A 30cm cubical enclosure will have three identical half-wave mode, so: 343 / 0.30 / 2 = 572Hz. This is probably a bad idea unless the driver is low-passed significantly below this frequency. 353Hz and 925Hz modes will be "generated" around the original 572Hz if the two other dimensions are instead made 30cm*1.618 and 30cm*0.618, thus spreading the resonances to non-multiples of any harmonics of the lowest one.
If you google 'Master Handbook of Acoustics' you will find in the fourth spot a PDF copy hosted on AmazonAWS. I'm not sure if this is naughty or not, but it has been there for a long time so assume nobody has made a take-down request.
Anyway if you jump to page 266 you can see what the book has to say on ratios and modal distributions including non-rectangular shapes. This is talking specifically about rooms, but I think the same principles apply in a speaker cabinet regarding even distribution of resonances they will just be at a higher frequency.
Anyway if you jump to page 266 you can see what the book has to say on ratios and modal distributions including non-rectangular shapes. This is talking specifically about rooms, but I think the same principles apply in a speaker cabinet regarding even distribution of resonances they will just be at a higher frequency.
You need to keep a few things in mind here. If you'll forgive the list:
- Golden ratio is just an irrational proportion, no more.
- A set of general mathematical proportions can be applied to the internal or external dimensions. If applied to the former, the latter is unlikely to continue to conform, depending on construction.
- Boxes built to golden ratio proportions do not (cannot) have some kind of generic 'sound' that is universally applicable, so asking how a speaker built to an unknown golden ratio configuration 'sounds' is basically unanswerable. The only time you could say something meaningful in this regard is if you directly compared, technically and in blind listening, to a speaker using identical drive units, to the same acoustic alignment, and with similar enough baffle proportions to ensure diffraction & step-loss are in approximately the same regions & degrees. And note that whatever findings may or may not result in this case, they won't apply to anything else.
- Golden or any other acoustic ratio are not always practical, since, for example, a quarter-wave design has acoustically functional proportions that dictate the form factor to a large (or total) extent. You may also in some compact cases find yourself in a situation where you can't physically fit the drive unit, vents etc. into the enclosure.
- The 'sound' of a loudspeaker is a combination of a very large number of factors: the drive units, the alignment, as relevant the crossover, the on / off axis frequency responses, impedance, distortion behaviour etc., and the construction materials and methods, in addition to a basic set of proportions. As I noted above, golden ratio may allow a small reduction in damping if applied to internal proportions. If applied to external dimensions, it is often considered aesthetically pleasing, though not everyone will necessarily favour this and the finish will play a significant role here also.
Thanks Scottmoose.
It sounds like it is very difficult to get a box to play the way you want.
The dimensions of a Golden Ratio will be different depending on what volume you want.
The baffle will become larger with increasing volume.
The reflectors, the standing waves, the clearing resonances for the box are spread out with a golden ratio, right?
It should be better for a smoother frequency curve?
I hope it works that way.
If it does not work, I will not build such a box.
It sounds like it is very difficult to get a box to play the way you want.
The dimensions of a Golden Ratio will be different depending on what volume you want.
The baffle will become larger with increasing volume.
The reflectors, the standing waves, the clearing resonances for the box are spread out with a golden ratio, right?
It should be better for a smoother frequency curve?
I hope it works that way.
If it does not work, I will not build such a box.
Google tends to give different results depending on who is looking from where. I get lots of ads for the book, not pdf (likely a pirate), i do have a gardcopy somewhere.
dave
The hardest step in coming up with a CGR is the iteration that gets you too an external GR aspect. Inside is not the same ratio. GR on the inside will not net you GR on the outside, thicker the material the greater the deviation,
dave
Right, ultimately depends why you're using it & whether you go for the internal or external application.
Yes and no. As I say, with golden or another irrational set of proportions / acoustic ratio you may be able to get away with a small reduction in damping, which is good in itself -sign of efficient engineering, doing the most with the least. But unless the direct alternative to which you're comparing is fairly badly designed, it shouldn't have significant issues in the response or alignment in the first place. It's nice enough, so if you can do it and it fits your requirements, then it's a good set of proportions to use, but it's certainly not a make / break scenario.
Yes and no. As I say, with golden or another irrational set of proportions / acoustic ratio you may be able to get away with a small reduction in damping, which is good in itself -sign of efficient engineering, doing the most with the least. But unless the direct alternative to which you're comparing is fairly badly designed, it shouldn't have significant issues in the response or alignment in the first place. It's nice enough, so if you can do it and it fits your requirements, then it's a good set of proportions to use, but it's certainly not a make / break scenario.
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Internal is the answer. But I can create a baffle as big as the inside if I mill the edges at a 45 ° angle.
I can try with Golden Ratio. Is not worse than that I fail. You always learn something.
The volume will determine the size of the baffle.
Feels a bit like buying a ticket.
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So far everyone's been talking about internal sound waves, but wouldn't the golden ratio ( or something similar ) lead to the panels of the speaker having different mechanical vibration, apart from the sides that will resonate like a tuning fork ( possible reduced by making one side thicker than the other, or adding weight ).
Maybe a thicker baffle can solve that?
The baffle will be the largest. But the box will be quite small when I use 12 liters of volume. I can contribute some braces inside.
The dimensions will then be 37cmx23cmx14cm. Internal.
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Only in the same way that all loudspeaker panels have resonance; there is no reason for a box with golden ratio proportions to 'resonate like a tuning fork' any more than anything else would; that is a question of construction rather than ratios, which is always the case.
Aesthetically speaking
Golden Ratio is visually pleasing.
Having seen some rather goofy looking speakers. I found some of my favorite designs were golden ratio, or at least very close.
Plenty speakers sound fine not being golden Ratio. But most speaker designs assume a narrow and tall enclosure.
Using golden Ratio for overall front baffle dimensions. Makes a very nice looking cabinet.
For correct volume you just adjust depth.
Far as micro details. Driver quality and crossover design are the biggest contribution. As with any speaker.
Far as mystical magical boxes.
Assume common well known knowledge as far as diffraction and dispersion. Tall, narrow vertical alignment for horizontal dispersion etc etc. The basics.
I found if the width is based on golden ratio according to speaker dimensions.
It will be narrow like any other design. And a large chamfer edge makes it fine.
Then if height is GR based as well.
It's just plain old good looking speaker.
Golden Ratio is visually pleasing.
Having seen some rather goofy looking speakers. I found some of my favorite designs were golden ratio, or at least very close.
Plenty speakers sound fine not being golden Ratio. But most speaker designs assume a narrow and tall enclosure.
Using golden Ratio for overall front baffle dimensions. Makes a very nice looking cabinet.
For correct volume you just adjust depth.
Far as micro details. Driver quality and crossover design are the biggest contribution. As with any speaker.
Far as mystical magical boxes.
Assume common well known knowledge as far as diffraction and dispersion. Tall, narrow vertical alignment for horizontal dispersion etc etc. The basics.
I found if the width is based on golden ratio according to speaker dimensions.
It will be narrow like any other design. And a large chamfer edge makes it fine.
Then if height is GR based as well.
It's just plain old good looking speaker.
Golden Ratio consists of 3 numbers that are well spread out.
0.618
1
and
1,618
Internal dimensions that should work together and give an even spread to reduce standing waves.
Do not know if there is a formula that can give the right measurements internally if you talk about the volume you want?
0.618
1
and
1,618
Internal dimensions that should work together and give an even spread to reduce standing waves.
Do not know if there is a formula that can give the right measurements internally if you talk about the volume you want?
Not so, you are assuming that the sole application of golden ratio is three-dimensional, which isn't the case. Golden ratio can be applied to the proportions of two dimensional shapes, e.g. golden rectangle, as was noted above for a front baffle.
https://en.wikipedia.org/wiki/Golden_rectangle
Frankly, as I've tried to point out several times, it's far from being a magic bullet, and in most cases not something to necessarily get very worked up about from an acoustic POV.
https://en.wikipedia.org/wiki/Golden_rectangle
Frankly, as I've tried to point out several times, it's far from being a magic bullet, and in most cases not something to necessarily get very worked up about from an acoustic POV.
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I wouldn't invest to much hope in this really Leif. If there where a substantial advantage we would see a lot of 1,61 oriented designs. We dont. This ratio is not like a hidden secret or anything... For instance, if you make all your bracing with the same distances, even when based on GR, you will get a number of surfaces that will resonate at the same frequency and Q value. So there might be a audio signature of this design - better, and even more irrational, would be to create bracing with no repeating distance i.e. totally chaotic - this will spread all resonances in the cabinet and make a more silent one than the 1,61 all-around based one.
I would say that diffraction is a far greater problem with a box - it seriously effect the frequency response. Look into that also (instead?) and see of you can make rounders of the edges of the box.
Good luck however you choose to proceed!
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I would say that diffraction is a far greater problem with a box - it seriously effect the frequency response. Look into that also (instead?) and see of you can make rounders of the edges of the box.
Good luck however you choose to proceed!
//