Yes, full-range open baffle with woofers under 100Hz = ideal! 😉
(And then you can play around with cardboard for the baffle)
I think "how low can you go" depends entirely on the resonant frequency of the material used for the cabinet.
Doesn't a simple variable volume MDF box solve the problem? You'd only have to build it once, and your testing results would be very accurate compared to the final box.
Doesn't a simple variable volume MDF box solve the problem? You'd only have to build it once, and your testing results would be very accurate compared to the final box.
Yes, I would agree completely. However, after reading through this forum and others for the last six months, it occured to me that a lot of people are building speakers in their living rooms and spending an enormous amount of time and energy to come up with something they know nothing about how it will sound.
I think this is the Achilles heel of DIY speakers. So I asked myself is there a better way. Surprisingly, I found very little on prototyping speakers.
So now this thread has come full circle. There's a lot of great information so far. My goal of this thread is to bring out what experience is out there (if any). You don't buy the car to test drive it, do you?
I guess the question now is:
Can one throw something on the living room floor with a straight edge, tape, and sharp knife, etc., and build something in an afternoon that will tell one what they need to know, which is, will this work for me?
So far, it appears that cardboard is okay for open baffles. Bass response is suspect in non-wood prototypes. Laminating cardboard works. Foam can sound as good as wood. Forget trying this on subwoofers. This is all knowledge I did not have last week.
Doug
Taperwood said:
Hmm, this is what Thiele/Small parameters and programs like WinISD and Unibox are for. (which are free for the DIY guy). They will tell you a lot more than a make shift floppy box.
I don't want to sound standoffish because I know you are sincere, but how are parameters and software going to tell me what something sounds like in a certain room until I actually build it? Numbers and squiggly lines can only do so much. I'm asking about the next step, when you need to build something.
In my woodworking, I have learned to always build prototypes. I used to hate it, thinking it was wasted time, but now I know better. My pile of unfinished projects in very expensive wood is a testament to that learning.
Doug
In my woodworking, I have learned to always build prototypes. I used to hate it, thinking it was wasted time, but now I know better. My pile of unfinished projects in very expensive wood is a testament to that learning.
Doug
I think you might find similar problems with a foam or cardboard prototype, in that it won't give you a very good representation of the final sound of a wood enclosure. The enclosure is, as you know, a critical component of the speaker, and it's resonances at across the frequency range (not just low bass) affect the final wave form (resonances, harmonics, difraction, absorbsion, etc).
I think the software will give you a good idea of how a speaker will behave generally, and a foam/cardboard prototype might extend that a little, but you really won't know how the speaker will sound until you have the final cabinet, or something as close as possible to it.
Again, we come full circle. Can a speaker be prototyped without a lot of construction work? Yes, but prototypes are just that, and will never be a true representation of the final.
I think the software will give you a good idea of how a speaker will behave generally, and a foam/cardboard prototype might extend that a little, but you really won't know how the speaker will sound until you have the final cabinet, or something as close as possible to it.
Again, we come full circle. Can a speaker be prototyped without a lot of construction work? Yes, but prototypes are just that, and will never be a true representation of the final.
This is all very interesting and, frankly, a bit surprising. I thought, Oh, DIY speakers, there should be tons of stories and experience on prototyping. But I guess not. I'm old enough to know that I am the one missing something here, not everyone else. I will defer to the collected experience and wisdom of this forum and not pursue this any further.
However, since I'm a guy, I will prove to myself the nature of prototyping speakers. My next project will be a Fostex full range speaker. I will build at least three prototypes: Fostex's horn design and bass reflex design, and an open baffle. I think I will use foam this time. I expect this to take eight hours and cost about $40. Heck, I may even grab a garbage can lid and some chicken wire and paper mache' and make one of those big round horns and stick the driver in that, just to see what that sounds like.
Doug
However, since I'm a guy, I will prove to myself the nature of prototyping speakers. My next project will be a Fostex full range speaker. I will build at least three prototypes: Fostex's horn design and bass reflex design, and an open baffle. I think I will use foam this time. I expect this to take eight hours and cost about $40. Heck, I may even grab a garbage can lid and some chicken wire and paper mache' and make one of those big round horns and stick the driver in that, just to see what that sounds like.
Doug
You might be surprised by what you can do without wood... you just need to understand the tradeoffs.
For example, if you made your horn out of chicken wire and something more like what they make casts (for broken bones) from, I think you could get superior sound. I saw someone's website where they made a front-horn out of a huge block of styrofoam (actually, sheets stacked up, but it was solid), and it was supposed to sound fairly good. Ditching wood and using more accessible construction techniques can be made to work quite well, if it's done right.
I'd really like to see anything you do that's non-wood. I think that what people are really saying here is that with this hobby you tend to get out of it what you put into it. Carefully considered and constructed enclosures that take into account real material properties will almost always beat the prototype.
That said, good luck on the prototypes!
Joe
For example, if you made your horn out of chicken wire and something more like what they make casts (for broken bones) from, I think you could get superior sound. I saw someone's website where they made a front-horn out of a huge block of styrofoam (actually, sheets stacked up, but it was solid), and it was supposed to sound fairly good. Ditching wood and using more accessible construction techniques can be made to work quite well, if it's done right.
I'd really like to see anything you do that's non-wood. I think that what people are really saying here is that with this hobby you tend to get out of it what you put into it. Carefully considered and constructed enclosures that take into account real material properties will almost always beat the prototype.
That said, good luck on the prototypes!
Joe
Whilst doing some research on horns I found this info, and thought it may be pertinent:
To construct the mid horns, I layed out a full size template using AutoCAD. I then took a material called Moldboard or Renboard. This is a compressed paper substance used for prototype work in the vacuforming industry. It looks like MDF, and is almost as dense, but the color of cardboard. It has 3 big advantages: it machines like butter, it is cheap, and it is porous to air, meaning vacuum pulls right through it. So, what I did was stack up rough cut circles of the approximate diameter using 1.5" thick material, stick it into a Bridgeport mill, and start cutting. 30 or 40 hours later, I had a mold, perfect to the tractrix curve using the template I made to check it.
To construct the mid horns, I layed out a full size template using AutoCAD. I then took a material called Moldboard or Renboard. This is a compressed paper substance used for prototype work in the vacuforming industry. It looks like MDF, and is almost as dense, but the color of cardboard. It has 3 big advantages: it machines like butter, it is cheap, and it is porous to air, meaning vacuum pulls right through it. So, what I did was stack up rough cut circles of the approximate diameter using 1.5" thick material, stick it into a Bridgeport mill, and start cutting. 30 or 40 hours later, I had a mold, perfect to the tractrix curve using the template I made to check it.
Thanks Matt, that stuff sound really cool. I will keep it in mind. I love curves and would prefer to build speakers using them, but right now I think I will concentrate on more traditional designs until I get some more experience.
I think now, in my open baffle part of my prototypes, I will try two versions, a traditional I_I form and a U, just to see what the difference is. In foam, it should be quite easy.
Doug
I think now, in my open baffle part of my prototypes, I will try two versions, a traditional I_I form and a U, just to see what the difference is. In foam, it should be quite easy.
Doug
You know, after reading through more posts, it seems to me that the reason for making a prototype is not really clear. In it's most common form, it is only one part of the process towards a final result. It should be part of the learning process and not be an end in itself.
This process, even in the simplest of projects, often takes the sequence: Idea, research, design, modeling, engineering, prototype, testing, re-engineering, pre-production prototype, process engineering, production run. The important part is not the prototype, but the testing that determines what kind and how much re-engineering is required.
Sometimes, it is not possible to make a prototype in a material or form that is different than that of a production model. Sometimes, it is. The reason I suggest multiple layers of cardboard, it that I believe it has a chance of approximating the characteristics of MDF or some exotic hardwood that a final speaker model would be made of. To use a significantly different material would only make your re-engineering impossible, or at very very difficult.
If what you want is the sound of MDF, then your prototype should take that into account. If you believe that cardboard, foam or any composite of materials will satisfy that constraint, then go that route. If you don't, then you are actually wasting your time and resources by doing it. If you are merely trying to save time and/or money, don't bother with the prototype and use established materials and methods to build your speaker.
🙂ensen.
This process, even in the simplest of projects, often takes the sequence: Idea, research, design, modeling, engineering, prototype, testing, re-engineering, pre-production prototype, process engineering, production run. The important part is not the prototype, but the testing that determines what kind and how much re-engineering is required.
Sometimes, it is not possible to make a prototype in a material or form that is different than that of a production model. Sometimes, it is. The reason I suggest multiple layers of cardboard, it that I believe it has a chance of approximating the characteristics of MDF or some exotic hardwood that a final speaker model would be made of. To use a significantly different material would only make your re-engineering impossible, or at very very difficult.
If what you want is the sound of MDF, then your prototype should take that into account. If you believe that cardboard, foam or any composite of materials will satisfy that constraint, then go that route. If you don't, then you are actually wasting your time and resources by doing it. If you are merely trying to save time and/or money, don't bother with the prototype and use established materials and methods to build your speaker.
🙂ensen.
Thank you, that was very well said.
In my mind, the prototyping process is not to determine the final sound but the direction the sound is taking. In essence, how does it change with each generation of prototype? Better or worse? I am assuming that if one uses the same material throughout the process, you would come to a point where changes affected the sound very little. At that point, if you decide to continue, you can build with wood knowing that your design is as good as it can be without starting from scratch.
Given the maturity of speaker technology and the wealth of experience on this forum and around the net, I don't think that more than a couple of prototypes would need to be built to finalize any design. Which should be a very comforting thought. I mean, we're not building rockets here.
Also, the first prototypes give one an excellent sense of proportion and aesthetics. It's one thing to see a photograph or have a mental picture, but until you see something in three dimensions and can walk around it and show it to others, you really don't know how something will look. Often, for furniture, at that stage I will use thin sticks hot glued together and brown wrapping paper taped over them. Very quick and dirty, but it has saved me a fortune in time and money and materials.
I wholeheartedly agree that prototyping is not a faster way to build something. My original question was is there a material that I could use to build speaker prototypes faster and cheaper. If the answer turns out to be no, then I will have to build them the harder and more expensive way, but I will always be wondering if I have missed something.
Doug
In my mind, the prototyping process is not to determine the final sound but the direction the sound is taking. In essence, how does it change with each generation of prototype? Better or worse? I am assuming that if one uses the same material throughout the process, you would come to a point where changes affected the sound very little. At that point, if you decide to continue, you can build with wood knowing that your design is as good as it can be without starting from scratch.
Given the maturity of speaker technology and the wealth of experience on this forum and around the net, I don't think that more than a couple of prototypes would need to be built to finalize any design. Which should be a very comforting thought. I mean, we're not building rockets here.
Also, the first prototypes give one an excellent sense of proportion and aesthetics. It's one thing to see a photograph or have a mental picture, but until you see something in three dimensions and can walk around it and show it to others, you really don't know how something will look. Often, for furniture, at that stage I will use thin sticks hot glued together and brown wrapping paper taped over them. Very quick and dirty, but it has saved me a fortune in time and money and materials.
I wholeheartedly agree that prototyping is not a faster way to build something. My original question was is there a material that I could use to build speaker prototypes faster and cheaper. If the answer turns out to be no, then I will have to build them the harder and more expensive way, but I will always be wondering if I have missed something.
Doug
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