amps and speakers

[AznVirus]

i have this headunit that says it sends 40X4 on the faceplate. does this mean it sends 40 Watts for each speaker no matter what? is there a way to send less watts? cause the front speakers can only hold 2-20W RMS. the peak power handling is 80 watts. if i just use these speakers, will i blow them?

[Swonder67]

the 40X4 power rating is referring to peak power. your headunit prolly puts out around 20-22 watts RMS. those speakers should be fine.

[AznVirus]

if i get an amp that says 150X2 RMS. that means its going to run at 150 constant power right? if it just says 150X2 then thats just peak power?

[Swonder67]

if the amp says 150 X 2 it means 150 max. They always give you Peak power, even though RMS is the more important one.

[AznVirus]

if i have substhat can handle 600W max, and the rated input power is 150W, will i be going under the rated input power if i use that 150X2? i want to get the most out of my subs.

[Swonder67]

Well, you'd be under the max wattage they can hold, but they will stilll work. the only way to increase the watts goin to them is to get another amp.

[Brian P]

"if i get an amp that says 150X2 RMS."

if it says RMS then it's RMS. and if it's x 2, then one would assume 150 RMS per channel, thus, 300 watts RMS of power.

[Swonder67]

if it says 150 X 2 RMS then yeah, thats 300 total RMS power. but if that were true, the amp would be over 1000 watts max power. Usually, when you see amps out there, they always show you peak power in big letters, and its usually a round number, like, 300 watt. To find RMS power, you put peak power through some wacky equation I can't tihnk of at the top of my head. like my head unit is 50 watt peak power, and on the head unit, it says, "50X4" but the actual RMS power is 22 watts per channel

[Rich]

I hope I dont get chewed out by any audiophiles for this.


To get a rough estimation of RMS power, its usuially 2/3 of the peak.

Example. A deck with 45x4 power is going to be around 30x4 RMS


Remember this is just a rough estimation that I just use when shopping for an amp and they usuially just say the peak power on them. If there are no sales persons around its close enough just to figure 2/3 as the RMS power.

Hope it helps.

[Swonder67]

I would say less than 2/3. more like 1/2 or lower.

[hybridamp]

Yes, usually %50 or lower.

Example: 300watt max power
would be: 150watt RMS power Typically

Though the less quality of the amp, the more the percentage goes up!

[lloyd_nickens]

Um, if memory serves me right, the RMS power of an amp is a direct funtion of its efficiency. Take for instance my MTX 500D can produce a maximum power output of (75 amps x 14.4 V) 1080 watts. With a 91 % efficiency it puts out a real 984 watts of power. The rest is wasted as heat. Now the real trick is finding out its efficiency rating.

[Rich]

Originally posted by lloyd_nickens
Um, if memory serves me right, the RMS power of an amp is a direct funtion of its efficiency. Now the real trick is finding out its efficiency rating.

Yes, you are right. I just posted before because depending on the product, it can be hard to find the efficiency rating, so I figured some other way would be ok even tho its less accurate.

[pche059]

Just go with a Class D amp
anyway guys
IMHO there are not many cases that you will over power a speaker
in fact in most cases it is "underpowering" which will cause a speaker to give up.
as for worrying that too much power could be going into a speaker...well don't look at the power that they "claimed" can handle...most of the times they are unaccurate.
Just run as much clean power into it as you can...you WILL know when you are over powering a speaker... if so..you can always turn the gain down
and i would say it is still better than underpowering hence distorting the speaker

[AznVirus]

well basically i want to get the best out of my speakers without blowing them. but just say your peak power on the amp is over the maximum wattage the subs can handle, it will blow if i turn it up too much right? wouldnt it be safer if i kept the peak power of the amp right at the maximum power of the subs? for example...

here is my subs...
http://cgi.ebay.com/aw-cgi/eBayISAPI...tem=1288338321

and here is an amp i want...
http://cgi.ebay.com/aw-cgi/eBayISAPI...tem=1296687752

and basically ill be running only about 75X2 RMS wattage? can i get a bigger amp without chance of blowing it?