What is the minimum power needed for a Pub Band?

[Phil Starr]

On 14/02/2024 at 14:12, thebrig said:

Following on from my previous post where I asked for some advice on a PA for a pub band.

 

My question now is:

How much power (rms) per side would be needed to play in small to large pubs, we would like to have a bit of headroom so that we are not pushing the PA to it's limit when playing the larger pubs?

 

Only the vocals and kick drum will be going through the PA.

 

If we ever get to play at a large venue or festival, then we would assume that a PA and sound engineer would be provided.

I've been wondering about this question again, could we have given a clearer answer? It's tough for someone with no technical background to follow some of the more technical answers but that is what anyone asking willl be offered.It's equally tough for someone who has a technical background to give a partial answer, something they know is almost true but leaves out some important detail which could end up with someones hard earned money spent on something that won't do the job.

 

There was a one line answer available here all along: buy a decent quality 12" system with 300W a side going to each speaker. My guess it that most of us who are regularly gigging either own or have successfully used such a system for many gigs. I see a lot of covers bands, I rarely see anyone using anything else in pubs. Two 12's on poles are on display at at least 80% of pub gigs. Why did we make it so complex

 

The analogy here might be asking three different 'experts' about how the heart works. A primary school teacher will give a different answer to an eight year old from the answer a secondary science teacher will give an eighteen year old Biology student different again. A doctor has a different problem when they talk about the heart it has consequencies. If they aren't clear somone might die, if they fail to get the message across, then catastrophe. If they over simplify and miss out what later turns out to be an important detail they can end up in court. I wonder if we aren't all pretending to be thoracic surgeons here carefully picking words and refining arguments when the real doctor inside them wants to just scream; "lose some effing weight, stop eating crap, get some exercise and enjoy the rest of your life" as they propose surgery or prescribe pills with side effects that will make their patients lives miserable.

 

I wonder why we didn't say; "get a couple of decent 12's on poles and get on and enjoy playing"?

 

 

Edited April 15 by Phil Starr

[b7l4s]

Old thread resurrection - sorry! But when I read this I wanted to comment...

 

On 14/02/2024 at 21:15, warwickhunt said:

Added to which I know PA guys who could make a band sound great with a couple of hundred watts of amps/cabs whereas another bloke could cripple a band with 2k watts of PA.  

 

My band have a mixture of old and new gear, but essentially we use a basic mixer, active 12's on poles for FOH and a couple of floor wedges for monitoring. The rehearsal rooms we use have a nice PA available, and it's easy to sound good in there, but every gig was a frustrating quest to sound as good as during practice. We automatically assumed that our cobbled together PA was just a bit crap and were debating spending out on a shiny new one, but one evening we were sharing with another band and they made our PA sound amazing... their singer knew what he was doing and in a five minute sound check had it nailed.

 

We made the effort after that - read the manual(!), did a bit of YouTube research and spent some rehearsal time just working out how to get the sound in our heads out of our own equipment. Gig life is much better now and we can cope with most of the variables that real venues throw at you. So no answer to the vexed question of power, but a long winded way of agreeing that what you hear is not just about the PA... you also need to know how to use it effectively.

[chris_b]

How loud is the band?

[Stealth]

A word in praise of RCF ART range we use the ART 312a mk11 great clarity not all Mankiewicz SRM mid push and decent SPL. 50 plus gigs no dramas 

[Beedster]

On 26/07/2024 at 12:52, b7l4s said:

Old thread resurrection - sorry! But when I read this I wanted to comment...

 

 

My band have a mixture of old and new gear, but essentially we use a basic mixer, active 12's on poles for FOH and a couple of floor wedges for monitoring. The rehearsal rooms we use have a nice PA available, and it's easy to sound good in there, but every gig was a frustrating quest to sound as good as during practice. We automatically assumed that our cobbled together PA was just a bit crap and were debating spending out on a shiny new one, but one evening we were sharing with another band and they made our PA sound amazing... their singer knew what he was doing and in a five minute sound check had it nailed.

 

We made the effort after that - read the manual(!), did a bit of YouTube research and spent some rehearsal time just working out how to get the sound in our heads out of our own equipment. Gig life is much better now and we can cope with most of the variables that real venues throw at you. So no answer to the vexed question of power, but a long winded way of agreeing that what you hear is not just about the PA... you also need to know how to use it effectively.

 

Useful post. Given that you can take a well mixed/mastered/produced album, play it through a top-end audio system in a flattering acoustic environment, and by messing with the controls make it sound bloody awful, the harm that can be done to the sound of an amateur/semi-pro band playing through a low/mid-price PA in a challenging acoustic environment is obvious. As is always the case, half the battle is having better gear, it's simply knowing how to use the gear you've got 👍 

[Chienmortbb]

On 26/07/2024 at 12:52, b7l4s said:

you also need to know how to use it effectively.

Was it Bessie Smith or someone else that sang “It ain’t the meat it’s the motion”?

[TimR]

The real answer to this is found in the answer to the following questions:

Can your drummer play at the appropriate volume?

Can your guitarist play his amp with the "Stun" setting disengaged?

Do you have effective monitoring for the singer?

 

If the monitoring for the singer is bad and they can't hear themselves and/or have to turn the monitor up to feedback levels due to the aforementioned drummer and guitarist, then it doesn't matter how much power you have - you won't have anything coherent anywhere in the room.

 

[keeponehandloose]

Broad rule of thumb I was told many years ago. 5 watts per head indoors, 15 watts per head outdoors, as a minimum.

 

[Stealth]

Errr Watts aren’t that important and Manufacturers use many methods to measure sell stuff. Also totally depends on what you’re playing. Decibels are slightly more representative.  It’s a bit of a suck it and see really. Sound on Sound magazine is a decent online resource 

[Stealth]

PS dunno where you are but you’re welcome to try my RCFs if you want too? 

[Stub Mandrel]

On 19/03/2024 at 19:18, Chienmortbb said:

I once met a girl , easy it is not that sort of forum. Her father was head flautist for the London Philharmonic. 
 

We were invited back to her parents house to play some  records(vinyl). The HiFi included  a pair of Lowther drivers set in concrete on the floor with huge horns going up and over, finally pointed into the centre of the room. The sound from a tiny amplifier was immense BUT not many spouses would accept either the cost, building work and visual intrusion in the lounge. 

 

Now apart from reminiscing,  as with Bill’s post above, illustrates that you cannot judge a system either by the power or the look of a system.
 

 

 

 

I recall reading a book, already old in the 1980s, that claimed a blind test comparing a recording to an orchestra (behind a thin curtain) in a concert hall with an audience found around 10 watts was equivalent to the full orchestra, but IIRC that used huge horns.

 

Another book I found recently has some interesting stuff.

 

 

A lot has changed. Labyrinthine bass reflex arrangements instead of simple ports, for example. But this is a very relevant page:

 

I would be interested to know how 'acoustic watts' compare to a dB/m reference, but also that he points out that it may take between 2W and 500W of electrical power to generate 1W of acoustic power. Even in 1966 it was well known that speaker efficiency is at least as important as amplifier power.

 

 

[Stub Mandrel]

This may (I hope) be helpful.

 

Each line represents a particular speaker efficiency in dB/W. 90 to 103 is a pretty representative range for PA/bass cabs. 'HiFi' speakers can be well below 90dB/W.

Left to right is increasing amplifier power in watts and vertical is SPL at 10 metres for a speaker in free air (if it was against a wall the sound would be louder, as it would if sound is confined in a room, but the relative differences in SPL still stand).

To properly understand this, 10bB in SPL is a doubling in loudness and is what you get by increasing amp power by ten times (e.g. from 30W to 300W), or increasing speaker efficiency by 10dB/W (e.g. from 93dB/W to 103dB/W).

So a 60W amp through a 103dB/W speaker is as loud as a 1000W amp through a 90 dB/W speaker.

 

These are realistic figures for amps and speakers  (horns are very efficient, if those huge concrete horns were on the chart they'd be giving 110dB/W or higher... that's why the old record players could make a listenable volume just from the movement of the needle, a fraction of a watt of power).
 

 

 

In the real world things are complicated by what we play through the speakers. The perceived loudness in 'phons' at our lovely bass frequencies requires lots more SPL than those just a bit higher. Very roughly, us bass players need about 10-15dB SPL more than guitar players to seem as loud, which is why our amps have to be several times more powerful AND use more efficient speakers:

[Phil Starr]

2 hours ago, Stub Mandrel said:

Another book I found recently has some interesting stuff.

Badmaieff and Davis pub 1966, I've got a copy in front of me, my first speaker book I built a few near copies of the Altec A7 from this and I have a collection of old books from the pre Thiele and Small era. Happy days

[Phil Starr]

14 hours ago, Stub Mandrel said:

 

I would be interested to know how 'acoustic watts' compare to a dB/m reference, but also that he points out that it may take between 2W and 500W of electrical power to generate 1W of acoustic power. Even in 1966 it was well known that speaker efficiency is at least as important as amplifier power.

Here you go

 

[Stub Mandrel]

9 hours ago, Phil Starr said:

Here you go

 

 

Thanks. So a brain melting SPL of 120dB is only one acoustic watt! Our amps are so very inefficient!

[Chienmortbb]

On 05/09/2024 at 20:23, Stub Mandrel said:

 

Thanks. So a brain melting SPL of 120dB is only one acoustic watt! Our amps are so very inefficient!

It does say sound power, without any other info (acoustic watts?) its hard to know what that means although the principle is largely true.

[Chienmortbb]

 A very unscientific accident has made e wonder how true the rule that 10 times the power equals a doubling of volume. I recently fitted an ICEPOwer 50ASX50 module to the modifies After Eight Combo that I described in another thread.

As is my wont, I keep fiddling with things and ended up taking out both the +15 volt power supply and the ICEPower module. So both were replaced and to my surprise the combo was much quieter. Now the sleeping cat usually heads for the cat flap at my first note but no.

 

Then I remembered that the ICEPower module needs a link changing to run BTL giving the full 100 watts into 8 Ohms. With the link as shipped the module only gives 30 watts into 8 Ohms. With the modified module, the room shakes and it certainly feels like more than a doubling of power. Of course no measurements were taken. However  any rule of thumb should be taken as s guide and not an absolute.

[Stub Mandrel]

2 minutes ago, Chienmortbb said:

 A very unscientific accident has made e wonder how true the rule that 10 times the power equals a doubling of volume. I recently fitted an ICEPOwer 50ASX50 module to the modifies After Eight Combo that I described in another thread.

As is my wont, I keep fiddling with things and ended up taking out both the +15 volt power supply and the ICEPower module. So both were replaced and to my surprise the combo was much quieter. Now the sleeping cat usually heads for the cat flap at my first note but no.

 

Then I remembered that the ICEPower module needs a link changing to run BTL giving the full 100 watts into 8 Ohms. With the link as shipped the module only gives 30 watts into 8 Ohms. With the modified module, the room shakes and it certainly feels like more than a doubling of power. Of course no measurements were taken. However  any rule of thumb should be taken as s guide and not an absolute.

 

The perception of volume has a subjective element which means there is no completely 'right' answer. The 10dB SPL = doubling of volume is an approximation, but is quite close for most sounds.

 

I remember my shock in the 1980s when I connected my Marshall 1x12 cab to my tiny Maplin one-watt PP3 powered 'micro combo'. It sounded huge, and I repeated the experiment as a demonstration for people many times.

 

Percieved volume is measured in 'phons'.

 

"A phon is a unit of measurement for the loudness of a sound or noise. Phons are based on equal loudness contours and the decibel scale of sound intensity. The threshold of hearing at 1,000 Hz is 0 phons, or 0 decibels. "

 

 

As you can see, perceived loudness is heavily dependent on frequency. With 200hz sounding loudest at just about all powers.

 

These curves can only be derived by subjective listening tests, but they show how the amount of power needed for a volume change is very different depending on context (frequency and starting volume).

 

Absolute volume is measured in the not universally accepted unit of 'sones'. To quote Wikipedia:

 

"a loudness of 1 sone is equivalent to 40 phons (a 1 kHz tone at 40 dB SPL).[1] The phons scale aligns with dB, not with loudness, so the sone and phon scales are not proportional. Rather, the loudness in sones is, at least very nearly, a power law function of the signal intensity, with an exponent of 0.3.[2][3] With this exponent, each 10 phon increase (or 10 dB at 1 kHz) produces almost exactly a doubling of the almost exactly a doubling of the loudness in sones.[4]"

 

See also the explanation section here:

https://en.m.wikipedia.org/wiki/Loudness

which isn't very useful...

 

Long and short of it is that it isn't an exact science.  Add in the complexity of headroom, room acoustics and other aspects of our amps and where/how we play them the only way to make truly meaningful comparison is to take readings with test signals and an accurate sound meter in proper conditions while accurately measuring amplifier output.

[Stealth]

43watts 

derived from the meaning of life which is 42 plus one one so it’s one louder !

 

 

Edited September 9 by Stealth

[PaulWarning]

36 minutes ago, Stealth said:

43watts 

derived from the meaning of life which is 42 plus one one so it’s one louder !

 

 

I've done that with my Trace Elliot, it's loads louder now 😂

[SimonK]

12 minutes ago, PaulWarning said:

I've done that with my Trace Elliot, it's loads louder now 😂

 

Oh my - and Trace Elliot Watts are louder than anyone elses (I think because they historically quoted RMS Watts rather than peak)! Certainly I've never found a 150 Watt Trace Elliot (GP7) under powered in a llive situation (using either 4x10 or 1x15 cabs).

 

As with the theme of the thread, knowing what you are doing with the PA is probably most important. I've had seriously underpowered PA's before which I just ran vocals through, letting the band use their amps. Knowing how to use a compressor well can also help with peceived volume.

[PaulWarning]

7 minutes ago, SimonK said:

. Knowing how to use a compressor well can also help with peceived volume.

we've got a built in compressor on our Yamaha EMX 512, whenever I try and use it I get feedback issues, but then I'm not sure what I'm doing, it is loud enough for vocals and bass drum anyway

[Chienmortbb]

1 hour ago, Stub Mandrel said:

 

The perception of volume has a subjective element which means there is no completely 'right' answer. The 10dB SPL = doubling of volume is an approximation, but is quite close for most sounds.

 

 

This was really my point. The same room, same speaker and cabinet. The difference was a lower powered amp and a few months in between hearing sessions. It is well know that the ear/brain has no memory for sound or at least comparing sounds but this was very noticeable. In future is I ever quote the 10 times the power for the doubling of volume, I will qualify it in some way.

[SimonK]

49 minutes ago, PaulWarning said:

we've got a built in compressor on our Yamaha EMX 512, whenever I try and use it I get feedback issues, but then I'm not sure what I'm doing, it is loud enough for vocals and bass drum anyway

...I should probably add you need to use a compressor alongside EQ. Often people turn up because they can't distinguish the vocals from the mix, whereas if you boost around 4kHz and also slightly over-compress the vocals to bring the quieter bits up you can get a lot more clarity with no more volume. Then you can get away with a much less powerful PA, although I do agree with not going smaller than 12 inch drivers. The other counter-intuitive thing to try is sound damping especially behind the musicians. A curtain behind the stage stops reflections and improves clarity.

Edited September 9 by SimonK

[Chienmortbb]

On 09/09/2024 at 11:53, SimonK said:

I do agree with not going smaller than 12 inch drivers.

If you are using the PA for vocals alone, 8" drivers should be fine, with the usual caveat that you use a respected make. I would take a pair or really good 8s over some cheapo 15/12s any day.

 

It is interesting that many manufacturer's ranges now go 15/12/8 with 10s being a rarity.  Of course you can add a sub or two later if needed.