rms????

[Defiant[YD]]

kk, i've been hearing my buddies talk about it, i've been hearing 3geez'ers talk about it, now it's time for me to ask the dumbest question of all time. WTH is rms?????
i read that RMS is more important than max output in one of the posts.

cuz i'm planning to get a new amp (trust me, "THump" sux) and i've been looking at a 350w kenwood, and a 200w mtx. i'm hesitating on the mtx cuz of the power. but if rms is more important, mtx it is. but if the power is also a factor, i dunno what to get then.

[shepherd79]

RMS & Continuous Power output

CONFUSION:
Many people wrongly believe that the RMS power rating is the same as a continuous power rating.

Power:
First, power is a 'snapshot' of the amount of work being done at any point in time. It has no specified time component.

Ratings:
There are a lot of different ways to rate an amplifier's output power capabilities.

A few possible ways to rate amplifiers:
Watts (not much information and lends itself to many different interpretations)
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When manufacturers state the power output in 'watts' (and only 'watts' i.e. 50 watts), they want you to assume that the wattage rating is an accurate measurement of the amplifiers ability to do a given amount of work (driving your speakers). In reality, the power rating could be derived by using peak voltage instead of the more honest RMS voltage when plugging the numbers into the formula P=E^2/R. This would give a power output/rating that's TWICE the RMS power output. Actually they could be using virtually anything to derive this vague specification (pulling a number out of thin air comes to mind).


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Peak watts (misleading because many will take it as a true measure of the work that the amplifier will do when driving the speakers)
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If the manufacturer specifies wattage as 'peak power' they may say that they aren't trying to mislead their customers, but I believe that that is precisely what they are trying to do. They assume that the vast majority of people are going to accept the wattage as the maximum power that the amplifier can produce. If they use peak voltage to derive the peak power, the power specification may be legitimate but it is misleading. The peak power is mathematically twice the RMS power output.


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RMS watts (Better than peak power but it also lends itself to misinterpretation because it contains no specified element of time)
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RMS wattage is an accurate way to measure power but the amplifier may only be able to produce the RMS voltage into the given load for a fraction of a second. The, less than honest, manufacturer may plug this RMS voltage into the P=E^2/R formula and give this number as the amplifier's output. If they give this as the power output of the amplifier but don't tell you that the amplifier can't continuously produce this power level, they are again misleading you.

RMS continuous watts (the best, most accurate, honest way to measure power output)
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When manufacturers rate their amplifiers at a given number of RMS watts continuous power output. They are using RMS wattage (derived from RMS voltage) which is the most accurate way to state the useful power produced by the amplifier. There is only one way to interpret this. They are also stating that the amplifier can produce the power continuously. If they didn't specify continuous power they may be trying to cover up the fact that the amplifier could only produce the RMS voltage required to drive the given load to a given RMS power for a fraction of a second (like in the previous example). When they state continuous output power, they are saying that the amplifier can easily and continuously produce the rated output power.

[shepherd79]

i hope you understand now. if not please visit this website and you will learn a lot. http://www.eatel.net/~amptech/elecdisc/caraudio.htm

[Bobs89LXi]

Thanks Alex. You saved me some time. :D I agree. Peak output is BS. You can get a cheap bargain basement amp to peak at 200 watts. True power output is RMS. When looking for an amp, always go by the RMS rating. If an amp manufacturer doesn't have it in the specs, find one that does. Just my opinion.

[Defiant[YD]]

kk... icic. that was really informative!!! thx for that shepard! i still want my fuel gauge though!!! hehehe

well, which one is better then?
this MTX:
http://www.futureshop.ca/catalog/proddetail.asp?sku_id=0665000FS10006288&catid=11031&atab=2&logon=&langid=EN&dept=9&WLBS=fs%2Dweb6#MoreInfo

or this kenwood:
http://www.futureshop.ca/catalog/proddetail.asp?sku_id=0665000FS10005867&catid=&atab=2&logon=&langid=EN&dept=9&WLBS=fs%2Dweb6

cuz they don't state the rms stuff on there.

[shepherd79]

MTX amp:
RMS 120W x 1 briged at 12.5V into 4ohm load.

Kenwood amp:
Bridged Power Output at 14.4V 150 Watts x 1

PS: gauges will be on it is way to you this week. i am getting paid this week.

[Defiant[YD]]

kk. thx! i'll be looking forward to the gauges!!! i really need to see how much gas my car uses up. filling up at every 400km is kinda expensive.

so from what u just said, the kenwood one would be the most logical choice right?

[shepherd79]

they are both good. MTX says that it is stable at 2 ohms, but they didn't give watts when it is bridged and pushing at 2ohms.
i have alpine MRP-m200 it is a mono amp that is pushing 200Watts at 2ohms with no problem.
Kenwood never said anything about being stable at 2ohms.
you can try ebay, they always have some nice amps that have a little more power.
how much power are you looking for?

[Defiant[YD]]

so both would give me the same performance???

cuz my friend works at this electronics store (futureshop) and he can get me 50% off the amps and speakers and decks and stuff.
i want a new amp cuz, well, i'm running a supposed 500w "thump" amp... so shitty, and these two are the ones in my budget range for now... (just blew a lot of money for my friends b-day present. trust me, gals not easy to shop for).

cuz if they both give me the same performance, i'd go MTX. but if not, i'll go for the more powerful one.

[shepherd79]

if i was you i would go with MTX. I am not a big fan of KENWOOD stuff.

[Tim Yoak]

Peak power is what happens when a cheap amp blows it's output transistors and sends a dc spike through your speakers frying them. Stick with a quality brand amp that you know. most honest manufacturers will give a true rating, their reputation depends on it.