a prototype -- this would be realizable with a table saw, router & glue...
(oh... & some plywood)
dave
An externally hosted image should be here but it was not working when we last tested it.
(oh... & some plywood)
dave
Hi,
all I'll say is there is no such thing as a an acoustic diode.
B&W's tapered tube is designed using TL theory.
It is not true that TL lines don't act on the back waves to the cone.
A TL line above a certain frequency related to its length can
effectively dissapate all the backwave energy of a cone and
prevent any reradiation of backwave energy through the cone.
/sreten.
all I'll say is there is no such thing as a an acoustic diode.
B&W's tapered tube is designed using TL theory.
It is not true that TL lines don't act on the back waves to the cone.
A TL line above a certain frequency related to its length can
effectively dissapate all the backwave energy of a cone and
prevent any reradiation of backwave energy through the cone.
/sreten.Hi,
sreten:
If you are looking at the photo of the snail prototype from Planet10, you can say that the only fault is the squared shape at the begining of the line (close to the speaker): the almost full amount of waves energy rebounds on the walls before part of this energy is propagated in the tapered snail: that's why B&W had to use a sphere before the tapered tube. (Dave, don't
me, this snail is however very nicely builded, congratulations.)
Also, such a line has to be obligatory stuffed because there is no way for the waves to be dampened, except the tapered section; but it's largely not enough.
sreten:
No, it's an acoustic diode using stuffing in the tapered tube; the sphere acts as a perfect wave guide allowing the complete amount of back waves to enter in the tube. Then the energy is dissipated in stuffing. OK, its lenght is a quarter waves lenght of the lower frequency the mid driver has to reproduce but the foundamental principle isn't the TL line principle.
Only if you are able to design a shape which can perfectly propagate the waves from begining (the very close surrounding of the driver cone) to the end of the line...and even so, part of the wave will return in the line toward the driver because the impedance of air at the end of the line is different than the impedance outside. And this phenomenon isn't depending of the waves lenghts.
If you are looking at the photo of the snail prototype from Planet10, you can say that the only fault is the squared shape at the begining of the line (close to the speaker): the almost full amount of waves energy rebounds on the walls before part of this energy is propagated in the tapered snail: that's why B&W had to use a sphere before the tapered tube. (Dave, don't
me, this snail is however very nicely builded, congratulations.)Also, such a line has to be obligatory stuffed because there is no way for the waves to be dampened, except the tapered section; but it's largely not enough.
crazyhub said:
Me and a mate took a trip to the B&W factory a couple of years ago now and they had a cross section of the mid enclosure on the 800 series. It was interesting to note that there was small baffles within the tapered tube which had a seemingly random amount of holes of various sizes. Through some of these holes were tubes and damping.
The effect was to strip phase information from the signal and diminish the output level whilst preventing reflections. Looked very cool and near impossible to replicate for the average DIY'er I might add. You'd have to be very dedicated to come up with a reasonable fascimile.
pinkmouse said:I don't suppose you got any pics Tony? I'm pondering something like that for the HM100s.
I did have but they have long since been lost through the formats and computer swapping since that time.
We listened to the old style 800's with the 15" bass driver and I was very impressed at the time but I've since revisted the newer model at hifi shows and recently the Northern Sound & Vision show. They now only sound average to my ears nowadays. I'm not sure if it was problematic rooms I was hearing though.
ShinOBIWAN,
thanks for the informations about the walls, tubes and holes in the B&W tapered tube; I guess the goal is to add efficiency to the stuffing with a mix of helmoltz resonators and diffusors.
I do not want to reproduce this shape because the tube would be too long for bass range...and I like the idea to go with...my idea about this matter.
Have fun with your SKA; hope to hear you soon comparing it to the AKSA55N+, notably if your feeling is the same than mine. I was soooo impressed by SKA's softness that I decided to build one, while keeping my valves integrated. Maybe it would be interesting that you compare these 2 SS to a good valves one, notably about the amount of inner-details...
Hubert
thanks for the informations about the walls, tubes and holes in the B&W tapered tube; I guess the goal is to add efficiency to the stuffing with a mix of helmoltz resonators and diffusors.
I do not want to reproduce this shape because the tube would be too long for bass range...and I like the idea to go with...my idea about this matter.
Have fun with your SKA; hope to hear you soon comparing it to the AKSA55N+, notably if your feeling is the same than mine. I was soooo impressed by SKA's softness that I decided to build one, while keeping my valves integrated. Maybe it would be interesting that you compare these 2 SS to a good valves one, notably about the amount of inner-details...
Hubert
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