Late to this...
Those wooden domes are gorgeous.
( A few years ago I wanted to experiment with some free form construction techniques, and I had a couple of 4" Vifa full range speakers ( made for Revel ) so I made a couple of spheres. They were a proof of concept, Cost me $35 )
Check out the 'White Paper' on the B&W website regarding the "tail" of the midrange driver of the Nautilus speakers - see also "flow resistance damping" and other such things from Carlson, Jensen, etc from years ago.
A minor issue, but if you want best, you have to go all the way. If you don't have a tail, you get turbulence on the backside. The B&W units are the same shape they are, as high efficiency cars are tear-drop shaped.
As alluded to in an earlier post, the tear drop overcomes the issue of the inside of a sphere as being a really bad shape for internal standing waves.
dave
Im considering sealed tweeters so internal waves is not an issue. Even a tear drop internals can have stuff fibre glass that sucks up most of the rear wave for a high midrange. Heck most people buy simple rectangle boxes ignoring the rear wave issue...we are way ahead.
Now I have to find the thread with that great explaination of how to build a moudling (it was in a waveguide thread somewhere). I need a 18" round ball....bowls are not that big so I will take my three year old's 18 inch ball she has ( I was sitting watching her this morning and it clicked 😀). I will build a moulding from it then use that moulding to make a fibre glass shell (all in theory of course).
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A simple rectangular box has better internal standing wave distribution than a sphere (at least if attention is paid to the aspect ratios).
dave
The rear wave goes directly back throught the woofer how can it be better?
Are you talking about 'Golden ratios' in speaker designs...there is little evidence of those being meaningful in a speaker design considering the average size of a speaker box and the mid range generally being sealed and having tons of absorption foam or fibreglass.
If that isnt enough and you have a bigger box that has meaningful size to actually create a standing wave then just stick a 3" PVC pipe sliced in half to each wall to diflect the sound. No issues.
A well choosen rectangle (no dimension an interger multiple of another -- irrational numbers are your friends) will have 3 different primary standing wave modes, with relative energy spread across all 3. A sphere has 1 with all the energy at the same place.
In a multiway, some of these issues can be mitigated with enclosure volume & XO points, but in my world a "midrange" usually does it all, and these considerations are very important. And if one wants a great speaker you have to worry about stuff well below the average signal (at least 40 dB) so they still play a role.
dave
In a multiway, some of these issues can be mitigated with enclosure volume & XO points, but in my world a "midrange" usually does it all, and these considerations are very important. And if one wants a great speaker you have to worry about stuff well below the average signal (at least 40 dB) so they still play a role.
dave
...put a wall with different hole sizes between the two parts and be done with the discussion.😎
Peter
Peter
doug20
I'm sure there are numerous ways to lift a shape rather than fabricate it.
I used the techniques employed to make plaster cast of faces and objects to cast from a Styrofoam ball ( sold in craft stores ).
It also depends on what you are after: a negative or a positive shape, and is the form sacrificial.
I found a shape similar to the B&W ball with"tail" in a modern floor lamp that would be a good candidate to cast from.
And any shape that can fabricated in clay or other sculpting materials can be used to create the form
Syd
I'm sure there are numerous ways to lift a shape rather than fabricate it.
I used the techniques employed to make plaster cast of faces and objects to cast from a Styrofoam ball ( sold in craft stores ).
It also depends on what you are after: a negative or a positive shape, and is the form sacrificial.
I found a shape similar to the B&W ball with"tail" in a modern floor lamp that would be a good candidate to cast from.
And any shape that can fabricated in clay or other sculpting materials can be used to create the form
Syd
Interestingly enuff, just what i sketched out last nite. The partition is holey and also contains 6 slot ports. The holey braces for the drivers (not drawn) will act as attachment points for the driver screws and further break up the front half
dave
Attachments
truly nice Dave!
from the b&w site, it appears that there's more in the shape than just teardrop outside also for the mid-woofer, look at the sixth picture from the 2nd row:
View the Innovation technology at Bowers & Wilkins - The World's leading Hi Fi and Home Theatre Brand
it seems like two concentric teardrops, acting like some TL to dampen rearwave?
from the b&w site, it appears that there's more in the shape than just teardrop outside also for the mid-woofer, look at the sixth picture from the 2nd row:
View the Innovation technology at Bowers & Wilkins - The World's leading Hi Fi and Home Theatre Brand
it seems like two concentric teardrops, acting like some TL to dampen rearwave?
This one?
I have referred to that one often
Given that it is a wireframe, there is a teardrop to define the outside, and then another to define the inside (ie the material has thickness -- note that thickness is different so that the inside is a different shape than the outside). Also of note is the back half of a teardrop on the magnet to reduce turbulence.
dave
An externally hosted image should be here but it was not working when we last tested it.
I have referred to that one often
Given that it is a wireframe, there is a teardrop to define the outside, and then another to define the inside (ie the material has thickness -- note that thickness is different so that the inside is a different shape than the outside). Also of note is the back half of a teardrop on the magnet to reduce turbulence.
dave
yes i was looking at that one, tought it was empty like some sort of folded TL... nice to discover the world is simplier
Might like to go back a few years and have a look at the many designs by the "Passion-Elipson" guys, or even further back to the "Eckmiller" designs about 60 - 70 years ago (ie Eckmiller 016 Coax) - much food for thought.
... and the "Rethym audio" folks have done quite a bit of work on the Lowther drivers around the rear of the magnet structure to get rid of a lot of the non-linearity of freq response - we can all learn something from this - I use one of those Ikea bowls to complete the "jacket" aroung the rear of the driver/magnets with good results - highly recommended!
Interesting, i'm in the middle of building a speaker with this shape!
I'm actually using a bongo drum with an interesting shape as the base and i'm mounting a alpair 5 on a modified baffle that i'm mounting on where the skin of the drum used to be located.
it was actually my wifes idea but i'm quite enjoying the unusual teardrop shape. Its still work in progress but i think it will be great aestethically when done!
rethm
Most people are using the wooden ones at the bottom.
http://www.ikea.com/us/en/search/?query=blanda
Warning: both are ^&$$@ Flash sites.
dave