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I'd like to build a pair of Pi-aligned cabinets for my newly-acquired pair of Goodmans Axiom 201 12" extended-range drivers. As a first step (and also just as a learning exercise), I'd like to measure the T-S parameters of my particular pair of 201's. I have all of the information I need to get started except: How should I calculate a reasonable volume for the closed box I will use to measure Vas? The Readme.txt file contained in PiAlign.zip says, "The test box should be 0.5 - 2.0 of the expected Vad, which can be approximated using the ratio method described above." I may be misreading the Readme.txt document somehow-- because I can't spot the ratio method for approximating the expected Vad. Can you help me out? Thanks very much, -uW
See the post called "T/S Measurements". <br(.*)
I have a number of papers by Pat Snyder of Speakelab (from some years back) in which he talks about this. He showed that even though individual samples will vary somewhat due to the manufacturing process, this causes some of the T/S parameters to vary in such a way that in the end, the effects cancel out. In a given box, ported the same way, the woofers of a given model will perform very similarly even though Vas, Fs, etc may vary slightly. He stated that what really mattered were the ratios of various T/S parameters. And even though T/S numbers varied from sample to sample, they varied in such a way that these ratios were the same.
Thanks, Wayne. I have just finished a careful read-through of that whole thread. I'm sure I'm being obtuse, but: I still don't know how to choose the volume of the sealed box to use for the sealed-box-method Vas test. Is the box volume fairly arbitrary, as long as it is precisely known? Thanks for your patience, -uW
Re: What volume box for sealed-box test?
The box size is arbitrary. Make a box of convenient size and it will work just fine.