If I do it I'll do it right with CNC machined alluminum molds. But these could be as high as $4000. A bit steep on a "maybe".
"But these could be as high as $4000."
Oh, that's not so bad, I thought it was in the tens of $K.
So obviously the problem is not enough qty to amortize the mold cost.
Hopefully the kits will increase awareness and achieve critical mass in demand.
tinitus, that's not an ellipse.
But it's an interesting idea to take it to the limit and just leave out the mold.
But it seems like an awful lot of handwork would be required.
Oh, that's not so bad, I thought it was in the tens of $K.
So obviously the problem is not enough qty to amortize the mold cost.
Hopefully the kits will increase awareness and achieve critical mass in demand.
tinitus, that's not an ellipse.
But it's an interesting idea to take it to the limit and just leave out the mold.
But it seems like an awful lot of handwork would be required.
noah katz said:
No, it a "super-ellipse"
Thats the one I may do, starting from round to ellipse and ending with super-ellipse
Those kind of molds last for about a half dozen parts, then they split or somthing. A solid piece of alluminum is the only thing that I have found robust enough for a lot of parts.
gedlee said:
You just need to use polyesther filling and finish the mold with glassfiber and topcoat, then its more durable, the tricky part is to end with the right measurements, which I reckon will have to be very precise, at least at the throat ... but yeah, its a lot of work
Re: horn format
I think you may assume I used CD horns with sharp edges. I do not.
In fact, I had spoken to Dr. Geddes in 2005 about making an asymmetrical horn very much like what is being discussed here.
In the end, I chose to do my own but do not discount the elliptical horn Earl's talking about. It could be done on the same CNC I use to make my horns.
The only thing I am adamant about is the axisymmetrical pattern. I don't want a large vertical radiation angle. All other criteria I agree with what I see discussed here, and am impressed with Earl's work.
By the way, Earl is right about the GPAF 2006 thing. I do not know if random placement is always better than symmetrical, but I do think he has a point. It's an attractive concept. The thing is, I did some models to try and confirm or deny Geddes/Welti configurations using CARA and I don't want to go into a long winded thing but I was not completely convinced either way. What I am convinced of is that multiple subs are better than one, and that models such as can be made with CARA are useful for finding the best locations. I am also sure that I was too hard on Dr. Geddes, having been frustrated by some of the same kinds of back and forth that have happened in this thread. Still, I have a great deal of respect for Dr. Geddes and, Earl, I hope you know that.
angeloitacare said:
I think you may assume I used CD horns with sharp edges. I do not.
In fact, I had spoken to Dr. Geddes in 2005 about making an asymmetrical horn very much like what is being discussed here.
In the end, I chose to do my own but do not discount the elliptical horn Earl's talking about. It could be done on the same CNC I use to make my horns.
The only thing I am adamant about is the axisymmetrical pattern. I don't want a large vertical radiation angle. All other criteria I agree with what I see discussed here, and am impressed with Earl's work.
By the way, Earl is right about the GPAF 2006 thing. I do not know if random placement is always better than symmetrical, but I do think he has a point. It's an attractive concept. The thing is, I did some models to try and confirm or deny Geddes/Welti configurations using CARA and I don't want to go into a long winded thing but I was not completely convinced either way. What I am convinced of is that multiple subs are better than one, and that models such as can be made with CARA are useful for finding the best locations. I am also sure that I was too hard on Dr. Geddes, having been frustrated by some of the same kinds of back and forth that have happened in this thread. Still, I have a great deal of respect for Dr. Geddes and, Earl, I hope you know that.
Re: Re: horn format
we should all respect each other as human beings, no matter the title
Wayne Parham said:
we should all respect each other as human beings, no matter the title
hi Wayne
sorry if i upset you. it was not my intention. I didn't realize the kind of horns you use.
sorry if i upset you. it was not my intention. I didn't realize the kind of horns you use.
tinitus said:
I've made and used every kind of form that you can imagine and as anyone in the biz will tell you anything but solid metal will fail eventually, its just a matter of when.
Re: Re: horn format
Wayne - thanks.
It's not so much that I disgaree about the vertical pattern, I just have not found it to be a problem and the extra expense to pursue something that may not pan out is just not in the budget right now. Maybe someday, as I said.
Wayne Parham said:
Wayne - thanks.
It's not so much that I disgaree about the vertical pattern, I just have not found it to be a problem and the extra expense to pursue something that may not pan out is just not in the budget right now. Maybe someday, as I said.
gedlee said:
Offcourse, a solid glassfiber mould will eventually wear down after several years of daily use, and it will have to be maintained with carefully vaxing
And some shapes are good fore glassfiber, and some are not or more difficult, but a waveguide should be ok but yes, if it aint done right it may be ruined even in the first try
I know that from having worked with glassfiber moulds professionally in boatbuilding which I reckon is more demanding than a small waveguide
I see no reason what so ever why a solidly build glassfiber mould couldnt be used - but its ok, if you dont like it so be it
You do prototyping like that?gedlee said:
Why not aluminum machined throat and CNCed MDF for prototyping?
Re: Re: horn format
Everyone has made bad moves in the past, why not focus on making good things and keep spirits high?
The concept of random placement depends on room configuration, and the purpose it to excite the most modes with the least number of subs. Still you have to plan the locations and do the analysis.Wayne Parham said:
Everyone has made bad moves in the past, why not focus on making good things and keep spirits high?
tinitus said:
But my waveguides aren't fiberglass. Fiberglass is a lot easier on the mold than casting. The casting generates a lot of pressure and heat as it cures because it does this in about 3 minutes. This tears up the mold a lot faster than glass and polyester. I destroyed molds in one cast that would have stood up to fiberglass for a long time.
flying speakers
Dr. Geddes,
I read a while back when you were overseas at AI, the ESP variant of your design was popular in clubs. I know flying is common in clubs. I was wondering, do you flip the speakers putting the waveguides at the bottom when you hang them overhead?
Dr. Geddes,
I read a while back when you were overseas at AI, the ESP variant of your design was popular in clubs. I know flying is common in clubs. I was wondering, do you flip the speakers putting the waveguides at the bottom when you hang them overhead?
No we didn't, but I guess that you could, and maybe now that I think about it you probably should. I had very little to do with the actual installations over there. They were done by a contractor. I concentrated on setting up the factory. From what I understand, the thing that the clug owners liked was how loud the systems played without loosing quality.
So elliptical waveguide molds may be cost prohibitive at the moment, but out of curiosity what does a proper one look like? Is it as simple as calculating the contour repeatedly while varying the exit angle as you rotate around from the 90 degree side to say a 40 degree top? And should the distance from throat to exit stay the same meaning these would need a curved fronted cabinet?
Quite perceptive. You are absolutely correct about the contour.
People have long thought that the cross sectional area of the elliptical had to satay the same as it went from round to an ellipse. This ends up with something that doesn't work very well. The idea of maintaining the cross section comes from Horn theory since it deals with areas. But in my theory only the contour shape matters, the cross section is irrelavent. So one just uses the same equation at each rotational angle, but with a different theta.
It would be better to have each path length a different length as this will minimize the coherence of a standing wave either in the mouth or along the length. This is why I would not expect an elliptical waveguide to exhibit an axial hole in the response.
There is a lot to like about the elliptical, except its cost. It would easily double the cost of the current waveguides which are already expensive. An Abbey with an elliptical 90 x 40 would be quite attractive to me.
People have long thought that the cross sectional area of the elliptical had to satay the same as it went from round to an ellipse. This ends up with something that doesn't work very well. The idea of maintaining the cross section comes from Horn theory since it deals with areas. But in my theory only the contour shape matters, the cross section is irrelavent. So one just uses the same equation at each rotational angle, but with a different theta.
It would be better to have each path length a different length as this will minimize the coherence of a standing wave either in the mouth or along the length. This is why I would not expect an elliptical waveguide to exhibit an axial hole in the response.
There is a lot to like about the elliptical, except its cost. It would easily double the cost of the current waveguides which are already expensive. An Abbey with an elliptical 90 x 40 would be quite attractive to me.
