best way to get 18-40 hz out of 2 sa-12's, suggestions

[devin171moto]

I've attached box specifications for reference. target tuning 29hz. (2003 gmc envoy 20H 42W 30D max dimensions) taramps smart 3 amp

I absolutely love this box. it slams from 25-40, my only disappointment being it drops ridiculously fast under 24hz (21hz the car has to be stopped for me to even notice the note is playing, subs excurt like a little or half xmax and turn dead silent. )

I wasn't expecting 140's at 20hz from a simple 3rd order bass reflex, but i thought It would at least be some decent vibration I dont have to pull over to feel.

questions: 1. is 2 12's even enough cone area to get decent pressure at 20hz?
2. i'm aware of fazing and the size of the 20hz wave making placement of port and subs complicated and crucial, how could this be adjusted for better deeper bass? (will run sweeps to find cabin peak soon)
3. can this even be acheived with a simple ported design? maybe changing to aero ports or increasing internal volume) or do I really need to be thinking about a 4th or 6th order?

please no "why would you even tune so low anyway songs don't have dijabndiqdb" comments. because I want to. and because I only really play edited music. deep rumble is what I want. I dont play over 40.

I understand I don't know much. but I'm reaching the limits of what I can learn from youtube and forum post research, as at this point most of it doesnt apply to my situation, I'm open to suggestions on learning more detailed box design theory. so please instead of telling me "do your research". realize that's what I am trying to do and point to where I can find that research. thank you all. I appreciate anyone's time

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[Lasherž]

I'm not very confident on your question in terms of increasing your box resonance range, but I figure it might be worth asking if you're using any bass boost? If so there's a roll off both above and below around 45hz, so you may be running into the back end of that that people don't usually notice.

 

[THATpurpleKUSH 5,000+ posts]

The subs get quiet at 21hz because they are beginning to unload and 21hz is barely audible anyway.

2 12s isnt much cone area to be playing below 25hz with authority.

You will need more cone area and subs with an inherently low resonance aka fs.

Look at 15s or 18s with a fs of 25hz or lower if you want to smash lows.

 

[devin171moto]

I'm not very confident on your question in terms of increasing your box resonance range, but I figure it might be worth asking if you're using any bass boost? If so there's a roll off both above and below around 45hz, so you may be running into the back end of that that people don't usually notice.

bass boost is off. lpf at 60hz and no subsonic (amp doesnt have one) it's set with a dmm to hit 1700 rms at volume 50 with a 40hz test tone. clamped 900 watts at 25hz shakes the car like crazy then by the time it gets to 21hz virtually no movement. it feels like engine idle.

 

[devin171moto]

The subs get quiet at 21hz because they are beginning to unload and 21hz is barely audible anyway.

2 12s isnt much cone area to be playing below 25hz with authority.

You will need more cone area and subs with an inherently low resonance aka fs.

Look at 15s or 18s with a fs of 25hz or lower if you want to smash lows.

this is what I was thinking the problem was but simultaneously was hoping I was wrong .
I was really hoping a 6th or fourth order would fix it.
to your knowledge can a proper 6th order at least give the car a good shake at 20hz? i'm fine with it being noticeably less powerful at 20, it doesn't need to move my steering wheel. just enough so I can feel when the beat drops from 26hz to 21hz. because right now it just feels like there's no bass note there. I don't care about a sharp drop off above 50 hz because I'm gonna get some good components for the 50 and above range.

If I have to get 15's I guess that will be the next plan. I have the power. but I would prefer to try a new enclosure to not only see if it works but to practice my design knowledge

 

[YukonXL04]

Your really screaming for some high power low fs 18s...

 

[Oldmang]

What vehicle do u have again?
U already tuned under 30hz and a 6th would be large.
Its extending to where it should at volume now so maybe higher excursion/power subs are the answer?
2 12s on like 5-7k in a 6th maybe sounds like might keep you happy this week.
Hey... We all want more but that 20hz life usually means cone area + big power.
2 Sa-12s?.. Maybe 2 X-12s on a badass 5k wired down or 8k @1 ohm for example.
Id grab some subs that'll SUB hard, handle big power and go.
20-40hz?
What u lookin for is within reach (i think) but $ is the answer at this point imo.

 

[THATpurpleKUSH 5,000+ posts]

this is what I was thinking the problem was but simultaneously was hoping I was wrong .
I was really hoping a 6th or fourth order would fix it.
to your knowledge can a proper 6th order at least give the car a good shake at 20hz? i'm fine with it being noticeably less powerful at 20, it doesn't need to move my steering wheel. just enough so I can feel when the beat drops from 26hz to 21hz. because right now it just feels like there's no bass note there. I don't care about a sharp drop off above 50 hz because I'm gonna get some good components for the 50 and above range.

If I have to get 15's I guess that will be the next plan. I have the power. but I would prefer to try a new enclosure to not only see if it works but to practice my design knowledge

Your SA subs have a fs in the low 30s and a low vas (high suspension stiffness) they are more of an SPL sub.

The X series is better designed for low notes with its high roll surround and long linear motor structure.

Get some subs that are designed for your specific application.

 

[dragon.breath 10+ year member]

Uh, the Taramps smart 3 does have a subsonic filter. Check your settings.

 

[devin171moto]

Uh, the Taramps smart 3 does have a subsonic filter. Check your settings.

it has a high pass and a low pass (10-90hz)(90-10k hz) but no subsonic

 

[shredder2]

it has a high pass and a low pass (10-90hz)(90-10k hz) but no subsonic

Ahem... hp can be/is your subsoinc

 

[devin171moto]

What vehicle do u have again?
U already tuned under 30hz and a 6th would be large.
Its extending to where it should at volume now so maybe higher excursion/power subs are the answer?
2 12s on like 5-7k in a 6th maybe sounds like might keep you happy this week.
Hey... We all want more but that 20hz life usually means cone area + big power.
2 Sa-12s?.. Maybe 2 X-12s on a badass 5k wired down or 8k @1 ohm for example.
Id grab some subs that'll SUB hard, handle big power and go.
20-40hz?
What u lookin for is within reach (i think) but $ is the answer at this point imo.

its a 2003 gmc envoy. it's got a hatch and the dimensions I gave are conservative, there's a fair amount of space. I dont know if anyone has had the same car and tried different boxes with it.

I'm getting the same answers from you and purple. I have the taramps 3k.

I guess I could pop the sa's in the box on craigs and see if I can sell it all together for 350 that way or to a friend. then put another 300 ish in for another set of subs. 5k rms seems like a lot more power than I want to go right now.

maybe take purples and your suggestion and fuse them get some 15's on the full 3k. more cone area. more power. I think I could fit a big enough box for some 15's behind the second row. smashing 18-40hz.

I'm looking at options now. so far 2 NVX vxf 15'S is the cheap option. PSI platfrom 1 15's is the expensive option.

my criteria would be under 30hz fs, high xmax, high vas woofer with as close to 3k as possible right? so I dont have the switch out my amp.

 

[devin171moto]

Ahem... hp can be/is your subsoinc

when I called the amp repair shop that works on brazilian ampss. they told me the high and low pass labels are backwards on brazilian amps.

the smart 3 is labeled as "high pass 10-90hz" "low pass 90-10k hz"
what he told me is the 10-90 is the low pass, and the 90-10k is the high pass.

so is that not correct? and if it is. I can't use the hpf as a subsonic because it doesn't go lower than 90hz

 

[shredder2]

Idk "smart 3k amps" but yes... I'd set it accordingly for UR power. Start 3db under tuning for a 12db Butterworth or if a 4th L/R maybe set it to 20hz or so. Your amp and vehicle are alien to me so play with it and report back.
I'd research what slope/type U got and go from there, don't kill your lows with a 29hz tuned enclosure for sure with a ssf but understand what U got.
"3k" ok then... it took me bux to get to a "3k" system and I'm a dummy... not too smart

 

[devin171moto]

Idk "smart 3k amps" but yes... I'd set it accordingly for UR power. Start 3db under tuning for a 12db Butterworth or if a 4th L/R maybe set it to 20hz or so. Your amp and vehicle are alien to me so play with it and report back.
I'd research what slope/type U got and go from there, don't kill your lows with a 29hz tuned enclosure for sure with a ssf but understand what U got

ROSSOVER HIGH PASS (HPF)	10Hz ~ 90Hz (-12dB/8ª) Variable
CROSSOVER LOW PASS (LPF)	90Hz ~ 10KHz (-12dB/8ª) Variable
BASS BOOST	Freq.: 35Hz ~ 55Hz Boost: 0 ~ +10dB
EFFICIENCY	79%

so are you saying the amp repair guy was wrong and 10-90 hz is indeed my high pass? not a low pass? and set it to 25hz approx?

that would mean It can't cross over below 90hz at the amp which is weird.

it was weird because when I set it to cross over at 80hz the subs played but music was coming through. I couldnt get the music to go away until I set the lpf on the head unit.
it's hard to find english info on this amp