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How do you choose the proper subsonic filter?

1K views 34 replies 8 participants last post by  jbeez 
#1 ·
I plotted out a box design in winISD, and I went to the cone excursion plot and I'm checking out some different subsonic filter settings, its a 4cu/ft box tuned to 30hz and my main question is, can I use a 25hz subsonic filter as long as the excursion isn't exceeded? When I plug in a 25hz@12db the cones hit about 20mm out of 28. Physically I see that it may not bottom out(afaik) but will it just sound like crap?

On the higher end the cone excursion seems to be peaking at 43hz, and its at a nice low dip right at the tuning freq of 30, the lower you go it starts rising back up again. Without any filter I will have some issues around 23hz. I don't think I have any programming that exactly goes that low but I'd rather throw a cheap hooker audio or harrison fmod filter on it and not worry about it. My amp doesn't seem to have a subsonic filter on it(zapco c2k 9.0xd)

Thanks,
-J
 
#2 ·
How much sub 23hz information are you planning on playing full tilt?

If you trust your models and don't need to speak to whales, grab a 25hz FMod and be done with it.
 
#3 ·
I'm not playing any bass mechanic CDs in the car on the daily, and I'm not talking to any ocean life LOL. This is more for an SQ install than SPL and I listen to all sorts of shit from electronic to acoustic, rock/hip-hop/dubstep etc.

Thanks!
 
#4 ·
don't fall into the "low end reproduction bs" that has been on forums for a while. There are very few, unaltered, songs that drop under 30hz. I would also say 25hz if your sure that's where your issues will start. It's not a definite cut off but rolls off at a set curve.
 
#9 ·
don't fall into the "low end reproduction bs" that has been on forums for a while. There are very few, unaltered, songs that drop under 30hz. I would also say 25hz if your sure that's where your issues will start. It's not a definite cut off but rolls off at a set curve.
I find about 10 per day EASILY with no alternation that go below 30hz in rap, hip hop, EDM, trap, etc... the bolded above is a regurgitated statement from people who are forgetting to mention they mean "radio" or "pop" music, in which case the statement holds more truth, but it does not encompass all genres as a whole, far from the truth.

I've always left my SSF Off or at Min... I choose to know what I am playing instead of using a crossover to "protect" me from dropping too low.

As mentioned, the drop or slope of the crossover is not a brick wall and its gradual... but not many realize or care to pay attention that the crossover point is -3dB or -6dB (depending on BW or LR), so its attenuating ABOVE the crossover point and is taking power away from the frequencies you deemed "playable" as well. IE: 30Hz SSF@-12dB... would still cut the signal at 35hz
 
#5 ·
It's true that there is not much sub-30hz content in most music, but all it takes is dropping that low once or even a turn on pop.

Care to tell us a little more about your setup? If your goal is a SQ install, you might be able to get away with shrinking the enclosure size a little and tuning lower to shift the sub's unloading point low enough to not even need subsonic protection. A drop in enclosure size will also lower group delay at the tuning freq, and lowering the tuning frequency at the same time will shift the group delay a little lower to decrease it throughout the rest of your bandwidth. <20ms is a good starting point.
 
#6 ·
OK, Here's where I'm at right now,

I have a 2wk old 2014 taurus SHO w/ sony system and nav in it.

I've ordered 2 psi platform 2 12" subs w/ hp option from psi audio and dave knows I'm leaning towards SQ for them.

I have currently onhand, zapco c2k 9.0xd amp, RF600a4, RF800a4, jlaudio cleansweep, jlaudio signal summing interface, a longass stinger 0awg i pulled out of my crownvic that ill be reusing, polk 5.25 components i pulled out of the front of my cv, and 5.25 coaxials i pulled out of the back of my cv. not sure if im putting the polk stuff back in.

Been pouring over box plots and all sorts of things for these subs for a few days now, trying to figure out enclosures, how I wanted them etc. I was first thinking of doing a sealed fiberglass setup with false floor in the spare tire well but decided it would probably be easier for me to go with a traditional box and I would also probably get a better sound out of it. Dave sent me some ported boxes he's used in the past with these and i've been plotting them out in WinISD alpha. the 4cu/ft @30hz port tuning for a pair of these 12's looked the best to me. WinISD def plot for them is almost 7cuft, its a little ridiculous heh.

Some things I'm still in the process of figuring out, how to mount my amps, cleansweep stuff, which subsonic filter to get, if I want different front speakers(I may tackle highs later, depending on budget), if I'll need another battery in my taurus in the trunk, if the stock alternator will be ok, I need to inventory my connectors and fuses I have from various installs and see if I have what I need to hook all this stuff up.
 
#7 ·
Sounds like that will be a nice setup. I love the old a4 amps, but they are VERY power hungry. I'd definitely look into at least adding another battery.

Do you have the t/s specs on the subs? Have you ever thought about a 4th order BP? Lots of people associate 4th orders with SPL, but they can be built to cover an incredible bandwidth with group delay almost as low as sealed.
 
#8 ·
Havent thought of the 4th b/c i just associate it with spl lol. Ill check that out.

The t/s are on the psiaudio page for the platform 2s, but dave sent me a partial list of them in email b/c these subs are a little different than stock
Revc*=*3.4 ohms
Fms*=*30.3 Hz
Qts*= 0.51
Sd*= 490cm^2
Vas*=*51.1 L
BL*=*15.5
Mms*= 199.8 g
Sensitivity = 85.5 dB @1W/1m

Sent from my HTC One
 
#13 ·
These look pretty good in a 4th order with a 4.0cf sealed and 1.75cf vented tuned to 65hz. They aren't showing as loud of a peak as a pair in 4cf tuned to 30hz, but the bandwidth looks to be within 3db from the low 20's to around 70hz. In this enclosure, you wouldn't even need a SSF.
 
#10 ·
This was really easy in my last car, i had an eclipse cd7200 mkii with all the adjustability i could want. My new car has everything integrated with the factory headunit. Im just trying to work with that, and not bottom anything out. I shouldn't need to know that a song im about to play has a 23hz note so i shouldnt try to bump it or im going to damage my gear.
Aint nobody got time fo dat

Sent from my HTC One
 
#12 ·
SSF's are usually a LR 4th order, which is a 24db slope and does not have as much of an affect above the crossover point as a butterworth. The great thing about 24db filters is they shift the phase 360 degrees which in turn does not change the phase response at the crossover freq.
 
#15 ·
Also having this discussion made me realize my stock headunit only has basic 3 band "eq" and the bands are... treble/mid/bass !

What do you guys like for audio processors? Was looking at the audiocontrol EQS, and that would also handle my subsonic filter issue as well... plus I'd be able to actually eq for my car a little, the cleansweep just removes the factory equalizations of the source signal but I still have to compensate for the enviornment after the programming leaves the drivers
 
#16 ·
Also having this discussion made me realize my stock headunit only has basic 3 band "eq" and the bands are... treble/mid/bass !

What do you guys like for audio processors? Was looking at the audiocontrol EQS, and that would also handle my subsonic filter issue as well... plus I'd be able to actually eq for my car a little, the cleansweep just removes the factory equalizations of the source signal but I still have to compensate for the enviornment after the programming leaves the drivers
Depends on your budget. You can get a MiniDSP for 100 bucks. Or a Arc PS8 for like... a billion dollars.

The Zapco DSP-Z8 is a lovely piece that comes in ~ $450 new. The JBL MS-8 is a "set it and forget it" type processor that does all the tuning for you. They're a steal at used prices.
 
#19 ·
The cleansweep is brand new and i could return it if need be, to purchase a diff device that may duplicate those functions. Not sure how good the other options are for cleaning up shitty oem processing

Sent from my HTC One
Much better, actually
 
#23 ·
thats how men do it :thumbsup:
 
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#22 ·
i leave subsonic off lol
 
#28 ·
I'll, ideally, have no extraneous knobs or displays upfront, it'll look completely stock if I can help it. I listen to all sorts of sources, CDs, google play, pandora, di.fm, satellite radio, and there is a bunch of music I have no idea how low it goes I just enjoy it. I did attempt to run foobar2000 through a pc based RTA to try and see what kind of frequencies were coming back but I didn't have enough resolution to discern exactly the lowest frequencies going on there
 
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