How do you run parallel subs and amp

[Trust33]

hi all when running 2 subs (4ohm) in parallel thats 2ohm's each.Do you run a amp that is 4ohm rated??? how do you run the subs in parallel? do they have to have rca in and out on the sub for this to be done.and what sort of amp do you use i.e.(mono)?

im not doing it im just curious about it.

[snapx]

ive got two subs runnin of one amp at the moment and the set up ive got is two seperate rca cable running into my amp as the guys i bought my amp and subs from gave them to me saying it would be better and then ive bridged the subs one on the front channel and the other on the rear.. my amp is 4ohm rated but i dunno if its eseential hppe it helps a little hopefully some 1 else be able to answer it

[Fhrx]

You'll find most car audio amplifiers are optimised for operation with a 4ohm load. Some amplifiers (usually class D mono-block subwoofer amps) are designed to run much lower resistance, even down to as little as 0.25ohm a channel.

So when talking about amplifiers go off the 4ohm rating and aim for subwoofer combinations that equal 4ohms because while amps may be able to run at 2ohms, they usually have better stats at 4ohms.

This is a generalisation, like any rule of thumb there are exceptions of course...

If you want to deliberately run lower, you'll need one of the afore mentioned specialise mono-blocks or similar multi-channel amplifier.

[Trust33]

So a monoblock amp rated @4ohms 1000watts then 2 subs @2ohms 500watts each.Wire the subs in series and viola...pretty much...

But the thing that i dont get is do the subs have to have 2 sets of rca's or 1 set of rca's to be daisy chained? :spamcan:

[Nav2k]

1 set.

its a monoblock

it can only accept 1 set of input cos its ment to have 1 set of outputs.

wiring 2 sets of outputs makes it parallel not series.

also if u have an amp rated at 1000watts rms at 4ohms, its gonna be like 2000wrms at 2ohms, not the same value. cos the resistance is decreased. (ohms law v=ir)

each sub will get half this 2ohm power.

[Edge]

In case you didn't get that

here is the correct statement

Monoblock amp rated @4ohms 1000watts

then 2 x4ohm subs =gives you> 2ohms and 2000w

you can also buy 8ohm subs and put two of these together to give you 4ohms.

[Edge]

Nav2k

how important is having the capacitor? What equipment is it meant to protect - do skylines really need it. I would have thought the battery acts as a capacitor to some extent. Does the 1F cap stop voltages going up and down such as when starting?

Or is it merely there for sound quality?

[Trust33]

1 set.

its a monoblock

it can only accept 1 set of input cos its ment to have 1 set of outputs.

wiring 2 sets of outputs makes it parallel not series.

also if u have an amp rated at 1000watts rms at 4ohms, its gonna be like 2000wrms at 2ohms, not the same value.  cos the resistance is decreased.  (ohms law v=ir)

each sub will get half this 2ohm power.

I didnt know that a there was a decrease in ohms occured when running the subs like this causin it to load i allways thought that ther was only a problem when the amp was 4 ohms and the two subs in parallel where 4 ohms each also.... :bat:

i hope you get your s-14 it looks like it'll have a killer sound system to go with it.

[Fhrx]

A cap is a bandaid fix for you average (read; not SPL comp) car stereo. If the charging system is struggling with the demand for power, look at upgrading your battery and / or charging system before adding a cap.

After installing literally thousands of systems, I have only ever needed a cap on the dedicated SPL vehicles…

[Edge]

Thanks - thats what I did and wasn't sure if a capacitor was needed as well.

I got a 1100 CCA battery with 70Ah rating to run with my system.

I will be testing my alternator as well - know the best way to do this?

Also I am planning to move the battery to the boot this week as I have heard it is better closer to the amp - would this be right? I am currently sourcing vent pipes and 2ga wiring for it.

yep... R33 4dr series 2 has battery under bonnet.

[Edge]

Trust33

Have one set of rcas to go from head unit to input of monoblock amp.

The monoblock amp ussually has screw connectors with place to wire both speakers using screws to make connection to the wires. 4 wires can be screwed into the amp in total then 2 wires to each sub.

[strutto]

R33 4dr series 2 has battery under bonnet.

Serious?

Got pics?

[Nav2k]

nup, ur right, a cap doesnt really do much. Only reason i got it was that i got it cheap brand new off US for $100 AU delivered when theyre about $300 brand new here. + it has a ricey voltage display. When i had my old battery, it stopped headlight dimming quite a bit. I have not noticed any SQ difference though, i never have from loss of current.

About the impedence question, if u remmber back to high school physics where v=ir, when the resistance is lowered, ie. from 4ohms to 2ohms, u need more current to make sure the law holds. and power is composed of current and voltage (which is constant).

so an amp at 4ohms will produce less power than an amp running at 2ohms.

thnx, hope to get the s14 soon and install all this stuff! taking a long time though :~(( slim pickins

[Edge]

In answer to your question the way you originally put it - you will need a 2ohm rated amp to run two 4ohm subs wired in parallel.

if you run the wires the way I suggeted earlier you will have 4ohms per sub but only half the power.

You can bridge the outputs on the amp by putting a total two wires - one in the first positive and one in the last negative. This gives you twice the power.

If you are buying subs for this it would be better to buy two 8ohm subs and wire them in parallel so that you have 4ohms altogether to run with this.

If you put two 4 ohm subs in parallel by wiring the subs with the negative-negative and positive-positive connected to each other then to the the enclosure terminals. You would have 2ohms altogether and twice the watts.

The important thing is to check what the amp is rated at.

Just make sure it matches check both the watts rating and the ohms specification of the amp.

JBhifi would explain it to you as part of their sales.

Also you may be better off getting a single 2ohm dual voice coil in series which gives you 4ohms and better quality sound.