trying to figure out which speaker set here is more powerful

[bhome83]

i have these altec lansing speakers im using now on my new computer. here are the specs of them: http://support.ap.dell.com/docs/acc/ACS495/

i know they are old but was wondering how these speakers compare to some new ones im going to buy for my older computer that needs speakers. they are the logitech z340 speakers.
http://www.staples.com/Catalog/Brows...e=1&SKU=471308

i looked at the specs of the altec lansing ones but don't understand which ones have more wattage and just are better overall. the altec lansing ones say:

Subwoofer
40 W at 0.8% THD
20 W at <0.8% THD
Satellites
5 W RMS per driver
20 W total at <0.8% THD

so is the subwoofer 20W or 40W? not sure how to read this. what is the total wattage for these then? the logitech speakers have a total wattage of 33. thanks for helping.

[glc]

I could write a book here, but I won't. Bottom line - forget the wattage. Speakers are subjective, it's what sounds best to YOUR ears in YOUR room. Altec and Logitech are both quality manufacturers.

[audiyoda]

I'll agree with glc -- who cares about wattage. It's a combination of wattage, speaker efficiency/design, quality of speaker cables, and amplification that give you the sound you are looking for.

More and more "multimedia" speakers are being rated in RMS -- which is good. But can still be decieving to a certain extent. Klipsch still rates theirs in MBP (Max. Burst Power) -- they seem to think it's a 'better' way to rate a speaker. I say it makes the buggers look on paper like they are louder than they really are. Recently, the FTC has gone after companies that don't report "continuous power ratings" for speakers so now Klipsch has disclaimers saying:

Maximium Burst Power indicates the actual power this amplifier will deliver to the speakers under normal operating conditions. While the FTC power rating indicates power available on a continuous, long-term basis, multi-channel systems do not rely on that type of power. Instead, the amplifier is called upon to deliver large, short-term bursts of power to be able to support today’s digital music, games and movie formats. In addition to the required FTC power rating, we have provided the maximum burst output as a better indication of the product’s true performance.

What I'm getting at in a few more words than glc is that quality companies make quality multimedia speakers. Don't expect them to out-perform true component speakers -- they just can't. But Altec Lansing, Logitech, Klipsch, Boston Accoustic, Harmon Kardon, Creative Labs, Yamaha and Sony will all give you quality and very good sound.

-Craig

[sam21]

I don't know,I might have to disagree.In my short career in car audio.Some of the most important issues are the RMS wattage,MBP,frequincy range,and of course brand reliability.

But I know nothing about PC audio...

[TwoRails]

Specs are almost meaningless if the manufacturer is not quality themselves. For example, I've seen PC speakers that weigh less than a pound but yet claim to have 500 watts of power. Yeah, right.

Specs are good for comparison only when you're comparing oranges-to-oranges, which is rarely the case any more. It's like comparing horsepower. You can't compare a 1 1/2 HP vacumn motor with a 1 1/2 HP table saw motor. An other example is my shop radio: it's speakers are rated at 200W rms, but I'll guarantee you that I'd blow them apart if I hooked them up to my 200W house amp.

Like mentioned above, it's a subjective thing. Each PC speaker system has it's own "flavor" of tonal quality. Even comparing speakers in the same price range can be difficult. How can you compare satellite speakers on paper that have the same power rating and distortion if one has both a mid-range and a tweeter, and the other has a tweeter only? You can't. You'll have to listen to them, but I'd guess the one with a mid-range and tweeter would sound better from previous experience.

Distortion is also a very grey area for a couple of reasons. The biggest reason is that most people can not tell the difference between 5% and 1% distortion, let alone the difference when both specs are under 1%. While lower distortion is a good indicator that it is higher quality, that doesn't mean it will sound better.

[audiyoda]

Let me see if I can clear up this "power" thing:

First, what is "power"--> Power is energy per time. It is measured in watts. Power delivered by an amplifier to a load (speaker) is normally determined by dividing the voltage (V) squared by the impedance (Z) :

Power = v(2)/Z

The resulting type of power will depend on what voltage we use. If peak voltages are used, then the result is peak power. If RMS voltages are used, then average power (often wrongly referred to as "RMS") is obtained. RMS (root-mean-square), is only a mathematical method to extract the mean value of an alternating signal (one with negative as well as positive values).

I know, YIPPIE!! For most people that's a bunch of mumbo-jumbo. How does that equate to real life?....There are four ways speakers are rated:

RMS: Abbreviation of Root Mean Square. Mathematical transformation that extracts the mean level of an alternating signal. A more common usage of RMS would be Continuous RMS power -- It's the spec that really tells you how powerful an amplifier is. RMS power is expressed in watts. A typical specification might read 100 watts RMS into 8 ohms from 20Hz-20KHz at .01% THD. What this means, basically, is that the amplifier will deliver 100 watts into an 8 ohm speaker from 20Hz to 20Khz. This frequency range is basically the entire audio range that an individual can hear.

Dynamic Power: This is a test of the amplifier's ability to go beyond its continuous RMS power for a very short time period. We are not talking minutes or even seconds here. We are talking milliseconds or thousandths of a second. A musical transient peak, such as a cymbal crash lasts only a very short time. Dynamic power is usually measured into 8 ohms, but specifications are generally also published for 2, 4, and 6 ohm loads as well. To keep things from getting too complicated, we will concentrate on the 8 ohm figures.

To measure dynamic power, an amplifier is fed a 1000 Hz signal for 20 milliseconds, then allowed to rest for 480 milliseconds. The amplifier volume control is turned up until the amp reaches the clipping point. At that point, the amp has reached its instantaneous peak or dynamic power output. Like the continuous power rating, dynamic power is expressed in watts. The figure is usually significantly larger than the RMS power rating, and should not be confused with the continuous power ratings of the amplifier. A dynamic power rating into a figure such as 1 or 2 ohms does not mean that the amplifier can drive a speaker with a 1 or 2 ohm rating continuously. If you attempt that, the amplifier will either go into the protection mode or possibly cause damage. Dynamic Power is similar in many ways to:

PMPO: Abbreviation of Peak Music Power Output. Expression of the power output of an amplifier by means of the the maximum power it can supply even in the shortest duration. That's why you see junky little speakers rated at 500W. They forget to tell you it's rated in PMPO. PMPO and Dynamic Power are very similar -- the biggest difference is that PMPO is a theoretical measurement with no real world testing behind it. In theory, a 10W RMS amp can supply 500W PMPO under perfect conditions -- conditions only found in a lab and the output would only last milliseconds -- the amp would blow out.

MBP: Abbreviation for Maximum Burst Power. This is basically a Klipsch thing -- there's no reference to it in any of my AES (Audio Engineering Society) books.

Of all of these, RMS and Dynamic Power are the only ratings accepted by the AES as a reference to how powerful a amplifier is. To the AES, PMPO is a joke. And to most AES members, Klipsch and their MBP is a joke -- especially since they only rate their multimedia (ProMedia) speakers with MBP. Their commercial/professional equipment and their consumer grade home theater equipment uses RMS to rate power.

So, how does Total Harmonic Distortion play into all of this? With mulitmedia speakers, it really doesn't. THD is the amount of distortion the amplifier will introduce into the original signal. Any high quality amp made today has extremely low distortion ratings. The human ear cannot hear anything under 2%. For the most part, when you are considering purchasing an amplifier, you can disregard the THD specifications.

So we're back to how good is the company that's making your speakers. And like I (glc and Two Rails) said, it's a combination of quality manufacturing and your ears.

-Craig

[TwoRails]

Excellent post, audiyoda !!

This is one I'm bookmarking for the superb explaination.

TwoRails

[DrZaius]

Great post, thanks for the "power primer" audiyoda.