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Subwoofer placement

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Subwoofer placement in a trunked vehicle

The problem [with facing the subwoofers forward in a trunked vehicle] is that the subs are not loaded against a hard boundary surface of the vehicle. In a trunked vehicle, you have to think of the interior of the car as the area between the dashboard and the rear seats. If you place a sub box behind the rear seat, you are really putting it close to the middle of the car, definitely not the ideal position.

Now, you have two good, and two "OK" options:

Good

  • 1. Install the subwoofer in the rear side panel (or in between the taillights and the strut tower). This is called corner loading. Since the subwoofer is as far back as possible in the vehicle, there will be no rear sound wave that can interfere. As well, you will have hard boundaries to the rear, and sides.
    2. Install the subwoofer in an enclosure facing the very rear of the vehicle. Optimally, within a foot. This allows for the rear wave to exit through into the cabin of the vehicle, as well as the front wave to reflect off of the rear of the vehicle, and be reinforced by the rear wave.

"OK"

  • 1. Install the subwoofer in the very front of the trunk (against the rear seats). This is much better than facing the subwoofer forward into the cabin of the vehicle because it still has a hard surface to be loaded against, and the rear wave will not interfere with the reflected front wave.
    2. Install the subwoofer facing towards the trunk lid. This method is still better than facing the subwoofer forward into the cabin of the vehicle, but becoming less effective. There is still the hard boundary (trunk lid), and lack of rear wave, but the problem is, the reflected wave from the trunk lid does not flow directly into the cabin. This can be partially alleviated by installing the subwoofer on a slight angle towards the rear of the vehicle.

Now, having the subwoofers facing forward (towards the passengers) is not always bad, but you have to ensure that the rear wave cannot reach the front wave. In other words, you must completely seal off the trunk from the cabin of the vehicle. Same can be said for subwoofers installed in the rear deck, and free-air subwoofer installs.

Subwoofer placement in a SUV/Hatch

Now, in a SUV/Hatch, the whole cabin of the vehicle is open. This makes these vehicles much easier to get loud, and reduces cancellation for the most part.

Same principles apply as a trunked vehicle though, but there can be twists to them, such as the ported "CRX-style" box, which has the ports facing the rear of the vehicle, and the subwoofer(s) facing upwards.

Here is another good read with some pretty pictures:

Subwoofer placement

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Can anyone clarify. In the Part 2 of the Good section, am I reading this right? The speaker cone should be facing the rear of the car? Or does the cone face forward? If it is to face the back of the car from the corner, I do not see how this could be done.

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Box faces towards the rear, cone faces that way as well. Maybe you should re-read, since it says not one word about a corner.

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Can anyone clarify.  In the Part 2 of the Good section, am I reading this right?  The speaker cone should be facing the rear of the car?  Or does the cone face forward?  If it is to face the back of the car from the corner, I do not see how this could be done.

Oh so Under GOOD 1 and 2 are two independent solutions for good bass response? I read them as Step 1 and Step 2. So it really means, either place the sub in the rear corner, or options 2, plce the enclosure with the sub facing the rear of the car.

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When i switched over to the ava, we fired it towards the rear (trunk setup) but i swear i think it sounds better facing forwards (i switched it later for comparison) Dave and Jack_Frost both recommended rear firing but i just don't like it as much, it sounds more like...well like sound is in the trunk, lol. In all honesty the cone was about 3" from the rear of the trunk so maybe that contributed.

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Does anyone have any ideas about replacing the rear deck of a car with 3/4 inch MDF and mounting the sub and ports firing against the back glass, using the trunk as a box? I am planning on doing this to a 94 Grand Prix. I'm hoping that this turns the trunk into a box, and theoretically gives the drivers compartment the transfer function of a hatchback. anyone have any ideas? :unsure:

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Ive seen it done, but not ported.

It would be more infinite baffle than anything since the trunk is so large.

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Cabin gain would be your friend in that case.

But, to do it successfully, you will need some very good fab skills.

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I cut the MDF to fit, I seal everything with Polyurathane adhesive if a tube(like a caulking tube), then use spray faom sealent to seal on top of the poly sealant. would that be enough behind the seat and on the deck? or should I reinforce the sides of the trunk with MDF? I will be putting viscoelastic vibration dampener on every trunk pannel? Is there anything else I may need to address?

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would it be better to build a large slot port, with the 3/4 in MDF behind the seat as 1 side, the modified 3/4 inch rear deck as the top(with the 12 and dual ports), make a back and sides out of MDF and build it in the trunk?

That would still solve the problem of having to pressurize the trunk area too.

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Unless you can *perfectly* measure the volume in your trunk and it happens to be *just right* you really can't port an IB setup. Plus your tuning would change everytime you put anything in your trunk. You can fire your sub and port directly into the car from a box though. In which case you can either build it in the car, or build it externally but have it fit so you can bolt it in place where the port and cone fire directly into the passenger compartment.

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Is there any correct port orientation in an suv for sub up/port back such as sub left side up, port passenger side back or sub passenger side up port drivers side back?

I'm building a new box when taxes come in and I'd like to get the most out of the design. My current box is sub up port firing to the side of the vehicle on the passenger side partially obscured by the wheel hump; I feel like this affects response a bit.

In particular, would I lose anything with the sub centered in the box? I think that orientation looks the best.

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Also, does sub orientation work the same with passive radiators since both faces have significant radiating area, if I did radiators up sub back in an suv would that compromise response versus sub up radiators back?

 

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You really can't do radiators facing up or down. Gravity isn't your friend in that instance and the cone will sag from gravity pulling on the weight. 

The rest of it is pretty much completely vehicle dependent and needs testing to determine for sure which orientation is optimal. 

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