BEC Posted December 7, 2004 Author Share Posted December 7, 2004 ---------------- On 12/7/2004 6:43:44 PM D-MAN wrote: ---------------- On 12/7/2004 6:16:53 PM John Warren wrote: He is attempting to determine Vas. ---------------- Somebody please SPLAIN this to me! How does this work? DM ---------------- DM Then, knowing Vas, we can calculate electro-acoustic efficiency. Just working my way through all of it as I have the time to work on it. Bob Quote Link to comment Share on other sites More sharing options...
Dylanl Posted December 8, 2004 Share Posted December 8, 2004 Test air tightness by blowing air from a compressor & (air nozzel) into the box, listen for leaks. Fill leaks with wood glue or epoxy. Use plexiglass and a seal to cover the driver opening. Quote Link to comment Share on other sites More sharing options...
BEC Posted December 19, 2004 Author Share Posted December 19, 2004 Here we go with some results of TS testing on some K-33E woofers. Included here are tests on one new fresh K-33E with round magnet and two K-33Es with square magnets from 1974 Khorns. One thing to point out on these woofers is that the old ones weigh a couple of pounds more than the new ones. That extra weight in the old ones seems to be all in the magnet assembly. We should remember that this is a small sample of the two types of K-33Es tested. It would be better to have a larger number tested to build confidence in the data. Thanks to John Warren for his assistance. Bob Crites TStestK33.pdf Quote Link to comment Share on other sites More sharing options...
Dylanl Posted December 19, 2004 Share Posted December 19, 2004 So Bob, explain what this means in sound reproduction? Did you get the other 2 sqare K33s from Joseph? That would give you more to test. Quote Link to comment Share on other sites More sharing options...
BEC Posted December 19, 2004 Author Share Posted December 19, 2004 I think I will be getting some from Joe. I am not really the best one on the forum to comment on the results. We can all see that Fs is different between the old and new woofers with the old ones going quite a bit lower. Bob Quote Link to comment Share on other sites More sharing options...
IB Slammin Posted December 19, 2004 Share Posted December 19, 2004 ---------------- On 12/19/2004 2:54:51 PM BEC wrote: I think I will be getting some from Joe. I am not really the best one on the forum to comment on the results. We can all see that Fs is different between the old and new woofers with the old ones going quite a bit lower. Bob ---------------- Bob, I wonder why the difference in the Fs is +/- twice as much in air as in the box? (did I say that right?) Regards, Terry Quote Link to comment Share on other sites More sharing options...
BEC Posted December 19, 2004 Author Share Posted December 19, 2004 Terry, The best answer might be "I don't know". I think though it would depend on the sealed volume of the box. Bob Quote Link to comment Share on other sites More sharing options...
IB Slammin Posted December 19, 2004 Share Posted December 19, 2004 ---------------- On 12/19/2004 3:32:54 PM BEC wrote: Terry, The best answer might be "I don't know". I think though it would depend on the sealed volume of the box. Bob ---------------- This is probably a dumb question. They were all tested in the same sealed box. Right? It seems odd to me that 01 & O2 had a difference of 8.45 to N1 in open air, but only 3.55 in the enclosure. I would expect the ratio to be the same or at least closer. (maybe I said it better this time) Terry Quote Link to comment Share on other sites More sharing options...
BEC Posted December 19, 2004 Author Share Posted December 19, 2004 Terry, I would guess that the resonate frequency of the old and new are affected differently by the sealed box. Bob Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted December 19, 2004 Share Posted December 19, 2004 I guess now that the testing hardware and equipment are up to speed, now we need to harness the power of statistics to calculate the standard deviation and mean for some of the critical measurements. It occured to me from IU busines E270 (statistics for business) that N>= 30 for any meaningful stats for a test. In other words the number of units to be tested needs to exceed 30 before any true number crunching can take place with any degree of certainty. This helps to account for test units that are far out on the bell curve from the mean in any measurement. It seemed that no matter how large the population size (ie how many E33 woofers are out there) the sample size only needed to exceed the 30 criterion. Will look into the math of this more if you wish. Michael Quote Link to comment Share on other sites More sharing options...
Deang Posted December 20, 2004 Share Posted December 20, 2004 Bob, I wonder why the difference in the Fs is +/- twice as much in air as in the box? (did I say that right?) What it looks to me is that the new driver isn't really a "K-33" at all. Not only does it "look" like a different driver, but it even behaves like a different driver. Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted December 20, 2004 Share Posted December 20, 2004 I'm wondering if a particular current production Emminence woofer could be identified as closer to the old K33. Or the new one for that matter. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted December 21, 2004 Share Posted December 21, 2004 I'm with Dean. Looks like the older driver is "better." What's the significance of all this? We ought to get Gil, John and Dennis to weigh in on this. Quote Link to comment Share on other sites More sharing options...
John Warren Posted December 21, 2004 Share Posted December 21, 2004 When Bob sent the numbers to me is was surprised to see the higher Fs on the new, rd. magnet driver. I've measured 8 K33E sq. magnets and not one of them was above 28Hz. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> I'm thinking out loud here. Bob says the new, rd motors are lighter than the older sq. so we should assume that the new structures have less magnet material which would account for the higher Qes number (Qes is inversely proprotional to the sq of the gap flux density). Note too, the electro acoustic efficiency, n, is similar to the larger sq. motor so even though the gap strength is lower, the acoustic ouput is similar. Look at the expression for n: n = 9.67x10-10 Fs3 Vas / Qes. It shows that to maintain a fixed n, an important criteria for interchangability between old and new K33Es, we can adjust Fs, Vas and Qes. So if Qes goes up because we shaved 2lbs of magnet material off the motor, the product (Fs3 Vas) can be adjusted to compensate. If Qes goes up, Fs must go up since Vas is inversely proprotional to Fs. Is it audible? The whole point of a horn is to increase the radiation resistance presented to the cone. As frequency is lowered, at what frequency does the horn begin to "unload" the driver. For the Klipschorn I think that frequency is around 50Hz. Since a cone driver no longer "works" below its Fs, the relationship between the cone Fs to the unload frequency determines the horn roll-off. My geuss is that testing showed the increase in Fs to be inaudible. Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted December 21, 2004 Share Posted December 21, 2004 John, In the scenario of replacing an old K33 in a Cornwall cab... would you think the the different K33's would make much of an audible difference? Quote Link to comment Share on other sites More sharing options...
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