Limited Space but want 2 15's...

[Chase Wallace]

Thanks guys. I'm going 2-3x over the budget I had in mind for putting some bass in my truck but I bought this amp on sale.

Sound Magus vs3500.1 On the amp dyno it did 3930 Certified with the voltage dropping to 13.95 volts so it seems to be a solid 4k RMS amp at 14.4 volts. I know there are better amps out there but this one seemed like it was really good dollar per watt RMS with the sale they had going on. I'll leave the link to the full amp dyno video down below.

I've been really busy with a few projects and fighting the weather so I haven't had time to get accurate measurements inside the truck yet. I hoped to do it today but got carried away trying to get the water running back at my house as the weather froze/busted my water well pump. Anyway, like I keep saying, I'm open to other ideas and subwoofers. I just have the Sundown X v2 15's in sight right now and if space turns out to be an issue for them then I guess I'll drop down to the 12" model which I think should fit pretty easily with all the modifications I plan to make. If anyone thinks another combo might get louder then please let me know. So far I'm just tied into roughly 4k watts RMS @ 0.5 ohm.

[Chase Wallace]

I finally got time to get some better measurements yesterday and wrote them down to do some airspace calculations. I used the12volt.com and 0.75 wood thickness to give me the internal airspace. These measurement's might not be exact but they should be real close. One thing I needed to know was how much clearance should I give the face of the subwoofer to the bottom of the floor for the X v2's. I calculated it at 3 inches off the floor. Anyway the measurements I got were...

3.73371 for the front console part of the box at a medium height of the existing console/arm rest.

6.18438 for the bottom seat part of the box

2.86914 for the seat back part of the box

Total 12.78703 minus subwoofer displacement gives total internal airspace available 12.34703 cubic feet.

Copied from Sundown's website the recommend box spec's for a Sundown X v2 15" are...

Ported          4.25 ft^3

Recommended Tuning        32hz

Recommended Port Area    68 in^2

 

 

So do you guys think we can make it happen with that? Can anyone help me figure out the airspace and porting? I can make slight changes and build the box to have less airspace or even squeeze a little more out of it but it doesn't look like that will be needed. Any help would be greatly appreciated! I ordered another 100 square feet of sound dampener material so I can get the area's where the box will sit before it goes in. I'll take pictures and post once I start getting the build going.

 

[Chase Wallace]

While looking over the airspace requirements for different subs it also looks like I could run 4 SA-12v3's     Recommended Displacement 1.5-2.0 ft^3 @ 35hz

This would give 100 more square inches of cone area and the recommended airspace for 4 SA-12's would actually be very slightly lower than the 2 X 15's...What do you guys think? The cost difference isn't much given the X series cost about twice as much as the SA's.

 

[ShadeTreeMechanic]

One thing to look at is the fs. The 3db down point on the response curve is calculated directly from this.

[Chase Wallace]

4 hours ago, ShadeTreeMechanic said:

One thing to look at is the fs. The 3db down point on the response curve is calculated directly from this.

Interesting, I don't have the best box building program [WinISD Pro Alpha if someone can help me get it working where everything looks correct] and really don't trust it because it doesn't seem to work right for me when entering all the parameter's or I can't find all the parameter's, I'm really not sure but basically I really want this done right. This might be a small setup to some but it's going to be by far the most expensive setup I've ever had and unless my life changes where I have more money it will probably be the best I've ever had so this is my last shot to really do one right and I think it will really be cool to have it all packed into my extended cab without loosing the back seating area. I'm really hoping someone can help me model the difference between the two boxes and get the airspace right. Any reduction in the required airspace would just help me so the 4 12's with the extra cone area and slightly less space requirements sounded good as they should also work well with my amp. I haven't taken apart my drivers side door that doesn't open on the 3rd door truck but I was hoping to put a 2nd battery there and build the amp rack either into the bottom of the seat or the back wall of the seat and need to know what kind of port arrangement I'm going to have because I might need to slightly accommodate the box for that as well. I could eek out a little more box space if needed but when I started getting near 13 cubic feet when calculating I really hoped that would be more than enough.

Here is the fs of both subs.

SA-12 fs (Hz)  33.71

X v2  fs (Hz)  29.6

 

I guess now I'm asking a lot but if anyone could run these two subwoofer's through a good box building program using what you think would be a good airspace withen the amount I have available it would be extremely appreciated! I have a couple places I think I might be able to put the port or ports for the box but both seem more suited for aero ports due to the odd shape of the box design.

[DLHgn]

Keep in mind that the more cone area and power you're running the more port area you're going to need and thus taking up more air space. 

[Chase Wallace]

On 1/2/2017 at 4:53 PM, DLHgn said:

Keep in mind that the more cone area and power you're running the more port area you're going to need and thus taking up more air space. 

Right, I understand that but good note. I measured pretty close but still think I could squeeze a little more airspace out of it if needed but really it seems like I have enough to hit the recommended volume plus a little extra left over considering I'm about 4 cubic feet over recommended without accounting for port volume.

So I don't claim to know what I'm doing with this program. The last time I used a box building a program I was ~16 years old and it already had the T/S parameters of the subs we were using so I didn't have to enter them in. Today I tried my best to enter in the parameters I could find for each sub and compare the two setup's I have in mind using WinISD beta.

I modeled both the two X 15's and four SA-12's in a 12 cube box tuned to the recommended 32 and 35 hz. I'm not sure if I did everything correct or got the parameters correct. It seems to me that the T/S parameters listed on Sundown's website are for the original SA series and not the SA v3 series. I question if the same isn't true for the X series. I suppose the biggest shocker the gain plot showed me was in how the two setup's rolled off from the port frequency. The 15's having a sharper peak and dipping below the negative gain line kind of surprises me. The 4 12's gained a little more at the tunning frequency as I expected but also look less peaky having a larger gain curve and not dipping into the negatives. The port area the calculator says is acceptable also seems like it's off to me. A single 8 inch is giving a vent mach of 0.09 for the 4 12's and 0.10 for the 2 15's. Of course I played around with different sizes and numbers of ports but the only change he program showed me was in the vent mach and port length. I don't quite understand enough yet to know if the number's the program gives me are correct. Basically the only thing I know about vent mach is that you don't want the number too high to avoid unwanted port noise.

This was for comparison purposes only and I'm sure the end design will be slightly different. I just hoped to get something mocked up to compare the two setups and hopefully get some advice or have someone show me what if anything I'm doing wrong with the T/S parameters and this program.

[Chase Wallace]

It's pretty clear to me that I don't understand much about port area. I'll be searching and reading what I can find about it but I guess what's confusing me is the need for more port area than require to keep the vent mach or airflow speed low enough. I don't claim to know what low enough is other than going off what the box design programs I've used say are good enough which has been a mach number of 0.16 or lower from what I remember and this program is showing.

 

The only thing I can think of that would give me enough port area (correct me if I'm wrong) would be to use the back wall with a 50" long 3" wide 7.56" deep slot port. 150 square inches of port area taking up 0.65625 internal space before the wood needed for the walls. This would still allow for quite a bit more airspace than recommended. The subs would all be firing down and the port up. Does anyone see anything wrong with this type of configuration? The only others that I can come up with that give me enough cubic inches of port area would be too long and would have clearance issues with the subwoofers plus take up much more of the box volume itself so unless I'm just not picturing something in my head that would work...well the 4 12's would be out simply because the ports would need to extend into them.

 

[reedal]

this thread may help you get a better understanding.

https://www.stevemeadedesigns.com/board/topic/189867-understanding-ports-a-lesson-in-dimensions-vs-efficiency/

[Chase Wallace]

14 minutes ago, reedal said:

this thread may help you get a better understanding.

https://www.stevemeadedesigns.com/board/topic/189867-understanding-ports-a-lesson-in-dimensions-vs-efficiency/

Thanks, I just finished reading that first post you linked about 30 minutes ago. There is some VERY technical information in there but I do understand a little more after reading that but most of what I got out of it was about how it can increase efficiency (which I guess the size and number of subs wouldn't matter if there wasn't really a limit to the efficiency linked to a sub's output)...Good read, some stuff a bit over my head but I do feel like I learned some stuff and plan to incorporate a few of the tricks into my port design. 

Now I'll start on the second link you posted...and/or perhaps finish it tomorrow because I just realized how late it is!

 

On another note, can anyone give me any thoughts on the port design I mentioned? Using a long slender port along the back wall is about the only way I can think of to get the port area I would need for either combo I'm wanting to run. I've noticed some people using things like dowel rods inside of their port to brace the port. Is there any way to know how bracing a port like this would effect the tunning?