported boxes do not work that way, NEVER do that. Ported boxes need to be 3x the size of your current box and the ports need to be big, space makes bass and thats how ported boxes are designed to work, well the actual working ones anyways. Without any understanding of how ported enclosures are designed, putting a hole in a small sealed box wont just make your sub sound like absolute garbage, you will lose output and also damage and tear up your sub because the box is tuned way too high and playing any kind of sub frequencies will cause it to unload which bottoms out the sub mechanically and tears up your surround and fks up your coils.

 

[bigron81]

Thank you all for the inputs.
The vehicle in question is a 2009 Hyundai Sonata.

The sub at the moment is kept in the foot well behind the front passenger seat facing the front passenger seat. I will turn it the other side and see if it makes any difference. Thank you @Jeffdachef for possible positions.

In case it is my boss HU and its limited 2v pre amp output I guess there is little I can do to work on the bass.

I used the Crutchfield information on the recommended box size and according to my calculations my box comes to 1.172 cu/ft. The recommendation is between 1.0 -2.0 cu/ft. Thank you @Dynasty76088 for the link.

I will play with placement and see if it makes any difference and drop the idea of adding a port. I also suspect negative bass being generated.

 

[Jeffdachef 5,000+ posts]

Thank you all for the inputs.
The vehicle in question is a 2009 Hyundai Sonata.

The sub at the moment is kept in the foot well behind the front passenger seat facing the front passenger seat. I will turn it the other side and see if it makes any difference. Thank you @Jeffdachef for possible positions.

In case it is my boss HU and its limited 2v pre amp output I guess there is little I can do to work on the bass.

I used the Crutchfield information on the recommended box size and according to my calculations my box comes to 1.172 cu/ft. The recommendation is between 1.0 -2.0 cu/ft. Thank you @Dynasty76088 for the link.

I will play with placement and see if it makes any difference and drop the idea of adding a port. I also suspect negative bass being generated.

try to get it into the trunk area firing right towards the trunk lid around 4 to 6 inches away. Having it in the cabin like that wont get any results.

 

[bigron81]

So I had the wiring wrong. Instead of using the sub pre out, I tried using the rear L/R speaker pre outs and used LPF on the rear channels.

I bridged the sub and voila all bass is back. Its crisp and clean.

Thanks to everyone for suggestions.