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About the reverb
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The reverb is the most complicated effect in the GSP-2101 with many parameters, which are hard to understand, if you don't know how a reverb is "generated".



The reverb bases on the sonic speed and reflections on the walls of the room, where the sound is generated.How the reverb sounds depends on the position of the sound source and the listener/microphone in the room, the size and form of the room and the material of the reflecting walls.

The first thing to be heard is the direct sound of the sound source. After that the early reflections occure. That is a cluster of direct reflections from the closest walls. Since the sound is reflected over and over again a so called reverberant tail occures at the end of the reverb sound. Here the reflections are too close, so that you can't distinguish between the reflections.


Apparently the quality of the reflections depend on the material of the walls. A tiled room has another reverb than a room with carpets on the wall. That's a matter of the different attenuations. A "hard" wall attenuates the reflections less than a "soft" wall. Also the the attenuation isn't constant over the sound spectrum. Higher frequencies are usually attenuated more than lower frequencies.

Since the MFX-Reverb is a comparatively small fx-module, it is used in most factory and user algorithms. However there are still a couple of parameters to be set up, which can be confusing to the GSP beginner. Here are some basic settings that can be used in user programs.

Setting

PreDly

Spread

Diffsn

HFDecay

Roloff

Size

RT60

Level

Short Plate

10ms

70ms

7

10000

16000

6

2.10s

25

Cool Plate

86ms

70ms

5

16000

10000

8

2.40s

25

Medium Room

35ms

30ms

1

6300Hz

16000

3

1.05s

18

Room Ambient

20ms

20ms

8

5000Hz

16000

2

0.36s

25

Large Room

50ms

30ms

1

6300Hz

16000

5

1.50s

25

Soft Ambient

4ms

40ms

9

6300Hz

8000Hz

5

0.50s

25

Orchest. Room

42ms

40ms

6

16000

16000

7

1.26s

25

Piano Hall

40ms

50ms

4

4000Hz

8000Hz

7

2.45s

20

Small Hall

40ms

40ms

2

5000Hz

6300Hz

6

2.10

25

Large Hall

80ms

60ms

9

8000Hz

4000Hz

7

3.15s

20

Cathedral

50ms

70ms

2

5000Hz

16000

10

4.00s

25

Long Cave

100ms

100ms

2

5000Hz

12500

9

4.05s

20

IMHO, the explanation of the parameters in the manual isn't really good. To estimate the parameters, you should keep in mind that the sound requires about 3ms to travel a distance of one meter (2.7ms per yard).



The pre-delay (PreDly) is the time between the direct sound and the early reflections. It depends on the shape and size of the room and the placement of the sound source. A big and wide room has a higher pre-delay that a small and narrow room. The distance the reflected waves ahev to travel before they reach the ear is greater than that the direct sound has to travel. A long narrow room wouldn't have a long pre-delay either.



The spread is a measure for the consistency of the early reflections. Low settings result in a dense cluster of early reflections, high settings will produce wider spreaded early reflections. Large rooms have a higher spread than small rooms.



The diffusion (diffsn) controls the smoothness of the reverb. Low settings produce grainy and bursty early reflections and reverb. The diffusion depends on the size of the room and the softness of the walls. A big room or soft walls will require higher setting for the diffusion. The diffusion is caused by the air and the material of the walls, it can also depend on the temperature and the humidity.



High frequencies will decay faster than meduim frequencies. The HFDecay emulates that fact. The roll off frequency (Roloff) is kinda high cut frequency. Frequencies higher than it will roll off rapidly. Both parameters depends on the material of the walls and of the size of the room. E.g. a carpet results in lower values for both parameters.



The size of the room is a pretty obvious parameter and doesn't require any further explanation.



RT60 is the duration of the reverb. A large room with hard walls results in higher values for RT60.



The best way to adjust the parameters is the switch off all other effects and to play percussive sounds on the guitar like picking a muted string. This way you hear the changes of reverb best.

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Last modified on Friday, 2. January 2009