I need a lesson on the importance (or not) of the L-W-H dimensions of a sealed enclosure.
I've read in the past about the "golden ratio" but I've seen box enclosures that are "all over the place" since the 1970's
It seems that the more recent boxes have the depth longer than the width.
In the past, I've seen the opposite.
I'm sure it may be a function of the driver parameters? BUT generally what should you shoot for? (and why? -- please teach me).
After all, air is moved with more force from the front and back so in a sealed enclosure it would seem that making the depth longer would make sense.
I'm interested at the moment in building a simple system using the Pioneer B20 full range in a sealed enclosure and I again see dimensions (width and depth) that are inconsistent.
One plan calls for a 10" wide, 6" deep, 40" high?
THANKS.
I've read in the past about the "golden ratio" but I've seen box enclosures that are "all over the place" since the 1970's
It seems that the more recent boxes have the depth longer than the width.
In the past, I've seen the opposite.
I'm sure it may be a function of the driver parameters? BUT generally what should you shoot for? (and why? -- please teach me).
After all, air is moved with more force from the front and back so in a sealed enclosure it would seem that making the depth longer would make sense.
I'm interested at the moment in building a simple system using the Pioneer B20 full range in a sealed enclosure and I again see dimensions (width and depth) that are inconsistent.
One plan calls for a 10" wide, 6" deep, 40" high?
THANKS.
Having the longest dimension as the depth helps to reduce the intensity of rear wall reflections back through the cone. Also there has been a tendency towards narrower baffles for improved imaging in more recent years (this works well with transforming the box to have what would previously have been the width become the depth and vice versa.
As far as golden ratio's are concerned, it doesn't hurt because it ensures you don't make a box that is prone to pipe resonances. A rule of thumb is that no internal dimension should be more than 3 times that of any other. If you stick to that you should be ok. Another rule of thumb would be that you shouldn't have any two internal dimensions the same (or very close to the same).
One of the main reasons you don't see too many golden ratio boxes these days is because they tend to be ugly
Tony.
As far as golden ratio's are concerned, it doesn't hurt because it ensures you don't make a box that is prone to pipe resonances. A rule of thumb is that no internal dimension should be more than 3 times that of any other. If you stick to that you should be ok. Another rule of thumb would be that you shouldn't have any two internal dimensions the same (or very close to the same).
One of the main reasons you don't see too many golden ratio boxes these days is because they tend to be ugly
Tony.
Attached is a chart I worked out many years ago. It shows plots of the depth (left one), width (center one) and height in inches vs box volume. It's based on the 0.62: 1: 1.62 golden mean ratio used by artists for centuries.
You just need to decide on what your box volume needs to be based on your driver's T/S parameters. You can use a free box calculator program available on the WWW. Just Google search.
You just need to decide on what your box volume needs to be based on your driver's T/S parameters. You can use a free box calculator program available on the WWW. Just Google search.
Attachments
Well certainly as you say a deeper cabinet (although an eyesore) would be better than the dimensions for this Pioneer B20 project.
It shows 9.75" wide and only 5.5" deep.
For an 8" woofer I would think that would be a problem (and even have some audible negatives?)
I'll copy that graph for future reference.
It shows 9.75" wide and only 5.5" deep.
For an 8" woofer I would think that would be a problem (and even have some audible negatives?)
I'll copy that graph for future reference.
Let me tie some of these comments together.
1/ internal box ratios are best if they are multiples of irrational numbers so that a standing wave across one set of opposite box walls does not reinforce any of the others. Be careful with the square root of 2.
2/ the golden ratio (phi) is an appealing irrational number. Due to one of its properties it is easy to calculate the internal box dimensions. Take the total required gross volume (ie includes volume of back of driver & all bracing) and find the cube root. That is D1. Then multiply D1 by phi for D2. Take D1 and divide by phi to get D3. Choose any side for the driver. Each has it's advantages and disadvantages. A Classic GR, sets D1 to width and D2 to height. Rotating it such that D1 is now depth fits today's aesthetic better.
3/ if one dimension starts to become significantly larger than the others (wintermute mentioned 3x) then the box becomes a quarter-wave resonator (ie a TL) if it has a hole/port/terminus in it, and a half wave resonator if sealed.
dave
1/ internal box ratios are best if they are multiples of irrational numbers so that a standing wave across one set of opposite box walls does not reinforce any of the others. Be careful with the square root of 2.
2/ the golden ratio (phi) is an appealing irrational number. Due to one of its properties it is easy to calculate the internal box dimensions. Take the total required gross volume (ie includes volume of back of driver & all bracing) and find the cube root. That is D1. Then multiply D1 by phi for D2. Take D1 and divide by phi to get D3. Choose any side for the driver. Each has it's advantages and disadvantages. A Classic GR, sets D1 to width and D2 to height. Rotating it such that D1 is now depth fits today's aesthetic better.
3/ if one dimension starts to become significantly larger than the others (wintermute mentioned 3x) then the box becomes a quarter-wave resonator (ie a TL) if it has a hole/port/terminus in it, and a half wave resonator if sealed.
dave
"Not" really, as long as there is enough damping material inside to dampen any standing waves. I like my enclosures "near" cubic, but not exactly cubic. The cube has the greatest internal volume with the least surface area. This will minimize the potential for box reradiation through stuctural resonances.
If a panel is going to resonate, a high Q one is preferable to a low Q one as it will be less audible.
dave
I'm sorry but this is not correct. The shape of the box cannot have any effect on the Q of a resonance. It also doesn't have any effect on the modal density, that depends only on the total volume. Thats why as far as the internal box effects are concerned shape doesn't have much of an effect.
Are you saying this because of Floyd Tooles work? because I don;t think that applies here. And if not then what are you basing this on because it seems to me that the effect would be the opposite.
Floyd's work only supplemented my supposition that a high Q resonance is better by providing research that shows a high Q resonance is less audible.
My reasoning for such a Q has to do with the energy available to excite a resonance and the distribution of energy in music.
This ties in with my box building philosophy of pushing panel resonances up as high as feasible. If one has a resonance and it is high Q then sustained energy in a very narrow bandwidth is required to excite the resonance.
In the unlikely situation where the resonance is excited, Floyd's research shows that it will be less audible than (with more available energy to excite) low Q resonance.
dave
My reasoning for such a Q has to do with the energy available to excite a resonance and the distribution of energy in music.
This ties in with my box building philosophy of pushing panel resonances up as high as feasible. If one has a resonance and it is high Q then sustained energy in a very narrow bandwidth is required to excite the resonance.
In the unlikely situation where the resonance is excited, Floyd's research shows that it will be less audible than (with more available energy to excite) low Q resonance.
dave
Floyds work applied to acoustic radiated resonance, not box resonances. My reasoning goes as follows: If the resonance is high Q then there is a stronger likelihood of its rising above the background of "noise" in the sense of all the other types of aberations going on such as diffraction, other resonances, etc. and let's not forget the signal itself. Floyds work assumed that the resonances were such that they rose above the basline of the signal and his study went from there. If the level of the resonances never reach the baseline of the signal such that they add significantly to the output then his conclusions don't apply.
Pushing box resonances as high as possible is logical, I do the same myself, but the statement "If one has a resonance and it is high Q then sustained energy in a very narrow bandwidth is required to excite the resonance." is not correct. A high Q resonance takes less energy to excite than a low Q one - bandwidth is not relavent if we are talking about musical types of signals which are very impulsive and contain broadband excitation. Bandwidth would be relavent for steady state excitation. And High Q resonances ring longer - the ear masks less in time than it does in frequency.
Finally, Floyds results implied that the area under the resonance was what mattered, so yes, a narrow Q resonance at the same level as a broad one would be less audible. But thats not what happens with a high Q - its generally higher but narrower.
In the end its a guess either way since there are no direct studies to quantify this either way. But applying Floyds conclusions to the situation is a misnomer IMO.
Earl,
You are saying the same things as i am and coming to different conclusions. Since the resonance needs energy at its frequency the bandwidth is important, because the likelihood of music supplying the necessary energy is low. A low Q resonance can accept energy over a larger bandwidth. To figure which one requires more energy to excite you'd actually have to measure the area under the curve.
If a box resonance does not produce acoustic radiation then i don't see it as a problem. This makes you 1st argument moot.
dave
You are saying the same things as i am and coming to different conclusions. Since the resonance needs energy at its frequency the bandwidth is important, because the likelihood of music supplying the necessary energy is low. A low Q resonance can accept energy over a larger bandwidth. To figure which one requires more energy to excite you'd actually have to measure the area under the curve.
If a box resonance does not produce acoustic radiation then i don't see it as a problem. This makes you 1st argument moot.
dave
Dave
We weren't saying the same things at all. The way you said it the first time was incorrect. You are now correct to say that it is the integral of the resonance times the excitation, but that is NOT at all what you said the first time. Its quite a bit different. Because the high Q resonance has such a large value at resonance it can easily equal the low energy level of the low Q excitation.
And your last point is meaningless because a box resonance ALWAYS produces radiation - its the level that is important. And thats exactly my point! If the level is low enough so as to not contribute significantly to the sound from the main driver then it doesn't mater, just as you say, BUT, the higher Q resonance IS MORE LIKELY to do that than the low Q one, not less.
hehe It's funny that I think that the golden ratio dimention boxes are ugly (I know that things in the golden ratio are supposed to be pleasing) I have a pair of golden ratio 70L boxes and frankly they look very "boxy" They are old school and have a wide baffle and shallow depth. I'm going to rebuild them sometime, I might stray from the golden ratio when I do but I will certainly be making the narrower dimention the baffle. I personally think having a narrow deep speaker looks much nicer than a wide shallow one.. also appears to take up less space
Tony.
They are old school and have a wide baffle and shallow depth. I'm going to rebuild them sometime, I might stray from the golden ratio when I do but I will certainly be making the narrower dimention the baffle. I personally think having a narrow deep speaker looks much nicer than a wide shallow one.. also appears to take up less space Tony.
I simply tried to answer the OP's question. GM box geometry is a good starting point for a noob building his first cabinet. It may be old school but is effective. Is it maximally effective? Maybe not, but alternative box shapes come with their own problems to solve.
Like most things associated with speakers building, there's no perfect way. Just a whole host of compromises.
Gedlee's cube comes with damping challenges and sloping front boxes can be a challange to build. Unless, of course, you are an accomplished carpenter. BTW, a sphere is the smallest shape for a given volume and structurally superior to a cube. About 20% lower surface area, but obviously, more difficult to build.
Like most things associated with speakers building, there's no perfect way. Just a whole host of compromises.
Gedlee's cube comes with damping challenges and sloping front boxes can be a challange to build. Unless, of course, you are an accomplished carpenter. BTW, a sphere is the smallest shape for a given volume and structurally superior to a cube. About 20% lower surface area, but obviously, more difficult to build.
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I didn't say cube - please don't misquote me. And what exactly are the "damping challenges"? The box aspect ratio is not a factor in that.
And please, the lecture on the sphere! That's real practical to build and the volume to surface area rather is rather elementary. I excluded it for the obvious reasons.
So, what's more important than box shape is the box materials ability to reflect sound?
(In simple terms)?
Concrete would be better than plywood for example?
If that's the case, you would think what's really important is the quality of the deadening material inside the enclosure?
Like a sound foam instead of "pillow stuffing"?
(In simple terms)?
Concrete would be better than plywood for example?
If that's the case, you would think what's really important is the quality of the deadening material inside the enclosure?
Like a sound foam instead of "pillow stuffing"?
"nearly cube" might as well be a cube. Sorry for not precisely quoting you. The damping challenges are finding the right type and amount to accomplish the task. Could be a challenge for a noob.
Here's an exact quote from your prior post:
"The cube has the greatest internal volume with the least surface area." - wrong as a general statement which could mislead a noob. Hence the lecture.
Look, many here have gotten off on what I believe is a tangent other than what the OP asked for.
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