Al Klappenberger

Duder, The efficiency will be the same for 8 or 16 Ohms. Which one to get depends on what impedance the network was designed for. Power = voltage squared over impedance. (P = E * E / Z) If Z is 16 ohms, the driver draws half the power and delivers half the output with a GIVEN VOLTAGE. The difference is 3 dB less output from the 16 Ohms driver than the 8 Ohm with a GIVEN VOLTAGE. The efficiency is the same. Again: Get the driver with the impedance that matches the network it is to be used with. In the case of my networks, it makes no difference. You just move the autotransformer tap up 3 dB higher for the 16 Ohm driver than for the 8 Ohm driver. Al K.

Dave, I remember you told me that before. Old age I guess. The memory cells are wearing out! Al K.

hklinker, Yes, those are mine. They were an extra set from a customer who sold his speakers before I could get them built. It took me so blasted long to get the parts he had forgotten he ordered them! This tells me I need to speed thing up SOMEHOW! .. Groan! Al k.

Dave, I just noticed that the motor board square to round adapter mysteriously changed from aluminum to plywood. Do you plan to go to plywood or is that just an experiment? Needless to say, the crossovers look pretty good to me too! Al K.

He's right. The drivers I am using are the JBL 2426h. It's the 8 Ohms version, The 2426j is the 15 Ohm version. They make excellent squawker drivers. They are supposed to go out to about 15 Khz but start to show major roll off above about 6 Khz. I have used them 2-way but require EQing to do it. AL k.

Robert, I don't follow your thinking. The AP15-6000 is the top section of the Universal PLUS the tweeter attenuator. It has two inductors and 3 caps. The squawker transformer is located on the AP12-600. The two are connected together by a 3-wire cable that makes each module compatible with my extreme-slope networks. There is no kit version for it. You would need to get all the parts yourself to make it a DIY project. Al K.

The AP15-6000 network is simply the squawker to tweeter crossover section of the Universal built on a separate board from the woofer to squawker section. Al K.

Shawn, Good old 20-20 hindsight! I wish I had done intermod distortion tests on that 902 you sent me long ago like I did on the JBL 2426 just a few months ago. It would answer a lot of questions. I got an email minuets ago from a fellow who just got a set of Belles with the Trachorn, 902 and my Kit Universal networks in them. He is having trouble with distortion, I suspect, although he describes it as harshness. I suspect a 1st order crossover at 400 Hz is just pushing the 902 to far! Al K.

Dave is right about the 500 - 600 Hz change. The networks he is thinking of are the AP12-600 and the AP15-6000. They are step above the Universal network in that the woofer to squawker section is specific to one crossover frequency and therefore a single speaker. Al K.

More important than if the driver will go down low enough is the distortion down low. I did some intermod test on a JBL 2426h, which I think is a more robust driver than the Altec 902. It generated major distortion even below 500 Hz. I really think the 902 should not be used below about 600 Hz even with an extreme-slope crossover. I would need to actually run tests on one to be sure about that though. Al K.

"It gets wierd above 450hz or so, that would be my choice for an ES crossover." I'm quite sure the Es400 network, which was designed for the Khorn, would work in the LaScala. It doesn't have quite as sharp a slope as the ES500 or ES600. I could easy do an ES450 design and post the schematic of it turns out to be the right place. I think it will limit your choice of drivers though. I don't know of any driver but the K55 that will run safely down at 400Hz on a 1-inch horn. I would definitely be scared to run an Altec 902 that low. Al K.

John, I have never run a curve on the LaScala, but the Belle woofer is similar and I have crossed mine over at 700 Hz for a while. It worked fine. I think 600 Hz would be both safe for the 902 and would be well within the upper limit of the bass horn. You will need an ES network to keep the lows off the 902 though. Al K.

BBQ, That is one of two caps that are part of the woofer filter. Removing one cuts the capacity in half. That would allow the woofer to go up higher and probably make a very rough response in the process. I would need to check this in the computer to find exactly what it would do, but I'm sure it won't be good. I would connect the cap back as it was designed to be. Al K.

kt This horn is the early version of the horn that will replace my Trachorn 400 now that Bill Martinelli has moved on to other things. I have been running tests on a similar horn to verify it's performance. The instrument tests look good. Al K.

Dave, My drawing says: A = 31.0 In. B = 12.5 In. C = 28.0 In. C - B should equal A / 2 and it does, so I think it's correct. Al K.

The Universal network runs the tweeter wide open. With the K77 and other high efficiency tweeters, an attenuator is often needed, The CT125 has lower efficiency and happens to be just perfect for the Universal. The ES networks have the tweeter attenuator built and can adjust to any 8 ohm tweeter. It's an option with the universal. Al K.

I think the only reason to move the crossover from 6000 down to 4000 is as a crutch for the K400 horn. The lower you cross over to a good tweeter the less you hear the K400 horn. I suggest replacing the K400 with a better horn and leave the crossover at 6000. Doing that will also keep you from having to replace the tweeter, unless you want to. The K77 isn't reliable down to 4000 Hz. Al K.

Guys, For whatever it worth, here's the measured performance of the woofer. It was done using the "close mike" technique. The markup job and comments were added by my late friend Mr "P" (Max Potter). The actual efficiency (sensitivity) is roughly 90 dB SLP at 1 meter. The black trace is the woofer driver. The red one is with the mike right at the port. The summation was drawn by Max. Al k.

Dave, One warning I want to harp on and I already said this to you in an email: THERE IS NOTHING MORE DANGEROUS THAN A SAFETY DEVICE THAT DOES NOT WORK! Don't take it for granted! Assume that the saw is just as dangerous as any other saw and that innocent looking feathery edge is out to get you. FEAR IS HEALTHY! Al K.

Shawn, I suppose the next step is deciding to actually do a test like this. I would like to do it, but the cost of building four matched set of networks plus the switching box could get expensive. For me, knowing if I can or can't hear a difference in caps wouldn't matter. What matters is what my customers want. I still would have to use the expensive caps no matter if I can hear a difference or not. People expect it! Al K.

Tom, I agree totally! I have an LF-10 sub on my main system. It will go down to 20 Hz. On music I just don't need it. The Belles handle everything needed. All it seems to add is the thumping of dancers feet around the stage on live recordings of ballet music, for example. I suppose I should move the thing up to the den where I watch TV. but I would have to get the lead out of my butt to do that! I really don't have a good place to put it up there anyhow. Al k.

Shawn, Yeah! That all sounds good. I have been thinking about that since my last post and I was going to say that I infinity want to know when the switch happens, but not what is selected. I also thought about the sound of the relays, if you hear them. You could definitely hear a clue about what was selected since a relay has a different sound on pull in then on release. With 4 poles though, it could be wired such that A is selected by two relays pulled in and two released. B would swap them. Two in and two out at the same time would make the same sound on A or B. I think the "buzz" would still be needed in case the same selection happened twice in a row. Al K.

Shawn, I see your point. I think that the sound from the speakers would cover the relay sounds if they were located in a box covered with an acoustic silencing materiel. Another idea would be to use a second or two of rapid relay switching which would stop at the setting dictated by the controller. It would just sound like a buzz. I am assuming that the controller would be a computer program running a random number generator to select the A, B or X condition. A transition period of buzzing shouldn't be hard to do. I'm not sure if you figure the listener should know when the switching action takes place or not. I would think he should know when to take note of changes. If not, the buzz idea would be out the window! BTW: I have a box here that has a bank of reed relays (SPST) that are operated by a GPIB buss from a computer. I use it to select channels when testing networks. The computer also runs the signal generator and the analyzer. That thing could easily be used to run the relays that ultimately swap the networks under computer control. Al K.

Shawn, Here's what i think would be required. The switch would be run by the A/B/X controller. The two networks would be as Identical as they could be made but using two different brands of caps and matched left for right for value as close is possible. Al k.

Shawn, I'm not following you on the switching. Of course single pole switches can be riged to select two differnt things, one is off while the other is on, then swap them, but that still functioning like a single pole 2 postion switch. You would need one set of these for each driver and one to switch the amp between netwroks. That works out to a 4 pole 2 postion switch requiring 8 single pole ON / Off switches for each channelin a 3-way speaker. Am I missing something? Al K.