Where's the subs boom

[TDot 10+ year member]

Where does the boom of the base come from, the port or the speaker. I'm trying to decide how to have the box built. The box will be in my trunk. Infiniti M.

My options are:

1/ sub facing up with port also facing up.

2/ sub facing up with port facing back seat. (I like this because if I open the passage to the trunk and the boom comes from the port I can get more base).

3/ sub facing the tail with port facing back seat. (I like this for same reason as 3).

4/ sub facing tail with port facing up.

--There will be maybe 3-4 inches between the sub face and the car if its facing up.

--There will be maybe 3-4 inches between the port and back seat.

--There will be maybe 3-4 inches between the port and the car if its facing up.

--I prefer not to go with 3 or 4 unless it would give me a better sound.

So which set up will give me the most boom? Also consider IF I open the passage to the trunk which won't be a regular thing. Thanks.

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[Dmac1991]

I just had a trunk setup with a 15" DC Level 3 and while it did bang the lows like no other, it dropped off rather sharply around 45hz and had little to no output with sub up, port driver side. You might have better luck than I did. It sounded good but I know it can sound much better.

Gonna go with a 12 with sub facing trunk, port driver size and see if I like it more

 

[bbeljefe]

Generally, in a trunk car, your best option is to run sub and port back with the box about a foot from the back wall of the vehicle. Doing the port and sub facing opposite directions is never a good idea, as this will almost guarantee some cancellation of the reflected wave.

And in answer to your question, the boom comes from the sub. Some of it through the port and some of it from the front of the cone.

 

[Side Show 10+ year member]

sub and port firing forwards towards the back seat, fold the centre down to see the sub. have also seen sub forwards and duel tube ports through the rear deck.

 

[MrFoca]

I was always told trunk cars should be blow through or port & sub facing trunk. Bass is reflective Is how It was explained to me.

 

[Side Show 10+ year member]

bass is non-directional..... with any trunk car the trick is to get as much bass into the cabin as possible (coz we don't drive around in the boot do we)

 

---------- Post added at 09:19 PM ---------- Previous post was at 09:18 PM ----------

 

hatches and suvs on the other hand, seem to work a lot better facing the back of the car or faceing up

 

[MrFoca]

bass is non-directional..... with any trunk car the trick is to get as much bass into the cabin as possible (coz we don't drive around in the boot do we) 

---------- Post added at 09:19 PM ---------- Previous post was at 09:18 PM ----------

 

hatches and suvs on the other hand, seem to work a lot better facing the back of the car or faceing up

I wear boot's ??????????? Redwings matter of fact.

 

[Side Show 10+ year member]

killa boots mannnn

 

[bbeljefe]

bass is non-directional..... with any trunk car the trick is to get as much bass into the cabin as possible (coz we don't drive around in the boot do we) 

---------- Post added at 09:19 PM ---------- Previous post was at 09:18 PM ----------

 

hatches and suvs on the other hand, seem to work a lot better facing the back of the car or faceing up

Actually, bass is omni-directional but not localizable.

The biggest problem we see with trunk cars is cancellation and this more often than not occurs when the sub and port are pointing in different directions. On a rare occasion it works out but then, so does buying lottery tickets.

 

[Side Show 10+ year member]

cheers man

 

[TDot 10+ year member]

My options are:

1/ sub facing up with port also facing up.

2/ sub facing up with port facing back seat. (I like this because if I open the passage to the trunk and the boom comes from the port I can get more base).

3/ sub facing the tail with port facing back seat. (I like this for same reason as 3)

4/ sub facing tail with port facing up.

Just want to clarify facing up means right under the rear deck; where my amp and all components are hanging under the rear deck.

Anyway, from the responses it sounds like 3 is definitely out, and probably 2 and 4 as well I assume.

So it seems 1 is the best out of my choices, however, that 12" clearance is simply not going to happen if I have port and sub facing up or the rear seat. The 12" clearance will only happen if I have everything facing the tail/trunk. So which would be better or more important? The 12" clearance, or everything facing the cabin by ways of the rear seat or deck for the boom?

I'll be honest, when I had a sealed box, I heard no difference no matter where I pointed the speaker. I don't know if that was because it was sealed, which is also why I asked if the boom came from the port.

Thanks.

 

[DDFusion]

Either i'm misunderstanding what he's trying to do or he's misunderstanding what he's trying to do and when/why it should be done. Judging from the posts he's made it sounded to me like he wanted to completely seal off the trunk from the cabin to "negate that sound wave issue in cars with trunks" (cancellation). But he never made any mention of firing his sub(s) into the cabin, furthermore he was asking "what dimensions did you make the sheet of MDF", until he chimes in to clear the air I can only assume his plan is to simply put up a wall directly behind his back seat to seal his trunk from the cabin. The only way that would work well is if he is:

A.) Going to run his sub(s) in IB alignment

B.) Going to build a 4th order and port it through the rear deck or ski pass opening.

or

C.) Going to run his sub(s) and port forward with that wall being used as the baffle of the box.

If he's not planning on doing either of the above, sealing off the trunk is a bad idea.

The whole purpose to sealing off the trunk is to eliminate the issue of cancellation due to the front and rear sound waves being out of phase with each other. How do you know if you have cancellation? Easy. Sit in your car and listen to a song you're familiar with, while you're listening to the song have a buddy open the trunk, if the bass gets louder then you indeed are having cancellation issues. How can the bass get louder with the trunk open? Makes no sense huh?

In this picture the vertical line is the back of the trunk and the black box is the subwoofer box which is facing towards the cabin. When the sub hits, the sound goes foward into the cabin (red wave) but also reflects off the back of the trunk to become the reflected wave. When those two waves are way out of alignment as shown in the picture there will be major cancellation. Simply opening the trunk will cause that reflected wave to "disappear" and not reflect back in the trunk and not cause cancellation in the process.

In this picture the sub is aimed at the trunk and the result is that the waves aren't nearly as out of phase as the first picture, resulting in much better bass response but still not as good as it can be.

In this picture the sub box is moved so it's closer to the back of the trunk with the sub firing towards the trunk resulting in the waves nearly being in phase with each other resulting in the best bass response.

Firing the subs/port into the cabin with the baffle of the box sealed off from the trunk results in a wave patter much the same as the last picture, directs all the sound/air into the cabin area and nearly eliminates that horrendous trunk rattle on high powered systems too.

__

 

[TDot 10+ year member]

That's an eye opener. So with the suggestion of never having the speaker and port point in opposite directions because of cancellation, what if I were to build a box to have it pressed right against the passage way with the speaker firing into the cabin and then the port firing into the trunk? Would that cause the same cancellation issues "as bad"? Reason for it pointing it opposite is there's not enough room in the passage to have them both firing into the cabin.

 

[ace_800 5,000+ posts]

Have them both firing towards the back then. I've always heard and applied sub/port back for trunk cars.

 

[bbeljefe]

That's an eye opener. So with the suggestion of never having the speaker and port point in opposite directions because of cancellation, what if I were to build a box to have it pressed right against the passage way with the speaker firing into the cabin and then the port firing into the trunk? Would that cause the same cancellation issues "as bad"? Reason for it pointing it opposite is there's not enough room in the passage to have them both firing into the cabin.

As counterintuitive as it may sound, the goal isn't to fire both the sub and the port through a small hole in your back seat. The goal is to have the sound waves from the port and the sub both leaving from the same place at (roughly) the same time so that they both encounter the same time delays before they reach your ears. Since there is an inherent time delay between the back wave (what exits the port) and the front wave (what comes from the front of the sub's cone), adding a time delay increases the chance of cancellation. And, having them point in different directions necessarily adds a time delay.

This is why you're better off with all the sound waves bouncing the back of the trunk area before entering the cabin. And mounting them pointing up directly under the package tray is not good for a variety of reasons. For one, the potential for rattles increases significantly without a lot of bracing and sound deadening of that panel. Also, sound waves will reflect to the rear and the front, which again can cause a delay that can result in cancellation.

So in the end, either have them both facing rear, preferably with the box close to the rear wall of the trunk or, have them both facing forward.

 

[argenis69 10+ year member]

__

May I ask, where did this information come from?

 

[TDot 10+ year member]

Ok I got it, then from what you say, and my needs for the trunk, its going to be one of two ways.

1/ the box sits up against the back seat with the sub and port facing the tail. In which case it will have the 12" clearance. But in this ill get the cancellation that the pictures illustrates.

Or

2/ have the box sit against the back seat with the sub and port facing the cab. This will give the port and sub 3-4" clearance instead of your recommended 12" clearance due to the 75 degree slope of the seat, but I believe from what you say should reduce the cancellation in comparison to 1.

So which of these two routes will give me the best two results?

Thanks for all your help.

 

[TDot 10+ year member]

Bump

I know the answer to my question would generally be just put the sub in and test it out, but the problem is the design of the box would be very different depending on the answer to maximize space. So any help is appreciated if it's definitive.