4th order questions

[akuma4u]

Hey

i have some questions regarding 4th orders

1) should the 4th order tuning be done 2-3hz under the resonant frequency of the car? Is this how the tuning freq is determined?

2) my cars resonant freq is 55hz, so if i tune the 4th to 52hz, what frequency bands will it be hitting?

3) i was told 4ths are not musical at all and are mainly just for high SPL and burping.. is this true? if so, is there any way to make the 4th both musical for daily listening AND loud for decent SPL? (more than what a ported box would deliver)

4) is there a sweet spot for ratio between sealed and ported? like is 1:2.5 a good ratio?

5) direction of port: If the port is aimed up through the rear deck versus aiming forward through the hole when the seats are down, will this cause a difference in bass impact or quality if i do one over the other? or will it sound the same? i have a feeling aiming it forward will make the bass hit the passengers harder as the waves are just moving forward directly towards the driver/passenger. I may be screwed and have no choice but to aim the port up through the rear deck.. would this still be decent and get the job done or would it not be recommended ?

thanks!

[RooTxBeeR]

Tuning of the ported section should be the resonant frequency of the sealed section.

Edit, 4ths can be musical as shit

[akuma4u]

Tuning of the ported section should be the resonant frequency of the sealed section.

Edit, 4ths can be musical as shit

how does one achieve a blend of musicality and SPL? lower tuning?

[hdorre]

i have some questions regarding 4th orders

1) should the 4th order tuning be done 2-3hz under the resonant frequency of the car? Is this how the tuning freq is determined?

2) my cars resonant freq is 55hz, so if i tune the 4th to 52hz, what frequency bands will it be hitting?

3) i was told 4ths are not musical at all and are mainly just for high SPL and burping.. is this true? if so, is there any way to make the 4th both musical for daily listening AND loud for decent SPL? (more than what a ported box would deliver)

4) is there a sweet spot for ratio between sealed and ported? like is 1:2.5 a good ratio?

5) direction of port: If the port is aimed up through the rear deck versus aiming forward through the hole when the seats are down, will this cause a difference in bass impact or quality if i do one over the other? or will it sound the same? i have a feeling aiming it forward will make the bass hit the passengers harder as the waves are just moving forward directly towards the driver/passenger. I may be screwed and have no choice but to aim the port up through the rear deck.. would this still be decent and get the job done or would it not be recommended ?

thanks!

1/2) You should tune the ported chamber to the resonant freq of the sealed. You generally want your sealed chamber as big as possible, without sacrificing mechanical cone control. Torn triple joints and munched cones arent good. As your sealed chamber volume increases, the resonance decreases, but efficiency increases.

3) My 4th played 25-55, one team mate plays 15-40, another team mate plays 18-45, an additional team mate plays low 20s to like 45. Thats musical to me. Also, 4ths tend to be more musical by nature than ported boxes, due to a flatter response in their passband.

4) I loveeee 3:1 - 4:1. But dont overthink your ratio. Only thing is that I wouldnt do less than like 2.5 - 2.75:1

5) If you port through your rear deck, you may need to cut some of your cars factory bracing. The up side is that the rear window may act as something for the port to load against.

[akuma4u]

i have some questions regarding 4th orders

1) should the 4th order tuning be done 2-3hz under the resonant frequency of the car? Is this how the tuning freq is determined?

2) my cars resonant freq is 55hz, so if i tune the 4th to 52hz, what frequency bands will it be hitting?

3) i was told 4ths are not musical at all and are mainly just for high SPL and burping.. is this true? if so, is there any way to make the 4th both musical for daily listening AND loud for decent SPL? (more than what a ported box would deliver)

4) is there a sweet spot for ratio between sealed and ported? like is 1:2.5 a good ratio?

5) direction of port: If the port is aimed up through the rear deck versus aiming forward through the hole when the seats are down, will this cause a difference in bass impact or quality if i do one over the other? or will it sound the same? i have a feeling aiming it forward will make the bass hit the passengers harder as the waves are just moving forward directly towards the driver/passenger. I may be screwed and have no choice but to aim the port up through the rear deck.. would this still be decent and get the job done or would it not be recommended ?

thanks!

1/2) You should tune the ported chamber to the resonant freq of the sealed. You generally want your sealed chamber as big as possible, without sacrificing mechanical cone control. Torn triple joints and munched cones arent good. As your sealed chamber volume increases, the resonance decreases, but efficiency increases.

3) My 4th played 25-55, one team mate plays 15-40, another team mate plays 18-45, an additional team mate plays low 20s to like 45. Thats musical to me. Also, 4ths tend to be more musical by nature than ported boxes, due to a flatter response in their passband.

4) I loveeee 3:1 - 4:1. But dont overthink your ratio. Only thing is that I wouldnt do less than like 2.5 - 2.75:1

5) If you port through your rear deck, you may need to cut some of your cars factory bracing. The up side is that the rear window may act as something for the port to load against.

i want mine to also play 25-55 range.. but i guess thats not up for me to decide but rather the cars resonant frequency to decide. Unless i can screw the resonant freq and just pick the same tuning you did... but i doubt that would give me the same 25-55 range you got in your car.

I am doing 2 SA 12s ,.. this guy in the video also did 2 sa12s and he did 2 cubes sealed to 2.5 cubes ported...15"H x 36"W x 28"D and it looks like it slams..

regarding the rear deck.. YES a hole has already been cut from my previous system and it did not go thru any vital factory bracing or anything so its good..

[Triticum Agricolam]

Ratios are meaningless. Both chambers need to be sized independently. Like others have said, 4th order band pass boxes can be very musical, but this is a lot harder to do with a low QTS and low Vas sub. Higher QTS and higher Vas subs make it easier.

Band pass boxes let you trade bandwidth for efficiency. You can get a balance of the two up to a point, but if you want to maximize one aspect you have to sacrifice the other.

[akuma4u]

Ratios are meaningless. Both chambers need to be sized independently. Like others have said, 4th order band pass boxes can be very musical, but this is a lot harder to do with a low QTS and low Vas sub. Higher QTS and higher Vas subs make it easier.

Band pass boxes let you trade bandwidth for efficiency. You can get a balance of the two up to a point, but if you want to maximize one aspect you have to sacrifice the other.

is the sa 12 a low qts low vas sub?

[reedal]

http://www.stevemeadedesigns.com/board/topic/204690-a-pair-of-10s-that-will-slam-in-under-3-4-cubes/?view=findpost&p=3103049

You said you don't have enough room for a regular ported enclosure for those 12's, and now you want to do a 4th, which takes up more space? How does that work exactly?

[akuma4u]

http://www.stevemeadedesigns.com/board/topic/204690-a-pair-of-10s-that-will-slam-in-under-3-4-cubes/?view=findpost&p=3103049

You said you don't have enough room for a regular ported enclosure for those 12's, and now you want to do a 4th, which takes up more space? How does that work exactly?

i went and got a second opinion from a different box builder/installer and once removing the spare tire, and jack and false floor, a lot of extra room is created and he took measurements and said there was enough room to do a 4th and said it would be the best route as the car already has issues getting bass into the cabin and because there has already been a square hole cut into the rear deck lid. He said porting thru that hole in the rear deck will spill all the bass into the cabin and will solve the issue of not gettin enough bass into the cabin.

[Triticum Agricolam]

is the sa 12 a low qts low vas sub?

It's QTS is around .5, which is pretty moderate. A .5 QTS should be fine for 4th order band pass. The Vas is about 24 liters, which is on the low side for a 12" sub. This is going to make the output more peaky and will make it harder to get a wide bandwidth.