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  1. #1

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    Question Low frequency phase shift with LSI 15 xover

    My question is as follows:
    I have a Sony ES DA9000ES, which is a digital receiver. Analog amps have a phase shift at low frequencies. Does the crossover in the LSI 15 correct for this? If so, how much of a shift occurs? The DA 9000 has the ability to adjust the phase shift according to the speaker attached, but no information is provided to help sort it out. I suspect that there is some phase shift, as the mid bass seems a bit warm with the amp. i'm trying to figure out what to set the low frequency adjust on the 9000 at. Thanks for any help provided.

    Kind Regards,
    Keith

  2. #2

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    I'm not sure where you got that info, but here's a snipet from 6 Moons about it. "NuForce also claims that all amplifiers use output filters and induce phase shift. Again, not true. Class D amplifiers must use filters but traditional linear amplifiers do not. Well-designed linear amplifiers don't suffer phase shifts but ICEpower for example does inject -70 degrees @ 20kHz/4-ohm for one of their boards as imposed by the output filter. The NuForce claims thus do apply to their direct competition -- so-called digital Class D amplifiers -- but not to traditional 'linear' amplifiers."

    So, it would seem that your AVR is the one that has a phase shift, hence the adjustment feature I suspect.
    'Political Correctness'.........defined

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  3. #3

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    Thanks fo the response, but disagree with your post. I got the information from the Sony Technical white paper on the amp, which is posted as follows:

    "DC Phase Linearizer
    Digital amplifiers like the S-Master Pro design can be highly accurate—in
    some respects they can even be too accurate. Phase linearity is an issue with
    analog amplifiers and a contributor to analog sound. When you connect a realworld
    amplifier to a real-world loudspeaker, the interaction causes significant
    departure from phase linearity at frequencies below 30 or 50 Hz. Sony studies
    show a typical deviation from linear phase of about +90 degrees. While not
    making the bass any louder or softer, this shift does have a subtle effect, creating
    warmer and more accessible bass.
    The low-frequency phase response of the typical analog amplifier
    departs from linearity at about 30 to 50 Hz. Because many audiophiles
    are accustomed to seeing frequency plotted against amplitude in
    decibels, this may look like a bass boost. It is not. It's a change in
    phase, which is much more subtle.
    Because this phase shift is common across many brands of amplifiers at
    many price points, the shift has a broad effect on loudspeaker design.
    Consciously or not, loudspeaker designers take this phase shift into account
    when they fine-tune the sound of their products.
    This raises an interesting dilemma. Should a new digital amplifier
    incorporate this phase shift or leave the sound in its original state? After
    extensive listening tests, Sony decided to give users the choice of applying an
    equivalent phase shift in the digital domain, using a dedicated Digital Signal
    Processor, the Sony CXD9776Q. This LSI adjusts low-frequency phase with
    internal accuracy equal to a 65-bit process. We call this circuit the DC Phase
    Linearizer, because it "restores" low-frequency phase, emulating the signal that
    the speaker would get from a top-quality analog amplifier.
    +90
    30~50 Hz
    -90
    0
    Phase
    Frequency
    DC (0 Hz)"

    So, I ask again, does the LSI 15 xover set up for this?

    Kind Regards,
    Keith

  4. #4

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    I'll answer your question first, I have no idea. Try contacting Polk for that one. About your response and no disrespect to you, but Sony is the last company I would look to for answers about audio. Perhaps they were referring to some of their own ill designed power products, but "well-designed linear amplifiers don't suffer phase shifts."
    'Political Correctness'.........defined

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  5. #5

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    Well, I did some research about low frequency phase shift (at 20 Hz) on the net, and even a well designed amp connected to a speaker can indeed have a phase shift of up to 90 degrees. So, while you may not trust Sony's explainations, this issue appeas to be valid. So far, adjusting this setting seems to make a subtle difference in the listening room used. I'm just trying to figure out what the design of the xover is, and what phase shift is designed at low frequencies.
    As a side note, I do not trust hype from any company that is not independently validated. Amps in general need to interface (impeadence and power match) well with a given set of speakers to achieve good listening results. I can say that with the LSI's, they sound outstanding with the DA 9000ES driving them. I have tried similarly priced receivers from other companies, and the 9000ES seemed to have the clearest overall sound with all types of material. I suspect the reason for this is the i-link interface, which has a built in anti -jitter circut, along with the amp design itself.

    Happy listening!

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    Always good to research. Let's say that there is a phase shift at 20Hz. It's a rather mute point as 99% of the speakers out there will never hit that low including the LSi 15's. Probably 50% or more will never hit 30Hz either.

    As stated before, contact Polk for the info you seek.

    Enjoy!
    'Political Correctness'.........defined

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    I believe that phase inversion happens in the output stage of the equipment, not at the speakers. This may be true if you have an active speaker, with EQ adjustablility, but that's a no-brainer.

    I know a couple of folks that this option, phase inversion, is very important but they also have extraordinary speakers.

    I use a phase inverting pre-amp, but the difference is VERY subtle and is more recording based than the actual setup. I think Russman told me something about phase inversion being common in gear, but that it's reverted back to absolute phase internally, prior to the output stage. He may correct me if I'm incorrect.

    That's all I know, good luck in whatever you find out.

  8. #8

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    Ok, I'm going from memory here, but I think class D amps experience phase shifts at low freq, but this doesn't keep them from makeing good sub amps because it's typically consistant across that frequency range. AB amps, on the other hand experience phase shift more on the high end, and not as extreme. I went and dug up my bryston manual when I saw this thread and it shows a +12 degrees at 20 khz and maybe -0.3 degrees at 20hz.

    That said, I'm pretty certain that the LSi's don't have any correction, nor would it's presence predict a better sound in your room. In room bass response is what you care about and every room is going to induce far more of a difference than a few degree phase shift. So, try it both ways, find which one sounds best, then move on to bigger and better tweaks.

    This is all I have to say about overall phase inversion: Meh. I've never heard a difference, but if it floats your boat, flip around your speaker wires.
    Last edited by unc2701; 09-10-2006 at 10:52 PM.
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    A lot less reading (white papers) and a lot more listening. Knowledge is fantastic, but experience is golden. There are lots of specs that measure one way but don't follow when listening to you favorite music. Take your own advice and do some happy listening.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  10. #10

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    One last thing to consider is your room acoustics and listening position will cause more phase shift issues than any quality speaker cross-over. So even if you corrected (if it needed it) the speaker crossover how are you going to fix the position of your ears and your room dimensions and the associated phase issues?
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

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