Enclosure shape

[dirtyunclerandy 10+ year member]

I am starting to throw together some ideas for my next set-up. All equipment is up in the air atm. I will be running 10's ported on around 1200rms. Most of the subs I have been looking at like 1-1.5 cubes per sub optimally. Here is my quandry.

Option 1: If I use a rectangular box, I can get around 2.68 for volume before port and sub displacement. Not sure if this is big enough.

Option 2: If I use a trapezoid box, I should be over 3 cubes. So my question is how does a trapezoid shape differ from a rectangle box? (other than shape) Has any one used this shaped box?

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[winkychevelle 10+ year member]

would the slant on the trap box be up against the back seats? if so that would work fine similar designs are used everyday. im partial to rectangle box cuze they are easy to build but if you need more airspace then the trap would work better. and depending on the tens you use u may not need much port area depending on the excursion capabilities of the sub and the actual airspace will decide how peaky the box is. smaller boxes peak worse than bigger boxes though this can be overcome with changes to the port design..

 

[Mr.meyhem 10+ year member]

also to thread jack a little, how would a box that is made of a big box in back and a smaller square extension work? like the small square would go through the opening of the trunk to the cabin and the bigger part of the box would be back in the trunk to make up the amount of volume the subs need.

 

[Mr.meyhem 10+ year member]

something like this

 

[dirtyunclerandy 10+ year member]

****, I just got jacked.

The slant would be on the sides. I have an odd shaped trunk. I am planning on a SQL setup. Subs I am considering are VVX, GCON, Lethal Injection or SA 10's. I am guessing I will have one of the gurus design it when the time comes. Just wanted to get an idea what would be best so I can plan out the amp mounting and other stuff.

 

[Mr.meyhem 10+ year member]

****, I just got jacked.
The slant would be on the sides. I have an odd shaped trunk. I am planning on a SQL setup. Subs I am considering are VVX, GCON, Lethal Injection or SA 10's. I am guessing I will have one of the gurus design it when the time comes. Just wanted to get an idea what would be best so I can plan out the amp mounting and other stuff.

didn't mean to jack thread just figured it was close to ur question. cuz I've been wondering bout box shape and stuff too. id suggest pro-rabbit.

 

[dirtyunclerandy 10+ year member]

no problem. I am hoping @pro\-rabbit,@ buck, @RAM_Designs or @Moble Enclosurs would chime in. All the people in am considering for designing it.

 

[Mr.meyhem 10+ year member]

i got a design from ram. was pretty good. I've heard great this bout pro-rabbit and buck ik pro rabbit customizes the boxes more for the sub than buck does tho. (both great designers tho)

 

[Moble Enclosurs 10+ year member]

Box shape is just as important as placement. But that does not mean the shape can cause more negative than positive. Two important things that you may or may not have heard of will effect the performance of the design........golden rule and baffle area( in relation to volume compliance).

1. Golden rule has been around since the beginning of time lol. Seriously though, looong before audio was incorporated. Many artists and engineers live by this rule due to the ability of what it can accomplish in an architectural form. And the rule has been applied to acoustics from a physics standpoint as well.

With the golden rule, there is a conformity that allows certain acoustical effects to either be allowed or ignored for the sake of proper performance. In sub design, this is for reducing what is known as standing waves, which create peaks and nulls in the response curve. The more peaks and nulls, the less desirable the output is to the listener in most cases of musical performance. So, it has been said that by utilizing the golden rule, you can achieve smoother transient responses without, or with minimalized need for, equalization beyond the physical design.

Though this is a great idea, other things have to be in play for it to become usable in subwoofer design due to the need for more room to accommodate the changes audibly noticable in LF response. All in all, it is always a good rule to conform to regardless of its intensity in effecting the curve.

2. The baffle area. Why is this important? Mainly because of placement within a limited space that can cause phase effects making the response once again, undesirable.....to a point. If you have a certain compression volume and do not feel the need to manipulate it for any reason, then making sure the baffle area is a certain area will greatly effect the phase of the design due to the same reasons that the golden rule is applied, just in a different manner. Normally, when the baffle exceeds a certain point in relation to volume of a third dimension for a non specified but also non uniformed depth or height, the chances of resonances occurring is increased, hence changing the peaks and nulls once again in the response curve.

By making the baffle a good area without causing a huge ratio difference of the third dimension, you allow the design to act more on the propagation effects rather than a pressured response for efficiency and phase correlation from the drivers original output point of source.

So, say you have a 1 cubic ft volume, you want to keep the baffle as close to a 1:1 ratio of area with the other planes as possible.

BUT, there is a catch to this......it has been said that making all planes the same area will also cause resonances. Though this is true, it is only true for certain conditions....1. That yes, it will cause resonances still, as anything within a given boundary will have, so that is not the issue. 2. The issue is that the same resonant frequencies will be excited on all planes therefore increasing the sensitivity of those specific harmonics by at least 3-12db higher than other harmonic resonances in that space. So, that is the reasoning for a volume to not be equal on all planes.

I know that is a LOT of information, but if you can get the idea, those are the main reasons for shape being important in the designing of audio enclosures. Other than that, the only other limitations are your imaginations.

Hope that helps.

 

[hispls 5,000+ posts]

^^^^^

Translated to English, if we are talking about

 

[Moble Enclosurs 10+ year member]

^^^^^
Translated to English, if we are talking about

not necessarily. When I discuss phase, it pertains to the idea of response output mentioned above. Normally, you want the passband to be within a certain degree of the driver for the port, as 180 degrees will be considered cancellation at the highest degree.

Having a baffle area that does not allow for a controlled phase will cause the biggest issue not recognized by most of the audio community....which is loss of output in the lower range (around 30hz) and naturally corrected by lowered tuning.

So, the effects of this is at any frequency range. The less sensitive of the two factors of output is based on a conventional idea. This is where pressure overrides intensity....much like that heard in round ported designs where port area is constant.

So, its not that it doesn't matter below 80Hz, its that it is design dependant ,so those that are more familiar with conventional designs, which most are, will naturally gear towards the side that is less sensitive to these changes.

 

[Moble Enclosurs 10+ year member]

Those that relate SQ with lower tuning may not have experienced a design with a near 0 phase response controlled over at least 1/2 octave of the passband, in which a higher tuning is considered more appropriate. The problem is, not many designers know how to keep the phase response within 90 degrees by using a higher tuning. Its common to rely on lower tuning for SQ results, but for the concept of correction, not perfection. Not realized is the effect of lost efficiency by lowered tuning either for SQ output.

 

[Moble Enclosurs 10+ year member]

Everybody says, "tune it to 33Hz and it will sound great for SQ", but what they really are doing is bypassing the problems......in most cases.....not all. Some designs sound much better tuned low, but it depends on the design. And if you can tune low, I don't condone it at all. Just do it for the right reasons and you will be more satisfied with the results.

Sorry for the rant.

 

[dirtyunclerandy 10+ year member]

Thats thorough. It took a few times reading it to get the gist of what you are saying, but very informative. I believe you just got yourself a client when the time comes.

 

[hondamikey 10+ year member]

WOW thats some crazy info!! I know enough about car audio to get buy and build what I though was good sounding boxes, but now reading that I might have to rethink that. Its crazy how much there really is to doing a proper car audio build.