4th order questions

[akuma4u]

With 2.5 cu ft sealed, the sealed resonance is going to be about 48 Hz. Tuning there will give you the flattest response, it may not play as low as you would like though, so you may want to tune more like 44 Hz. I'd suggest making your port adjustable so you can tweak things once you get the system playing in your vehicle.

I think that box should perform well for you, buts not going to beat a ported box, either for max output or smooth frequency response. For use in vehicles 4th order bandpass boxes have one advantage over a ported box, they let you push all the output through the port, which when you need that ability its a very handy thing to have. When it comes to performance though, ported boxes are better at turning space into bass.

yet again i have been told misleading info, i was told a 4th has the most output and easily outperforms a standard ported box. Thats one of the reasons i was looking forward to doing a 4th. The second reason i was looking forward to doing a 4th , and this is the MAIN reason, is because extending that port upwards into my rear deck where a square hole has already been cut out, it will (hopefully and theoretically) solve my issue with the bass trap trunk. Having this port come up and into the cabin will allow all the bass to come into the cabin instead of half stuck in trunk and half into cabin. Hopefully it will put all the bass where it belongs. Plus i will be able to have my rear seats up all the time as well.

So, if i were to do a regular ported - even if it may have more output or quality etc,.. a big portion of that output would be eaten up and lost in my crappy bass trap trunk (yes, even when the seats are down).

now - im a little confused about the resonant freq. I was told the tuning has to be a few hz under the cars resonant freq. But you have been able to figure out the sealed chambers resonant freq without even being in my car.. the guy in the video tuned his to 45hz or 43 hz i forgot , but i did go thru his comments and he said that was for HIS car and if it was in other peoples cars it prob wouldnt have sounded as good because you have to tune it to the res freq of the specific car its going into.

I did find out from a buddy with the same car as mine that the res freq of my car is 55hz.. so does that mean i should tune it to 52hz? or should i still do 44hz? little confused on that.

thanks

[Joe X]

The sealed resonance and the vehicle resonant frequency are two very different things, I guess there is a way to match them but that could result in a very peaky setup.

[reedal]

You can do a regular ported enclosure and have the port come through the trunk the exact same way you would with the 4th. The difference would be you wouldn't have a sealed section, and you would tune the port to a lower frequency of your choice based on the frequencies you want to play

[akuma4u]

You can do a regular ported enclosure and have the port come through the trunk the exact same way you would with the 4th. The difference would be you wouldn't have a sealed section, and you would tune the port to a lower frequency of your choice based on the frequencies you want to play

ya but , correct me if im wrong, but with a 4th 100% of the sound/bass comes out of the port , whereas in a ported box sound/bass comes out of the port and the subs. Right?

[akuma4u]

The sealed resonance and the vehicle resonant frequency are two very different things, I guess there is a way to match them but that could result in a very peaky setup.

so then what is the correct way to calculate the tuning of a 4th? to the sealed or to the vehicles resonant freq?

[Joe X]

You would measure your vehicle's transfer function and feed the data to modeling software, that would give you an idea of what needs to be done with chamber sizes, tuning, port area etc.

[Triticum Agricolam]

The sealed resonance and the vehicle resonant frequency are two very different things, I guess there is a way to match them but that could result in a very peaky setup.

so then what is the correct way to calculate the tuning of a 4th? to the sealed or to the vehicles resonant freq?

There isn't one correct way, there are a lot of variables that will influence what frequency will be best. This is why I suggest you tweak it once you get the system playing. Joe X's suggestion of measuring your vehicles transfer function and using that with software should help you get closer to where you want to be before you get to the trial and error stage.

Let me expand on what I saying earlier, when I said a 4th order bandpass won't outperform a ported box I was speaking in terms of raw output. With your vehicle you have a limitation getting the sound into the cabin. In your case a bandpass box may give you better performance than a ported box would.

[reedal]

You can do a regular ported enclosure and have the port come through the trunk the exact same way you would with the 4th. The difference would be you wouldn't have a sealed section, and you would tune the port to a lower frequency of your choice based on the frequencies you want to play

ya but , correct me if im wrong, but with a 4th 100% of the sound/bass comes out of the port , whereas in a ported box sound/bass comes out of the port and the subs. Right?

Yes.

[akuma4u]

The sealed resonance and the vehicle resonant frequency are two very different things, I guess there is a way to match them but that could result in a very peaky setup.

so then what is the correct way to calculate the tuning of a 4th? to the sealed or to the vehicles resonant freq?

There isn't one correct way, there are a lot of variables that will influence what frequency will be best. This is why I suggest you tweak it once you get the system playing. Joe X's suggestion of measuring your vehicles transfer function and using that with software should help you get closer to where you want to be before you get to the trial and error stage.

Let me expand on what I saying earlier, when I said a 4th order bandpass won't outperform a ported box I was speaking in terms of raw output. With your vehicle you have a limitation getting the sound into the cabin. In your case a bandpass box may give you better performance than a ported box would.

You can do a regular ported enclosure and have the port come through the trunk the exact same way you would with the 4th. The difference would be you wouldn't have a sealed section, and you would tune the port to a lower frequency of your choice based on the frequencies you want to play

ya but , correct me if im wrong, but with a 4th 100% of the sound/bass comes out of the port , whereas in a ported box sound/bass comes out of the port and the subs. Right?

Yes.

Then 4th it is.