~~REVERB~~
I have been asked recently,.. by quite a few people, "What is Reverb?" and "What is a Spring Reverb?"
Ok,.. first one is quite simple really. Reverb is short for REVERBERATION which is a sort of ambient echo like you get in large halls, the bathroom, an empty street, a drain-pipe etc. and is basically a short form of echo. This is the sound bouncing off a hard surface and coming back at you from a slightly different direction, also a little bit later than the original sound. There is however, very little reverb in a carpeted room or most studios for that matter and so, if you record a sound in such a "dead" space, it lacks something. (Quite a lot actually!)
If you want a more simple picture of how it works, chuck a ball hard at one wall in a room and it will usually bounce off several surfaces before it smashes that priceless cut-glass vase or a window! So I suggest you take MY word for it and definitely don't try this at home!!!
A slightly less painful way to visualise it is, to look at the way waves break on a shoreline. A wave comes in and breaks on the shore, then washes back again where that bit of water from the first wave is picked up by a second wave and comes back in again, although you'll have a hard time telling which bit of water belonged to which wave, won't you? And so it goes on, wave after wave, with each wave carrying smaller and smaller bits of the the earlier waves. Interesting thing about this particular analogy is that as the waves get bigger, the less you will notice the effect, thus, exactly the same applies to sound, the louder the original volume, the less you will notice natural reverberation which is why so many PA engineers run masses of watts to drown out the reverb they don't want or rather can't control. I tend to try and work with such reverb rather than attempt to drown it for the simple reason that this natural reverb is where that 'orrible problem of feedback comes from. (what on earth? I use feedback?? er,.. no,..) If I know that I have natural reverb, I use it to thicken up the sound rather than trying to blow it out with pure volume because even at high volume, it's still very much there, that's why you get feedback from the mics and accoustic instruments at high volumes. To control this feedback, you need the services of a decent GRAPHIC EQUALIZER which is basically a very posh tone control that splits the sound into lots of small slices of frequencies, so that you can cut or boost to reduce the frequencies at which feedback happens. If you are going to use any form of echo or reverb at a gig, you will almost certainly need to adjust the graphic again after you add any sort of delay into the sound. The more bodies (fanz) you fill a place with, with all the clothes they have on, (or not even!) the natural reverb of the place will alter and so will the feedback, in very annoying ways!
Another thing that comes from natural reverberation, is the sound of an accoustic guitar when you mic it up. Yes there are really good piezo bugs out there that will give a really nice true accoustic sound,.... but it's often slammed by classical guitarists as sounding wrong. Why? Simple reason is that the body of an accoustic guitar has a reverberation all of its own which you (and the mic) hear, but the bug, squashed into the slot under the bridge or stuck on a spot on the body, DOESN'T. If you use a bug, you will almost always have to add some form of reverb to the signal or it will sound clinical and twee. Trust me, nearly all the classical guitarists I have worked with do not like the idea,... either I don't tell them, or I use a really expensive electret mic and fight the feeback,... it's easier than trying to re-educate them about the finer points of PA!!
That's natural reverb.... So what's a spring reverb then?
I suggest you take a quick look at this next link to ACCUTRONICS (Sound Enhancement Products, Inc.) who have been the makers of spring line reverb "tanks" since dear old Hammond first spawned the idea. You'll find a short history of the spring reverb there too, which makes interesting reading so I won't duplicate it here. They still make spring-line reverbs and although there are many imitators, if you want to play with reverbs the way I am about to suggest here, get yourself a decent device to do it with, or the results WILL be less than you wanted/expected!
What a reverb unit does is to add a live feel to an otherwise dull sound. Originally developed to make electronic organs in granny's front room sound like the local cathederal, the reverb unit has also become a core component of nearly every guitar combo and PA mixer desk.
A reverb tank is a pretty odd looking thing,...
It works by sound vibrating the springs at one end,... the sound travels down the spring and is picked up at the other end, amplified and mixed back into the original. Because the sound will be refected back up the spring, (remember the waves earlier?) there will be several delayed versions of the original input before it dies away completely. Electrically, it's a speaker,... shouting at a distant mic in a rather echoey hall, this is because the sound travels quite slowly along the spring, well slower than it would in the air. One unique aspect of the spring line is that different frequencies travel at different speeds in the spring; this is almost impossible to emulate with any digital device.
The input coil is a rather more beefy thing, it is driven in the same way as a small speaker and, much like a small speaker, it vibrates the spring. (In a loudspeaker this would be the speaker cone) At the other end, the pick-up coil is very much like a magnetic pick-up on a record deck, (For those of you who only know about CDs, I can't be arsed to explain here!!) A tiny ferrite bead magnet wobbles in a coil to re-produce the original sound, at a MUCH lower level than you started with, which requires a very clean, powerful pre-amp to mix into the main signal again. When I was first playing with reverb circuits, I actually used a small deck monitor amp with about 500 milliwatts output, I used the output stage to drive the spring and having separated the pre-amp, that bit was used as the spring output amp.
If you want a louder reverb sound, you can't just chuck more power into it,... all that will do is launch the poor little coil into the next milennium! You laugh,... I've seen it done!.. 50 watts in = "PHUKT!" What you need is even more gain in the output preamp, along with tone shaping but there will be a finite limit to how far you can push that.
Spring reverb in a combo cabinet will also tend to get vibrated by the sound from the speaker. What results is a pretty unique clean delay sound. Er,.. if you put your amp on the drum riser, the spring will also be picking up the drummer,... fine if you like that sort of thing but picking up the drummer is best left to his girlfriend,.. or his mother!
Now I suppose you want some circuits to play with????
Ok,.. first one is quite simple really. Reverb is short for REVERBERATION which is a sort of ambient echo like you get in large halls, the bathroom, an empty street, a drain-pipe etc. and is basically a short form of echo. This is the sound bouncing off a hard surface and coming back at you from a slightly different direction, also a little bit later than the original sound. There is however, very little reverb in a carpeted room or most studios for that matter and so, if you record a sound in such a "dead" space, it lacks something. (Quite a lot actually!)
If you want a more simple picture of how it works, chuck a ball hard at one wall in a room and it will usually bounce off several surfaces before it smashes that priceless cut-glass vase or a window! So I suggest you take MY word for it and definitely don't try this at home!!!
A slightly less painful way to visualise it is, to look at the way waves break on a shoreline. A wave comes in and breaks on the shore, then washes back again where that bit of water from the first wave is picked up by a second wave and comes back in again, although you'll have a hard time telling which bit of water belonged to which wave, won't you? And so it goes on, wave after wave, with each wave carrying smaller and smaller bits of the the earlier waves. Interesting thing about this particular analogy is that as the waves get bigger, the less you will notice the effect, thus, exactly the same applies to sound, the louder the original volume, the less you will notice natural reverberation which is why so many PA engineers run masses of watts to drown out the reverb they don't want or rather can't control. I tend to try and work with such reverb rather than attempt to drown it for the simple reason that this natural reverb is where that 'orrible problem of feedback comes from. (what on earth? I use feedback?? er,.. no,..) If I know that I have natural reverb, I use it to thicken up the sound rather than trying to blow it out with pure volume because even at high volume, it's still very much there, that's why you get feedback from the mics and accoustic instruments at high volumes. To control this feedback, you need the services of a decent GRAPHIC EQUALIZER which is basically a very posh tone control that splits the sound into lots of small slices of frequencies, so that you can cut or boost to reduce the frequencies at which feedback happens. If you are going to use any form of echo or reverb at a gig, you will almost certainly need to adjust the graphic again after you add any sort of delay into the sound. The more bodies (fanz) you fill a place with, with all the clothes they have on, (or not even!) the natural reverb of the place will alter and so will the feedback, in very annoying ways!
Another thing that comes from natural reverberation, is the sound of an accoustic guitar when you mic it up. Yes there are really good piezo bugs out there that will give a really nice true accoustic sound,.... but it's often slammed by classical guitarists as sounding wrong. Why? Simple reason is that the body of an accoustic guitar has a reverberation all of its own which you (and the mic) hear, but the bug, squashed into the slot under the bridge or stuck on a spot on the body, DOESN'T. If you use a bug, you will almost always have to add some form of reverb to the signal or it will sound clinical and twee. Trust me, nearly all the classical guitarists I have worked with do not like the idea,... either I don't tell them, or I use a really expensive electret mic and fight the feeback,... it's easier than trying to re-educate them about the finer points of PA!!
That's natural reverb.... So what's a spring reverb then?
I suggest you take a quick look at this next link to ACCUTRONICS (Sound Enhancement Products, Inc.) who have been the makers of spring line reverb "tanks" since dear old Hammond first spawned the idea. You'll find a short history of the spring reverb there too, which makes interesting reading so I won't duplicate it here. They still make spring-line reverbs and although there are many imitators, if you want to play with reverbs the way I am about to suggest here, get yourself a decent device to do it with, or the results WILL be less than you wanted/expected!
What a reverb unit does is to add a live feel to an otherwise dull sound. Originally developed to make electronic organs in granny's front room sound like the local cathederal, the reverb unit has also become a core component of nearly every guitar combo and PA mixer desk.
A reverb tank is a pretty odd looking thing,...
It works by sound vibrating the springs at one end,... the sound travels down the spring and is picked up at the other end, amplified and mixed back into the original. Because the sound will be refected back up the spring, (remember the waves earlier?) there will be several delayed versions of the original input before it dies away completely. Electrically, it's a speaker,... shouting at a distant mic in a rather echoey hall, this is because the sound travels quite slowly along the spring, well slower than it would in the air. One unique aspect of the spring line is that different frequencies travel at different speeds in the spring; this is almost impossible to emulate with any digital device.
The input coil is a rather more beefy thing, it is driven in the same way as a small speaker and, much like a small speaker, it vibrates the spring. (In a loudspeaker this would be the speaker cone) At the other end, the pick-up coil is very much like a magnetic pick-up on a record deck, (For those of you who only know about CDs, I can't be arsed to explain here!!) A tiny ferrite bead magnet wobbles in a coil to re-produce the original sound, at a MUCH lower level than you started with, which requires a very clean, powerful pre-amp to mix into the main signal again. When I was first playing with reverb circuits, I actually used a small deck monitor amp with about 500 milliwatts output, I used the output stage to drive the spring and having separated the pre-amp, that bit was used as the spring output amp.
If you want a louder reverb sound, you can't just chuck more power into it,... all that will do is launch the poor little coil into the next milennium! You laugh,... I've seen it done!.. 50 watts in = "PHUKT!" What you need is even more gain in the output preamp, along with tone shaping but there will be a finite limit to how far you can push that.
Spring reverb in a combo cabinet will also tend to get vibrated by the sound from the speaker. What results is a pretty unique clean delay sound. Er,.. if you put your amp on the drum riser, the spring will also be picking up the drummer,... fine if you like that sort of thing but picking up the drummer is best left to his girlfriend,.. or his mother!
Now I suppose you want some circuits to play with????
To Be Continued,....
(That means Circuits!)
PB 2006
(That means Circuits!)
PB 2006