The whole POINT was to answer your question about altering the SPL of the woofer relative to the rest of the speaker. That's what it's SUPPOSED to do. The transformer does so without any change in efficiency or the alignment. Yes, it changes the impedance- so what? Let's say you have an 8 ohm nominal woofer that needs a 6dB reduction in sensitivity. Its impedance will vary from (say) 6 ohm below resonance to maybe 30 ohms at resonance to 10 ohms above resonance; these are not atypical numbers. 2:1 stepdown means 4:1 impedance transformation, so the speaker impedance ends up varying from 1.5 ohm below resonance to roughly 8 ohms at resonance to 2.5 ohms above resonance. A decent SS amp will have zero problem with that- its source impedance is low, well under 0.1 ohm. So.. the passive solution works. It's not convenient- a big bass transformer is heavy and bulky, and biamping will be cheaper- but it's absolutely doable if you want a passive solution.
I understand that many years ago B&W used a transformer to lower the sensitivity of the 10" bass unit in their 3 way DM6 (also known as "The Pregnant Penguin". If you ever see a photo of a gloss white version you'll see why.). The cross over was published somewhere here a year or two ago.
Edit; and just for completeness the thread is; DM6 Recap. Post #1 24 June 2011.
Jonathan
Edit; and just for completeness the thread is; DM6 Recap. Post #1 24 June 2011.
Jonathan
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Why would Linkwitz say this as a simple "Case closed" statement if it wasn't true? He is an an authority on active vs passive if there ever was one. Yet he claims that the reason is quite simple..
"Crossovers may be implemented either as passive RLC networks, as active filters with operational amplifier circuits or with DSP engines and software. The only excuse for passive crossovers is their low cost. Their behavior changes with the signal level dependent dynamics of the drivers. They block the power amplifier from taking maximum control over the voice coil motion. They are a waste of time, if accuracy of reproduction is the goal."
"Crossovers may be implemented either as passive RLC networks, as active filters with operational amplifier circuits or with DSP engines and software. The only excuse for passive crossovers is their low cost. Their behavior changes with the signal level dependent dynamics of the drivers. They block the power amplifier from taking maximum control over the voice coil motion. They are a waste of time, if accuracy of reproduction is the goal."
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Hardly an irrefutable source? He knows at least as much about crossovers as you do about HOMs. Maybe even more..(Trying to be funny. Kind of.)
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I don't care. 🙂
I have "passive" capacitors in series with tweeters, LC filters for woofers and for subwoofer, but before corresponding power amps. Digital Audyssey does for me the rest.
I have "passive" capacitors in series with tweeters, LC filters for woofers and for subwoofer, but before corresponding power amps. Digital Audyssey does for me the rest.
Are you serious?
An externally hosted image should be here but it was not working when we last tested it.
a well designed multi-way passive crossover speaker is much closer to a nominal impedance than a single woofer.
Really? 🙂
So, if SY in order to align SPLs increases inpedance on lows by adding transformer the speaker is no more "well designed", despite it sounds better? 🙂
With as many choices as there are out there for all kinds of drivers why would anyone (who knows what they are doing) choose a woofer with a higher SPL than the mids or tweets for a multi-way passive crossover system and then try to fix that problem with a transformer?
So now you have the DC resistance of both the secondary coil of the transformer and at least one coil in the passive crossover in series with the woofer.
That's very counter productive.
James.
So now you have the DC resistance of both the secondary coil of the transformer and at least one coil in the passive crossover in series with the woofer.
That's very counter productive.
James.
You don't have to have drivers with the same impedance in a passive speaker. IE- 4 ohm woofer, 8 ohm mid, and 6 ohm tweeter is perfectly doable.
Later,
Wolf
agreed, provided there is no need to match source/load as in tubes that use transformers and rely on impedance reflection to transfer max. power, although the significance would not be tat important given the outrageous speaker behaviour - impedanc wise.
its not about drivers having different impedances
like you say, no problem at all
its the varying impedance of each driver
that is real big problem, and plays a major role with passive crossovers
active is not troubled with this
That's only a problem if you want to use textbook formulas and topologies, rather than modern CAD methods and a bit of creativity about compensation.
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