A lot of people have been having issues with the Yellow Tops lately, I have a brand new one that rests at 12.1, I need to bring it in, this is the second one in a year.

I plan on upgrading to something better upfront with a 120ah+ for the rear.

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- 08-28-2012cynRe: higher impedance easier on electric system?
- 08-28-2012Flex68Re: higher impedance easier on electric system?
- 08-28-2012_dontaskwhyRe: higher impedance easier on electric system?
o ok yea u should my duralast gold has been fine sitting at 14.3.

- 08-29-2012akheathenRe: higher impedance easier on electric system?
okay, easy way to settle this: apparently, none has actually seen the efficiency graphs of different amplifiers. look them up, and i hope you find them, and not just take my word. every amp has a max efficiency point. some are at higher impedances than others, but the point is that max efficiency is at/near the amplifiers full clean potential. the only real way to tell is to actually tell, is to measure rail sag and watch where the voltage drops beyond a typical operating slope, or even drops some on particular amps with a good rail regulation. A good indicator i look at, is rms doubling with ohm load. take, for instance, your 600rms@1. if it does 300rms@2, and 150rms@4, then i would have to say that power supply is in the lower operating range at 2 and 4, which would be typically 40-60%, sometimes less. now, your other example of a 1500 that does 600@4, then it would be doing 375@4 if 1ohm was the most efficient. likely, that would be an amp that likes 2ohm, where it is efficient, but not overly strained and heated. old school kicker amps were a good one to look at. they gave the 1,2,2.66,4, and 8 ohm ratings. 2.66 is where they reached most efficiency. usually looked like this: 37.5@8, 75@4, 125@2.66, 125@2, 100@1. so basically, in your example, the 600@1 would be more efficient than the 600@4.

as for the optimas, i've been saying that for a while. last year, or 1.5-2years ago, i threw out 13 optimas. last winter, my best friend pulled in the driveway with his newer yellow-top swollen like i've never seen before, and i have 2 more yellow tops, and 1 red top i have to go drop-off for disposal. then, there is my last red top, which i have to try and save, but it might just be toast like the rest. i run an x2power in the daily. - 08-29-2012quackheadRe: higher impedance easier on electric system?
How can this statement be valid if we do not even know which 2 amps are being compared. As you say, it depends on design, which also depends on Make and Model.

And what about dynamic headroom on a 600w@ 4ohms/1ohm stable amp compared to 600w@ 1ohm, assuming the 1ohm amp may not be .5 ohm stable?....and then again, how about the possibility of .1% THD at 4ohm rated output vs the possibility of 10% THD at 1ohm rated output?

OP, which 2 amps are you trying to compare, exactly? - 08-29-2012akheathenRe: higher impedance easier on electric system?
what i am looking at is how the power is passed through the torroid(s), where the greatest majority of efficiency is determined. at lower power levels, a lot of the field enters in and around the core and a lower amount is sent through the secondaries, as they only need so much. the use in the secondaries lowers resistance effect the secondaries have on the total inductance.

*dynamic*headroom is a big part to do with the rail storage caps and impedance drop below the mean topology. however, i was just answering the simple question of efficiency. iirc, the 2 amps were hypothetical amps, so i went with what is most likely and common traits, which is not usually .5 stable, and even if it is .5, it would probably still reach the most efficiency at 1ohm, or 2ohm load. at lower imp. there is more strain and loss in the whole system. - 08-30-2012quackheadRe: higher impedance easier on electric system?
Is this a contradiction to your earlier post? Or, are you referring to .5 ohm operation vs 1ohm operation? Are you suggesting an amplifier can be 86% efficient at 4 ohms and 98% at 1 ohm?...and Dynamic Headroom.. this would be where some amps' max power rating might be handy, right? For instance, the Orion HCCA25001 is rated 625 @ 4, 1250 @ 2, 2500 @ 1 and 5000 max. does this mean there is enough reserve capacitance to possibly achieve 5000 watts at .5 or .25 and at this point, there is no dynamic headroom available and the efficiency is at rock bottom?

it is late..er, early and I may not be making much sense, but thank you for trying. - 08-30-2012keep_hope_aliveRe: higher impedance easier on electric system?
efficiency is determined by the amplifier topology, which determines how efficiency reacts to changes in impedance load.

Amplifier efficiency climbs as you increase power output - until the limits of the power supply are met and thermal losses are linear.

Efficiency drops as impedance load is reduced (same output power level) due to increases in current: current = heat = losses. The drop is worse for Class A/B than modern Class D or other topologies.

http://www.icepower.bang-olufsen.com...1_06072009.jpg

Audio - ClassD: October 2010

AVR-2308CI Measurements & Analysis — Reviews and News from Audioholics

the age old question: do you draw less current with 600W@1 ohm or 600W@4 ohm?

answer: depends on the two amplifiers in question.

in the examples given above: if the amplifier is rear it's rating, it's efficiency is near peak. highest efficiency would be Class D and operating near rating - whatever impedance that may be.

of course, headroom/crest factor/etc. certainly come into play from a musical standpoint. we prefer our amplifiers to have more output capability for musical peaks, meaning most of the time they are operating at lower efficiency points, waiting for a musical peak.

for the OP: you have a 454 block - you have flexibility as to what size (or how many) alternators you can put on that beast. - 02-10-2013AxT4430Re: higher impedance easier on electric system?
Resurrecting an old thread.. from this last graph would the a/b class amp should a much higher efficiency at say 400 or 800 watts? or is this amp dependent, ie power supply dependent?

---------- Post added at 08:17 PM ---------- Previous post was at 08:16 PM ----------

Maybe its just me but this graph is so misleading to me.. - 02-10-2013AxT4430Re: higher impedance easier on electric system?
- 02-10-2013AxT4430Re: higher impedance easier on electric system?
@

**neo_styles**; @**pro-rabbit**; @**ciaonzo**; @**keep_hope_alive**; @**Spooney**; @**av83**;

Just listing people I think could explain past common dogmatic beliefs.. Thanks for any replies! - 02-10-2013neo_stylesRe: higher impedance easier on electric system?
Nobody can answer this better than KHA, man. I can't remember enough of my BEE knowledge to be able to cover it adequately, but it has to do with the P/S switching required to output a higher level of power IIRC and how class D topology allows for faster switching than A/B.

- 02-10-2013AxT4430Re: higher impedance easier on electric system?
How does that correspond to Impedance levels and efficiency on electical systems? Thanks Neo!

Why are higher impedance's usually more effiecient with lower THD ratings?

Is this always a general law for any class/amp or is just a particular case or a/b class?

btw, whats your acronym BEE mean? - 02-10-2013neo_stylesRe: higher impedance easier on electric system?
Basic Electrical Engineering. One of the first classes we take for my line of work.

As for impedance levels and efficiency, it's not overly complicated. Just think of what "impedance" means. Just like "resistance" is the ability to*resist*voltage, impedance is the ability to resist the flow of current. So at lower impedances, the system is easier able to accept changes in current. - 02-10-2013AxT4430Re: higher impedance easier on electric system?