Re: A Comparison


"ScottW" <ScottW48@xxxxxxxxxxx> wrote in message
news:1129918763.423959.232410@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> normanstrong@xxxxxxxxxxx wrote:
>> "Sander deWaal" <nospam@xxxxxxxxxx> wrote in message
>> news:e2kfl1pqc1sf09gdstgmbme6cbed47001l@xxxxxxxxxx
>> > "nyob123@xxxxxxxxxxxx" <NYOB123@xxxxxxxxxxxx> said:
>> >
>> >>Krell 350 Watt monoblocks @ $17,500.00 per pair
>> >>350 watts wpc @ 8 Ohms
>> >>700 wpc @4 Ohms
>> >>1400 wpc @ 2 Ohms
>> >>Signal to noise = 118db 95 db @ 2.83 V
>> >>THD = .05% 20 Hz - 20 kHz
>> >>Input Impedance = 100 K Ohms
>> >>Input Sensitivity = 2.6v RMS for max power
>> >>Voltage gain = 26.4 db
>> >>
>> >>---------------------------------------------------------------------------------
>> >>QSC PLX 3402 Stereo amp $1200.00
>> >>700 wpc @ 8 Ohms
>> >>1100 wpc @ 4 ohms
>> >>1700 wpc @ 2 ohms
>> >>Signal to noise 107 db
>> >>THD = .03% 20 Hz - 20 kHz
>> >>Input Impedance = 6 K ohms
>> >>Input sensitivity = 1.9 Volts @ 8 ohms
>> >>Voltage gain = 32 db
>> >
>> >
>> > One of the things that I noticed immediately is the ability of the
>> > Krell to deliver twice the power (meaning current) in half the load,
>> > up to 2 ohms.
>> > I suspect that even in 1 ohm the figure would be close to the required
>> > 2800W, be it for a brief period of time.
>> > The QSC has only marginally more power into 2 ohms (not that those
>> > insanely high wattages have any meaningful use, you will note).
>> > Also, the current doesn't double with half the load.
>> > This means the Krell has a stiffer power supply, despite the lower
>> > average wattage. It is a true constant voltage source.
>>
>> You've jumped to a conclusion that's not borne out by the figures. The
>> power output into a variety of load impedances is simply part of the
>> spec.
>> It does not mean that the power output of the Krell will double just by
>> changing the load from 8 to 4 ohms.
>
>
>
> BS. Power output is either current limited or voltage limited.
> Obviously into an 8 ohm load the amp is voltage limited. The QSC is
> also voltage limited into 8 ohms but becomes current limited into 4
> ohms.
> IF the QSC is driven to max output into 8 ohms with 1.9 V rms input it
> will suddenly find itself current clipping if that load is increased to
> 4 ohms. The max input is now only 1.7 V rms. Since the gain is the
> same the useful dynamic range of the amp is reduced.
>
>> In other words, it has nothing to do
>> with the "stiffness" of the power supply.
>
> I guess we differ on the meaning of "stiffness". In my opinion...
> the power (current and voltage) capability of an amp is very dependent
> on its power supply.
>
>>
>> What it DOES mean, on the other hand, is that the Krell is a 1400W
>> amplifier
>> designed for optimum performance into a load of 2 ohms or less. Since
>> the
>> output is voltage limited, it's an inefficient amplifier choice for an 8
>> ohm
>> speaker.
>
> Excess current capacity may bother you, I like it. It makes the amp
> more versatile and acceptable for use with virtually any speaker. The
> QSC suffers degraded dynamic range with load and the specs also show it
> suffer increased THD into 4 ohm loads as well.

We're not disagreeing here Scott. I've simply chosen to emphasize the
inefficiency of the Krell when driving an 8 ohm load; you're pointing up the
versatility of the Krell into a variety of loads. If this versatility came
for free, I'd be all for it. As it is, the result is a $17,000 amplifier,
which to my way of thinking is more or less absurd.

Norm


.

Relevant Pages

  • Re: A Comparison
    ... >>> in half the load, up to 2 ohms. ... >>> The QSC has only marginally more power into 2 ohms (not ... >>> This means the Krell has a stiffer power supply, ...
    (rec.audio.opinion)
  • Re: A Comparison
    ... >>> Krell to deliver twice the power in half the load, ... the current doesn't double with half the load. ... >> changing the load from 8 to 4 ohms. ...
    (rec.audio.opinion)
  • Re: A Comparison
    ... The power output into a variety of load ... >> changing the load from 8 to 4 ohms. ...
    (rec.audio.opinion)
  • Re: Standing-Wave Current vs Traveling-Wave Current
    ... It would be correct for measurement at the load and at every point 1/2 wavelength back to the source from the load, because the standing wave has the same measurements at these points. ... we would also be measuring a reactive component that could be described as the charging and discharging of the capacity or inductive component of the transmission line. ... The inclusion of this reactive component would invalidate the power reading if we were assuming that the measured power was all going to the load. ... ohms resistive and a reactance of 83.33 ohms. ...
    (rec.radio.amateur.antenna)
  • Re: Standing-Wave Current vs Traveling-Wave Current
    ... It would be correct for measurement at the load and at every point 1/2 wavelength back to the source from the load, because the standing wave has the same measurements at these points. ... we would also be measuring a reactive component that could be described as the charging and discharging of the capacity or inductive component of the transmission line. ... The inclusion of this reactive component would invalidate the power reading if we were assuming that the measured power was all going to the load. ... ohms resistive and a reactance of 83.33 ohms. ...
    (rec.radio.amateur.antenna)
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