Subwoofer Orientation.

I have two TS-W12PRS Premier subwoofers.  I would like to have the magnets exposed (Outside of the enclosure) since they are quite spectacular to look at.  Installing the subs like this is referred to as what?  Inverted?  Anyway, I heard somewhere that if you install the subs like this, you have to reverse the sub's polarity?  Please advise if this statement is accurate and if so, how do I do this?  The specs call for a sealed enclosure with the volume of 1.0 cu. ft. or 28 liters, both of +/- 10%.

I have all the parameters and specs but do not know how to use them properly.  My Subs are the DVC, 2ohm model.  I am looking to do my install in about a month from now.  I am sure I will have more questions concerning this install.  If you need more info, I will get it.  Please help.  Thanks,

Steve

Yes KETEL22, about my other question.  I guess I forgot to ask it.  It's late, I'm tired.  My Bad.

The second question should have been finding the most accurate volume for my enclosure.  Short of filling the box with water, what is the best method to find volume?  The problem is that my idea for the box is not going to have square dimensions by any stretch of the imagination.  I'm trying to add style to the box.  Picture this: A perfect cube.  12" X 12" X 12" = 1 cu ft. exactly.  Lets say I wanted to change the face of one side.  Lets say, looking at the box at eye level, the front face.  Pivot that face about its vertical center line by 15 Degrees.  Therefore elongating left side of the box while shortening the right side.  Is that box still 1 cu ft. exactly?  I am trying to explain my question as clear as possible.

Bear with me on this one.  Do the same thing to top now.  Pivot it along its dead center line by 15 degrees, whichever way you like.  As long as you respect the fact that you remain on the dead center of the wall you are pivoting, does the volume remain 1 cu. ft.?

Obviously this will be done by computer.  Namely AutoCAD.  Am I making sense here? 

im not exactly sure of what shape you are trying to achieve, maybe you could make your c.a.d drawing and import a picture in one of your posts. but i would just use the volume formula's for squares, triangles, etc.

12volt as pretty much every one you can need here,

https://www.the12volt.com/caraudio/boxcalcs.asp

just find the shapes in your box and use the formula's just adding the anwsers of all the ones you use together....

Keep in mind that all box dimensions are measured on the inside of the box.  So then a 12X12X12 box is not 1 cu ft, because the inside dimensions are reduced by the 3/4 or 1 inch thickness of the material.  Draw some basic sketches of what you want the enclosure to look like according to the space in the car you have.  They don't have to be accurate at this time.  Now,  divide that drawing into rectangles.

With a slanted side, you will have a triangle, too.  The square inches of that triangle are figured by:  1/2 base X height X width.  All the rectangles are figured as length X  height X width, with length being the same direction as base in the triangle.

Your specs call for 1 ft3, 12X 12x 12 = 1728.  Play around with your drawing dimensions until you get that.  And those will be the inside dimensions.  Once you get there...you will change it again to accomodate the woofer, or should I say, the lack of it.  Being inverted, it will not be taking up space in the box, but will also be adding space to the box (the volume inside the cone).   Draw it on your sketch for a clear view.

The allowance you have is about 10%.  The speaker displacement is somewhat less than 10% of 1 ft3, I would presume.  So you can get the dimensions close without having to worry about being true to the inch.

Thanks for all the feedback guys.  Can the woofers be installed facing a flat wall?  I've been told that they should not fire perpendicular towards a wall.  That they should be on an angle towards the facing wall.

If this is the case, I will make the floor my box.  Also, does the depth of the box matter?  Can the box be, let's say, two inches deep using the width and length to achieve the volume?  Now I'm thinking to install the subs firing downward and have the magnets sticking upward.  Raising the floor 2 inches or so will leave me with alot more trunk space.  Let me know if there are any important rules to folow when designing an enclosure. 

A rule to try to follow is the "Golden Ratio", to present the best acoustical response.  The ratio is .62 to 1.0 to 1.62.  So that if, for example you replace the 1.0 with 8", then .62 would be 5" and 1.62 would be 13".  For a box dimension of  8 X 5 X 13.  (That box is too small for anything, but just to illustrate the ratio.)

Rarely can this be possible, especially with angles.  But you see that none of the parameters are extremely small.  Angles, too, are good for the acoustics, especially the face or the back.

stevdart wrote:

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A rule to try to follow is the "Golden Ratio", to present the best acoustical response.  The ratio is .62 to 1.0 to 1.62.  So that if, for example you replace the 1.0 with 8", then .62 would be 5" and 1.62 would be 13".  For a box dimension of  8 X 5 X 13.  (That box is too small for anything, but just to illustrate the ratio.)

Rarely can this be possible, especially with angles.  But you see that none of the parameters are extremely small.  Angles, too, are good for the acoustics, especially the face or the back.

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I had heard of the "Golden Ratio" before and wondered if it was still applied to present day calculations.  I say present day because I have some old "N.A.M.E." videos on pod making and enclosure designing that mention the "Golden Ratio".

What do you mean by this paragraph below?

"Rarely can this be possible, especially with angles.  But you see that none of the parameters are extremely small.  Angles, too, are good for the acoustics, especially the face or the back."

i meant as soon as you introduce an angle, you can't achieve that absolute ratio. And that the ratio could not include a dimension as small as 2".  A word on this ratio, though:  When you're dealing with only subwoofer frequencies, the dimensions of the enclosure are not as important as that for a home system cabinet.  So people follow the rule of "how does it fit best into the car".

The angles, esp. when either on the face or the back, tend to help eliminate standing waves inside the enclosure.  I built a box for the trunk in my car with an angle on the side, and I believe that is still beneficial.

If you want to build it low and flat, consider the impact of the speaker on the face of the structure.  The box has to remain absolutely rigid.  So figure for bracing if you are going to stray that far from a "standard" box.  And build the box to fit into the car...don't consider the car floor suitable in itself as a side of the box.

You can do a google search of this site under "inverted" and pull up some previous discussions of inverted subs, with some important input from DYohn and others.

stevdart wrote:

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i meant as soon as you introduce an angle, you can't achieve that absolute ratio. And that the ratio could not include a dimension as small as 2".  A word on this ratio, though:  When you're dealing with only subwoofer frequencies, the dimensions of the enclosure are not as important as that for a home system cabinet.  So people follow the rule of "how does it fit best into the car".

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:)  I was just about to say the same thing... in general the golden ratio is critical for enclosures intended for woofers with frequency response above 180Hz or so, but for sibs can be ignored.  Air displacement volume is really the most important criteria for car audio subs.  That and speaker placement.  ALTHOUGH the golden ration would still create the best case enclosure no matter what in my opinion!

QUOTE=stevdart]

If you want to build it low and flat, consider the impact of the speaker on the face of the structure.  The box has to remain absolutely rigid.  So figure for bracing if you are going to stray that far from a "standard" box.  And build the box to fit into the car...don't consider the car floor suitable in itself as a side of the box.

[/QUOTE]

That is correct.  The floor, walls and sides would be made of wood.  Braces are a great point.  Thanks.  Are braces going to affect sound quality?  Is there a bad place to put them?  Obviously not in the woofers path.  How does their role play when calculating interior volume?  By saying I need 1 cu. ft. of air means I need 1 cu/ ft. of AIR, right.  Not simply an interior volume of "Space" inside the walls of the enclosure.

DYohn] wrote:

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:)  I was just about to say the same thing... in general the golden ratio is critical for enclosures intended for woofers with frequency response above 180Hz or so, but for sibs can be ignored.  Air displacement volume is really the most important criteria for car audio subs.  That and speaker placement.  ALTHOUGH the golden ration would still create the best case enclosure no matter what in my opinion!

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DYohn, Are you saying that it may be possible to have the enclosure, for example, 2" high and making up the remainder of the vloume through length and width?  what is your take on having the sub fire towards an angled wall? 

Yes, in theory, it doesn't matter what the geometry of a subwoofer enclosure is as long as the air volume is correct.  So yes, in theory, a 2" high enclosure could be designed.  It might not sound as good as one built closer to the golden ratio, but below, say, about 80Hz I have to believe it could perform equally well.  Go for it and see!  It's just MDF, time and money, afterall...

As far as "firing a sub toward an angled wall" it depends on the vehicle and the intent of the design.  For SPL, it probably does not matter.  For SQ, it could make a critical difference.  That's why I do not believe there are any good "rules of thimb" for loudspeaker placement that apply in ALL cases.  Every installation is different and it all depends on what the RTA tells you.

Thanks Dyohn.  One last thing before I am comfortable.  Let's say for argument I did incorporate a slight angle, opposing the woofer face, into the box, say 10 degrees.  Would this be enough to get some effect out of the angle?  I am going to try it anyway since, yes, It is only MDF.

Whats your two cents on whether or not to follow the information found in the "N.A.M.E" videos.  I think they are from the 90's.

Lastly, what is RTA?

Thanks to all for the help.