American bass VFL-8" woofer depth?

[macantley]

I'm not gonna pay for bass box, but i put all the parameters that i knew into WINISD and it says ported box, with  0.86 CF and a 4 inch port  approx.24 inches long. or a 4x4 rectangle port at 32 inches long.   Pretty sure i'm gonna go with a round port at 30 inches long. and it says tuned to 39hz

 

[fithwheel]

I'm not gonna pay for bass box, but i put all the parameters that i knew into WINISD and it says ported box, with  0.86 CF and a 4 inch port  approx.24 inches long. or a 4x4 rectangle port at 32 inches long.   Pretty sure i'm gonna go with a round port at 30 inches long. and it says tuned to 39hz

port seems a little long for .86 cf net @39hz 4" round? was that a little over 4"? if just 4" i got around 35hz if not flared. Maybe i looked at it wrong idk? I paid for bass box pro and I am glad i did port length has been spot on, there is a difference between winisd port length and bbp depends on how you're doing the port.  Excursion seems more accurate to me anyway. I've had a couple of subs that I've modeled and according to winisd  they should be over excursion but not on bbp  went with bbp without issues. Group delay is different then winisd as well as vent velocity. Other stuff like impedance etc, seem close idk but yeah that length seems long if going for 39hz in that volume. If you're going with a 4'" personally I wouldn't worry about flaring seems like plenty of port area at that volume u can just smooth the edges imo but i am no expert. Also 4 looks like it'll be a little more boomy then a 3 but the 4 will give ya a little more output near tune. personally with a single 8 I'd go for as much output as you can get.

 

[macantley]

if i go with a 3 inch port it wants 12.5 inches long

 

[THATpurpleKUSH 5,000+ posts]

If you are feeding the sub a true 400rms it will max out acceptable port velocity with a 3 inch port. As far as box size, I would keep it in the range of .5-.75cf. The larger the box size the more you will have an undesirable spike in group delay around 50hz. I had to reinstall windows on my laptop and I'm having issues printing to pdf so I can't post my graph from Bass Box Pro. 

 

[macantley]

If you are feeding the sub a true 400rms it will max out acceptable port velocity with a 3 inch port. As far as box size, I would keep it in the range of .5-.75cf. The larger the box size the more you will have an undesirable spike in group delay around 50hz. I had to reinstall windows on my laptop and I'm having issues printing to pdf so I can't post my graph from Bass Box Pro. 

so is that your way of telling me that i should keep a 4 inch port?  I have a 4" port now but its only 8 inches long, so i'll either have to  extend it, or build a slot port of some sort.  After i put some internal bracing in my box to keep it stiffer it will probably be around the .75CF  after accounting for basket size and what the port itself removes from the box. 

 

[THATpurpleKUSH 5,000+ posts]

so is that your way of telling me that i should keep a 4 inch port?  I have a 4" port now but its only 8 inches long, so i'll either have to  extend it, or build a slot port of some sort.  After i put some internal bracing in my box to keep it stiffer it will probably be around the .75CF  after accounting for basket size and what the port itself removes from the box. 

I would rebuild the box allowing the space for a properly designed port. You'll probably have to do a slot port to incorporate a long port. What amp are you planning on using?

 

[macantley]

*IF* i can move my seat forward enough in the back of the truck i'm going to attempt to build an amp rack behind it to fit all 3 old school (mid 90's) orion HCCA amps, i'll use an HCCA 275R for the single 8" sub  according to the manual its 600W RMS at 2 ohm mono.   Although i'll be honest, i dont want to use the orion amps, I'd much rather have a single 5 channel amp to run everything.   I've got a memphis "big bell"  5 channel amp in my audi wagon and it does a great job. The HCCA 225's that i have could run my 4 doors and the 275 on the sub, but it seems extreme.  I've also got an american bass XD 1800 (early 2000's i think) and an american bass SQ900 (not sure what it's 2 ohm mono rating is)  i've got quite a few other amps but i dont think any of them are up to the task.    but lets just use the orion as the example for now.     The box i'm building is approx. 28 inches in length (26.5 internally)   its custom for the pickup truck so rebuilding it isnt really the best option, i could shorten the box some but then i wouldnt have the best length for a round port and i'd have to go with a slot.   *IF* i go with a round port it will be ported out the side of the box under the passenger rear seat (i dont see this being an issue as it will have about 20" or so of room between the port and the passenger rear door)  from what i'm reading i need about 4" of room between the port  and the inside wall of the box  so that i'lll have plenty of room for air movement.  so given that recommendation from box desing, i can be no longer than  23.25 inches on my port length.   although it does seem that the larger the box, the shorter my port length is.   I guess i need to finish building the box and get the 100% accurate measurement of the airspace inside of it then remove what space the port will be taking up. 

 

[macantley]

finished building the box other than cutting the hole for the round port, I estimated that a 4 inch port at 20 inches long is approx. 0.15 cubic foot of air space, the box itself is 1.05 CF, and the subwoofer takes up 0.10 CF, so if i port the box it will be 0.80 CF of space, *IF* i tune the box to 37HZ i can add a few more inches to the port and the box will be approx. 0.76 CF of air space  which i think would be optimum  from what i'm reading, almost every sub box i've viewed on Youtube that runs the american bass VFL subs is between 0.75 and 0.80 CF per sub. and they are ported. 

 

[THATpurpleKUSH 5,000+ posts]

finished building the box other than cutting the hole for the round port, I estimated that a 4 inch port at 20 inches long is approx. 0.15 cubic foot of air space, the box itself is 1.05 CF, and the subwoofer takes up 0.10 CF, so if i port the box it will be 0.80 CF of space, *IF* i tune the box to 37HZ i can add a few more inches to the port and the box will be approx. 0.76 CF of air space  which i think would be optimum  from what i'm reading, almost every sub box i've viewed on Youtube that runs the american bass VFL subs is between 0.75 and 0.80 CF per sub. and they are ported. 

Are you using sch 40 pvc for the port? 

A 20inch long port thats flush with the side of the box and made from sch40 pvc is .0787cf. 

.5-.75 is optimal for that sub, the larger you go the boomier it will sound and the faster it will reach its max excursion. It sounds like it will be slightly under to right around its rms power with any of the amps you have. 

In general, the larger the box size the shorter the port will need to be when cross section area stays the same. 

 

[macantley]

Are you using sch 40 pvc for the port? 

A 20inch long port thats flush with the side of the box and made from sch40 pvc is .0787cf. 

.5-.75 is optimal for that sub, the larger you go the boomier it will sound and the faster it will reach its max excursion. It sounds like it will be slightly under to right around its rms power with any of the amps you have. 

In general, the larger the box size the shorter the port will need to be when cross section area stays the same. 

thanks, i just realized i forgot to take in account that schedule 40 pipe is actually 4.5" in diameter due to the thickness of the pipe which also affects my cubic feet.  I'm going to have to measure to double check that i can fit a 4.5" pipe inside the box through the brace i made inside of it, i'm pretty sure i can, but i mostly accounted for 4.125" and was planning on screwing some screws through the pipe then cutting off the access of the screws. so the pipe will be rigid inside the box. Either way it's gonna wait till tomorrow, its damn cold outside now. 

 

[THATpurpleKUSH 5,000+ posts]

Finally got print to pdf to work, here's a comparo of .5 and 1cf with tunes of 35 and 40hz for each volume to give you an idea of performance.

View attachment VFL8 plot.pdf

 

[THATpurpleKUSH 5,000+ posts]

Those were all with a 3 inch aeroport (flared ends) btw

 

[macantley]

I went a bit off script here and made the port 15.5" long with a 3" schedule 40 PVC pipe, so the box is a bit oversized but i just tested the sub in my home theatre room and it sounds pretty bad ass for a single 8" sub, out of curiosity i had my son cover up and hold the port closed while i was playing some music and it cut the output down so much that it was pretty pathetic.  Granted the box is completely too large for a sealed enclosure.   I Cant wait till i get my amps setup and everything mounted and carpeted in the truck.   I really appreciate the help, i would have never been able to get the sound output right without you guys. 
from what i'm seeing it should be tuned to "around" 34HZ
matthew

 

[THATpurpleKUSH 5,000+ posts]

I went a bit off script here and made the port 15.5" long with a 3" schedule 40 PVC pipe, so the box is a bit oversized but i just tested the sub in my home theatre room and it sounds pretty bad ass for a single 8" sub, out of curiosity i had my son cover up and hold the port closed while i was playing some music and it cut the output down so much that it was pretty pathetic.  Granted the box is completely too large for a sealed enclosure.   I Cant wait till i get my amps setup and everything mounted and carpeted in the truck.   I really appreciate the help, i would have never been able to get the sound output right without you guys. 
from what i'm seeing it should be tuned to "around" 34HZ
matthew

What are the outer dimensions and wall thickness of the enclosure?

 

[macantley]

the front is 28.25" x 9.25" and its double thick 3/4" MDF

the back is 6.5" x 28.14" 3/4" MDF

the top is 14.5" x 28.25" 

the bottom is 13.75" x 28.25"  (so it has a bit of a wedge shape because of the front/rear height difference) 

there is also a notch cut out of the bottom on one side thats  14" x  8" x 1.375"  (had to get the box over the center up in the floor for the driveshaft/transmission)

once i have the box carpeted and everything installed i'll probably post a picture up on the forums.