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#1
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convert Thiel-Small parameters to optimum enclosure volume, & vice-versa?
Is there a straightahead method for determining the optimum volume for
a loudspeaker enclosure based on a particular driver's Thiel-Small parameters? And conversely, is there a way to determine the optimum Thiel-Small parameters (or, really, to select an appropriate driver) based on an existing enclosure's volume & port size? And is there a way to determine how a given driver will perform in a given enclosure if you have all that information? Thanks. |
#2
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Though this same set of questions was posted in rec.audio.tech
several days ago, I'm responding to the questions here as well. Roscoe East wrote: Is there a straightahead method for determining the optimum volume for a loudspeaker enclosure based on a particular driver's Thiel-Small parameters? Yes, if you are willing to define what you mean by "optimum." The problem being is that optimum is a multi-dimensional system. For example, does optimum mean maximum bandwidth, flattest response, greatest low frequency excursion limited output, best transient response, smallest size and so forth? Or some combination thereof? Which performance parameter(s) are you willing to compromise to optimize some other parameter(s)? You may answer "I want maximally flat (Butterworth) response" as "optimum," and then learn that the driver you have simply can't get you there in ANY enclosure. Another driver might get you there, but at significant cost, for example, a driver with a Qts of 0.2 COULD be used in a maximally flat, sealed box system, to be sure, but you'd end up with a very efficient system with a very high cutoff frequency, most likely. After you spent all that money on this driver with it's big magnet, you might be justified in concluding that a sealed box system is not an "optimal" design. And conversely, is there a way to determine the optimum Thiel-Small parameters (or, really, to select an appropriate driver) based on an existing enclosure's volume & port size? Again, if you can answer the question I posed above, the answer is yes. And is there a way to determine how a given driver will perform in a given enclosure if you have all that information? Yes, to a very great extent, especially in the so-called "piston band" region of operation. |
#3
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wrote:
Though this same set of questions was posted in rec.audio.tech several days ago, I'm responding to the questions here as well. Roscoe East wrote: Is there a straightahead method for determining the optimum volume for a loudspeaker enclosure based on a particular driver's Thiel-Small parameters? Yes, if you are willing to define what you mean by "optimum." The problem being is that optimum is a multi-dimensional system. For example, does optimum mean maximum bandwidth, flattest response, greatest low frequency excursion limited output, best transient response, smallest size and so forth? Or some combination thereof? Which performance parameter(s) are you willing to compromise to optimize some other parameter(s)? I would have defined "optimum" as "the best balance between all those parameters" but I do see your point, that trade-offs among those parameters are preferential and so leave a lot of leeway. Is there a direct formula or simple rule of thumb for translating T-S parameters to "optimum" dimensions for each of the qualities you describe? And conversely, is there a way to determine the optimum Thiel-Small parameters (or, really, to select an appropriate driver) based on an existing enclosure's volume & port size? Again, if you can answer the question I posed above, the answer is yes. Okay, see my answer (above). Now how do I go about determining what those sonic variables will be based on the information I have at hand (in this case, existing enclosure's volume & port size)? And is there a way to determine how a given driver will perform in a given enclosure if you have all that information? Yes, to a very great extent, especially in the so-called "piston band" region of operation. I didn't realize I had posed a Yes or No question! Allow me to rephrase: How does one go about determining how a given driver will perform in a given enclosure, assuming one knows the different driver's T-S parameters & the candidate enclosure's dimensions? Thanks. |
#4
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Roscoe,
Get yourself a copy of Vance Dickenson's Loudspeaker Cookbook. It's a very good book that explains alot in practical terms in a way almost anyone can understand. You will have to invest some time and devotion in to its content, but after some days with this book you could probably explain to us here the very answers to your questions. Enjoy the search, Wessel |
#5
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Roscoe East wrote:
Is there a straightahead method for determining the optimum volume for a loudspeaker enclosure based on a particular driver's Thiel-Small parameters? Yes, if you are willing to define what you mean by "optimum." I would have defined "optimum" as "the best balance between all those parameters" but I do see your point, that trade-offs among those parameters are preferential and so leave a lot of leeway. Fine, define what the "best balance" is between low-frequency cutoff, power handling and response smoothness. What might be "best" for you might not be for someone else. For example, if you were a client of mine looking to design a system, I would try to convince you that trading increased power handling for bass extension is "best" because it will reduce after-sales support costs. Is there a direct formula or simple rule of thumb for translating T-S parameters to "optimum" dimensions for each of the qualities you describe? No, there is not. There are approximate equations, but the especially in the case of vented systems, there are no closed- form equations that get you there. One finds procedures such as "find the largest positive real roots of this 4th order equation and then ..." And is there a way to determine how a given driver will perform in a given enclosure if you have all that information? Yes, to a very great extent, especially in the so-called "piston band" region of operation. I didn't realize I had posed a Yes or No question! Well, here's your question: "is there a way to determine how a given driver will perform in a given enclosure if you have all that information?" Sure looks like something requiring a yes or no question to me! :-) Allow me to rephrase: How does one go about determining how a given driver will perform in a given enclosure, assuming one knows the different driver's T-S parameters & the candidate enclosure's dimensions? Thanks. One finds the appropriate formulae, takes the appropriately scaled parameters and solves the formulae. That was done in detail in Small's work in the early 70's and has been amplified upon by any number of people. Several, including myself, have gone so far as to encode various forms of those formulae and their derivatives into programs that one can use. I might suggest that you explore them internet for any number of inexpensive or (even) free modeling packages for this purpose. Someone else suggested Dickason's work, which while not the best in terms of an exposition of the underlying theory, does, like a cookbook, getr you to the point of eating fairly quickly, even if youm don't understand WHY you cooked the meal that way. |
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