Subsonic Filter for Sealed Enclosure

[SnapperKing 6]

Just purchased the sealed enclosure for 2) 12" SSA GCONs - Net will be 1.3.1-45 FT^3 per. I've been doing some research but have seen a very wide variety of recommendations for setting the amp's subsonic filter for sealed enclosures.

Some say to set it @ or just below the Fs of the speaker (31.5hz for the GCON)

Some say that you don't need to run the subsonic filter at all because the air-suspension inside of the sealed enclosure acts as a shock absorber/accumulator and will provide ample protection from over-excursion.

Not sure which is the best bet for my situation. Naturally, I want to protect my drivers without inhibiting performance.

What should I be doing here? Input from the SSA guys would be much appreciated.

Thanks,

The Snapper King

[An-i-no 86]

You don't need it. This comes from first hand experience.

Unless the box is a LOT bigger than recommended it will control the excursion just fine.

[ricksi30 923]

You don't need it. This comes from first hand experience.

Unless the box is a LOT bigger than recommended it will control the excursion just fine.

Agreed, as long as the enclosure is the proper size I wouldn't worry about it.

[Impious 1,476]

It depends on the amount of power you are running, volume of your enclosure and things like your musical selection and listening habits.

The purpose of a SSF is to limit the excursion of the driver at certain frequencies to decrease the possibility of damage to the driver. Of course this is a big problem for ported enclosures because of driver unloading below tuning. However exceeding the mechanical limits of the driver can also be a potential problem in sealed enclosures depending on the volume of the enclosure, amount of power, etc etc. To see if you are at risk, it's a simple matter to load the driver and enclosure into WinISD and look at the cone excursion graph. In a sealed enclosure excursion will always increase as frequency decreases, what's important to note is the frequencies at which you begin to exceed Xmax (although exceeding Xmax won't damage the driver, you don't know the Xmech of the driver so we'll use Xmax as an approximation to stay on the safe side).

While it's probably pretty likely you won't really need an SSF, it is important to note where you might begin to run into problems. It helps keep you from doing stupid things like blasting a 20hz sine wave showing off for friends thinking you're "safe" because you have a sealed enclosure when it could in fact potentially damage the driver if excursion is too high in your enclosure volume with your power level. Or if you, for example, listen to a lot of classical music which can contain very low frequency reproductions.

The other use for an SSF is to use it as an "equalizer" to smooth out a bloated bottom end

[SnapperKing 6]

1.35 - 1.40 FT^3 as per the optimal sealed recommendations on the SSA website. They will be getting ~600W each.

I've never used WinISD before - is it a free program?

[ssh 924]

Most amps come with a ssf, so you mine as well use it.

If yours doesn't have one, then I wouldn't worry too much, your enclosure isn't large.

Impious summed it all up nicely.

Yes, WinISD is free.

Edited June 13, 2012 by stefanhinote

[An-i-no 86]

While it's probably pretty likely you won't really need an SSF, it is important to note where you might begin to run into problems. It helps keep you from doing stupid things like blasting a 20hz sine wave showing off for friends thinking you're "safe" because you have a sealed enclosure when it could in fact potentially damage the driver if excursion is too high in your enclosure volume with your power level. Or if you, for example, listen to a lot of classical music which can contain very low frequency reproductions.

The other use for an SSF is to use it as an "equalizer" to smooth out a bloated bottom end

Hmm...maybe one of these days I'll stop assuming people know what unloading sounds like.

[///M5 2,833]

The other use for an SSF is to use it as an "equalizer" to smooth out a bloated bottom end

Great use for it considering you surely don't know your cabin gain up front.

Most amps come with a ssf, so you mine as well use it.

As long as the frequency is adjustable or fits in a range where it helps. Nothing like adding another level of safety to have it be out of whack and give false confidence.

[ssh 924]

The other use for an SSF is to use it as an "equalizer" to smooth out a bloated bottom end

Great use for it considering you surely don't know your cabin gain up front.

Most amps come with a ssf, so you mine as well use it.

As long as the frequency is adjustable or fits in a range where it helps. Nothing like adding another level of safety to have it be out of whack and give false confidence.

Yeah, a fair amount are fixed and set relatively low, which can be problematic for ported enclosures & the general census of 30hz tuning, but a fixed 20hz ssf & a sealed enclosure sounds pretty good to me.

[Tirefryr 1,742]

I never have, nor will I ever use one.

[Impious 1,476]

I never have, nor will I ever use one.

I've never used an SSF, I have however used my EQ to smooth out the low end which, since I'm making big cuts down there, is in effect the same thing as an SSF.

Actually, I take that back. IIRC my MS8 doesn't have an "off" for the subsonic, so I had it set to 20hz with a 6db slope and let the EQ take care of the bottom end for me.

[Quentin Jarrell 671]

I've never had a sub spontainiously combust under tuning either.

[Quentin Jarrell 671]

Anyhow a driver should have more xmech than xsus to prevent sub failure in these rare cases of unloading.

[SnapperKing 6]

At which frequency would I want to set the SSF to if i were to run it as an additional level of protection? I'm thinking 20-22hz?

[Quentin Jarrell 671]

Your best bet is to use test tunes at low- moderate lever. Start high work you way down. When the sub starts to unload (move like it's free aired) adjust the ssf a bit higher than that frequency

And don't go by the numbers written on the amp. They could be anywheres up to 20 percent off.

[SnapperKing 6]

OK Sounds good. I'll let you guys know how it works out.

I probably should take some videos and put them on youtube when i'm done. There is 1 video of a single GCON in a ported enclosure and free-air (SSA's Video).