RMS Output vs FTC Output

[wseyller]

Not sure if this is highly technical but I can find any explaination on this. I have an home amplifier and in the specifications it shows:

RMS Output Power: Dolby Digital Mode
Front Ch 170 W per channel (6ohm) 1kHz, 10% THD
Surround CH 70 W per channel (4ohm) 1kHz, 10% THD
Center CH 260 W per channel (4ohm) 1kHz, 10% THD
Surround CH 260 W per channel (4ohm) 1kHz, 10% THD

Total RMS Dolby Digital mode power: 1000W


FTC Output Power: Dolby Digital Mode
Front Ch 100 W per channel (6ohm) 120Hz-20kHz, 1% THD
Surround CH 45 W per channel (4ohm) 120Hz-1kHz, 1% THD
Center CH 140 W per channel (4ohm) 120Hz-1kHz, 1% THD
Surround CH 150 W per channel (4ohm) 120Hz-1kHz, 1% THD

Total FTC Dolby Digital mode power: 580W


I wonder what the difference between the RMS and FTC is? Is my amplifier able to output closer to 1000W or 580W

 

[CycloWizard]

RMS is the root mean square power output - approximately an average value, maybe at maximum volume? I'm sure someone else here can give a better answer.

I wasn't familiar with FTC, so I found the following info:

Dynamic power indicates the actual power this amplifier will deliver to the woofer under normal operating conditions. While the FTC power rating indicates power available on a continuous, long-term basis, subwoofers do not rely on that type of power. Instead, the amplifier is called upon to deliver large, short-term peaks of power to be able to support the wide dynamics required by today's digital music and movie formats. In addition to the required FTC power rating, we've provided the dynamic power rating as a better indication of the product's true performance.

Source

 

[patentman]

RMS power is the root of the mean value of the square of wave amplitude. The root is used to find the DC equivalent of an AC quantity. In otherwords, it is, as mentioned above, an "average" power rating, and probably the one to rely on the most when evaluating the power of an amp. Rule #1 of amplifiers is if the RMS power of an amp is not disclosed, do not buy it.

FTC power rating indicates power available on a continuous, long-term basis. Most music (unless you are playing one continuous long note) is not technically continuous, and so this rating is not as important as RMS. Also, the reason its called "FTC" power is it relates to an amplifier rule (See this link) the federal trade commision promulgated a number of years ago to ensure fair advertising of amplifier power ratings.

Check out this Link for a description of various power ratings, including RMS power.


As for your questions, 1000W RMS is pretty damn good. You could power a couple of 12's or a 15 with that thing easily. Just be careful not to hit the "brown" note. :Q Seriously, I've been in cars with bass so low and so loud that it almost made me lose control of my faculties, so be careful. :shocked:

 

[wseyller]

Well then there must be something wrong with it then because it sounds pretty weak. Even at 580W it should be very loud. The volume adjustment must be practically up the way up for anything impressive.

 

[MrDudeMan]

You may have the wires reversed. I have had that affect the volume pretty badly a time or two..

patentman, what do you mean the root is used to find the DC equivalent of an AC quantity? the only way to get DC out of AC is to rectify it and for that you use the peak of the wave, not the RMS.

 

[patentman]

Originally posted by: Bigsm00th
You may have the wires reversed. I have had that affect the volume pretty badly a time or two..

patentman, what do you mean the root is used to find the DC equivalent of an AC quantity? the only way to get DC out of AC is to rectify it and for that you use the peak of the wave, not the RMS.

Scroll down to the discussion of RMS values in this link it explains it a lot better then I can in text on this message board.

 

[MrDudeMan]

Originally posted by: patentman

Originally posted by: Bigsm00th
You may have the wires reversed. I have had that affect the volume pretty badly a time or two..

patentman, what do you mean the root is used to find the DC equivalent of an AC quantity? the only way to get DC out of AC is to rectify it and for that you use the peak of the wave, not the RMS.

Scroll down to the discussion of RMS values in this link it explains it a lot better then I can in text on this message board.

yes, i understand how AC to DC works quite well. however, what you said still isnt true if you are going off of 1 power source. the wall power rectified to be DC is ~169 volts, and only 120V RMS (AC). in order to get 120V DC from a 120V RMS AC source, you have to transform it down after you rectify it. maybe i was going a little too indepth but still.

 

[CrispyFried]

what ohm rating are your speakers and what efficiency are they rated at? if theyre 8 ohm and inefficient thats why they dont sound loud.

also note that FTC is 1% distortion, rms is 10%. 10% is very noticable. so use the FTC rating as your guide. most amp ratings Ive seen are at 1% distortion.

 

[fornax]

Originally posted by: Bigsm00th
yes, i understand how AC to DC works quite well. however, what you said still isnt true if you are going off of 1 power source. the wall power rectified to be DC is ~169 volts, and only 120V RMS (AC). in order to get 120V DC from a 120V RMS AC source, you have to transform it down after you rectify it. maybe i was going a little too indepth but still.

Rectification is irrelevant here. It's easier to think in terms of how much work the AC current will do (which is utimately why we use it). Basically, AC voltage with a RMS of 120V will do the same anount of work (e.g. moving the speaker membrane to generate sound waves) as DC of 120V.

 

[patentman]

Stupid computer!

 

[MrDudeMan]

Originally posted by: fornax

Originally posted by: Bigsm00th
yes, i understand how AC to DC works quite well. however, what you said still isnt true if you are going off of 1 power source. the wall power rectified to be DC is ~169 volts, and only 120V RMS (AC). in order to get 120V DC from a 120V RMS AC source, you have to transform it down after you rectify it. maybe i was going a little too indepth but still.

Rectification is irrelevant here. It's easier to think in terms of how much work the AC current will do (which is utimately why we use it). Basically, AC voltage with a RMS of 120V will do the same anount of work (e.g. moving the speaker membrane to generate sound waves) as DC of 120V.

lol...ok you guys just dont get. thanks for telling me what the RMS is :roll: i was talking about the theory behind what is going on and not so much the actual problem. afterall, i didnt even bring up the AC->DC conversion. i simply pointed out patentmans misunderstanding.

this is highly technical after all so i figured i didnt have to dumb it down and explain all of that. apparently i was wrong. just stop this 'debate' and get back on topic.

 

[patentman]

Originally posted by: Bigsm00th
lol...ok you guys just dont get. thanks for telling me what the RMS is :roll: i was talking about the theory behind what is going on and not so much the actual problem. afterall, i didnt even bring up the AC->DC conversion. i simply pointed out patentmans misunderstanding.

this is highly technical after all so i figured i didnt have to dumb it down and explain all of that. apparently i was wrong. just stop this 'debate' and get back on topic.

O.......k. Maybe you should clarify your question then before you decide to label people as stupid. I was not, and am not, trying to get into the math behind what I said. I was just trying to answer a question regarding what RMS power is and what FTC power is.

Snide holier then thou comments are not appreciated by anyone. :disgust: