In trying to design a Zobel network for my next project I have observed that the printed T/S is L @1Kz is 1.34mH. Using my LCR meter at 1Kz I observe a reading of 234uH. Can anyone explain the difference. Which value would you use? This is a 3/4" polydome tweeter made by pioneer model FBDE75-52
Why do you want a Zobel for the tweeter? They usually aren't required unless you are crossing to a supertweeter. They can be used for response shaping if you use nonstandard values, but from your question I don't imagine you are using it this way....
1mH sounds like a lot for a tweeter - Re and Le measurements really should be done with the voice coil clamped(obviously not possible with a finished driver) - and Le actually changes with frequency so.....
1mH sounds like a lot for a tweeter - Re and Le measurements really should be done with the voice coil clamped(obviously not possible with a finished driver) - and Le actually changes with frequency so.....
"Location: Behind you"
I was wondering why the hair on my neck was standing up.
I will do as you have suggested and plot the impedance curve.
Now get thyself to a music store and pick up the album "Blast Tyrant" by Clutch. Great rock and roll and somewhat of a concept album following the adventures of the space ship "The swollen goat". Great heavy Metal for evil and non-evil people
I was wondering why the hair on my neck was standing up.
I will do as you have suggested and plot the impedance curve.
Now get thyself to a music store and pick up the album "Blast Tyrant" by Clutch. Great rock and roll and somewhat of a concept album following the adventures of the space ship "The swollen goat". Great heavy Metal for evil and non-evil people
The inductance of the voice coil is far from that of an ordinary coil. The inductance varies a lot with frequency. Furthermore, if inductance is measured from the reactive part of the impedance at one frequency, the box size will affect the measured value. The bottom line here is that a zobel network cannot fully compensate for the voice coil inductance (since there is no capacitor that mirrors the frequency dependant inductance). The best thing to do is to connect a zobel network and measure the impedance as a function of frequency, and adjust the R and C until an as flat as possible impedance is reached. ...or you could simulate the whole thing using a voice coil impedance of Re + K * w^n * e^(j*n*pi/2), where Re is the voice coil resistance and K and n describes the "inductance". n is typically 0.6-0.8, and K in the same order of magnitude as Le.
You don't need a zobel for the inductive rise of a tweeter except in rare circumstances - most of the time you are better off leaving it inductive because it is better for your amp - capacitive or low impedance at high frequencies can cause oscillation. I have yet to see a professional crossovr that uses a zobel on a tweeter that small.
If you are designing a zobel for the impedance peak of the tweeter, Le is not a factor. Actually, the impedance peak is much more likely to be trouble in crossover design than inductive rise in a tweeter.
If you want to learn about designing speakers, buy or build a wallin jig and measurememtn mic and preamp. Then download speaker workshop and you can measure your speakers and simulate the crossover. Even before you have all the necessary hardware, you can even import other people's measurements and design crossovers and see how they work....
cheers from a big town in Minnesota
If you are designing a zobel for the impedance peak of the tweeter, Le is not a factor. Actually, the impedance peak is much more likely to be trouble in crossover design than inductive rise in a tweeter.
If you want to learn about designing speakers, buy or build a wallin jig and measurememtn mic and preamp. Then download speaker workshop and you can measure your speakers and simulate the crossover. Even before you have all the necessary hardware, you can even import other people's measurements and design crossovers and see how they work....
cheers from a big town in Minnesota
"cheers from a big town in Minnesota" hmm......home of the Replacements I'm guessing?
Svante, thanks for the description of how to select Zobel values. I will absolutely use that process for my project I just need to start stockpiling some components of different values. There are no stores(except radio shack) where I can get components from so I need to order them through Digikey, or build some resistance and capacitive substitution boxes I ran across on the net somewhile back. Many thanks to you also Ron E! Will speaker workshop run on an old power pc Mac? Blazing 75 MHz machine!
Svante, thanks for the description of how to select Zobel values. I will absolutely use that process for my project I just need to start stockpiling some components of different values. There are no stores(except radio shack) where I can get components from so I need to order them through Digikey, or build some resistance and capacitive substitution boxes I ran across on the net somewhile back. Many thanks to you also Ron E! Will speaker workshop run on an old power pc Mac? Blazing 75 MHz machine!
eddog said:
Yup.
I'm afraid Speaker Workshop won't run on a mac that I know of. You can get pretty serviceable used PC's (500MHz-1GHz or so) with monitor and OS for about $250 if you know where to look. I use Linux for online uses and for fun, but have an old W98 partition for all the fun freeware.
For parts, you can check out Madisound's sale page. There is a small (hole in the wall) speaker repair shop just south of 94 on Snelling avenue in St Paul - Midwest Speaker Repair. IT's a retail shop so not a cheap place to buy drivers, they want at least 50% more than Madisound for drivers - they sell Peerless classic line - they also have some crossover components.
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