hi birkett7!
Here are some sources which should help you. I think the "best way" to
do this really depends on how accurate you need the results to be, how
much you intend to spend on a measuring device, and what kind of
comparisons you wish to analyse, and in how much detail.
----------------------------
"It is a very simple thing to measure wattage, using even a simple
Volt/Ohmeter. Of course, the better the meter, the more trustworthy
the resulting measurement. Here's how to do it. Set your VOM to it's
very lowest AC scale. This will usually be 10 volts on an inexpensive
meter. Then, play some music through your system with fairly steady
rhythm patterns so that the peaks will be more easily observed on the
meter. Crank it up to a decent volume, as loud as you can stand, and
then measure the voltage across the speaker outputs. The meter will be
swinging in "VU" fashion, but you can easily obseve the highest peak
readings with some practice. Note this measured AC voltage. it will
represent the "RMS" voltage of your audio signal. Square this number
(multiply it by itself) and divide the result by the speaker
impedance.
Example: Your meter is peaking right at 6 volts so you square this
reading for a total of 36. Your speaker impedance is known to be, say,
4 ohms so you divide 4 into 36 and you get 9. In this example, the
system would be supplying 9 watts RMS [Root Mean Squared].
Now, once you master this technique, you will surprise yourself by
trying to guess how much power you are listening to! No doubt, if you
are new at this, you will assume your system is putting out a hundred
or more watts at that 9 watt level! That is, if indeed, you can get it
to actually acheive 9 watts or stand to listen to it long enough to
measure it while it is putting out this level of power (assuming an
efficient speaker of course!)."
http://www.davisound.com/TB8.html
----------------------------
Here are a few test instruments that can be used:
Fluke Power Harmonics Analyser
"Measure rms, peak and total harmonic distortion (THD) for complex
voltages and currents - with no manual calculations required"
http://www.testequipmentdepot.com/fluke/powermeter/39and41b.htm
Fluke website: http://www.fluke.com/
Global Specialties 1521
"The 1521 Autoscan True RMS AC power line analyzer is a
state-of-the-art instrument, ideal for providing all the necessary
information about any electrical load connected to the AC line. It
monitors/scans sequentially all electrical parameters, i.e., voltage,
current, power, VA, power factor & line frequency, thus providing a
clear picture of the load."
http://www.globalspecialties.com/1521.html
Watts Up?
"Simply plug any device into Watts up?, and the meter instantaneously
displays the wattage being used, as well as the cost, in dollars and
cents....Watts up? measures the voltage and current thousands of times
a second so it has an incredibly fast response time which enables you
to "see the surge" of power when appliances are first turned on. The
peak value display captures this surge so it is displayed even if it
happens too fast to see live. The minimum voltage display shows the
line quality and voltage dips. Minimum current and minimum watts can
be used to monitor variances in appliances that run continuously.
Watts up? measures true RMS power (including power factor) which is
what utilities charge for."
https://www.doubleed.com/products.html
Dranetz-BMI has long been recognized as the world's number one source
for power monitoring equipment and services. From versatile handheld
power quality monitors used for portable troubleshooting applications,
to permanently installed systems for continuous power quality process
improvement. Click here for Dranetz/BMI products:
http://www.dranetz-bmi.com/products/products.cfm
There are a number of other products that measure & analyse - you can
view a list here:
http://www.euroelec.ie/products.htm
----------------------------
Search terms used:
stereo "measure wattage"
"measure wattage"
"measure wattage" rms
----------------------------
I hope you find this information useful.
regards,
Jack |
Request for Answer Clarification by
birkett7-ga
on
15 Apr 2003 05:27 PDT
I'm sorry, I don't think I specified my question well enough. What I
meant was, how to compare different stereos do see what is the
loudest. I know the basic measure is through watts, but there are more
specs involved that will judge the power of sound versus watts alone.
Specifically, I'm trying to see what is the loudest: Bose Lifestyle
5/20, Sharper Image Vertical 4CD, Nakamichi Sound Space 5 and Sony MHC
GX8000. I"m willing to pay more for answer. Thank you!
|
Clarification of Answer by
jackburton-ga
on
15 Apr 2003 09:36 PDT
Hi birkett7,
Thank you for your clarification.
I have contacted a professional audio writer who reviews CD players,
turntables, amplifiers, preamplifiers, speakers, and assorted
ephemera. In response to your query, he advises:
------------------------------
"Purchase a Radio Shack sound level pressure meter. They come in
analog (needle on a scale) and digital (LCD readout) models. I use the
digital model, Catalog No. 33-2055.
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=&product%5Fid=33%2D2055
Use the same recording for each measurement (very important) and turn
up the volume as loud as you can stand it. The "loudest" system will
record the highest sound pressure level, measured in decibels of sound
pressure level (dB SPL).
A couple of caveats, however. First, "loudness" is not a particularly
effective measure of the fidelity of any sound system. I can show you
speakers that are plenty loud, but sound terrible--and a great deal of
what you're measuring is the effectiveness of the sound output, that
is, the ability of the speakers to be, well, loud.
Second, "watts RMS per channel" (wpc RMS) is not a reliable measure of
how loud something can go. Yes, it's true that a 300 wpc amplifier can
blow away a 20 wpc amplifier, but in real world listening
applications, neither is using much more than 5-10 wpc at any given
time. The extra oomph that the more powerful amplifier gives you is
for musical peaks at very (very, very) high volumes. Further, there
are 3 and 9 wpc tube amplifiers (called "single ended triodes") that
can, using the right speakers, blow away conventional 300 watt
amplifiers. That is, they will be louder. Finally, after 60 wpc +/-
the ability of sheer power to made things louder diminishes
considerably; that is, 300 wpc isn't going to be five times as loud as
60 wpc. You want the extra power in this case for very big, very
inefficient speakers who require a lot of power to produce realistic
live orchestral sound levels.
If what you desire is volume (loudness--not the same but close
enough), then my suggestion is to invest in a good receiver with 60+
wpc RMS continuous output and a couple of good, efficient speakers (90
dB or higher) whose dynamic range is in the 50-20K hertz range. You'll
be able to play music louder than you can imagine, and you'll achieve
higher fidelity to boot. The shelf or "one box" systems that you've
mentioned are all very nice, but they're also all very expensive. You
can achieve big time loudness at considerably less cost. If you're
interested in alternatives (models and prices), tell me what your
budget is, what your listening habits/goals are (please distinguish
between music and home theater--each has different requirements), and
I'll put together a list of recommendations for you."
------------------------------
Here some links you may find useful:
"Choosing a Mini Audio System"
http://www.epinions.com/elec-topic-Audio-Systems-Buying_Guides-How_to_Choose-a_mini_audio_system
"Choosing Stereo Separates"
http://www.harmanaudio.com/all_about_audio/choosing_separates.asp
------------------------------
I hope this helps!
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