Golden Ratio speakers?!

What's with this new obsession with 45° chamfers? The effectiveness of form varies with angle (45° is not necessarily optimal) and in particular, proportion. In most cases, small chamfers < about 1.5in are mostly cosmetic with little significant impact on behaviour. This is not difficult to model.
I'm thinking of a picture that Dave showed how different shapes of a baffle affect the sound.
An angle with edges showed the next best thing.
The spherical was the best.
I do not know how much it affects, but it made a difference. The frequency curve changed a lot how the baffle was designed.

https://www.diyaudio.com/community/threads/mar-ken-12p-with-side-vents.385431/#post-7005259
 
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No 45 ° isn't probably an exact value. It works safely with other angles.
I have imagined that a smaller baffle places the sound more precisely in the soundscape. Do not know why.
Of course, it depends on where but puts the speakers and where you sits.
I have milled an angle of about 40 ° on the Nostromo speakers now. They are so big that they are very close to the driver. A11MS.
Think it became easier to place different sounds.
 
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and in most cases not something to necessarily get very worked up about from an acoustic POV.

A GR is an interesting mathematical entity, that the GR is essentially equivalent to the Fibonaci sequence, and is capable of many interesting tricks that it can do.

For instance, the GR (in 3D) is 0.618:1:1.618. 1/1.618=0.618. Fibonaci spirals. Many more.

It is a very interesting number.

It is a convenient set of irrational numbers to do boxes, it is a very nice aesthetic shape for a rectangle, but it is not really special in any other way. If it suits your needs excellent.

dave
 
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Diffraction is the next part of a design.
45 ° edges are the next best thing to use. A spherical shape is said to be the best

Given the material we can take materail off (unless the box is specifically built to accomodate large roundovers, a chamfer gives an effectively larger radius and is, to my mind, more effective in most practical applications,

Ideally you would like 3 or 4” minimum to really have a significant affect (ref Speaker Builder article), something tricky to achieve without jumping thru hoops (which Leif has done twice so far with trapezoid miniOnkens).

dave
 
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LeifB60

Member
2015-05-18 5:50 pm
Sweden
Sorry for what? :scratch1: I'm simply stating a fact.
Well, I have not fully followed your recommendations on the construction drawings.
  • 16mm mdf first.
  • I have used this material as damping inside (all sides except the bottom)
https://www.biltema.se/bil---mc/bil...r/dampmaterial-till-hogtalare-5-st-2000018639
-4mm2 internal cables

I can not really judge your entire Nostromo construction.

Lacks birch plywood and wool as damping material.

I will continue and compare with different lengths of bass reflex tubes.

Seems like the minor disturbances in 7khz-12khz have disappeared. Do not know yet if it is due to the base reflex tube or the 40 ° angle of the edges. It should be explored. May put back the bass reflex tubes that are 6.3 cm long again. If it comes back, I know what it's due to.
 
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It's not Nostromo then so best not described as such.

Duct length in itself will have zero influence on anything in the 7KHz - 12KHz band; nominal tuning is < 100Hz & any 1/2 wave modes should be heavily suppressed and far below that region; if you have problems it's from a different cause. Very large, shallow chamfers may reduce a small amount of edge diffraction at the lower end of that range but primary influence will likely be in the ~1KHz - 3KHz region. You don't specify how you're identifying these issues, but I suspect some methodological variation may be at work.

Re the box, 16mm MDF will have audible colourations from panel resonance unless heavily braced and / or strategically damped with bitumen a la BBC type designs (albeit is a bit thick for those). The foam appears to be the type I recommend not using for this construction. Forgive me, but I don't recall what the driving amplifier is, but if it is not a high output impedance SET, then you may also have a mismatch, as that box was designed for those conditions.
 
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