Speaker Spec's for dumbies

[markER717]

Okay well I know pretty much jack all about sound systems and some of you guys seem to know a hell of a lot. So what im asking is, could you guys just give me a little explanation on some terms using to describe speakers and answer some questions. Like for example: wrms? and whats a decent wattage for subs? whats a 'monoblock' amplifier'? and any other term you can bring to speakers that I wouldn't know(thats pretty much everything) I am really eager to learn more about this sorta stuff, but I just need a little but of help.

[Haydz]

now thats saying something.

cant even spell dummies

for more info on car audio search mobile electronics in google. that site has alot of good car audio info.

good luck mate

[Philthy]

Okay well I know pretty much jack all about sound systems and some of you guys seem to know a hell of a lot. So what im asking is, could you guys just give me a little explanation on some terms using to describe speakers and answer some questions. Like for example: wrms? and whats a decent wattage for subs? whats a 'monoblock' amplifier'? and any other term you can bring to speakers that I wouldn't know(thats pretty much everything) I am really eager to learn more about this sorta stuff, but I just need a little but of help.

I'll give a few of these a go, but maybe someone could do a decent write up on this and it could become a sticky.

"Watts" is a measure of power. Amps produce power (measured in watts) which is then fed into the speakers/subwoofers. The power rating you see on speakers refers to the amount of power that can be safely fed into them.

Peak power, pmpo, max power etc are the high values you will see quoted by most car audio brands. This is the amount of power an amp can put out (or a speaker can handle) for a very short amount of time without causing any damage. Peak/Max/PMPO all have slightly different meanings as far as I know but someone else will be able to explain them. Most important to know about this value is that it generally doesn't mean squat.

RMS, or WRMS is the "root mean squared" value. Again, someone else will be able to explain the technical side (something about the sine wave), but this is the amount of power that an amp can produce or a speaker can handle continuously, day in day out. This is the value you should always be looking at when matching speakers and amps.

A monoblock amp, contrary to some peoples beliefs is not simply a 1 channel amp, but has different circuitry to multi-channel amps to make them run more efficiently, and generally have a bigger power output, but sacrifice a bit of quality. That makes them will suited to powering subwoofers, which take a lot of power to drive and the lack of high-end quality won't be noticed.

Coaxial speakers have a tweeter (or tweeters) mounted above the speaker cone (on the same axis). This is because a large woofer isn't sensitive to accurately reproduce high frequency notes as well as handle all the mid-bass etc, so a tweeter is needed to give a clear high end. The advantage of coaxial speakers is that you get the better sound quality that a seperate tweeter gives you, yet they are still easy to install in the standard speaker mounts.

The alternative is to use splits, where the tweeter is a seperate unit to the main woofer. In this case, the signal from the headunit or amp is sent into a crossover, where it is split into high and low frequencies. The highs are sent to the tweeter, and lows to the woofer in the door. Splits generally sound better, as there is no interference from the tweeter mounted on the cone, and the tweeter can be mounted anywhere to give you a better sound "stage".

A far as decend wattage for subs is concerned...what do you want your sub to do? If you are just after a bit more punch in the bottom end then I don't look at power ratings at all. Most subs are around 200+wrms, and (in my opinion), this is plenty to just give a but more kick. Then the choice comes down to whatever sub you find suits your music style/budget best.
If you want to be able to cruise down the street setting off car alarms, then you are probably looking more around 800+wrms, and again find the best sub to suit your needs.


Mistakes that I see people make when buying audio gear -
Thinking that speakers with a bigger power rating are going to be louder. No, the volume of your system is determined by the source of the power (amps). Higher rated speakers might be able to handle the higher volumes better, but if the speakers you have can already handle full volume, then thats as loud as you will get.

Thinking the more tweeters in them the better. If you look at entry level speakers you will see anything from 2-way up to about 6-way speakers. This basically is the number of tweeters that are mounted on the cone (mounted "on" the cone probably isn't the right way to put it, but you get the idea). However, if you look at more expensive speakers, you will find that they almost always are simple 2-ways, with just the one good tweeter, and they are guarenteed to sound better.

Buying speakers based on power ratings. Same thing again here. Some of the best speakers I've ever heard were a set of vintage 25(ish)wrms warfdales. Which brings me to my next point...

LISTEN TO THE SPEAKERS BEFORE YOU BUY THEM. Let your ears decide which speakers are the best. It's your ears that have to put up with the decision you make, and sound is a very subjective thing. What sounds good to some people won't always sound good to you. I always get stuck in cars with mates who have the subs up so loud you can hardly hear the music, and they think it sounds fantastic.

But I'm getting off track. There is so much to know about audio. I haven't even touched on different sub boxes, crossovers, low/high pass filters, sound deadening etc.
This should give you something to think about til others add their bits anyway.
And feel free to correct me on any mistakes I'm bound to have made in there

[TMM]

^^ Agreed.

I think the most important thing to consider when buying speakers is that none of the specs will tell you how good a speaker will sound.

[graemevb]

RMS, or WRMS is the "root mean squared" value. Again, someone else will be able to explain the technical side (something about the sine wave), but this is the amount of power that an amp can produce or a speaker can handle continuously, day in day out. This is the value you should always be looking at when matching speakers and amps.

Sort of half right. The rms value is simply the maximum value of the sine wave divided by 1.4, it does not represent a continuous rating Best to look for a continuous rms rating and a specified distortion figure.
ie some amps will have 50 + 50 wrms at 0.01% continuous, and 80 + 80 at 1%, 100 + 100WRMS at 10%. Some will even specify what frequency range that is for, either at 1kHz or for 20-20kHz.
Most head units are rated using an rms fig but at 10% distortion.

Re loudness of speakers, the other spec that matters here is sensitivity. Typically expressed as sound level(dB) at 1 meter from the speaker when measure when 1W is fed into it. Do appreciate that a difference of 3dB here will mean that one speaker needs twice as much power to drive it to the same loudness. ie a speaker rated at 89db/W/m will need twice as much amplifier power as one rated at 92dB/W/m

[graemevb]

^^ Agreed.

I think the most important thing to consider when buying speakers is that none of the specs will tell you how good a speaker will sound.

If the only specs you are looking at are the power figures then that is true.
There are a host of other specs that can give a very good idea of what it will sound like(that most likely wont be written on the side of the box, because the average punter wouldnt know what to make of them), and if speakers test bad in the specs, they will be bad!

[Philthy]

Sort of half right. The rms value is simply the maximum value of the sine wave divided by 1.4, it does not represent a continuous rating Best to look for a continuous rms rating and a specified distortion figure.
ie some amps will have 50 + 50 wrms at 0.01% continuous, and 80 + 80 at 1%, 100 + 100WRMS at 10%. Some will even specify what frequency range that is for, either at 1kHz or for 20-20kHz.
Most head units are rated using an rms fig but at 10% distortion.

Re loudness of speakers, the other spec that matters here is sensitivity. Typically expressed as sound level(dB) at 1 meter from the speaker when measure when 1W is fed into it. Do appreciate that a difference of 3dB here will mean that one speaker needs twice as much power to drive it to the same loudness. ie a speaker rated at 89db/W/m will need twice as much amplifier power as one rated at 92dB/W/m

Thanks for that. I thought all rms ratings were at 0.1% THD, or is that just most speakers that I look at?
And I hadn't thought of sensitivitites when I wrote that...

If the only specs you are looking at are the power figures then that is true.
There are a host of other specs that can give a very good idea of what it will sound like(that most likely wont be written on the side of the box, because the average punter wouldnt know what to make of them), and if speakers test bad in the specs, they will be bad!

Agreed. At the very least I always like to see a reasonably flat response curve on the box, and that alse helps with the setting of crossover and filter points.

As I said though, there are so many things to look at and 90% of people wouldn't understand half of them so its much easier to let your ears do the work

[graemevb]

Thanks for that. I thought all rms ratings were at 0.1% THD, or is that just most speakers that I look at?
And I hadn't thought of sensitivitites when I wrote that...

There are no standards for car audio or home audio speakers.
There are standards for home audio amplifiers which make it possible to compare.
For example the continuous ratings for home amplifiers are done after the amp has been running for a period of time at 1/3 rated power etc and it must maintain the output for an hour or so at a certain distortion figure, the are known as the IHF standards.

In regards to car audio speakers, Id be amazed if any car speaker could test to 0.1%THD at any power level or any frequency, typically there are 3-5%. Even the best home speakers are at best 1%.
Yes, people get all excited about whether an amp has 0.1% or 0.01% distortion, but only an oscilloscope is going to be able to tell the difference, its not going to matter when you connect it to real speakers.

[theSeekerr]

Hi,

None of these links will directly answer your question, however, they're all very detailed posts in which I try to clear up one misconception or another about audio. A lot of the maths is included, too, to give you some idea how it's done.

question about bridging?
Subwoofer to suit current amp
Subwoofer to suit current amp
ssl monoblock amp 500wrms at 4 ohms????
Can i run a 15 inch L7 off this amp?
Can i run a 15 inch L7 off this amp?

A monoblock amp, contrary to some peoples beliefs is not simply a 1 channel amp, but has different circuitry to multi-channel amps to make them run more efficiently, and generally have a bigger power output, but sacrifice a bit of quality. That makes them will suited to powering subwoofers, which take a lot of power to drive and the lack of high-end quality won't be noticed.

Um....sort of. A monoblock IS just a single channel amplifier, however, in car audio circles it's typically used to refer to a high-efficiency Class-B design. Class-B amplifiers exhibit higher distortion but lower power usage than typical Class AB designs. As Philthy says, they're typically used to drive subs, where the distortion will pass unnoticed.

In home audio, conversely, a monoblock is a single channel amp typically built to the highest quality standards, with marginally better sound quality than integrated stereo amps as a result of having a seperate power supply for each channel (avoids cross-channel modulation, or "crosstalk").

A lot of car amplifiers now are Class-D designs, which rely on Pulse Width Modulation and a low-pass filter on the output. What's that mean? It means that they're even more efficient than Class-B, and can sound anywhere from perfect to horrible, depending on how much care has been put into their extremely complex design. It also means that they're thinner, lighter and run cooler, all extremely worthwhile characteristics in car amps. Personally, I recommend them, but keep in mind that you'll get what you pay for.

Peak SPL Calculator Here's a useful calculator for determining the relationship between wattage, speaker efficiency (sensitivity) and loudness. Compare to Decibel (Loudness) Comparison Chart to give you a feel for how loud things actually are in dB terms. Note that exposure to 100dB for more than 2 hours a day will cause permanent hearing damage, which reduces to just half an hour at 110dB.

Sorry about the disorganised post, just a few things that came to mind. Other than that, I can recommend listening to Philthy and StoneX, they know what's going on. There's one bloke in particular that I'd recommend ignoring - if you read through my posts above, you'll quickly work out who it is.

- Chris

[Philthy]

Um....sort of. A monoblock IS just a single channel amplifier, however, in car audio circles it's typically used to refer to a high-efficiency Class-B design. Class-B amplifiers exhibit higher distortion but lower power usage than typical Class AB designs. As Philthy says, they're typically used to drive subs, where the distortion will pass unnoticed.

In home audio, conversely, a monoblock is a single channel amp typically built to the highest quality standards, with marginally better sound quality than integrated stereo amps as a result of having a seperate power supply for each channel (avoids cross-channel modulation, or "crosstalk").

A lot of car amplifiers now are Class-D designs, which rely on Pulse Width Modulation and a low-pass filter on the output. What's that mean? It means that they're even more efficient than Class-B, and can sound anywhere from perfect to horrible, depending on how much care has been put into their extremely complex design. It also means that they're thinner, lighter and run cooler, all extremely worthwhile characteristics in car amps. Personally, I recommend them, but keep in mind that you'll get what you pay for.

I thought most monoblocks were Class D circuitry, and most full range/multichannel were Class AB? I haven't looked into these kind of details for a while though so I could be wrong. I don't think there would be many people who could pick the quality difference between a well made Class D and a Class AB amp though.
Also worth noting is that, from memory I think most Jaycar amps are Class D which is how they manage to give such good power for such a good price. (I'll double check that in a min)

There are no standards for car audio or home audio speakers.
There are standards for home audio amplifiers which make it possible to compare.
For example the continuous ratings for home amplifiers are done after the amp has been running for a period of time at 1/3 rated power etc and it must maintain the output for an hour or so at a certain distortion figure, the are known as the IHF standards.

In regards to car audio speakers, Id be amazed if any car speaker could test to 0.1%THD at any power level or any frequency, typically there are 3-5%. Even the best home speakers are at best 1%.
Yes, people get all excited about whether an amp has 0.1% or 0.01% distortion, but only an oscilloscope is going to be able to tell the difference, its not going to matter when you connect it to real speakers.

Sorry, it was 1% THD that I was thinking of, not 0.1%. I'm no expert on these datails though, as I've said countless times I buy what sounds good to me, not what looks good on paper...although the paper stats help decide what is worth testing out and what not to bother with

EDIT: Just had a quick look over some of the posts TheSeeker linked, and there is some good reading in there. I agree about certain people that shouldn't be listened to, but TheSeeker definately knows what he is on about. I'm definately not an expert on the matter, I just know little things I've picked up along the way

[theSeekerr]

Hi Philthy,

To be honest, most of what I know comes from pro audio (concerts and whatnot) rather than car audio. You're probably right that most car amp monoblocks these days are Class D - but that's a relatively recent development, since Class D has only been "mature" for about 5 years.

I think all the Jaycar "Response" amps are class D - and yes, they are, typically, an exception to the "you get what you pay for" rule. They sound fine, but I have heard reports of them failing from build quality issues - apparently the 2007 models were fine, the 2008 models broken. I haven't heard anything yet about the 2009 models, or whether they have even been updated this year.

The take-home message from most of my posts can be distilled to: It's never a bad thing to have too big an amp, and often a bad thing to have too small an amp, however, you probably don't need an amp as big as you thought you did in the first place, because you probably don't want to listen quite that loud. Put another way: 100 or 150 Watts RMS per channel is a good size to drive most speakers, and 500 Watts RMS is a good size to drive most subs.

Take the calculator I linked to a few posts back. Find a speaker, and plug in its efficiency figure. Then enter a quarter of your amplifier's RMS power, and a distance of 1m (which you'll have to convert to feet, sorry - I think it's about 3.28 feet). A 100 watt RMS amplifier, driving an ordinary speaker of 89dB/Watt sensitivity, will thus give you enough power for an average volume of 103dB, with peaks up to 109dB. That's pretty loud, and you can add another 3dB for the other speaker in the stereo pair.

[warney]

hope this helps :

General Information
*Terminology:
Impedance - The resistance of a load
Ohms - Main unit for Impedance
Watts - Main unit for Power
Amps - Main unit for Current
WRMS - Watts Root Mean Square (see below)
Hertz - Unit of measure of frequency
Frequency response (Hz) - It identifies the speaker bandwidth, the limits within which it can be used with a linear response
Decibel - Unit of measure of sound pressure
HU - Head Unit
AMP - Amplifier
THD (Total Harmonic Distortion) - Measured additional noise or interference induced into the system by the power supplies
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Amplifiers
Calculating WRMS:
From Max Power - Max Power / (Square Root 2)
Bridged Mode for a single 4 ohm speaker - 2*(AMP Power in WRMS @ 2 ohm):
#Eg. 2 Channel Amp; Power: 50WRMS/channel with 4 ohm load, 70WRMS/channel with 2 ohm load .:. Bridged WRMS = 2* 70 wrms = 140 wrms. Therefore the 4 ohm speaker is receiving 140 WRMS of power
Parallel Mode with 2 equal speakers of x ohm - Power = [Power @ (x/2) ohms]/2
#Eg. Mono block Amp; Power: 200 WRMS with 4 ohm load, 350 WRMS with 2 ohm load. .:. Parallel WRMS = 350 WRMS/2 = 175 RMS. Therefore, each 4 ohm sub would be receiving 175 WRMS of power
Series Mode with n speakers at x ohm - ?
*Terminology:
Stereo -A stereo system has two independent signals, each driven into its own separate speaker
Mono - A mono system sends the SAME signal to ALL of the speakers
Max. Power - The maximum power an amplifier can produce with no load
WRMS (Nominal Power) - The power that the speaker is actually receiving from the amplifier at a continuous rate
Bridging - Connecting the -ve from one channel and the +ve from a second channel to drive a single speaker with more power due to each channel seeing 2 ohm resistance. This does NOT mean that there is a resistance of 2 ohm in total, just that each channel see half the total resistance.
Parallel - Running two speakers off the one channel, in result halving the impedance
Clipping - When the volume is turned up past what the amplifier can deliver and distorts
Overload Protection - A protection circuit that eliminates component failure from impedance loads that are to low by shutting off the amplifier
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Speakers
*Terminology:
Power Handling - The power that a speaker can receive for short moments (Max) or for continuous programs (Nominal).
Efficiency (dB): Reference efficiency value of a speaker; it is measured in decibels and at a distance of one meter, with 2.83 Volts in the input
Tweeter - Speaker specialised in reproducing high frequencies
Midrange - Speaker specialised in reproducing mid frequencies
Woofer - Speaker specialised in reproducing low and mid frequencies
Xmax (mm) - Mobile voice coil excursion, in one direction
Voice coil - Wire (usually copper) winding around a cylindrical former that is glued with the speaker membrane. Alternate current passing through mobile voice coil generates a magnetic field that interacts with the one occurring into the gap; the vibrations that derive from this are sent to the membrane, generating sound
Speaker Size - The dimensions of the speaker given in terms of inches
Coaxials - A speaker which produces all three frequencies in one unit
Components/Splits - A set of speakers which seperates into 2 or 3 lone speakers, which is combined with a crossover so that each speaker only reproduces its specific frequency
Crossover - Filter used to separate frequencies to their appropriate speakers
*Resistance Calculations:
Speakers in Series = R1 + R2 + ... + Rn
Speakers in Parallel = [R1^-1 + R2^-1 + ... + Rn^-1]^-1
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Speaker Enclosures
*Terminology:
Sealed - Airtight enclosure suited to general applications
Ported - Enclosure with ports which can be tuned to certain frequencies to change SQ and SPL characteristics
Isobaric - Two speakers placed in an array as to act as one speaker in an enclosure design that requires half the air space that a single driver requires
Bandpass - Bandpass boxes are a special type of ported box designed for maximum bass. The woofer is mounted inside a dual-chambered box (one chamber sealed, the other ported), with the sound waves emerging from the ported side. The sound that comes out of the port is extra loud within a narrow frequency range
Dipole Passive Radiator - A sealed box with 2 subs running out of phase

Infinite Baffle - Infinite baffle enclosures are the simplest from a design concept. The principle of IB design is the seperation of the front output of the woofer from the rear output of the woofers. One of the advantages of this design is the low resonant frequency of the IB system. This low RF allowes the system to have a very good low frequency extension. Another advantage of an IB design is the little amount of boot space needed for this application. For this reason IB designs are popular in cars where the boot space is small but there is a need for big bass...

One of the main disadvantages of this application is the REDUCED MECHANICAL POWER HANDLING of the speaker. This is due to the fact that the enclosure is actually the whole boot volume and the air in the boot is not able 2 help the mechanical suspension system of the woofer, for this reason not all woofers are suited for IB applications.

It is a common misconception that IB enclosures are the easiest to construct, this is not true as maximizing performance in this type of enclosure is quite difficult and time consuming. Maximizing the performance in a IB system you must minimize leaks and maximize the sturdiness of the baffle....

Ok, so in short an IB enclosure is putting a sub in the parcel tray and using the boot as one big enclosure and attempting to seperate all the air either side of the tray, same principal is used when placing a sub in the ski-port in some sedans and using the back seats/parcle tray as the dividing wall and the boot as the enclosure.

Also this type of enclosure means u cant feed buckets of power 2 the sub cos its not being helped by the box and will be worked 2 hard if u do apply 2 much power.

You will be surprised how many installs come out of brisbane car sound like this, if u feel air leaking from around the plate ur sub is fixed 2 then this is the "box" that u have got... *Written by 'Ferdie'
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Head Units
*Terminology:
'Loud' Button - To prevent overloading on speakers i.e push into clipping, try and adjust system gain levels to prevent its use
Power Rating ( 45 x 4 etc.) - This is the Max Power of the HU, not the WRMS. However, this usually equates to only approx. 13 WRMS from each channel
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SPL and SQ
*Terminology:
SPL - Sound Pressure Level, measured in dB
SQ - Sound Quality, measured in ?
-----------------------------------------------------------------------------------------------
Display Units
*Terminology:
LCD - Liquid Crystal Display
-----------------------------------------------------------------------------------------------
Wiring Guide
*Terminology:
AWG (Gauge) - American Wire Gauge; Used to describe the size of a wire in relation to its current carrying ability. Smaller the AWG, Higher the current carrying ability
Earth/Ground Wire - The wire which is earthed to the chassis via direct contact; Drains excess electrons to create an equal balance in the system
Power (Memory) Wire - The wire running directly from the battery to the source unit i.e HU, AMP; providing the main source of power. Called memory wire in reference to its ability to provide power to the HU so that stored data is not lost when the car is switched off
Accessory Wire - The wire which only supplies power to the source unit when the ignition is turned over to ACC i.e car turned 'ON'
Speaker Wire - The wire which sends power and signal to a speaker
RCA Outputs - Dual wires which are specifically for sending signal to an amplifier, as they do not have a high enough output current to drive a speaker
Internal Wire Resistance - The resistance of the actual metal which the wire is made out of, usually small in relativity
*Guide to choosing what gauge wire:
AWG___Maximum Rated Current
00___ 400 amps
0___ 325 amps
1___ 250 amps
2___ 200 amps
4___ 125 amps
6___ 80 amps
8___ 50 amps
10___ 30 amps
12___ 20 amps
14___ 15 amps
16___ 7.5 amps
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FREQUENTLY ASKED QUESTIONS (FAQ'S)

Q: Will a blow off valvy thingy give me booste?
A: NO!

Anyways, here is a list of questions that seem to appear constantly in this forum:

Q: Is it safe to overpower a sub or speaker? Eg. 700W amp on a 400 W sub...
A: Yes, as a matter of fact, it is a lot more beneficial for the subs performance and safety that you use a overpowered amp and adjust the gain settings to suit your listening levels. Underpowering a sub, then pushing it to its limits (high volumes) can be harmful to both sub and amp due to clipping (see above)

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[theSeekerr]

'Loud' Button - To prevent overloading on speakers i.e push into clipping, try and adjust system gain levels to prevent its use

The "loud" button is a frequently misunderstood beast. It's simply an equalisation curve which is designed to compensate for the way the human ear works - at low SPL's, we're more sensitive to midrange frequencies than bass or high treble, and the "loudness" EQ crudely compensates for this by boosting the bass and treble.

It doesn't make your system louder, nor does it make your system "sound" louder. It just makes it sound a little bit better if you're listening at low volume.

Of course, a lot of people leave it turned on all the time, either believing one of the fallacies above, or, most often, because they like the bass boost.

Point is, it should only be used at low powers anyway, so the above advice is a bit silly.

[Philthy]

Amplifiers
Calculating WRMS:
From Max Power - Max Power / (Square Root 2)

Midrange - Speaker specialised in reproducing mid frequencies
Woofer - Speaker specialised in reproducing low and mid frequencies

Thats a good write-up, if maybe a bit long.
There's a couple things I wanted to pick up on though.

I see a lot of different amps where the RMS power isn't related to the max power as you stated above. Not to say I try calculating them, but for example I might see a 300wrms Kenwood amp advertised as 600w, but then an alpine 300wrms advertised as 500w.

And just to be picky, with the speaker terminology, I have always called midrange speakers woofers as well. There is confusion around where if you were to say the word woofer people automatically assume you are talking about a subwoofer

EDIT: Oh, and I agree with theSeeker on the LOUD button. If I'm listening to my stereo for a while with no sub and at low volumes (like when I wash my car) then I will turn loudness onto the low setting for that little extra kick that is hard to pick up when its so quiet

[theSeekerr]

Oh, cripes, I didn't even see the watts RMS thing the first time around.

That version is wrong, in two ways. Let's run the numbers:

Let's take an amplifier rated for 100W into 4 ohms. Since Power = Voltage Squared / Impedance, we can see that it's swinging a voltage of 20V RMS, or 28.28V Peak.

Since we also know that Current = Voltage / Impedance, we can see that there's a peak current of 7.07 Amps.

Finally, since we know that Power = Voltage * Current, we can see that the peak power is 28.28 * 7.07, which is 200W, or 2 times the RMS power, not Sqrt(2).

However, that's not how the amplifier makers calculate "Peak" power, or "Peak Music Power Output". That's done by a very technical method called "making shit up". Read some more about it here: Amplifier Power Ratings

[markER717]

Thanks for all your help guys!