location of sub in 4th order bandpass box

[luis1]

Hi. I need some help from all the experts here. I have a bandpass box that want to use with a 12" sub installed in the trunk of my car. I've been reading a lot, and on most of the information I found, the sub is shown with the front towards the ported side of the box. My box is designed to mount the sub so that its back is in the ported side. I have also read that the orientation of the sub should not matter, however I am a little skeptical about it, because I think that it would affect the phase, and could cancel the sound coming from my rear speakers. I thought that maybe I need to change the polarity of the sub.

Could somebody elaborate around these doubts?

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[VWBobby 10+ year member]

The difference in sound might be very slim, but it should make a difference changing what direction the sub is firing. I've never done an A/B comparison before on a 4th order. I've noticed that with a ported box, the location can make a difference in the sound. If its a front port, it tends to have more definition and punch, while a side or rear port has a rear fill sound without much definition....just the low freq extension of the port.

 

[helotaxi 5,000+ posts]

The only difference is which chamber has the displacement of the sub accounted for. As far as phase goes, it is quite simple to swap the phase by switching the wires for the sub at the amp or in the case of many amps, simply flip the phase switch. The group delay of the enclosure will make phasing a tricky one anyway.

 

[RAM_Designs 5,000+ posts]

The group delay of the enclosure will make phasing a tricky one anyway.

This.

 

[VWBobby 10+ year member]

He was talking about the direction of the sub, not the phase. What direction its firing. I don't know about you guys, but my ears can definitely tell a difference listening to the back of a sub (back of the cone) in a box compared to it facing towards you. It has nothing to do with phase.

 

[RAM_Designs 5,000+ posts]

He was talking about the direction of the sub, not the phase. What direction its firing. I don't know about you guys, but my ears can definitely tell a difference listening to the back of a sub (back of the cone) in a box compared to it facing towards you. It has nothing to do with phase.

I was just agreeing that group delay is an issue with BP boxes.

I haven't inverted any subs so I can't really comment on whether or not there's an audible difference of some sort.

 

[helotaxi 5,000+ posts]

The box masks any motor noise. You can't hear the difference in which way the sub is firing in a 4th order since the box fully encloses the sub regardless of which way it fires.

And the OP most certainly did mention phase.

 

[VWBobby 10+ year member]

RAM_Designs, I see what you mean...sorry. I agree with the group delay issue with 4/6 order BP boxes.

It really depends on the ratio of the chamber volume and how big the port is on the chamber. (the non sealed box) I've seen some designs that barely hide the sub, you can see most of the face of it. On these designs, it seems like there isn't as much compression since the port is so large. On these low compression boxes, I've noticed more definition and more clear sound. I've only heard 1 good example in person. A box with a high ratio but a small port opening tends to have that fart box sound. Especially those Audiobauhn type boxes that fire the subs downwards into (4) 4" port..... However some home theater subs and tight location subs are designed this way and seem to work well for 20-60hz operation.