Originally Posted by Nightlord
Originally Posted by Theresa
There is no reason for a properly ported sub not to reproduce all frequencies above the tuning frequency better than a sealed one. The one disadvantage of a ported sub is that the enclosure will be larger than a sealed one with a similar driver. Any talk about speed or "tightness" or.... is hogwash. The advantages of a sealed sub is all audiophile nonsense. I say this out of both experience and study. I currently have two subs, both DIY, both tuned with large passive radiators which are equivalent to ports. They are extraordinary sounding with clean bass from their crossover down to below 20Hz.
How does this box behave compared to a ported box below the tuning frequency? Say if you want to EQ it up quite a lot in the ULF, say to play useful outputs in the 5-10Hz range?
The dynamic and distortion behavior of a speaker at any frequency below the point where it is mass loaded is dominated by the linearity of the cone's suspension and magnetic motor. I suspect that a vented enclosure may have a slight edge near the box tuning frequency, which in turn is near to but usually above the - 3dB point because cone motion is reduced at this point, and sound from the vent predominates.
In the picture about the blue line is the radiation from the cone which roughly tracks cone motion at low frequencies. You can see that cone motion is actually minimized around about 78 Hz. This corresponds to an area of low distortion. Instead of coming from the cone at this frequency, the sound in the room mostly comes from the port. Below the-3 dB point low frequency distortion rises pretty quickly because cone motion increases.
At 10 Hz the threshold of hearing is very high.
The threshold of hearing below 20 Hz is not generally given, but the green line shows a reasonable but not necessarily highly accurate extrapolation to approximately 95 dB @ 10 Hz.
As shown below merely having a barely audible SPL at 10 Hz requires at minimum a SOTA 15" subwoofer driver:
If you want to enjoy 10 Hz, you might need a minimum of 4 SOTA 18" drivers and they would probably have to have some low bass boost!