What does the term F3 actaully mean

[Kangaroux 5,000+ posts]

The only available Obsidians are the 12 d2s, the rest arent available till February. They say the Obsidians sound like a mix of SAs and Skars. I am very interested in trying out a 15 when they are available again.
I have always understood that f3 was when the roll off was down 1 octave.

You might be confusing it with the general idea of setting a subsonic filter, where you set the filter to being a half octave down.

 

[wenn_du_weinst 10+ year member]

f3 is calculated in half space.

 

[ciaonzo 5,000+ posts]

f3 is calculated in half space.

F3 can be calculated anywhere, in a cornfield or in a closet.

 

[wenn_du_weinst 10+ year member]

F3 can be calculated anywhere, in a cornfield or in a closet.

if noted, on speaker specs 90% of the time it is taken in half space. What would be the point of listing response from in car?

 

[huricaine 10+ year member]

For music it's usually good to tune low. Some people are tuned high and it gets pretty punchy but it's more one note and quick rolloff while the cabin's gain picks up low end some. Unloading dosn't sound good though even if you can keep the sub under excursion limits it still isn't great. Alot say you can get away with tuning higher with rock and the like, but if you want to keep some of the sq then tuning low is always good, just not too low.

Plenty of subs aren't too peaky at even a pretty high tuning either, it also depends on box volume.

 

[ciaonzo 5,000+ posts]

What would be the point of listing response from in car?

What you should be asking yourself is what would be the point of measuring a subwoofer system intended for use in a vehicle, in half space?
If you designed it to achieve an F3 of 22Hz in half space, what would the results be once it was installed in the vehicle? That would be more like 1/4 space or even 1/8 space, yielding a far lower actual F3. Highly desirable in my opinion, but rather unpredictable unless you have an accurate frequency response plot handy for your vehicle that you can use for a reference.

Just sayin', there's subwoofer/enclosure F3 and there's system F3. Very different things.

 

[wenn_du_weinst 10+ year member]

What you should be asking yourself is what would be the point of measuring a subwoofer system intended for use in a vehicle, in half space?
If you designed it to achieve an F3 of 22Hz in half space, what would the results be once it was installed in the vehicle? That would be more like 1/4 space or even 1/8 space, yielding a far lower actual F3. Highly desirable in my opinion, but rather unpredictable unless you have an accurate frequency response plot handy for your vehicle that you can use for a reference.

Just sayin', there's subwoofer/enclosure F3 and there's system F3. Very different things.

because every vehicle is different, a real installer could use what he already knows about his cabin to gain a general idea on how it will respond in car.

 

[ciaonzo 5,000+ posts]

Also of importance is what happens in the stretch between F3 and F10. Food for thought.

 

---------- Post added at 12:00 PM ---------- Previous post was at 11:59 AM ----------

 

because every vehicle is different, a real installer could use what he already knows about his cabin to gain a general idea on how it will respond in car.

Can't argue that, but OP doesn't sound like that guy so I thought I would put it out there.

 

[huricaine 10+ year member]

Because ported enclosures mechanically unload and "disappear" below tuning, cabin gain will not help as much as for a sealed enclosure(below tuning). This is why ported enclosures are recommended to be tuned near your preferred low side. It's like having an HPF set(like SSF), like electronically cutting out the signal. Cabin gain won't boost a signal that's not there. Which is also why there is an SSF since it's not worth having that signal there.

As far as spatial loading goes: It's just the way they do it. A tested F3 in manufacturers car(test) won't guarantee that you will get that in your vehicle.

 

[wenn_du_weinst 10+ year member]

Also of importance is what happens in the stretch between F3 and F10. Food for thought. 

---------- Post added at 12:00 PM ---------- Previous post was at 11:59 AM ----------

 

Can't argue that, but OP doesn't sound like that guy so I thought I would put it out there.

I wish more people would understand the importance of knowing the cabin gain of your car. I have mine saved for when I redo my enclosures.

 

[JoshC 10+ year member]

lol yea idk if my installer does threw that. I know he runs a program or 2 to get the box designs and what not, but hes come threw for me every other time. Hes got alot more knowledge about how the mech. interact then i do

 

[ciaonzo 5,000+ posts]

Because ported enclosures mechanically unload and "disappear" below tuning, cabin gain will not help as much as for a sealed enclosure. It's like having an HPF set(like SSF), like electronically cutting out the signal. Cabin gain won't boost a signal that's not there. Which is also why there is an SSF since it's not worth having that signal there.
As far as spatial loading goes: It's just the way they do it. A tested F3 in manufacturers car(test) won't guarantee that you will get that in your vehicle.

Very good info. All of it true. The only difference of opinion I have is that even as the driver is unloading below tuning, the cabin gain will certainly add more to the "disappearing" frequency response than a room will. Especially if the driver and vent have any amount of distance between them so that they may be "loading" different areas. The reason frequency response falls off is because all the energy below tuning (originating from the backside of the driver) has inverted phase relative to the driver's front output. Sometimes you can end up getting quite a bit of usable response well below tuning in vehicles. Much more than in a living room or similar.
Honestly, I'm not trying to play semantics. Just kicking things around.

 

[ciaonzo 5,000+ posts]

I wish more people would understand the importance of knowing the cabin gain of your car. I have mine saved for when I redo my enclosures.

Truly awesome effects from cabin gain. Especially in the teens and twenties.

 

[huricaine 10+ year member]

Very good info. All of it true. The only difference of opinion I have is that even as the driver is unloading below tuning, the cabin gain will certainly add more to the "disappearing" frequency response than a room will. Especially if the driver and vent have any amount of distance between them so that they may be "loading" different areas. The reason frequency response falls off is because all the energy below tuning (originating from the backside of the driver) has inverted phase relative to the driver's front output. Sometimes you can end up getting quite a bit of usable response well below tuning in vehicles. Much more than in a living room or similar.
Honestly, I'm not trying to play semantics. Just kicking things around.

Yessir, and the bad part about unloading is that the sound you get from it dosn't sound good. The subwoofer unloads due to the port not having enough mass to "catch the sub". Ported subwoofers are efficient and the absence of the loading on the subwoofer kills the sound quality down there. I've never liked the sound below tuning unless it was within a few cycles.

 

[ciaonzo 5,000+ posts]

Yessir, and the bad part about unloading is that the sound you get from it dosn't sound good. The subwoofer unloads due to the port not having enough mass to "catch the sub". Ported subwoofers are efficient and the absence of the loading on the subwoofer kills the sound quality down there. I've never liked the sound below tuning unless it was within a few cycles.

Yep, no more loading and then the output from the rear of the driver (and there's lots of it) is pretty much completely out of phase with the front of the driver and that leaves you with purely all the wonderful sounds of mechanical distress and goo-goo gobs of THD.