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bman8891

(2) xl12's box as backseat port help

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I have not built it yet but the box is acting as the back seat so it has to be a pretty specific size

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also, would I be better off firing the port forward and turning it inside the box or firing the port to the side and loading off the back door?

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I have not built it yet but the box is acting as the back seat so it has to be a pretty specific size

So next question, have you bought the subs yet? Given your space constraints you would probably be better served by 10"s.

Another thing to think about, based on the amount of power you are going to be running your box really should have a double baffle and some bracing. Both of which are going to further eat into the amount of net volume you have available.

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I have not built it yet but the box is acting as the back seat so it has to be a pretty specific size

So next question, have you bought the subs yet? Given your space constraints you would probably be better served by 10"s.

Another thing to think about, based on the amount of power you are going to be running your box really should have a double baffle and some bracing. Both of which are going to further eat into the amount of net volume you have available.

Yeah I already have one of the subs which creates a new problem because its a d2 so if I get another I will have to run my amp at 2 ohm. Maybe I could get two amps that can be strapped?

It will be triple baffled since the subs are inverted it will be a lot of strain on such a narrow box and as far as bracing I was just going to put aDowell rod in the center 3/4 mdf should span 13" fine.

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So do you think if I went with a slot port like this it would be better? I got my port area from 28 to 50 but now my tuning is a bit too high.

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If I did that it would be over 20 square inches of port per cubic foot and my ports would have to be like 6 feet long. Remember how small this box is everything I've seen says 1.5-1.75 per xl12.

Your box is a perfect example of why "port area per cube" rules don't always work out. I've built plenty of boxes with over 20 sq in of port per cube, it all depends on what the application requires. You are going to be putting 4k watts into this box, that's going to move some air and you need to facilitate that or your output is going to suffer significantly.

To put things in perspective, Sundown recommends 40 sq in of port area per sub for their Zv.4 12"s. A single 6" aero port is 28 sq in, so you have 14 sq in per sub. Does that sound like a recipe for success?

I know there are other people here who are saying they've run similar setups with a single 6" aero, but here's the problem, how do you hear the output you aren't getting because your port is too small? You can't. Port compression isn't always audible, but you would sure as hell hear the difference if it wasn't there.

Not sure what the Sundown subs you mentioned have to do with DC Xls he's going to use.

I was quoted 9-12 areo for 12 xls from DC. I agree with you that more port might give more output, but how will the afffect daily?

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Not sure what the Sundown subs you mentioned have to do with DC Xls he's going to use.

I was quoted 9-12 areo for 12 xls from DC. I agree with you that more port might give more output, but how will the afffect daily?

I picked the Sundown sub as an example because Sundown is one of the few companies that gives an actual port area recommendation, not just the typical "x sq in of port area per cube".

I picked the Zv.4-12 because its a roughly equivalent sized sub in terms of RMS power handling. I know it's not a perfect comparison, but 14 sq in of port area (using one 6" port for two subs) isn't anywhere near the 40 sq in Sundown recommends for their sub.

This isn't the only information I'm going off of for my recommendation either. I'm also going off of my experience, and I also use box modeling software to see what kind of port velocities the OP is going to get. With a single 6" aero velocities peak at almost 80 m/sec, above 33 m/sec is when bad things start to happen and lower is better. Even if software is off by 25% (which I doubt) port velocity will still be way, WAY too high.

The reason this affects daily use is primarily, you aren't getting what you pay for. If you lose 5 db to port compression, you are paying for a 4000 watt system, but only get roughly 1500 watt performance, if that even. Also there is a really good chance you will get port noise like crazy, so not only are you not getting the performance you paid for, you get some really annoying port noise you didn't want.

Now the 5 db loss is just a number, I can't tell you exactly how much output is going to be lost to port compression, I wish I could. I do think that 5 db probably isn't unreasonable though.

Edited by Triticum Agricolam
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So do you think if I went with a slot port like this it would be better? I got my port area from 28 to 50 but now my tuning is a bit too high.

Honestly, I think you should sell the one 12" you have, and then buy two 10"s. That will fix both your space/port area problem, and your impedance problem.

If you are determined to stick with 12"s, you are going to have to make design compromises somewhere. Ideally you should use at least 80 sq in of port area, with 3 cubes of net airspace, tuned to the low 30's. Since you don't have space for that, you are going to need to sacrifice somewhere and it is going to cost you performance one way or another. First thing I suggest is you don't use a triple baffle, a double baffle will be fine. Since the box is narrow that actually makes it stronger. Getting rid of that third baffle should gain you some space.

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Not sure what the Sundown subs you mentioned have to do with DC Xls he's going to use.

I was quoted 9-12 areo for 12 xls from DC. I agree with you that more port might give more output, but how will the afffect daily?

I picked the Sundown sub as an example because Sundown is one of the few companies that gives an actual port area recommendation, not just the typical "x sq in of port area per cube".

I picked the Zv.4-12 because its a roughly equivalent sized sub in terms of RMS power handling. I know it's not a perfect comparison, but 14 sq in of port area (using one 6" port for two subs) isn't anywhere near the 40 sq in Sundown recommends for their sub.

This isn't the only information I'm going off of for my recommendation either. I'm also going off of my experience, and I also use box modeling software to see what kind of port velocities the OP is going to get. With a single 6" aero velocities peak at almost 80 m/sec, above 33 m/sec is when bad things start to happen and lower is better. Even if software is off by 25% (which I doubt) port velocity will still be way, WAY too high.

The reason this affects daily use is primarily, you aren't getting what you pay for. If you lose 5 db to port compression, you are paying for a 4000 watt system, but only get roughly 1500 watt performance, if that even. Also there is a really good chance you will get port noise like crazy, so not only are you not getting the performance you paid for, you get some really annoying port noise you didn't want.

Now the 5 db loss is just a number, I can't tell you exactly how much output is going to be lost to port compression, I wish I could. I do think that 5 db probably isn't unreasonable though.

Thanks for the knowledge.

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So do you think if I went with a slot port like this it would be better? I got my port area from 28 to 50 but now my tuning is a bit too high.

Honestly, I think you should sell the one 12" you have, and then buy two 10"s. That will fix both your space/port area problem, and your impedance problem.

If you are determined to stick with 12"s, you are going to have to make design compromises somewhere. Ideally you should use at least 80 sq in of port area, with 3 cubes of net airspace, tuned to the low 30's. Since you don't have space for that, you are going to need to sacrifice somewhere and it is going to cost you performance one way or another. First thing I suggest is you don't use a triple baffle, a double baffle will be fine. Since the box is narrow that actually makes it stronger. Getting rid of that third baffle should gain you some space.

Space isn't an issue I can go wider to 15" and a hair taller but then I'm over 4 cubes and those subs only want 3-3.5 cubes for the pair. My problem is the shape of the box wont let me fit 2 6" aeros. If I stretch it a little I can fit 3 4"aeros. That might be my best ccompromise to staying under 3.5 cubes but thats still only 37 inches of port area. Im sure I can make this work somehow, I wont be competing at all just want to turn some heads.

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