DiyMobileAudio.com Car Stereo Forum banner
1 - 18 of 18 Posts

·
Registered
Joined
·
2,138 Posts
I did some quick calculations and at 5.52 cf net tuned to 32 hz I could go up to 72 square inches of port that would be 50 percent more port area. Will that meet our goals? My usable dimensions are 29.5 wide internal 14.5 high internal 28.5 deep internal.
Going bigger on box size creates box gain at the tuning frequency and a concurrent increase in excursion as well. Gives you a "one note wonder" at the tuning frequency and if coupled to cabin gain is the normal practice for SPL burps for maximum SPL at one frequency at the expense of all others.

With all that being said - what you want is to shoot for about 2.5 cuft airspace and use the rest of space for a folded or labyrinth port tuned in the 28-32Hz range. You don't need more than 50-60 in² port area even at 2kW per driver.

Sent from my SM-G965U using Tapatalk
 

·
Registered
Joined
·
2,138 Posts
Truth be told I'm running 400 watts probably after box rise because I'm using a Phoenix gold xenon 400.1 which makes the same power between 1-4 ohms. Based on a previous setup I had in the car I'm probably hitting 128 dB right now. The car is a 2019 Nissan versa sv horrible for spl from what I can tell. I Have a tramps bass 3 k that does that power at .5 ohms which would work with my two si sql 12s since they are both d2 subs but I'm going to use a dmm to dial them back to 2 k total.
My Single SQL12 sealed in 0.85 cuft net on Taramps Smart 3k at 2 ohms for the full 3kW output has been fine for a year now. I don't rave with it and I know what "hot coil" smells like so I throttle back and give it time to cool between runs - I DO NOT recommend running a single SQL12 on 3kW for more than a song or two without time to cool between. But with that being said you need to try more than 400W before deciding to go ported. Ported is fine and the last box you posted:
ok another calculation 3.84 cf net total with a port 14.5 x 6.5 equaling 94.25 square inches of port with 3.25 end correction for the turn in the port and the total needed port length is 53.5 minus that 3.25 equals 50.25 total inches of port length that gives me 7.75 inches from the nearest wall of the enclosure and ends up with a tuning of 32 hz. So each subwoofer will see 1.92 cf net. Hows that look?
1.92 cf net each at 32 Hz would absolutely pound at the port frequency and work just fine even on 1.5kW per Sub as long as you keep an eye on thermals.
 
  • Like
Reactions: ItsonlyaHONDA

·
Registered
Joined
·
2,138 Posts
I've been running ported boxes forever and considering building a box for a couple of these sql-12's... I've had the same dual 12" kicker comp ported prefab for like 14 years and at this point it is the 'lowest' part of my system. It has been taking 900rms for a while and really pounds (and gets low with some eq), but it struggles with really fast passages. It sounds great for rap, of course, I listen to all types of music. Do you think 2 of these 12's in a sealed box would really do the trick?
If you've never used a sealed, infrasonically capable sub in your ride then you owe it to yourself to at least try. The extension, accuracy, detail (especially on those "fast passages") and overall sound that you get from the subharmonics and undertones that a properly tuned, sealed Sub like the SQL12 will give you has to be experienced. No graph or empirical data can suffice. You've already got a single sealed and the amp to do testing. Try the single you have on 3kW (be careful) and know that adding a 2nd sealed will increase the output 3-6dB (depending on loading, cabin gain, etc.) Additionally, if you put them each in their own 1 cuft sealed prefab enclosure on 3kW shared and that's not enough output (or TOO much infrasonic output due to cabin gain) then you'll KNOW that by going flat SQ ported you'll have similar response but additional output down to the port frequency. If that's still not enough output or too low, then you can continue to raise the port frequency in the simulation till you get the increase in output or the low frequency rolloff you are looking for... a properly tuned ported enclosure can be just as accurate as sealed down to about 1/4 to 1/3 octave below the port tuning but below there it will have virtually no output. My son used a 2 x 12 Kicker Comp Ported prefab (the entry level one with the huge flared port in the side) and while it had WAY more output in the 40-80Hz range vs my sealed SQL12, the output below 40Hz was what sold him. He's actually running dual Dayton 10HO (what I had laying around in the shop) sealed now while he saves up to purchase an SQL(s).
 
  • Like
Reactions: ItsonlyaHONDA

·
Registered
Joined
·
2,138 Posts
I just ordered a 500 Farad cap bank for under the hood as well.
The closer you install this to the amp the better...

Sent from my SM-G965U using Tapatalk
 

·
Registered
Joined
·
2,138 Posts
Duralast Platinum AGM Starter battery under passenger seat - OEM 240A Alternator - XSPower 750 AGM on the amp board to 1,200W of Class AB and 3,000W of Class D all on 1/0 OFC Welding Cable and no voltage drop (but no burps either.)

2 x 40AH LTO is not much reserve - the 500F Capacitor will stabilize the peaks but keep in mind that 500F = 3.6-5.2 Megawatts of potential energy (at 12-14.4VDC) so make sure your wiring is up to the task of carrying the full ampacity of your amplifier as your likely to be running off the Capacitor during burps.

Sent from my SM-G965U using Tapatalk
 
  • Like
Reactions: ItsonlyaHONDA

·
Registered
Joined
·
2,138 Posts
Would i gain anything by running an agm under hood with the isolator and the other two lithiums and cap bank? Id imagine some because the agm would take the amps that the car needs to run basic electrical?
Yes, the AGM under the hood (especially a Low Internal Resistance one) will help immensely. Regular SLA batteries and even AGM's designed for starting specifically have higher internal resistance to raise the voltage during discharge events which helps keep your voltage more stable but restricts the amount of current available.

The isolator is only necessary if the batteries have different float or resting voltage to keep them from feeding off each other. I have one in my install though, even though it's not necessary.
 
  • Like
Reactions: ItsonlyaHONDA

·
Registered
Joined
·
2,138 Posts
I did some reading and i have lto lithium cells that can rest at 14.8 volts how can I limit the charge on my lithium charger so it rests at 14.8 volts?
Your "Lithium Charger" would have to be specified - most Chargers built for Lithium Batteries are 'intelligent' chargers that recognize the float voltage based on current flow and automatically switch to trickle or float charging at the correct voltage.
 
  • Like
Reactions: ItsonlyaHONDA

·
Registered
Joined
·
2,138 Posts
I figured out I can fit a 10 inch Octoport and that will be good for like 81 square inches of Port and gives me 5.25 cf net for both subs.
5.77 cf net with 81 in^2 port tuned to 32Hz = 29.39" port length, 22Hz LR4 HP and 12kW before xmax
Port Velocity at xmax is 50 m/s which is a tad high but fine for SPL and 131.7dB at 34 Hz non-anechoic.
Rectangle Font Line Screenshot Parallel


Rectangle Slope Font Parallel Screenshot


Rectangle Slope Font Line Parallel


Rectangle Slope Font Screenshot Parallel
 
  • Like
Reactions: dodgerblue

·
Registered
Joined
·
2,138 Posts
Ok this thread isn't done. I just came up with the idea to build a 3.00 cf net tuned box with a Dayton 12 inch passive radiator with 26 mm of Xmas and tune it to 24 hz. That would give me sq and nice lows and more spl from the subs and with a pair of them and 2k clean power they will bump. Anyone know if a pair of them would be OK with that passive radiator if I burped them on 3k
You "might" get by with 2 x 15PR for each SQL12 or one of the Earthquake huge xmax units but generally you go up one size to start with... if you've got the baffle space for 2 PRs per SQL12 then maybe.

Sent from my SM-G965U using Tapatalk
 

·
Registered
Joined
·
2,138 Posts
2 x SQL12 in 3 cuft with 2 x RSS315PR = they hit xmax at 900W (450 per driver) while only utilizing 29.4% of the driver's exursion (8.4mm)
Rectangle Line Font Screenshot Parallel

Rectangle Slope Font Line Parallel

Rectangle Slope Font Line Screenshot


At rated RMS of 1000 per sub the PR are trying to hit nearly 38.5mm...
 

·
Registered
Joined
·
2,138 Posts
The earthquake pr's hit 4 inches of xmax i think will one per sub work if thats the case?
Depends on the Vas, Qms, Mms and Sd but unfortunately they don't publish their specs.

Edit: they've updated their cutsheet to include the specs needed to model...

But the xmax is both ways so the one-way is 2" or not quite double the Daytons and with the higher Fs and Vas they still can only do so much with the SQL12.

2 x SLAPS M-12 with 300g of added weight per PR in 3 cuft hit xmax at 1,850W (925W per Sub) or 43.8% of xmax on the SQL12 (way better but still leaving alot on the table.) So if you wanted to stay under their thermal rating it is doable but if you're planning to push 2-3kW per Sub you'd need 4+ of the Daytons and at least 3 of the M-12s.
Rectangle Slope Terrestrial plant Font Screenshot
 

·
Registered
Joined
·
2,138 Posts
They provide a graph at that link also for up to 1.5 cf. If i understand correctly it would tune to like 22 - 23 hz with zero weight added in that air space. Am i right?
That's where I got the data for the model... I'll look at 1.5 cf in a second.

OP was looking for 3 cuft and maximum boom which ended up being 4 x M12 PRs each with 600g of weight added to handle 6kW without reaching xmax on either the drivers or the PRs:
Rectangle Font Line Slope Parallel

Rectangle Slope Font Screenshot Parallel

Product Rectangle Slope Font Line
 

·
Registered
Joined
·
2,138 Posts
They provide a graph at that link also for up to 1.5 cf. If i understand correctly it would tune to like 22 - 23 hz with zero weight added in that air space. Am i right?
Single SQL12 with a Single M12 (no weight added) in 1.5 cf = 51 Hz
Rectangle Slope Font Line Screenshot

Rectangle Slope Font Line Screenshot
 

·
Registered
Joined
·
2,138 Posts
Single SQL12 with a Single M12 (no weight added) in 1.5 cf = 51 Hz
View attachment 339929
View attachment 339930
Adding 300g of weight to the M12 takes it down to 25.6 Hz and is acceptable tuning but is PR xmax limited to 900W.
So it's acceptable (especially if you want to stay under the Thermal RMS rating) but having heard and used the SQL12 on 3kW daily it certainly leaves a lot of performance on the table.
Rectangle Slope Font Line Parallel

Rectangle Slope Font Line Screenshot
 
  • Like
Reactions: ItsonlyaHONDA

·
Registered
Joined
·
2,138 Posts
I decided to look online and see what i could find sealed enclosure wise and found a dual 12 box with a 1 inch front baffle that has 1.20 cf per chamber so 1.05 net per chamber after the subs and the dimensions are exactly what i needed to maximize space. So i saved some money too.

I've got one of these in the 1.0 cuft size - they are beastly and the bracing in the 1 cuft had to be "massaged" to make room for the basket and voice coil vent but you can't beat the price "IF" you've got the clamps and glue.
 

·
Registered
Joined
·
2,138 Posts
What if i doubled up the walls on the enclosure would that work as well to make a strong box? Or fiberglass the inside of the prefab box i bought?
I have used Line-X Bedliner spray to coat the inside of prefab boxes to keep from blowing them apart but you have to know someone who makes the "real" stuff and not the kind you buy in a can.

The problem with bracing most prefab boxes is you can't really install full width skeletonized braces without taking the baffle off so you end up putting in triangle braces or multi-piece braces and if not done correctly they can rattle loose. Some of the boxes that I've been asked to "fix" had so many holes in them from drywall screws that were used to try and salvage a blown out corner or securing an angle brace and missed that it was easier to take the box apart and glue a new piece of MDF on in place of the damaged panel.

Doubling up the walls is the best idea but you have to take off whatever they put on the outside (carpet, vinyl, paint, etc.) and sand it down to the MDF so you can glue the panels you add to the existing enclosure. Gluing the entire mating surface so they become laminated together is what creates the strength. But if you have the tools to make the panels for doubling then you can make your own enclosure and do the internal bracing correctly. You don't have to Dado every mating edge to make a strong joint (it does help because it makes more glue surface and stabilizes the joint so it is easier to make that joint straight) just realize that it takes multiple days to glue up one enclosure as you wait for the glue to cure before proceeding to the next panel.
 

·
Registered
Joined
·
2,138 Posts
for my dual 12 box i used somethign similar. PE sells the "kit" version too. Its all the bracing plus the double baffle. This gave me the ability to buy 2 of them, and then also custom cut everything to the box specs.
...and they sell blank baffle versions as well so if you need the 15" size knock-down for a 12" driver you can cut your own cutout.
 

·
Registered
Joined
·
2,138 Posts
Ok im trying here what about threaded rod across the front and sides of the prefab with a thick washer to draw it in. If this cant work i will have a box built just trying all my options.

This is the enclosure i bought.

Not that putting spreader turnbuckles or threaded rod and self locking nuts wouldn't help but you really want to be able to spread the bracing out over a large area and triangulation from perpendicular sides is what really solidifies the enclosure.

You "can" brace that enclosure but it's complicated. First you have to have spreader clamps so you can push out on the braces and force them into the sides. You cut braces that are the same depth as the box and thick enough to match the cutout hole. One at each midpoint of all 4 sides on each side. Then you cut cross braces that will fit between these side braces very tightly and cut slots in both of them so they interlock then glue them in all the way at the back. Hopefully that makes sense?

You'll also want to cut full depth 45⁰ braces for the corners as well to reinforce those glue joints.

Sent from my SM-G965U using Tapatalk
 
1 - 18 of 18 Posts
Top