a bigger system for more coverage?

[S&L]

a bigger system for more coverage?

 

as some of you will be aware, I'm working at the bottom end of the food chain, with smaller venues and tiny budgets, ]learning the trade as I go - but lately the shows are getting bigger and I have had a few in the last six months where my boxes really aren't big enough for the venues. in the latest case I had a really successful show and the band concerned want to use me again but only for smaller ]venue soI am wondering how to get better coverage and how to calculate adequate coverage for a room.

 

the sounds?...live bands of all sorts, bluegrass, pop, rock, funk and soul. predominantly pop/rock and funk though.

 

the boxes at present? (a) rig is adlib 15" tops, HK 15" subs, (b) rig is peavey 15" tops, carlsbro 15" subs. and yes I know that I could get better results with different mixes of boxes but they are what has been available to date for 'best fit' on a tight budget.

 

]the venues? the above have been fine for coverage in your average pubs, bars and function rooms with a capacity of circa 100. they have been found wanting (but got away with it) in venues that are deeper, say 20m, stage to back wall.

]in some cases this has been for weddings and so the volume at the back is not an issue but for arguments sake lets say I would like the sound to penetrate to the back in a rooms 10m x 20m with a crowd of 200. I don't want to deafen them but I do want to get to or slightly above conversational volume. obviously this will vary dependant on room characteristics but I'm looking to work up a wish list/shopping list to add to the above sets that would provide what I need in this size of room. while acknowledging that spl varies with box model I think we can deal in generalities enough to cover my shopping list.

[]the budget would be 2nd hand, probably above the ]level of peavey but up to the level of HK as an absolute maximum. with clarity still being preferable to volume.

so leaving aside box brand:

1. am I really going to get better coverage by using 6 boxes instead of 4?

2. if I use 6 boxes is that 4 subs, 2 tops, or 2 tops, 2 mids and 2 subs - and which configuration suits the above music best for clarity and penetration?

3. will a 6 box rig ever be sufficient or does it need more boxes - will boxes at one end of the room without repeater towers ever cover the full distance?

 

or am I missing the point entirely here?

[jbaileypro]

If you think your current rigs aren't big enough then be more specific in what you are missing? Have you walked around the venue to hear the coverage? Are you lacking high end or bass?

Some tips is the usual of getting your main speakers as high as possible and sometimes even angled. Is the dispersion pattern of the speakers right for the room? Using a crossover to remove any lower frequencies from the main speakers will also mean that you can usually drive them harder (as they aren't having to use lots of energy reproducing the low frequencies that are already reproduced by your subs). Are you driving the speakers correctly with the right amps? Are you having to push the system hard when you are using it?

Many systems you will see will be bottom heavy. Eg 2 subs to one top on each side. If you need to go lower or feel that there is a lacking in bass the you can always add a larger sub (eg a 18" sub will generally go lower than a smaller 15 that you have already have but will normally require more power though).

Again as many questions posted on here it is hard to tell without many other questions first.

[S&L]

If you think your current rigs aren't big enough then be more specific in what you are missing? Have you walked around the venue to hear the coverage? Are you lacking high end or bass?

Some tips is the usual of getting your main speakers as high as possible and sometimes even angled. Is the dispersion pattern of the speakers right for the room? Using a crossover to remove any lower frequencies from the main speakers will also mean that you can usually drive them harder (as they aren't having to use lots of energy reproducing the low frequencies that are already reproduced by your subs). Are you driving the speakers correctly with the right amps? Are you having to push the system hard when you are using it?

Many systems you will see will be bottom heavy. Eg 2 subs to one top on each side. If you need to go lower or feel that there is a lacking in bass the you can always add a larger sub (eg a 18" sub will generally go lower than a smaller 15 that you have already have but will normally require more power though).

Again as many questions posted on here it is hard to tell without many other questions first.

 

obviously it varies from venue to venue but all frequencies are missing in any volume at the back of the venues.

in most 200 capacity venues I work it isn't possible to get the height and coverage of all the crowd by lifting and angling speakers tho angling is something I could look at for the top end in some circumstances - it presumably wouldn't carry the bottom end tho.

both rigs already have 2 amps and active crossover - I never use a passive to split between subs and tops

I could drive the present rigs a little harder and upgrade amps. in the case if my (a) system:

2 no, adlib 15" top, 400w program 8 ohm driven by 600w peak 500w rms at 8 ohm per channel amp

2 no. HK 15" subs, 600w program 8 ohm driven by identical amp.

in the case of the (b) system the boxes are rated a little less and use similar powered amps.

I should confess that the HK's haven't been out to a bigger venue yet to see if they are lacking.

generally with the types of music played the tops amp is set lower in gain than the subs amp to get a sound that matches to the ear. once set that way, the gain from the desk once split by the crossover is much higher to the tops amp than the subs amp. i.e. subs amp at full gain but incoming gain on tick over, tops amp at 2/3 full gain with incoming gain not quite peaking amp. limiters engaged on both amps, crossover at 100 to 120hz dependant on rig and results in room.

with the rigs set as above the system is pushing as much as it can without tops amp peaking. the result is fine for a depth of 10m into the larger rooms but it struggles to reach the rear of these rooms, usually the deficit is even across the frequency range.

[stagemanagement]

1. am I really going to get better coverage by using 6 boxes instead of 4?

 

In theory, yes; as two loudspeakers will couple together to increase the available SPL compared to one.

 

 

2. if I use 6 boxes is that 4 subs, 2 tops, or 2 tops, 2 mids and 2 subs - and which configuration suits the above music best for clarity and penetration?

 

This depends entirely on the boxes and the job in question - a wide room with modest SPL requirements for a standard wedding band would perhaps be best served by 2 subs and 4 tops arrayed to give a full coverage across the space. A narrow venue with high SPL requirements for dance music would be better served by 4 subs and two tops.

 

 

3. will a 6 box rig ever be sufficient or does it need more boxes - will boxes at one end of the room without repeater towers ever cover the full distance?

 

Again, this depends on the venue and the SPL required for the programme; sometimes one very well designed loudspeaker is plenty, sometimes 10 poorly designed ones is not enough.

The simple way to work these things out is to ask what level do I need/want at the back and work from there. All loudspeakers have a given max SPL rating, which is measured at 1m from the cabinet; inverse square law dictates that the SPL level will drop 6dB for every doubling of that distance e,g 136dB SPL @1m becomes 130dB SPL @ 2m, 124 dBSPL @4m, 118dB SPL @8m and so on.

[mackerr]

1. am I really going to get better coverage by using 6 boxes instead of 4?

 

In theory, yes; as two loudspeakers will couple together to increase the available SPL compared to one.

 

Only in the low end. Once the wavelength gets smaller than about 4x the driver spacing they begin to cancel each other out at various frequencies (comb filter). While the bass gets louder and the mids and highs don't the tonal balance changes. More speakers is about better coverage, not louder, and requires different eq.

 

Mac

[S&L]

I can see even though this is a theoretical exercise, I am going to have to place some specific parameters on it.

so lets say 20m deep room x 8m wide x 2.8m high (the last room I worked where this problem)

lets assume I can afford some HK actor gear - unlikely but I can adjust later - they would give me 104db spl at 1m as individual boxes.

lets say that I want 60/65db spl at the back of the 20m room but that I want all the speakers to be either side of the stage at the other end.

lets assume the stage is 4/5m wide and speakers are in front of stage at either side.

 

if 65db at 20m is ok then I calculate 91db is required at 1m and therefore 2 hk tops and 2 subs more than fit the bill.

if I use my adlib tops they give 97db at 1m which should still satisfy the criteria..

..yet it doesn't. you can't really here the band over the conversation meaning subjectively the band is below 60db at 20m.

but bodies soak up sound - is there a calc to reduce db per body soak up?

or am experiencing comb filtering as mackerr suggests?

and if I am how would I overcome the issue without repeaters?

or is this this about under powering the speakers and not achieving spl?

(next big room I do I WILL take a sound meter out)

[stagemanagement]

As a general rule, background noise level is going to be in excess of 65dB in a normal environment; even more so in a gig environment where people are chatting quite loudlyy to compensate for the music around them.

And you are right that people (and furnishings) absorb sound - so your "65db at 20m is ok", was never okay in the first place.

 

I would suggest that no matter the venue size, if you are doing a gig with a band, then the minimum you are going to require at the back of the room is around 80dB, if that is also the mix position then you will probably want somewhere around 86-90dB min, so you can pick things out of the mix without difficulty - most riders I receive will stipulate anywhere between 106-116dB at the mix position to allow enough headroom in a system.

Working from there, 80dB @ 20m is 86dB @ 10m, 92dB @ 5m, 98dB @ 2.5m, reaching a minimum SPL of 106dB @ 1.5m; if a value of 90dB is required, then working through the same process gives you a requirement of 114dB @ 1.5m - requiring a cabinet capable of around 118dB @ 1m to achieve this.

 

I don't think the level issues you are experiencing are related to comb filtering, that would be apparent as level drops at certain frequencies in certain areas of the room - not the inability to listen to the band above the chatty punter 3 feet away from you at the back.

 

As Mac has said, you will get comb filtering from arraying multiple cabinets above a certain frequency threshold - but that's real world audio and you don't ever get rid of that entirely; that's why manufacturers at the high spend so much money on R&D to minimise it's effect in larger scale systems. Balancing out coverage, SPL and tonality is a compromise to achieve a balance between all three requirements - but without enough SPL, the other two factors are pretty much redundant.

If you do find combing issues when arraying multiple cabinets, then experiment with how you are aiming them, set a 45 degree angle between the cabs that are side by side and adjust wider and narrower splay from there, until you find a workable solution to the problems.

[S&L]

80db at the rear - okie dokie, now I know what's acceptable for calculation purposes - that helps thanks.

the venue I described was a modern working men's club, average demographic was about 30 to 45, some younger a few older. in venuew like this I rarely get a mix position at the back. in this case I was 6m or so from the front of the stage. the drop in level wasn't that apparent at sound check but once 200 bodies were in place it was more than apparent.

so sticking with the example and saying this requires 106db at 1m, I'm almost there with the HK spec of 104db at 1m (78db at 20m)..using 1 top

..but if I wanted to use my adlib tops with 97db at 1m performance, I calculate that I would need 5 of those tops to reach 104db at 1m.

 

I think if this is right then I have the hang of it now! ..and in doing so have filled another hole in my knowledge

[MrBoomal]

Can you not, just use your Peavey top's as delays, set half way down the room ?

[Shez]

HK actor gear - unlikely but I can adjust later - they would give me 104db spl at 1m as individual boxes.

<snip>

if I use my adlib tops they give 97db at 1m

Are you looking at the sensitivity figure rather than the maximum SPL? Even cheapo boxes will get well over 100dBspl with the good ones reaching 136+.

[S&L]

@Shez

to be honest I'm not sure....the adlibs are old versions of their AA151 which they quote on their web site as spl @1m 97db but they don't say if that's peak or not.

 

@MrBoomal

quality of the peaveys not withstanding, in most of these function rooms and large bars it's a fight to get ANY mix position, putting speakers in amongst the crowd as repeaters is a non starter - the building operators won't wear it...even though in the example I gave they asked if we could turn it up a bit.

 

generally, I am wondering if there is scope for uprating my amps to push the speakers further,

[JLEvents]

@Shez

to be honest I'm not sure....the adlibs are old versions of their AA151 which they quote on their web site as spl @1m 97db but they don't say if that's peak or not.

 

 

Just to throw my 2p in here, I had the Adlib AA151's which were rated at 97db as correctly stated above. I've now got RCF 302 which are rated at 127db (max spl) and the Adlibs sounded much louder!!

[Shez]

To put things in to context, the venerable little JBL control 1 manages a continuous maximum SPL of 108dBspl which would sound twice as loud as your boxes if they really did max out at 97. That's almost certainly the sensitivity measurement which gives you a theoretical max spl of 123dB (ignoring power compression and other loses). For a 15" PA cab, that sounds slightly more realistic.