Seeking advice: interesting charity sound installation

[mark76uk]

Hello,

 

I'm an IT Technician at a residential college for 60 students with disabilities. We had £2700 donated (the college is part of a charity) for theatre equipment. This is the first investment in sound/lights for ten or fifteen years!

 

I'm a lighting guy, but planning the sound part is marginally worrying. Maybe someone can give some input, if you have a moment? I have researched this a lot, as I knew nothing about watts and ohms before!

 

The student common room is where most of our events occur, including discos, theatre, graduation and christmas concerts, etc. It's approximately 20 metres by 8 metres and 3 metres high.

 

The plan so far: We plan to have four speakers on swivel wall brackets. Diagram is below! This is because events may be staged anywhere in the room. Discos and theatre events are mostly staged at one end of the room, but some musical events are staged in the centre.

 

I plan to get a Behringer UB2442FX-PRO Mixer and two stereo amps. The mixer has four subgroups. Each subgroup output will control one speaker. In this way all four speakers can be used appropriate to the position of a performance. We have had a problem using just two speakers - a sonic blast near the front so that people near the back may hear. The four speaker solution will act like additional speaker towers at the back of an outdoor concert.

 

The sound equipment (amp, mixer, cd) will be on a rackmount trolley. To avoid cables crossing doors there'll be four sockets where the trolley can be plugged-in. These will be 8pin Speakon connectors, cabled up the wall using 8core 2.5mm cable to a central point of 'choc block' connector inside the ceiling. From this central joiner 2core 2.5mm cable will distribute the power out to the speakers. In this way, the sound trolley can be situated anywhere, with a single 8core cable plugged into any of the wall sockets.

 

Sound cabling:

http://www.markmajor.com/external/soundlight/sound.gif

 

Originally, we had a local sound guy give us a quote. He specified four Behringer TRUTH B2031P monitor speakers (150w max, 4ohm, 89db sensitivity, 9" woofer) and an Inter-M QD4480 (4 x 120w @ 4ohm) amp. This setup wouldn't be good for a disco? According to the crownaudio.com amp power calculator, it'd give us about 85dBSPL at 6metres with 9dB headroom. I don't know exactly how loud our previous discos were, as I only just purchased a sound meter. It really wasn't quiet!

 

Questions you might be able to help with: I have ideas, but a few worries due to my lack of experience with these things (I knew much less about amps and speakers before this week!):

 

*** Our current speakers are (fancy domestic?) Jamo GF25 150w, driven by a 85w Sampson Servo amp. Should I be going for 12" woofers again? Should I be going for approx 150w again? Playing CDs gives a loud and solid sound in my opinion, but 15" cones would improve bass further?

 

*** Speakers with 15" woofers put out too much power for the size of our room? Peavey Messenger Pro-15s (250w RMS, 500w program, 1000w peak, 4ohm, 98dB efficiency) are just £73.44 each exc VAT on Thomann, but a 700w amp would give 95dBSPL at 6metres with 16dB headroom!? I'm not sure about 111dBSPL in a room where some of the students can't put their hands over their ears or leave without assistance! EDIT: just got the sound meter out and turned my music up to about 100dBSPL(A) average maybe that's not too bad. Otherwise, I can get Peavey Messenger ST12 Speakers (125w RMS, 250w program, 500w peak, 8ohm, 95dB efficiency, 12" woofer.) for £68.65 each exc VAT. A 450w amp would give 95dBSPL at 6metres with 11dB headroom?

 

*** The average length of cable from amp to speaker will be about 18m through 2.5mm squared cable. Do you think this have significant effect on the sound? Damping factor?! SPL? If I use 4ohm speakers or 8ohm? Will there be signal loss or other problem caused by the big spider of cable leading from the middle of the ceiling to all the trolley-sockets and speakers? Only one will be in use at any time, but the live cabling will connect to all the others!

 

Brand wise, I'm currently looking at Peavey speakers with Thomann 'The Box' amps. I guess these aren't too bad!? I'm not looking for breathtaking quality, just a decent installation for use about five times a year. The equipment will be in a 19" 12x10U Gator wheeled trolley, so it should have a fairly easy life!

 

Thanks for your time,

Mark

[Chris Hinds]

It's approximately 20 metres by 8 metres and 3 metres high.

 

Discos and theatre events are mostly staged at one end of the room, but some musical events are staged in the centre.

My immediate concern looking at the diagram is when the system is used to reinforce sound as in the second diagram. Assuming the distance between the two speakers is (horizontally) about 6m, then the people sitting in the coverage of the back set will hear the sound from the speaker near them, then a few ms later they'll hear the sound from the front speakers as an echo. This will reduce clarity at the back of the room, causing you to raise the volume to try and increase clarity, which makes it worse because the echo is now louder etc etc.

 

I plan to get a Behringer UB2442FX-PRO Mixer and two stereo amps. The mixer has four subgroups. Each subgroup output will control one speaker. In this way all four speakers can be used appropriate to the position of a performance. We have had a problem using just two speakers - a sonic blast near the front so that people near the back may hear. The four speaker solution will act like additional speaker towers at the back of an outdoor concert.

How long do you hope this will last? I can tell you that mixer is unlikely to see the end of 18 months of regular use. Faders will get stickier, knobs will fall off and gain pots will suddenly develop dead spots right where you want to use them. Some of your blasting problem is to do with having the incorrect type of system in there currently... but see later. I'd plan to spend a little more of your budget on the mixing desk. If you have significant amounts of money to spare then try an A&H MixWizard, if you don't then the Yamaha MG series or Soundcraft Spirit E series are better built for little more money.

 

To avoid cables crossing doors there'll be four sockets where the trolley can be plugged-in. These will be 8pin Speakon connectors, cabled up the wall using 8core 2.5mm cable to a central point of 'choc block' connector inside the ceiling. From this central joiner 2core 2.5mm cable will distribute the power out to the speakers. In this way, the sound trolley can be situated anywhere, with a single 8core cable plugged into any of the wall sockets.

I can't see any immediate problem with that, except someone inadvertantly plugging two inputs into the NL8 sockets. Unlikely in your setup though. It will increase your speaker cable runs somewhat accentuating your losses. Some runs will be over 20m, which is a fair amount of cable. Having said that I've driven almost that far to speakers pushing a lot more current that you will be, and you just accept a little loss in power.

 

Originally, we had a local sound guy give us a quote. He specified four Behringer TRUTH B2031P monitor speakers (150w max, 4ohm, 89db sensitivity, 9" woofer) and an Inter-M QD4480 (4 x 120w @ 4ohm) amp. This setup wouldn't be good for a disco?

He's a sound guy??? Or he's a a guy who once sold you some cable. The speakers are TOTALLY wrong for the purpose, being designed for a nearfield monitoring application (or rather ripped off from someone else's nearfield monitoring application). They are also underpowered. Your current speakers don't sound exactly right for the purpose either and I suspect given the amp combination that they are infact clipping like mad at high levels making it seem louder than it is due to distortion. Yes I would be looking at 12" or 15" driver speakers. If vocals are your priority, go with 12", if level and LF response is go with 15s.

 

Speakers with 15" woofers put out too much power for the size of our room? Just got the sound meter out and turned my music up to about 100dBSPL(A) average maybe that's not too bad.

Good to see you are thinking about headroom as well as average level. You are going to suffer a degree of power compression with any speaker, but with lower cost speakers it is going to be worse. 100dB(A) is not too bad, though it's a little loud for long term use. Having said that I suspect you did this with the room empty. When you stick 60 'sacks of water' i.e. people in the room you will lose a fair amount of level due to absorption by the body. 15" drivers will not put out too much level for your room - It's just a case of a 15 being rather less suited to vocal work generally, because the driver is being asked to work to around 1.8kHz which is somewhat beyond where it is comfortable.

 

The average length of cable from amp to speaker will be about 18m through 2.5mm squared cable. Do you think this have significant effect on the sound? Damping factor?! SPL? If I use 4ohm speakers or 8ohm? Will there be signal loss or other problem caused by the big spider of cable leading from the middle of the ceiling to all the trolley-sockets and speakers?

Answers in order: Yes, Yes, Yes, No - you'll just lose more with 4ohm cabs as the current will be higher, increasing the loss, Possibly.

 

Brand wise, I'm currently looking at Peavey speakers with Thomann 'The Box' amps. I guess these aren't too bad!? I'm not looking for breathtaking quality, just a decent installation for use about five times a year. The equipment will be in a 19" 12x10U Gator wheeled trolley, so it should have a fairly easy life!

The Peavey speakers are good value and while you could never accuse them of sounding great, they will work fine. You can get cheaper racks than the Gator ones that will protect better too. "The Noizeworks" make some perfectly acceptable racks and I paid £150 for a rack 16x10u in wood not plastic. Seems to be built fine, and capable of protecting the gear too.

 

I didn't see the comment about how often it was going to be used until now. If you are only going to use it five times a year, then WHY are you investing in equipment and cabling? I reckon that you'll spend based on your current choices a little bit over £1250, maybe £1500 on sound once it's installed. Not wishing to be too blunt, you could hire a proper, professional level system for £100 a day that would do the job better by a long shot. You could hire for 3 years without any major issues, and also that's based on a fairly pricey solution using D&B Speakers/Amps. If you wanted to do the same kind of level system as you're proposing to install, well my local music shop will hire you that gear for £35 a day. In that situ you could run for nearly 9 years. By which time the horns in your speakers would probably have blown, your mixer would have died (three times, each time just out of warranty) and your wall cables would have been bashed into several times too. It doesn't make sense to me to buy the gear for such limited use.

 

Having said that, if you must buy the gear I'd look at the following:

Yamaha MG Series Mixer

Behringer EP2500 Amp

Peavey ST12 speakers

Noizeworks case.

 

Don't bother with 4 speakers, you'll cost yourself more problems than you'll solve due to the need for a delay on the rear speakers. If you can, install the amp and run signal cables at line level from the mixer to the a patch panel near the amp and do it that way.

 

Hope that's of some use.

 

Chris

[paulears]

Chris said.

My immediate concern looking at the diagram is when the system is used to reinforce sound as in the second diagram. Assuming the distance between the two speakers is (horizontally) about 6m, then the people sitting in the coverage of the back set will hear the sound from the speaker near them, then a few ms later they'll hear the sound from the front speakers as an echo. This will reduce clarity at the back of the room, causing you to raise the volume to try and increase clarity, which makes it worse because the echo is now louder etc etc.

 

 

 

- er.... we are talking 6m - as in 6ms delay. This is actually less than the typical reverb early reflection time. Hearing the sound as an echo is impossible. Let's be honest, we are talking about a basic spec system here - the equipment quality will mask the main deficiencies of the room. The result will be a coloured sound, probably made worse by the bottom end that won't sit well in a smallish space like this. Assuming there is no acoustic treatment, then the snags will probably be that left right separation will be poor, and imaging either very confused or just sound mono. Depending on the listener position there will, as already desribed, be multipaths to the listeners. These will all confuse the image further, but just 'smear' the sound, not create distinct time arrival problems. Although they will be there, they won't be obvious to the listener as a series of separate arrivals - just a kind of wall of sound.

 

Reducing the system to just 2 loudspeakers will improve the 'quality' but have an impact on level at the rear. If the use is for loud, in your face sound for dance - then doubling the number of cabinets helps keep levels similar throughout the room. If you want quality, accept lower levels in some parts.

 

The type of cabinets you have in mind are pretty wide dispersal at MF but probably have a fairly narrow HF dispersal, so expect changes in the HF level as you walk the room.

 

One thing - DON'T think of using studio monitors for this type of thing.

1. They have a pretty flat response, and you'll be sticking bass heavy stuff through them - I'd bet you fry them very quickly.

2. They sound grim in a studio - but that isn't what they are about - they are designed with the neutral frequency response so as to reveal the truth about the sound source, knowing that most listeners then listen on far less revealing speakers. Most studios use this type of dreadful (musically) sounding speaker for this purpose.

3. The bass output is pretty terrible.

4. The volume is meagre, despite the hefty power handling capability

 

If you choose small speakers, you need subs, not just for true sub frequencies, but to simply get some output below 100Hz.

 

I'd suggest you look carefully at what you want to achieve. Quality background at low levels or nightclub levels with extended LF response. Whatever you do, if you don't know the kit, don't be swayed by the specs, and don't ever take a recommendation from anyone who just has the net and a few catalogues. Why not get a dealer to bring you some kit, stick it in and have a listen. If they want your money they will do it!

Paul

[Bobbsy]

- er.... we are talking 6m - as in 6ms delay. This is actually less than the typical reverb early reflection time.

 

Er, isn't it more like 20ms, using my "back of the envelope" figure of 1ms per foot? This IS getting into the range where it can be perceived as a slight echo....I seem to remember some tests back when I was in uni where the perception of a delay disappeared somewhere in the 10-15ms range.

 

In any case, depending on exactly how the room will be used, it's not unusual to WANT am SPL gradient, allowing the headbangers to get up where it's loud, and the old fogies like me to hide in the back and try to talk! I'd think a single pair of speakers would reduce installation and cabling costs too...maybe allowing better quality components for the ones you do put in.

 

Bob

[paulears]

Bob 20ms is the figure for the single delay from one to another, but if you draw in the speaker on the opposite side (as in making a triangle) then the difference in path lengths is just under 6ms from the extra path length. Plotting these out, with the speakers just a small distance off the extreme edges results in these short delays. The trouble is, as we have all said, the combination of all these source points means pretty iffy sound. I'm not sure if intelligability of speech is compromised, but any attempt at proper stereo is going to be quite difficult

[mackerr]

- er.... we are talking 6m - as in 6ms delay.

UH...I don't know what fluid sound travels through to get to your ears, but through air it takes closer to 20ms to travel 6 meters. This is enough to cause articulation loss.

 

Mac

[Chris Hinds]

through air it takes closer to 20ms to travel 6 meters. This is enough to cause articulation loss.

Mac

I *thought* it was 20ms not 6ms! Initally wondered if the beverages of last night had confused me this morning!

 

Regards

 

Chris

[paulears]

so many posts in just a few minutes. The room intrigued me so I've just scaled it up properly based on the sizes. There are some extra problems with some areas of the room I didn't notice. I've used the op's dimensions and the worst case maximum distance is over 16m using this, makes the maximum delay from cab to ear about 49ms - very close to the delay where a discrete echo can be detected. The other path lengths are much less.

 

The other thing that occurs to me is that the plan shows the speakers facing in, rather than along - this should help people within the central area, but the HF roll off to people at the ends would probably be the worst feature, probably making it very dull at just the point where the multiple paths cause the most damage to clarity.

 

All in all, and I'm sure the one thing we agree on, is that it will sound very strange.

paul

[mark76uk]

Thanks to everyone for their input - especially Chris who jumped in first! I have the OK to start spending this money, so I'm reading very carefully! Some more details are below and any further input is very welcome I'm sorry I couldn't get the nice forum quotes thing to work.

 

 

 

2 OR 4 SPEAKERS? BUY OR HIRE?

paulears Reducing the system to just 2 loudspeakers will improve the 'quality' but have an impact on level at the rear. If the use is for loud, in your face sound for dance - then doubling the number of cabinets helps keep levels similar throughout the room. If you want quality, accept lower levels in some parts.

chris Don't bother with 4 speakers, you'll cost yourself more problems than you'll solve due to the need for a delay on the rear speakers.

bobbsy depending on exactly how the room will be used, it's not unusual to WANT am SPL gradient, allowing the headbangers to get up where it's loud, and the old fogies like me to hide in the back and try to talk! I'd think a single pair of speakers would reduce installation and cabling costs too...maybe allowing better quality components for the ones you do put in.

chris If you are only going to use it five times a year, then WHY are you investing in equipment and cabling? I reckon that you'll spend based on your current choices a little bit over £1250, maybe £1500 on sound once it's installed. Not wishing to be too blunt, you could hire a proper, professional level system for £100 a day

Reasons for purchasing and installing (rather than hiring) four (rather than two) speakers:

(1) The organisation who donated the cash want a photo opportunity and/or to know their money bought 'something.' I don't know which, and I'm not arguing with £2700!

(2) At most, I get one day in the room prior to the performance. Usually this is while they're doing the first of two full rehearsals! A plug and play solution will allow me to focus on what I'm actually going to 'do' with the equipment, rather than dancing about with misc audio components and taping dozens of cables around the place. Similarly, for lighting, distributed dimming and pre-wired DMX cables will remove the need to tape hoards of mains cables in every direction. There are four fire exits in the room, so a lot of these cables are taped very carefully (but probably illegally) over doors. The sound cabling and sockets will cost £200ish, plus £70 to add the DMX (lighting control) circuit. The audio cable I plan to use is the Cordial brand from thomann.de I'm sure it'll be good enough for our purposes.

 

Four speakers is kind of key to the strategy. That the four speakers will be on the wall and ready to go, and two of those will inevitably be in a position downstage of any event.

This was my imagined strategy:

*** Discos, the four speakers will all be pointed to the centre, perhaps with the 'rear' two EQd to deal purely with bass?

*** For productions staged in the centre of the room, the four speakers will be pointed 'outwards', towards the audience at either end.

*** For spoken presentations, as in the little diagram where the 'rear' two speakers give a slight boost to audience at the back.

*** For theatre, as with presentations. Perhaps with the addition of surround or directional effects.

 

Four speakers wasn't my idea by the way, it was the Head of Education! I just figured out a lot more ways it could be useful.

 

 

 

WOOFERS: 12" or 15"?

paulearsI'd suggest you look carefully at what you want to achieve. Quality background at low levels or nightclub levels with extended LF response.

I would be looking at 12" or 15" driver speakers. If vocals are your priority, go with 12", if level and LF response is go with 15s.

15" drivers will not put out too much level for your room - It's just a case of a 15 being rather less suited to vocal work generally, because the driver is being asked to work to around 1.8kHz which is somewhat beyond where it is comfortable.

I am confused that the bass on our existing 12" speakers sounds quite solid. Maybe they're just 'good' speakers, or maybe I don't know what I'm missing. What does anyone think of the idea of EQing the 'rear' two speakers to concentrate largely on bass? Maybe this would get more out of the 12"? Wouldn't the tweater handle the 1.8kHz (and upper) range?

 

 

 

PRICING AND CHOICE OF EQUIPMENT

I can tell you that mixer is unlikely to see the end of 18 months of regular use.

We do have a small Behringer desk which has been doing fine for ten years, but perhaps the manufacturing happened differently back then.

 

If you have significant amounts of money to spare then try an A&H MixWizard, if you don't then the Yamaha MG series or Soundcraft Spirit E series are better built for little more money.

I'll take a look, but the four sub master thing may be quite important. I'm not sure I can get any other desk with four subs for a similar price. Four subs allows one-fader control per speaker, on the rare occasions that I won't be there to explain about aux sends or rewire or patch or somesuch.

 

"The Noizeworks" make some perfectly acceptable racks and I paid £150 for a rack 16x10u in wood not plastic. Seems to be built fine, and capable of protecting the gear too.

I'm tempted by the £159 16x10 rack. Delivery and VAT considered, it's the same price as the 'Gator 10x12' I've been offered by proaudiosystems.co.uk (I wrote saying we're a charity)

 

paulears Why not get a dealer to bring you some kit, stick it in and have a listen. If they want your money they will do it!

Just trying to get more for the money. Compare prices on thomann.de to buying from a dealer who's hauled stuff over to the college for a demo. Although a well intentioned dealer will try to offer you the best for your budget, he'll only offer products he can source and will also add a fair profit for himself.

 

If you can, install the amp and run signal cables at line level from the mixer to the a patch panel near the amp and do it that way.

I like that idea. Routing speaker-level signals around the room seems more reliable though. You think that long runs of signal level cable are preferable to long runs of speaker level cable? More of the problem is that the subgroup outputs are jack, rather than balanced XLR?[/color][/I]

 

 

 

REFLECTIONS AND DELAY

mackerr through air it takes closer to 20ms to travel 6 meters. This is enough to cause articulation loss.

paulears Assuming there is no acoustic treatment, then the snags will probably be that left right separation will be poor, and imaging either very confused or just sound mono. Depending on the listener position there will, as already desribed, be multipaths to the listeners. These will all confuse the image further, but just 'smear' the sound, not create distinct time arrival problems. Although they will be there, they won't be obvious to the listener as a series of separate arrivals - just a kind of wall of sound.

paulears The room intrigued me so I've just scaled it up properly based on the sizes. There are some extra problems with some areas of the room I didn't notice. I've used the op's dimensions and the worst case maximum distance is over 16m using this, makes the maximum delay from cab to ear about 49ms - very close to the delay where a discrete echo can be detected. The other path lengths are much less.

Thanks for the attention to detail! I went and read about early and late reflections at http://www.church-acoustics.com/aa102.htm (very good.) This is a little worrying, as the new flooring is very solid (feels like rock when you touch it.) One wall has a lot of big windows with blinds, but the others are fairly bare. The ceiling has those polystyrene looking ceiling tiles. Surely these 'multipaths' go untreated in 80% of entertainment venues? Do people really notice?

 

Early on, I did look at getting four Behringer Sharks to add delay and feedback killing. I was hoping that the 8metre delay wasn't going to be tremendously significant though. Would adding delay solve most of the problem, most of the time? I guess you're going to tell me that a good EQ will be better for the feedback killing. I just read about compression on vocals too - our students singing can vary from whispers to shouts! :o

 

When you stick 60 'sacks of water' i.e. people in the room you will lose a fair amount of level due to absorption by the body.

Yes, I'm hoping this may be a saving grace with the late reflections. Quite often, for the more audio-critical events such as spoken presentations or theatre, the room is wall to wall, shoulder to shoulder with 'sacks of water.' Maybe I can get people to hold polystyrene sheets above their heads? :D

 

 

 

THE MONITOR SPEAKERS :)

He's a sound guy??? Or he's a a guy who once sold you some cable.

paulears One thing - DON'T think of using studio monitors for this type of thing.

paulears don't ever take a recommendation from anyone who just has the net and a few catalogues.

Actually, we contacted two local guys who had adverts on the Yellow Pages website. The guy who specified the Behringer Truth monitor speakers was going to charge £1790 plus £410 installation. The other guy quoted £3329 which was immediately over budget. I calculated how much mark-up they'd added to the basic equipment cost and started to formulate a plan based on the ideas we had exchanged during the consultation (mostly mine, as I was doing the specifying.) I then based my plan on much of the Behringer stuff the cheaper bloke had specified. Then I started to worry about the 9" woofers for bass. Then I started to research SPL, ohms, prices and watts, etc. And here I am.

 

Thanks again,

Mark :)

[sparkyweb]

I like that idea. Routing speaker-level signals around the room seems more reliable though. You think that long runs of signal level cable are preferable to long runs of speaker level cable?

 

Long runs of signal cable are less likely to have interferance. Long lines of speaker cable can be susceptable to RF interferance and then there is power loss....

 

Have found this post very informative and learnt a few things too- Ta

 

Mark

[Chris Hinds]

Reasons for purchasing and installing (rather than hiring) four (rather than two) speakers:

(1) The organisation who donated the cash want a photo opportunity and/or to know their money bought 'something.'

The audio cable I plan to use is the Cordial brand from thomann.de I'm sure it'll be good enough for our purposes.

OK cool, I wasn't certain but suspected that might be at least part of the reason. It's understandable if they wish to raise their profile some. I haven't heard of the cable you intend to use, but a quick look on Thomann looks like the 22AWG mic cable comes up to what I'd expect. I doubt it's hugely different to the normal stuff I use which is made by VDC. How much more a reel that is I'm not sure, but probably about £15-20.

 

Four speakers is kind of key to the strategy. That the four speakers will be on the wall and ready to go, and two of those will inevitably be in a position downstage of any event.

This was my imagined strategy:

*** Discos, the four speakers will all be pointed to the centre, perhaps with the 'rear' two EQd to deal purely with bass?

EQ'd for just Bass sounds like a less than desirable situation. Using huge amounts of EQ cut (as you would be) would dramatically affect the phase of the signal output, as well as being less than desirable in terms of a smooth roll off. You would be better leaving the speakers full range.

 

*** For productions staged in the centre of the room, the four speakers will be pointed 'outwards', towards the audience at either end.

Fine, no issues with that at all.

 

 

*** For spoken presentations, as in the little diagram where the 'rear' two speakers give a slight boost to audience at the back.

*** For theatre, as with presentations. Perhaps with the addition of surround or directional effects.

Here is where I think you will need a 20ms or so delay on the feed to the rear speakers. Due to the Haas effect you can over delay a little and get away with it ok, so 20-22ms would be a good ball park to start with assuming the speakers are 6m apart (which was my guess). Basically work out the time it takes for sound to move the distance and then add up to 15ms to that time, I tend towards adding 2-3ms most times.

 

I am confused that the bass on our existing 12" speakers sounds quite solid. Maybe they're just 'good' speakers, or maybe I don't know what I'm missing. What does anyone think of the idea of EQing the 'rear' two speakers to concentrate largely on bass? Maybe this would get more out of the 12"? Wouldn't the tweater handle the 1.8kHz (and upper) range?

I think it more likely you aren't aware of what is possible to be honest. No slur on you, but I have serious reservations that a glorified HiFi speaker can produce effective LF response. They might make lots of booming sounds, and maybe even some low end that sounds passable however I doubt it's too even compared to a professional speaker. If you EQ the back speakers to largely deliver LF you will have the same issue as I mentioned above with nasty phase etc. Also you have to decide how limited the benefit is going to be. Anything much above 150Hz and you can locate where sound is coming from (it ceases to be omnidirectional). The Peavey ST12 only goes down to 80Hz, and it's not going to add much low end to the room being limited with an EQ to between 80 and 160Hz say. The HF horn does indeed handle above 1.8kHz, but because the speakers are not designed to produce low frequencies there will be little benefit in doing this.

 

 

We do have a small Behringer desk which has been doing fine for ten years, but perhaps the manufacturing happened differently back then.

Six of one half a dozen of the other. I've never met a Behringer desk that I liked and I've met several of varying ages that have done things like drop phantom power or channels mid show. Also having used the model in question you need to know that the pan knobs affect whether it goes to group 1 or group 2 for example. So you can't send a source to group 1 and group 4, this may be an issue when doing sound effects but pretty unlikely. Some people get on fine with Behringer and for the amount of use you reckon on I expect it will be fine, I just haven't had a huge amount of luck with their mixers. Sufficient that I wouldn't like to put one in my key audio channel. On the other hand you can't beat a Composer when you need a cheap compressor.

 

I'm not sure I can get any other desk with four subs for a similar price.

Nor am I. Which should say something about the quality of the desk in question. Actually Phonic probably do something as good (bad?) for similar money.

 

Just trying to get more for the money. Compare prices on thomann.de to buying from a dealer who's hauled stuff over to the college for a demo. Although a well intentioned dealer will try to offer you the best for your budget, he'll only offer products he can source and will also add a fair profit for himself.

Tis the nature of business that people want to make money. The issue with DIY audio is not unlike installing your own bathroom. The bits you can do easily will go fine, then there'll be the bits where you do less well and have to get the expert in to fix. Sometimes it's cheaper to get the expert in first time. Now fair enough you've done the right thing by asking before you buy (you no idea how irritating posts that read: "I just bought xyz is it any good?" are!) and there's a wealth of information online that can take you through the basics.

 

I like that idea. Routing speaker-level signals around the room seems more reliable though. You think that long runs of signal level cable are preferable to long runs of speaker level cable? More of the problem is that the subgroup outputs are jack, rather than balanced XLR?

I thought the outputs are balanced Jacks, and I've even downloaded the mixer for the thing to check... and they aren't. I have to admit that is a really really low place to take a few pence out a mixer. 4 balancing circuits would have cost them less than a pound to put in I reckon. Grumble grumble moan moan. Long runs of line level balanced cable are very much preferred to long lines of speaker level. The losses in a 200m line level run are tiny. 200m of speaker level will lose most of the signal into heating the cable and do nasty things to damping factors etc, even 20m of speaker cable will lose 1-2dB of level depending on the impedance of the speaker and the gauge of the wire.

 

Thanks for the attention to detail! I went and read about early and late reflections at http://www.church-acoustics.com/aa102.htm (very good.) This is a little worrying, as the new flooring is very solid (feels like rock when you touch it.) One wall has a lot of big windows with blinds, but the others are fairly bare. The ceiling has those polystyrene looking ceiling tiles. Surely these 'multipaths' go untreated in 80% of entertainment venues? Do people really notice?

Attention to detail is what it's all about. Doing a basic install can be done by anyone who knows what to plug to what and can screw a bracket into the wall. Doing a basic install that sounds ok can be done by someone with a rudimentary knowledge of the theory. Doing a good install that works well involved modelling the venue using some package like EASE or similar, and using the data from that to commission the install. That you have a lot of reflective surfaces tell me you are almost certainly going to have intelligibility issues. A lot of these can be resolved by keeping the sound off the hard surfaces directly. In order to do this with very wide dispersion speakers (such as the Peaveys) you may well end up with slightly odd looking installs with the speakers at almost 45 degrees to the walls to minimise the pattern thrown onto the wall. As to whether venues resolve the multipath issue, well that depends from venue to venue. In an ideal venue each area is only covered by one speaker, and a large number of tight dispersion cabs will be picked to make a system that fits the venue. In other venues I've seen some acoustic treatments done to reduce the issues, sometimes an inventive 'bodge' to the loudspeaker layout has been used too, I've seen removing the outer two drivers from a Bose 802 to reduce the width the speaker covered done a couple of times. But then removing the 802 would most likely have improved the sound further.

 

Early on, I did look at getting four Behringer Sharks to add delay and feedback killing. I was hoping that the 8metre delay wasn't going to be tremendously significant though. Would adding delay solve most of the problem, most of the time? I guess you're going to tell me that a good EQ will be better for the feedback killing. I just read about compression on vocals too - our students singing can vary from whispers to shouts!

Four Sharks... well they pass audio. For some reason they seem to hiss a lot generally. If you lock the filters down they'll find feedback fairly fast, but not as fast as you will with practise. Also you'll find that with the right system setup in the room your feedback issues will be majorly reduced. Reflected sound ending up back at the mic is a major cause of low gain before feedback (GBF). They would enable you to add delay to the speakers though. It would help with some issues i.e. intelligibility in the delay situ, it won't stop sound bouncing off the walls though. That's about product choice and aiming. Compression can be useful yes in the way you cite, but you can usually manage ok by pulling the fader down.

 

Yes, I'm hoping this may be a saving grace with the late reflections. Quite often, for the more audio-critical events such as spoken presentations or theatre, the room is wall to wall, shoulder to shoulder with 'sacks of water.' Maybe I can get people to hold polystyrene sheets above their heads?

Not seen that done. Seen polysheets stuck to the ceiling though. Make sure it's fireproof. Very, very fireproof.

 

Actually, we contacted two local guys who had adverts on the Yellow Pages website. The guy who specified the Behringer Truth monitor speakers was going to charge £1790 plus £410 installation. I then based my plan on much of the Behringer stuff the cheaper bloke had specified. Then I started to worry about the 9" woofers for bass. Then I started to research SPL, ohms, prices and watts, etc. And here I am.

 

OK, I'm bored, I've not got any pressing work to do for my degree (surely I should do - finals in a few weeks!) and I've got a few mins to kill... so this is my take on what I'd probably put in without having seen the venue, based on your diagram being fairly accurate. I haven't done any modelling of the room or anything, I'm doing it on experience only. With those caveats in mind also remember I'm no audio professional either, there are high end pros who have been doing this longer and better than I.

 

Rack: Rockcase £159

Mixer: Yamaha MG16/6Fx £223

CD Player: Numark CDN15 £115

Speakers: Mackie SRM350 Powered cabs £1200

Delay: Behringer Sharks x 2 £165

Sub: Mackie SWA1501 £700

 

Total: £2562 or £2180 excluding VAT.

If you skip the sub then it's £1862/£1585.

 

The SRM350 is a speaker that I've used and even bought a pair of for the society I'm on the exec of. They work fine and sound reasonable, better than most things for that money. They are only 10" drivers though which makes them underpowered for low bass, hence the recommendation of a sub.

 

If it were me I'd run stereo from the mixer to the Sub (it has L+R inputs) then come out of that into the two from SRM350, and loop out of those, via the sharks to the back SRM350s, with the option to patch in to them directly at other times if necessary. You should place the SWA1501 under one or other of the front SRM350s to avoid a time alignment issue there.

 

Well that's some food for thought. I wouldn't like to see cheaper speakers than that in the mix really though.

 

Regards

 

Chris

[mark76uk]

I haven't heard of the cable you intend to use, but a quick look on Thomann looks like the 22AWG mic cable comes up to what I'd expect. I doubt it's hugely different to the normal stuff I use which is made by VDC. How much more a reel that is I'm not sure, but probably about £15-20.

Here they are:

2 x 2.5mmSQ

http://www.thomann.de/thoiw2_cordial_cls_225_prodinfo.html

8 x 2.5mmSQ

http://www.thomann.de/thoiw2_cordial_cls_825_prodinfo.html

 

you need to know that the pan knobs affect whether it goes to group 1 or group 2 for example. So you can't send a source to group 1 and group 4, this may be an issue when doing sound effects but pretty unlikely.

I figured I could just put the L and R of the stereo into two mono channels. This way, I could pan either side of the stereo to any side of any subgroup.

 

Long runs of line level balanced cable are very much preferred to long lines of speaker level.

If I put the amps near the ceiling near the speakers, how do I join all the wires coming from the four sound-trolley-plug-in sockets? I'm guessing that joining balanced cables will cause them to lose the 'balancing' all the way back to the mixer? Similarly, if I use powered speakers, how do I feed them inputs from all four sound-trolley-plug-in sockets? I'm not willing to surrender the multiple trolley-plug-in-sockets idea, as it's the solution we need. I think I'd rather suffer the consequences of over-long amp to speaker cables.

 

Rack: Rockcase £159

I think I may choose the 16x10, for future-proofing.

 

Mixer: Yamaha MG16/6Fx £223

I think that if we're surrendering the one-subgroup-fader-per-speaker idea, I may aswell go for the Yamaha 16/4 £149.00

http://www.dolphinmusic.co.uk/page/shop/fl...product_id/4365

 

CD Player: Numark CDN15 £115

We planned to get a CDN22, for the discos. £149.00

 

Speakers: Mackie SRM350 Powered cabs £1200

I'm not sure I can justify these to myself. In a way, with those small woofers, it's taking us back down the Behringer Truth route (yes, I considered getting a sub for those too!) I may consider getting cheaper powered speakers, such as The Box from Thomann £196.65

http://www.thomann.de/thoiw2_the_box_pa502...m_prodinfo.html

 

Delay: Behringer Sharks x 2 £165

These are only £59 at Dolphin Music

http://www.dolphinmusic.co.uk/page/shop/fl...product_id/2229

 

Does anyone know if they do Feedback Killing and Delay simultaneously? Or only one function at a time?

 

Sub: Mackie SWA1501 £700

I thought of getting a sub, but it involves extra cables. I'd rather have the bass from the main speakers, up on the wall.

You should place the SWA1501 under one or other of the front SRM350s

At one side? Does this really work well?

 

Total: £2562 or £2180 excluding VAT.

If you skip the sub then it's £1862/£1585.

It's a bit much really, as I need to get lighting stuff too. Half our lighting stuff is ten years old, homemade and second hand! Worse than the sound really.

 

Working vaguely on 4x Peaveys, 2x Thomann t.amps and the Yamaha desk, I'm currenly budgeting about £1500 for sound.

 

If it were me I'd run stereo from the mixer to the Sub (it has L+R inputs) then come out of that into the two from SRM350, and loop out of those, via the sharks to the back SRM350s, with the option to patch in to them directly at other times if necessary.

As I said, I can't surrender the four sound-trolley-input-sockets as it eliminates wiring and allows other people to make use of the equipment.

 

Thanks,

Mark :)

 

Good morning,

 

Is this any better? ;) Here's my alternate wiring idea. Balanced line level signals come from each of the four sound-trolley-input-sockets and are fed to two amplifiers, on shelves above each of the 'front' speakers. I guess this is better because it has long runs of line level cable, not speaker cable?

 

Questions...

---Can I still use a single 8 pin speakon connector to plug the desk into the sound-desk-input-sockets?

---What thickness of cable does anyone suggest for the balanced line cable leading up from the sockets to the amps?

---How do I join the various balanced line signals from each of the four sockets?

 

Thanks even more,

/Mark :)

 

http://www.hinwickhall.ac.uk/external/soundandlightforum/ampsnearspeaker.gif

[nickb12345]

I may be missing something totally here so please feel free to shoot me down.

 

How about using something like the Behringer ULTRADRIVE PRO DCX2496. That way you can take your 2 mix outputs from the desk into it and then configure each speaker from there. You can set delays and eq on it, as well as limiting and volume control.

 

That way you can set up presets which other people can load for easy possible combination for the setup such as

 

Speaker outputs like this:
|-----------------------------------------|
|			 2			  4			|
|										 |
|										 |
|										 |
|			 1			  3			|
|-----------------------------------------|

With Input A as the left desk channel and B as the right channel


Preset 1: Stage at left end of room
O  EQ	DEL	INA	INB
1   X			X	   
2   X				   X
3   X	 X	  X		   Incl Volume Pad to correct level
4   X	 X			 X	Incl Volume Pad to correct level


Preset 2: In The Round production
O  EQ	DEL	INA	INB
1   X				   X
2   X			X	   
3   X			X	   
4   X				   X


Preset 3: Mono Disco
O  EQ	DEL	INA	INB
1   X			X	  X
2   X			X	  X
3   X			X	  X
4   X			X	  X


Preset 4: Stage at Right end
O  EQ	DEL	INA	INB
1   X	 X			 X	Incl Volume Pad to correct level
2   X	 X	  X		   Incl Volume Pad to correct level
3   X				   X
4   X			X

And any other presets required. Also include XOVER and limiter on all speakers if you need to. You can then lock the interface so other people can only recall the presets you have stored.

 

That way they dont have to worry about mixing 4 speakers individually and also you can use the limiter as a kind of idiot check to stop them driving the system too hard. It can be a good idea to program the system with the amps on full, that way they cant just turn the amps up to overide the limiter.

 

I think the above all makes sence, it does to my small mind!

 

With regards to speaker placement and all that dont ask me, im normally a lampie.

 

Rgds

 

Nick

 

 

Edit:

 

Also forgot to add the Behringer system has 6 outputs so you could always configure another one with a XOVER for a sub on all your presets and then if you need more bass you can hire one in and plug it in there!

 

The ULTRADRIVE PRO DCX2496 can be found here: http://www.behringer.com/DCX2496/index.cfm?lang=ENG

[mark76uk]

How about using something like the Behringer ULTRADRIVE PRO DCX2496.

 

This seems like a good idea. Thanks. I've never seen this box before. ......Taking a look!

 

/Mark

[MarkPAman]

Speakers: Mackie SRM350 Powered cabs £1200

I'm not sure I can justify these to myself. In a way, with those small woofers, it's taking us back down the Behringer Truth route

 

Sub: Mackie SWA1501 £700

I thought of getting a sub, but it involves extra cables. I'd rather have the bass from the main speakers, up on the wall.

 

Mackies will be much much better than Behringer. If you don't want to use the sub then why not go for four SRM450, the price will be almost exactly the same.(Studiospares it works out £7 cheeper)

 

I have not used the Ultradrive, but it seems like a good plan to me. I wold put it on your trolley with the desk, then four leads go to your wall boxes which are connected directly to the speakers.

 

Just had another thought! The SRM350 will take mic level in if you have a very simple event & didn't want to set up the desk at all.

 

Have fun! :)

 

Mark