4 Ohm Vs 8 Ohm

[xgsjx]

Someone said that their bass amp sounds better through a single 4 ohm 4x10 than it does through an 8 ohm of the same cab.

Does running an amp at it's maximum ohms affect the sound that it produces? I've never noticed any difference when I've tried it.

[leroydiamond]

Halving the impedence from 8 to 4ohms results in increased output from the amp, assuming the amp is compatible with a 4 or 8 ohm load. E.g. my Markbass amp feeds 300 watts at 8 ohms and 500 at 4 ohms.

Edited November 6, 2013 by leroydiamond

[barkin]

Louder is better

[badboy1984]

All depend really. On my LB30 head it make no different running a single 4 ohm or 8ohm cab. Either cabs my head will pump out full power.

[barkin]

[quote name='leroydiamond' timestamp='1383746212' post='2268454']
Doubling the impedence results in increased output from the amp...
[/quote]
ITYM halving...

[leroydiamond]

[quote name='barkin' timestamp='1383746698' post='2268466']
ITYM halving...
[/quote]

i stand to be corrected and have edited accordingly

[xgsjx]

That's not what I meant. I know that an amp that runs 500w at 4 ohm is about 350w at 8 ohm. The difference in volume is near enough sod all.

Say I had a 2x10 8 ohm cab & an identical 2x10 4 ohm cab. If I used one at a time, would it affect the power stage enough to make the amp sound different?

[badboy1984]

Volume wise i can't see a huge different but tone wise i would say yes, but i could be wrong. So please correct me if i'm totally wrong.

Let says a amp is 500w at 4ohm and 350w at 8ohm.

You get more clean headroom when using a 4ohm cab because you pumping out more power.

[Tdw]

I dont know but i have an eden metro combo which can work at two ohms, however eden recommend its used at four ohms because it will sound better, so maybe some amps sound better at a specific impedance?

[chris_b]

I've seen reviews where an amp is reported to have produced a slightly fuller tone into 4 ohms, but if you can hear the difference in a noisy band or when the drummer gets going I'd be surprised.

For me, the benefit of 8 ohms is with smaller cabs, when you can either use one cab or add another and get a better tone from having more cone area. You [i]will[/i] hear that improvement in a band mix when the racket starts.

If you're talking about larger cabs, 410's etc, I'd always go for 4 ohm because I wouldn't be adding a second cab and you might as well have full power on tap, if you need it.

[Guest bassman7755]

[quote name='badboy1984' timestamp='1383747778' post='2268491']
You get more clean headroom when using a 4ohm cab because you pumping out more power.
[/quote]

More specifically you get greater headroom because the amp can use a lower voltage to deliver the same power so its less likely to exceed its voltage limit (and thus clip the signal).

[razze06]

From an electrical point of view, a lower load impedance (4 ohm) means that the speaker will draw more current from the amp than a bigger load (8 ohm). Not all amp power supply work the same at different output levels, just like car engines have ranges in which they work better. A small city car may just about reach 100 mph, but a sports car will comfortably cruise at that speed. Now substitute car with amp and speed with output current...

[flyfisher]

If the amp is perfectly linear, i.e. maintains the same frequency response and other characteristics across its entire power range, then I wouldn't expect it to sounds any different through a 4ohm cab or an 8 ohm cab. The same applies to the cab of course.

So, in an ideal world I wouldn't expect any difference.

Meanwhile, back on planet Earth, I'd be less sure of the technical answer but I do know that I don't really care. This is because the only real test of anything so subjective is to try it and decide what you prefer.

The problem with all these sorts of questions is that, in practice, the audible differences are likely to be negligible - if detectable at all - but people seem to like reassurance about what 'should' sound better. Then, primed with what to expect, they try it out and, guess what, configuration X turns out to sound much better than configuration Y, just as everyone said it would.

I've done it myself with various cab configurations: single 210, single 115, dual 210s arranged 2x2, dual 210s arranged 4x1, 210+115 and I couldn't hear any dramatic difference - I just preferred the dual 210s arranged 1x4 because it means I don't have to bend down to adjust my amp and the top speaker was closer to my ears so easier to hear. But what sounds 'best' in a rehearsal room will likely sound completely different in a small, crowded pub with low ceilings.

I reckon we tend to agonise too much about all this stuff . . . but maybe I've just got cloth ears.

[Lozz196]

I think there`s something in that Mike, the search for tone nirvana has become limitless due to what we can read about on-line, seeing reviews/demos etc. Maybe just playing and enjoying would yield better results.

[Guest bassman7755]

[quote name='chris_b' timestamp='1383753867' post='2268622']
I've seen reviews where an amp is reported to have produced a slightly fuller tone into 4 ohms, but if you can hear the difference in a noisy band or when the drummer gets going I'd be surprised.
[/quote]

Thats likely to be because (as I alluded to in my earlier post) its operating at a lower output voltage so is less likely to reach its rail voltage limits especially at lower frequencies were a higher voltage swing is required to produce the same volume.

[flyfisher]

[quote name='bassman7755' timestamp='1383758098' post='2268688']
Thats likely to be because (as I alluded to in my earlier post) its operating at a lower output voltage so is less likely to reach its rail voltage limits especially at lower frequencies were a higher voltage swing is required to produce the same volume.
[/quote]

OTOH, a PSU not capable of supplying the required current/voltage at the amp's highest rated power output is really an issue of poor product design.

[dincz]

In solid state amps with real-world power supplies, the rail voltage sags as you approach clipping - more so with a 4 ohm load than with 8 ohms because more current is being delivered. This can result in a certain amount of compression.

Edited November 6, 2013 by dincz

[flyfisher]

I'm sure that's true in some amps but it's a design issue, not a law of physics.

[Musky]

I seem to remember Bill saying that speaker specs are usually published for the 8 ohm version, but some of the parameters will be different for the 4 ohm version.

I haven't got a clue how much difference that will make in the real world.

[dincz]

[quote name='flyfisher' timestamp='1383759932' post='2268727']
I'm sure that's true in some amps but it's a design issue, not a law of physics.
[/quote]

Unfortunately it is a law of physics - Ohm's law - and that's why an amp's maximum power at clipping with a 4 ohm load is never double what it is at 8 ohms. Until someone develops a power supply with zero impedance, we're stuck with it

[LukeFRC]

I think there's a article on barefaceds website saying why they make 8ohm cabs onthe mobile so can't link to it...

[Bill Fitzmaurice]

[quote name='xgsjx' timestamp='1383745411' post='2268442']
Does running an amp at it's maximum ohms affect the sound that it produces?
[/quote]No. Voltage sensitivity is increased by 3dB, but that's at the cost of doubled current draw. Seldom is maximum output affected, as that's determined by the driver displacement limit, which on average is only half the thermal limit.

[flyfisher]

[quote name='dincz' timestamp='1383761134' post='2268760']
Unfortunately it is a law of physics - Ohm's law - and that's why an amp's maximum power at clipping with a 4 ohm load is never double what it is at 8 ohms. Until someone develops a power supply with zero impedance, we're stuck with it
[/quote]

We may be at crossed purposes. I'm suggesting that if an amp's power output is limited by the PSU capacity then the PSU is not adequately specified. Even a PSU with zero impedance wouldn't prevent signal clipping would it?

[Phil Starr]

There's a few reasons why people might think a 4ohm speaker sounds 'better' but in the end there is probably more myth and magic than hard fact.

1.There is an increase in total power, usually a couple of dB's. This is just noticeable and could be the difference between running into distortion or not. Mainly not though, and the difference in volume is tiny. As Bill has said in most cases the limits are just as likely to be the speakers so the amp power is often not the problem.

2. The drivers aren't the same, to get the different impedance the voice coils and sometimes the magnets are changed. This changes the sound and the speakers parameters. If they are put into the same sized cabs the frequency responses won't be the same, neither will the excursion limits.

3. We instinctively like louder sounds (which is why modern recordings are compressed to hell) If you A/B the 4ohm speaker with the 8 it will be louder, if you don't adjust the volume and sound 'nicer'. Adjust the volumes to be the same and the preference disappears.

4. People aren't very objective, which is why we need double blind tests. If all the experts tell you that (for example) oxygen free copper wire sounds better then it isn't long before everyone hears a difference that can't be measured.

So there may be a grain of truth, 4 and 8 ohm speakers may sound different and 50% of the time you might prefer the 4's but the differences are mainly slight and I doubt anyone would notice if you did the listening test whilst the amp sat next to a drummer, never mind a guitarists half stack. It's not a sensible way to choose a speaker cab.

[xgsjx]

Cheers guys.
I wasn't looking to change to a 4 ohm cab, but curious from someone's comments on another website about how amps are designed to sound better with a 4 ohm load, so where better to ask.