sound quality ported box design

[wilkes5]

Would like help designing a box for a single OZ superman 300L 12 inch subwoofer (oldschool car audio). Specs given on the sub....

Oz superman 300L 12's

Fs---20.1
SPL dB/1W/1M---91
Qms---2.395
Qes---0.460
Qts---0.386
Re---3.2
Le---0.35mH
Xmax---10mm
Mms---79.3g
Vas---0.326 cubic M/ 11.51 cubic feet

The manufacturer suggested ported box max is 4 ft^3 for a single 12.

Not sure if the sub is best for ported boxes? Have experimented building SQ ported boxes in the past, and it seems to me the setup which gives the best sound (to me at least) is to build the box a little bigger than max recommended, and tune really low (high teens / low twenties). A website also explains such procedure for SQ ported boxes...(because some guy tried to tell me it doesn't work).

Also, would like to know what the best subwoofer design software is. LEAP looks pretty cool. Does anyone use LEAP to charge customers for box design plans (don't feel like shelling out $700+ for a single box).

 

[OscarS]

The first thing you need to do to evaluate the manufacturer's suggestion is to create a simulation with your favorite enclosure modeling software. You need to properly evaluate FR vs gain (or raw SPL), cone excursion, and group delay plots.

Part of the reason that the setup you describe sounds "good" is because since the box is so large, and the tuning is so low, the driver for the most part ends up working in a 'sealed box', since the vent only operates over a very very tight freq. range of only a few Hz. This characteristically low tuning drives the group delay peak so low that it becomes a non-issue for the most part, just like a large sealed box does.

Not sure if the sub is best for ported boxes?

If you're asking because of the large volume recommendation, it is because of the very compliant suspension. To get a Fs of 20Hz with such a low Mms from a 12", the suspension necessarily has to be soft, and thus Vas gets huge quickly (Vas is proportional to compliance). You will need a large enclosure for this driver no matter what type of enclosure you decide to use. The Qts is in the mid-range so it can go either way with regards to that, but that low Fs makes the EBP < 50, so overall it tends more so to sealed and 4th order BP enclosures.

 

[wilkes5]

The first thing you need to do to evaluate the manufacturer's suggestion is to create a simulation with your favorite enclosure modeling software. You need to properly evaluate FR vs gain (or raw SPL), cone excursion, and group delay plots.

So, it's not as easy as plugging in the PS parameters into Winisd then tweaking the box size and reading the port dimensions? Don't have a clue so if you can take time to explain step by step...
1) evaluate FR vs Gain (raw SPL)
2) cone excursion
3) group delay (plots)

Don't really have a favorite software, guess Winisd. Wish could have someone knowledgable with building boxes like such give me a good design. Better yet, the same knowledgable person give me the best american made sub which will work for the such setup (oldschool or new).

 

[wilkes5]

The max recommended ported is 4 ft^3.

So was thinking have something around 5 ft, then experiment with different tube lengths to get the sound right. need a ballpark for tube diameter and length. then have a connection piece to connect different smaller length tubes for tunability.

 

[Andrew Eckhardt]

Model it in the software of your choice, Winisd is fine. Different softwares sometimes abitrarily pick which type of tuning is used or let you select it, but all that's going on there is trading different volumes and duct tunings, and usually you can look at the graphs to see what it does to frequency response, group delay, phase.. and get an idea what the various tradeoffs lead to. Qts .386 is on the high side for ported box and high Vas leads to a very large box which will force port tuning near driver Fs for maximally flat response. This is what you want for maximum bass extension and efficiency in stationary applications where size and weight don't matter. The recommend volume is another matter probably directed toward flat response in a more reasonable volume, taking into account cabin gain of the autosound application. Oversizing ported boxes and dragging the duct tuning below Fs will lead to a reduced frequency where total cone unloading occurs but bottom end efficiency falls and a further output dip shows up just above the tuning frequency, while group delay at the bottom increases. Oversizing basically not worth it, but you can look at all this by playing with the parameters in Winisd.

 

[wilkes5]

Oversizing ported boxes and dragging the duct tuning below Fs will lead to a reduced frequency where total cone unloading occurs but bottom end efficiency falls and a further output dip shows up just above the tuning frequency, while group delay at the bottom increases. Oversizing basically not worth it, but you can look at all this by playing with the parameters in Winisd.

Whatever oversizing does, it's the sound which is best to me for some reason. Have built lots of slot ported boxes, and it seems to work my taste (worth it!).

 

[wilkes5]

alright, going to go a little bigger than 5 foot and try to have an adjustable port, maybe let you guys know how it goes?

 

[bjorno]

Hi,

FYI.

b

 

[wilkes5]

YEA YEA YEA, nice job dude!! awsome info, however most of it is illiterate to me. did pick up on "Opt. BR Volume". And see, the real sq ported box is 3x as big as the max recommended. you don't understand dude, been trying to convice people all over the place how it sound great to build like such..and have met stiff opposition.


P.S. sweden? not good for legalization of Cannibis according to Wiki. love to smoke, but always what is right.