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Old 29th January 2006, 11:47 PM   #1
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Default Some interesting questions

Hi guys,

I would like to learn more about subwoofer theory and I need as much information as I can get. I have some questions that I would really like answered and I would appreciate the help.

1. I need to know: why do bigger enclosures give deeper bass ? I need to know the theory behind this. What exactly is it about bigger enclosures that makes for deeper bass ? Is it more air in the enclosure ? I don't know. Some in depth theory would be appreciated.

2. I need to know about the back wave in the cabinet. How does this affect driver performance. How does pressure in the cabinet affect the driver ? Again, the theory behind this would be appreciated.

3. I would really appreciate it if you guys could recommend me to some articles that would expound on these issues as well. Excellent books on theory would be appreciated as well.

I need to know how these things work. It isn't good enough for me to know the answers but I need to know the "how" behind the answers. Thank you very much.

--Sincerely,
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Old 30th January 2006, 12:12 AM   #2
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there are a few books that are pretty good at explaining the knows and hows of loudspeakers.

for getting the basics down and then some.

you can't go wrong with:

"Designing, Building, and testing your own speaker system"
by David B. Weems

and if that gets you going enough then

"The loudspeaker design cookbook" is regarded by many as one of the best out there for technical know how and theory.

that book was written by Vance Dickason.

Check them out i'm sure you wont be disapointed.
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Old 30th January 2006, 11:07 AM   #3
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Thank you for the recommendations. I also read through Hoffmans Iron Law which gives me answers but doesn't explain anything.

"Hoffman's Iron Law states that the efficiency of a woofer system is directly proportional to its cabinet volume and the cube of its cutoff frequency (the lowest frequency it can usefully reproduce). "

But why is this ? What is it about the bigger enclosure that gives deeper bass ? Is it the increased air pressure ? I don't know and no one I have spoken to even attempted to answer this for me.

I really need to know. It's like sooo frustrating when you don't understand the reason behind the answers.

--Sincerely,
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Old 30th January 2006, 11:18 AM   #4
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Basic explanation.

The air in an enclosed box has a compliance. Think of this as "springyness". A bigger box with more air is less springy, allow the cone to move slower, therefore produce lower bass.

Think of a ruler, held over the side of a table top. The natural elasticity of the ruler is the same all the way through, much like the air in a box. If you want to produce low frequencies when you flick the end of the ruler, you need to have a lot of the ruler sticking over the edge of the table. As the amount of ruler over the side of the table gets less, (i.e. the box gets smaller), the frequency of the "sproing" noise gets higher.

Does that help?
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Old 30th January 2006, 11:44 AM   #5
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Pink mouse, how does a bigger box with more air allow the cone to move slower, therefore to produce lower bass ?

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Old 30th January 2006, 11:50 AM   #6
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Because there is more air enclosed, so it is more easily compressed by the slow movements of the cone needed for bass reproduction.

It's exactly the same principle as the ruler experiment above.
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Old 30th January 2006, 11:51 AM   #7
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Are there any articles on the web I can read that go into this in more detail ?

--Sincerely,
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Old 30th January 2006, 12:01 PM   #8
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How heavy do you like your maths?

http://www.silcom.com/~aludwig/Sysde...l_analysis.htm
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Old 31st January 2006, 06:57 PM   #9
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To be honest, I am not a "math" guy. But I am into "theory".

Could you recommend some articles I could read that go into detail on the theory of how enclosures affect driver performance, how bigger enclosures allow deeper bass, and the effects of the back pressure in the cabinet ?

Please correct me if I'm wrong here. If I understand this properly, the air in an enclosure acts like resistance. The more resistance, the more power required to overcome this resistance which is why sealed designs are inefficient compared to ported design because sealed designs need to overcome the internal air pressure in the cabinet to compensate.

Am I correct so far ?

And bigger enclosures have less resistance than smaller enclosures which means better efficiency. Better efficiency means deeper bass ?

This is what I'm struggling to understand. The causal relationship between bigger cabinets and deeper bass. I don't understand why a bigger enclosure necessarily means deeper bass. I know you explained in your example but I'm still not following.

Sorry for being such a pain here.

I need to know what happens to a driver as the cabinet increases, or, moreover, what happens to the cabinet as it is increased. This is what I need to understand.

Another analogy would be appreciated (or two ). I also just want to say thank you for trying to make me understand these things. Any help I get is greatly appreciated.

--Sincerely,
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Old 31st January 2006, 07:00 PM   #10
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Also, I just wanted to know. The Vance Dickason book on loudspeaker design. Is that part math and part theory ? How much is theory and how much is math ? Because I need to read books that are heavy in theory.

If there are some recommendations on this I also would appreciate it. I just don't want to purchase a book and find out that there are tons of equations and theorems that I have no clue of. Thanks in advance.

--Sincerely,
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