These are the specs for a range of Humminbird products.
Matrix 12 specs:
| Display Size: | 5.0" diagonal |
|---|
| Display Pixel Matrix: | 240V x 240H |
| Display Type: | FSTN LCD |
| Display Colors/Grayscale: | 12 Level Grayscale |
| Single Beam |
| Sonar Coverage | |
| Target Separation: | 2.5 inches |
| Power Output (RMS): | 250 Watts (RMS) |
| Power Output (Peak to Peak): | 2000 Watts (Peak-to-Peak) |
Humminbird 325
| Display Size: | 4.0" diagonal |
|---|
| Display Pixel Matrix: | 320V x 240H |
| Display Type: | FSTN LCD |
| Display Colors/Grayscale: | 16 Level Grayscale |
| DualBeam PLUS |
| Sonar Coverage | - 200 kHz / 20° @ -10db
- 83 kHz / 60° @ -10db
|
| Target Separation: | 2.5 inches |
| Power Output (RMS): | 300 Watts (RMS) |
| Power Output (Peak to Peak): | 2400 Watts (Peak-to-Peak) |
Humminbird 161 Combo (specs for 160 not listed on website):
| Display Pixel Matrix: | 320V x 240H |
|---|
| Display Type: | FSTN LCD |
| Display Colors/Grayscale: | 16 Level Grayscale |
| Single Beam |
| Sonar Coverage | |
| Target Separation: | 2.5 inches |
| Power Output (RMS): | 150 Watts (RMS) |
| Power Output (Peak to Peak): | 1200 Watts (Peak-to-Peak) |
PiranhaMax 220
| Display Size: | 4.0" diagonal |
|---|
| Display Pixel Matrix: | 240V x 160H |
| Display Type: | FSTN LCD |
| Display Colors/Grayscale: | 8 Level Grayscale |
| Dual Beam |
| Sonar Coverage | - 83 kHz / 60° @ -10db
- 200 kHz / 20° @ -10db
|
| Target Separation: | 2.5 inches |
| Power Output (RMS): | 200 Watts (RMS) |
| Power Output (Peak to Peak): | 1600 Watts (Peak-to-Peak |
Humminbird 787C
| Display Size: | 5.0" diagonal |
|---|
| Display Pixel Matrix: | 640V x 640H |
| Display Type: | 256 Color TFT |
| Display Colors/Grayscale: | 256 colors |
| DualBeam PLUS |
| Sonar Coverage | - 200 kHz / 20° @ -10db
- 83 kHz / 60° @ -10db
|
| Sonar Optional: | QuadraBeam PLUS |
| Target Separation: | 2.5 inches |
| Power Output (RMS): | 500 Watts (RMS) |
| Power Output (Peak to Peak): | 4000 Watts (Peak-to-Peak) |
One thing to take note of is that the target separation (sonar beam resolution) on all of them is 2.5 inches. The sonar itself can only resolve down to 2.5 inches. The differences lie in the power, number of beams and screen resolution. Power is probably the least of your concerns if you fish in <200 feet of water. As long as you have a good transducer installation, even a low power unit should get enough signal return to see the bottom. Having a dual beam unit gives you greater coverage of the water column and bottom. The higher resolution screen will allow more detail to be displayed. On a 240X240 pixel screen in 120 feet of water, each pixel is going to represent 6 inches of the water column. On a 420 pixel screen, each pixel will only be 3 inches. The higher resolution screen will allow the data that's available to be displayed more clearly and effectively.
In my opinion, you should go with the highest resolution screen that you can afford.