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4 Ohms or 8 Ohms?

A

ahamill

Dec 12, 2007
5
0
#1
Maybe this is a dumb question... I'm on the market for a new cab and I don't really know how much of a difference it makes if I get an 8 ohm cab vs a 4 ohm cab.

I understand that the wattage from the head is higher with a lower impedance, but does this translate to louder sound?

If this is the case, why are 8 ohm cabs even used?
 
#3
To the original poster...what is the watts of your amp at 4 ohms and what is the watts of your amp at 8 ohms and what type of music do you play and what type of venues to you plant to play in? Will you be playing indoors with PA support or will you be playing outdoors with no PA support?

I am talking about right now, this very next year, with the amp that you have and the very next cabinet that you plan to buy.
 
#4
quadebass17 said:
its impedence.

more watts are pushed at 2 ohms than 4 ohms
and more at 4 ohms, that 8 ohms.

8 ohm cabs are more efficient, from what i'm told. I'm not sure if thats the case, but you never know.

it comes out when you add extension cabs.
(adding ohms)

like two 4 ohm cabs=8
an 8 and a 4 ohm=2 i think
two 8 ohm cabs=4.


i think thats correct, might wanna google it. Theres a real good site there that explain addition and subtraction of ohms.

I personally have an 8 ohm cab.
It doesn't really matter to me, how much power it takes.

All the classic bassists only had 300 watts (AMPEG CL) at their peak most. I'm not one to go buy a 1500 Watt Bass Head.

You know?

I like SVT CL's, Fender Bassman, Sunn 300T, Orange AB200B, tube heads like that.

even lower wattage heads, some of them, are great.

agree?
Click to expand...



^No.

In a nutshell, your amp will produce the most wattage at its minimum rated impedance. Common values for this are 2,4, and 8 ohms.

You can increase volume (spl) by increasing wattage or by increasing speaker surface area (moving more air).

When you power multiple cabinets with a head, they are usually wired in parallel. According to Ohm's Law, when you wire two 8 ohm cabs in parallel you have a a resultant 4 ohm impedance. Similarly, two 4 ohm cabs in parallel will yield a 2 ohm impedance.

8 ohm cabs are not inherently more efficient, but using two 8 ohm 4x10s will be louder than using one 4 ohm 4x10 because you have twice the speaker surface area.

This topic has been discussed in detail in many threads. Try searching "impedance."

quadebass17 -- try not to answer these questions unless you are a bit more certain of your answers.
 
#9
I need some help too...I'm right now in an AP Physics class at my high school, and were about to go over ohms and electromagnetics. Isn't an Ohm a constant for the resistance in an electric circuit? And, by the Conservation of Energy Law, wouldn't that mean that this resistance (much like friction) causes heat to build up in the cab?

So wouldn't less Ohms be better?
 
#11
quadebass17 said:
WARNING: i may be wrong.

Ohms is the resistance in electriciticy in a circuit.

Heat doesn't build up in the cab, possibly the head?

but i'm quite sure it doesn't devolop heat anywhere.

then again, i haven't/never take AP physics. ;]
Click to expand...

Better. Or just don't post about this stuff ; }

Heat buildup in voice coils is one of the two major reasons speakers get destroyed. The other is mechanical overextension.
 
#12
Some numbers from Carvin:

SPEAKER COMBINATIONS and OHMS

Four x 8ohm cabinets = 2ohms
Three x 8ohm = 2.66ohms
Two x 8ohm = 4ohms
Two x 4ohm = 2ohms
One 8ohm and One 4ohm cabinet = 2.66ohms
Two 8ohm and One 4ohm = 2ohms
One 2.66ohm and One 8ohm = 2ohms
Two x 2ohm = 1ohms
Three x 4ohm = 1.33ohms
Two x 4ohm and One 8ohm = 1.6ohms
One 2.66ohm and One 4ohm= 1.6ohms



Mike
 
#13
I've got a MKII head 4ohm min. & i SAFELY run a pair of 4 ohm cabs thru it quite frequently..

DSCF0009-1.jpg


running thru this...

DSCF0011.jpg


it's a Speakermate Model 5,, ( google it )

this little box lets me SAFELY run :

one 8ohm cab
one 4ohm cab
two 8ohm cabs
two 4ohm cabs
one 8ohm & one 4ohm cab
two 8ohm & one 4ohm cab
two 4ohm & one 8ohm cabs
four 8ohm cabs
four 4ohm cabs

have run the LMII with two 4ohm cabs for hours,,, no problem

the big advantage is,, if i only need one cab,, i'm running full power at 4ohm, ( as i only own 4ohm cabs )

& besides,, if i ever cook the LMII,, it's gotta 2year no questions asked exchange warranty at GC.
 
#14
NorCal Dog said:
I've got a MKII head 4ohm min. & i SAFELY run a pair of 4 ohm cabs thru it quite frequently..

DSCF0009-1.jpg


running thru this...

DSCF0011.jpg


it's a Speakermate Model 5,, ( google it )

this little box lets me SAFELY run :

one 8ohm cab
one 4ohm cab
two 8ohm cabs
two 4ohm cabs
one 8ohm & one 4ohm cab
two 8ohm & one 4ohm cab
two 4ohm & one 8ohm cabs
four 8ohm cabs
four 4ohm cabs

have run the LMII with two 4ohm cabs for hours,,, no problem

the big advantage is,, if i only need one cab,, i'm running full power at 4ohm, ( as i only own 4ohm cabs )

& besides,, if i ever cook the LMII,, it's gotta 2year no questions asked exchange warranty at GC.
Click to expand...

and I could safely drive at the speed limit by keeping the gas pedal floored and my foot on the brake....but I'd be using twice as much gas and needlessly revving my engine. ;)
 
#17
dogbass said:
and I could safely drive at the speed limit by keeping the gas pedal floored and my foot on the brake....but I'd be using twice as much gas and needlessly revving my engine. ;)
Click to expand...

all i'm trying to do is let people know that they have options out there in the bass world.

i'm just taking a different approach,,, you may not want to do so & that's cool too.. :)

but using the above analogy,, i'd rather have my foot on the brake,, than just idling along with an 8ohm cab...

& the really cool thing is,, i can if that's what i choose to do.. :hyper::hyper:

god i love the freedom to do as i choose.. :bassist:
 
#18
rsrhcp said:
I need some help too...I'm right now in an AP Physics class at my high school, and were about to go over ohms and electromagnetics. Isn't an Ohm a constant for the resistance in an electric circuit? And, by the Conservation of Energy Law, wouldn't that mean that this resistance (much like friction) causes heat to build up in the cab?

So wouldn't less Ohms be better?
Click to expand...
Less ohms would mean less heat on the drivers, but it's also harder on the amp as it has to output more power. That's why an amp will fail if you have too little resistance from the speakers. The increased power is also harder on the speakers.
 
#19
Thanks to everyone who replied. It didn't even occur to me to search for impedance before starting a new thread. I tried searching for things like "4 vs 8 ohms" and "4 ohms or 8 ohms".

When I posted the question wasn't even thinking about how running multiple cabs in parallel affects the load on the amp.

That said, the question is cleared up for me.
 
#20
running the Speakermate with two 4ohm cabs puts a 8.3ohm load on the head.. it may be a little harsh on my speakers,, but not any different than running a 4ohm cab with an 8ohm min head,,, it's when you go the other way, ( ie,, 8ohm cab,, 4ohm min head ) you got problems

i consider my components as mass produced tools, to get the tone i want. i don't always run both cabs,, but when the need arises, I can.. & please re-read the last line of my OP.
 

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