Hello
I'm in the process of designing a subwoofer to house my old car sub, a Hertz ES 300D.
I've settled on 80 liters of internal volume and I'd like to reach atleast 100dB of output before cone / power limitations, preferably as flat as possible and getting usable response at 20hz.
I'm currently modelling the model in WinISD and I realised multiple small round ports are vastly superior to using one long slotted port.
However this is only the case if I tick the " Use transmission-line model for port simulation". Disabling this doesn't change the slotted port version much, but drastically changes the small round port model.
Slotted port (tuned to 22hz. Blue legend):
400mm x 40mm, 130cm long
Multiple round ports (tuned to 35hz. Orange legend):
4 x 57mm diameter, 27cm long
I've added multiple EQs to get the response flat. Heres the response with the transmission line model sim turned on:
Here's with the transmission line model sim turned off:
Not only is the response much different, the cone excursion is absolutely out of bounds with the multiple round ports. If disabling the transmission line sim is closer to reality, this design is horrible.
What gives, what should I trust?
I have some additional questions; The sub is going to be in an apartment room, roughly 4.5m x 3.5m x 2.5m. How will room gain influence the response? I'm assuming it will boost the low end significantly.
I'm in the process of designing a subwoofer to house my old car sub, a Hertz ES 300D.
I've settled on 80 liters of internal volume and I'd like to reach atleast 100dB of output before cone / power limitations, preferably as flat as possible and getting usable response at 20hz.
I'm currently modelling the model in WinISD and I realised multiple small round ports are vastly superior to using one long slotted port.
However this is only the case if I tick the " Use transmission-line model for port simulation". Disabling this doesn't change the slotted port version much, but drastically changes the small round port model.
Slotted port (tuned to 22hz. Blue legend):
400mm x 40mm, 130cm long
Multiple round ports (tuned to 35hz. Orange legend):
4 x 57mm diameter, 27cm long
I've added multiple EQs to get the response flat. Heres the response with the transmission line model sim turned on:
An externally hosted image should be here but it was not working when we last tested it.
Here's with the transmission line model sim turned off:
An externally hosted image should be here but it was not working when we last tested it.
Not only is the response much different, the cone excursion is absolutely out of bounds with the multiple round ports. If disabling the transmission line sim is closer to reality, this design is horrible.
What gives, what should I trust?
I have some additional questions; The sub is going to be in an apartment room, roughly 4.5m x 3.5m x 2.5m. How will room gain influence the response? I'm assuming it will boost the low end significantly.
Last edited:
Greets!
A vent is a 1/2 WL TL resonator, so has both odd and even harmonics that comb filters with the driver's output as shown by the phase flop spikes, different response, so definitely more accurate than without. If you want to quell them, 'critically' damp the vent with an impulse response of some sort to get ~ the smooth response. The old DIY way before cheap measurement software became the norm: Click Test | GM210 | Flickr
Room gain is dependent on its size, construction, though living where you do I imagine it's quite robust, so could get a lot closer to the ~ 9 dB corner limit than in my locale where it's more like 4-5 dB for the majority. Room modes really mess with bass response, so just have to use either room EQ or use one of the experimental ways to find where it works best overall.
GM
A vent is a 1/2 WL TL resonator, so has both odd and even harmonics that comb filters with the driver's output as shown by the phase flop spikes, different response, so definitely more accurate than without. If you want to quell them, 'critically' damp the vent with an impulse response of some sort to get ~ the smooth response. The old DIY way before cheap measurement software became the norm: Click Test | GM210 | Flickr
Room gain is dependent on its size, construction, though living where you do I imagine it's quite robust, so could get a lot closer to the ~ 9 dB corner limit than in my locale where it's more like 4-5 dB for the majority. Room modes really mess with bass response, so just have to use either room EQ or use one of the experimental ways to find where it works best overall.
GM