Tom Mobley Posted January 7, 2004 Share Posted January 7, 2004 this is interesting: driver calcs any good, Al? the Le calc? or this: more driver calcs Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 7, 2004 Share Posted January 7, 2004 Hmpf. I've got a feeling these simple measurements are not what Al is after. I mean, he would already have done this himself, right? Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 7, 2004 Share Posted January 7, 2004 Tom, My latest thing is to design the woofer filter with an inductor at the output that exactly matches the voice coil inductance of the woofer. The link given earlier shows the basic idea of how to measure it but it gives an equation I have never seen for Le. I don't trust it anyhow. The actual inductance is different at every frequency. I want to know what it is at the exact frequency of the crossover for the stock K33 driver in a stock Khorn. I have the plot for the woofer in a Belle done with a fancy analyzer and an impedance bridge. I'm pretty sure the Khorn is similar, but I want to be sure. Without the fancy analyzer, the only way I know to measure it is by resonating the entire woofer with a known value of capacity. Once I know the frequency of resonance it's easy to calculate the inductance. The attached graphic shows the setup. The capacitor Cx has to be chosen such that the straight line on the scope (like box FM) happens as close to the 400 Hz crossover as possible. Once I know what value of Cx causes the straight line on the scope at 400 Hz I can calculate the voice coil inductance of the woofer at 400 Hz. The inductance is about 1 mHy, so value of Cx should be roughly 160 uFd. The only detail not shown is that you need to first connect a 10 Ohm resistor in place of the speaker and Cx just like the earlier link shows. You adjust the oscillator output so you get exactly .1V (or some multiple of 10) on the AC Voltmeter. This makes the meter read directly in Ohms. When you connect the speaker and Cx in place of the resistor, the meter will then indicate the resistive component of the woofer impedance when the scope shows a straight line. This is about 6 Ohms in the Belle Klipsch and becomes the design impedance of the filter. The impedance plot at the bottom of the graphic illustrates tuning a port for an open port enclosure. With the capacitor (Cx) in the circuit, the curve will be a very broad dip at 400 Hz. Al K. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 7, 2004 Share Posted January 7, 2004 Al, I have to work 12hrs/day for the next 3 days, after that I could try to do this. I have a scope that works, a Fluke with a frequency counter, an audio generator, some other stuff. These are the main tools needed, right? I would need to pull a K-33 out of one of my LaScalas, mount it in place of the Jensen in one of the KHorns, do the thing laid out in the graphic, right? This would be done with speaker fully assembled, in the corner, so I would have minor logistical issues with wiring, right? I could try it, but I might need some hand-holding at some point. Would it be better to try it Monday when I can get hold of you at work? Tom Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 8, 2004 Share Posted January 8, 2004 Tom, Yes, I think the equipment you have will do it. I do need the data on the K33 driver since I will be designing for the "stock" Khorn. You might want to do it with the driver you are using just for you own info though. BTW, are you aware of the "restrited throat" of the Khorn. It's optimized for the K33. Changing to other drivers is usually a step backward. Are you sure the one you are using is right? Thanks, Al K. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted January 8, 2004 Share Posted January 8, 2004 Tom, In about the vintage of your Khorns Klipsch made some changes to the bass bin. One thing I've read is the tuning slot width was changed. And, I thing, a slight demensional change was made to the first section of the split horn. It might behoove you to measure the woofer slot opening when you put in the K33 to accertain which Khorns your measurements apply to. Does anyone know exactly when the changes were applied? If they were a running change in mid-year what was the serial number cutoff? Rick Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 8, 2004 Share Posted January 8, 2004 Al, my Khorns were made in late 59 or early 60, they were still using Jensen woofers then. I haven't had one out yet but I'm guessing they have the 3 x 13" slot. I believe the 6 x 13" went away when they switched from the Stephens Tru-Sonic woofers to the Jensen. Rick- I haven't previously heard about changes to the bass horn structure except for the openings that changed the back chamber volume. I was under the impression that that change was later. Tom Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 8, 2004 Share Posted January 8, 2004 Tom, I take it that the two different woofer drivers you have there are BOTH stock drivers. That complicates things! I guess I need Ls measurements on both. That hight require two different designs to accomodate the two drivers or a compromise between the two if they are close. I think there is variation in production losts anyhow. That would justify designing to some mean values. Al K. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 8, 2004 Share Posted January 8, 2004 Al, AFAIK, designing to the K-33 would probably cover at least 90% of existing KHorns. The early variations are rare, IMO, and their owners probably more interested in originality that replacing working parts. I'll pull a woofer, see if I have the 3x13" slot, if so then use the K-33 out of one of my LaScalas to try this. And I do think that production variations justify some generic-izing. It would be past idealistic to assume that all those batches of K-33 are all the same. I understand that there's been several different manufacturers of these over the years. Tom Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 8, 2004 Share Posted January 8, 2004 Tom, I think your are right about even true K33s might be different from batch to batch. Of my 3 Belles, my older set measures 6 Ohms in sereis with 1 mHy. My center Belle, which is 10 years newer, measures closer to 7.5 Ohms in sereis with 1 mHy. Since the newer one was bought used, I really can't swear that is hasn't been reconed or somethihng though. Those measurements are from rectangular impedance (R +-jX) Not simple impedance. The simple impedance is 7.5 Ohms and 9 Ohms at 700 Hz. Al K. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 13, 2004 Share Posted January 13, 2004 Al, I'm sorry to say I'm just not going to have a chance to do this on this set of days off. I'm just bombed with stuff, home and family. Yep, I'm over-committed right now. I'm willing to try again next days off if you don't find anybody else to do it first. I work 12 hour days, 3 days one week and 4 the next. This current Sun, Mon, and Tues are my short weekend, I'll go back to work Wed, Thurs, Fri and Sat, then have four days off. I should be able to get to it then. Sorry to let you down, but I got hit with unexpected stuff this time. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 13, 2004 Share Posted January 13, 2004 Tom, Ok.. I'm sure the tests will get done someday! Thanks, Al K. Quote Link to comment Share on other sites More sharing options...
sfogg Posted January 13, 2004 Share Posted January 13, 2004 Al, I'm waiting for the software to arrive but I ended up buying dual channel FFT software that can do transfer functions between the channels that claims to plot magnitude and phase. So hopefully I can use that with the bridge to do the complex impedance. It also has a built in impedance measurement function but I think that is doing a more basic impedance measurement and I know it doesn't show phase changes. That is explained in the manual here: http://www.dr-jordan-design.com/Download/WinAudioMLS.pdf It will be a little more difficult to use as the input voltage will have to be calibrated with the software but it should work. I ended up ordering WinMLS Pro EX. He was selling the PRO version on e-bay (which is normally $250 but I got it for $30 on ebay direct from the developer) and then upgraded it to the dual channel version for $103. Hopefully I can do everything I want with it instead of using the SD380. On the plus side the software has a better dynamic range and can also THD, THD+N, IMD and all sorts of other things too. Biggest downside is the lack of built in voltage calibration and also the limited input voltages available into the sound card itself. Shawn Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 13, 2004 Share Posted January 13, 2004 Shawn, Ok.. I will be interested to know how that software program performs compared to the SD380 or my SD375. I find it hard to believe it can do all that good stuff, but I am a fugative of 1970s thinking! Tom, I think I have found a guy that can do the "Le" tests on the Khorn for me. I have know the guy for a while but I didn't know he had Khorns. Somehow I thought he had Cornwalls! Anyhow, he is well qualified and equiped to do it. Al K. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted January 16, 2004 Share Posted January 16, 2004 RickTTT Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 19, 2004 Share Posted January 19, 2004 Al, sounds good 'cause I would be fumbling in the dark any. Also, my real life family just co-opted most all of the time I had these days off. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted February 29, 2004 Share Posted February 29, 2004 ttt Quote Link to comment Share on other sites More sharing options...
Deang Posted February 29, 2004 Share Posted February 29, 2004 Damn. A killer thread. Enough for me to chew on for the next month. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted February 29, 2004 Share Posted February 29, 2004 Dean, You've got your brown belt in xovers. Now you must work with X Master Al to earn your black belt! Rick Quote Link to comment Share on other sites More sharing options...
3dzapper Posted February 29, 2004 Share Posted February 29, 2004 Dean, You've got your brown belt in xovers. Now you must work with X Master Al to earn your black belt! Rick Quote Link to comment Share on other sites More sharing options...
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