Subwoofer enclosure size doesn't matter much *pics*

[glen]

Thanks to Sid59 for hosting.

This was made with the free program called WinISD Pro (Alpha version)

The drivers specs are from http://www.adireaudio.com
for the Shiva MarkIII. You have to add this driver's T/S parameters in as the program only has the Shiva 1 and 2 already loaded in the data.

Orange is 2.26 cubic feet
Blue is 1.5 cubic feet
Yellow is 1.2 cubic feet
http://pages.sbcglobal.net/sid_rocks/atot/plot3.PNG


Also, remember this does not show the whole picture. It assumes an enclosure on one side of the driver, and infinate space on the other side. In your car, the box is on one side of the driver, and the cabin space of you car is on the other.

 

[Heisenberg]

Pretty lines but what the hell do they mean?

 

[glen]

Originally posted by: Heisenberg
Pretty lines but what the hell do they mean?

They show how the frequency response of the speaker changes as the space on one side of the driver changes size.

 

[Lithium381]

i heard that that sub loves 3cuft enclosures

personally my sub for an 8" pioneer(cheap) is a vented 1/2 cubic ft vented, i could easily do a lot better, but with my budget, both time and money, this worked out great

 

[glen]

Originally posted by: Lithium381
i heard that that sub loves 3cuft enclosures

personally my sub for an 8" pioneer(cheap) is a vented 1/2 cubic ft vented, i could easily do a lot better, but with my budget, both time and money, this worked out great

I am trying to show that these so called, "ideal enclosure" sizes are over rated and don't make much difference.
My point is that it doesn't love 3cubic feet.

 

[LS20]

is that scale on the left dB? and if so, below 50hz--where subs are suppposed to play--isnt there a large difference between the deviation is as much as 3db... which equals to twice as powerful ?

 

[glen]

Originally posted by: LS20
is that scale on the left dB? and if so, below 50hz--where subs are suppposed to play--isnt there a large difference between the deviation is as much as 3db... which equals to twice as powerful ?

Great point, and in some posts I say size doesn't matter, yet in others I swear by infinate baffle.
In the graph, the difference between the yellow(1.2 cuft) and blue(1.5) in the octave from 10hz to 20hz is about 2db, which is not much, barely audible. That si the size of the box in question that started me on this. But, you are right, size does make a difference once we start getting to some really large enclosures, which is why I always say use an infinate baffle. An infinate baffle starts from 4 to 10 times the VAS and runs to infinate volume. For the Shiva Mark III, VAS is 151 litres, hold for convertion to cubic feet... 5.3 cubic feet, so 4 times that is 20 cubic feet which is your average trunk size.

 

[glen]

for the mornign crowd

 

[Howard]

Originally posted by: glen
for the mornign crowd

Is there a technical explanation why there's a mini-rise in output @ ~55Hz for the yellow and blue lines?

 

[ElFenix]

my oem stuff uses infinite baffle... deck mounted woofer

 

[dman]

What's infinite baffle style vs Sealed? Is that where there's lots of that special acoustic foam inside?

The vented enclosures are the ones that get me, you can 'tune' them to sound best at certain frequencies by the volume and by the length of the vent. I never understood the best way to design those.

 

[Lithium381]

Originally posted by: glen

Originally posted by: Lithium381
i heard that that sub loves 3cuft enclosures

personally my sub for an 8" pioneer(cheap) is a vented 1/2 cubic ft vented, i could easily do a lot better, but with my budget, both time and money, this worked out great

I am trying to show that these so called, "ideal enclosure" sizes are over rated and don't make much difference.
My point is that it doesn't love 3cubic feet.

yes, they may be over rated for just a 2db boost, but if you're making a sub, you want to get peak preformance, at the cost of about .5ft, it'd be worth it, and that's what it's there for, you can settle for less, but if you're going to do it, might as well go all out

 

[Mrburns2007]

At 20 hz there's 4 db difference and 3 db is equal to doubling the power so i would say that it is worth it to build the bigger box.

 

[Viperoni]

glen, whatever happened to transient response/group delay and excursion/power handling?

Furthermore, WinISD doesn't model under power where the frequency response change DRASTICALLY. You'd crap your pants if you saw the actual frequency response for the Shiva in the 1.2cf sealed box at anything more than 150watts.

 

[glen]

Originally posted by: Viperoni
glen, whatever happened to transient response/group delay and excursion/power handling?

Furthermore, WinISD doesn't model under power where the frequency response change DRASTICALLY. You'd crap your pants if you saw the actual frequency response for the Shiva in the 1.2cf sealed box at anything more than 150watts.

WinISD pro does measure freque3ncy under power.
Well, Nousaine says you can't really hear changes in transient response much, what matters in subs is the frequency response.
I always say go with an IB, which has the best transient response.
And, the original thread was talking about the difference between a 1.2 and 1.5 cuft sealed box, which is very very little.
In addition, none of the graphs are correct because they do not take into account the enclosure infront of the driver, the car's interior.
WinISD pro will add this feature in later editions, but how we are going to measure the interior volume of our cars in beyond me.

 

[Viperoni]

Originally posted by: glen

Originally posted by: Viperoni
glen, whatever happened to transient response/group delay and excursion/power handling?

Furthermore, WinISD doesn't model under power where the frequency response change DRASTICALLY. You'd crap your pants if you saw the actual frequency response for the Shiva in the 1.2cf sealed box at anything more than 150watts.

WinISD pro does measure freque3ncy under power.
Well, Nousaine says you can't really hear changes in transient response much, what matters in subs is the frequency response.
I always say go with an IB, which has the best transient response.
And, the original thread was talking about the difference between a 1.2 and 1.5 cuft sealed box, which is very very little.
In addition, none of the graphs are correct because they do not take into account the enclosure infront of the driver, the car's interior.
WinISD pro will add this feature in later editions, but how we are going to measure the interior volume of our cars in beyond me.

But it doesn't model for non-linearities which only occur when you model at power with a true program like LEAP, LSPCad, Speak Easy, etc. Also the sub has to be measured with calibrated equipment using a program such as LEAP or MLS.
WinISD, though somewhat useful, is practically useless at any sort of typical subwoofer power level.

Take for instance the 12inch Dayton Titanic MK2...
These are LEAP models of it at 350watts. Notice the big hump between the 2 smallest box sizes.

Link's help
http://members.rogers.com/viperoni/RUDYSEAL.jpg

IB's nice if you're into that type of bass response, unfortunately most people, myself included, prefer a nice midbass bump
I'm of the opinion that you can hear differences in group delay easily: I'd have no problem spotting a Shiva in 2cf EQ'd to sound like a Shiva actually in 1cf due to the group delay difference. I suspect almost everybody else could.

The volume of the car itself is not so big of a concern as the actual frequency response is... after all, you could have a small leaky car (like my Topaz), or a big well sealed one (such as your BMW )