ported box for SQL 15 possible in my car?

[YaImCool]

I have a 2017 mazda 6 and I want to put in a SQL 15 to replace my current Fi Q 12. This will be my first time building a box so please bear with me.

my trunk is 36 inches wide, about 19 inches tall, and a bit over 30 inches deep. The trunk opening is somewhat small. The current box for the Fi Q is 35 wide, 17 deep, and 14 high. It take up the whole width of the trunk but there is a good amount of space to move the box back and forth in the trunk and it comes in and out of the opening easily.

Stereo Integrity's website recommends a 4.25 cubic foot box tuned at 22hz. I think I can fit 4.25 cubes, or at least close to it. But 22hz is too low for everyday music so I think im aiming to tune around 30-32hz. I plugged in some numbers to the subbox.pro website and got this:

https://subbox.pro/en/design/?bt=2&...=4&pq=1&rf=31&pd=192.32&pw=2&pa=290.34&pp=100

As you can see to get 4.25 cubes it shows dimensions of 35 wide, 17 high, and 18.3 deep. What I dont quite understand are the port dimensions. It seems I can change the "port area" field to basically whatever I want and still obtain the 31hz tune I entered. So what port area should I choose?

If I built the box shown would it be sufficient or am I doing this wrong?

Click to read more...

 

[YaImCool]

Also, I am wondering, is sub and port facing the trunk the best way to go? Should I be considering a different type of build like sub facing up and port to the side? aroe port?

 

[SlugButter]

Also, I am wondering, is sub and port facing the trunk the best way to go? Should I be considering a different type of build like sub facing up and port to the side? aroe port?

An aeroport design would bring overall box size down a little. I would face sub and port to the trunk and sound deaden the trunk lid.

 

[YaImCool]

I have already deadened the lid, trunk floor, and some of the trunk walls. Ive always been skeptical of these aeroports, is there any trade-off to them over a traditional slot port for everyday music listening?

 

[SlugButter]

I have already deadened the lid, trunk floor, and some of the trunk walls. Ive always been skeptical of these aeroports, is there any trade-off to them over a traditional slot port for everyday music listening?

Aeroports work fine for every day listening, unless you go way too small. I’m not a big aeroport fan unless I’m trying to save space.

 

[Bobbytwonames 5,000+ posts]

Just contact @Buck. This is his forum and he will get you all lined out. He knows his shitt!

 

[hispls 5,000+ posts]

It seems I can change the "port area" field to basically whatever I want and still obtain the 31hz tune I entered.

If your software is working you will notice that the port length will increase as you increase port diameter. This will be a juggling act between what fits, the tuning you pick, and of course keeping enough port area to avoid turbulence and have good performance.

You may get away with 6" flared round port, I'd say 8" would be better and you would gain a bit of efficiency going up to 10" round, but it's doubtful you'll fit that tuned so low.

 

[Buck 5,000+ posts]

30d x 19h x 36w is 9.9-10 cubes internally, 6 sides sides of .75" of wall thickness. That's a ton of room. 30-32 hz is a tuning that I personally like. 22 hz is very super low tuning. Your port area could be small; not saying it is. I'd have to design it to check on that, but you don't want too small of a port area. Some woofers do well with 10 in^2/cube of port area, but it's usually woofers that are tuned very low, or lower powered woofers.

 

[Wolv19D]

I had a couple Fi Q 12s many years ago myself and strangely plan to buy a couple SQL-15s in the next couple months. I have been doing a lot of modeling in WinISD for what it's worth to give me a general idea of how the sub performs without cabin gain coming into the equation. I am a novice at this so hope to learn more about cabin gain in the near future along with everything else.

Anyways, the higher you tune a box the smaller you should make it to keep it from peaking so much. So the 4.25 is at 22hz and at 32hz I would at least knock it down to 4 cubes and possibly all the way down to 3.5 cubes. The bigger you make the box the more efficient it will be and it will have a little more low end as well but like I said there is a trade off in that it has a bigger peak where it's tuned at. And the bigger you make the box the less power the sub can handle since it's more efficient.

How much power are you running? The SQL is rated at 1000rms but I have read on other forums of people running up to 3k daily on them but that's without continuous heavy bass tracks for extended periods. My guess is 1500 would be no problem and 2k would also likely be fine if it was clean power.

I am planning on tuning around 25-28hz on mine to have a very flat response for a more SQ oriented build to try out. But I also may build a box in the 30-32hz range to compare. Even at 32hz it isn't too peaky at tuning as long as the box isn't huge. The SQL's like small boxes and it would do well even in 3 cubes. But like I said I would likely do 3.5-4 cubes if you are doing 32hz or just say 3.75 cubes.

As for port area that is another area I am still learning about and every sub is different. Most places that have high xmax subs like these recommend at least 15 square inches of port per cube so at 4 cubes that would be 60 square inches. But that said many also do fine running lower then that at around 12.5" per cube or about 50 square inches total. Your 45 square inches would likely be fine but I couldn't say for sure. I'm not sure how much truth there is to this but I have read a couple people say more port area may allow a higher SPL to a certain extent but a lower port area may allow you to play below tuning a little bit better and possibly be more musical? Again I am not an expert at all.

But since the SQL's don't typically reach xmax until way past the 1000w then perhaps a higher port area would be better? I am guessing here and it could be the complete opposite. But if you just wanted to play it safe the standard 15" per cube almost every place recommends would be a safe bet. So 3.75 cubes with about 56 square in of port.

I highly recommend having Buck design a box for you if you are going to go through the trouble of building it yourself the extra few dollars to have him design a box is likely money well spent. He takes all of this stuff into account. But if you don't choose to go with him then play around with sub box pro a little to get even numbers for an easier build. If your trunk is truly only 19" tall I would likely leave as much room as I could above it for the air to get back to the front of the vehicle so a 16-17" tall box at most.

 

[Wolv19D]

Playing around with Sub Box Pro a little a box that's 17" tall needs 54.20" of port area to have an equal width of 3.5". That's what I mean by playing around with the numbers a little to get equal measurements. That would equal 14.45" of port so likely a very safe bet.

Also remember to add bracing to the box and take that into account using the sub displacement. The SQL-15 takes up .16 displacement but with bracing I would at least bump that to .20. You can add up your total bracing yourself to add to it and play with it a little to make the box come out in equal measurements.

To figure out bracing displacement you just multiply them together and divide by 1728. So if you used 4 pieces of MDF that are 2" wide and 15.5" tall you would do 2" x 15.5" x .75" = 23.25 then divide 23.25 / 1728 = .013 of displacement. So if you used that amount of bracing you would add the .013 to the sub which is .16 so the total would be .173.

Anyways with .20" of displacement for your sub and 54.2" of port area in 3.74 cubes at 32hz. A box that is 17" tall and 32" wide would need to be 19.75" deep. If you used more bracing and got it to .25 of displacement then that would make it 20" deep. It's easy to play with the numbers a little and if it doesn't come out dead perfect you can easily round up 19.98" to 20" when cutting there is no difference. The only thing I would try to get dead on is your port width.

If you have Buck design you a box you could have him do you one with a port that is about twice the normal width and doesn't go all the way up the box. So instead of a normal slot port that goes from top to bottom it would only go about halfway up but be twice as wide.

Check out this thread - https://www.caraudio.com/threads/my-ssa-icon-15-buck-box-build.606898/

 

[Buck 5,000+ posts]

If your trunk is truly only 19" tall I would likely leave as much room as I could above it for the air to get back to the front of the vehicle so a 16-17" tall box at most.

This is solid advice as a definite thing to watch for, especially in a trunk. Air has to be able to flow around a rear-ported enclosure especially, or else it’ll get stuck in the trunk. I’ve quite literally seen that happen, not too often, but have. The pressure gets stuck in the trunk, in between the trunk inner walls and the box outer walls.

 

[Buck 5,000+ posts]

Slot ports are better, overall, IMO. You can’t really adjust aeros by the 1/8” in diameter, so you get sort of the port area you want, but I like to get exactly the port area that works the best for any given situation. Port area really matters for musical playing.