# Why choose a 2ohm over a 4ohm speaker/sub and vice versa?



## Shmee (Dec 22, 2013)

I searched but got too many obscure results not at all to do with what i was interested in.


Is there a better reason to go with one over the other or is it just preference. From what I have seen, the lower the resistance on the speaker the more power out of an amp to that speaker. I would assume that this is what most people are after. maximum output per dollar. So why offer a 2 and 4ohm version?

is there a better application for one over the other? SPL/SQ?
is it a matter of heat dissipation of the amp or the speaker?
is it a matter of flexibility to upgrade to better gear as time goes?
Matching outputs of amps to speaker/sub choices?
Personal preference?



I'm looking to order my new gear soon and this popped into my head and wanted to know if my plan to build my SQ system around 2ohm speakers/subs was the right choice or not.


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## ShaneInMN (Sep 27, 2013)

It's because there are a lot of combinations that you can do with the speakers, and some amps are rated stable at even 1 ohm. A single sub with single voice coil gives you one option. Add another sub or two, and you get more options, dual voice coils, more options.

Series Parallel Speaker Impedance


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## Alrojoca (Oct 5, 2012)

In simple words, just to draw more power and get higher spl for competition.

There may be some disputes regarding SQ is better with 4 ohm loads but that is a different subject.

If you buy 2 subs at 4 ohms each single coils you get a 2 ohm load and need to make sure your amp can handle a parallel connection.

If you get 2 dual 4 ohm voice coils connected in parallel you get a 4 ohm load since each gives you a 8 ohm load

2 two oms dual VC in parallel you get 2 ohms 

2 single 2ohms gives you unsafe load unless the amp can handle it.

You can also connect them in series but then the load increases too much it may not be a good match for the amp unless it is one high end amp with stable power in 2 and 4 ohms.

Bottom line if you plan to buy 2 subs connected to a single amp you need to know the right combination to get the right load for the amp you plan to use


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## ccapil (Jun 1, 2013)

In short this is why you would use one over the other etc:

- There is no difference between 2 and 4 ohm, sound wise. So 99% of the time you can't hear if a amp has a 2 or 4 ohm load.
- Power. Some people want to get the most out of there amp, so for example you buy a mono amp. It is rated at 600 watts at 4 ohm and 1000 watts at 2 ohm. If you want to get the most power out of that amp, then wire it for a 2 ohm load (1000 watts)
- Wiring. You have to wire speakers / Subs to an impedance load to the amplifier. So you can either have a 1,2,4 ohm load are the most common. It just helps to wire drivers up to the amplifier at the correct ohm load. Most spl guys want the most out of there big wattage amplifers, so they wire their subs to the amp for a 1ohm load, only if the amp is 1 ohm stable. 1 ohm gives you the most power (in theory) out of the amplifer, but it also has the ability to draw the most current out of all the ohm loads. 
Amps have many power rating at different ohm loads to offer many different types of drivers to be hooked up, not just one. Eg, single voice coil at 1,2,4 etc ohms, dual voice coils in parallel or series, at 1,2,4 etc ohm loads. It offers a variety of possibilities. 
If you are building your system, I would look at the speakers you want first, then buy the amplifer, you can do it either way, as long as you have the correct impedance at the amplifer and wire it correctly.


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## Alrojoca (Oct 5, 2012)

Something to consider is the heat, heat is the enemy of components and affects their life, the lower the load the more heat for the amp and drivers.

You may want to consider getting subs with higher efficiency this will make it easier for the amp by not having to turn the volume higher for more bass or sound.

This is another subject where there are some controversies, some say expensive inefficient drivers provide better SQ but it does not always apply. While others say that more efficient drivers with higher sensitivity deliver more spl but not better SQ, it does not always apply but many expensive good sounding drivers do sound good.

I guess we can say the 4 ohm better SQ is myth the same for higher sensitivity drivers not having the best SQ


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## Shmee (Dec 22, 2013)

Ok, that all makes sense. However, when it comes to wiring the speakers/subs to the amp, is the wattage then split equally between the components or does each component get the advertised value? 
If I had a mono amp with 800W @ 14.4V and 2ohms and had 2x 2ohm DVC subs, would each sub get the full 800W or would that 800 be split between them?


As a more specific example, I'm looking at a pair of SA-10 D2 matched to a SA SAZ-1200D amp. Subs are rated at 600W RMS and the amp outputs 790W RMS @ 14.4 and 2ohm or 1200W @ 1ohm. Is there a way to wire these into a 1ohm load to get the full 1200W out or what would be the best method to extra the most usable power for these subs.

If I can load the amp to 1ohm, would it be advisable to mount a couple of computer fans in the amp rack to blow air over the amps to cooling?


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## ccapil (Jun 1, 2013)

Shmee said:


> Ok, that all makes sense. However, when it comes to wiring the speakers/subs to the amp, is the wattage then split equally between the components or does each component get the advertised value?
> If I had a mono amp with 800W @ 14.4V and 2ohms and had 2x 2ohm DVC subs, would each sub get the full 800W or would that 800 be split between them?
> 
> 
> ...


For your first question, if you had 2 subs that are 800 watts, they do not get 800 watts each. If the amp is rated at 800 watts then how can it deliver 1600 watts? (800 to each sub)
The power is split between the subs. But only if A, they are wired correctly and B, both subs are exactly the same, so same voice coils, wattage etc. If they are not then the power won't get split up evenly. 
Go on to this site, to help you wire subs up if you don't know it off by heart:

Subwoofer Wiring Diagrams at Sonic Electronix

No you cannot wire 2 dual 2 ohm subs to an impedance of 1 ohm at the amplifer. It's either 0.5 or 2 ohm. I would look at different subs or buy the dual 4 ohm subs so you can wire them in parallel to the amp at 1 ohm.


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## mid_life_crisis (Dec 6, 2013)

There is a difference in sound quality, but the average person can't hear it anyway, so the point is moot.
If each sub is a single coil 2 ohm design, you just divide that number by the number of subs to get the load, so 2/2=1 ohm load. Be careful with this though. If the subs are dual voice coil, the power rating assumes both coils are in use. So if you have a pair of subs with 2 voice coils each at 2 ohms each, you could wire them together to be 2 ohms or 1/2 an ohm, (2+2)/2=2 or (2/2)/2=.5. If the amp is 1 ohm stable, you would have to go with its 2 ohm power rating.
Don't wire your subs in series if you care about the SQ. You have undoubtedly seen plenty about time alignment and seen how sometimes installers will reverse the phase on a sub because it is 180 degrees out of phase with the rest of the system, or so close that it is easier to align it by first reversing it. If you wire your subs in series, you are creating a situation where they are 90 degrees shifted from each other, and there is nothing reasonable you can do about it. 
As long as the amp is mounted somewhere that there is plenty of air around the heatsinks and is well designed, additional fans should not be required. We're assuming of course that the designer knew what they were doing. The heatsinks should be large enough or there should be built in fans. You might look for reviews to see how the amp held up for others. On the other hand, an electrically and acoustically quiet fan couldn't hurt.


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## PsyCLown (May 17, 2013)

So coming from more of a Hi Fi background, generally 8ohm is the standard for most drivers.
When something with a lower impedance appears, sometimes talk arises about how well an amp drives / controls the speakers at that impedance.

Or when someone is designing a system, they have something planned and they listen to it, decide to do something else which will increase the impedance (or lower it) and they often refer to the fact that their amps much prefer that. Obviously it differs from amp to amp.

What I am more asking about here is the "control" which the amp has over the driver and how the impedance may effect it. It is something I have yet to see being brought up with regards to car audio, which is a bit strange considering in car audio you generally run a lower impedance load, 2 and 4 being the most common.
There does not seem to be any lack of dual voice coil subwoofers out there either, it could be seen as common practice.


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## Shmee (Dec 22, 2013)

ccapil and mid-life_crisis, thanks.

So if I'm understanding this correctly, if I wired those 2 SA-10 *D4* (4ohm) subs (at 600W RMS each) going by this:








and powered them with the SAZ-1200D, I'd be at a 1ohm mono load and I'd get 1200W out of the amp. So then that 1200W split between the 2 subs, or 600W per sub of clean power and in phase?
Would this be ideal for powering the subs and wouldn't it be best for SQ? 


Aside from the heat, are there any disadvantages to running this setup? I will probably run a couple of small computer fans just for piece of mind and to ensure things stay cool.

Unless I'm crazy, or I have forgotten basic electronic theory, that is a completely parallel wiring, so good for SQ if I'm understanding it correctly, and not a parallel-series wiring method like this: 









Here are the specs on the amp and subs I'm looking at:
SAZ-1200D
SA Series


And I'm not sure if it matters or not but I'd be running these subs in sealed enclosures.


Cheers
Mitch


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## PsyCLown (May 17, 2013)

Shmee said:


> So if I'm understanding this correctly, if I wired those 2 SA-10 *D4* (4ohm) subs (at 600W RMS each) going by this:
> 
> 
> 
> ...


Yes, that is correct.




Shmee said:


> And I'm not sure if it matters or not but I'd be running these subs in sealed enclosures.


Sealed or ported, won't make a difference really.
The same applies, sealed often has less bass extension when compared to a low tuned ported enclosure etc. Impedance won't matter much, more power for a sealed unit could be good though, especially if you have the xmax and are able to EQ it for better low end response


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## Alrojoca (Oct 5, 2012)

My opinion about this dual sub thing is that you need to have extra power on the amp to make it worth it. If we have 2 subs handling 300wats each and and the amp only puts 300 w at 2 ohms, this means each sub will get 150 w with a 2 ohm final load.

I will take just one single 2 ohm load sub instead of 2 four ohms subs, and drive it with 300 watts. 

What's is the point of having that extra sub driven at half the power? Move more air inside the car? Maybe not even that, It will not give me significant extra bass, maybe some extra spl but not worth the extra cost and space and bass only detectable by being measured and not by human ears.

Then you have the power limits when you exceed some power where, when it is increased money is being wasted since there will not be significant differences, I think it was mentioned once you pass certain power with the same number of drivers there is no audible difference.

Any thoughts? based on experience numbers or calculations and what humans can detect and not just simply saying 2 subs are better than one just because 2 is a higher than 1? V


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## Shmee (Dec 22, 2013)

Ok, so you are saying there is no point to running 2 subs, properly powered?
Or there is not point in running 2 subs, underpowered?


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## Alrojoca (Oct 5, 2012)

Shmee said:


> Ok, so you are saying there is no point to running 2 subs, properly powered?
> Or there is not point in running 2 subs, underpowered?



yes 2 subs under powered versus one with twice the power


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