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C-Bass
10-02-2007, 03:29 AM
I'm well into my box building project. The remaining issue is the port.

I have 3.8 cuft box I want tuned to 33Hz

The online calculator stuff I've used comes up with a slot port of 6"W x 3" H x 5.22" L which seems small to me.

Can someone point me in the right direction here. I don't have a lot of room to work with either about 8" on either side of the sub

BJ The Man
10-02-2007, 05:02 PM
is it already built and your putting the port in? and what car are you putting this in and maybe some pics would help for starts.

shavenblazer
10-02-2007, 05:04 PM
I had 4 cubes with 3 4in aero ports @32hz for mine and it wannged.

C-Bass
10-02-2007, 06:43 PM
is it already built and your putting the port in? and what car are you putting this in and maybe some pics would help for starts.

The box is mostly built, I just have to get the port sorted out and fiberglass what will become the baffle.

I originally used some of the online calculators you can find to get my port area, but when I double checked with some people that are "in the know" they all said it looks too small for the woofer. That's why I'm confused. I thought a formula is a formula...

The car it's going in is a 64 Impala, but there is VERY limited room in the trunk

http://i7.photobucket.com/albums/y281/sessland/Impala/Stereo/Trunk%20Build/IMG_2462.jpg

C-Bass
10-02-2007, 06:44 PM
I had 4 cubes with 3 4in aero ports @32hz for mine and it wannged.

How long were the ports?

Immacomputer
10-02-2007, 07:00 PM
The usual way of doing these things is coming up with a design BEFORE starting to build.

It doesn't look like you have anywhere near enough room to port. It also doesn't look like you have anywhere near 4 cubes either.

C-Bass
10-02-2007, 07:36 PM
I did have a design BEFORE I started to build, using the same formulas as I have in years gone by. Everything had more than enough room as per my original design.

As I was posting a build up on another site someone mentioned they didn't think I had enough port area, but nobody has been able to say why. I didn't just pull these numbers out of the air, I used the standard formula for calculating ports like I have done in the past.

As far as it "looking" like I don't have near 4 cubes...my measurements say different. It's also in the trunk of a 64 Impala, which if you're not familiar with is HUGE....that might be a reason why it "looks" small to you

I'm by no means an expert, but just because I have 4 posts on this site doesn't mean I've never done this before.

The reason I came to ask what the deal was is I have always built my boxes the same way (with very good results) and I'm not understanding as to why I need so much more port this time around. Each time I've done this in the past, I've used the same formula.

tuck05
10-02-2007, 07:40 PM
The car it's going in is a 64 Impala, but there is VERY limited room in the trunk.....

...

DaveT
10-02-2007, 07:47 PM
...

I think he is referring to there being limited room with the batts and looks like it may have hydros or bags.;)

C-Bass
10-02-2007, 08:07 PM
It's got hydros and 6 batts in the trunk. They're currently removed for obvious reasons

Immacomputer
10-02-2007, 08:30 PM
I did have a design BEFORE I started to build, using the same formulas as I have in years gone by. Everything had more than enough room as per my original design.

As I was posting a build up on another site someone mentioned they didn't think I had enough port area, but nobody has been able to say why. I didn't just pull these numbers out of the air, I used the standard formula for calculating ports like I have done in the past.

As far as it "looking" like I don't have near 4 cubes...my measurements say different. It's also in the trunk of a 64 Impala, which if you're not familiar with is HUGE....that might be a reason why it "looks" small to you

I'm by no means an expert, but just because I have 4 posts on this site doesn't mean I've never done this before.

The reason I came to ask what the deal was is I have always built my boxes the same way (with very good results) and I'm not understanding as to why I need so much more port this time around. Each time I've done this in the past, I've used the same formula.
I don't give a **** how many posts you have and it matters not. What "formula" are you using to get port area. If you were planning on using 18in^2 of port area, you would get a lot of port noise and things would sound terrible.

What other enclosures have you built (I'm looking for size and port specs)? For what subs? With what kind of power?

You may be able to get away with a slot port heading back into that top area you have there but without dimensions, there is no way to know.

C-Bass
10-02-2007, 09:19 PM
I don't give a **** how many posts you have and it matters not. What "formula" are you using to get port area. If you were planning on using 18in^2 of port area, you would get a lot of port noise and things would sound terrible.

What other enclosures have you built (I'm looking for size and port specs)? For what subs? With what kind of power?

You may be able to get away with a slot port heading back into that top area you have there but without dimensions, there is no way to know.

If you don't know of any formulas to calculate ports I doubt you can help me.

Past enclosures have nothing to do with anything in this post...

the dimensions for the "top" part are 35.5" W x 5.5" H x 16.5" L

Immacomputer
10-02-2007, 10:07 PM
If you don't know of any formulas to calculate ports I doubt you can help me.

Past enclosures have nothing to do with anything in this post...

the dimensions for the "top" part are 35.5" W x 5.5" H x 16.5" L

I know them plenty well. I'm curious as to how you figure how much port area you should use...

What about dimensions to the other parts of the enclosure? I can possibly make a sketchup of it and see how a possible port could fit. With that sub, you're going to want about 40-50in^2 of port area.

I would actually run that sub sealed but it shouldn't sound bad in about 3.5 cubes at 32hz or so.

C-Bass
10-02-2007, 11:34 PM
ok for example...the 12volt port length calc

the formula they claim to use is ((14630000*(D/2)*(D/2))/((Fb*Fb*Vb*1728)-(1463*(D/2))))

I use 4" as the diameter simply because someone mentioned 4" aero port

box volume 3.8 cuft tuning 33 Hz Length = 5.22 inches

the bottom part of the box 34.5 x 12 x 8

the triangular middle part is 13.5 x 11 x 17.5

that's all internal dimensions also.

shavenblazer
10-02-2007, 11:36 PM
How long were the ports?

21 inches.

Immacomputer
10-03-2007, 12:39 PM
ok for example...the 12volt port length calc

the formula they claim to use is ((14630000*(D/2)*(D/2))/((Fb*Fb*Vb*1728)-(1463*(D/2))))

I use 4" as the diameter simply because someone mentioned 4" aero port


I know how to calculate port length and that's not what I was asking about. You seemed all pissed that people said the port area was too small and that you trusted your formula. Picking port area is not just something you pull out of your *** (like you did here with choosing 4" for the diameter).

The reason the 4" port or the port area that you mentioned at the top of the thread is too small is because of the horrible port noise that you will get. Around tuning, the air in the port will be excited and will be moving back and forth like the sub does. The smaller the port area is, the faster the air will be moving. If the port area is too small, the air will be moving too fast and you will get turbulence. This turbulence can be heard and it will limit the output of the sub along with add a lot of distortion to your sound.

If I can find some time at home, I will try to draw up your enclosure and find a way to fit a port in there.

You may just want to go sealed. That sub should sound **** nice in a sealed enclosure of that volume.

C-Bass
10-03-2007, 04:26 PM
I know how to calculate port length and that's not what I was asking about. You seemed all pissed that people said the port area was too small and that you trusted your formula. Picking port area is not just something you pull out of your *** (like you did here with choosing 4" for the diameter).

The reason the 4" port or the port area that you mentioned at the top of the thread is too small is because of the horrible port noise that you will get. Around tuning, the air in the port will be excited and will be moving back and forth like the sub does. The smaller the port area is, the faster the air will be moving. If the port area is too small, the air will be moving too fast and you will get turbulence. This turbulence can be heard and it will limit the output of the sub along with add a lot of distortion to your sound.

If I can find some time at home, I will try to draw up your enclosure and find a way to fit a port in there.

You may just want to go sealed. That sub should sound **** nice in a sealed enclosure of that volume.


My only concern is that when someone makes a comment like "You need more port area" and that's it, I'd like to know why.

It's been a LONG time since I played with this stuff, so I forgot most of whatever knowledge I had back then.

I did recall something about port speed and noise, but only after someone mentioned it first. As far as what to do with that info, that's another story :)

You say this sub would sound nice in a sealed box of this size. Can you explain why? The Fi website says it's not recommended.

I don't have anything against sealed boxes...and personally my way of thinking is that having a 15" sub should provide plenty of low bass (something I would normally want more of out of a smaller sub). Having it in a sealed enclosure would limit the boomy-ness and provide some more control to the sub...at least in my head

Immacomputer
10-03-2007, 10:49 PM
My only concern is that when someone makes a comment like "You need more port area" and that's it, I'd like to know why.

It's been a LONG time since I played with this stuff, so I forgot most of whatever knowledge I had back then.

I did recall something about port speed and noise, but only after someone mentioned it first. As far as what to do with that info, that's another story :)

You say this sub would sound nice in a sealed box of this size. Can you explain why? The Fi website says it's not recommended.

I don't have anything against sealed boxes...and personally my way of thinking is that having a 15" sub should provide plenty of low bass (something I would normally want more of out of a smaller sub). Having it in a sealed enclosure would limit the boomy-ness and provide some more control to the sub...at least in my head

Fi's website doesn't say it isn't recommended, they just don't have any numbers for the recommended sealed volume size. If that means they don't recommend it, I would love to hear why.

If I was looking for a 15" sub for a sealed enclosure, the SSD would be one of the first subs I would consider. When sealed, the sub will have a nice low F3 around 35hz or so and it would still sound pretty tight as it's alignment would be around .8 Qtc. It has a mid Qts value, low Fs, medium Vas, high Qes, and a decent amount of throw which just screams "seal me" to me. It should dig pretty **** low sealed and should still have decent authority up top with all around decent SPL.

It would probably be your best route unless somebody else can figure out how to get a port into that. I failed at making one easy to do.

C-Bass
10-04-2007, 01:48 AM
Fi's website doesn't say it isn't recommended, they just don't have any numbers for the recommended sealed volume size. If that means they don't recommend it, I would love to hear why.

If I was looking for a 15" sub for a sealed enclosure, the SSD would be one of the first subs I would consider. When sealed, the sub will have a nice low F3 around 35hz or so and it would still sound pretty tight as it's alignment would be around .8 Qtc. It has a mid Qts value, low Fs, medium Vas, high Qes, and a decent amount of throw which just screams "seal me" to me. It should dig pretty **** low sealed and should still have decent authority up top with all around decent SPL.

It would probably be your best route unless somebody else can figure out how to get a port into that. I failed at making one easy to do.

They mention it on the official Fi forums

but...

After doing way more research than I had hoped regarding this topic, I agree with you 100% There doesn't seem to be any reason why not

and it would also get me out of this situation

I would have definitely designed the box differently had I taken into account the port sq.in. etc,. I thought I was going to get away with the little ports in my first calculations..heh

If anybody is interested I can update this thread with the building progress

Immacomputer
10-04-2007, 11:41 AM
Keep us updated.

I would love to know why Scott would not recommend this sub sealed. Maybe it's because it needs a good size sealed box to perform well? That would be a pretty ****** reason to not recommend it.

C-Bass
10-04-2007, 12:26 PM
I don't know why either...

Thanks for all your help btw, appreciate you steering me in the right direction.