Sealed vs ported spl and xmax at low frequency

[rpb]

I agree with Bill. Lower the box tuning a bit and see what happens. Might stumble on something better. That's what makes this hobby fun.

My rule of thumb.... Always tune to 23hz. (Mostly kidding.)

Lots of amps roll off starting around 20hz, and will reduce some of the excess excursion.

[Regore]

I agree with Bill. Lower the box tuning a bit and see what happens. Might stumble on something better. That's what makes this hobby fun.

[Paul O]

Apply a high pass filter to the ported sub so that xmax isn't exceeded below tuning.
Eq the sealed sub to achieve the same response as the ported box.

Then compare cone excursion of both designs.

[billfitzmaurice]

Tune the box to 20Hz and see what happens. Then look at the port output alone for both tunings.

[Scarface1]

At low frequencies below resonance the air from the rear of the cone is pushing air out the port in the opposite direction to the air being moved by the front of the cone. The two sources of sound are largely cancelling hence the large cone displacement creating little sound.

Ok this makes sense i gues. So its the opposit effect as at tuning frequency ? I just wanted to know this because i tought maybe the app have some errors in it.

[andy19191]

Yes i understand and i don't want to use the sub for 20hz but just curious because they have the same spl at 20hz but ported have a lot more xmax. I understand a ported design have more spl but this is the other way around. Cone excursion = cone excursion, so why less spl at 20hz. Just for the facts !

At low frequencies below resonance the air from the rear of the cone is pushing air out the port in the opposite direction to the air being moved by the front of the cone. The two sources of sound are largely cancelling hence the large cone displacement creating little sound.

[fpitas]

Yes i understand and i don't want to use the sub for 20hz but just curious because they have the same spl at 20hz but ported have a lot more xmax. I understand a ported design have more spl but this is the other way around. Cone excursion = cone excursion, so why less spl at 20hz. Just for the facts !

You've been told already. The port is a hole in the box down there.

[Scarface1]

Yes i understand and i don't want to use the sub for 20hz but just curious because they have the same spl at 20hz but ported have a lot more xmax. I understand a ported design have more spl but this is the other way around. Cone excursion = cone excursion, so why less spl at 20hz. Just for the facts !

[billfitzmaurice]

Look at the charts again. The ported has higher output below 100Hz. At 35Hz the ported sub is 8dB louder with half the excursion. The ported sub only has higher excursion below 30Hz, where it still has a decided output advantage.

[fpitas]

Do you mean, why the ported has more xmax below the port tuning? The cone is basically unloaded there. The port has become a big hole in the box, and you won't get much sound down there, either.

[Scarface1]

Hi i was wondering why a sealed sub needs less xmax for the same spl as a ported at low frequency.

The sub is a tangband w6