Rumble Bass 200 Adequate?

[borgward]

Several buddies here use the Rumble 200 for ALL their gigging needs. One guy is in an 80s metal band doing Slayer, Megadeth, Metallica. The 200 is great. And will probably be fine for your 2nd band.

Sound is not measured in watts. It is measured in Decibels. I personally don't use watts as a measuring stick for rigs. My current main rig is 110 watts. It is easily twice as loud as my backup rig, which is 250 watts. I can carry any room with my 110 watt rig. And have used it extensively in many situations, both indoor and outdoor.

So I can understand what are the specs for each amp what ohms? specs for cabs, speaker size, how many, what ohms?

 

[agedhorse]

So I can understand what are the specs for each amp what ohms? specs for cabs, speaker size, how many, what ohms?

Time for you to do some research on what the specs actually mean. There's not a single line or even single paragraph answer.

 

[borgward]

Guessing that for a given wattage decibels are determined more by speaker and cabinet. I am not an electrician so what specs really mean is beyond me.

 

[agedhorse]

Guessing that for a given wattage decibels are determined more by speaker and cabinet. I am not an electrician so what specs really mean is beyond me.

They are determined equally by the power and the speaker sensitivity. They can't be separated.

 

[Wasnex]

Guessing that for a given wattage decibels are determined more by speaker and cabinet. I am not an electrician so what specs really mean is beyond me.

Hopefully this will help you along your journey.

The spec you are looking for is the cab's sensitivity rating, which is normally expressed as the decibels measured at one 1 meter from the cone with 1 Watt applied.

For example you might see:

Sensitivity = 97dB 1W/1m.

This means 1W is applied and 97dB is measured at 1m.

When you double the power the SPL goes up +3dB

Here is the sequence:
1W = Sensitivity Rating
2W = Sensitivity +3dB
4W = Sensitivity +6dB
8W = Sensitivity +9dB
etc.

So you can count the number of times the power is doubled and then multiply by 3 to get the decibel change.

For example (count the doublings):
1,2,4,8.

At 8W the power has been doubled 3 times from 1W.

3 x 3 = 9dB

You can add this figure to the sensitivity rating to estimate the max SPL.

So if the sensitivity is 97dB 1W/1m and the amp is putting out 8W, you get

97 + 9 = 106dB

You can also calculate the decibel change with the log function on your calculator. If you are starting with 1W you can use a simplified formula:

Decibel change = [Log(Power) x 10]

For example:
[Log(8) x 10]= 9.03dB

This is the decibel change from 1W to 8W.

You can also calculate the decibel change between two power levels using this formula:

Decibel change = [Log(P2/P1) x 10]

For example the decibel change when you raise the power from 2W to 8W is

[Log(8/2) x 10] = 6.02dB

You may be surprised to find that the decibel change when you raise the power from 200W to 800W is also 6.02dB

Another factor you will want to understand is what happens you add speakers. In most circumstances a parallel connection is used when you add a second cab. The ideal is to use matching cabs. When you add a matching cab with a parallel connection, the combined impedance is 1/2, the total power handling is 2x, and the combined sensitivity goes up approximately 3dB. Note: Real world sensitivity gains are slightly less and dependent on how close the drivers are to each other.

So if you have an 8 ohm cab rated for 200W with 97dB 1W/1m sensitivity. When you add a matching cab in parallel: The total impedance is 8/2 = 4 ohms, power handling is 200 x 2 = 400W, and sensitivity is 97 + 3 = 100dB 1W/1m.

The same changes occur every time you double the number of cabs. So if you add two more cabs: The total impedance is 4/2 = 2 ohms, power handling is 400 x 2 = 800W, and sensitivity is 100 + 3 = 103dB.

Let's assume the amp can make 200W at 8 ohm and 400W at 4 ohms.

With one cab:
Calculated SPL = [Log(200) x 10] + 97 = ~120dB

With both cabs:
Calculated SPL = [Log(400) x 10] + 100 = ~126dB

Note, in this example the SPL at full power increases ~+6dB. +3dB comes from doubling the power and +3dB comes from the increased sensitivity. If you double the cabs but hold the total power constant, you only get the +3dB from the increase sensitivity.

When the impedance is cut in half, some amps hold the power constant, some double the power, and some increase the power about 60-70%. Check the amp's specs for rated power at various impedances.