MatthewMartin

I'm building an SPL box for 2 12 cvr's in a 06 Impala. He wants the port to face into the cabin. Sd of both subs is ~165 sq in. I've been told to use up to 100% of Sd. Here is where I'm running into some difficulties. Both subs and 165 sqin of port can't fire into the cabin. There isn't enough room. The most port area I can get is ~65 sq in this way. If I tweak the placement of the subs, I can get all 165 sq in of port firing into the cabin. This requires me to place one of the subs on the side and one facing into the cabin. I worry about phase issues with this but those may be negated by the sheer amount of port area. I also wonder whether having both subs facing into the cabin will make much of a difference than moving one to the side. Have a quick look at the designs and tell me which is better suited for his application. Both these are 3.5 cubes at 48hz.

I just got back from a show and managed to hit a 146.5 dB in my 1993 MX3. Not bad, I know she has a few more dB's in her. I want to tweak seat position/box position/everything else but I really want to avoid spending a lot of cash at my local shop for Termlab time. Can I buy a cheap radioshack SPL meter and adjust my setup with the volume down low so it'll fall below the 120db limit? I know it's not accurate but is it precise enough for testing purposes?

I'm sorry, but asking questions like this with the setup you've listed, don't coincide. Here's problems I see already.. Not enough information: We need dimensions of your box and port. Most first attempts at SPL setups get this wrong. Also firing direction and orientations. Tuned too low for an SPL setup: You say it peaks at 50, but that's a result of your tuning. SPL setups should be higher. Chances are, your port is too small: See above 4 gauge wire? Really?: Although the runs are short, you are considering a .5ohm burp. Upgrade. Wrapping a box in "duck tape" (try to flame me): Why did you wrap the box? Because somebody told you to? Please help us help you. I'm not trying to be a dick, but from what I read, you're pretty confident in yourself and only want three answers that really don't apply unless we know what we're working with. I'll try to answer your questions the best I can, then further explain our situation in more detail. We need dimensions of your box and port. Most first attempts at SPL setups get this wrong. Also firing direction and orientations. Box is 5 cubes. 45hz. The internal height is 16.25 inches. The port is 5 inches wide. Port area then comes out to be 81.25 sqin. This equals 16.25 sqin of port/cuft. The sub faces up, and the port sideways. The box is a very tight fit in the cargo area of the mx-3. There is no space between the back and front walls. There is a recessed pocket of space that the port fires into. The same pocket on the opposite side houses the optima redtop. Tuned too low for an SPL setup: You say it peaks at 50, but that's a result of your tuning. SPL setups should be higher. The car's peak frequency was found using a sealed box, not the result of any tuning. Ideally, the sealed box would have taken up the same amount of space in the cargo area as my SPL box, but that wasn't the case. This probably threw off the "true" peak freq. for the car. To what extent is another story. Chances are, your port is too small: Possibly. When I designing, I was under the impression that the bigger the box, the more efficient it becomes. Because of this, I put net cuft. first, and port area second. The idea was to use up as much volume as possible. The result of this is 16.25 sqin. of port per cuft. On a related note, our local installer said we should have used a smaller box. This surprises me since the response curve on winisd shows more output with a larger box. 4 gauge wire? Really?: Although the runs are short, you are considering a .5ohm burp. Upgrade. Agreed. We weren't considering burping at .5 ohms until just recently. If the electrical can't handle it, we will make due with what we have now. Theoretically, the 3000d puts out 3000w at 2 ohms and the 1500d puts out 3000w at .5 ohms. What is the difference in 3000w at 2 ohms vs. .5 ohms? Keep in mind we had no problems running the 3000d at 2 ohms. Wrapping a box in "duck tape" (try to flame me): Why did you wrap the box? Because somebody told you to? Yes. That's exactly what we did. We wrapped the box in duct tape under the advice of a local stereo shop installer who said that he's seen dB gains everytime. In no way do I want the answers I expect. I'm probably way off in some aspects of this build, but that's OK as long as I can learn from my mistakes. Based on the design above, where would you place the 45s?

This is the OPs buddy. The port is pretty large the way it is. I don't remember the port area off the top of my head but I know its more than enough for an SPL setup. I had another thought. If we run the ap3000d, we must compete in the stock 601-1800 class. We have an Ap1500 that we could use instead dropping us down to the stock 0-600 class. From here we could run the 1500 at .5 ohm to stay competitive. Thoughts?