Lowering tuning freq.

[qtipextra 5,000+ posts]

The box I have is actually tuned to 33hz. I would like to tune it to about 28hz. My question is, can cutting a piece of wood and adding it to the current port work? I know it will lower the tuning, but is that a good way to do it without building a new box?

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[PowerNaudio 10+ year member]

technicaly it would work.

note:any time you decrease the displacement of the enclosure your tuning rises. so calculate how much displacement is that panel that your adding taking from the enclosure volume and what the new tuning freq will be. before you make any changes.

best way to make any changes is to cut out as much of the front panel of the enclosure as you can that will increase your internal volume and add a new panel on top of that. and re cut your holes for the sub and port. that also adds to the ports length by what ever the width of the baffle you replace it with. with out taking any internal volume and it looks clean.

but yeah its posible. just make sure the port piece youre adding fits snug. use penty of glue and brad nail it or screw it from top and bottom.

 

[qtipextra 5,000+ posts]

technicaly it would work. note:any time you decrease the displacement of the enclosure your tuning rises. so calculate how much displacement is that panel that your adding taking from the enclosure volume and what the new tuning freq will be. before you make any changes.

best way to make any changes is to cut out as much of the front panel of the enclosure as you can that will increase your internal volume and add a new panel on top of that. and re cut your holes for the sub and port. that also adds to the ports length by what ever the width of the baffle you replace it with. with out taking any internal volume and it looks clean.

but yeah its posible. just make sure the port piece youre adding fits snug. use penty of glue and brad nail it or screw it from top and bottom.

Thanks for the info. I dont want to change external size at all. And adding a board would decrease the total volume to about 3.93 cubic feet net (after subs and port). I had 4.4 to start with.

 

[mazdakid 5,000+ posts]

box is going to stay the same size, you will just have a smaller port area, so its going to lower it. this is the way i do it any time i want to lower my tuning

 

[PowerNaudio 10+ year member]

box is going to stay the same size, you will just have a smaller port area, so its going to lower it. this is the way i do it any time i want to lower my tuning

that would work with a round port.

but not that simple with slot port.

unless the slotport was designed for that purpose.

 

[mazdakid 5,000+ posts]

so what are you saying

 

[mazdakid 5,000+ posts]

my port was 6.25" wide, and i put a piece of 3/4" along the inside wall of the port and now its 5.5" wide, are you saying thats not right?

 

[PowerNaudio 10+ year member]

edit: you re- posted right qick!

 

[PowerNaudio 10+ year member]

my port was 6.25" wide, and i put a piece of 3/4" along the inside wall of the port and now its 5.5" wide, are you saying thats not right?

ok thats a diffrent story. yes that will work but youll run the risk of port noise.

but yah that would work.

 

[mazdakid 5,000+ posts]

whats the reason for port noise by doing that?

 

[PowerNaudio 10+ year member]

by making the port area smaller you increase the chances of port noise. im not saying it will, since i didnt design the enclosure, but by making the port area smaller then appropiate. you increase the chances of port noise.

 

[mazdakid 5,000+ posts]

ok just making sure there wasnt something you knew that i didnt

 

[PowerNaudio 10+ year member]

okey!

 

[qtipextra 5,000+ posts]

Wow, nice hijack. thanks for that.

Anywayz, the interior net size will change, because (technically) the port size increases, so the net size of the box decreases.

EDIT: I dont want to affect port area, but I do have a little actual box volume I can play with. More port area = lower tuning = less net box volume.

EDIT #2: I didnt think of that. I was going to add to length, not decrease width. I could bring it down by adding 1" wood to the enire length.

now I have 2 options:

1) Increase length - increase port size - decrease net volume

OR

2) Decrease width - decrease port size - same net volume.

 

[mazdakid 5,000+ posts]

haha see so i didnt actually hijack, i asked questions you probably had. if the box is already at the size you wanted just try to make the area smaller, if you want the box smaller just add to the length, its going to take more than an inch to get down to 28hz