MJL21193 said:
It's too bad that you live so far away Dave, I could challenge you to a listening test. Put your money where your mouth is sort of thing. I would be more than happy to build two exactly identical speakers of your design (no, not one of those frugil phool "horns").
Shut me up forever if you could tell the difference.
You may be speaking too boldly. I think you would easily hear a difference even in braced boxes. As to which you would prefer, that's not to say until you have done the comparison.
Oh and why did you deliberately misspell his speakers? Do you feel better when you do that?
planet10 said:
I think it's fair to say that all materials have their advantages and disadvantages. It's how you manage them that counts, and why composites and/or CL damping are probably the best solution, since one material can offset the disadvantages of another. Making the cabinets the same way with different different materials to compare is probably not a fair argument either, because the particular construction method used may favor the advantages of one material over the other. The only fair test is to build two cabinets in such a way that the advantages of each material are promoted over the disadvantages of each material, and then compare cost and labor.
I would tend to agree, but I doubt that others would agree to your last line. If cost and labor are the principle factors then MDF would win hands down (I've done this study). The argument is whether there is an audible difference or not and thats not so easy to determine since very few would be willing to do the level of test control required to answer this question.
pooge said:
I was thnking about that very same thing as i was considering John's offer to build 2 otherwise identical boxes... the box i had in mind is very much optimized for mostly 1/2" plywood (but very specifically uses some 3/8" MDF in a critical location to provide a dissimiilar material interface)... executing the same box in MDF would be like shooting an animal in a trap (ie MDF is just not stiff enuff to make a decent brace)
dave
This discussion on materials started as a discussion on how to promulgate Dr. Geddes designs. If the DIY community is the target, then maybe Sigfried Linkwitz's model might be considered. He offers (or did, I haven't checked lately) a range of options going from plans to complete speakers. For the Summa, the waveguide and crossovers would seem to be the critical pieces. Just plans might not be a good idea, as the waveguide is much harder to execute properly than ordinary baffles and boxes. So maybe a waveguide and foam, with complete plans for the rest would be the starting point. The builder can then decide, within reason, on the materials. A complete kit would be waveguide, complete crossover, and cut panels. For overseas customers, it might be possible to identify a shop that would manufacture the WG locally under license, if the demand were there. Maybe cooperate with a source for the drivers, so that they could be drop shipped separately to avoid overseas shipping.
Now, this ain't gonna make Dr. Geddes rich, but might buy an extra night on the town now and then. And it would get this technology in the hands of appreciative users, and maybe further the development of the line. And it might spin out a few sales of finished units at decent margins. And we could talk about how these designs sound, which is a lot more fun than talking about how materials sound.
Sheldon
Now, this ain't gonna make Dr. Geddes rich, but might buy an extra night on the town now and then. And it would get this technology in the hands of appreciative users, and maybe further the development of the line. And it might spin out a few sales of finished units at decent margins. And we could talk about how these designs sound, which is a lot more fun than talking about how materials sound.
Sheldon
Sheldon said:
You might be better posting this in the thread that was split off to discuss just that....
http://www.diyaudio.com/forums/showthread.php?s=&threadid=121618
(if you don't repost, i'll move your post, but it might be useful to leave a copy here to direct other people who missed the above thread after Dr Geddes' perception thread was split into 4)
dave
Cal Weldon said:
Cal, I know I wouldn't hear a difference. The question is, would Dave?
Cal Weldon said:
Deliberately misspell? Oh no, that must be a typo.
Just having some fun here, if that's allowed?
planet10 said:
We aren't even doing it, and you are making excuses already?
Here's the deal with braces: they are structural, therefore depending on the application, I might not use MDF. I'd use something stronger. Yes, plywood is stronger. So, whatever box it would be, the bracing material would be the same for both.
This is nothing special, just the correct way to build in the first place
If you build boxes with 1/2" plywood, then you might be hearing it's sonic signature up there at 1200Hz, so helpfully pointed out by you on the Dutch site. That would be colouration though, and go against your philosophy (or is that "mission statement"?) that the box should be silent and that you are pushing resonance up where there would be nothing to excite it (except for someone knocking on the box with their knuckles).
Any established box design (except "horns" for obvious reasons). Single driver, 2-way, 3-way.
Shut me up forever...
MJL21193 said:
The box is considerably more complex than a simple 1/2" BB shell... it does only make noise in itself if excited externally, and a knock test gives a very low level very short HF on the sides, on the other sides even higher in frequency but a bit louder. These boxes very much do a dissappearing act -- even without the aid of EnABLed drivers. maximum unbraced dimension is <5". Not shown is that we are now running the MDF spacers all the way to the back.
dave
planet10 said:
This is the one you would chose? I don't think I'd have much trouble with it - I have put together a few fairly demanding boxes in my time.
What driver is this designed for?
You would attain God-like status in my eyes IF you could tell which one was made from MDF. I would erect a shine in your honour and travel throughout the country in my 1972 Dodge Monaco wood panel station wagon, with loud hailer on the roof singing your praises!
Well, I might not go that far, but it would shut me up once and for all.
Sheldon said:
This is not too far from reality, but reality is not this flexible. First, you are correct that making the waveguide is not simple and my selling just the waveguide would be very expensive owing to the manufacturing process used. I changed that process to make it cheaper, but in doing so the limitation is that the entire baffle has to be made as one piece - its basically MDF. Now you can put whatever wood you want on the sides, or you can veneer the baffle (if you are very good because its not flat anywhere), but for me to make baffles with waveguides any other way than what I have planned would double or triple the cost of the entire project - not just the baffle. So quickly you see that the baffle is going to have to be MDF with attached waveguide and foam plug. Don't like that? Well I'll custom make a pair for about 20 times the cost of the basic kit.
Then there is no such thing as a "generic" crossover - its specific to the drivers used. That means that buying the system without the drivers makes little sense because the crossover will only work with one set of drivers - B&C. Would I do a custom crossover for specific drivers? Sure! About $1500 for a new crossover design based on different drivers. Further, I get the B&C drivers for a lot less than what I see at various outlets, so I can sell them lower than virtually any customer can buy them.
The options then appear to be sell the kit with MDF sides or not. At the cost of MDF, its not worth the time and effort to delete them. If you don't like them then just throw them away and make your own.
I have thought about options and they push the prices up dramatically. SO much so that I doubt that they would be worth the effort and certainly NOT worth what I'd have to charge to make it worth the extra time.
The idea is to sell a really great speaker at a reall great price - options make the price pretty unatrractive.
planet10 said:
If I could critique about your boxes, they are not really very structurally optimimum. A brace works a lot better if it goes across the enclosure, and the largest panels should get this kind of brace. The center board is kind of a waste since it is far stronger than needed, in the wrong plane, and the holes etc. do not help the acoustics.
In other words you have braced the wrong dimension and left the critical one fairly unsupported. A brace in the plane of the wall is not really very effective. A single one placed across the cabinet, in the center of the walls would likely be more effective than all the braces that you have lying in the same plane as the walls.
planet10 said:
You might be better posting this in the thread that was split off to discuss just that....
http://www.diyaudio.com/forums/showthread.php?s=&threadid=121618
(if you don't repost, i'll move your post, but it might be useful to leave a copy here to direct other people who missed the above thread after Dr Geddes' perception thread was split into 4)
dave
gedlee said:
Sounds like Dave may move these back to the other thread - that's cool.
Sorry I was vague. I didn't mean to imply crossovers for other drivers. Yes, horn, crossover, spec'd drivers, spec'd box dimensions, ala Linkwitz. If you can get a deal on the drivers, that's good. Maybe you can get the same deal and have them drop shipped, at least other than continental North America. The less you have to handle, the better I would think. Maybe start in N.A., see how it goes, then find a small shop in the EU to mnf under license, if there is enough interest.
Sheldon
MJL21193 said:
That's true but the assumption I made was that had you done such a comparison you would have at least alluded to it rather than take the stance you did. I'm not Sherlock but...
It wasn't nasty, it was disrespectful, a cheap shot. I will let the other mods decide now that I am a part of this thread.
I was referring only to a direct comparison of two boxes. Not suggesting nor questioning anything else of your knowledge or experience.
EDIT: Grammar
Sheldon said:
As long as he doesn't move them to the "dome tweeter" argument. I'm not going to give that credibility by responding.
I have a basic agreement from B&C that I can have the drivers shipped anywhere in the world and they will find the local distributor and have them sent locally. The prices can be quite a bit higher in places like Asia, but it does keep the shipping down.
As far as other people doing things, like in the EU, everything adds cost, another layer another 25-50%. I was disgusted to learn today that the biggest company in the world is now a retailer - a non-value-added producer of services (not goods). Used to be the top ten companies all "made" things. Took raw materials and made useful products out of them. Now its not the products that make money anymore, its the companies that dispense those products. The manufacturers are now all in China. We are becoming a society of consumers who produce next to nothing.
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