Problems with Ported Enclosure for 12'' Fi X

[imhungnurnot 9]

So I designed and built my first ported box on my own, and it does not sound like i anticipated. I believe you all can help.

The box is for a single 12'' Fi X with 1.6 cuft @ 31.00 Hz. The sub has a 0.1 cuft displacement, and the Fs is 25.7 Hz. I was told to tune a little higher than the Fs.

The O.D. of the box is 16 x 14.75 x 21.625

The port is 8 x 2.25 x 27.875. I used WinISD to design the port. I used 11.25 sqft of port area.

I was hoping for it to be musical and be able to go from high freq. to low freq. without problems, but it bottoms out easily on the lows and makes mechanical noise on the highs even with my active cross over set to 35 Hz with a 18 DB slope.

I was thinking that i may have too much port area because it seems like the speaker does not have enough back pressure to control its movement.

What do you all think?

[rushnrun 14]

what amp are you running?

got pics?

is it a slot port?

[imhungnurnot 9]

what amp are you running?

got pics?

is it a slot port?

Autotek MM1000.1D. This box was a test to see if I am capable of porting.

http://by113w.bay113.mail.live.com/att/GetAttachment.aspx?tnail=0&messageId=566bebd0-bc43-4d5e-a8d8-71d1c775e0c9&Aux=0|0|8CBEA5BAB595A90|

http://by113w.bay113.mail.live.com/att/GetAttachment.aspx?tnail=0&messageId=de4befed-b21f-4159-99d5-3afcb8dd95a3&Aux=0|0|8CBEA5BB8E38A50|

[Duran 387]

what amp are you running?

got pics?

is it a slot port?

Autotek MM1000.1D. This box was a test to see if I am capable of porting.

http://by113w.bay113...CBEA5BAB595A90|

http://by113w.bay113...CBEA5BB8E38A50|

A link to your email won't do anything for us. When I click on your link it opens up MY email.

[rushnrun 14]

X2

[imhungnurnot 9]

[Kanaworm$ 292]

General rule of enclosures is 12-16 square inches of port per cubic feet of air space. Looks like you don't have enough port.

[Notorious97200 339]

1.6 ft3 at 31Hz ?

That looks small! (for my taste!!!).

[shizzzon 461]

i dont know anything about the requirements for the sub but this is what i do know-

most 12s are recommended to be in 2cuft NET

You need at least 25sq of port, recommended at least 32sqin, not 18sqin.

When building a port, try to use the whole height of the box for the slot port.

The way you built it is just taking up unnecessary room in the box due to the thickness of the wood.

Also, when using a port that shares the box wall, the beginning of the port from the inside of the box will have an acoustical extended length to it.

Average calculations would say that the width of the slot port would have an acoustical length 0.5x that of the width.

Example-

If you had a 14.5" high x 3" wide port, the acoustical extended length would be 1.5" and this would need to be subtracted from required port length to obtain desired tuning frequency.

Also, if building port completely in the box, if the port uses the baffle as part of it's length, do not forget to account for this as well.

[imhungnurnot 9]

The reason it is small is because I have a limited amount of room in my truck. Is there any way to design a compact ported enclosure for a 12 to be louder than a sealed box in the lower freq range? That was my aim because i am disappointed with the low end sound and loudness of my 12's in their sealed enclosures.

[shizzzon 461]

if there is any way to make the box larger, give me the maximum dimensions

[imhungnurnot 9]

if there is any way to make the box larger, give me the maximum dimensions

5.5 x 9.5 x 16 x 56 O.D. wedge box with 5.5 and 9.5 being the different depths using 3/4 inch wood for one 12inch sub

[shizzzon 461]

can u show me a picture of your existing one?

I dont understand how u can only have 1 depth of 5.5 and another of 9.5 when ur existing one is 14.75...

[Kanaworm$ 292]

You have a net of 2.744 cubic feet before port and speaker displacement.

Edited August 13, 2009 by OldSkool_08

[KU40 173]

I'm not sure where you learned math, but an 8 x 2.25" port does not give you 11.25 square inches of port. It gives you 18 square inches. But that is not too much port area.

Factoring in 3/4" wood, your box is about 2.2 cubes gross. Take out .1 cube for the sub and about .42 for the port and you have a net of 1.68. Plug this into winISD and your tuning frequency is a little over 30 hz. So you're still ok there.

What crossovers do you have on the sub, and where are they set? Are you using any bass boost either in the head unit or amplifier?

[imhungnurnot 9]

I'm not sure where you learned math, but an 8 x 2.25" port does not give you 11.25 square inches of port. It gives you 18 square inches. But that is not too much port area.

Factoring in 3/4" wood, your box is about 2.2 cubes gross. Take out .1 cube for the sub and about .42 for the port and you have a net of 1.68. Plug this into winISD and your tuning frequency is a little over 30 hz. So you're still ok there.

What crossovers do you have on the sub, and where are they set? Are you using any bass boost either in the head unit or amplifier?

11.25 of port area per cubic foot of volume.. sorry for the type-o..

the crossover on the amp doesn't really matter much because i have the one on head unit set to 35 Hz with a 18 db slope. No bass boost on the amp.. but I guess i use a booster on the head unit on like 4.. the scale is 0-15

[imhungnurnot 9]

can u show me a picture of your existing one?

I dont understand how u can only have 1 depth of 5.5 and another of 9.5 when ur existing one is 14.75...

the box i built wasn't designed to fit in the truck.. it was to test if i could build a compact box and make it sound good with good output.

[rushnrun 14]

well your LPF should be set much higher than 35.... I don't know of any decks that have a 35hz lpf though... should be set around 60-80hz or whatever blends with the frontstage..

[imhungnurnot 9]

well your LPF should be set much higher than 35.... I don't know of any decks that have a 35hz lpf though... should be set around 60-80hz or whatever blends with the frontstage..

i have it set to 40 with the speakers sealed.. they go crazy with the high frequency and don't pick up the lows as easily.. so i set the crossover low to compensate for that.. because they make mechanical noise when i send too much high freq to them.. and it doesn't blend cause my front stage sucks.. 4x6's need to be discontinued.. lol.. but they would def blend if i had a pair of 6.5's on that active crossover..

[KU40 173]

Exactly what kind of crossover is your head unit putting to the subwoofer amplifier? High pass or low pass? Either way, 35 hz doesn't work. You need a low pass around 80 and a highpass (subsonic) around 25.

[imhungnurnot 9]

Exactly what kind of crossover is your head unit putting to the subwoofer amplifier? High pass or low pass? Either way, 35 hz doesn't work. You need a low pass around 80 and a highpass (subsonic) around 25.

it works perfectly fine.. for some reason it'll play way higher than 40 Hz.. LPF.. Apline CDA-9855

[///M5 2,833]

Exactly what kind of crossover is your head unit putting to the subwoofer amplifier? High pass or low pass? Either way, 35 hz doesn't work. You need a low pass around 80 and a highpass (subsonic) around 25.

it works perfectly fine.. for some reason it'll play way higher than 40 Hz.. LPF.. Apline CDA-9855

what slope, if it is only a 6db then of course it will

[imhungnurnot 9]

Exactly what kind of crossover is your head unit putting to the subwoofer amplifier? High pass or low pass? Either way, 35 hz doesn't work. You need a low pass around 80 and a highpass (subsonic) around 25.

it works perfectly fine.. for some reason it'll play way higher than 40 Hz.. LPF.. Apline CDA-9855

what slope, if it is only a 6db then of course it will

either 18 or 12.. but i believe its 18.. i'll check tom

[KU40 173]

Exactly what kind of crossover is your head unit putting to the subwoofer amplifier? High pass or low pass? Either way, 35 hz doesn't work. You need a low pass around 80 and a highpass (subsonic) around 25.

it works perfectly fine.. for some reason it'll play way higher than 40 Hz.. LPF.. Apline CDA-9855

what slope, if it is only a 6db then of course it will

18 db.

Let me guess, you have the lowpass at 35 but in order to get decent bass you have to turn the gain on the amp all the way up? Then it makes it bottom out easily but not play the high stuff because of the low pass filter. Are you sure it's making mechanical noise on the highs? Mechanical noise comes from the cone moving a decent amount, and I can't see the cone moving hardly at all on the higher bass notes when your lowpass is at 35.

Try this out- turn the crossover off on the head unit. Turn the lowpass xover on the amp to 80 hz. Reset the gain.

[imhungnurnot 9]

18 db.

Let me guess, you have the lowpass at 35 but in order to get decent bass you have to turn the gain on the amp all the way up? Then it makes it bottom out easily but not play the high stuff because of the low pass filter. Are you sure it's making mechanical noise on the highs? Mechanical noise comes from the cone moving a decent amount, and I can't see the cone moving hardly at all on the higher bass notes when your lowpass is at 35.

Try this out- turn the crossover off on the head unit. Turn the lowpass xover on the amp to 80 hz. Reset the gain.

In the ported box it makes mechanical noise with the high stuff but not so much sealed box.. But that is exactly what i did and it sounds way better than it did before because it sounded like shit with the LPF at 60.. Like the subs were getting really loud and bottoming on the high end but barely playing the lower notes.. so i cut the highs with the LPF and cranked the gain..

I'll try what you told me and see how you works.. but i think its something with the subs.. like they take less power to get loud on the high freq than the lower freqs.