Hertz?

[Vindicate]

Ok, I've been tryen to read around and figure out what tuning to diff hertz does, and I just can't wrap my head around it for some reason... Here are my questions in regards to hertz.

1) If you have your subs tuned to low hertz, can you play the higher hertz also? Or do you have to stay in the range of whatever your box is tuned to? (I think I read somewhere that you can go about 1/2 a hertz lower before you hurt your subs) So say my Box is tuned to 35Hz, if they were trying to play at 60Hz would my subs get damaged?

2) What are the ranges for a sealed box? I have Resonant Engineering RE12s, and their stat sheet says 20.0Hz. Does that mean that any sealed box I build will give me 20hz? I built the box to 15x15x15=1.424 Sq.ft. That is without the displacement of the woofer. I think I read somewhere it's 0.14 or something.

3) Do I try and match my sub hz setting to my amp setting? If so my amp only goes as low as 50hz.

Sorry if these questions seem retarded to you guys, I just have NO clue about these there hertz things! OI!

[Mithrandir]

as for the box tuning i dunno, sealed boxes play all ranges of sound well, ported play the tuned part loudest and it slowly gets lower as you go up in hz. i think the subs will get damaged if its ported and you go below the tuned hz which is why you use a subsonic filter. The lowpass on your amp is to stop your subwoofers from playing too high of hz because that will damage then id set the filter to 100 - 125

[stephensmia]

for ported boxes the sub wont play below what its been tuned to. the closer it gets to the tuned freq the less work the sub dose and the port takes on the work vibrating at the freq.
I think thats right

[audiobass10]

i think the subs will get damaged if its ported and you go below the tuned hz

That's not really true. It's true you shouldnt be playing below tuned frequency often, but I played 20hz test tones with my SE all the time for fun and it never really phased it. As long as its not for long periods of time it's usually fine.

[veggie-man]

ok i'm not sure if this is going to answer any of your questions but It depends on your boxes tunning frequency. below explains it 10 times better than what i could ever do.


here is one section in the FAQ:

A subwoofer cone moves in and out very, very rapidly. 40hz is 40 "in and out"s per second!

The lower the note you play, the fewer cycles per second (20hz is only 20 "ins and outs" per second, for example, compared to 40hz, or 80hz)

There's a point, depending on your port "tuning frequency", where the cone slows down enough that it can't support that moving mass of air anymore...
...and at that point, the port just acts like a gaping hole in the box... making the box not act like a box at all. At that point, there's no air pressure inside the box helping control cone excursion - and it's easy to bottom the sub out with just a fraction of your wattage!
Blown sub... overexcursion damage.

entire article:
http://www.caraudiocentral.net/forums/s ... php?t=3156

[stephensmia]

Hertz(noun) : A unit of frequency equal to one cycle per second.
So hertz is the number of times the speaker is able to move in one second.

[GlassWolf]

1: the response of the box varies based on several factors, such as volume, port tuning, and the sub you use. Generally it works like this:
the higher you tune the port (closer to the resonant frequency of the cabin) the more SPL you'll get from it, but the more "boomy" or warm the sound will be, which isn't very pleasing to most people. You give up low end response for more volume.
The lower you tune the box (down to the Fs of the subwoofer. going lower doesn't add any benefit) the more musical and low the box will play. The drawback is that tuning lower gives less of a spike in output at the tuned frequency.
You should be using a subsonic filter set to the tuned frequency of the enclosure anyway so you will never play much of anything below the tuned frequency of a ported box in a properly designed system. This is another reason I tend to prefer boxes tuned to the 25-35Hz range instead of the more commonly used prefab range of 40-50Hz, or god forbid, the bandpass box range you typically see of 55-65Hz.
If you chart the output of a ported box, with cabin gain factored in so you get an "in car" result, you'd see a graph with a curve that starts at 80Hz (where subs start, typically) at zero gain, with a very gentle rise in gain as you approach the tuned frequency. at or near the tuned frequency (typically about one octave above tuned freq) you'll see a sharp spike in efficiency, meaning the sub gets louder at the same power input. After the tuned frequency you'll see the sub's curve drop off like a brick, down to zero output.
the higher you tune the box, the sharper and larger that spike will be at the tuned frequency, but the sooner the curve will sharply drop off.
-So say my Box is tuned to 35Hz, if they were trying to play at 60Hz would my subs get damaged?
certainly not. a box tuned to 35Hz will play from the LPF set frequency (say 80Hz) down to 35Hz. Now if you tried to play 25Hz on that box, with no SSF in place, then yes you'd damage the subs. that's why we have subsonic filters.

2. What are the ranges for a sealed box? I have Resonant Engineering RE12s, and their stat sheet says 20.0Hz. Does that mean that any sealed box I build will give me 20hz?

That spec on paper is called an "anechoic response" meaning out of a box, or not in the car with cabin gain factored in.
the graphed response of a sealed box with cabin gain, is flat as a board from 80Hz down to about 9Hz (well below human hearing range)
changing the box volume for a sealed box will not affect the frequency response or range so much as it will affect the output (SPL) of the subwoofer, and the power handling ability (mechanical) as well as how tight or boomy the response of the driver is in the car. Box size for a sealed sub does affect things, just not the things you're asking about.

3. set the PLF setting on the amp to 80Hz for starters. (60-80Hz is what most people end up with)
this defines where the subs start playing (with no roll off)
the ported enclosure should be tuned to just above the Fs of the subwoofer. Usually about 32Hz or so for good deep bass.

Does that answer your questions?

[Darthness]

for ported boxes the sub wont play below what its been tuned to. the closer it gets to the tuned freq the less work the sub dose and the port takes on the work vibrating at the freq.
I think thats right

thats wrong, i don't know the hole truth, but a sub in a ported box will play whatever freqs. you throw at it (As long as the driver is capable.. and im sure there are other exceptions)

i belive as someone else said, ported boxes will play at its tuning frequency the loudest... which would pretty much explain why (for example) spl competitors try to find some sort of vehicle-specific frequency that will be loudest.. adn then tune the box to that.


something like that, im sure.

[GlassWolf]

below the tuned frequency, the sub becomes very difficult to control, and you run a very high risk of the driver unloading, and losing all of it's suspension provided by the box.. which in layman's terms results in watching the cone of your speaker go flying across the car in a puff much akin to that of a capacitor blowing it's pressure seal.

I wouldn't suggest doing it often.

[Darthness]

can't wait til my 10's get here, im so going to throw it a 10hz tone and see how long it lasts i guess its a good thing i didn't decide to tune my box too high... althoguh, i am using flared round ports so im pretty sure i could order ports with differnt tunings and swap them out...