Port in non-optimal position ?

[RobWells]

Have finally decided I need the space in my suv too much to put in a 'normal' sub.

I've decided to go for a pair of 6.5" subwoofer drivers and fit them in the shallowest enlosure possible. Not the best I know but I'm trying to keep all of my rear load space.

What I've decided is to build a box that fits behind the rear seats, but only extends about 3" back at the top of the seat, and around 7" at the bottom (these are guesses, but you can get the idea...) That bit of space is usually lost if anything big is put up against the seat..

The subs will fire forwards, into the rear seat. The seat will be folded down though so not a problem. (A fridge will be sitting on top of the seat back)

My question is whether building a port into the box as in the pic below will work ? It's the only way I can think of doing it.

If not I'll go sealed.

All the amps will be fitted onto the rest of the space in there, so none should be wasted.

The pic is side on, seat to the left, trunkspace to the right.

Thanks,
Rob.

[richie00boy]

Neat design. I looked at something similar for my car and ended up just going with an 8 inch sub in a 6 litre sealed box and touch of EQ. I made two boxes so I can take one out if needs be for a little extra room.

As long as you have accounted for the port volume displacement of the main volume, it should be ok if a little tricky to build.

[RobWells]

Good stuff, will give it a go. Building etc is not a prob. My main concern was where the port starts (being against the back wall) and the severity of the bend.

Usually I would lose the ports and put another driver/s into the port space (and EQ). In this app it's not physically possible.

Thanks,

Rob.

[901Fixer]

What kinda 6.5" subs are you using? How wide is the enclosure, volume, port area and length? I have a pair of TangBand W61139SI in a sealed 14 liter box, push push. They sound good but could be giving up some SPL.

[RobWells]

Elemental Designs 7KV 2 of in a 0.9 cuft box. The vent is 7" x 2" , 26.7" long.

Haven't worked out the box dimensions yet.

Powered by a 2 x 40w RMS amp @ 2 ohms per channel.

Rob.

[901Fixer]

Wow! 13mm Xmax, you better make sure you have enough room in front of the driver so it doesn't reach out and touch anything. Will it be a single internally divided enclosure or two seperate boxes? Have you tried to model it in a TappedHorn?

The glass in most cars will help distribute sub frequencies and many I have seen try to aim towards it but since bass more ooozes out and around the space your port should be fine. Do you actually have any other choice with your tight space constraints?

[GM]

Originally posted by RobWells
My main concern was where the port starts (being against the back wall) and the severity of the bend.

The end correction is greater plus the sharp bend adds a bit of frictional resistance, so the vent will theoretically be tuned somewhat lower than predicted, though usually not an issue in a vehicle app except at high SPLs with the windows down where the driver may bottom out above Fb.

GM

[RobWells]

Thanks GM,

That's good to know - I'll tune it a few Hz higher and see how I get on.

[RobWells]

Originally posted by 901Fixer
Will it be a single internally divided enclosure or two seperate boxes? Have you tried to model it in a TappedHorn?

Do you actually have any other choice with your tight space constraints?

Will be a single box for both drivers. Not tried modelling a tapped horn as I don't think there's enough space to get a long enough line in.

Not much else I can do given my choice of not losing the rear load space.

Cheers,
Rob.

[RobWells]

Well just done the mount for my fridge and it needed the seat back to be in its normal position in order for the fridge lid to open fully.....

So.. Looks like I'm going isobaric 6th order Bandpass:

Have modelled the ports to be within 'chuffing' at the speakers x-max (approx 65W to the pair)

Don't forget to add the cabin gain ~10dB that the car gives...

Not too shabby

Rob.