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Discussion in 'Home Theater Projects' started by DanielKellmii, Mar 11, 2004.
I see some subs with variable "tuning points", what does that mean?
I believe they are referring to a built in variable crossover which allows you to determine what frequency you want to have your sub roll-off at (usually a 12db rolloff). -Jason
No, not that. This is something that can be adjusted with baffles. "Selectable 16Hz, 20Hz or 25Hz tuning with included port plugs" That is what I am asking about. Thanks.
Moved to diy/advanced area.
As you know the "Tuning Point" or "Tuning Frequency" or "Fb" is the the frequency the sub (box or tube) is tuned to. So if a sub enclosure is tuned to 25Hz any frequencies after 25Hz will roll off quickly. A variable Tuning Point just means (in this case) that they can plug one of the ports to lower that Tuning Frequency for more low bass extension. A trade off is that they will loose a little upper bass (upper bass frequencies). Or they can open them all up for more upper bass with a loss of lower bass. I believe it's just a few dB's difference when port blocking but noticeable. Did I get this right???
I got moved to advanced.
Give this post I wrote a while ago a read. http://www.hometheaterforum.com/htfo...53#post1937653
Dustin, thanks. That is very helpful.
You would be surprised at how quickly the answer to this question could get somewhat complex.
I believe in a sealed sub, the 'tuning point' is generally considered the point at which the sub's output is 3db down anechoically, called the F3. Perhaps someone can correct me on this if I'm wrong. In a vented sub, the tuning point is the frequency the port is tuned to. At this frequency, the port will be providing 100% of the sub's output, the driver will not be contributing at all. As you move away from this point, the driver's contribution grows and the port's contribution shrinks. Some subs have variable port tuning points so you can 'shape' the low frequency response to what you prefer, by altering the interaction of the port's output and the driver's output.
It's definately not a 0%/100% contribution at tuning. The link I posted above has some graphs that show the relative contributions quite well.