I'm looking at a dual 8" sub set up with a single amp.

Here's my issue:

Would I be better off running:
a) two 4ohm subs in parrallel to an amp bridged for 400W (rms @ 2 ohm load)
or b) two 8ohm subs in parrallel to an amp bridged for 400W (rms @ 4 ohm load)

granted which one I pick will be based on available speakers/amps... but many 8" subs seem to be available in 2ohm, 4ohm and 8ohm configurations (and more possibilities with dual voice coils).

Amps also seem to vary on ohm load ability.

So... do I tap an amp with a 2ohm load? or a 4 ohm load? If the rated wattage is equal, what would be the PROS/CONS?

(I guess the "bridged" part doesn't matter... these could just as easily be mono-amps as well)

 

The only thing I've come up with is that
i) the 2ohm ohm load may let the speakers run cooler (I think... gotta think about that for a while... current vs. power hmmm....),
and ii) the 4ohm load will let the amp run cooler (for the same rated power).

anyone have an idea? I'm not talking about the same amp in each set up (obviously... or else the 2 ohm load is pointless), but the same POWER output through a separate ohm load.

My gut feeling is both set ups would be equal from a power standpoint, but the heat would be greater on the 2 ohm set up, and the 2 ohm amp would probably be a better sound quality (since flagship amps tend to be made for low-ohm loads I assume quality control is better vs. their 4 ohm counterparts).

 

If you go with a mono class D subwoofer amplifier you won't have to worry about any heat problems. I'm running an MTX Thunder 6500D (600x1@2ohms) and a Thunder 4202 (75x2@4ohms). Out of curiousity one day I checked to see how hot the amps were after having the tunes cranked for a while. The 4202 was VERY warm to the touch while the 6500D wasn't warm at all.

 

Good point, although I havn't really picked any specific amp yet. When I do I'll try to get a D or T class amp. Last I checked the D class amps were pretty pricy (granted that was a few years ago... had a HP bug for the past 3 years or so )

Still... what would be a better set up? 2 or 4 ohm loads?

Is there a sound quality difference? What about heat generation from the speakers? What about current draw on the vehicle? (is a lower ohm load inherently more efficient?)

Thanks for your input guys...

 

I know this is all in theory, but remember that almost all 2-channel amps are only stable to 4 ohms when bridged. If it were a mono amp..... the lower the stable impedence, the higher the output power. So....what's the question again?lol

 

yeah, essientally the internal bridge just saves me from the wiring hassel of parrallel wiring speakers I guess.

ok....

Given a mono-line amp, and a single speaker, what would be a higher quality set up:

1000W @ 2 ohms

or 1000W @ 4 ohms


Now understand that I don't care about getting much louder than that for this example... just looking at signal/sound quality and any effects of thermal effiency.

Any difference? (Besides the idea that the 4 ohm amp above would probably support 2000W @ 2 ohms... and could be used in future upgrades).

 

ok ur theory on lowering ohms is wrong.. if u take a look at bose for example they run at 8 ohms for clarity.. the lower u lower ur ohms the less clarity u get that is just common sense. all amps are built diff some will stay clear even though they are higher powered at lower ohms but look at there price. u could buy 2 dual 4 ohms and buy a amp stable at 2 ohms and run them parrlel for best opower have fun

 

Not true....

I've got 3 different 2ch amps that are installed in cars currently... all are rated for either 2 ohm mono, or the large Audiobahn one in my Bird is rated at 1 ohm, and running awesome at 1 ohm...

 

It IS true! Remember... he said "almost all 2-channel amps". There are very few amps on the market that can be bridged and run at 2ohms.

I still recommend a mono class D sub amp. I'd take that over a bridged 2-channel amp any day.

The higher levels of distortion produced by an amp into 2ohms as opposed to 4ohms is a NON issue. The subwoofer itself will distort far more than the amplifier ever will.

 

Ok, that's fair....

I guess I must have some of the few amps... seeing I own 2 different amps that are both capabile of 1 ohm mono operation...

 

You'd end up with the same thing in the end. As long as the amp is designed to take the load you are giving it then I wouldn't worry about which set up you go with. (lets not even argue about the differences in clarity or any of that. I mean, as long as a quality name brand amp is used I doubt a person would be able to tell the difference between the 2 ohm load and 4 ohm load on an amp as long as they are not clipping and are stable to those ratings)

Really, it's a game of making sure you give the amp the right load. If they are good quality made amps that give true wattage ratings then you should be okay in both situations.

 

Yeah, that's a nice amp. It's rated at 500 x 1 @ 2 ohms but the one I have will push 624 watts @ 2 ohms on battery voltage. Estimating it's pushing 700 to 750 watts at 14.4 volts. I picked it up from a friend for $150, heck of a deal and he needed the moeny to buy some other speakers so I said why not.

 

I wouldn't say that he's wrong and I wouldn't say you are right either. If you are talking Bose in the home, their are reasons why they are running 8 ohm. Think about it, they have a lot of voltage to work with coming right from the wall. Why make the amp have to push a bunch of current into a lower ohm load when you can keep the load higher (like 8 ohms) and push less current and have a higher voltage go out to the speaker on the output stage. Remember, the more current that is pushed out the more heat you produce and the higher the quality components you are going to need to make things work.

In the car audio enviroment it makes sense that 4 ohm and 2 ohm loads are common. You are starting out with 12.5 to 14.4 or so volts so you don't need to step it up as much to produce the same power. For example:

A: For a home amp to produce 100 watts at 8 ohms you would need:

Voltage: 28.28 Volts
Ohms: 8 Ohms
Current: 3.535 Amps

B: For a car amp to procude 100 watts at 4 ohms you would need:

Voltage: 20 Volts
Ohms: 4 Ohms
Current: 5 Amps

C: For a car amp to procude 100 watts at 2 ohms you would need:

Voltage: 14.14 Volts
Ohms: 2 Ohms
Current: 7.07 Amps

D: For a car amp to produce 100 watts at 1 ohm you could need:

Voltage: 10 Volts
Ohms: 1 Ohms
Current: 10 Amps

As you can see, as the impedance drops the current demand goes up. Keep in mind though that speakers are run off of an AC signal so it's really impedance we are talking about here and it's frequency dependance so the amp shows what would happen if the certain ohm load was presented to the amp.


Like I said above, if you lower the impedance load on the amp, the more current you are going to need to produce the same power. Hence, more current means you'll need higher quality components in the amp that can take the harsher load. (excess heat the current will produce and also the components that can actually flow the higher current demands)

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In the end, it depends on a lot of factors if you ask me. Name the amps you are thinking about and that would help me give you suggestions for saying a 1000 watt amp compared to antoher 1000 watt amp doesn't mean anything really.

If you said a 1500 watt MTX mono block amp veres the 1500 watt Rockford 1500BD, then we are talking about something that can be compared.

 

Just wait until all car manufacturer's switch to that new 42V system! This will TOTALLY revolutionize the car audio industry as we know it! I can't wait!

 

ok if own an mmats amp 1200 watts at 2 ohms.i sent it to mmats and had it reworked now it is 1900 watts at 2 ohms. i had it pushing 4 15 w3s (jl audio) and ported box. once it got that loud there was no noticable distortion and if there was, i woldnt be able to hear it. i have had plenty of amps and the( this sis common sense) more money u spend the better the product , so if u want clarity spend the money or dont be happy. that is one thing every audio person has learned. well i did atleast. i tried byin the cheap **** and makin it loud and clear ,,,, yeah tht lasted for a week or so, then i had to buy somthin new. no wi am down to 1 15 w3( sold the rest) a mmats amp, a jbl amp, pionner 7300 deck 00 gauge wiring. i am just trying to say dont go the cheap route, u most likely wont be happy