Pros and Cons-4ohm or 8ohm

[TheVoiceless]

Hey!!

So I posted my first thread and got some really great replies. So I wanted to post another one.

Can someone explain to me the pros and cons to playing at 4ohm or 8ohms?

Thanks

 

[KJung]

With tube amps, I guess it doesn't really matter, as long as you have a 4ohm or 8 ohm tap.

For SS amps, if you have a very small cab (like a 112), it probably doesn't matter, since most SS amps put out enough power at 8ohms to drive most small cabs to full volume. (The exception here are very low SPL cabs like the Acme cabs. Even the small ones prefer a lot of power, and some moderate power SS heads won't put out the oomph needed).

If you have a very powerful head that puts out 500+ watts into 8ohms, it probably doesn't matter, since you probably won't push the amp past its rated operating wattage or kick in power limiting at 8ohms.

With 'stereo' type amps (like the WT800), 8ohm operation, even with large cabs, is probably better than 4ohms, since 8ohm operation gets most of the wattage out of the head in bridged mode, but does not push its limits (4ohm bridged equals 2ohm operate per side).

The only time it really seems to make a difference to me is when you have a large cab (212 or 410) and a relatively low powered SS head. Running a small SS head at 8ohms into a large cab (i.e., at 300 watts or less) often times results in the head lacking headroom, resulting in its power amp limiting circuitry to kick in. To my ear, 4ohm operation with relatively large cabs and relatively low power SS heads like the Shuttle 6.0, the Markbass LMII/F1, the AG500, etc., etc REALLY can help out and result in not only a touch more volume, but a much nicer low end and treble response when digging in.

IMO, that covers it

 

[Wes Whitmore]

A 4 ohm amp allows you to run 2 8 ohm cabs, netting you more output than just the single. Most amps double their power when you half the ohm load, which is nice for adding to the system when you need it. I try to match 8 ohm amp power with the power handling of my 8 ohm cab. If I need the extra volume, just buy another 8 ohm cab and plug it in. It's modular.

 

[waveman]

on a more basic level, 4ohm cabs cannot be added to unless you are running an amp that can handle 2ohm load. However, it isn't impossible to add another 4ohm cab and make it 8ohm (wired series), but doing so you would loose some of the wattage your amp has available to power the speakers.

 

[KJung]

A 4 ohm amp allows you to run 2 8 ohm cabs, netting you more output than just the single. Most amps double their power when you half the ohm load, which is nice for adding to the system when you need it. I try to match 8 ohm amp power with the power handling of my 8 ohm cab. If I need the extra volume, just buy another 8 ohm cab and plug it in. It's modular.

I interpreted the question from as being from the amplifier's 'point of view'.

+1 to your comments from the 'speaker' point of view. The optimal combination of cabs is two small 8ohm cabs, or a single large 4ohm cab, given that most SS heads are 'optimized' for 4ohm operation.

While many amps have been 'safe' for 2 ohm operation for many years, it was typically at the expense of poorer specs and hot operation. Now, there are at least some amps (some of the Genz and Mesa models) that are actually designed to run at 2ohms, meaning that you can pretty much mix and match any cabs you want, as long as you don't go below 2ohms.

 

[rappa29]

The only time it really seems to make a difference to me is when you have a large cab (212 or 410) and a relatively low powered SS head. Running a small SS head at 8ohms into a large cab (i.e., at 300 watts or less) often times results in the head lacking headroom, resulting in its power amp limiting circuitry to kick in.

Say that again? I'm confused about the small SS head at 8ohms into a large cab (300watts or less). Do you mean a head that runs 300w or less and a cab that handles >300w?

 

[TheVoiceless]

WOW!!! Great responses. Sorry for the over excitement but I'm new to the community.

After reading your replies I realized that I am using my amp to its full potential, (GK1001RB-II) But I am running it at full range and not bi amped.

I'm having another conversation with my guitar player through email discussing if its worth it for me to replace my old GK cabs for new ones to utilize the Bi-amp and speakon options, or should I just replace my speakers saving a ton of cash that way.

I would be willing to move up to the new cabs but not sure if is justified. I am on a budget but like you all know tone comes first. So if you have an opinion please send it my way.

Peace!!!

 

[KJung]

Say that again? I'm confused about the small SS head at 8ohms into a large cab (300watts or less). Do you mean a head that runs 300w or less and a cab that handles >300w?

I was referring to the power output of the head. The power rating of the cab is kind of an 'uninteresting' spec for the most part.

The point I was trying to make is that the typical 8ohm output of around 300 watts (the typical wattage of heads like the LMII, the AG500, the TF550B, the Eden WT550, the Shuttle 6.0, etc., etc.) is plenty to drive, for example, a 112 cab, since most single speakers can't take much more than that anyway. However, if you have a big honkin' 410, or a 212 cab or whatever, the difference between the 300 watt output of a head like those sited above and the 500 watts 'full power' at 4ohms is quite noticable.

 

[KJung]

WOW!!! Great responses. Sorry for the over excitement but I'm new to the community.

After reading your replies I realized that I am using my amp to its full potential, (GK1001RB-II) But I am running it at full range and not bi amped.

I'm having another conversation with my guitar player through email discussing if its worth it for me to replace my old GK cabs for new ones to utilize the Bi-amp and speakon options, or should I just replace my speakers saving a ton of cash that way.

I would be willing to move up to the new cabs but not sure if is justified. I am on a budget but like you all know tone comes first. So if you have an opinion please send it my way.

Peace!!!

All the biamp option does is separate the tweeter from the primary power amp. The only real advantage of this (and I believe the reason that GK did this) is that overdriven, distorted output sounds pretty nasty through a tweeter. Since part of the inherent capability of the GK amps is a unique 'solid state overdrive' tone, GK designed the amp so that when you use it with their 'biamp capable two way speakers', you can get that GK grind through the woofers, and still have a clean, crisp, pleasant sounding high end through the tweeter (since the tweeter is being driver by a separate amp.

So, if biamp capability is your primary reason for 'upgrading' your cabs, I would say it's only worth it if you are experiencing nasty, harsh output from your tweeter due to using the boost knob for a grindy tone from your 1001.

 

[TheVoiceless]

Well that certainly helps me make my decision. I would much rather apply the money I would save by replacing my speakers into a Pro Tools rig.

Very helpful KJung

 

[Wes Whitmore]

Great biamp post.
I dont think I would replace them just to biamp. In fact, it would probably make it worse because a cab is supposed to be designed for the woofer that you load in it. Ask yourself what you don't like about your sound. Just replacing the cab with something different (used is fine) might be the best bet.
The good thing is that you can rewire any cab to take advantage of your biamp feature of that amp. All you need to do is replace the jack on the cab with a 4 pole speakon, and disconnect the horn from the crossover in the cab and wire it to the new jack. If you do it, we can trace out the wires in my Gk cab and relay that info to you. If that's the only head you use, then you are fine. To take it further, you can put the horn on a switch mounted to the jack plate that puts it back the way it came, so you can still run the horn with a single amp channel.
It really depends if you want to use the horn or not. I don't even have mine on. 5K is pretty high. The mids are what are probably most important to me, and the woofer does most of that. Slappers and tappers like the horn though.
Wes

 

[TheVoiceless]

The cabs I have (1x15 and 4x10) don't have a horn in them. Which I really like. Cause I have used a cab with a horn and I blew it with a effect I was using. Besides that I'm looking for more mid/low end.

So by not having a horn do I really need the Bi-amp ability? I like the idea of swapping my 1/4" for speakon. So any info on how to do that would be great.

 

[KJung]

The cabs I have (1x15 and 4x10) don't have a horn in them. Which I really like. Cause I have used a cab with a horn and I blew it with a effect I was using. Besides that I'm looking for more mid/low end.

So by not having a horn do I really need the Bi-amp ability? I like the idea of swapping my 1/4" for speakon. So any info on how to do that would be great.

If neither of your cabs have a tweeter, then the biamp capability of your GK head is not usable.

Again, though, if you like the sound of a tweeter in your signal chain, and use some extreme effects, then the biamp capability of the GK heads is perfect, since it will send a separate, pure signal to the tweeter (if you either buy a GK cab, or make the modifications on other two way cabs as mentioned in one of the above posts, and use that 4 pin speakon cable). If you dig the more vintage sound of your two one way cabs, then just keep cranking it like you are doing and ignore the small 50 watt 'biamp' module and capability of the GK head you have.

 

[Franco Bollo]

Regarding SS amps, I think the following are good guidelines:

If you're going to run a single speaker cabinet from a mono SS amp, I'd go for 4 ohms, since you get more power out of the amp.

If you're going to run two cabs from a single mono SS amp, I'd go with 8 ohms for each. The amp will see a 4 ohm load. With two 4 ohm cabs, the amp would see only a 2 ohm load.

If you're going to run a stereo amp bridged, I'd go for 8 ohms, because if you bridge a stereo amp into 4 ohms, each channel sees just 2 ohms.

If you are going to run two cabs from a stereo SS amp, I'd go for two 4 ohm cabs and run each from its own channel.

 

[dream_bass]

so if I have an ss amp with (or not) tube preamp,power around 400w or + 500w you sugest that I need an 4 ohm cabinet(4x10's) ? I mean its better than using an 8 ohm ?
thanx

 

[Franco Bollo]

so if I have an ss amp with (or not) tube preamp,power around 400w or + 500w you sugest that I need an 4 ohm cabinet(4x10's) ? I mean its better than using an 8 ohm ?

Let me clarify. My comments regarding solid-state amps refer to the poweramp section. Doesn't make any difference if the preamp is tube or SS.

Most if not all solid-state amps give different power ratings for 4 ohm and 8 ohm loads, with the rated power into a 4 ohm load being the greater value. Therefore you will have more available power into a 4 ohm load.

Now of course the same is true for a 2 ohm load (if the amp is rated to drive 2 ohms). However, my personal opinion is that I don't like driving a 2 ohm load with a SS amp.

Note also that if you have a very powerful poweramp, it could be possible that the amp would put out the full rated power of the speaker even at 8 ohms. In this case you would have no benefit of additional power into the 4 ohm load and in fact the 8 ohm speaker could give the option of adding a second speaker.

Confused yet?

 

[dream_bass]

Let me clarify. My comments regarding solid-state amps refer to the poweramp section. Doesn't make any difference if the preamp is tube or SS.

Most if not all solid-state amps give different power ratings for 4 ohm and 8 ohm loads, with the rated power into a 4 ohm load being the greater value. Therefore you will have more available power into a 4 ohm load.

Now of course the same is true for a 2 ohm load (if the amp is rated to drive 2 ohms). However, my personal opinion is that I don't like driving a 2 ohm load with a SS amp.

Note also that if you have a very powerful poweramp, it could be possible that the amp would put out the full rated power of the speaker even at 8 ohms. In this case you would have no benefit of additional power into the 4 ohm load and in fact the 8 ohm speaker could give the option of adding a second speaker.

Confused yet?

ahhhhh,so to make it easy...if I have an 500w amp and I want just one 4x10's should I take the 4ohm or the 8 ohm ? to have good volume and punch
cheers and thanx

 

[winstonthecat]

ahhhhh,so to make it easy...if I have an 500w amp and I want just one 4x10's should I take the 4ohm or the 8 ohm ? to have good volume and punch
cheers and thanx

If you only have one cab, and will not want to add another cab, then you should get a 4 ohm cab to get maximum power from your amp.

 

[dream_bass]

If you only have one cab, and will not want to add another cab, then you should get a 4 ohm cab to get maximum power from your amp.

thanx a lot man
no I dont want to add another cab,cause its imposible to cary them at concerts...so I only need one! so its going to be 4ohm ...
thanx again

 

[bassrique]

The following may help some understand, or it may confuse. It's from the Carvin BX 600/1200 manual. Unlike most solid sate amps, these go down to 2 ohms, and therefore may help illustrate how the cab/ohms thing works.

SPEAKER COMBINATIONS/OHMS:
NOTE: BX1200

Two 8 ohms speakers = 4 ohms (OK) (OK for BRIDGE ONLY
output)

Four 8 ohms cabinets = 2 ohms (OK) (not for BX1200 BRIDGE)

Three 8 ohms speakers = 2.66 ohms (OK) (not for BX1200 BRIDGE)

Two 4 ohms speakers = 2 ohms (OK) (not for BX1200 BRIDGE)

One 8 & one 4 ohm cabinet = 2.66 ohms (OK) (not for BX1200 BRIDGE)

Two 8 & one 4 ohms speakers = 2 ohms (OK) (not for BX1200 BRIDGE)

One 2.66 & one 8 ohms speakers = 2 ohms (OK) (not for BX1200 BRIDGE)

Two 2 ohms speakers = 1 ohm (no)

Three 4 ohms speakers = 1.33 ohms (no)

Two 4 & one 8ohm speakers = 1.6 ohms (no)

More for those that may not get "bridged" or "biamp":

X-OVER (bi-amping) and BRIDGE modes on the BX1200:

The BX1200 is capable of three different power amp modes, each with different advantages:

1. DUAL MONO mode (standard)
Both the X-OVER and AMP BRIDGE switches are set to “off”. Each power amp receives the same mono
signal (unless effects are used in the AMP INSERTS). Speakers can be connected to a single or both
SPK1 and SPK2 output jacks. The balance of volume between the two speaker outputs can be set by the
“1 LO” and “2 HI” POWER AMP controls. This mode can useful when using two different speaker cabinets
(such as a 4x10” and 2x10&#8221 that have unequal output levels or when using cabinets with low wattage
ratings.


2. X-OVER mode (bi-amping)
The X-OVER switch is “ON” and AMP BRIDGE switch is “off”. Power amp 1 (LO freq) handles frequencies
below the CROSSOVER FREQ setting. Power amp 2 (HI freq) handles frequencies above the CROSSOVER
FREQ setting. Subwoofers such as 15” or 18” speakers should be plugged into the “SPK 1” jack. Full
range (or high frequency) enclosures should be plugged into the “SPK 2” jack. The balance of volume
between the two speakers is set by the “1 LO” and “2 HI” POWER AMP controls. The X-OVER mode takes
full advantage of the frequency response of these two different types of speakers.


3. BRIDGE mode (mono, full power into one speaker load)
The AMP BRIDGE switch is “ON” (X-OVER settings are disabled). Plug speakers into the BRIDGE ONLY
jack. DO NOT use SPK 1 or SPK 2 jacks in the BRIDGE mode. This mode is used to get the most power
into one speaker enclosure, or several identical enclosures. Be sure your speaker(s) can handle 1200watts
for 4ohm or 800watts for 8ohm enclosures. If two identical speaker enclosures are used each one will
receive 1/2 the wattage. When using speakers of unequal impedance make sure they can handle the full
wattage.

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