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Discussion Starter · #1 ·
I'm about to upgrade my I.C.E system, and am worried that the additional power I require could have a great impact on my battery.
I have come to understand that if I am using 400 watts an additional 400 watts is lost in heat and such. Is this understanding correct?
I worked out that 5 speakers, [email protected] [email protected] = 1550x2 (power loss through heat) = 3100w + 400w (inverter, fans and lighting)= total of 3500 watts.
I am really unsure of the heat factor. If this is the case then It will need a 300amp fuse. If I was to take the supply stright to the boot and I'd need to use 0 gauge cable. I am new to auto electrics and audio systems so plz go easy on me.
I also have some really lame questions to follow but they can wait.
What do u guys think of JBL speakers and subs?
Cheers guys, any help will do.
Oh 1 last thing. I also got a 3 farad capacitor, not sure what power usage it will have on batt, instructions r rubbish.[/b]
 

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simplyuniqueperformance said:
I have come to understand that if I am using 400 watts an additional 400 watts is lost in heat and such. Is this understanding correct?
no that would mean ure amp is only 50% efficent most audio class a/b amps are 70 -75% efficent and up.

I worked out that 5 speakers, [email protected] [email protected] = 1550x2 (power loss through heat) = 3100w + 400w (inverter, fans and lighting)= total of 3500 watts.
1. the power stated by the amplifier is the output power with all the losses already added in for example a 300w amplifier is really a 400w amplifier with a 75% efficeny rating hence 300w output. (i think anyway)

2. the power rating given on speakers are max power to find the real power (average/rms) u half the max power to get the peak power then divide by root 2 to get rms power. havent got a calculator so u do the math...

I am really unsure of the heat factor. If this is the case then It will need a 300amp fuse.
hell no ull never hit 300A bud, with those five speakers at a guess ull be around 20A but im sure some1 who has a calculator will work it out for u :)

Oh 1 last thing. I also got a 3 farad capacitor, not sure what power usage it will have on batt, instructions r rubbish.
power caps dont have any drain on the battery except for when they are charging up they work in parallel with the supply basically ure sound system will draw power from the cap rather than the battery this will help keep a constant volatge supply to the amps when ure driving the subs hard.
 

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Discussion Starter · #3 ·
1. the power stated by the amplifier is the output power with all the losses already added in for example a 300w amplifier is really a 400w amplifier with a 75% efficeny rating hence 300w output. (i think anyway)
My understanding is that you use 300watts as stated you loss watts that are not accounted for. I.E amp rated at 2800watts (max) rms=1200w, but this wattage is based just on the sound output. So my amp can deliver 1200w(rms) to my speaker not accounting for heat loss and cable resistance. (but I am new and not really got a clue bout this).
I used haynes max power on ICE to come up with the fact that amps r accepted as been 50% efficent (page141) . I aint got amps yet, so i can't see the exact spec. (comming through post.) I just thought the 50% thing was a rule of thumb. but going on 75% it does make one hell of a difference.
Think you may have been a little generious with ampage there, on 75% watts used are 1937.5+ 400= 2337.5.
watts divided by volts =amps so 2337.5 / 12.6 = 185 amps. (is this the right equation for d.c circuits?)
Once again thanks for help
 

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My understanding is that you use 300watts as stated you loss watts that are not accounted for. I.E amp rated at 2800watts (max) rms=1200w, but this wattage is based just on the sound output. So my amp can deliver 1200w(rms) to my speaker not accounting for heat loss and cable resistance. (but I am new and not really got a clue bout this).
u dont need to worry about heat loss etc that all been accounted for by the designer of the amplifier. in theory yes u are correct amplifiers loose alot of power from heat etc this is due to alot of things inside the amplifier such as as the biasing of the transistors. y do u think it costs alot of money to get a high powered amplifier? the losses are worse the higher in power u go.

I used haynes max power on ICE to come up with the fact that amps r accepted as been 50% efficent (page141) I aint got amps yet, so i can't see the exact spec. (comming through post.) I just thought the 50% thing was a rule of thumb. but going on 75% it does make one hell of a difference. .
dont know, the 75% is approx the therioritcal maxium efficency for that type of amplifier the real maxium efficency will be lower for ure amp and will depend on alot of things such as how much cash ure willing to spend.

Think you may have been a little generious with ampage there, on 75% watts used are 1937.5+ 400= 2337.5.
watts divided by volts =amps so 2337.5 / 12.6 = 185 amps. (is this the right equation for d.c circuits?)
Once again thanks for help
one thing to understand is although the amp says 1200w rms it is not always delivering thbat power thats just the average power when the input signal is at maxium because thats when the base currents of the transistors are at max swing. [in every audio song there always a build up to hard deep bass part of it so the input is never at max if u kinda get what i mean]

1 point im not to sure about that i would love for some1 to clear up is in two scinerios.


1) 1200w (rms) output however the amplifer is only 60%, so infact the actual output is really only720W (rms) divide by 14.4v = 50A flowing and being drained from altenator.

2) 1200w (rms) output [the efiiceny of the amp is irrelevant as the designer has quote the power output at that efficency level]
divide by 14.4v 83.3A flowing and being drained


any1 answer that 1 for me? [cause im lazy and cant be bothered finding out :) ]

hope that was any help to u as always what i say is off the top of my head from what i can rember and might be out a little or a lot :up:
 

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what kind of system are you thinking of geting ?...........all im running is
cerwin vega comps front
infinity rears
300w planet audio 12"
zx350 pg amp
f300 v12 alpine amp.
140.9 db........
 

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Discussion Starter · #7 ·
Right I am running 2x 10inch and 1x 15inch 1000w max 250wrms subs, 4 x 200wrms 400wmax speakers t.v tuner, xbox, line driver, 3 farad capacitor, various lighting and 2 amps 1 @ 2800w max 1200wrms and 1 @ 1600w max 900wrms. Oh and 3 x 7inch tft screens.

1) 1200w (rms) output however the amplifer is only 60%, so infact the actual output is really only720W (rms) divide by 14.4v = 50A flowing and being drained from altenator.
Right thing i got the basics of this now. When an amp has a rating of 1200w rms and you set the output to 1200w then the output of the amp to the speaker is 1200w. But I'm going to keep it simple and say amp is 50% efficent. so the amp requires an input of 2400w to have an output of 1200w. Also avrg car batt at avrg is 12.6volts (i think) so 2400 divide 12.6 190amps. This is a high amount i know, but there the figures on 50%. Also do it by the book and it will always work. Dont and it prob will work with greater chance of failure. Try it and see i think is best option just dont over rate fuses.



2) 1200w (rms) output [the efiiceny of the amp is irrelevant as the designer has quote the power output at that efficency level]
divide by 14.4v 83.3A flowing and being drained
Not sure how input is same as output you'd think it would go through a few reisistors and things to use some power. anyways the calculation is right.
/ = divide
watt / volt = amp
watt / amp = volt
amp x volt = watts
 

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where are u getting these figures a maxpower book did u say? ill tell u from experience a 1200w rms amp will definately not need a fuse of 190a thats just crazy the actual figure is 60A i know this cause i had the vibe vp4 digital which was 60a rated with an output of 1200w RMS

http://209.200.11.57/forum/viewtopic.php?t=5080

^^ read there thats some info that might help u that was written by nitro.


with the setup u sayed yes it would be advisable tochange batt to yellow cap and upgrade altenaor wiring to get the best out of the system.

bud 1 piece of advice what type of amp u got to power the subs ir ure gonna run 3subs be carefull about ure load resistance ull be lucky if the amp can run 3 subs.
 

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Discussion Starter · #9 ·
I think figures are all balls as well, at most I'll have to run 2x 100amp feeds to boot (i hope). Could do with some feedback from nitro, anyone know him? I think I'd better wait till i get spec on amps. even if we take out max power info of 50% and say only 1200wrms is been used then thats still 95 amps on the understanding of a 12.6 v supply. I'm not experenced in this matter so its all new to me, but i'm sure the physics of it stay the same.
 
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