BEC Posted January 2, 2004 Share Posted January 2, 2004 While checking out the new (to me) Wavetek Specturm Analyzer I just got, I thought I might test a crossover. This plot is three separate traces combined on one sheet which show the three outputs of the crossover with the same pink noise signal at the input. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 2, 2004 Share Posted January 2, 2004 Bob, I think you may have a fine instrument there. I have been doing similar tests using an old Spectral Dynamics SD375 analyzer and I also have an HP7470A plotter. I suspect that you are using white noise, not pink. What's generating the noise? Al K. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 2, 2004 Share Posted January 2, 2004 Bob, I did a little research on that Wavetec analyzer. It's more than just a spectrum analyzer. You can do some very serious analysis of a crossover by using it's "Transfer function" mode. That will show you insertion phase and totally remove the response of the noise gnenerator from the curve. Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted January 2, 2004 Author Share Posted January 2, 2004 Al, The generator is built in to the Wavetek. What I was using is called "A white noise signal whose spectrum is band limited and band translated to match the selected measurement span". I think that is what I used to call "pink" noise since it is composed of only frequencies inside the test bandwidth. The unit also has a sine generator that outputs a sine wave signal at the position of the cursor. That feature should be extremely nice at doing something like filter tuning. Bob Quote Link to comment Share on other sites More sharing options...
sfogg Posted January 2, 2004 Share Posted January 2, 2004 White noise is equal energy by frequency. Pink noise is equal energy by octave. Band limiting the noise doesn't really have anything to do with it being white or pink noise. Shawn Quote Link to comment Share on other sites More sharing options...
BEC Posted January 2, 2004 Author Share Posted January 2, 2004 Al. I have some more reading to do before I will understand all the complexities of this analyzer. This is the first one I have used since the 70's and I am lucky it came with the full manual. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 2, 2004 Share Posted January 2, 2004 Bob, sfogg is correct. What you used is simply bad limited WHITE noise. Pink noise shows a 3 dB / octave slope. The sine wave mode you mentioned is an option on my SD375 that I don't yet have. I am looking for it but so far haven't had any luck. sfogg has an analyzer similar to mine but a bit newer (SD380). I got a hunch the one you have is nicer than the ones we have and certainly newer. Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted January 2, 2004 Author Share Posted January 2, 2004 Al, I stand corrected on my white/pink noise terminology. My only defense is that the chief engineer for the audio test lab I bought the analyzer from told me that it was perfect for audio frequency response testing since it had a pink noise generator built in. They used it for setting up sound systems in some large concert halls and auditoriums around the country. They have moved on to the newer hand held types of analyzers that are a bit easier to travel with. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 2, 2004 Share Posted January 2, 2004 Bob, The pink / white error was probably just a quick comment he made without thinking about it. Pink noise is generated from white noise with a simple R-C filter you could build if you ever really needed pink noise. My SD375 will dipslay 1/3 octave bands using pink noise. That is usually what it's used for since it is said to more closely resemble music. Using transfer fuction mode, it doesn't matter which type you use since only the ratio if channel A to B is important. What you have is quite well suited to audio testing. He made no mistake when he told you that. Al K. Quote Link to comment Share on other sites More sharing options...
acresm22 Posted January 5, 2004 Share Posted January 5, 2004 Hello all, I'm a Klipsch Forum newbie, and have some questions regarding the Type A crossover... I recently purchased a pair of LaScalas at a garage sale, 1982 models with Type AL crossovers, and I want to replace those with the Type A crossover. I don't have the time to build the crossovers myself, so was wandering if anyone out there offered custom built Type A crossovers as drop-in replacements... I'm using the speakers with a Jeff Korneff SE amp that uses 6L6G tubes in triode mode, for a whopping 2.8 watts. Sounds glorious, but think it could be that much better with the Type A crossovers in there. Any info or thoughts would be much appreciated! A. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted January 5, 2004 Share Posted January 5, 2004 Type A, AA or ALKs would be superior to AL networks IMHO. I sent you a PM. Go to your profile to see it. By the way< Welcome to the forum! And enjoy those Lascalas! Rick Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 6, 2004 Share Posted January 6, 2004 A. I'd be willing to build up a pair for you. I've already done the Al K crossovers for my own LaScala's. I'd recommend building them from scratch, reserving the original for the day (hopefully it never comes) you offer the speakers up for sale. There's an enhanced version of the Klipsch T2A autoformer available, use the well-regarded Solen 14 ga. inductor, probably Solen or similar for the 13uf, a $24 Hovland for the 2uf, mount a pair of decent binding posts right on the board. I used nice Oak board for mine, but wood of your choice can be used. Cost = cost of parts and $100 labor. I'd guess around $250 or so. Gauranteed to last your lifetime. With your choice of amp tweeter protection is not really an issue, keeps the circuit simple. This will be a sweet sounding deal. Tom tmoble at cox daught net is my email Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 6, 2004 Share Posted January 6, 2004 here's a rather crummy pic of my DIY ALK crossovers. Some of my first attempts at a digicam. Tom Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 6, 2004 Share Posted January 6, 2004 and another, detail. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted January 6, 2004 Share Posted January 6, 2004 Tom, You did an excellent job on the networks. Al K. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted January 6, 2004 Share Posted January 6, 2004 Tom: Did you order the parts from the various suppliers mentioned in Al's list, or did you find a one stop supply? I am considering making one for my center channel. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 6, 2004 Share Posted January 6, 2004 I used Al's list. I think Madisound now carries more of the stuff. I actually ordered some of the stuff from Solen in Canada, shipping was very slow. Thanks, Al. If I had it to do over I'd pony up for the Hovlands. I used the low-cost option but the leads on the caps weren't long enough and I had to splice pieces onto the leads to get them to reach. A small thing yeah, but jeez. My DIY LaScala's had new k-33, new diaphragms in the K-55-V and K-77, I built these crossovers and was amazed when I fired them up. What a killer deal. Quote Link to comment Share on other sites More sharing options...
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