Al Klappenberger Posted November 13, 2003 Share Posted November 13, 2003 Guys, Here's an entirely new crossover design being developed for Shawn Fogg (Sfogg). I expect to make it available for use in 2-way or 3-way systems based on the Belle Klipsch or LaScala woofers. This will include the stock Belle and LaScala. I will also be posting the design itself, for the DIY people, including the schematic in later posts. I want to delay posting the layout drawings because it will be critical because of inductor coupling problems. I also expect to change the layout a bit on the next prototype to address the problem. The design crosses over at 600 Hz (actually about 605 Hz) and is an extreme- slope design. The woofer filter reaches 22 dB down at about 680 Hz. The highpass filter reaches 26 dB down at about 530 Hz. Rejection is equal to or greater than that as you go away from the crossover. This gives a window of only about 50 Hz centered at 605 Hz where both drivers are less than 10dB down and can interfere with each other. The new innovation with this design is that it compensates, and actually utilizes, the inductance of the woofer voice coil WITHOUT the use of the usual Zobel R-C combination. It was found that the Belle woofer complex impedance (and I assume the LaScala woofer) actually measures 5.9 +j4.01 Ohms at 600 Hz. This is equivalent to 6 Ohms in series with a 1.06 mHy inductor. The lowpass filter in this network was synthesized to have a 1 mHy inductor at the output. This inductor was simply left out of the filter and becomes the woofer inductance. The results of the combination measures a very flat resistive 6 Ohms impedance all the way from the woofer resonance to beyond the crossover. The reactive component of the impedance measures about 1.4 Ohms right at the crossover input. This is the worst case and represents a "VSWR" of only 1.27:1 in a 6 Ohm system. "VSWR" can be thought of as a measure of impedance mismatch which includes complex impedance. Anything below 1.5:1 is considered good. 1:1 is a perfect match. The speaker will be transformed to a 6 Ohm speaker which should operate very nicely from the 4 or 8 Ohm taps of any power amp. The machine-run plot of complex input impedance is attached. The plot was done with the Belle woofer connected to the lowpass filter and an 8 Ohm load resistor terminating the highpass filter. More in the next post. Al K. IT SEEMS THE IMPEDANCE PLOT GOT LOST. I HAVE ATTACHED IT DOWN A FEW POSTS BELOW. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 13, 2003 Author Share Posted November 13, 2003 Guys, I have attached a photograph of the new network. As you can see, it is quite large and requires 4 inductors and 9 caps. The base board measure 13.5 X 8 Inches. It's a little difficult to see, but the large inductor at the lower left corner is jacked up 1 inch to center it with the inductor next to it (above it in the picture). This area will be laid out differently in the next prototype. The two coils wanted to talk to each other messing up the slope of on of the filters. Note that there is a removable strap connected between the 4th and 5th screw terminal on the barrier block. This connects the output of the highpass filter to the input of the autotransformer and swamping resistor. The strap may be removed so that an external crossover from a squawker to a tweeter may be connected with the squawker output fed back to the transformer. This will allow 2-way or 3-way operation. The transformer taps are connected to plugs so that the level can be adjusted just like with my type "A" replacement network. Because the transformer could also be located on the external squawker / tweeter network, the transformer and tap plugs will be optional. Al K. Quote Link to comment Share on other sites More sharing options...
Colin Posted November 13, 2003 Share Posted November 13, 2003 beautiful, you are the Klipsch crossover specialist! what are the orange wires terminated with blue caps? are you thinking of an improved crossover for the Khorns then? is the cost even higher? Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 13, 2003 Author Share Posted November 13, 2003 Guys, Here's the schematic diagram of the new network. Don't go ordering any parts yet though! The layout is going to change. I don't expect the values to change though. AL K. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 13, 2003 Author Share Posted November 13, 2003 Colin, The wires you are seeing are the leads from each of the transformer taps with a plug on the end. They plug into shove-on-terminals connected to the high output of the netwrok. You move them to adjust the output level for various drivers. This is identical to the arrangement on my "stock" replacement network. A network for the Khorn will be a bit more trouble. That's down the road! As to pricing, I'm not worried about that yet. For now, it is just a developement project. Al K. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 13, 2003 Author Share Posted November 13, 2003 Guys, Here's the impedance plot that got lost from the first post. Al K. Quote Link to comment Share on other sites More sharing options...
Rockets Posted November 13, 2003 Share Posted November 13, 2003 Al, here is a chart John Warren presented prior of an unbaffled K-33 vs. baffled in a Khorn (IF I'm not mistaken). I'm amazed, but maybe I shouldn't be, as to the > 2 ohm delta between your Belle measurements and the Khorn and wonder how much of a spread is possible between the Belle and the Lascala?? While the spread may not seem to be much in the 'real world', once again I wonder of its impact on XO design parameters. Could one really hear the difference of a couple of ohms Z, and the subsequent change in values in L/C?? I read your paper on extreme XO's, and have questions, but will email you at a later time when I have a firmer grasp as to exactly what I'm asking... Thanks TC Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 13, 2003 Author Share Posted November 13, 2003 TC, I am courious about the difference between John's plot and mine. I think his was of the raw k33 driver OUTSIDE the hron (I think). His plot is also simple impedance. My plot includes the reactive (inductive) component. I think there is also some difference between horns too. I really wish I had a LaScala and a Khonr here to do measurements on! The significance of the impedance matching really relates to the performance of more complex filters. A simple 6 dB / octive filter can operate into anyhting. It's all over the place anyhow! A more complex filter, even a 12 dB / octave, starts require a good terminaiton to act as it should. It also matters to some amps. I suspect a multi-million dollar Krell wouldn't care what it's terminate with, but a little SET "one lunger", as I call them, should see a good load. Their source impedance is pretty high (poor damping factor). In my case though, it's just "my thing" to work to a falt impedance. It comes form the absolute need to do it at microwave frequencys where I "grew up"! Al K. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 13, 2003 Author Share Posted November 13, 2003 Guys, Well, the say: in for a penny, in for a pound. I might a well include the plot of the network by itself. Here's the high and low outputs plotted into resistive loads with an external 1 mHy inductor between the lowpass section output and the load resistor. The insertion phase is also shown. If anybody is interested in Group delay, it looks to be somewhere between 2.5 and 3.0 mSec at the crossover. It goes way down on either side of the crossover very quickly. I can't measure it accurately though. I can only calculate it from the phase data at each frequency point. In any case, I am quite sure it is below the limits set by the well known B&L criteria. I have come to believe group delay is not important anyhow. Al K. Quote Link to comment Share on other sites More sharing options...
John Warren Posted November 14, 2003 Share Posted November 14, 2003 , Quote Link to comment Share on other sites More sharing options...
John Warren Posted November 14, 2003 Share Posted November 14, 2003 . Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 14, 2003 Author Share Posted November 14, 2003 John, The impedance method you are used is quite valid. It's described in a book I got here by Dickason as the "Voltage divider method". I used to do it that way myself. The only problem is it doesn't tell you what part of the impedance is reactance. The instrument I am using is very old but fancy beast made by Spectral Dynamics called a "Dynamic analyzer II" model SD375. I got it on eBay. It cost me roughly $70! I also am using a HP 7470a digital plotter, also from eBay for less the $10! Remember, my main business is filter design software. Crossover networks began as a hobby too. I never believed when I started doing this that anybody would actually want me to build these things for them and actually pay me to do it! Anyhow, The SD375 is a dual FFT spectrum analyzer that maintains phase data between the A and B channels. That gives it the ability to compute and display all sorts of information about the two including transfer function between A and B channels. I have a bridge set up with two 3300 Ohm 1% resistors and a 10 Ohm resistor as a reference on one side. That runs channel A. With the unknown on channel B, it displays complex impedance as the ratio of A to B in the transfer function mode. The scheme is fairly accurate so long as the unknown doesn't get more than about 2 times the 10 ohms reference. It depends on a constant current. That goes to pot if the unknown gets large enough to unbalance the bridge. I think it's actually within the ball-park up to about 50 Ohms. I have attached a picture of the SD375. The big down-side to the thing is that it weighs 55 Lbs! Lugging it down the steps from the office to the listening room is a real drag! Al K. Quote Link to comment Share on other sites More sharing options...
John Warren Posted November 14, 2003 Share Posted November 14, 2003 . Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 17, 2003 Share Posted November 17, 2003 Al, Looks very good. I am very curious to hear how the very slight overlap (and attendant reduction in interaction) between the drivers is going to sound. How did the Belle sound run as a two way with this crossover and the Altec? Thanks, Shawn Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 17, 2003 Author Share Posted November 17, 2003 Shawn, I think you will be quite pleased. I could only compare it to the 3-way arangement of my Belle + JBL 2426h and Beyma. pink noise had a slightly higher pitched quality through the 3-way system than the 2-way using the Altec 902 driver. I can only assume this is due to the better dispersion of the Beyma up high compared the the Altec 811bs dispersion up high. I expected that though. I will say tis though, the JBL 2426h woudn't make a bump on an Altec 902s posterioe running 2 way! The jebl really NEEDS the help of the tweeter! I am very anxious to hear how you like it especially if you try it 3-way using my standard network as the squawker/tweeter crossover. When you do that I need you to short out the 39 uF cap and leave its woofer port open. AL K. BTW.. The crossover and driver were shipped this morning by FedEx ground in seperate boxes. Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 17, 2003 Share Posted November 17, 2003 Al, " pink noise had a slightly higher pitched quality through the 3-way system than the 2-way using the Altec 902 driver." It will be interesting to see how this compares to a t35. The Altec looks like it goes higher but maybe not with quite as good of a dispersion. I'll try and doing some testing of that when I get a chance. If the high end is a little soft my pre/pro can do a little digital EQ to bring it up a touch if needed. "I am very anxious to hear how you like it especially if you try it 3-way using my standard network as the squawker/tweeter crossover. When you do that I need you to short out the 39 uF cap and leave its woofer port open." So just feed the standard network from the high pass section of the ES600 and leave the standard networks woofer out completely open or should I terminate it with a resistor? One of the things I want to do is build a relay box that will let me swap between the standard crossover used as a three way vs. ES600 crossover as a two way via remote control from across the room. Easy enough to do.. just need to find the time build it. It could also be used to compare other three way crossovers or even to compare ES600 two way vs. stock 3 way setup with AA for example. Looking forward to receiving the network. Thanks again for all the work on this. Shawn Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted November 17, 2003 Author Share Posted November 17, 2003 Shawn, No, don't terminate the woofer output port. You want the 400 Hz woofer crossover totally out of action. The ES600 will perform that job. That consists of the 2.4 mHy inductor and the 39+1uF cap. Open the inductor (no termination) and short out the cap. This leave the input connected directly to the 6000 Hz squawker / tweeter crossover. You will then be using the autoformer in the convention "A replacement" network to run the squawker. In 2-way operation you will need to use the transformer on the ES600. Al K. Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 23, 2003 Share Posted November 23, 2003 I received the ES600 from Al earlier this week but haven't had any chance to play around with it till now. I haven't lisened to it too much so far but my initial impressions are favorable. This is using the LaScala as a two way with the regular bass horn but from 600hz and up is handled by an Altec 902-8B on a 511b horn. The attached is a FR measurement with the mic in the 511b horn to get an idea on how sharp of a crossover this is. Shawn Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 23, 2003 Share Posted November 23, 2003 This is the FR of the LaScala as a 2 way using the same combo. Mic measured about 4' from the speaker. Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 23, 2003 Share Posted November 23, 2003 This is of my other LaScala using a conventional ALK as a three way speaker and the Altec as the midrange on a 511b. The different position in the room of the speaker will be the difference in the bass. Shawn Quote Link to comment Share on other sites More sharing options...
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