- This topic has 48 replies, 11 voices, and was last updated September 8, 2011 at 12:16 am by .
-
Rig design
In this section we will look at what goes into designing a rig, and how to go about doing it. By the end of it you should hopefully have a fairly comprehensive design brief for the rig you want to build, and an idea of what it will likely cost to build. Obviously money is going to be one of the major factors in many of the decisions (unless you’re lucky enough to have unlimited funds), but there are many other factors that will make your life easier down the road if you think about them at the design stage…
Planning for a particular purpose.
The first thing you need to think about is what your rig will be used for – not in the sense of what music will be played (because a good rig design should be capable of reproducing anything well), but in the sense of how and what you will use it for. Will you be taking it outdoors using a tent and generator, or do you plan to only do indoor parties? Does it have to be easily portable, or are you building it into a venue? Will it be used for organised events or underground parties? Working out what you want to do with it now, and what you might want to do with it in future will save you a lot of time and effort later on because any need to modify for the new use will be already thought through and won’t necessitate rebuilding from scratch. To try and give you some idea of the sort of things you might take account of I’ll use the design brief for the rig we currently have (but definetly don’t do free parties with 😉 )
Quote:Likely uses: Outdoor parties and large building parties (warehouses etc). Not too worried about small indoor events. Not building for hire, so an engineer will always be present to oversee it’s use. Set up and striking of equipment needs to be quick (for doing ninja parties, and the occasional need to exit a site sharpish.)Things to take account of (in no particular order):
Outdoor venues require more acoustic power (due to the inverse square law), and need extra reinforcement in bass particularly.
Needs to be portable and quick to set up/take down. Must be able to achieve this with only 2 crew (becomes less important as we find new crew members, but keeping it achievable by as few as possible to be kept in mind).
Must fit into a single wheel base van (because twin wheel base and box vans etc require a group 7 MOT which is unneeded stress). So max packing size and weight roughly 12 cubic meters and 1350kg (size of a LWB high top transit) for all equipment (not just sound kit).
Modularity – needs to be easily reconfigurable (within reason) to take account of situation (ie if an amp failed, can the rest be easily tuned to take up the slack?) Needs to be easy to upgrade for when we have more cash to spend.
Sound – Must sound sweet (goes without saying really, but high audio quality central to the design). Keeping the sound intensity wanted for a party, but also keeping it contained so we’re not annoying people miles away (and therefore see the feds less often). High efficiency – we want to produce as much volume as we can with as little power as possible (while maintaining sound quality) – willy waving over how many watts your rig uses may impress your mates and punters, but only really shows your lack of skill as an engineer (how many engineers would be proud to say “I used 20KW to do something that can be done with 10”?)
Power requirements – outdoor rig, so generator powered. Low electrical demand important as lower power generators are less hassle to haul around the place. Preferably keep power single phase, as 3 phase genny’s are bulky and weigh lots. Multiple genny’s are a pain too, so whole system (including lighting) must be powered by no more than a 15KVA genny (so power max of 12KW, but the lower the better).
Robustness – It’ll be hauled around all the time, often to inhospitable places, and often set up when dark, so must be able to withstand the rigours of the road (and depredations of roadies) as much as possible. Easy servicing would be a bonus too and easy troubleshooting for when it stops working in the middle of a field. Looks not really important, as long as sound is good (so no need for carpeting speakers and such). Terrain likely to be rugged, so carrying handles rather than wheels (which will likely just get stuck), and individual boxes kept light enough to lift (no 30U racks with nowt but amplifiers).
Uses – predominantly DJ’s with turntables and DJ mixer, but provision for live acts desirable, so small professional mixer to be operated by the engineer a minimum requirement (mixer controls between DJ and rig desirable to avoid damage by over-excited turntable gorillas too).
That was the basic outline, and we tried to be as comprehensive as possible with what needed taking into account (grading by importance can be done later). Obviously you are probably going to miss things, and can’t plan for all eventualities you might encounter, but a solid idea of what your rig will be spending it’s time doing and some forethought given to any potential issues that may become important will save you a lot of stress in the long run.
Designing for modularity and robustness – why you should.
Irrespective of the use you are designing for, you should always put plenty of thought into both the modularity and robustness of the design – robustness means toughening the design as much as possible against everyday wear and tear and possible mishandling/misuse or accidents (all of which are not only possible, but likely to happen to a party rig). To that end it’s important to make sure everything is protected, so the design needs to include flight casing for electricals, grilles to protect speaker drivers and prevent pissed people trying to put their pint through any vent ports, minimal plugging/unplugging when setting up or taking down (the sockets on devices eventually fail from this – if you minimise it by hard wiring wherever possible in a rack you’ll extend the life of the equipment and save giving yourself some white hair tracing faults).
Modularity is also to be strived for as much as possible because there is no way to predict for a certainty what is going to happen in the future – making the design modular will help enormously if you find a new use you hadn’t considered at the start because it allows for some redesign by changing how the various modules connect, and allows for the insertion of new modules (as an example, in our design brief we originally dismissed the notion of small indoor venues, but later discovered that it would be useful. Owing to the modular design, we were able to reconfigure by adding a module and taking some out to allow this possibility).Efficient use of time – what to design and build yourself, and what to buy ready made.
It is possible to build an entire system by gathering the components and building everything yourself – none of the electrical equipment is outrageously complicated in design, and even speaker drivers are constructable from their component parts if you are keen. For most of us though, it is useful to work out what has to be bought and what can be built – this doesn’t necessarily come down purely to a question of funds available, because it’s sometimes easier to achieve the design goals by building rather than buying even if the components used to build cost more than the ready built item would.
My advice on this is to buy everything pre-made apart from the speaker cabinets and the cabling. The speaker cabinets because that is the area of the overall system that is by far the least efficient, and large gains in overall efficiency can be had by devoting attention to designing and building them yourself. Cabling because it’s relatively easy to make, the components cost far less than pre-built, and making them yourself allows you to build custom cables for particular jobs (plus as long as you keep some components in your toolkit, you’ll never have to desperately hunt to try and find a replacement for the one you left on the kitchen table – you can just make another.) Flight casing is also relatively easy to build, and custom made cases can help make it modular, but I don’t tend to do this myself as pre-built cases cost about the same as the components required for building and are easy to modify to requirements (the one exception to this is the flightcase for our turntables which was custom built).
Design flowchart, and how to estimate build cost and time.
- 1. Arrange your list of things to take account of in order of importance, and split them into the categories Essential, Desirable, and Useful.
2. List all the parts you already have that could be useful.
3. Use list 1 to make design decisions – try to use the simplest method you can to solve the essentials first, then the desirable and finally the useful.
4. Now list all the components necessary to those solutions, including the ones you already have. Don’t forget things like cabling, or wood, glue, screws etc if you intend to build speakers.
5. Research all the possibilities you can come up with for the components, and ask opinions etc (places like PV, or the usenet group rec.audio.pro are useful for this).
6. Find prices for the equipment (if buying second hand from ebay or the like, use the average auction sale price rather than the lowest you can find). Download and read the manuals for any equipment you consider so you know exactly what cabling will be required, and how many units of a rack it takes up etc.
7. Add up the equipment cost (use zero for stuff you already have), and (most likely) gasp at the size of the number you arrive at.
8. Now it’s time for the compromises – the aim is to reduce that huge number in 7 to the amount you actually have to spend – there may be things you can live without altogether, or cheaper alternatives to essential items that will do the job.
9. Build time is more difficult – if it’s simply wiring the boxes together into flightcases it can be done in a matter of hours, and the time is going to depend mostly on how long it takes to acquire the component parts. If you are building speakers, allow up to a week for each pair. This should give a rough estimate of how long it will take.
Again, to attempt to make this process clearer I will use our real world example:
Quote:1. Essential
Sound quality must be good.
Portable and able to fit single wheel base van.
Quick to erect/un-erect.
Sound intensity must be high enough for the great outdoors.
Mixer between DJ and amplification boxes for engineer use.
Modularity.
Robustness.Desirable.
Easy upgrade potential.
Plenty of bass reinforcement for outdoors.
Power requirements within reach of single phase generator.Useful.
No requirement for multiple generators.
Keeping required crew to a minimum.
Easy servicing and troubleshooting.2. Equipment already owned:
Decks and DJ mixer in flightcase.
1 X Peavey M2600 power amp (260W RMS @ 4ohm)
2 X 18″ Black widow speaker drivers (400W RMS each).3. Design decisions.
The first thing I noticed was that several of the requirements could be addressed by raising the efficiency as much as possible (portability, packed size, speed of erection, sound intensity, bass reinforcement and power requirements would all benefit from more efficiency.)
The second thing was that designing in modularity would help with the packing, upgrade potential, service and troubleshooting and numbers of crew needed.The efficiency was a relatively easy problem, and only required the extra workload that comes with designing and building speakers. Making the whole system active (with respect to the crossover matrices) would further enhance the efficiency.
Designing speaker cabinets to each take only 1 driver type would help both efficiency and modularity over multiple driver type designs, and several small flightcases for amps, crossover etc would allow for some more modularity.
Using ported radiator designs for all cabinets other than highs would help with both the size issues and the set up speed – I’m less than convinced of the benefit of folded bass designs for anything other than large scale PA, where the longer throw is useful to cover the extra distance. In small scale (ie smaller than stadium size) a radiator produces more output into the nearfield than any horn design I’ve heard. Ported radiators also have the benefit of being smaller, easier to build and importantly much easier to set up than folded horns or scoop bins. The only place a horn flare is worthwhile IMO is with a high frequency compression driver where the exponential flare can cause the acoustic transformer effect and result in a large increase in volume. This benefit outweighs the extra time required to align them properly during set up.
Designing the mid range cabinets so they can effectively reproduce bass wouldn’t adversely affect their mid range performance, but would allow for more options in terms of modular configurations.
Designing and building the cabinets myself allows me to effectively over engineer all the joint fixings and material strength resulting in a much more robust speaker system.
Using a 3 way stereo crossover that could be run as a 4 way mono one would allow plenty of room for a future upgrade by way of getting another of the same crossover and using both in 4 way.
A pair of 10U racks would allow modular use by splitting up amps while at the same time ensuring the boxes don’t become too heavy to carry easily. External sockets on the racks would deal with necessary connections between them, and hard wiring speaker cables, input feed, and internal connections would allow them to pack into the cases and remove the need to constantly plug/unplug all connections.
Components
So from those solutions we knew our system needed to be 3 or more way active (preferably with upgrade potential via other modes), would require at least 3 amplifiers, and at least 2 10U racks. In addition we would require at least 3 speaker pairs of varying size, and enough wood to build the final speaker designs, and a mixer for the engineer. We already had a pair of 18″ drivers, decks, dj mixer and flightcase, and a 260W amplifier.The component list minimum was:
2 X HF compression drivers with bolt on horn flare for each
2 X Mid range drivers (we decided on 12″ drivers which would be capable of bass reproduction if wanted).
2 X Bass drivers (Fane colossus would be preferred, but the black widows were already paid for)4 sheets 8 X 4 marine ply (1/2″ thick)
1 giant bottle of glue
1 big box of 1″ screws
8 lengths 1″ X 1″ beading for internal strength
2 feet 4″ bore plastic pipe (for port tubes)
2 X 12″ speaker grilles
2 X 18″ speaker grilles1 X 3 way crossover (with option for more ways in mono)
1 X Compressor for use as a level limiter to protect the amps/speakers1 X amplifier to drive the compression drivers (the M2600 seemed perfect)
1 X mid amplifier
1 X Bass amplifier2 X 10U flightcases (wood with metal edging/corners rather than ABS plastic)
1 X engineers mixer with flightcase
100m 3 core mains flex (min 16A power rating) for speaker cable and mains power inputs
100m good quality PVC sheathed mic/signal cable for all other cabling purposes
Connectors – at least 12 XLR female, 12 XLR male, 10 TRS 1/4″ jack, 8 speakon sockets, 4 XLR female sockets and 14 4 way speakon plugsAfter my research I added my list of prices together, gasped (it came to over £6000, and I only had £1500), then sat down to work on those compromises. I ended up striking the compressor from the list as I found a crossover that had built in limiters (and was about 1/4 the price of my original choice). I picked up a good 2nd hand amp for the mid for £100, and got what I thought at the time was an excellent deal on a Yamaha CP2000 for the bass (£400). A pair of Eminence gamma 12’s, and a pair of 2″ DAS compression drivers with horn flares set me back another £200, the crossover £60, 2 10U flightcases cost me £140, and a second hand Soundcraft 400B in full flightcase was a steal at £190. That left me £400 for the speaker materials, cabling and connectors which was easily manageable.
So I’d sourced all the necessary components and managed not to require sacrificing any of the desirable or useful wishes on my list – it wasn’t my perfect system but it’d do the job. I estimated 3 weeks build time (and having had plenty of speaker building experience beforehand got it pretty much right). It sounded good, and was very efficient – under 2KW of power being used, and it was acceptable for outdoor use, could be set up in about 1/2 an hour and packed as quickly, and was solid enough to stand the rigours of road use.
The built in upgrade potential was useful too, because a year later a little carelessness resulted in one of the black widows and one side of the CP2000 being totally fried (I still have the CP2000, and will fix it as soon as I can source the parts). At the time I had some cash to spare (about £1200 or so), and decided to go 4 way as well as using my preferred bass drivers (18″ Fane colossus). I replaced the CP2000 with a pair of Peavey CS800’s running bridge mono, and built a pair of 15″ low mids using a pair of Fane 15B’s. Power use went up to about 3KW which was OK as it sounded like a rig several times that size. The current incarnation has been upgraded again (I got another pair of 18″ colossus and built the twin driver cabs I’d been choking to try out which have been every bit as good as I hoped they would be), and power use is now around the 4KW mark (with bass output heavy enough that the vibrations distort your eyesight anywhere within about 30 feet 😀 )
Your own list may be very different to the example here, and your solutions too. If you put plenty of thought into it though, and try to make your solutions cover or help as many of your list points as you can then you won’t go far wrong, and should end up with a useful design.
Power – working out the requirements, and working within safe limits.
Power is always going to be a limiting factor in any rig design – and it’s important to have some idea of how to calculate the requirements. The most power hungry devices are always going to be the amplifiers – they have a published power rating expressed as an average over a set time period (the RMS power rating). However, the power draw may be much more than that average, such that it becomes prudent to at least double the RMS rating when calculating power requirements – so rig using 4KW RMS amp power would require an 8KW supply – many people will tell you it’s possible to run on much less, and that’s true providing you don’t mind reducing the lifespan of your equipment and can live with the occasional blown driver or amp. If you’d like them to last I’d recommend powering them properly. You also need to account for any lighting, turntables, mixers processing etc etc in this calculation – most devices will have a power draw rating listed in their specs which you can add on to your doubled amp RMS value. I’ll go into this in more depth in the last part of this guide on rig power.
Matching amplifiers with speakers properly.
There are many opinions as regards matching amp to speaker power – some say one should be lower than the other, usually giving some quasi-scientific waffle as justification. The best advice and reasoning I have found is contained in one or two of Peavey’s tech notes, and specifically the “How much power” PDF document. Basically it boils down to matching the speakers program power handling value to an amps RMS output value (so an amp that outputs 400W RMS @ 8 ohm should be matched with a driver that is rated for 400W program power and 8 ohm.)
Under powering a speaker is probably slightly safer than over powering (after all, it’s more likely to drive beyond safe limits with an amp that is too powerful), but not by much because there is a tendency to try and drive underpowered drivers harder resulting in overdriving and distorting the signal (which is also very bad for a speaker)…
Linking it all together.
Once you have all your components, the next thing is to make a schematic drawing of the whole system, what connects to what, and which connector type is needed to make those connections. It will hopefully look something like this:
This can then be referred to if you are making your own cables to buy connectors, or if buying cables what type of cable you need for each connection, and can be used later on during the build process. Obviously your signal diagram will be specific to your set up, but you should try to keep it as clear, concise and uncluttered as possible – adding only necessary information (cable lengths would be useful additions for instance, whereas pin assignments for connectors can be noted elsewhere). If you’re hardwiring into flight cases, and using sockets to connect the cases together include it in the diagram. Another diagram detailing the power inputs and distribution within the cases would be useful, including peak power draw values and connector or distribution board types – allowing you to ensure the power system is robust enough to cope with the loads it’s carrying without spontaneously combusting…
Once all this is sorted, you’re ready to build (which will be the subject of the next section)…
Rig design
In this section we will look at what goes into designing a rig, and how to go about doing it. By the end of it you should hopefully have a fairly comprehensive design brief for the rig you want to build, and an idea of what it will likely cost to build. Obviously money is going to be one of the major factors in many of the decisions (unless you’re lucky enough to have unlimited funds), but there are many other factors that will make your life easier down the road if you think about them at the design stage…
Planning for a particular purpose.
The first thing you need to think about is what your rig will be used for – not in the sense of what music will be played (because a good rig design should be capable of reproducing anything well), but in the sense of how and what you will use it for. Will you be taking it outdoors using a tent and generator, or do you plan to only do indoor parties? Does it have to be easily portable, or are you building it into a venue? Will it be used for organised events or underground parties? Working out what you want to do with it now, and what you might want to do with it in future will save you a lot of time and effort later on because any need to modify for the new use will be already thought through and won’t necessitate rebuilding from scratch. To try and give you some idea of the sort of things you might take account of I’ll use the design brief for the rig we currently have (but definetly don’t do free parties with 😉 )
Quote:Likely uses: Outdoor parties and large building parties (warehouses etc). Not too worried about small indoor events. Not building for hire, so an engineer will always be present to oversee it’s use. Set up and striking of equipment needs to be quick (for doing ninja parties, and the occasional need to exit a site sharpish.)Things to take account of (in no particular order):
Outdoor venues require more acoustic power (due to the inverse square law), and need extra reinforcement in bass particularly.
Needs to be portable and quick to set up/take down. Must be able to achieve this with only 2 crew (becomes less important as we find new crew members, but keeping it achievable by as few as possible to be kept in mind).
Must fit into a single wheel base van (because twin wheel base and box vans etc require a group 7 MOT which is unneeded stress). So max packing size and weight roughly 12 cubic meters and 1350kg (size of a LWB high top transit) for all equipment (not just sound kit).
Modularity – needs to be easily reconfigurable (within reason) to take account of situation (ie if an amp failed, can the rest be easily tuned to take up the slack?) Needs to be easy to upgrade for when we have more cash to spend.
Sound – Must sound sweet (goes without saying really, but high audio quality central to the design). Keeping the sound intensity wanted for a party, but also keeping it contained so we’re not annoying people miles away (and therefore see the feds less often). High efficiency – we want to produce as much volume as we can with as little power as possible (while maintaining sound quality) – willy waving over how many watts your rig uses may impress your mates and punters, but only really shows your lack of skill as an engineer (how many engineers would be proud to say “I used 20KW to do something that can be done with 10”?)
Power requirements – outdoor rig, so generator powered. Low electrical demand important as lower power generators are less hassle to haul around the place. Preferably keep power single phase, as 3 phase genny’s are bulky and weigh lots. Multiple genny’s are a pain too, so whole system (including lighting) must be powered by no more than a 15KVA genny (so power max of 12KW, but the lower the better).
Robustness – It’ll be hauled around all the time, often to inhospitable places, and often set up when dark, so must be able to withstand the rigours of the road (and depredations of roadies) as much as possible. Easy servicing would be a bonus too and easy troubleshooting for when it stops working in the middle of a field. Looks not really important, as long as sound is good (so no need for carpeting speakers and such). Terrain likely to be rugged, so carrying handles rather than wheels (which will likely just get stuck), and individual boxes kept light enough to lift (no 30U racks with nowt but amplifiers).
Uses – predominantly DJ’s with turntables and DJ mixer, but provision for live acts desirable, so small professional mixer to be operated by the engineer a minimum requirement (mixer controls between DJ and rig desirable to avoid damage by over-excited turntable gorillas too).
That was the basic outline, and we tried to be as comprehensive as possible with what needed taking into account (grading by importance can be done later). Obviously you are probably going to miss things, and can’t plan for all eventualities you might encounter, but a solid idea of what your rig will be spending it’s time doing and some forethought given to any potential issues that may become important will save you a lot of stress in the long run.
Designing for modularity and robustness – why you should.
Irrespective of the use you are designing for, you should always put plenty of thought into both the modularity and robustness of the design – robustness means toughening the design as much as possible against everyday wear and tear and possible mishandling/misuse or accidents (all of which are not only possible, but likely to happen to a party rig). To that end it’s important to make sure everything is protected, so the design needs to include flight casing for electricals, grilles to protect speaker drivers and prevent pissed people trying to put their pint through any vent ports, minimal plugging/unplugging when setting up or taking down (the sockets on devices eventually fail from this – if you minimise it by hard wiring wherever possible in a rack you’ll extend the life of the equipment and save giving yourself some white hair tracing faults).
Modularity is also to be strived for as much as possible because there is no way to predict for a certainty what is going to happen in the future – making the design modular will help enormously if you find a new use you hadn’t considered at the start because it allows for some redesign by changing how the various modules connect, and allows for the insertion of new modules (as an example, in our design brief we originally dismissed the notion of small indoor venues, but later discovered that it would be useful. Owing to the modular design, we were able to reconfigure by adding a module and taking some out to allow this possibility).Efficient use of time – what to design and build yourself, and what to buy ready made.
It is possible to build an entire system by gathering the components and building everything yourself – none of the electrical equipment is outrageously complicated in design, and even speaker drivers are constructable from their component parts if you are keen. For most of us though, it is useful to work out what has to be bought and what can be built – this doesn’t necessarily come down purely to a question of funds available, because it’s sometimes easier to achieve the design goals by building rather than buying even if the components used to build cost more than the ready built item would.
My advice on this is to buy everything pre-made apart from the speaker cabinets and the cabling. The speaker cabinets because that is the area of the overall system that is by far the least efficient, and large gains in overall efficiency can be had by devoting attention to designing and building them yourself. Cabling because it’s relatively easy to make, the components cost far less than pre-built, and making them yourself allows you to build custom cables for particular jobs (plus as long as you keep some components in your toolkit, you’ll never have to desperately hunt to try and find a replacement for the one you left on the kitchen table – you can just make another.) Flight casing is also relatively easy to build, and custom made cases can help make it modular, but I don’t tend to do this myself as pre-built cases cost about the same as the components required for building and are easy to modify to requirements (the one exception to this is the flightcase for our turntables which was custom built).
Design flowchart, and how to estimate build cost and time.
- 1. Arrange your list of things to take account of in order of importance, and split them into the categories Essential, Desirable, and Useful.
2. List all the parts you already have that could be useful.
3. Use list 1 to make design decisions – try to use the simplest method you can to solve the essentials first, then the desirable and finally the useful.
4. Now list all the components necessary to those solutions, including the ones you already have. Don’t forget things like cabling, or wood, glue, screws etc if you intend to build speakers.
5. Research all the possibilities you can come up with for the components, and ask opinions etc (places like PV, or the usenet group rec.audio.pro are useful for this).
6. Find prices for the equipment (if buying second hand from ebay or the like, use the average auction sale price rather than the lowest you can find). Download and read the manuals for any equipment you consider so you know exactly what cabling will be required, and how many units of a rack it takes up etc.
7. Add up the equipment cost (use zero for stuff you already have), and (most likely) gasp at the size of the number you arrive at.
8. Now it’s time for the compromises – the aim is to reduce that huge number in 7 to the amount you actually have to spend – there may be things you can live without altogether, or cheaper alternatives to essential items that will do the job.
9. Build time is more difficult – if it’s simply wiring the boxes together into flightcases it can be done in a matter of hours, and the time is going to depend mostly on how long it takes to acquire the component parts. If you are building speakers, allow up to a week for each pair. This should give a rough estimate of how long it will take.
Again, to attempt to make this process clearer I will use our real world example:
Quote:1. Essential
Sound quality must be good.
Portable and able to fit single wheel base van.
Quick to erect/un-erect.
Sound intensity must be high enough for the great outdoors.
Mixer between DJ and amplification boxes for engineer use.
Modularity.
Robustness.Desirable.
Easy upgrade potential.
Plenty of bass reinforcement for outdoors.
Power requirements within reach of single phase generator.Useful.
No requirement for multiple generators.
Keeping required crew to a minimum.
Easy servicing and troubleshooting.2. Equipment already owned:
Decks and DJ mixer in flightcase.
1 X Peavey M2600 power amp (260W RMS @ 4ohm)
2 X 18″ Black widow speaker drivers (400W RMS each).3. Design decisions.
The first thing I noticed was that several of the requirements could be addressed by raising the efficiency as much as possible (portability, packed size, speed of erection, sound intensity, bass reinforcement and power requirements would all benefit from more efficiency.)
The second thing was that designing in modularity would help with the packing, upgrade potential, service and troubleshooting and numbers of crew needed.The efficiency was a relatively easy problem, and only required the extra workload that comes with designing and building speakers. Making the whole system active (with respect to the crossover matrices) would further enhance the efficiency.
Designing speaker cabinets to each take only 1 driver type would help both efficiency and modularity over multiple driver type designs, and several small flightcases for amps, crossover etc would allow for some more modularity.
Using ported radiator designs for all cabinets other than highs would help with both the size issues and the set up speed – I’m less than convinced of the benefit of folded bass designs for anything other than large scale PA, where the longer throw is useful to cover the extra distance. In small scale (ie smaller than stadium size) a radiator produces more output into the nearfield than any horn design I’ve heard. Ported radiators also have the benefit of being smaller, easier to build and importantly much easier to set up than folded horns or scoop bins. The only place a horn flare is worthwhile IMO is with a high frequency compression driver where the exponential flare can cause the acoustic transformer effect and result in a large increase in volume. This benefit outweighs the extra time required to align them properly during set up.
Designing the mid range cabinets so they can effectively reproduce bass wouldn’t adversely affect their mid range performance, but would allow for more options in terms of modular configurations.
Designing and building the cabinets myself allows me to effectively over engineer all the joint fixings and material strength resulting in a much more robust speaker system.
Using a 3 way stereo crossover that could be run as a 4 way mono one would allow plenty of room for a future upgrade by way of getting another of the same crossover and using both in 4 way.
A pair of 10U racks would allow modular use by splitting up amps while at the same time ensuring the boxes don’t become too heavy to carry easily. External sockets on the racks would deal with necessary connections between them, and hard wiring speaker cables, input feed, and internal connections would allow them to pack into the cases and remove the need to constantly plug/unplug all connections.
Components
So from those solutions we knew our system needed to be 3 or more way active (preferably with upgrade potential via other modes), would require at least 3 amplifiers, and at least 2 10U racks. In addition we would require at least 3 speaker pairs of varying size, and enough wood to build the final speaker designs, and a mixer for the engineer. We already had a pair of 18″ drivers, decks, dj mixer and flightcase, and a 260W amplifier.The component list minimum was:
2 X HF compression drivers with bolt on horn flare for each
2 X Mid range drivers (we decided on 12″ drivers which would be capable of bass reproduction if wanted).
2 X Bass drivers (Fane colossus would be preferred, but the black widows were already paid for)4 sheets 8 X 4 marine ply (1/2″ thick)
1 giant bottle of glue
1 big box of 1″ screws
8 lengths 1″ X 1″ beading for internal strength
2 feet 4″ bore plastic pipe (for port tubes)
2 X 12″ speaker grilles
2 X 18″ speaker grilles1 X 3 way crossover (with option for more ways in mono)
1 X Compressor for use as a level limiter to protect the amps/speakers1 X amplifier to drive the compression drivers (the M2600 seemed perfect)
1 X mid amplifier
1 X Bass amplifier2 X 10U flightcases (wood with metal edging/corners rather than ABS plastic)
1 X engineers mixer with flightcase
100m 3 core mains flex (min 16A power rating) for speaker cable and mains power inputs
100m good quality PVC sheathed mic/signal cable for all other cabling purposes
Connectors – at least 12 XLR female, 12 XLR male, 10 TRS 1/4″ jack, 8 speakon sockets, 4 XLR female sockets and 14 4 way speakon plugsAfter my research I added my list of prices together, gasped (it came to over £6000, and I only had £1500), then sat down to work on those compromises. I ended up striking the compressor from the list as I found a crossover that had built in limiters (and was about 1/4 the price of my original choice). I picked up a good 2nd hand amp for the mid for £100, and got what I thought at the time was an excellent deal on a Yamaha CP2000 for the bass (£400). A pair of Eminence gamma 12’s, and a pair of 2″ DAS compression drivers with horn flares set me back another £200, the crossover £60, 2 10U flightcases cost me £140, and a second hand Soundcraft 400B in full flightcase was a steal at £190. That left me £400 for the speaker materials, cabling and connectors which was easily manageable.
So I’d sourced all the necessary components and managed not to require sacrificing any of the desirable or useful wishes on my list – it wasn’t my perfect system but it’d do the job. I estimated 3 weeks build time (and having had plenty of speaker building experience beforehand got it pretty much right). It sounded good, and was very efficient – under 2KW of power being used, and it was acceptable for outdoor use, could be set up in about 1/2 an hour and packed as quickly, and was solid enough to stand the rigours of road use.
The built in upgrade potential was useful too, because a year later a little carelessness resulted in one of the black widows and one side of the CP2000 being totally fried (I still have the CP2000, and will fix it as soon as I can source the parts). At the time I had some cash to spare (about £1200 or so), and decided to go 4 way as well as using my preferred bass drivers (18″ Fane colossus). I replaced the CP2000 with a pair of Peavey CS800’s running bridge mono, and built a pair of 15″ low mids using a pair of Fane 15B’s. Power use went up to about 3KW which was OK as it sounded like a rig several times that size. The current incarnation has been upgraded again (I got another pair of 18″ colossus and built the twin driver cabs I’d been choking to try out which have been every bit as good as I hoped they would be), and power use is now around the 4KW mark (with bass output heavy enough that the vibrations distort your eyesight anywhere within about 30 feet 😀 )
Your own list may be very different to the example here, and your solutions too. If you put plenty of thought into it though, and try to make your solutions cover or help as many of your list points as you can then you won’t go far wrong, and should end up with a useful design.
Power – working out the requirements, and working within safe limits.
Power is always going to be a limiting factor in any rig design – and it’s important to have some idea of how to calculate the requirements. The most power hungry devices are always going to be the amplifiers – they have a published power rating expressed as an average over a set time period (the RMS power rating). However, the power draw may be much more than that average, such that it becomes prudent to at least double the RMS rating when calculating power requirements – so rig using 4KW RMS amp power would require an 8KW supply – many people will tell you it’s possible to run on much less, and that’s true providing you don’t mind reducing the lifespan of your equipment and can live with the occasional blown driver or amp. If you’d like them to last I’d recommend powering them properly. You also need to account for any lighting, turntables, mixers processing etc etc in this calculation – most devices will have a power draw rating listed in their specs which you can add on to your doubled amp RMS value. I’ll go into this in more depth in the last part of this guide on rig power.
Matching amplifiers with speakers properly.
There are many opinions as regards matching amp to speaker power – some say one should be lower than the other, usually giving some quasi-scientific waffle as justification. The best advice and reasoning I have found is contained in one or two of Peavey’s tech notes, and specifically the “How much power” PDF document. Basically it boils down to matching the speakers program power handling value to an amps RMS output value (so an amp that outputs 400W RMS @ 8 ohm should be matched with a driver that is rated for 400W program power and 8 ohm.)
Under powering a speaker is probably slightly safer than over powering (after all, it’s more likely to drive beyond safe limits with an amp that is too powerful), but not by much because there is a tendency to try and drive underpowered drivers harder resulting in overdriving and distorting the signal (which is also very bad for a speaker)…
Linking it all together.
Once you have all your components, the next thing is to make a schematic drawing of the whole system, what connects to what, and which connector type is needed to make those connections. It will hopefully look something like this:
This can then be referred to if you are making your own cables to buy connectors, or if buying cables what type of cable you need for each connection, and can be used later on during the build process. Obviously your signal diagram will be specific to your set up, but you should try to keep it as clear, concise and uncluttered as possible – adding only necessary information (cable lengths would be useful additions for instance, whereas pin assignments for connectors can be noted elsewhere). If you’re hardwiring into flight cases, and using sockets to connect the cases together include it in the diagram. Another diagram detailing the power inputs and distribution within the cases would be useful, including peak power draw values and connector or distribution board types – allowing you to ensure the power system is robust enough to cope with the loads it’s carrying without spontaneously combusting…
Once all this is sorted, you’re ready to build (which will be the subject of the next section)…
- 1. Arrange your list of things to take account of in order of importance, and split them into the categories Essential, Desirable, and Useful.
- You must be logged in to reply to this topic.