Higher Effiency vs Lower Ohm Load

[Blackout67]

So I have been watching amp dyno videos because I need to replace my amp I've blown and I've noticed that as speaker impedance lowers, effeciency of the amp drops condsiderably and I want to know why 1 ohm stable amplifiers are pushed so heavily and everyone looks for them (hell every time I shop for one myself, I always go straight for 1 ohm stable amps), if you can get an amplifier that puts out the same power with better efficiency?

Let me explain:
My girlfriend needs a new amp cause Im pretty sure I fucked it up by running it over with the chair moving to back and forth so many times. Anyways, I was looking for something small and effient for her single cab beater truck with no upgades other than an AGM (Never got around to doing the big 3 on this one before I let her take it over) so we wont have to worry about voltage drop cause she loves to crank it and I found the JP3
So I watched the Williston Audio amp dyno to see what kind of amperage it draws to make the power cause I knew itd be putting out more than rated as all the other JP amps do. To make just over 1000 watts it is pulling 140 amps at 13.5 volts @ 1 ohm. An abyssmal 68% effiency. The test before that. 2 ohm, was making like 950 pulling just 83 amps at 13.6 volts that is 88 percent efficiency. That is a MASSIVE difference especially if you are running a stock alt/battery/wiring.

I know the quality of the parts def plays a factor in these numbers, but even from watching other amp dynos and comparing what one would make at 1 ohm vs 2 ohm with similar voltage and the difference was still usually around 15 percent between 1 and 2 ohms which is considerable if you are trying to squeeze out power on a budget. Also keep in mind that as the temperature of the amp rises efficiency will go down too and 1 ohm loads will produce much more heat as they are closer to a theoretical short so your amp has to work harder to keep everyting under controll, generating more heating and lowering efficiency and life span of the product.

What are the benefits of "getting the most out of your amp" if it comes at such a large expense? Ive always read that you wire it to the 1 ohm impedance cause its more efficient. Wouldnt it be easier to just match up the driver to an apropriate rated 2 ohm amp since it will take less power to get there and will produce less heat doing so? Ive tried researching but I dont understand so there might just be something Im missing and would like to have an open discussion on this.

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[1aespinoza Premium Member]

What are the benefits of "getting the most out of your amp" if it comes at such a large expense?

Even though efficiency drops and heat rises at a lower Ohm load, Class D allows you to get more power out of a smaller footprint. Many have overcome this by using a more powerful amplifier and running it at 4 Ohms. The thing is that you now have a way bigger amplifier thus limiting mounting options.
Now with "full bridge" technology, the footprint gets even smaller. The issue with that tech is that your charging system has to be up to par or your full bridge amp has a high possibility of croaking. I think that issue has been improved because the negative reviews have dropped.
Now here is the main thing to consider in regards to lower efficiency; music is dynamic. What that means is that you will not always have a heavy load on the charging system because the bass is not constantly playing or of the same intensity throughout the track. Therefore that is the reason most people use 1 Ohm stable amplifiers.

 

[spokey9 5,000+ posts]

1 ohm is the selling point mainly because it's a lot cheaper to buy an amp that does 1k @ 1ohm than 1k @ 4ohm

 

[Jimi77 Premium Member]

In the OP's example, the amp is trading 20% efficiency for 5% bump in output wattage. Definitely not worth it in this case since +27% increase in power = 1db. Damping also improves as the driver's ohms increase. It's all trade offs.

Also since music is dynamic (not a max watts rms sine wave), I wonder what the difference in efficiency would be at 1 vs 2 ohms at 500wrms? My guess is the efficiency doesn't change so dramatically under those conditions and/or real world conditions.

 

[spokey9 5,000+ posts]

My guess is the efficiency doesn't change so dramatically under those conditions and/or real world conditions.

Also you gotta figure in box rise so how often would subs wired to 1 ohm actually show 1 ohm to the amp.

 

[Jimi77 Premium Member]

Also you gotta figure in box rise so how often would subs wired to 1 ohm actually show 1 ohm to the amp.

Impedance also rises as the VC heats up. While I'm glad to see amp tests, etc, the information needs to be put in proper perspective to be really useful.

 

[chillin 10+ year member]

This leads to the question of what cost more, upgraded electrical at 1ohm or a more expensive amp that can put out the same power at 4 ohms. Of course as said above, the footprint makes a difference too.

 

[Doxquzme Premium Member]

I'll always opt for an amp that makes what I need (or a little more) at 4ohms and twice what I need at 1 ohm. Everything plays nicer at 4 ohms when it can do much more at 1 or 2. Size is no longer a "huge" factor (pun intended) anymore and power is cheap. Unless one cannot afford too, that's the way I roll.

 

[Blackout67]

This leads to the question of what cost more, upgraded electrical at 1ohm or a more expensive amp that can put out the same power at 4 ohms. Of course as said above, the footprint makes a difference too.

See that's what I'm trying to figure out. Cause even if I got a high output alt of like 240 amps and my amp is pulling 140-160 amos just to make 1.2k that's like 75 percent of that alternators output then my 4 channel I think has a 40 amp fuse. So 200 amps give or take.

Vs a 2 ohm amp and 85-90 percent as most quality amps have around this efficiency at this ohm rating pulling around the same power would probably be like 110-120 amps for the 1200 sub channel and then the 40 amps for the 4 channel a good 40 amps less and the amp is gonna run cooler.

At that point I could bump the amp up to like 1800 watts and it'd probably pull the same amperage to make that power at 2 ohms cause of the higher efficiency

 

[Blackout67]

I'll always opt for an amp that makes what I need (or a little more) at 4ohms and twice what I need at 1 ohm. Everything plays nicer at 4 ohms when it can do much more at 1 or 2. Size is no longer a "huge" factor (pun intended) anymore and power is cheap. Unless one cannot afford too, that's the way I roll.

Yea usually I look at an amp that is going to have solid power across its impedance load cause music has a dynamic impedance depending on the frequency and excursion of the subwoofer and like someone else said the heat of the voice coil as well.

So if you match a subwoofer rated for "1000 RMS" with a amp that puts out that's rated power at 1ohm, then 500 and 2 ohms and 250 at 1 ohm. That amp is more like likely hella inefficient for one and then as soon as Impedance rises you're losing all that power anyways

 

[Blackout67]

In the OP's example, the amp is trading 20% efficiency for 5% bump in output wattage. Definitely not worth it in this case since +27% increase in power = 1db. Damping also improves as the driver's ohms increase. It's all trade offs.

Also since music is dynamic (not a max watts rms sine wave), I wonder what the difference in efficiency would be at 1 vs 2 ohms at 500wrms? My guess is the efficiency doesn't change so dramatically under those conditions and/or real world conditions.

Probably not so much. I'm not sure of the equation of the energy is lost as heat from the transfer of energy, but if I had to guess it'd be 50-75 per percent less heat (could be talking out of my ***)

But definitely when you get into larger numbers those efficiency percentages are even crazier. I couldn't imagine what kind of efficiency these guys running .5 or god forbid even .33 ohms are getting while clamping 5k+ watts

 

[Blackout67]

I have an SIA2500 that I remember someone dynoing 3300 @ 1 ohm, 2500 @ 2 ohms, and 2000 @ 4 ohms.

I'd love to see the efficiency on that amp for the 1 vs 4 ohms but I can't find the videoa. 4 ohms is even more efficient than 2 ohms. That JP3 amp I believe was 91 percent efficient at 4 ohms

 

[Blackout67]

Even though efficiency drops and heat rises at a lower Ohm load, Class D allows you to get more power out of a smaller footprint. Many have overcome this by using a more powerful amplifier and running it at 4 Ohms. The thing is that you now have a way bigger amplifier thus limiting mounting options.
Now with "full bridge" technology, the footprint gets even smaller. The issue with that tech is that your charging system has to be up to par or your full bridge amp has a high possibility of croaking. I think that issue has been improved because the negative reviews have dropped.
Now here is the main thing to consider in regards to lower efficiency; music is dynamic. What that means is that you will not always have a heavy load on the charging system because the bass is not constantly playing or of the same intensity throughout the track. Therefore that is the reason most people use 1 Ohm stable amplifiers.

Yea that's why I switched away from full bridge. The ones I had always got super duper hot too. Funny you mention them croaking. I had an SFB2000 full range that I sold to my buddy and I told him he needs to be super careful since he doesn't have his HO alt in yet cause of the weather and putting in that Focus was a ***** but anyways, I noticed he was always clipping it frequently and I told him you gotta be careful doing that on these full bridge amps especially cause you don't have stable voltage and like 3 months later he texted me saying the amp wont turn on and smells like burning.

As for that impedance rise part I really think it doesn't apply accurately to all music. Trance, EDM, and Dubstep have pretty constant bass throughout the whole song. Even some rap songs such as "Like That" from Future and Kendrick where the bass is almost always present and there are tons of hard transients, my voltage gets hit hard

Not to mention amp for your door speakers. Most of the class d 4 channels that put out 80-100 watts at 4 ohms x4 pull 40-60 amps and if your bass is hitting while those amps are pulling that, voltage is going to sag like a MF and going to be harder for a stock alternator to handle.

 

[Blackout67]

1 ohm is the selling point mainly because it's a lot cheaper to buy an amp that does 1k @ 1ohm than 1k @ 4ohm

Yea but that is moot if you can't make that power because of the efficiency discrepancy. No point in getting a cheap 1 ohm 1200 watt RMS amp if it's pulling twice your alternator output cause you'll have to spend even more to get your voltage stable and an alternator to keep up than you would in a quality 2 ohm amp. Big three and AGM battery is gonna be a minimum of $300 and you could probably find a higher quality 2 ohm amp for like $50 more

 

[Doxquzme Premium Member]

Yea usually I look at an amp that is going to have solid power across its impedance load cause music has a dynamic impedance depending on the frequency and excursion of the subwoofer and like someone else said the heat of the voice coil as well.

So if you match a subwoofer rated for "1000 RMS" with a amp that puts out that's rated power at 1ohm, then 500 and 2 ohms and 250 at 1 ohm. That amp is more like likely hella inefficient for one and then as soon as Impedance rises you're losing all that power anyways

I've just learned over the years, it's less cost up front to go less expensive, it's always expensive to go cheap. I have a Soundigital EVOPS 2400.1 2 ohm model that gets 1590 watts at 4 ohms, 2400.1 at 1 for two 33v2's that have a combined RMS rating of 800. watts. Plenty of wiggle room, efficient operation, better control (damping) and smaller footprint than the Hooligan HKO 3000 that it replaced. I ran that at 4 ohms too, just cooler, and they don't work as hard and are at peak efficiency.

It's kind of like a winch. If you have a 2500 lb boat, if you can, are you not better off using a 5000 pound capacity winch? The minimum will get you there but for how long?

Excess power is crazy cheap these days, even decent crazy power!