Speakers; making sense of the figures

[stevekane]

Hi, we have a band,,its a Ukulele band and were playing a variety of venues,,not a George Formby song on the menu but a wide mix of stuff from the 50s right through covering most styles. There ae up to 10 of us, inc a bass guitar (with his own cab) and a cahon (which is not spelt correctly Im sure?) 9 mics and 3 of the ukes are plugged in and a couple of wedge monitors. We were running this lot through a little Yamaha Stagepas 400. We recently upgraded to a Studiomaster club16 mixer but were still using the little yamaha set as our Amp and Speakers, so our next move is to buy a couple of active speakers and now Im trying to make sense of the specs.
With a Uke band we dont need thumping bass,,so Im thinking that the Mackie Thump range are probably not for us? But, are certain speakers “modelled” for say Bass or Vocals and how do I know? And now there is loudness, we want some loudness,,SPL as is described in an excellent article on this site, it seems that according to the article a band like ours, playing small to medium venues and sometimes outside needs an SPL of around 125db,,which is Mackie Thump 1000w territory,,but Alto TX750w is just a mild 117db from memory,,,so I checked the spec sheet for our 400w yamaha and its given as SPL125db,,,rock band volume,,can this be right, what am I missing? Any help gratefully received.
Steve.

[The Red Bladder]

Rules to remember -

• +10dB is to double the volume.

• Watt and SPL ratings are largely "Think of a number - now double it!"

• A clear indicator that a brand of amp/speaker/whatever is lying is when they site 'music power' - it can be made to mean anything!

• Volume ain't everything - people have to like what they hear.

• You get what you pay for!

When I was running sound systems, we had to cover all kinds of music and speakers had to be BIG. Today, just two relatively small D&B speakers (or similar quality speakers) will cover anything up to a one thousand audience.

When it comes to PA speakers, you get what you pay for. Cheap speakers will give you a cheap sound (poor transient response, distortion, uneven frequency response, etc.)

[James Perrett]

• Watt and SPL ratings are largely "Think of a number - now double it!"

Pretty much what dB Technologies did with the Opera 215's that I used for a few years. They sounded fine but maybe not quite as loud as expected. It was only when they went wrong and I took a good look at the amp chips that they used that I realised they weren't putting out anything like the power claimed.

[shufflebeat]

About a year ago I did a quick A/B of my Yam dxr12 (+ sub) and my Yam dxr8 (+ sub). The difference was very marked with the 8s having much greater definition and separation in the higher melody instruments and vocals.

From time to time over the years I’ve used 15” speakers, thinking they would be a bigger sound and my mate has some old EV 15s which I was recently persuaded to use at one of his gigs. They were very loud but the inherent compromises meant that for music with detail in the higher end they always struggle to fill a room without sounding too loud.

Moral of story - size and paper numbers don’t tell the whole story.

[Philbo King]

No offense, but if I encountered a ukelele band amplified to 125 dBSPL I would flee the area and never come back.

[shufflebeat]

No offense, but if I encountered a ukelele band amplified to 125 dBSPL I would flee the area and never come back.

It’s the new Death Metal, not for everyone.

[Arpangel]

No offense, but if I encountered a ukelele band amplified to 125 dBSPL I would flee the area and never come back.

It’s the new Death Metal, not for everyone.

Banjo's Of Doom.

[shufflebeat]

No offense, but if I encountered a ukelele band amplified to 125 dBSPL I would flee the area and never come back.

It’s the new Death Metal, not for everyone.

Banjo's Of Doom.

Mmm… that has a ring to it, I may be stealing it.

[Wonks]

Maybe without the apostrophe.

[Drew Stephenson]

Interesting as this detour is, I'm not sure it's helping the OP much.
Personally I'd suggest that SPL is the best figure to look at, but treat it with the above mentioned pinch of salt. Given your use case I'd probably look at either units with a 8" or 10" driver and, depending on budget, start with options from Alto or Yamaha.
It's also worth thinking about the portable line-array units as well, the thin-column-on-a-box units. They'll generally have a lower SPL at a given price point but the way they distribute the sound can compensate for that to an extent.

[Wonks]

What you don’t want to do is have to run the speakers near flat-out to get the volume you need. Speakers with a higher maximum SPL should give you headroom to allow transients through without any distortion, so everything sounds clearer.

PA Speakers normally aren’t voiced for specific applications, and should be nominally flat within their frequency limits, but the way they are made and the components used may colour the sound so you get a less than flat frequency response.

Also some will have internal DSP and a choice of EQ curves that suit different applications. E.g. you may have ‘flat’ for general FOH use, ‘scooped’ with more bass and treble and less mids for recorded music playback (I don’t like this myself but in may help on speakers that are naturally mid-heavy), ‘speech’ where there is less bass and more mids to make voices cut through in vocal-only use and ‘monitor’, where the bass frequencies are rolled off so if the speaker is used as a monitor in a large PA system with subs, then it doesn‘t add to the level of bass on the stage as there will be a lot coming back from the subs, and so reduces the risk of feedback.

So whilst a speaker may not be inherently voiced for a particular application, selective EQ can make it more suitable for a particular task. But this can be applied from the desk just as well as within the speaker, provided the desk has the facilities available. Most digital desks have comprehensive EQ available for both the main and monitor speakers, and you then have more control over the sound, rather than choosing maybe one of three or four presets.

[John Egan]

Hi,
I must admit to struggling with Db ratings. Fortunately my interest is purely acadmic these days.
I do remember that through the 1960s, we used to use a Leak 30w amp driving 4x12" Goodmans Audiom 60(?) - 2 per side for vocals. We were playing some of the biggest venues in the country at the time and I don't remember sounding any lower in volume than any of the major artisis we were supporting (except for The Who).
I believe that modern volumes are higher, but the PA wattage ratings amaze me. Then again, I supose that it makes a difference when they are carrying the signals from the whole band ?
Regards, John

[BigRedX]

I do remember that through the 1960s, we used to use a Leak 30w amp driving 4x12" Goodmans Audiom 60(?) - 2 per side for vocals. We were playing some of the biggest venues in the country at the time and I don't remember sounding any lower in volume than any of the major artisis we were supporting (except for The Who).

As far as I can hear it's mostly down to the intelligibility of the vocals. When I started going to gigs in the late 70s the best you could hope for in the audience at most venues under 2000 capacity was that you could hear that someone on stage was actually singing. Whether they were singing the right words or in tune was anyone's guess.

In the last 20 years the quality of live sound has come on in leaps and bounds, and now everyone expects to be able to hear all the vocals and make out most of the words that are being sung. This requires much better performance from the PA than simply more SPL.

[stevekane]

Hi everyone,,Ive just got home and quickly checked the replies, which were all very interesting, I had posted a reply this morning, but no sign of it it here? I will do a proper reply tomorrow, and pick up a couple of the points, but before then many thanks to you all for taking the trouble to comment,
Steve.

[Wonks]

There have been problems with the website in the last 24 hours, so I expect your reply unfortunately got lost in some digital chaos.

[Philbo King]

Something a bit more helpful:
If you do outside gigs, the skinny-tower type PAs are not great. They are great for inside shows, and can avoid the need for stage wedge speakers, but they really need nearby wall(s) to work well.

[Wonks]

Something a bit more helpful:
If you do outside gigs, the skinny-tower type PAs are not great. They are great for inside shows, and can avoid the need for stage wedge speakers, but they really need nearby wall(s) to work well.

Yet quite a few people here have found the opposite. It really depends on the type of gig - what sort of music, how many people you are playing to and whether they are spread over a wide area or seated/standing in front of the stage.

I’d consider them for a spread-out audience with a fairly acoustic performance, but not a rock band or similar

Though certainly, you’d need a system at the more powerful end of the stick line-array + sub type for outside use, and at least a couple of them to provide monitoring as well for a large group on stage.

[Arpangel]

Interesting as this detour is, I'm not sure it's helping the OP much.

Come on Drew, I’m just trying to steer his career in a lucrative direction, and I’ve got one fan already, so as you can see, it’s got legs.

[Wonks]

And now there is loudness, we want some loudness,,SPL as is described in an excellent article on this site, it seems that according to the article a band like ours, playing small to medium venues and sometimes outside needs an SPL of around 125db,,which is Mackie Thump 1000w territory,,but Alto TX750w is just a mild 117db from memory,,,so I checked the spec sheet for our 400w yamaha and its given as SPL125db,,,rock band volume,,can this be right, what am I missing? Any help gratefully received.
Steve.

I’m not sure exactly what Alto speaker you were referring to with TX750w, but some of the confusion is down to the previously mentioned usage of ‘watts’. A lot of speakers are given a wattage figure based on the peak amount of power the internal amp can put out for a millisecond or so.

The base wattage figure used to be ‘RMS watts’, a misleading term but typically measured with a steady 1kHz sine wave input and the amp’s output very slightly distorting at around 1% THD. There is now an ISO standard for amp watts using a constant bandwidth limited pink noise signal, which normally results in a figure within 3-5% of the RMS value. This is the best indicator of how powerful an amp is IMO.

You then get ‘music’ or ‘program’ power watts. Music isn’t a constant tone, but dynamic and non-constant. One main limitation of how much power an amp can put out is its power supply. The capacitors in it store a reserve of energy that can be used when the input signal increases above the nominal max level to put out more power than the constant input from the PSU can normally provide. So as long as a brief loud section is followed by a quieter section, then the stored energy in the capacitors can be used and then recharged, allowing for signal peaks that would appear to come from a larger amp.

This extra ‘power’ is very program dependent and heavily compressed pre-recorded music is unlikely to show a volume increase over nominal, whilst very dynamic music with notes not too close together could give you a lot more.

But in general, music/program power is normally given as twice the RMS/ISO power rating by manufacturers, though it is open to misuse by marketing departments.

Note that doubling the power value doesn’t double the volume, as it's a 3dB increase in power.

And as already mentioned, there is ‘peak’ power, where they take the highest voltage level achievable from the shortest transient, and extrapolate that as if the amp could provide that constantly (which it can’t). In general, this figure is given as four times the RMS/ISO value, but is often given as a much higher value by unscrupulous vendors.

So a typical amp might be described as
300W/600W/1200W RMS/program/peak power in the specification section. But the advertising may well pick on the 1200W value without stating what sort of ‘watts’ they are.

So a ‘750W’ amp in a speaker may well only really be a quarter of that, say 150W in RMS terms, which is why a ‘750W’ speaker only gives 117dB SPL.

The other factor affecting speaker SPLs is the speaker sensitivity. A typical PA cone speaker will have a sensitivity of around 98dB SPL for 1W input at 1kHz. But it could be 95dB SPL or it could be 101dB SPL.

Which is why some speakers with say a 600W RMS amp have a higher SPL figure than others with a 600W power amp. A 101dB sensitivity speaker should be 6dB louder than a 95dB sensitivity speaker for the same power input.

Of course, nothing is straightforward. Some speakers’ SPL values are calculated from the sensitivity figure and the amp power rather than measured. e.g. a speaker with a 98dB SPL sensitivity figure and a 300W amp should produce an SPL of 98 + 24.8 = 122.8dB SPL. (the 24.8 figure comes from the dB increase in power of 10xLog(300W/1W). As sensitivity is always based on 1W (unless stated otherwise), then it’s 10xlog of the amp power which you add to the sensitivity figure to get the maximum SPL figure.

But if the speaker power rating is near the amp’s output value, the speaker might suffer from compression and not produce as much output when driven hard. So a measured SPL is preferable.

You can also work backwards to see if a speaker’s SPL figure ties up with the amp rating. So let’s take 125dB SPL from 400W for the Stagepas.

400W is a 26dB increase over 1W (26 = 10 x log 400), so a speaker sensitivity of 99dB SPL for 1W input seems reasonable if we assume the wattage figure is RMS or ISO.

[Drew Stephenson]

Excellent summary Wonks.

[shufflebeat]

Interesting as this detour is, I'm not sure it's helping the OP much.

Come on Drew, I’m just trying to steer his career in a lucrative direction, and I’ve got one fan already, so as you can see, it’s got legs.

Could be life-changing (possibly not for the better).

Mmm… banjo with legs…

Excellent summary Wonks.

And an explanation very much appreciated by those of us who deal with the numbers but haven’t dove/dived into the reasons for the various values.

[Wonks]

In terms of doubling of volume, it's not a cut and dried value. You can't simply say10dB SPL is a doubling of volume. A lot of sources on the web will say that 10dB SPL change is perceived as a doubling in volume, but others say it may be from 6dB.

Technically, a 6dB increase in SPL doubles the sound pressure produced, which should be a doubling of volume. But you are then reliant on the human ear and brain to turn that extra sound pressure into a volume signal, and that runs into the world of psychoacoustics.

For a start, a 6dB increase in volume is perceived as a bigger change than a 6dB decrease in volume, so we know it can't be a strictly linear and repeatable thing.

There are also the Fletcher-Munson equal loudness curves for the ear's level-dependent frequency response (updated to the more accurate ISO 226:2003 curves). As things gets louder, our hearing is more sensitive to bass and treble, so a wide frequency-band sound will get subjectively louder quicker than a narrow frequency band sound centred on the most sensitive hearing frequencies around the 2kHz-5kHz region.

So a 6dB SPL increase will sound quieter at low volumes than at high volumes.

And then there's always a subjective element as to what constitutes a doubling in volume. If you do it gently, you may give a different response to a step change. If you go noise> quiet period > louder noise, would you give the same response to what was double the volume as going straight from one level to the next?

And if I told you that the second of two sounds I played back to you was double the volume of the first as a reference point, you might well believe that, even though it was only say a 4dB increase. That could well affect perception of other level differences played back afterwards. The mind is easily led astray.

But basically, in comparing SPL levels of speakers, 6dB is a significant difference, which some people might hear as double the volume, and some a bit less. 10dB is more of a difference (and definitely at least double the volume) and if louder is more good, then 10dB more SPL is betterer.

But sound quality also comes into consideration. You can have a loud PA but if it's really harsh and there's nasty things going on at crossover frequencies, then quieter is betterer!

Ideally you want a loud, good-sounding PA that's portable and fits in the back of a hatchback. And the wonder of it is that today, you can get such a PA, and you have a wide choice. Back when I started playing with bands, to get a 2kw rig, you needed as stack of separate cabinets; bass, middle and horn units, plus a rack of heavy amplifiers and a Transit van as a minimum to cart it round in. And hopefully some mates to roadie for you. Now you can get a similar performance from a couple of 8" tops and a single sub.

[stevekane]

Well Ive read it, and I cannot thank you enough for going to so much trouble, but theres so much to digest,,,Im at home tomorrow morning and will read it all again and then come back to you,,
Steve

[stevekane]

Good morning, Ive gone through it again but in truth Im no further forward,,when I made my initial post I was trying to “make sense of the figures” thinking that SPL figures were in fact some more scientific way in which volume/performance power was rated, sound BHP if you like, I then would only have to work through sound quality, which would be based on peoples opinion on what we could look at and no doubt cost,,,as someone has said, you get what you pay for, but sometimes you don't get what you pay for!
And it was whilst looking at Fletcher Munsen diagrams that I realised that Ive gone completely off the track, why does any sane person who only wants to ensure that a medium small audience can hear what the band is playing need to clog up their few remaining brain cells with the works of Fletcher Munsen and his pals,,I know that our little Yamaha Stagepas 400w, their smallest and most basic entry level plug n play outfit cannot be as loud as say a couple of 1300w active Mackies,,,no mater what the figures say. Maybe I should stick to Watts, big Watts= big sound, and before you say anything, remember that SPL is apparently just as inaccurate!
All joking aside, you've all been very helpful, and maybe my questain is really unanswerable?
Steve.

[Wonks]

No, stick to SPL for volume. Watts is almost irrelevant for active systems, and is only relevant when putting together power amps and passive speakers.

SPL is a much better indicator of volume than watts. Partly because there is only one meaning of SPL, whilst as previously explained, there are several different type of 'watts' and you often don't know which one the sales descriptions use.

Whilst SPL can also be a bit misused depending on how the figure is derived, it's a much better yardstick to determining speaker maximum volumes than watts.

A 132dB max SPL speaker is always going to be a lot louder than a 125dB max SPL speaker.

Whether a 128dB SPL speaker will be noticeably louder in use than a 126dB speaker from another manufacturer is another thing, but you know their volumes should be in the same ball park. But it helps you make an initial selection of system based on availability and price.

It's then down to your ears. You really want to go and hear some PA systems either in a store or in action. Hear speakers with and without a sub connected.

Even though you only have a cajon, they can be surprisingly bassy, so my own choice would be a small sub to go with some 8" or 10" tops. But it does obviously depend on budget and what you can afford to spend, and who gets to move the PA around. Even a 12" sub is going to be quite heavy and take up a reasonable amount of space.

The very cheap subs tend to be rather 'one note' and make a thud rather than be a musical extension of the tops. As you spend more, you get to the stage where the subs really support the low end of the tops and you get a seamless musical extension. Again, it's down to going and listening to some choices, ideally being able to play say single notes from a keyboard through them in the bass region to ensure the notes sound well defined and in tune.