Deang Posted November 17, 2004 Share Posted November 17, 2004 Can the ALK be used with the K-55-M? The second question involves something I don't think we ever had complete resolution on. Does changing to different taps on the autotransformer move the crossover points. Bob says "no", John W. says "yes", Al and John A. haven't weighed in -- and based on everything said so far, I'm inclined to agree with Warren -- as long as I don't look at BEC's graphs. Quote Link to comment Share on other sites More sharing options...
D-MAN Posted November 18, 2004 Share Posted November 18, 2004 I'll weigh in here, having ALK's and a non-Klipsch top-end, so my opinion will probably just as misleading as anybody's... I doubt that you could actually hear a difference as to where the crossover point occurred with a K-55-M on the network. I've found the ALK to be very accepting of various driver and horn changes with absolutely no ill effects whatsoever. For instance, I am running a K33E, an 2" mid-driver (8 Ohm) on a non-Klipsch horn, and JBL tweeters. Sounds great! Any change in the overall reactance (varying impedance) caused by different drivers and/or different horns (which all have a throat impedance) "seen" by the network will change the crossover point slightly, but in the case of the high-end, the changes are less than, say, putting an 8 Ohm woofer (vs. the nominal 4 Ohm K33) in a Khorn bin which alters the crossover point a little more noticably. The mid and high frequency crossover points seem to be less effected by driver/horn changes than a woofer change, IMO. DM Quote Link to comment Share on other sites More sharing options...
BEC Posted November 18, 2004 Share Posted November 18, 2004 ---------------- On 11/17/2004 11:52:25 PM DeanG wrote: Can the ALK be used with the K-55-M? The second question involves something I don't think we ever had complete resolution on. Does changing to different taps on the autotransformer move the crossover points. Bob says "no", John W. says "yes", Al and John A. haven't weighed in -- and based on everything said so far, I'm inclined to agree with Warren -- as long as I don't look at BEC's graphs. ---------------- Dean, I would agree that it moves. It just looked to me in my testing to be rather insignificant. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 18, 2004 Share Posted November 18, 2004 Guys, My network will work with virtually any squawker driver so long as the efficiency is in the same general range as the K55. It can even be 8 Ohms. Since most all are, the K55M certianly can be used. The K55V and K55M have IDENTICAL efficiency. Moving the transformer taps DOES move the crossover slightly, but ONLY slightly. Al K. Quote Link to comment Share on other sites More sharing options...
JohnA Posted November 18, 2004 Share Posted November 18, 2004 O.K., I'll weigh in. In Al K's crossover design and others similar to it the crossover point (-3 dB point) may move, but it will be insignificant. With Klipsch' normal designs, moving the tap on the autoformer moves the crossover point theoretically an octave. Since the autoformer is not perfect and has pure resistance, the actual change will be something less than a full octave. Quote Link to comment Share on other sites More sharing options...
Deang Posted November 18, 2004 Author Share Posted November 18, 2004 A full octave is quite a bit. John Warren says you have to take the 13uF cap in the A & AA to 6.5uF when you drop to the #3 tap -- to keep the crossover point the same. Opinions? In another thread, Dennis said, "When you move the midrange down one tap you should add a 15R/10W resistor in parallel with the driver to keep the crossover point the same." I'm having trouble correlating Dennis' statement above to John W's about halving the capacitance. Quote Link to comment Share on other sites More sharing options...
jwc Posted November 18, 2004 Share Posted November 18, 2004 Great Discussion. I can't offer any technical input. However, I am a case in point. I have a pair of 84" La Scalas w/ AL networks in great condition. I will make an upgrade soon. Dean emailed me to ask what Mid was in my scala. Stupid me, I never looked. At any rate, it is a K-55-M, not a K-55-V. I too am interested on your opinions of this matter. Is the ALK the right upgrade? Is the K-55-M in need of a Type A or AA like network or more like the later Networks (ie AL-3). The above language in this thread is well over my head but I do have a picky ear for audio. Quote Link to comment Share on other sites More sharing options...
Deang Posted November 18, 2004 Author Share Posted November 18, 2004 Well, Al says the ALK works with the K-55-M. I realized after he answered that what I was actually thinking about was the incompatibility of the Cornwall ALK with the later Cornwall II -- because of the different tweeters. I think it's time I start keeping a notebook on all this stuff, because I apparently don't have the capacity to remember it all. It would be nice to nail down this 'tap' issue, because it comes up all the time, both on the forum and in emails I get. We have folks that like to move down to the #3 tap in the A and AA, down to #1 with the Heresy -- as well as those who move to the different taps on the ALKs. It would be nice to have something definitive to tell people. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted November 18, 2004 Share Posted November 18, 2004 Dean, you need several notebooks and trousers that are too large with the waist altered to fit so you can carry them and everything else in your pockets. Maybe a pair of watches would help too. Rick Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted November 18, 2004 Share Posted November 18, 2004 I've been using the #3 tap for the K55 since we were discussing this in a thread some months ago and absolutely love the change, IMO improvement in the way my Khorns sound. One little bit of research I did, can't remember the numbers, but looked up some Atlas stuff and found out that even if the #3 tap lowers the crossover freq. it's no prob for the K55. Klipsch doesn't utilize it anywhere near what it's capable of in lower freq. Quote Link to comment Share on other sites More sharing options...
WMcD Posted November 18, 2004 Share Posted November 18, 2004 Everyone is pretty much correct. If we use a classic 6 dB per octave high pass we need a certain sized (value) capacitor. You have to do the math but its reactance is equal to the load at the crossover frequency. And Xc = 1/(2 pi F C). (Phase angle goes to 45 degrees for the power industry people.) If you double the load in ohms you have to half the size of the cap to keep that relation. Remember that the filter (here in my example, like the Klipsch A) is just a cap which is feeding the autotransformer, which in turn feeds the driver. Consider the autotransformer with taps which decrease the power by 3 dB for every tap change. We know that P = V^2/R. The R is the effective load seen looking into the autotransformer. So for every 3 dB the load seen is doubling. Let's consider a driver with an effective impedance of 12 ohm in the voice coil. On the -3 dB tap, the effective impedance seen looking into the autotransformer is 24 ohms. And I think we'll see that the Xc at 400 Hz of the 6 uF cap in the type A is indeed 24 ohms. But moving to the -6 dB tap, the load presented by the autotransformer is 48 ohms. Now we need a cap half the value. This is consistent with the above posts. So what is the magic with Al's Xover? It is the swamping resistor of 10 or 11 ohms. This is wired across the input to the autoformer. Thus it is in parallel with it. Now we have to take a closer look at parallel resistances. Without having the math in front of me. Roughly, a 24 ohm load (3dB down tap used) in parallel with the 11 ohm drives the parallel resistance down to about 9 ohms. So we can pick a filter designed for that. (Al is using a 12 dB high pass, but lets not get too complicated.) However, when we go to taps on the autotransformer the load from it, which is part of the parallel load goes up and up. BUT, the calculated number for load on the filter only creeps up to 10 or 11 ohms. The "swamping" resistor has really swamped out the variation of the load on the filter. This is all the effect of the math which decribes the parallel circuit, of which the swamping resistor is the dominant factor. The result is that Al's design allows the changing of the taps without much effect on the crossover point. Genius. Some of the above math is just approximations, but you can see the trends. Best, Gil Quote Link to comment Share on other sites More sharing options...
Deang Posted November 18, 2004 Author Share Posted November 18, 2004 Beautiful. Thank you Gil. So Dennis has the most simple and straight-forward approach, and the swamping resistor would appear to be applicable to any of the networks utilizing the T2A (or UT 3619). Yes? If no, is this because AL uses a 12db/octave on the high pass -- and where does this leave Dennis' suggestion? Is the proper solution for the A and AA with the #3 tap to halve the capacitance, and forego the swamping resistor? Quote Link to comment Share on other sites More sharing options...
WMcD Posted November 19, 2004 Share Posted November 19, 2004 Dean, Again, all of this is consistent. I think that K-Horns sometimes sound too hot in the midrange. There can be several reasons. One may be a room with little bass reinforcement. Others suggest the P-Trap circuit to cut out a peak above 6 kHz. Going to 6 dB step down in the midrange could be a help. So you either supplement the load with a 16 ohm resistor and keep the cap, or you decrease the cap value. Either way you're preserving the crossover point of the filter at 400 Hz. I think the 12 dB circuit that Al uses is beneficial. None the less you should take a look at the article by PWK on the K-400 which I posted in Technical Questions about two weeks ago. The K-400 and K-5 both go down to about 400 Hz and then fall off very, very rapidly. I think his sound curves were run without a crossover. Gil Quote Link to comment Share on other sites More sharing options...
djk Posted November 19, 2004 Share Posted November 19, 2004 In the early days theater stuff had a cap for every tap on the inductor. Expensive. A bolt out of the blue strikes, we only need one High$ cap and a bunch of cheap resistors. http://www.jblproservice.com/pdf/Network%20Schematics/LX5.pdf Quote Link to comment Share on other sites More sharing options...
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