chrisstankevitz
New member
I have used two MP40s on my cube aquarium (24" x 24" x 20") for two years. I am an engineer and work on resonating gyroscopes. I am familiar with resonance, control loops, fine tuning, etc. I am fanatical about keeping my tank quiet.
The MP40 is a beast and will be very loud unless it is properly tuned and housed. The MP40 is the loudest part of my tank.
1. Dry Side Humming
Example: http://www.youtube.com/watch?v=EPChUv5vcCw
The dry side contains a motor that hums while it runs. I think nothing can be done about this other than run it at a lower speed. This high frequency sound does not travel far and has never bothered me.
2. Dry side knocking
The dry side sometimes knocks. This is a frightening sound that will fill the room. This is usually a function of speed e.g. it will knock at 70% power but at no other power. This can be easily fixed by making fine adjustment to the dry side. I will move the MP40 dry side up/down/left/right or rotate it clockwise/counterclockwise to remove the knock. Then I will try another speed and re-make the adjustments. Then I try another speed. This works best in the green "constant speed" mode.
3. Wet side knocking
The wet side will knock also at certain speeds. I fix this with the same kinds of adjustments as the dry side knocking. However, after some time adjusting you might reach a point where no further improvement can be made. At this point I reach in the tank and rotate the wet side. Perhaps it's just superstition, but I always rotate my wet sides so that the part of the casing that has no slits in it points up. I find that the MP40 wet side will settle into this position anyway after months of use.
4. Wet side rattle
This started after an overnight MP40 dunk in the vinegar jar. I think the cleaning loosened something and one of the blades is hitting the housing at certain high RPMs. I'm not sure yet about this one as it's new to me...
5. Stand Vibration
Once properly "tuned", my MP40 still makes a lot of noise that is neither humming, knocking, nor rattling. It's a vibration that permeates the whole house. My house sits on a raised foundation and somehow the sound of the motors transmits into the floor and all over the house. I recently discovered though that the sound is not coming out of the motors themselves. Rather the motors are vibrating the tank. And the tank is transmitting those vibrations to my hood and to my stand. The walls of my hood and stand vibrate and, acting as a speaker, transmit the noise to my room, floor, and house. I can tell that the noise is coming from the stand by placing my ear near/on the hood, stand glass, and the motors themselves. I'm not sure how I'm going to deal with that but it might involve putting pads between the tank and hood, or some kind of sound deading inside my stand. My stand is effectively a plywood box 4' by 2' by 2'.
Chris
The MP40 is a beast and will be very loud unless it is properly tuned and housed. The MP40 is the loudest part of my tank.
1. Dry Side Humming
Example: http://www.youtube.com/watch?v=EPChUv5vcCw
The dry side contains a motor that hums while it runs. I think nothing can be done about this other than run it at a lower speed. This high frequency sound does not travel far and has never bothered me.
2. Dry side knocking
The dry side sometimes knocks. This is a frightening sound that will fill the room. This is usually a function of speed e.g. it will knock at 70% power but at no other power. This can be easily fixed by making fine adjustment to the dry side. I will move the MP40 dry side up/down/left/right or rotate it clockwise/counterclockwise to remove the knock. Then I will try another speed and re-make the adjustments. Then I try another speed. This works best in the green "constant speed" mode.
3. Wet side knocking
The wet side will knock also at certain speeds. I fix this with the same kinds of adjustments as the dry side knocking. However, after some time adjusting you might reach a point where no further improvement can be made. At this point I reach in the tank and rotate the wet side. Perhaps it's just superstition, but I always rotate my wet sides so that the part of the casing that has no slits in it points up. I find that the MP40 wet side will settle into this position anyway after months of use.
4. Wet side rattle
This started after an overnight MP40 dunk in the vinegar jar. I think the cleaning loosened something and one of the blades is hitting the housing at certain high RPMs. I'm not sure yet about this one as it's new to me...
5. Stand Vibration
Once properly "tuned", my MP40 still makes a lot of noise that is neither humming, knocking, nor rattling. It's a vibration that permeates the whole house. My house sits on a raised foundation and somehow the sound of the motors transmits into the floor and all over the house. I recently discovered though that the sound is not coming out of the motors themselves. Rather the motors are vibrating the tank. And the tank is transmitting those vibrations to my hood and to my stand. The walls of my hood and stand vibrate and, acting as a speaker, transmit the noise to my room, floor, and house. I can tell that the noise is coming from the stand by placing my ear near/on the hood, stand glass, and the motors themselves. I'm not sure how I'm going to deal with that but it might involve putting pads between the tank and hood, or some kind of sound deading inside my stand. My stand is effectively a plywood box 4' by 2' by 2'.
Chris
