Amp trouble/ am I wrong?

[xgsjx]

I never said that either Chris. Yes, it's safe to run an amp at 4Ω (or in your case, 2Ω). But the higher the resistance you put on it, the more current is drawn, therefore the hotter the components get. It's really that simple.
The amp should be built to withstand the extra load, but if you don't need to put the extra strain on the amp, why would you want to?

Your car's engine is designed to run up to the red line without any damage & racing cars run regularly to that & get regular services, whereas with my car, even though it's safe to do so, I don't run my car to the red line all the time as it means I'll need more servicing to keep it in good nick.

[Prosebass]

An amplifier will output a maximum voltage into a cab(s) of a given resistance.

For example my Peavey Tour 450 will deliver a maximum of 42.4v RMS (with good quality Class II wiring)
If you do the maths 42.4 x 42.4 = 1797.76
Divide this by 4 (ohms) = 449.44 (watts)
Divide this by 8 (ohms) = 224.72 (watts)

Power input into the amp is 600 watts so its efficiency (output/input) = 75% at 4ohms
An amp is designed to operate at its maximum output without damaging the components.
However any electrical component has a given life span derived from a complex formula used in the design stages as part of a FMECA (failure, mode, effect & criticality, analysis)
This will formulate the design parameters of the amp and lead to a MTBF (mean time between failure)
This is why cheap components in cheap amps fail sooner than quality components in quality amps for a given use. You really do get what you pay for.

An amp will have a given lifetime running at full power, running at lower power it will last longer, so yes the analogy with a cars engine revs is correct.

Speaker efficiency is much more complex and I would suggest reading here [url="http://www.sengpielaudio.com/calculator-efficiency.htm"]http://www.sengpiela...-efficiency.htm[/url]

To give a quick example remembering (+/- 10dB = double/half) loudness.
My Peavey 450 running (224.72 watts) into a single Genz Benz Contour 210 cab (8 ohms / 97dB) will produce a SPL (sound pressure level) of 120.52dB at 1 meter.
Using two cabs with the equivalent (8ohms) load will make no difference to the actual SPL
Two of these 8ohm cabs in parallel (4ohms / 97dB) makes only a small difference even though the wattage from the amp is doubled to 449.44watts.This gives an SPL of 123.53dB
Using the same Peavey 450 with a Barefaced Super 15 (4ohms / 103dB) will produce a SPL of 129.53dB so getting towards double the volume from the same amp.

This demonstrates why it is important to check the efficiency of a cab and not just what power it will handle. Its power handling taken alone has no bearing on loudness.
Distance from the audience also has a huge bearing on loudness (SPL) and a good rule of thumb is 3-5 meters will half your loudness (SPL)

Edited March 6, 2014 by Prosebass

[Prosebass]

[quote name='xgsjx' timestamp='1394100466' post='2387851']
I never said that either Chris. Yes, it's safe to run an amp at 4Ω (or in your case, 2Ω). But the higher the resistance you put on it, the more current is drawn, therefore the hotter the components get. It's really that simple.
[/quote]

Sorry to be a pedant but the lower the resistance = more current drawn

[xgsjx]

[quote name='Prosebass' timestamp='1394102030' post='2387885']
Sorry to be a pedant but the lower the resistance = more current drawn
[/quote]



I did mean that, but was trying to word it to make it easier to understand (which isn't a good thing, as it then sounds backwards).

Edited March 6, 2014 by xgsjx

[0175westwood29]

[quote name='xgsjx' timestamp='1394100466' post='2387851']
I never said that either Chris. Yes, it's safe to run an amp at 4Ω (or in your case, 2Ω). But the higher the resistance you put on it, the more current is drawn, therefore the hotter the components get. It's really that simple.
The amp should be built to withstand the extra load, but if you don't need to put the extra strain on the amp, why would you want to?

Your car's engine is designed to run up to the red line without any damage & racing cars run regularly to that & get regular services, whereas with my car, even though it's safe to do so, I don't run my car to the red line all the time as it means I'll need more servicing to keep it in good nick.
[/quote]

im afraid your not making any sense!

your just relaying info thats wrong, yes using the amp at 4 ohms will mean it runs hotter but its been designed to run at 4 ohms. so there wnt be any shortening of the amps life. and saying this will worry people.

andy

[Prosebass]

[quote name='0175westwood29' timestamp='1394130854' post='2388315']
im afraid your not making any sense!

your just relaying info thats wrong, yes using the amp at 4 ohms will mean it runs hotter but its been designed to run at 4 ohms. so there wnt be any shortening of the amps life. and saying this will worry people.

andy
[/quote]

Running an amp at its maximum will shorten its life when compared to running it well within its capabilities. This is due to electrical stress on the components.

To quote my previous reply

[quote]An amp is designed to operate at its maximum output without damaging the components.
However any electrical component has a given life span derived from a complex formula used in the design stages as part of a FMECA (failure, mode, effect & criticality, analysis)
This will formulate the design parameters of the amp and lead to a MTBF (mean time between failure)
This is why cheap components in cheap amps fail sooner than quality components in quality amps for a given use. You really do get what you pay for.[/quote]

[0175westwood29]

[quote name='Prosebass' timestamp='1394131670' post='2388320']
Running an amp at its maximum will shorten its life when compared to running it well within its capabilities. This is due to electrical stress on the components.

To quote my previous reply
[/quote]

yes maximum volume! not loading im sorry but i cant agree with this, its designed to be run at 4ohms why would anyone make 4 ohm cabs if they new it would damage there amps

[Prosebass]

[quote name='0175westwood29' timestamp='1394133514' post='2388350']
yes maximum volume! not loading im sorry but i cant agree with this, its designed to be run at 4ohms why would anyone make 4 ohm cabs if they new it would damage there amps
[/quote]

I think the thread is confusing 2 separate issues.
If an amp is designed to run down to a certain resistance (load) and the cab / cabs are matched to that then no, it should not damage the amp.
However, if you also run the amp at maximum output (turned up full) all the time then said amp will not last as long as an equivalent amp run at a lower output (turned down) as there is less amperage flowing through the amplifier.
This is in an ideal world and other factors such as transformer rating can effect the loading and 4ohm speakers with a cheap amp can appear as a 2ohm load under certain conditions and hence the amp goes 'pop'
The relationship between amp and speakers is not as straightforward as it appears [url="http://www.gcaudio.com/resources/howtos/spkramp.html"]http://www.gcaudio.c...os/spkramp.html[/url]
Unfortunately you will never get an amplifier manufacturer to divulge failure figures, but I am sure quality amps will run at maximum for years.
Looking at amp reviews I do not think the same can be said for budget models.

No speaker cab will (should not) damage an amp provided its rating in ohms is no less than that recommended for the amp.
But electrical parts do wear out, just the same as mechanical parts and the more stress you place on them the lower their lifespan.

Hope this clears it up

Edited March 6, 2014 by Prosebass

[0175westwood29]

[quote name='Prosebass' timestamp='1394134514' post='2388369']
I think the thread is confusing 2 separate issues.
If an amp is designed to run down to a certain resistance (load) and the cab / cabs are matched to that then no, it should not damage the amp.
However, if you also run the amp at maximum output (turned up full) all the time then said amp will not last as long as an equivalent amp run at a lower output (turned down) as there is less amperage flowing through the amplifier.
This is in an ideal world and other factors such as transformer rating can effect the loading and 4ohm speakers with a cheap amp can appear as a 2ohm load under certain conditions and hence the amp goes 'pop'
The relationship between amp and speakers is not as straightforward as it appears [url="http://www.gcaudio.com/resources/howtos/spkramp.html"]http://www.gcaudio.c...os/spkramp.html[/url]
Unfortunately you will never get an amplifier manufacturer to divulge failure figures, but I am sure quality amps will run at maximum for years.
Looking at amp reviews I do not think the same can be said for budget models.

No speaker cab will (should not) damage an amp provided its rating in ohms is no less than that recommended for the amp.
But electrical parts do wear out, just the same as mechanical parts and the more stress you place on them the lower their lifespan.

Hope this clears it up
[/quote]

never had a problem with if you run your amp at full volume and gain it will die pretty quick! but xgsix said was that this strain could also be caused by running your amp at 4 ohms or whatever your lowest impedance is.

[Guest bassman7755]

[quote name='0175westwood29' timestamp='1394130854' post='2388315']
im afraid your not making any sense!

your just relaying info thats wrong, yes using the amp at 4 ohms will mean it runs hotter but its been designed to run at 4 ohms. so there wnt be any shortening of the amps life. and saying this will worry people.

andy
[/quote]

This is essentially true and people should not get paranoid about amps "wearing out" when used as designed. PA amps for example generally get much more abuse over much longer periods of time than bass amps and bass amps benefit from the same advances in reliability that have been made over the years. Yes, technically you might marginally reduce the MTBF on some components by running a higher load but in the vast majority of cases you will only ever experience problems if some component was a bit dodgy in the first place.

Its also worth adding to mix that in general the electronic components of a amp (or indeed most modern electronic devices) are actually the most reliable part - switches/knobs/sockets/fans etc or anything else that physically moves are much more likely to be the things that fail.

So my honest is advice is just use your amp as it was designed in what ever way sounds best and stop worrying about overworking it when used with speaker loads it was designed and rigorously tested to cope with.

Edited March 6, 2014 by bassman7755

[xgsjx]

[quote name='0175westwood29' timestamp='1394137800' post='2388433']
never had a problem with if you run your amp at full volume and gain it will die pretty quick! but xgsix said was that this strain could also be caused by running your amp at 4 ohms or whatever your lowest impedance is.
[/quote]

So are you're saying that running an amp at gigging volume into its minimum load isn't affecting the amps components?

[Guest bassman7755]

[quote name='xgsjx' timestamp='1394151735' post='2388619']
So are you're saying that running an amp at gigging volume into its minimum load isn't affecting the amps components?
[/quote]

Its doing what it was designed to do and the vast majority of people using amps in this way will get a lifetime of use out of them.

[xgsjx]

[quote name='bassman7755' timestamp='1394185279' post='2388776']
Its doing what it was designed to do and the vast majority of people using amps in this way will get a lifetime of use out of them.
[/quote]

I never said that it wasn't. I said "why use a single 4Ω cab if there's an identical 8Ω cab as you're not going to gain anything other than putting extra load on the components".
It's really that simple. I don't know how you're managing to find it so difficult.

You like sports cars. You drive it like an every day car & you only need to service it once a year. You start racing it, you put more strain on the components (they're working harder). They are designed to deal with it but you might find that it needs more servicing.

If you're using a good quality amp, then you might find you rarely need to service it, but it will need a service sooner if it's been running at 4Ω rather than 8Ω.
If you're using a cheaper amp, then the parts are less likely to handle the increased heat.

[Guest bassman7755]

[quote name='xgsjx' timestamp='1394193537' post='2388968']
I said "why use a single 4Ω cab if there's an identical 8Ω cab as you're not going to gain anything other than putting extra load on the components".
It's really that simple. I don't know how you're managing to find it so difficult.
[/quote]

Yes but you are gaining something - the extra power headroom. Yes it might only be a couple of DB in practice but why throw it away for some unquantifiable supposed reliability gain. If were going to swap car analogies then its like buying a 4 seater car but never carrying more than 2 passengers on the basis that it will wear out less quickly - in the vast majority of cases it wont make any measurable difference over the expected time span of use.

[xgsjx]

[quote name='bassman7755' timestamp='1394195973' post='2389004']
Yes but you are gaining something - the extra power headroom. Yes it might only be a couple of DB in practice but why throw it away for some unquantifiable supposed reliability gain. If were going to swap car analogies then its like buying a 4 seater car but never carrying more than 2 passengers on the basis that it will wear out less quickly - in the vast majority of cases it wont make any measurable difference over the expected time span of use.
[/quote]
Bill worded that the opposite way round from you. his words were "[color=#282828][font=helvetica, arial, sans-serif]Voltage sensitivity is increased by 3dB, but that's at the cost of doubled current draw"[/font][/color]
[font="helvetica, arial, sans-serif"][color="#282828"]​So you're willing to have twice as much heat going through your amp for 3db if you're using a [/color][/font][color=#282828][font=helvetica, arial, sans-serif]single cab[/font][/color][color=#282828][font=helvetica, arial, sans-serif]? It's your choice, I'm only giving information that I've [/font][/color][font="helvetica, arial, sans-serif"][color="#282828"]acquired.[/color][/font]
[color=#282828][font=helvetica, arial, sans-serif]The "extra headroom" also increases the chances of clipping. You've got twice as much current going through things.[/font][/color]

[0175westwood29]

[quote name='xgsjx' timestamp='1394202615' post='2389113']
Bill worded that the opposite way round from you. his words were "[color=#282828][font=helvetica, arial, sans-serif]Voltage sensitivity is increased by 3dB, but that's at the cost of doubled current draw"[/font][/color]
[font=helvetica, arial, sans-serif][color=#282828]​So you're willing to have twice as much heat going through your amp for 3db if you're using a [/color][/font][color=#282828][font=helvetica, arial, sans-serif]single cab[/font][/color][color=#282828][font=helvetica, arial, sans-serif]? It's your choice, I'm only giving information that I've [/font][/color][font=helvetica, arial, sans-serif][color=#282828]acquired.[/color][/font]
[color=#282828][font=helvetica, arial, sans-serif]The "extra headroom" also increases the chances of clipping. You've got twice as much current going through things.[/font][/color]
[/quote]

the point you are making is rubbish! any amp is tested and will be fine! the extra heat your talking about is designed in to the amp and wint hurt anything in it, im mean if your that worried about the components im surprised you ever turn your bloody amp on!

and the extra headroom increases the chance of clipping?!

[Iheartreverb]

This has moved into things I really don't understand.
It just seems odd that heads are sold on wattage that can't achieved with 90% of the cabs available.

It seems my assumption of need a new amp are correct and for the people who confirmed this, thanks.

Probably going to go with a 4x10 as won't need to upgrade from that for a while, if at all.

As for a head, for £250 I could take my pick

[xgsjx]

[quote name='0175westwood29' timestamp='1394216469' post='2389298']
the point you are making is rubbish! any amp is tested and will be fine! the extra heat your talking about is designed in to the amp and wint hurt anything in it, im mean if your that worried about the components im surprised you ever turn your bloody amp on!

and the extra headroom increases the chance of clipping?!
[/quote]

How do you work it out to be rubbish?
I've tried to explain it simply, but I think you're either missing what I'm saying completely or think I'm meaning it'll kill the amp (which I'm not).

I'm not saying don't run at 4 ohms. I run mine at 4 ohms when needed at a gig.

Could you explain how it reduces the potential for clipping?
I'm not asking to make an argument, I like to find out a much about gear as I can & how things work, which is why I spend time reading on here, the Barefaced site, BFM's forum & anywhere else that discusses sound systems. I like to get the best from what I have.

[0175westwood29]

[quote name='xgsjx' timestamp='1394231805' post='2389476']
How do you work it out to be rubbish?
I've tried to explain it simply, but I think you're either missing what I'm saying completely or think I'm meaning it'll kill the amp (which I'm not).

I'm not saying don't run at 4 ohms. I run mine at 4 ohms when needed at a gig.

Could you explain how it reduces the potential for clipping?
I'm not asking to make an argument, I like to find out a much about gear as I can & how things work, which is why I spend time reading on here, the Barefaced site, BFM's forum & anywhere else that discusses sound systems. I like to get the best from what I have.
[/quote]

its rubbish as by meaning that your stating a point that doesnt need to be said!

your saying it will increase the heat, which yeh it will but turning the bass up will increase the bass neither will break the amp, and if it wnt break or hurt the amp then why put it on a forum that has alot of beginners who may panic thinking they are hurting there amp.

andy

[xgsjx]

[quote name='0175westwood29' timestamp='1394233788' post='2389497']
its rubbish as by meaning that your stating a point that doesnt need to be said!

your saying it will increase the heat, which yeh it will but turning the bass up will increase the bass neither will break the amp, and if it wnt break or hurt the amp then why put it on a forum that has alot of beginners who may panic thinking they are hurting there amp.

andy
[/quote]
Don't you think that letting people know that "running a single 4Ω cab to get the best from the amp" is really telling them rubbish though?

[Prosebass]

[quote name='0175westwood29' timestamp='1394216469' post='2389298']
the point you are making is rubbish! any amp is tested and will be fine! the extra heat your talking about is designed in to the amp and wint hurt anything in it, im mean if your that worried about the components im surprised you ever turn your bloody amp on!
[/quote]

In which case my position as a materials quality assurance specialist is bogus, and everything manufacturers produce is just hunky dory.
Thanks for that, I have now stopped worrying about anything ever failing.

[0175westwood29]

[quote name='xgsjx' timestamp='1394234464' post='2389505']

Don't you think that letting people know that "running a single 4Ω cab to get the best from the amp" is really telling them rubbish though?
[/quote]

But again this isnt what you said, most ppl will run a 8 ohm 410/115 or use two cabs. If ppl want to use a 4 ohm 410 they should be able to without ppl like you telling them they are putting strain on there amp.

[0175westwood29]

[quote name='Prosebass' timestamp='1394236401' post='2389536']


In which case my position as a materials quality assurance specialist is bogus, and everything manufacturers produce is just hunky dory.
Thanks for that, I have now stopped worrying about anything ever failing.
[/quote]

If your using the head correctly it shouldnt fail, yes sometimes s@&t happens but just saying plugging into a 4 ohm will shorten the life of the amp ( this is what he was saying) is a point that doesnt need to be made

[xgsjx]

[quote name='0175westwood29' timestamp='1394264606' post='2389617']
But again this isnt what you said, most ppl will run a 8 ohm 410/115 or use two cabs. If ppl want to use a 4 ohm 410 they should be able to without ppl like you telling them they are putting strain on there amp.
[/quote]
I know never said running a single 4 ohm cab is rubbish, I just advised that it puts an extra strain on the amp.
You do realise that most bass amps are effectively 2 amps? There's the pre amp & the power amp. If you've set the volume on your bass quite low & set the input gain to just under clipping, then turning the instrument up would cause the pre amp to clip, which could damage the cab's drivers.
Increased current draw increases the chance of the power amp clipping.
I never said it would cause the amp to fail (though it could, especially if the amp is 2nd hand), but more likely to need serviced sooner.
If someone is given advice to get a single 4 ohm cab, don't you think it's wise to know the pros and cons?
It's like telling someone with a car that it's good to run upto the red line before changing gear as you'll get there quicker.

[Musky]

[quote name='0175westwood29' timestamp='1394265038' post='2389621']
If your using the head correctly it shouldnt fail, yes sometimes s@&t happens but just saying plugging into a 4 ohm will shorten the life of the amp ( this is what he was saying) is a point that doesnt need to be made
[/quote]
Heat will shorten the life of an amplifier - this isn't scaremongering or something that isn't of any concern to the users of electrical equipment. It's often quoted in electrical engineering circles that a 10C increase in operating temperature will result in a doubling of the failure rate.

However a few things need to be borne in mind. Simply running an amp at 4 ohms will not necessarily result in an increase in operating temperature - it will depend on how the amp is used. And of course amps have cooling features built in, some better than others that might go some way to overcoming heat build up. The failure rate of an amp may double with increased temperature, but if you have a failure rate of 0.1% to start with a 0.2% rate may be something you could live with. On the other hand any owner of an Ashdown Superfly will be able to describe how heat build up in an amp affects reliability.

So it's just not true that this is something that affects nobody and is of no concern to a gigging player: it's more a case that there are a lot of variables going on, including expectations of a 'reasonable lifetime'.