Windows up subs unload, windows down subs fine

[MADVIBES]

Is it safe to assume that the port is 18" long? or did you cut it down?

[Triticum Agricolam]

I think port is way too big for a box that size, I have a theory about the woofer control with the windows down, with the windows down its acting a like a 6th order series, basically one ported rear chamber firing into a front ported enclosure, with the windows up it behaves like a small box with too much port area.

So what is a symptom of having too much port area, in your opinion?

[MADVIBES]

no choke on the subs at frequencys near or below tuning. I am guessing that box is tuned to 38?

[Triticum Agricolam]

no choke on the subs at frequencys near or below tuning. I am guessing that box is tuned to 38?

No, having too much excursion at tuning is what happens when you don't have enough port area. Below tuning excursion goes up, no matter what. Don't take my word for it though. Assuming you have a ported box in your vehicle, go play a test tone at your tuning frequency, at moderate volume, through your system. Your cone shouldn't be moving much at all, if it is, that's not what you are really tuned to. Now stuff something in your port to obstruct it and tell me whats happens to your cone movement.

[MADVIBES]

I agree not having enough port area will do that, but only when your box volume is large. My car hits 156.7 at 30hz I have a single 2 6" ports. If i plug one My my driver excursion goes way up. which is normal with that much air space and not enough port displacement, how ever when I increased up to 3 6" ports driver excursion went up once again, yes I adjusted the lengths to accomadate for tuning. I think he would be better off with a single 4" aero port

[Jessica]

not much space in front of that port.

[Triticum Agricolam]

I agree not having enough port area will do that, but only when your box volume is large. My car hits 156.7 at 30hz I have a single 2 6" ports. If i plug one My my driver excursion goes way up. which is normal with that much air space and not enough port displacement, how ever when I increased up to 3 6" ports driver excursion went up once again, yes I adjusted the lengths to accomadate for tuning. I think he would be better off with a single 4" aero port

If your excursion went up when you switched to three 6" ports, its because your tuning changed.

You think two 12's on 3500 watts should have a single 4" port? Carry on brother.

[MADVIBES]

I think 2 12" subs shouldnt be placed in a box that small and with the thought that your going to have an ability to put any port that will be achieve deep bass, but you seem to have vast knowlegde so what would you do?

[MADVIBES]

I agree not having enough port area will do that, but only when your box volume is large. My car hits 156.7 at 30hz I have a single 2 6" ports. If i plug one My my driver excursion goes way up. which is normal with that much air space and not enough port displacement, how ever when I increased up to 3 6" ports driver excursion went up once again, yes I adjusted the lengths to accomadate for tuning. I think he would be better off with a single 4" aero port

If your excursion went up when you switched to three 6" ports, its because your tuning changed.

You think two 12's on 3500 watts should have a single 4" port? Carry on brother.

I put that I adjusted the lengths of the port to keep tuning the same, you realize that there is a point of deminishing return right?

[Triticum Agricolam]

I think 2 12" subs shouldnt be placed in a box that small and with the thought that your going to have an ability to put any port that will be achieve deep bass, but you seem to have vast knowlegde so what would you do?

Like I said in my first post, I suggest he checks the tuning frequency under both conditions and see if there is a difference. It is possible he may be able to improve the situation by changing tuning. Though first we need to know what's going on. Its also possible there is nothing that can be done. I agree with you that his subs are too big for his space.

I put that I adjusted the lengths of the port to keep tuning the same, you realize that there is a point of deminishing return right?

Yes I know you adjusted the lengths, but did you actually verify your tuning before and after you make the change to confirm it remained the same? The formulas for port length aren't an exact science and there are a lot of factors that affect tuning that they do not account for. I'm well aware of how diminishing returns works, but that's not what you were experiencing.

I know you are just trying to help, that's great and don't let me discourage you from doing so. I'm just picking on you because your suggestion that he reduce his port area is not sound advice. This community is built on constructive discussion, so if you think I'm wrong (and I am sometimes), explain how and why and we all can discuss it.