my Kappa build

[just-some-guy]

thanx, i'll search.

that vent. i think i would make a hole in the wool and wood behind the driver.

 

[just-some-guy]

ok, i have another question.

the standard kappa build is 5.9cf. mine is 6.1cf. the standard port is 12.5 x 3 x 55".
i was told to use a 11.5 x 3 x 27" port. seeing as how the box's have the same, basicly, cf. why would my port not be the same ? trying to learn. thanx

 

[WmAx]

ok, i have another question.

the standard kappa build is 5.9cf. mine is 6.1cf. the standard port is 12.5 x 3 x 55".
i was told to use a 11.5 x 3 x 27" port. seeing as how the box's have the same, basicly, cf. why would my port not be the same ? trying to learn. thanx

Are you using a Kappa driver? If so, the 11.5 x 3 x 27" port is going to be a disaster. It will cause the response to fall down after 28Hz, and it will have a large resonant peak around 28-30Hz resulting in a 'boom-box' type response, not precision bass. The avaserfi design is correct. Do not attempt to modify it without understanding the physical interaction that will take place between the driver and altered design.

-Chris

 

[just-some-guy]

yes. the PERFECT 12.1. and by my humble testing, it does what you say.

so, what you are saying. even though my box is a little(?) different shape, i should use the original port size ?

 

[just-some-guy]

i just fixed my hum !!! WooHoo !!! i rerouted my rca's away from everything, and the drivers are dead quiet. and it seems there is more output, but that very well could be because they are in the corners. as opposed to the middle of the room as before.

 

[lsiberian]

Are you using a Kappa driver? If so, the 11.5 x 3 x 27" port is going to be a disaster. It will cause the response to fall down after 28Hz, and it will have a large resonant peak around 28-30Hz resulting in a 'boom-box' type response, not precision bass. The avaserfi design is correct. Do not attempt to modify it without understanding the physical interaction that will take place between the driver and altered design.

-Chris

He's using the 12.1 Perfect Driver so I think he'll be ok. The high pass filter set at 20hz should correct the peak according to WinISD modeling. And for the Simple 12.1 it's only 1 or 2 db even without a filter.
Though modeling and reality are very different things. If you've built the boxes. Go ahead and give them a try.
Make sure you use the rockwool!

If you don't like your sound then you will want to lengthen the port.

I do suggest sticking to that design though. You sacrifice extension by making the port shorter.

 

[just-some-guy]

ok. i just made the ports about 55". i say "about" because i never got an answer to my question = measure the inside or outside of the bend. so i went with the outside. its not all glued together yet, so i can change if needed. i have a bag of mineral wool. that will go in when the top is ready to be glued on.

 

[lsiberian]

ok. i just made the ports about 55". i say "about" because i never got an answer to my question = measure the inside or outside of the bend. so i went with the outside. its not all glued together yet, so i can change if needed. i have a bag of mineral wool. that will go in when the top is ready to be glued on.

Port bottom:
2x 18" x 3"
17.25" x 14"
Port back:
2x 24" x 3"
18" x 14"
Port top:
2x 13.75" x 3"
13" x 14"

Cut these pieces to get the proper port size.

As you can see with the 3" x 12.5" port the length of it is 55" when the interior length is 17.25" + 18" + 13" = 48.25" + 1.5" = 49.75" For the edges. That will give you the 55" port.

As you can tell to get the outside wall one simple adds about 6" for every turn

coming to around 61.75" Then you add the 2 together and divide. 61.75" + 49.75" = 111.50" /2 = 55.25" Which is close enough to 55" that it's simpler to round down. .25" length is negligible.

So basically its the length of the middle of the port.

 

[WmAx]

He's using the 12.1 Perfect Driver so I think he'll be ok.

Incorrect. The 12.1 Kappa behaves almost identical to the Kappa 12VQ. That is, both will have the same response, within 1 dB of each other in the same cabinet system.

-Chris

 

[WmAx]

ok. i just made the ports about 55". i say "about" because i never got an answer to my question = measure the inside or outside of the bend. so i went with the outside. its not all glued together yet, so i can change if needed. i have a bag of mineral wool. that will go in when the top is ready to be glued on.

Actually, length refers to the imaginary 'middle' line of the port. But a 55" long port ending up with an error in length +/- 1" will have very little effect on the final response. So don't worry about small errors in length. But be sure to keep width and height of the port consistent and accurate.

-Chris

 

[just-some-guy]

thanx fellas. i just measured the middle. it turns out i have 59". cutting this down is not an issue. but, what would be the effect of leaving it ? just trying to learn.

also. that board that is in the middle of the box, that the rockwool is attached to. is there some kind of formula for placing it "exactly" ?

and. is there any advantage to using more wool in the box ?

 

[lsiberian]

thanx fellas. i just measured the middle. it turns out i have 59". cutting this down is not an issue. but, what would be the effect of leaving it ? just trying to learn.

also. that board that is in the middle of the box, that the rockwool is attached to. is there some kind of formula for placing it "exactly" ?

and. is there any advantage to using more wool in the box ?

It would slightly improve extension, but not enough to be noticeable IMO.

 

[sawzalot]

thanx fellas. i just measured the middle. it turns out i have 59". cutting this down is not an issue. but, what would be the effect of leaving it ? just trying to learn.

also. that board that is in the middle of the box, that the rockwool is attached to. is there some kind of formula for placing it "exactly" ?

and. is there any advantage to using more wool in the box ?

That large brace will only fit one way ,it butts up to the sides and fits between the ports top of the bottom port up to the bottom of the top port,lol,that sounds funny but its where it fits.and the small brace is the same length and the cut sheet gives you the rip or width that butts up to the port going up the back the push the large brace up to the small brace.

 

[lsiberian]

thanx fellas. i just measured the middle. it turns out i have 59". cutting this down is not an issue. but, what would be the effect of leaving it ? just trying to learn.

also. that board that is in the middle of the box, that the rockwool is attached to. is there some kind of formula for placing it "exactly" ?

and. is there any advantage to using more wool in the box ?

To answer the wool question there is always an advantage to more wool, but I wouldn't put it too close to the driver. Give it plenty of clearance.

 

[just-some-guy]

ok. where would be good places to add some ? i have some old pillow cases that i am going to put the wool in (holding the shape of the wool). then glueing that to the box.

 

[WmAx]

ok. where would be good places to add some ? i have some old pillow cases that i am going to put the wool in (holding the shape of the wool). then glueing that to the box.

Note: Too much dampening will result in the port actually reducing it's output level. I recommend 2" on most walls, reserving 4" thick for just the bottom and the back(behind driver) IF you have space. You can alternately place 4" on just one of the sides if their is not enough space behind the driver. In this case, just use 2" behind the driver. I am assuming you are using the high density rock/mineral wool (4-8lb/ft^3 range).

-Chris

 

[lsiberian]

Honestly I think you'd be better using the extra wool for room treatments if you can get away with it.

 

[just-some-guy]

Note: Too much dampening will result in the port actually reducing it's output level. I recommend 2" on most walls, reserving 4" thick for just the bottom and the back(behind driver) IF you have space. You can alternately place 4" on just one of the sides if their is not enough space behind the driver. In this case, just use 2" behind the driver. I am assuming you are using the high density rock/mineral wool (4-8lb/ft^3 range).

-Chris

i was thinking along those lines. i don't want to get carried away with it.
mineral wool, yes. idk what the # is of it, but the bundle is pretty heavy, and the stuff is pretty dense.

 

[just-some-guy]

oh. yes, i am planning acoustic room mods.

 

[just-some-guy]

ok, guys. my build is winding down, not including the tbd finish. i want to test them with my old RS meter and humble test cd. i need to know where to put the meter. and i know about the RS meter db compensations, and will apply them. thanx