PDA

View Full Version : Ways to lower tuning?



rangerboy101
08-25-2011, 04:29 PM
Any way to lower the tuning on my box? It's currently tuned to 35hz and I'd like it to be more around 30hz. Building a new box is not an option because I really don't want to spend $140 to build an identical box just to have it tuned lower. The box is just a simple slot-port designed by Buck. Thanks in advance.

groundpound4200
08-25-2011, 04:32 PM
you're going to have to make the port longer or shrink down the port area.

btw.. what do you want for the AQ in your sig?

rangerboy101
08-25-2011, 04:35 PM
you're going to have to make the port longer or shrink down the port area.

btw.. what do you want for the AQ in your sig?

I need to update my sig. I sold it already haha sorry. What part of the port do I need to make longer? I'm a newb when it comes to tuning.

surreal
08-25-2011, 04:45 PM
Per the SA15 specs they like pretty generous boxes.. Im guessing in the box you have it now there is premature rolloff which may be part of the problem.

rangerboy101
08-25-2011, 04:52 PM
There's nothing wrong with the current box. I just wanted it to be tuned a little lower.

Falcons
08-25-2011, 04:54 PM
There's nothing wrong with the current box. I just wanted it to be tuned a little lower.

dont mess with it if you like it now. its just gonna be a big pain in your ***

Nut Hair Trick
08-25-2011, 04:56 PM
If he were to add mass inside the enclosure to lower the compression area, while maintaining the same port area, wouldnt this lower box tuning?

bhsdriller
08-25-2011, 04:58 PM
yeah I think so...

take 2 boxes, one smaller then the other. With the exact same size/length port, the smaller box would be tuned lower?

mast240
08-25-2011, 05:01 PM
yes, but it would also lower his final airspace, which might screw with things... you could always extend the port out of the box a lil... would have to know exact dimensions on everything to tell you how much tho

rangerboy101
08-25-2011, 05:03 PM
So it can be done? lol

---------- Post added at 05:03 PM ---------- Previous post was at 05:02 PM ----------

I'll see if I still have the email from Buck with the pictures/deminsions of the box.

mast240
08-25-2011, 05:04 PM
i wont say a definate yes... till i see the box... but most times, yes it can

rangerboy101
08-25-2011, 05:08 PM
I just copied the email. I don't feel like opening up every picture to get dimensions.

This is a pic of the bracing:

1 dollar box designs :: tylercrim2sa-15sfrontbracing.png picture by jtbuck92 - Photobucket (http://s640.photobucket.com/albums/uu126/jtbuck92/1%20dollar%20box%20designs/?action=view&current=tylercrim2sa-15sfrontbracing.png)

bracing and port wall:

1 dollar box designs :: tylercrim1sa-15internalfront.png picture by jtbuck92 - Photobucket (http://s640.photobucket.com/albums/uu126/jtbuck92/1%20dollar%20box%20designs/?action=view&current=tylercrim1sa-15internalfront.png)

sub mounting:

1 dollar box designs :: tylercrim1sa-15submounting.png picture by jtbuck92 - Photobucket (http://s640.photobucket.com/albums/uu126/jtbuck92/1%20dollar%20box%20designs/?action=view&current=tylercrim1sa-15submounting.png)

overall:

1 dollar box designs :: tylercrim1sa-15overall3d.png picture by jtbuck92 - Photobucket (http://s640.photobucket.com/albums/uu126/jtbuck92/1%20dollar%20box%20designs/?action=view&current=tylercrim1sa-15overall3d.png)

Nut Hair Trick
08-25-2011, 05:09 PM
Yeah...
OP, if you could take some MDF, the same height internally of your enclosure, and cut them into say 3 inch strips, you can add them til you get the tune you like. To be more precise, here's an online calculator to figure out how much airspace each section will take up.... Use the bracing calculator, just leave the cutouts at 0 value. It will give you your cubic inches for the added mass... enter you info at the top so you can get an idea how it will effect your enclosure.
Enclosure Volume Calculator (EVC) (http://www.hometheatershack.com/forums/enclosure-volume-calculator/)

rangerboy101
08-25-2011, 05:10 PM
And just so everybody knows I'm not saying anything bad about Buck or his design. I just wish I would've had him design me a box with lower tuning.

supermaxx123
08-25-2011, 05:14 PM
Making the internal space less with the same length port equals higher tuning. so either inverting the sub and/or making the port longer on the outside would work

bhsdriller
08-25-2011, 05:16 PM
Making the internal space less with the same length port equals higher tuning. so either inverting the sub and/or making the port longer on the outside would work

I thought it was opposite...lowers tuning

Linkz
08-25-2011, 05:22 PM
Lower port area or extend the port outside the box. Those are the only ways to lower tuning. Reducing the area inside the box will raise tuning.

Changing the port to about 35 inches wide should give you the desired tuning.

supermaxx123
08-25-2011, 05:31 PM
If you have 2 boxes the same space, and want to do a 30hz on A and 35hz on B, box A would need to be bigger to compensate for the longer port. Hence you would need the inside bigger, not smaller.

Linkz
08-25-2011, 05:36 PM
If you have 2 boxes the same space, and want to do a 30hz on A and 35hz on B, box A would need to be bigger to compensate for the longer port. Hence you would need the inside bigger, not smaller.
You could also leave the port the same length and increase (internal) box size.

813thumper
08-25-2011, 05:57 PM
If you have 2 boxes the same space, and want to do a 30hz on A and 35hz on B, box A would need to be bigger to compensate for the longer port. Hence you would need the inside bigger, not smaller.

not true. If you have a box that is 4 cubes tuned to 30Hz and you have a box that is 4 cubes tuned to 35Hz they will have the same internal airspace but the box with the 30Hz tune would be larger overall to compensate for the port displacement.

In this case the only real option that you have without screwing everything else up is to extend the port externally.

supermaxx123
08-25-2011, 05:59 PM
If you have 2 boxes the same space, and want to do a 30hz on A and 35hz on B, box A would need to be bigger to compensate for the longer port. Hence you would need the inside bigger, not smaller.
i know

Linkz
08-25-2011, 06:07 PM
You two are saying the same thing.

akheathen
08-26-2011, 04:54 AM
lol, i ran some numbers real quick before seeing the 2nd page. got the same thing- increase the port to about 35" length, but i was just going to say- either replace the rear part of the port with a borad that is 15.5" long, instead of 7-1/2, or add another 8" to it...... but i noticed something....... you made this 4cu+ box out of 5/8" wood? and i didn't see any large panel bracing.... but i only clicked the first 2 pics...

Buck
08-26-2011, 11:17 AM
I think it's going to be difficult to lower your tuning 5 hz.

Buck
08-26-2011, 11:19 AM
Actually, now that I look at the drawing, you could shrink the port some to lower it maybe a little bit. The only way I would do that is to make the port less wide, i.e., come in from the sides and go towards the middle.

hispls
08-26-2011, 11:36 AM
Shrink the port. Cut a piece of wood (or two or three) that'll slide in snug along the outer wall of the port. You can screw it in place from the outside. Decreasing port area will lower tuning at the expense of some port area of course.

Buck
08-26-2011, 11:43 AM
I wouldn't make the port skinnier though.

infamous_e46
08-26-2011, 12:15 PM
invert the moofers

rangerboy101
08-26-2011, 05:06 PM
lol, i ran some numbers real quick before seeing the 2nd page. got the same thing- increase the port to about 35" length, but i was just going to say- either replace the rear part of the port with a borad that is 15.5" long, instead of 7-1/2, or add another 8" to it...... but i noticed something....... you made this 4cu+ box out of 5/8" wood? and i didn't see any large panel bracing.... but i only clicked the first 2 pics...

Double baffled with port bracing and baffle-port bracing.

infamous_e46
08-26-2011, 05:34 PM
invert the moofers

:fyi:

groundpound4200
08-26-2011, 05:47 PM
some bad info ITT...

Moble Enclosurs
08-27-2011, 07:43 PM
If he were to add mass inside the enclosure to lower the compression area, while maintaining the same port area, wouldnt this lower box tuning?

Only if the added mass were to slow down the sound waves. Adding mass with equal or more density than the enclosure material, would actually increase tuning.

Moble Enclosurs
08-27-2011, 07:45 PM
I thought it was opposite...lowers tuning

No. Increasing acoustical compression increases tuning, if all other variables were equal.

24v
08-30-2011, 08:21 AM
*WARNING Stupid Newb Question*
Couldn't he add some polyfill to get the desired effect? It is my understanding that adding polyfill is similar to a displacement increase. Increased displacement would lower tuning, right?

Moble Enclosurs
08-30-2011, 08:31 AM
*WARNING Stupid Newb Question*
Couldn't he add some polyfill to get the desired effect? It is my understanding that adding polyfill is similar to a displacement increase. Increased displacement would lower tuning, right?

In essence, yes, but this has a different effect on the overall sound than a properly constructed design without it. Normally, polyfill is more desired in a sealed enclosure for tuning purposes, or transmission line enclosures for LF output at the opening while dampening the HF from the rear wave for proper reproduction. In subwoofer designs other than sealed, which is based mainly on the Q factor, is not necessary for tuning. It will also, likely not do much to the tuning if the desire is to lower it by many frequencies, rather than a few(1-6Hz band).

Best bet is to properly construct a compression area and port volume for the desired frequency range, rather than tuning frequency, as the tuning frequency has minimal relationship to the entire response, unless the desired goal is SPL output alone.
I will not say do not do it though. Most of what we know today is based on trial and error.

Moble Enclosurs
08-30-2011, 08:33 AM
*WARNING Stupid Newb Question*
Couldn't he add some polyfill to get the desired effect? It is my understanding that adding polyfill is similar to a displacement increase. Increased displacement would lower tuning, right?

Think of designing enclosures this way in the idea stated in the quote:
For tuning a vehicle for speed, would you rather use a mod chip to trick the vehicle into a couple of extra horsepower, or would you rather get the turbo and hook it up correctly to get much more than a few horsepower?

hispls
08-30-2011, 08:56 AM
*WARNING Stupid Newb Question*
Couldn't he add some polyfill to get the desired effect? It is my understanding that adding polyfill is similar to a displacement increase. Increased displacement would lower tuning, right?

May work somewhat. There is some good data out there if you google the subject of stuffing boxes with polyfill. The biggest issue with stuffing a ported box in this type of scenario is stuffing firing out a big *** port into your trunk... I've tried it and it's a mess (It did change the boxes response a bit though)