Hz question

[chicago_guy]

What is the main effect of having a lower Hz rating for a vented box. Lets say somebody had a 2 cubic ft vented box tuned to 40 Hz, and another has the same box but tuned to 30 Hz. How much different would they sound?

[Haibane]

different subs peak or sound better or louder at different levels of tuning

[sr20de4evr]

The tuning of the box is the frequency where the wave from the port and the wave from the cone are in phase (or as much in phase as they can be). The signals add constructively and it makes it louder at, and just above, that frequency. On a side note, at this frequency the air is going in the port at the same time the cone is going in, resulting in a much higher pressure inside and the cone moves less for the same amount of power, which lets you run more power through the sub when it's at that frequency without it bottoming out.

When you get below the tuning frequency the waves from the port and the cone become more and more out of phase, and once you hit about 5-10Hz below the tuning frequency the air is going in the port at the same time the cone is going out, this makes the sub perform almost like it isn't in a box at all and it can easily tear itself apart if you aren't careful and run too much power through it at this frequency.

This is why sub sonic filters are used. They are generally set about 5Hz below the tuning frequency so as it gets lower and lower the signal diminishes and it keeps the sub from killing itself.

Assuming the same sub was in 2 different boxes, one tuned to 40Hz, one tuned to 30Hz, both using SSF set about 5Hz below the tuning frequency, the one in the 40Hz box would be louder around 40-45Hz and then once you get down to around 30Hz it won't even be audible anymore. The one in the 30Hz box won't be as loud around 40, but it will hit much lower.

For daily driver setups you generally tune it low so you can get all the frequencies from the music without cutting any off with the SSF. My box is tuned to 26Hz so it hits VERY low and I love it. If you are going into SPL competitions you normally tune the box just under your car's resonant frequency (around 45-50Hz for most cars) so it will be it's loudest right around there. These are terrible for daily driver setups since you won't even be able to hear half of the songs when listening to rap or other low-hitting songs.

[chicago_guy]

ok thanks for clearing that up. So if i just keep to the manufacturer's specs for box tuning i should be fine, right?

[GSteg]

depends on the manufactor. over time, i have noticed that manufactors only recommend "X" size because it gives them the "small box" sub status. usually it'll sound good for most average people who don't need to extract the most out of their sub.

[chicago_guy]

ok how about if i phrase it like this b/c im still a little confused. The sub im looking into has a recommended tuning of 30 Hz. If i were to tune it to 40 Hz what would the result be?

[GSteg]

your frequency reponse will be more peakier. most likely not as smooth sounding as 30hz. you'll get a higher group delay time with it. probably not the freq. u want to tune the box at if u want sound quality.

[sr20de4evr]

40Hz would be good for impressing your friends or SPL competitions, that's about it. The frequency response will peak pretty high, and you'll miss out on half of many songs with low bass lines (lots of rap, some metal with deep bass lines in the background). It just won't sound that good for music, but test tones at 40-45Hz will sound nice.

[chicago_guy]

ok now i get it. so basically the higher the number the louder it will be. Thanks for your help.

[Haibane]

not true... The louder it will be at those frequencys. The higher the number is not the louder. only in certain ranges is it louder than the rest

[sr20de4evr]

Originally Posted by chicago_guy

ok now i get it. so basically the higher the number the louder it will be. Thanks for your help.

The number is a frequency, a ported sub will be its loudest (generally) at the tuning frequency. So a higher number means it will be its loudest at a higher frequency, it doesn't mean it gets louder. With a sub that has a perfectly flat frequency response, not taking into account cabin gain or the resonant frequency of the car or anything like that, a sub at a 40Hz tune and the same sub at a 30Hz tune will be just as loud as each other, but the one with the 40Hz tune will be its loudest at 40Hz, and the 30Hz one will be its loudest at 30Hz. Below the tuning frequency the response drops off exponentially, so at about 5-10Hz below tuning and below you can't really hear the sub anymore.

This means that if you have a sub in a ported box tuned to 40Hz, it will be loud at 40Hz and it won't even be able to play anything below that. A 30Hz box on the other hand won't be quite as loud at 40Hz, but it will be able to play all the way down to 28Hz or so and still be loud, which is much better for listening to music.

As a general rule, if you're going to play music through your sub (as opposed to test tones all the time), tune low, as in 25-32Hz.

[chicago_guy]

ok now i actually get... i mean it this time. Thanx for your guys' help.

BTW-can you tell the im a newbie? lol

[9ball]

The best way to learn about box tuning is to use a box tuning computer program. I used WinISD to build mine. Look it up on the internet, it's a free download.

[chicago_guy]

i have WinISD dowloaded...the problem is that i havent figured out how to read the info in it. I will figure it out though, i just need to explore the program more.

[chicago_guy]

speakin of WinISD, how do i change it from the metric system to the english system?