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Stereophile's recent review of the Vienna Acoustics Beethoven Grand suggested that the woofers were likely wired out of phase.Are there situations where this is advisable? It seeems "wrong."
But what do I know!?
Thanks for any insight,
Hukk
Follow Ups:
For each order, high-pass filters vary from 0 to 90 degrees of phase lead (45 degrees at the pole) as they move from pass to stop band and low-pass filters vary from 0 to 90 degrees of phase lag (45 degrees at the pole).With second order filters the high and low-pass outputs are 180 degrees out of phase at all frequencies. The polarity of one output must be inverted if you want any output.
First order cross-overs have a 3dB peak 15 degrees below axis; third order cross-overs have a 3dB peak 15 degrees above axis. Inverting the polarity of one output flips the peak (but means the first order cross-over is no longer transient perfect).
Fourth order filters have the inputs and outputs 360 degrees out of phase which is to say in-phase for continuous tones. Flipping one output will eliminate most output.
Of course, this assumes that the driver acoustic centers are aligned on the Z-axis which will not be the case (look where the tweeter dome is vs. a midrange cone). That causes a tilt in polar response arround the cross-over region which interacts with the cross-over tilt.
Depending on the crossover topology, sometimes drivers HAVE to be wired out of phase or there will be a severe dip at the crossover frequency.
Additionally, if physical placement of the drivers on the baffle tilts propagation direction, reverse electrical phase can offset that lobe tilt so that final acoustic propagation is forward rather than tilted. What is *right* is the final acoustic result, not how it is electrically accomplished. Vance Dickasons's Loudspeaker Design Cookbook 6th edition is currently on sale @ madisound.com for only $11 because the 7th edition is now in print ($39); this technical book would make an inexpensive education per loudspeaker design fundamentals.
Thanks !!!! Great discount on a very useful book.
The final acoustical phase result is what really matters and is what will make the crossover most effective. What folks usually forget about is time. If the tweeter is set back too far, yet the crossover adjusts for the phase for smooth FR, it still won't sound right. Traditionally, the tweeter is ahead in time which, to me, isn't perfect either. Why would you want to start hearing the harmonics before the fundamental? That's what's happening if the tweeter's acoustic center is in front of the mid/woofer.
I have to laugh at some of these magazines and their obsession with in-phase driver connections. When a novice like me knows this isn't always the case, makes the mags look pretty foolish.
I *was* going to ask if I would risk harming anything by reversing phase on my woofers (I own the previous generation Beethovens).But given these comments it sounds like I have little to gain by experimentation in this direction.
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