I'm a bit confused here, why test a woofer with a series resistance?
That will stuff up the damping factor so I would think its totally bad practice.
Doing tests on a tweeter would be more relevant I would think?
I guess a 2 resistor Lpad arrangement on a tweeter makes more sense than a single series resistor anyway as it'll be a more stable load for a xover. (less variation with freq)
As for whether a series resistor before the xover changes the xover freq/Q factor etc, it seems to me from my listening tests that maybe it does, but its inclusive to me so far.
I also tried the resistor after the xover, and that changes massively the response of the tweeter, a very noticeable change and not for the better.
That will stuff up the damping factor so I would think its totally bad practice.
Doing tests on a tweeter would be more relevant I would think?
I guess a 2 resistor Lpad arrangement on a tweeter makes more sense than a single series resistor anyway as it'll be a more stable load for a xover. (less variation with freq)
As for whether a series resistor before the xover changes the xover freq/Q factor etc, it seems to me from my listening tests that maybe it does, but its inclusive to me so far.
I also tried the resistor after the xover, and that changes massively the response of the tweeter, a very noticeable change and not for the better.
It stands to reason, shmb. If I could throw in my 2c about the plot in post #12, the dark blue trace (resistor after filter) comes down to join the red (L-pad) trace at its lower end. Ie: the resistor after the filter keeps the crossover point whereas the light blue (resistor before) doesn't.
However, it is the higher up parts that we care about more and the resistor after doesn't control that well. Some tweeters have worse impedance peaks than others.
However, it is the higher up parts that we care about more and the resistor after doesn't control that well. Some tweeters have worse impedance peaks than others.
Is it possible to do a simulation on my design?
Heres my situation: The tweeter is a Vifa D25AG-35-06 (6 ohms) and it uses a 12db HP xover, with a 5.6uF Cap and 0.47mH Coil.
Originally I had a 2.2R resistor in series (before xover) and gradually, after many listening tests, ended up with a 6.8R.
Now, since reading this thread, I've tried removing the 6.8R and replaced it with an l-pad arrangement (after the xover) consisting of a 6.8R in parallel with the tweeter and a 2.7R in series. Theoretically, the tweeter should now be louder, but it sounds almost softer now, probably because its so much smoother and imaging has improved massively.
Is it possible to do a simulation of my situation with the single series resistor vs l-pad arrangement?
Heres my situation: The tweeter is a Vifa D25AG-35-06 (6 ohms) and it uses a 12db HP xover, with a 5.6uF Cap and 0.47mH Coil.
Originally I had a 2.2R resistor in series (before xover) and gradually, after many listening tests, ended up with a 6.8R.
Now, since reading this thread, I've tried removing the 6.8R and replaced it with an l-pad arrangement (after the xover) consisting of a 6.8R in parallel with the tweeter and a 2.7R in series. Theoretically, the tweeter should now be louder, but it sounds almost softer now, probably because its so much smoother and imaging has improved massively.
Is it possible to do a simulation of my situation with the single series resistor vs l-pad arrangement?
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Possibly. You can't assume the tweeter behaves like a resistor whose value varies according to the impedance plot and when you rearranged this you did more than just changed the impedance magnitude. To be certain, you need to include impedance phase.
Anyway, my considered guess is that your tweeter is now a little louder, but it cuts off at a higher frequency. I'd say maybe half an octave, ie: above 2kHz now.
Ok, well it does sound like its crossing over higher, maybe that's it, but how can that be?
I always thought, from what I've read in the past, that a second order filter (unlike a first order) won't vary its cutoff freq with impedence, only the Q varies?? Maybe its got something to do with what you mentioned just then, ....impedence phase? What does that mean?
Also, in the datasheet for the tweeter, it gives a recommended xover circuit diagram of an 8uF Cap and 0.22mH Coil. (second order) Then after that it says "The impedance load provided by the x-over should be as low as possible at the tweeter res. frequency. (850Hz) This will ensure maximum electrical damping and consequently minimum excursion."
What does that mean in practice? How do I achieve this?
Since I'm using quite different Cap and Coil values to the recommended ones, should I be using their values instead? The higher Q of their filter may bring it to life a bit more?? Its quite mellow sounding atm.
Once again sorry for going slightly off topic.
You removed the leading resistor that was reducing the crossover point.
Electrically, the tweeter can behave capacitive, through resistive to inductive.
This doesn't sound right, could you check it doesn't say: "The impedance load provided to the crossover..."
Probably means that they expect the impedance peak at resonance to be dealt with. The simplest way to do this is to use an L-pad but the effect will be only partially dealt with in that case. The better way to do it is to use one resistor, capacitor and inductor in the form of a series notch filter. This creates an equal but opposite peak for a flat total. If you can find such an impedance peak compensation filter on an existing design with this tweeter then it will save you the time of measuring your own tweeter and simming it.
Will probably give you a few dB just around the 5kHz region.
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Hi,
It does sound right, it means the source impedance seen by the tweeter
at its Fs should be low. For second order parallel the 0.47mH shunting
inductor does give a lowish source impedance of < 2.5 ohms so the
mild Fs peaking should not be a real problem.
rgds, sreten.
"Now, since reading this thread, I've tried removing the 6.8R and replaced it with an l-pad arrangement (after the xover) consisting of a 6.8R in parallel with the tweeter and a 2.7R in series. Theoretically, the tweeter should now be louder..."
If you had moved the 6.8R to the back alone the tweeter would have been louder, but then you added a voltage splitter, the 2.7R, which really makes an impact. Try the theory by removing the 2.7R. You will see. And by the way, put the 6.8R in series, like before.
If you had moved the 6.8R to the back alone the tweeter would have been louder, but then you added a voltage splitter, the 2.7R, which really makes an impact. Try the theory by removing the 2.7R. You will see. And by the way, put the 6.8R in series, like before.
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Yes it is definately correct as seen here: http://www.d-s-t.com.au/data/Vifa/D25AG-35-06.pdf
Interesting info here, thanks guys.
Interesting info here, thanks guys.
As a follow-up question: For a 8ohm impedance load and I want to lower the level by -3db. I have used a L-pad calculator listed on L-PADS. The value of the serial and the parallel resistors are 2.34ohm and 19.34 ohm respectively. The power going through the serial and the parallel resistors are 29.2W and 20.7W respectively for a 100W feed. When I look up the power rating for the resistors available at parts_express, the resistors are mostly 5W and 10W rated. Will the be blown out if too much power are feed to the speakers? Thanks
Don't use full power. Or if you are to the max make a series/parallel connection with 4 resistors of each/same value. You can also use 15/20W resistors.
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