15" xfl Trunk install opinions.

[ancorp 10+ year member]

The gain is not a volume knob. Setting it to 75% wont give you 75% power. It's to match the head units output. With some head units you could get full power out of the amp at the gain at 25% if not lower.

The box sounds great to me. But if you stick that huge port into the ski pass, there won't be much area left for the rest of the sound to come through, and you will mostly get notes near the port tuning. I suggest you still open up your rear deck if you can.

Or you could build a 4th order box where everything comes out of the port, but I doubt you can fit a 4th order for a 15". You'd need at least 6 cubes. I would consider doing two XFL 10s in a 4th order in that vehicle with a rectangular port that fits the maximum size of the ski pass. Then you will have no trunk rattle at all, and the two coils will take the 2400w without a sweat. I'd start with building 1.5 cubes sealed, 3 cubes ported at 45-50hz or so, but people with actual 4th order XFL experience can chime in.

 

[rickymac21 10+ year member]

The gain is not a volume knob. Setting it to 75% wont give you 75% power. It's to match the head units output. With some head units you could get full power out of the amp at the gain at 25% if not lower.
The box sounds great to me. But if you stick that huge port into the ski pass, there won't be much area left for the rest of the sound to come through, and you will mostly get notes near the port tuning. I suggest you still open up your rear deck if you can.

Or you could build a 4th order box where everything comes out of the port, but I doubt you can fit a 4th order for a 15". You'd need at least 6 cubes. I would consider doing two XFL 10s in a 4th order in that vehicle with a rectangular port that fits the maximum size of the ski pass. Then you will have no trunk rattle at all, and the two coils will take the 2400w without a sweat. I'd start with building 1.5 cubes sealed, 3 cubes ported at 45-50hz or so, but people with actual 4th order XFL experience can chime in.

Thanks for the heads up.. I'm not sure how I never knew this. Ignorance I guess. But I just did some reading and gave myself a quick lesson on the gain....

But if my amp is rated at 1600w rms at 2 ohms that would that be under-powering the XFL ? I was told 1800w rms is good for the sub so 1600 isn't much lower...

As for the making a 4th order box, I'm not opposed but from what I understand those usually only play well through a short range.??? I've never built one though so it would be fun to try, especially if you say it'll reduce trunk rattle.

 

[bbeljefe]

2 6" ports for 4 cubes is almost double the average 8 sq in per cubic ft. But as far as the power issue, I've been told the Cfl's can handle 1800w Rms all day. So why couldn't I just wire it to 1 ohm and set the gain lower on the amp? This would help prevent clipping as well.

For high powered subs the average is 16 in² per cubic foot. I would keep the box small and use a square or slot port... that way you can get the size you need and you can easily configure it so that it fires through the package tray if that's what you want to do.

 

[97maxima 10+ year member]

Have you ran the xfl 15? If so please explain to me what your box was like.. cubes? port area? tuning?
I would imagine with my stock 120a alternator and nothing more than 2 batteries and the big 3 i'll be fine on electrical... But I seriously doubt that the BRX2400 will really do 2400w rms at 1 ohm. I bet it's more like 1800 @ 12v. . . Which is what i'll be running on most likely (havent checked my cars voltage)... But even if the amp does put out 2000rms @ 1ohm why can't I just set the gain down on the amp to reduce the power?

I guess my other option would be to just buy the D4 ohm xfl and wire it to 2 ohms, but I don't want to do that because I'd have to turn the gain up on the amp and I don't want to risk clipping the amp or sub...

How about this. ..
4.25 cubic ft box

8" aero port tuned to 34 hz

Sub wired to 1ohm

Amp gain set to 75-80%

Sub firing up and port firing foward into cabin (through ski hole)

?????????????

Everything ive said as far as specs is a good guide line for the xfls, as ive said before 4.25 is a tad too big. id run the amp at 1 ohm if you have access to a dd-1 or a scope id set your amp that way. cant go off oh i turned the knob this much its ok, you would be surprised how quickly you can become hard clipped past 1/4 gain

The gain is not a volume knob. Setting it to 75% wont give you 75% power. It's to match the head units output. With some head units you could get full power out of the amp at the gain at 25% if not lower.
The box sounds great to me. But if you stick that huge port into the ski pass, there won't be much area left for the rest of the sound to come through, and you will mostly get notes near the port tuning. I suggest you still open up your rear deck if you can.

Or you could build a 4th order box where everything comes out of the port, but I doubt you can fit a 4th order for a 15". You'd need at least 6 cubes. I would consider doing two XFL 10s in a 4th order in that vehicle with a rectangular port that fits the maximum size of the ski pass. Then you will have no trunk rattle at all, and the two coils will take the 2400w without a sweat. I'd start with building 1.5 cubes sealed, 3 cubes ported at 45-50hz or so, but people with actual 4th order XFL experience can chime in.

This would also work^

 

[rickymac21 10+ year member]

Originally Posted by ancorp
Or you could build a 4th order box where everything comes out of the port, but I doubt you can fit a 4th order for a 15". You'd need at least 6 cubes. I would consider doing two XFL 10s in a 4th order in that vehicle with a rectangular port that fits the maximum size of the ski pass. Then you will have no trunk rattle at all, and the two coils will take the 2400w without a sweat. I'd start with building 1.5 cubes sealed, 3 cubes ported at 45-50hz or so, but people with actual 4th order XFL experience can chime in.

This would also work^

I like the 4th order idea.. I have also wanted to build one but I know there's a lot more to factor in (sub specs) and I'm just not sure how to go about it... Everyone I've read ratios 1:2 (sealedorted) 1:3 (sealedorted) and some others too... And apparently that's what makes it difficult, there's no golden ratio...

But since you have experience with the XFL's, would you suggest that ancorp's idea is pretty accurate as far as ratio's for the 4th order? If so how many cubes sealed/ported for the 15?

I know I read that the larger the sealed box is (compared to the ported chamber) the lower the sub will play ?? would 2 cubes sealed, 4 cubes ported be good? tuned to 45 hz

Sorry guys, just trying to figure this out....

 

[97maxima 10+ year member]

For a 15 id do 2.25 sealed and 4.5 ported or larger around 1/3 cone area for port which works out to about 14 sq in of port per cube.So 60 ish sq in. tuned in the 45-50hz range

 

[bbeljefe]

Prefab 4th orders are the ones that give 4th orders the reputation for being peaky, narrow bandwidth burp boxes. That and poorly designed custom ones.

The thing about 4th and 6th order boxes is that you need to spend some time modeling different configurations and tuning frequencies until you get a wide, smooth passband for the specific driver(s) you're designing it for. Sometimes that means modeling three boxes and sometimes that means modeling thirty boxes. But, you only have to design it once.

And one thing I've found is that I have better luck tuning below the normal 45-50 hz range. Mid to high thirties has been good for most drivers I've done them for.

 

[rickymac21 10+ year member]

Prefab 4th orders are the ones that give 4th orders the reputation for being peaky, narrow bandwidth burp boxes. That and poorly designed custom ones.
The thing about 4th and 6th order boxes is that you need to spend some time modeling different configurations and tuning frequencies until you get a wide, smooth passband for the specific driver(s) you're designing it for. Sometimes that means modeling three boxes and sometimes that means modeling thirty boxes. But, you only have to design it once.

And one thing I've found is that I have better luck tuning below the normal 45-50 hz range. Mid to high thirties has been good for most drivers I've done them for.

I am aware that there are many more things to factor in when building one... But is it really impossible to have a general size? I'm not competing, just like to demo and jam... I know that the FS and QTS is in the range for a 4th order... And if I have my net box volume down to the point when I tune the box, I would have to have a "decent" response? If not I can just mess around with different port lengths right??? Do you personally have any suggestions for this particular sub??

For a 15 id do 2.25 sealed and 4.5 ported or larger around 1/3 cone area for port which works out to about 14 sq in of port per cube.So 60 ish sq in. tuned in the 45-50hz range

Is this coming from experience? A recent calculation ? or is this just something general that tends to work with a sub of this size/power??

And just to be clear, the bandpass box would allow the sub to handle more power since it's partially sealed correct?

 

[97maxima 10+ year member]

Is this coming from experience? A recent calculation ? or is this just something general that tends to work with a sub of this size/power??

And just to be clear, the bandpass box would allow the sub to handle more power since it's partially sealed correct?

All the above, they tend to like a larger sealed section compared to other subs. Has to do with their bl strength which is middle of the road.They will have more cone control and will get pretty loud off not much power. They still will handle a good bit tho. Built one a while back for a pair of xfl 12s firing into the cabin. Very enjoyable listening experience

 

[rickymac21 10+ year member]

Well It's settled then.... 4th order it is with the port firing through the ski hole !!!! Thanks maxima for staying in here with me and helping me out ! I really do appreciate all the help and advice.

I have a box designed already ... Just need to know two small things.

1. For port area I know you said about 14 sq in of port per cube... The 'per cube' only pertains to the ported section correct? Might be stupid question but thought I'd ask...

2. Tuning the port is the same as tuning a regular ported box?

 

[bbeljefe]

I am aware that there are many more things to factor in when building one... But is it really impossible to have a general size? I'm not competing, just like to demo and jam... I know that the FS and QTS is in the range for a 4th order... And if I have my net box volume down to the point when I tune the box, I would have to have a "decent" response? If not I can just mess around with different port lengths right??? Do you personally have any suggestions for this particular sub??

I don't have any for that sub now but if you decide whether you want to do one of their 15s or two of their tens, I'll be more than happy to model some boxes for you. Just lemme know what driver and how many.

And yeah, once you have a good ratio for the driver you're building for, you can tweak the tuning with an aero port or some other removable port design.

 

[97maxima 10+ year member]

Well It's settled then.... 4th order it is with the port firing through the ski hole !!!! Thanks maxima for staying in here with me and helping me out ! I really do appreciate all the help and advice.
I have a box designed already ... Just need to know two small things.

1. For port area I know you said about 14 sq in of port per cube... The 'per cube' only pertains to the ported section correct? Might be stupid question but thought I'd ask...

2. Tuning the port is the same as tuning a regular ported box?

np, yep so 14*4.5=63 sq in. Its the same but since you typically use less port area and a higher tuning you end up with a pretty short port.

 

[rickymac21 10+ year member]

np, yep so 14*4.5=63 sq in. Its the same but since you typically use less port area and a higher tuning you end up with a pretty short port.

Cool... Thanks again... Carstereo.com is telling me a box 4.5 cubes with an 8"x8" square port will need to be 15.12" long to get 42 hz.... seems like a long port.. That port will take up about a .5 cubes of airspace...

 

[rickymac21 10+ year member]

I don't have any for that sub now but if you decide whether you want to do one of their 15s or two of their tens, I'll be more than happy to model some boxes for you. Just lemme know what driver and how many.
And yeah, once you have a good ratio for the driver you're building for, you can tweak the tuning with an aero port or some other removable port design.

This is for the 15" ... XFL1544 ...

 

[97maxima 10+ year member]

Cool... Thanks again... Carstereo.com is telling me a box 4.5 cubes with an 8"x8" square port will need to be 15.12" long to get 42 hz.... seems like a long port.. That port will take up about a .5 cubes of airspace...

thats accurate id bring the tuning up some if you cant afford the length. also if the port is external that would be better