What does the term F3 actaully mean

[JoshC 10+ year member]

So i think im going with a sa12. I see that in a 1.75cu^ft box @ 30hz it has an F3 of 26Hz. But what does that actaully mean? Like 30hz is going to be the peak sweet spot for output? Reason being is im looking to make the 35-50hz region push the most air, centered at 40-42Hz. So if i tune the port to lets say 42Hz is my F3 going to yield 38Hz now? Thanks

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[UMWDawg92 10+ year member]

F3 is the point where your frequency response has dropped 3dbs in output... so at 30hz it would have 3dbs less spl. It is important because 3dbs is about what it takes for a human's ear to actually notice a difference in the amount of output

 

[JoshC 10+ year member]

So if its tuned to 30Hz the ouput will drop 3db at 26hz? Is there any correlation between this and tuning frequency?

Basically i guess im asking if tuning the port to 42hz will give me a strong 35-50hz region then 30hz.

Say a songs bassline was at 54Hz, wouldnt it be louder if my box was tuned to 42hz vs 30hz? Most of my songs dont go below 32-35

Or is 30hz the best place to tune it and the output will be what it is

 

[UMWDawg92 10+ year member]

So if its tuned to 30Hz the ouput will drop 3db at 26hz? Is there any correlation between this and tuning frequency?

yes but tuning frequency and how the speaker's frequency response are dependent on the speaker itself... some are going to have a smoother or flatter frequency response when tuned higher others better when tuned lower. It's similar to how every speaker has an optimal sized enclosure. Generally speaking higher tuning will increase output but make the sub a one note wonder and will sound like ****, and when tuned high everytime you try to play anything below tuning frequency the sub will unload and get no help in controlling excursion from the enclosure which makes it easy to cause damage at high output.

 

[JoshC 10+ year member]

So basically go with sundowns recommended 1.75cu^ft @ 30hz?

My jbl was really loud 28-38hz or so but after that just lost its rumble. I want my next sub to rumble 32-50hz

 

[UMWDawg92 10+ year member]

Go with the recommended enclosure size it gives a bit of a peak in the range you're looking for

 

[duanebro 10+ year member]

There's more to it than that. A lot more. If you changed your tuning to say 40 Hz. your box will start to unload below that point. This means that you will loose spl and the woofer will move like it is not in a box. Not good. But what will happen is that everything played at 40 Hz will be louder than at any other, including above tuning, the higher you tune it the worse this becomes. Group delay could be worse, and phase also. This type of box is often called a one note wonder, or Spl box.

What type of music do you listen to? and what size car?

 

[JoshC 10+ year member]

Single cab truck. GOing to do sub behind me with port facing up in the center. I listen to alot of electronic music(dub, drum and bass, house) rock and reggae. My last box tuned to 35hz played most electonic music very well except for some house with bass above 45hz. But rock just didnt hit for crap

 

[hispls 5,000+ posts]

f3 is pretty much just where low end starts rolling off. I susect reccomended tuning will perform well. Changing the position of the sub, direction of aiming, placement of port may have more of an effect on response than a few cycles off in tuning of the box and much will depend on accoustics of your cabin.

 

[duanebro 10+ year member]

IMHO, when you add cabin gain in to your response you are getting way more in the low end. This leads to not hitting at higher frequencys. Tuning low may help in this case. Or using a sealed sub. Your max spl will be lower but more even.

 

[Kangaroux 5,000+ posts]

IMHO, when you add cabin gain in to your response you are getting way more in the low end. This leads to not hitting at higher frequencys. Tuning low may help in this case. Or using a sealed sub. Your max spl will be lower but more even.

Yep. I'm tuned to 27hz, and even though I should be getting nasty roll off at 50hz my cabin gain actually pulls the response up so it's pretty flat. My response from 30-50 could use a little bit of tweaking if I was picky enough but it sounds nice. If you are going to tune low, know where your cabin peaks at. Too high of a peak frequency and your response won't be smooth, but rather have a "valley". A cabin gain that is closer to your tuning will make your setup seem very peaky, and you won't reap the benefits of a smoother response, unless done properly.

 

[JoshC 10+ year member]

how would i go about calculating cabin gain?

 

[duanebro 10+ year member]

Good question. Unless you have a measurement system, you just guess. Anyone have a good way to figure this out?

 

[JoshC 10+ year member]

lol like using old fire works, either going to work as designed or blow your hand off. Well **** guess ill just go with rec. then and hope for the best. Anyone have a clue as to the differances between a SA12 and a obsidian 12? Ide like to save 40bucks and check out the obsidians but havnt heard much.

 

[THATpurpleKUSH 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.