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,
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,
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.
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.
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,
"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,
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?
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?
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,
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,
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,
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,
Vaughan said:
Probably you must start from other perspective to understand.
Imagine a speaker freely suspended, that is, no box or baffle whatsoever. In this case, you have a pressure wave created by the front of the moving cone, but also a smaller presure wave from behind going in the opposite direction. The front pushes air while the back is pulling, and this pulling leaks arround the driver and substracts from the front component.
To solve this, now we place a perfect wall with a single hole for driver mount. This is known also as an infinite baffle. By blocking completely the presure wave generated by the cone's back, we have the best possible efficiency. This arrangement is used sometimes when conditions allow.
Second best is to replace the infinite baffle with a box, the idea is to trap and dissipate the rear wave as best as possible. But now having a closed box behind, every attempt to move the cone either way will result in varying the box's inner volume, which by way of Boyle's law implies a reciprocal change in pressure. Any attempt to move the cone will thus find an elastic reaction attempting to restore it to the resting position. The larger the box, the lower the elastic reaction being it null in the limiting case wher the volume is infinite like the previous example of an infinite baffle.
Bass reflex tuning and other variations address other frequency response issues, but I hope this helps to get the basic concepts.
With respect to low frequency extension, note that to attain a given sound pressure, the cone displacement must be proportionally larger for lower frequencies. Remembering the enclosure trapped air resists cone movement, much more so the larger the attempted movement, it is clear the lower frequencies are the ones to benefite more from a larger box volume.
Hope this helps.
Rodolfo
Hi Vaughan
Whilst I appreciate and understand your thirst for knowledge, there is a contradiction in what you say. To understand properly what is going on, you need to have a certain level of skill with formuli and mathematics. Examples like the one I gave you above are not the truth, just a way of simplifing things. To design speakers, you don't really need to understand the Gas Laws, just know that certain equations come out of them that you can use. I suggest that before you do anything else you get a few physics textbooks from the library, especially ones dealing with mechanics, and see if you can give yourself a basic grounding in the way things move and react. I would love to have the time to give you what probably equates to an undergraduate level knowledge of physics, but sorry, I don't. But good luck in your studies!
Whilst I appreciate and understand your thirst for knowledge, there is a contradiction in what you say. To understand properly what is going on, you need to have a certain level of skill with formuli and mathematics. Examples like the one I gave you above are not the truth, just a way of simplifing things. To design speakers, you don't really need to understand the Gas Laws, just know that certain equations come out of them that you can use. I suggest that before you do anything else you get a few physics textbooks from the library, especially ones dealing with mechanics, and see if you can give yourself a basic grounding in the way things move and react. I would love to have the time to give you what probably equates to an undergraduate level knowledge of physics, but sorry, I don't. But good luck in your studies!
Ingrast, thanks for the explanation. BTW, how did you come to understand this ?
Do you have some books that you could recommend that go into heavy theory without bringing up complex equations ? As I said, I am not a math guy, and I don't want to wade through formula's that I can't understand.
There must be better ways to understand this. The theory behind it will work for me because I can understand that. Any books on theory ?
--Sincerely,
Do you have some books that you could recommend that go into heavy theory without bringing up complex equations ? As I said, I am not a math guy, and I don't want to wade through formula's that I can't understand.
There must be better ways to understand this. The theory behind it will work for me because I can understand that. Any books on theory ?
--Sincerely,
Vaughan said:
It happens I am an engineer ...
I do not have recomendations, but I guess the ones cited above are provided by reliable contributors.
Please understand maths is an inescapable tool to understand in depth what goes on in the physical realm. I am afraid there is a certain point beyond which verbal description no matter how carefully worded simply cannot replace physics modelling by maths.
Rodolfo
Vaughan,
Boyle's law won't help you here. Just think of the air inside the enclosure as a spring... the more air (bigger box) the softer the spring.
The woofer has to work against the spring... so the softer the spring, the more the woofer will move.
Now, you tripped on one thing... more EFFICIENT does not mean DEEPER.
Buy the beginner speaker books and do the math. The good books make the math easy. When it comes to science and engineering you will never find math & theory separated.
Boyle's law won't help you here. Just think of the air inside the enclosure as a spring... the more air (bigger box) the softer the spring.
The woofer has to work against the spring... so the softer the spring, the more the woofer will move.
Now, you tripped on one thing... more EFFICIENT does not mean DEEPER.
Buy the beginner speaker books and do the math. The good books make the math easy. When it comes to science and engineering you will never find math & theory separated.
Now I am even more confused. I thought that more efficiency would mean deeper bass because the driver is less restricted and can move more air.
I am not doubting your knowledge but I am getting conflicting opinions here. Do you know Jack Gilvey ? He posts on Home Theater Forum. I asked him the same question and his response was :
" More deep bass efficiency means deeper bass, since there will be more output down low for a given power input...hence a flatter FR with a lower F3 in general. Deep bass requires larger excursions, which would compress the airspring more, so the deep bass would be most affected by an increase in Vb/decreased resistance. Less resistance to the excursions means that it takes less work for the amp to move the driver...which defines efficiency. A larger box has less affect on the upper bass, that's why you don't get an even increase in efficiency across the spectrum. There's a limit, of course, a point at which the driver is no longer limited by the box but by its own characteristics/rolloff (as in IB)."
Do you agree with that ?
--Sincerely,
I am not doubting your knowledge but I am getting conflicting opinions here. Do you know Jack Gilvey ? He posts on Home Theater Forum. I asked him the same question and his response was :
" More deep bass efficiency means deeper bass, since there will be more output down low for a given power input...hence a flatter FR with a lower F3 in general. Deep bass requires larger excursions, which would compress the airspring more, so the deep bass would be most affected by an increase in Vb/decreased resistance. Less resistance to the excursions means that it takes less work for the amp to move the driver...which defines efficiency. A larger box has less affect on the upper bass, that's why you don't get an even increase in efficiency across the spectrum. There's a limit, of course, a point at which the driver is no longer limited by the box but by its own characteristics/rolloff (as in IB)."
Do you agree with that ?
--Sincerely,
There are no conflicts hear... his first sentence could have been worded a little better.
Efficiency blankets the frequency spectrum... so more effriciency means more deep bass, more mid bass, more everything... so the deep doesn't seem deep because everything else got louder too.
When you say you want "deep bass" you are really saying that want flat response down to 20 Hz or so. Like a guitar string, or blowing over a soda bottle, a speaker has a resonant frequency. It sings louder at this note then any other.
You can hear this frequency, somewhat, if you tap on the speaker cone. The problem this frequency is usually where you don't want it... too high in frequency thus masking or overwhelming the deep stuff.
To get deep bass you either have to supress the speaker's tendency to sing too loud at this frequency... so you can hear the deep bass instead of everything alse. This means killing some of the efficiency... usually.
Or you must shift the resonant frequency down into the deep bass range. That usually means a different speaker.
In all cases, the box, and it's ports, or horns etc... all link mechanically with speaker. In the end you have new system that is a combination of all things.
Two very... very... general rules:
"Tight bass" with "deep" response usually comes from sealed boxes because the consistent spring behavior of the air donimates the speakers tendency to sing too loud at its resonant frequency. Now, what you pay for this is efficiency. But this is how you can realize some of these little bookshelf speakers with big bottom ends.
"Efficient bass" usually comes from boxes that are: large, ported, or tuned. The large boxes allow the cone to move easier, but the speaker starts to resonate more. Ported boxes allow for a smaller box because they fool the speaker into thinking it's in a bigger box (there are many other tricks with ports)... at least at certain frequencies. The ports are "tuned" to help squash down the resonance.
Now there are some very efficient designs that get deep bass. A large driver, with a weighted (heavy) cone, loose suspension, in a carefully ported box. These can tend to sound "loose" though because the speaker tends to keep moving even when the amp says no.
Everything is in conflict... and everything must be comprimised... welcome to engineering!
And I ain't no speaker guru... I've built speakers... got great results... but I used the books and the "numbers". Trust me, I are an engineer and no one hates numbers more than an engineer.
You need da books man!
Efficiency blankets the frequency spectrum... so more effriciency means more deep bass, more mid bass, more everything... so the deep doesn't seem deep because everything else got louder too.
When you say you want "deep bass" you are really saying that want flat response down to 20 Hz or so. Like a guitar string, or blowing over a soda bottle, a speaker has a resonant frequency. It sings louder at this note then any other.
You can hear this frequency, somewhat, if you tap on the speaker cone. The problem this frequency is usually where you don't want it... too high in frequency thus masking or overwhelming the deep stuff.
To get deep bass you either have to supress the speaker's tendency to sing too loud at this frequency... so you can hear the deep bass instead of everything alse. This means killing some of the efficiency... usually.
Or you must shift the resonant frequency down into the deep bass range. That usually means a different speaker.
In all cases, the box, and it's ports, or horns etc... all link mechanically with speaker. In the end you have new system that is a combination of all things.
Two very... very... general rules:
"Tight bass" with "deep" response usually comes from sealed boxes because the consistent spring behavior of the air donimates the speakers tendency to sing too loud at its resonant frequency. Now, what you pay for this is efficiency. But this is how you can realize some of these little bookshelf speakers with big bottom ends.
"Efficient bass" usually comes from boxes that are: large, ported, or tuned. The large boxes allow the cone to move easier, but the speaker starts to resonate more. Ported boxes allow for a smaller box because they fool the speaker into thinking it's in a bigger box (there are many other tricks with ports)... at least at certain frequencies. The ports are "tuned" to help squash down the resonance.
Now there are some very efficient designs that get deep bass. A large driver, with a weighted (heavy) cone, loose suspension, in a carefully ported box. These can tend to sound "loose" though because the speaker tends to keep moving even when the amp says no.
Everything is in conflict... and everything must be comprimised... welcome to engineering!
And I ain't no speaker guru... I've built speakers... got great results... but I used the books and the "numbers". Trust me, I are an engineer and no one hates numbers more than an engineer.
You need da books man!
So a bigger enclosure will be more efficient in the deep bass. But it won't necessarily be more efficient in the higher bass ranges ?
Ported enclosures, as I understand it, are two resonating systems. One the active driver and the port. So the enclosure is emitting two sound waves as opposed to one in a sealed enclosure (all things being equal ). The port is redirecting the back wave energy (or back pressure ) of the driver through the port while sealed subwoofers waste half of their radiated energy because it's trapped.
Am I correct so far ? And as I understand it, in ported design, the drivers work relatively hard above the tuning point until gradually when the response nears tuning, the port takes over and the drivers excursion is small. More headroom less distortion. Correct ?
I'm not totally clueless. At least I don't think so. Heh. The 24dB per actave drop, is that because the driver and port go out of phase below tuning ? Why is that ?
And why do ported subwoofers have a lower -3dB point all things being equal to sealed designs ?
--Sincerely,
Ported enclosures, as I understand it, are two resonating systems. One the active driver and the port. So the enclosure is emitting two sound waves as opposed to one in a sealed enclosure (all things being equal ). The port is redirecting the back wave energy (or back pressure ) of the driver through the port while sealed subwoofers waste half of their radiated energy because it's trapped.
Am I correct so far ? And as I understand it, in ported design, the drivers work relatively hard above the tuning point until gradually when the response nears tuning, the port takes over and the drivers excursion is small. More headroom less distortion. Correct ?
I'm not totally clueless. At least I don't think so. Heh.
The 24dB per actave drop, is that because the driver and port go out of phase below tuning ? Why is that ? And why do ported subwoofers have a lower -3dB point all things being equal to sealed designs ?
--Sincerely,
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