What frequency to tune to??????? (1 Viewer)

[Chris:-/OV]

Hi
I'm fairly new to sub building and need someone to explain to me how you figure out what frequency your sub should be tuned to. Is the type of music you listen to a factor?
For example should I tune the sub to say 40Hz for more punch?

 

[Ryan Schnacke]

It depends on a number of things.

Is the sub going to be used for home theater? If so then you'll definitely want to tune it lower than 30Hz. Probably more like 20 - 25Hz. In a ported enclosure the woofer has very little loading at frequencies below the tuning point (1/3 octave or more below). So if its tuned to 40Hz and even a moderately powerful 30Hz note is input then you'll bottom that woofer out in no time. The solutions to this are to tune the sub very low or apply a "rumble filter" to filter out signals below the tuning point. A lot of guys use some combination of these since DVD soundtracks can have large signals down to 10-15Hz and tuning below 15Hz gets kinda ridiculus.

It'll also depend on the woofer and enclosure size. Some woofers work better in big boxes tuned low. Others might like some other configuration. The best way to learn this stuff is to play around with one of the box/woofer simulation programs.

Dinner's ready and I'm gonna get in trouble if I stay any longer so I hope this helps.

 

[Rob Formica]

The tuning of a sub is the frequency at which the port will produce it's maximum output.

A port acts like a woofer driver at a very narrow frequency due to the resonant frequency of the mass of air in the tube (a port and a Passive Radiator work in the same way). So question is which frequency you'd like the maximum output from your port... and to choose this you have to model the performance of your woofer in the projected cabinet. In theory you want to tune the port to the point where the woofer normally rolls off, in such extending it's low frequency performance.

Using the T/S parameters and a small software like WinISD http://www.linearteam.dk/ you can do this pretty easily (unless you want to do the math manually http://www.diysubwoofers.org/). Then you play with the tuning frequency and box size to get your desired performance. By default winISD will recommend an enclosure/tuning to produce the flattest response possible.

People in HT often prefer an EBS (extended bass shelf) design which has a larger than ideal box with a slightly lower tuning which will lower the sub's overall SPL but extend it's low frequency response. Using a slightly smaller than ideal enclosure with a higher tuning will create a small peak in the mid-bass frequency response and these are often referred to as "punchy" subs.

In any case the TUNING isn't necessarily the "roll off" of the subwoofer or the lowest frequency it'll reproduce... but is the maximum output of the port.

Hope this helps...
Rob