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  1. #1

    Default Does 40 hz mean 40 hz?


    So if a receiver states that it's output is from 40 hz to 20 khz, does this mean that the bottom end only goes down to 40 Hz even if a subwoofer is hooked up to the sub out line?

    Here's the blurb from a receiver and it seems strange that the receiver would be limited to 40 Hz and not 20 Hz, like other receivers.

    -100 Watt @ 6 ohm, 40 Hz - 20 kHz, THD: 0.9%

    Would this be a problem??

  2. #2
    Join Date
    Oct 2005
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    Sacramento, CA
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    695

    Default Re: Does 40 hz mean 40 hz?


    > -100 Watt @ 6 ohm, 40 Hz - 20 kHz, THD: 0.9%

    > Would this be a problem??

    I think for most people, at least most of us here, this would be a problem.

  3. #3
    Join Date
    Sep 2005
    Posts
    6,251

    Default Power Supply


    > So if a receiver states that it's output is
    > from 40 hz to 20 khz, does this mean that
    > the bottom end only goes down to 40 Hz even
    > if a subwoofer is hooked up to the sub out
    > line?

    > Here's the blurb from a receiver and it
    > seems strange that the receiver would be
    > limited to 40 Hz and not 20 Hz, like other
    > receivers.

    > -100 Watt @ 6 ohm, 40 Hz - 20 kHz, THD: 0.9%

    > Would this be a problem??
    It just means it has a wimp power supply for the main amp. The sub out should not be affected.



    (Originally posted by: djk)

  4. #4
    Join Date
    Oct 2005
    Location
    Sacramento, CA
    Posts
    695

    Default Re: Power Supply


    > It just means it has a wimp power supply for
    > the main amp. The sub out should not be
    > affected.

    Is that what it means? Hmmmm... Girlie man's amp.


  5. #5
    Join Date
    Nov 2005
    Location
    Silver Spring, MD
    Posts
    1,611

    Default Re: Does 40 hz mean 40 hz?


    > -100 Watt @ 6 ohm, 40 Hz - 20 kHz, THD: 0.9%

    This is only for the amplified signal / powered outputs on the receiver. Pre-amp signals should be as full-range as the source of your audio.

    BTW- .9% THD is not an impressive spec, what amp is this anyway?

  6. #6
    Join Date
    Jul 2006
    Location
    Wisconsin
    Posts
    525

    Default JVC RX-316 on Ebay $40.00 *NM*




  7. #7

    Default In this case: No.


    > -100 Watt @ 6 ohm, 40 Hz - 20 kHz, THD: 0.9%

    They have chosen to show off the 100W quantity (Anything less than "100W" is not respected by the ignorant consumer mob) and the 6 ohm rating. To do that, they had to limit the signal to 40Hz and above, and the THD is already high. If they had lowered that to 20Hz, the THD would be even higher, and/or the power output would be lower. If I were them, I would have rated it into 8 ohms. At least the THD would look better.

    Granted, this may be quite a shi**y receiver, but it will still play something lower than 40Hz.

  8. #8

    Default Re: Does 40 hz mean 40 hz?


    As mentioned by Damkor, the receiver will still play 20-20k, but they just decided to play games to meet the 100 watt power specification.

    I've used a few JVC receivers in the past, and honestly, I don't know how they even get those numbers with the fudging that they do. My JVC as well as ones owned by college buddies, had pitiful output capabilities. Mine was "rated" for 70x3 and some lower amount for the surrounds, and even in 2 channel mode it's a pig. With my 6 ohm Cerwin Vegas, I couldn't squeeze even moderate output levels out of it before it would go into protection. With higher impedance speakers, it wouldn't go into protection, but it would clip at low to moderate output levels.

    I own other inexpensive receivers, including a 50 watt onkyo, a 100 watt sony, and a 100 watt magnavox. All of them provide substantially more clean output power than the JVCs I've used, though the magnavox can't handle anything below 8 ohms with any dignity.

    If you're looking for a bedroom receiver that's going to power a pair of bookshelf speakers, that JVC will do just fine. If you're after anything more ambitious, forget about it.

    > So if a receiver states that it's output is
    > from 40 hz to 20 khz, does this mean that
    > the bottom end only goes down to 40 Hz even
    > if a subwoofer is hooked up to the sub out
    > line?

    > Here's the blurb from a receiver and it
    > seems strange that the receiver would be
    > limited to 40 Hz and not 20 Hz, like other
    > receivers.

    > -100 Watt @ 6 ohm, 40 Hz - 20 kHz, THD: 0.9%

    > Would this be a problem??


  9. #9

    Default Re: Does 40 hz mean 40 hz?


    > This is only for the amplified signal /
    > powered outputs on the receiver. Pre-amp
    > signals should be as full-range as the
    > source of your audio.

    > BTW- .9% THD is not an impressive spec, what
    > amp is this anyway?

    The specs. are for a Panasonic Surround receiver.
    (Here's more info.)
    <A HREF="http://www.epinions.com/pr-Receivers...ay_~full_specs">http://www.epinions.com/pr-Receivers...ay_~full_specs</A>

  10. #10
    Join Date
    Sep 2005
    Location
    North TX
    Posts
    2,113

    Default Re: Does 40 hz mean 40 hz?


    > -100 Watt @ 6 ohm, 40 Hz - 20 kHz, THD: 0.9%

    Translation: 53 watts per channel at 8 ohm 20-20k at similar (or better) distortion.

    How to arrive at this? Take 6/8 of the power to account for impedance, and divide by the square root of two for power supply droop (which happens more at low frequency). Real figures may be a bit better than this, but I wouldn't count on it.

  11. #11

    Default Re: Does 40 hz mean 40 hz?


    Then scale back the power until the THD spec is reasonable and you start to see a much more accurate picture of what this thing can (or can't) do.
    > Translation: 53 watts per channel at 8 ohm
    > 20-20k at similar (or better) distortion.

    > How to arrive at this? Take 6/8 of the power
    > to account for impedance, and divide by the
    > square root of two for power supply droop
    > (which happens more at low frequency). Real
    > figures may be a bit better than this, but I
    > wouldn't count on it.


  12. #12
    Join Date
    Sep 2005
    Location
    North TX
    Posts
    2,113

    Default Re: Does 40 hz mean 40 hz?


    > Then scale back the power until the THD spec
    > is reasonable and you start to see a much
    > more accurate picture of what this thing can
    > (or can't) do.

    Distortion in a cheap amp may not be much better than .5%, even at 1 watt. Most cheap receivers don't even have provision for setting the output stage bias. And I've 'improved' a lot of car amps and such just by hand trimming it with resistors from B to C on the Vbe multiplier. It makes a world of difference in distortion at all power levels. In any case, with distortion figures quoted around 1%, usually they're driving it into clip for the power test to show higher numbers.

    If an amp is *really* any good, it will retain its .005% distortion right up until it clips, then go to 1% pretty quickly. Such amps don't have lower distortion numbers just by backing off the power unless they *are* inflating the power spec.

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