bkolfo4

I have owned Tumults and Avalanches (Chad actually used my Tumult in his original comparison tests). Unless you are running less than 1000 watts, the tumult is a better driver.

One year later. . . Finally getting to work on the car after building a house and a couple of other projects. Slowly working on the drivetrain, and it is now drivable. Second skin for the roof went in tonight so I can have the headliner installed.

Thank you.

That is why I asked how wide the opening inside the box was. You need to account for both 90s in the current box.

What are the external dimensions of that box?

You post a lot of good info, but this is absolutely not true.

How wide is the opening inside the box? Looks like it is ~6". Are you adding the length created by that corner into the port length calculations?

Arsenal or Chaos 10's

If it is under the seat and you want small, the Massive N2 or N3 might be a good fit. Nice amps, inexpensive, and small.

Left and right sides are 12" not 11.25" Wrong. It says 2x front (3 pieces total) 13.5 - 2.25 = 11.25

That is incorrect. People have a lot of incorrect information on port area. Only thing worse is all the misinformation on impedance rise Port area is based on air speed through the port, which is based on cone area x Xmax (called Vd) and port tuning frequency. 95% of the car boxes built do not have the required port area for 100% linear operation at maximum output. That is why it is funny to hear "too much port area". They end up with port compression which alters the operation of the port without them even knowing it because it gets too loud in the car anyway. Car boxes are almost always designed with a high Q and will peak above port tuning frequency. This has nothIng to do with how much port area you have. It is the design. To have too much port area would mean having resonant problems within the port itself so that it does not act like a helmholtz resonator because of the port size vs. the box size. More than likely will never happen in a car box. . . I have run 386 sqin with 11.8 cuft tuned to 34 Hz in a box designed for music. No problem at all.

Double the area and then calculate the required length.

Who cares!!! I think he should. If he has too much port the box could start sounding like crap. And start to decrease spl substantially. You are confused.

You could do a couple of 6" aeros or 4 4" aeros to save space. Either setup would need to be 17" long, so you need 21"-23" of depth if you go that route.

6.5-7 cuft, tuned to 32-34 Hz. 80-100 sqin of port. Makes a great daily box.

Who cares!!! OP - The issue is that as your port becomes longer to lower the tuning, the net volume becomes lower, making the tuning higher than you calculated. Your port has to be even longer than you calculated, which will further lower the net volume and again not give you the tuning you calculated. It is an iterative process (along with a little predicting) to get you where you want to be. In your design, you can only go .75" deeper, then you will have to turn up. I am also confused on your current design - I come up with well over 4.13 cuft net volume. What is your sub and bracing displacement? How thick is the baffle? Using 14.5 x 26.5 x 28.5 = 6.34 cuft Port - 26.5 x 3.25 x 25.25 = 1.26 cuft Leaves 5.1 cuft. Where is that 1 cuft going?

I was told by a SPL competitor that uses DD that the coils they give ~16-17 mm Xmax (cannot verify that myself). I would guess it is off by more than a few mm, or they would just advertise the true Xmax. Not bashing DD subs, they are great subs. I was just trying to answer the OP's question. Like the old MT's. Short BL Xmax figure, but so much motor force you could throw them beyond the gap without any problem.

Something is wrong - how is the port 21" tall if the box is 21" tall?? The port is 19.5" tall. Edit - I see you posted while I was calculating. So is the box 40 x 21 x 19 external?

Joe X - you are trying to make too much out of the center port. I have built both ways at least 20 times each. The center port is awesome for music and allows for a nice symmetrical design.

I think DD uses suspension travel because it is not the true Xmax. They run out of BL before the "suspension travel" rating. The BTL is a true 28mm Xmax. Still 70% BL at 28mm one way excursion.

You can sometimes have issues with unequal excursion between the 2 subs if you have them on one side of the baffle and the port on the other. One chamber is fine, but if you are just building it for daily, put the port in the middle of the box between the 2 subs. you might lose a very small amount of SPL, but it will not be noticable.

That is why I said more power

You are throwing more power into it when you are playing the lower frequencies.

Playing below tuning does not thermally blow the sub, it rips it apart mechanically if you have enough power. Like playing it free air.

A lot of bad info here. Caps are polarized, not resistors. As long as you use a non-inductive resistor, it will not affect the signal or frequency response. If you created a coil from wire, you have created an inductor, which will change the frequency response. The correct answer to the OP question should be: Even if you parallel enough resistors to do this, it is a waste. Let's say you have an amp that does 500 watts at 4 ohms and 1000 watts at two ohms. The 4 ohm sub gets 500 watts. Add the resistor in parallel (and assume it is VERY high power), and your amp now outputs 1000 watts. But guess what - 500 watts goes to the sub and 500 watts goes to the resistor. Nothing gained but some additional heat and stress on your electrical.