How much power per person?

[ukpartydj]

I'm sure this question has been asked before (and yes I did have a quick scan to make sure it hasn't already been answered).

Basically I have 2x Mackie SRM-450's & 1x Mackie Thump 18".

I've done a drama hall before (high roof) with 100 kids and the SRM-450s they hold out fine but they get quite hot! And as I've mentioned before I've heard about these turning off due to overheating! I've never had them turn off myself and never had a warning light come on but the last thing I want to happen is these to cut out during the gig!

The most I've ever catered for is 150 people with my sub etc the speaker tick over nicely but I've been asked for a quote in a large high roof school hall for 300 people! - Picture of the Hall (http://www.ballhall.co.uk/case-studies/parkstone-grammar-school-for-girls-poole/)

I'm thinking If I hire out another subwoofer - plonk the 2 subs together for that little bit extra DB that will be alright?

I would also be useful for me to know how far everyone else pushes there equipment... how many speakers have you used before for how many people in what type of venue... I've never had to do over 150 people before so It's fairly new to me!

Thanks in advance!

Mobile DIsco DJs In Bournemouth (http://www.ukpartydj.com/)

[hammy]

Personally I would not use subs in a school gym, I took my subs out once in a gym and had to turn them off due to the amount of echo in a gym.

[surround sounds]

Yes i have to agree with Hammy on this one. School halls can be hard to work in with the echo..

[ukpartydj]

interesting ... like a echo off the far wall or like an echo behind the sub? would have thought people standing in front of the sub would stop any echo from a far wall?

I don't think I can get away with doing it without a sub - they want a "Rave".

do you think I'd be alright if I angled the Subs? I always angle my speakers to prevent echo from the back wall but Bass being omnidirectional may sound like it's just bouncing wherever it wants?

[Supreme Soundz]

as said above i personally think you'll also have trouble with echo in the hall? unless its rammed full of people and soft furnishings its just going to sound awful? i did a gig in a local golf clubs function sweet its all wooden clad inside, and no furnishings what so ever, used 2 opera live 405's sounded terrible, the only thing i could do to ever so slightly improve the echo was to not have the speakers pointing at 90 degrees to and wall so i turned them both out 45 degrees so the sound was bouncing around still sounded horrid

[CRAZY K]

as said above i personally think you'll also have trouble with echo in the hall? unless its rammed full of people and soft furnishings its just going to sound awful? i did a gig in a local golf clubs function sweet its all wooden clad inside, and no furnishings what so ever, used 2 opera live 405's sounded terrible, the only thing i could do to ever so slightly improve the echo was to not have the speakers pointing at 90 degrees to and wall so i turned them both out 45 degrees so the sound was bouncing around still sounded horrid

Very similar to problems on my last 2 gigs==School type Aircraft Hanger and a Golf Club with loads of wooden panels :eek:

I agree the subs might not help at the School Hall.

The high ceiling is a killer also.

Mackie Speakers that get hot have been ( allegedly on here) controlled by fitting clip on fans

Generally I would think you need to consider more sound power if its a Loud gig for such a big hall and 300 people.

I was working with my son in a Harlow College ( Rodeo bull job) and the sound system in the main Hall which I imagine would hold up to 300 had a 5kw Peavey system with a battery of ceiling fitted speakeers and massive subs.

Sounded great but shows the differences in approach:daft: :daft: :daft:

[ukpartydj]

Mackie Speakers that get hot have been ( allegedly on here) controlled by fitting clip on fans

Generally I would think you need to consider more sound power if its a Loud gig for such a big hall and 300 people.

I was working with my son in a Harlow College ( Rodeo bull job) and the sound system in the main Hall which I imagine would hold up to 300 had a 5kw Peavey system with a battery of ceiling fitted speakeers and massive subs.

Sounded great but shows the differences in approach:daft: :daft: :daft:

Hmmm, with my speakers and Sub I'm on about 2400 watts peak - 1300 watts RMS so it's only half of that really ...... :)

Maybe I should just turn the Bass down on the speakers - whack em up a notch and forget the sub :Tumble: haha!

I just can't see the point in getting say 4 speakers and no subs ... and no I'm not hanging any speakers from the roof! Maybe a horn loaded sub would work but they are pretty huge!

[thex-faders]

I think if they are having the hall with just you & people then subs are a no no as they will sound terrible.

But if they are planning on including tables for half the hall for say a sit down meal then it could sound ok once they are all up on the floor and absorbing the base to reduce echo around the hall.

Have you got an EQ? Could help with the echo?

Tom

[ukpartydj]

No separate EQ, probably no tables - might be ok if they draw one of them big curtains that they have in sports halls across as I bet they absorb quite a bit of sound.

[CRAZY K]

Hmmm, with my speakers and Sub I'm on about 2400 watts peak - 1300 watts RMS so it's only half of that really ...... :)

Maybe I should just turn the Bass down on the speakers - whack em up a notch and forget the sub :Tumble: haha!

I just can't see the point in getting say 4 speakers and no subs ... and no I'm not hanging any speakers from the roof! Maybe a horn loaded sub would work but they are pretty huge!

Possibly you havent seen the Pro install rigs in Colleges Clubs and Universities which I have worked and have speakers flown from the ceiling, plus Bass units to make your eyes water.

Specifically they are designed to overcome problems of large cavernous venues including acute angling to overcome sound problems.

They are designed for 300 / 500 people upwards and to be very loud.

Your Two Mackie SRMs and two bass units are fine for small/ medium events
but are not designed to overcome these problem venues.

As things are, usual Mobile Disco PA equipment which we can buy at affordable prices and carry comfortably in a standard vehicle has its limitations as to what we can get out of it which we have to accept.

As it happems theres nothing wrong with 4 full frequency cabinets of the right sort to do the job--I think allowing for the dreadful acoustics likely to be in the Hall you might have a problem with too much bass.

Good luck with it anyway.;)

Might be worth having a check over the inside beforehand to see how it looks.

You never know, they might have a better sound system install than yours;)

The College in Harlow we worked at had a system that was way beyond anything a standard Mobile DJ could offer.

[addoaddo]

The kind of hall is a help and a problem. As other have said the reverb around the room is going to cause a lot of problem and not just to the base but the choice is not yours so you will have to live with it and eq to get the best sound. The advantage is that the wall will not absorb the sound so you may not need as much power as you think.

Power is never a good way to judge a system as efficiency is much more important. Go with normal efficiency I work on 1K of RMS power (not program or peak) per 100 people and double it for a young crowd that want it loud.

5 – 6K should be about right which is a lot more than can be handled by a Sub and a couple of Mackies. You need to move away from “Disco” speakers and use a PA system to get the right sound. I hope you have quoted correctly for the Job.

I use Mackies for small jobs and never had a problem with over heating as they are Mark 2 version. I think it was mainly the Mark 1s that suffered.

[ukpartydj]

I have quoted a higher than normal price so I can hire some Speakers but then maybe not enough! Feel a bit of an idiot!

I can hire 4 x RCF Art 312A for £90 ... alongside 2 x Mackie SRM-450s and a Mackie 18" Sub that's 2.5K RMS.

For a Maximum of 300 people in a large hall ... I think I can get away with it

My SRM-450's did 100 kids in a high roof hall and they were pretty loud and nobody asked me to turn it up everyone was dancing and seemed happy!

that's 800 watts RMS ... I personally would have liked to get my sub out but I wanted to see how far I could push them.

I don't mean to be trying to accuse people of being wrong as I have little experience with the large halls but it just seems odd ...

800watts RMS= <100 people IMO
1300watts RMS = <200 people in small hall
5000watts RMS= 300 people

I know it's like cars most of them can reach 100mph but you need 3 times the power to get to 140mph ... but surely it isn't that steep? Or am the squire who is yet to learn the wise ways of the large Disco?

[addoaddo]

Sound is a strang beast, if my memory serves me right you need 10 times the power to double the sound level / increase it by 3dB

[katman]

Sound is a strang beast, if my memory serves me right you need 10 times the power to double the sound level / increase it by 3dB

Double the power to increase by 3db

Ten times the power to increase by 10dB which is a doubling of volume.

[woody2]

I can hire 4 x RCF Art 312A for £90 ... alongside 2 x Mackie SRM-450s and a Mackie 18" Sub that's 2.5K RMS.

For a Maximum of 300 people in a large hall ... I think I can get away with it



with comb filtering you could make the problem worse not better with more tops;)

[ukpartydj]

with comb filtering you could make the problem worse not better with more tops;)

I did actually think about this... hence my original wish to get more Subs ... I heard that if you join 2 cables together it creates a tiny delay that can boost the perceived sound by up to 6DB on the mids but phase cancellation will make the bass inaudible ... interesting stuff - research needed I feel ... off to google i go!

[ukpartydj]

Interesting - I understand comb filtering now ... the SRM450's have a 90 degree angle which would increase comb filtering even more!

I could set up speakers in all 4 corners would increase the area which would be "comb filtered" but the sound would be loud enough from all angles that the effect would be minimized and nobody would really be able to tell & it'd be really loud in the centre of the hall! I'd just need to get some 50m leads or something stupid haha!

[djeddie]

I heard that if you join 2 cables together it creates a tiny delay that can boost the perceived sound by up to 6DB on the mids but phase cancellation will make the bass inaudible ... interesting stuff - research needed I feel ... off to google i go!

Sorry, but that's complete garbage. I wouldn't bother wasting your time Googling.

[Corabar Entertainment]

Sorry, but that's complete garbage. I wouldn't bother wasting your time Googling.
I'm all for making sure that accurate information is posted, but it's not very helpful to just say that something someone has posted is garbage without posting some helpful information / advice to put over what you believe is the correct information! :rolleyes:

[djeddie]

What would you like me to put? I could write 5000+ words in full technical detail but doubt many would understand it. I wrote that comment to be plain and simple, the poster obviously got his information from somewhere (or someone who has absolutely no understanding of loudspeaker physics) and I simply wanted to say "don't waste your time".

[Corabar Entertainment]

What would you like me to put? I could write 5000+ words in full technical detail but doubt many would understand it. I wrote that comment to be plain and simple, the poster obviously got his information from somewhere (or someone who has absolutely no understanding of loudspeaker physics) and I simply wanted to say "don't waste your time".
Thanks for your help. :rolleyes:

[Solitaire Events Ltd]

What would you like me to put? I could write 5000+ words in full technical detail but doubt many would understand it. I wrote that comment to be plain and simple, the poster obviously got his information from somewhere (or someone who has absolutely no understanding of loudspeaker physics) and I simply wanted to say "don't waste your time".

Rude and patronising. Delightful. A real asset to the forum.

[addoaddo]

Interesting - I understand comb filtering now ... the SRM450's have a 90 degree angle which would increase comb filtering even more!

I could set up speakers in all 4 corners would increase the area which would be "comb filtered" but the sound would be loud enough from all angles that the effect would be minimized and nobody would really be able to tell & it'd be really loud in the centre of the hall! I'd just need to get some 50m leads or something stupid haha!

There is some truth in the theory, it is call the Haas effect. It is used in large rooms with a second PA stack. If the delay at the second stack is app 20msec more than the sound from the original stack the customer perceives that the sound is coming from the main stack of speakers as these appear louder.
In your situation I would not worry about this or comb filtering. The guest will be moving around so any dip in one frequency in one location will disappear as soon as they move.
Your proposal should be OK give your target audience. If the room was full of audio buffs you may have to think again.