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Working with Sound Equipment
I have been working with sound equipment since the age of 13. My first homemade devices were vacume tube audio amplifiers. At some point, in the 70's I built the mixer shown in the picture below. Now I work for a Bible School where there are about 6 sound systems, and over 100 computers to maintain. I also travel around the world to help churches with their computers and sound systems. Hopefully I can offer some "sound" help with this web page.
These are some areas that will be covered.Microphones and Cables
Mixers
Reverb Limiters and Equailizers
Audio Amplifiers
Speakers, and Cabeling
Recording Cassettes
Recording CD's
Microphones and Cables
My favorite microphones are made by Shure. Virtually every Sure microphone lasts forever. If you do need it fixed they have all the parts available to fix it. Kingdom Tapes sells a microphone that has wires going to the head that break every few weeks. They once talked me into buying some instead of Shure microphones. The solution is to solder short extensions on the wires.
My favorite wireless microphones are made by Shure and Telex. Most churches have both a Handheld wireless and a lapel wireless microphone. Make sure all of your wireless microphones are on seperate frequencies. Cheap wireless microphones lack true diversity. That means they do not have two independent receivers so that if one receiver looses the signal the other one can pick it up. Otherwise you will have drop outs as the person speaking rotates or walks around. Another thing to look for is 9 volt battery operation. Nine Volts gives you more dynamic range than 1.5 volts. Using a bunch of "AA" cells is a pain.
When installing a sound system you will need a "Snake". That is a collection of 8 to 12 microphone cables all in one cable. Some bigger churches use as many as four 12 channel snakes, one for each corner of the stage. Usually you will need to remove all of the plugs at the mixer end to install the snake, The snake should be installed in a 1 to 2 inch metal conduit. PVC can be used and is better for installations that are in concrete. On one occasion I used 4 inch PVC and installed a snake without removing any of the plugs. A seperate conduit must be run for speakers as well as electrical power. It is best to keep them about 1 foot or more apart.
There are two types of microphone plugs and cables. The cheaper is 1/4 inch and it is used mostly for instruments. The better cables are called XLR and have 3 pins. XLR cables have two signal wires and a ground. The two signal wires are wired so that they are 180 degrees out of phase. Any hum or noise induced on one is also induced on the other. Since the mixer only looks at the difference between the two signal wires it ignores all of the hum and noise. The picture shows two 1/4 inch plugs, three xlr jacks, one xlr cable plug, and one xlr cable jack.
Mixers
My favorite mixers are made by Yamaha. I had a collection of problematic Mackie mixers. The main problem with some Mackie mixers appears to be the power supply that is hidden down inside the mixer with almost no ventilation. Adding a cooling fan helps many mixers work better and last longer. On the other hand I have seen very old Yamaha mixers still working almost as well as when they were new.
A basic mixer just mixes the inputs into the Right, Left and Monitor outputs. Bigger mixers offer what are called sub-mixes. What these are used for is grouping the inputs to make it easier to adjust a group of inputs. Typical groups are instruments, choir microphones, male vocals, female vocals, drums, etc. Each input on this type of mixer must be assigned to the Right and Left outputs or to a sub group, where it is then assigned to the outputs.
I recently rebuild a Behringer MX2442 mixer. Someone had spilled something into the controls and just about all of the slide controls had to be replaced, as well as several other controls. It was a long and difficult repair process. Next time I will pass on it unless I get the mixer for free. There is a lot more information on the repair under technical tips as well as the Digi-Key part numbers for the slide controls.
Reverb, Limiters, and Equalizers
Reverb adds the effect of having a chorus singing along with you. Thie is most helpfull when doing a solo, and sounds terrible if someone is talking, unless they want to sound like "God". Reverb used to use springs, but these days they use electronic delay lines, or even computerized memory.
Limiters are devices that try to keep the volume from changing too much. They are mostly needed on feeds to recorders and 70 volt lines to foyers, etc. Some speakers may need them but most prefer to have the ability to change their volume as they talk to help keep the audience alert.
Equalizers can be set up in one of two manners. The simplest method is to use a good microphone and turn up the sound system to where fedback starts. Then adjust the equailizer to prevent the feedback. The better method is to use a white noise generator. A precision microphone is positioned in the center of the audience and it then is fed through a frequency seperator to several VU meters. That way you can tell what frequencies are absorbed and what frequencies are too strong in a building.
Audio Amplifiers
My favorite amplifiers are made by QSC and Peavey, avoid buying cheap ones. Many manufactures will lie about the power of their amplifiers. They will say it has more power output that it really has. I have seen computer speakers rated for "100 watts" that were powered by a 9 volt 1/2 amp power supply. Watts is voltage times amperage, so the power supply was only 4.5 watts! If the amplifier was 100% efficient it could only deliver 4.5 watts! Some used to say to weigh an amplifier, the more it weighed the better it was built. That was true back in the days of linear power supplies, the transformer weight told you a lot. That is a little to primitive of a method for me. These days I would say to go by the brand names.
The amplifier that feeds the monitors must be the most durable. It will get the most abuse while it is running. This might come from someone connecting 6 speakers to it. It might also come from someone shorting out a speaker cable by jumping on it.
Some amplifiers are designed to drive what is called a 70 volt line. This arangement makes it possible to connect many speakers to the output of one amplifier like in a foyer or nursery. This is usually done by having a transformer built into the amplifier or by adding one externally. Then every speaker connected to the amplifier will also have a transformer to convert the 70 volts back into what will drive a 4 or 8 ohm speaker. Most of the speaker transformers have taps so that you can adjust the sound level at the speaker. In a nursery you may want to put a 6 postion switch so the listener can adjust the sound level.
Speakers and cabeling
My favorite speakers are made by Electro Voice. Watch out for cheap tweeters. I cannot tell you how many times I have been called to look at a sound system to discover that the speakers tweeters were blown. Yamaha makes some bad tweeters, the same goes for Peavey. Electro Voice makes killer speakers. I have seen some that were left at full blast overnight and they were still working in the morning. All the Capacitors in the crossover were blown however!
Speakers should always be connected via 14 or 12 gague stranded wire. It looks just like the wire used in extension cords. The length should be kept as short as possible because if you had 500 feet of 16 gague wire then it has 2 ohms resistance. If you have two 4 ohm speakers in parallel then you have 2 ohms of wire going to 2 ohms of speakers. That means you would loose 1/2 of your sound in the speaker wires! A rule of thumb is to keep the speaker wires under 100 feet. That may require the amplifiers to be located at the sides of the stage in a large building.
The placement of speakers is critical. They should be high enough to be above the heads of the people and far enough towards the audience to where the person speaking will almost always be behind the speakers. There are two main arrangements of speakers and both have their advantages. One is to use a cluster of speakers in the center. This is the best arrangement for a person speaking. The sound will seem to come from the person, not the speakers. However music is best reproduced from speakers on both sides of the stage. That gives the music depth and gives the effect that the musical instruments are spread out. Some churches even use both of these arrangements.
The speakers should be angled so that a perpendicular line from the center of the speaker is directed at the center of the area of audience it is supposed to reach. If the speakers are just above the listeners heads no angle may be needed. In a larger auditorium there can be two sets of speakers one for the front 20 or 30 rows and one for the back rows or balcony. In extreamily large installations like a stadium, the speakers need to be located throughout the building. Special delays are used to compensate for the speed of sound so that the sound arrives at the listener at the same time from all of the speakers.
Recording Cassettes
Kingdom Tapes has made and sold the best cassette tapes for years. If your duplicator is eating tapes, or has lots of crud on the heads, try Kingdom tapes. We have tried tapes from other companies and they will ruin the duplicators.
Telex makes the most reliable tape duplicators. I have worked on some other brands and they are not built as well. However my information may be a little out of date as it has been a few years since I have worked on any other duplicator. Duplicators copy both sides of the tape at once, and work at speeds up to 15 times faster than normal. That means a 60 minute tapes is copied in 4 minutes. If you use a rewinder you can save waiting on the duplicator to rewind the tapes. There are models that copy in stero and models with VU meters so you can see what is happening. It is best to test a tape in a tape player every few copies to make sure it is working properly.
Recording CD's
When it comes to recording CD's DO NOT BUY one of the CD recording machines. In my experience about 1/2 of the CD's made on them are worthless. Just get a computer with a CD recorder in it and use Sound Forge. That way you can record the message or music, edit it, and then record it to a CD. If you buy an overpriced direct to CD device you cannot edit it! If the recording is started too soon or the speaker speaks too long there is little you can do about it unless you use a computer.
Sound Forge has a few tricks to get it working corectly. When you select the red record button, you will need to select a second red record button to actually start recording. Before selecting the second record button, select the box marked "monitor". This will turn on the VU meters so you will know what the recording volume is. Another trick is adjusting the recording volume. Right click on the speaker on the task bar. Select "open volume controls". Select "options", "properties", and "recording". Now you will see your recording mixer. You can select what device to record from and set it's volume.
When you are done recording use "File" and "Save as" then give it a name containing todays date. Editing a message is just a matter of selecting and hitting "delete". Loading a file to edit it can take a while if it is a long message. Most CD's can hold 75 minutes but in a pinch some can hold 80 minutes of recording.
To duplicate a CD or to make more than one copy at a time you can load a computer with three CD burners and use Nero 6. You can also put four CD burners in a computer if you use a SCSI hard drive, but that may be tricky if you are not computer savy. To enable all the CD drives to burn at the same time you will have to select full Nero 6, and hold down the control key while selecting all the CD ROM drives. The feature is not documented too well in the Nero manual.
If you get the master/slave jumpers in the right order your drives will be drive D:, E:, and drive F: from top to bottom. The CD copying towers are easier to operate than a computer, if you do not have someone that can operate the computer. You can add even more CD ROM drives if you use SCSI drives, but they are not as common and can be very expensive. The picture shows a typical four CD burner computer all set up and ready to go.
A better method of copying CD's is to use a CD copier. There are WYTRON DVD-3000 and DVD-2000 copier controllers for sale on Ebay for under $100. They are last years models and do not support 16X DVD's. However they work great for CD copiers and for slower DVD copiers. This method is much easier and does not require that the user be able to operate a computer.
The problem with the CD or DVD copiers is finding a cabinet that can fit it. To make a 1 to 4 copier you need a cabinet that has room for six 5 1/4 inch drives. Then it has to have an AT type of power supply. You can figure you will need about 50 watts per drive, so you need a 250 watt power supply for the 1 to 6 copier.
There are three options available. There are the external SCSI drive cabinets that have the slots and the power supply already. They are very expen$ive. Then there were some older AT cabinets that had several 5 1/4 slots but they are hard to find. I threw out at least two of them years ago thinking there would not be any need of them in the future. The third option is to modify an AT or ATX cabinet to fit the additional 5 1/4 inch drives. The power switch will need to be moved to the back of the cabinet.
Another problem we had with the first CD duplicator we built was learning how to use it. We would put in the master CD and 4 blank CDs then press the copy button. Usually one or two CD's would not turn out. The problem was that you must wait for the drives to be ready before pressing the copy button. In fact, if all the drives are ready, it will start copying automatically.
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