Monday Mailbag – 50hz boom problem

Hi Mike,

I’m adapting the front room of my apartment so it can be used as a home studio. The problem is the sound is awful at present with an annoying long boom in the 50Hz range and strong mode issues between 100 and 150 or so.

I believe it is because of the brick walls which are 12ft distance from each other and which the speakers directly fire at. Because it is also my lounge I don’t want it to be too covered in thick tube traps (12 to 17cm would be max). Also I don’t own the property so I can’t really go about mashing up the walls or ceilings too much with screws, etc. I have some space available either side of the speakers for traps.

Do you have any recommendations of what I can do with this situation?

Thanks
Pete

Hi Pete,

You will have to trade real estate to minimize your acoustical issues. To deal with your particular situation, you will need some frequency specific low frequency absorbers and you will also need some broadband absorbers to cover the 100 – 150 cycle range. Acoustic foams do go down to 100 Hz. but their rate and level of absorption will be lower than you will probably require. You need serious low frequency absorption to deal with a 50 Hz. resonances.

Since you do not own the property, you can get freestanding absorbers that will assist you but you will have to provide places for them to go into. These places are not places of convenience or because you have the room for them in this or that location, but they need to be placed where the resonances are within the room to have maximum impact. The side walls at 12′ present axial modal issues that must be addressed with low frequency absorbers that have the necessary rates and levels of absorption to deal with their magnitude.

Space next to your speakers can be a good place to start with low frequency absorption because the speaker is a pressure source and placing low frequency next to the pressure source is advisable when you are trying to reduce low frequency pressure issues. This is no place for foam. Use diaphragmatic absorption because it works well in regions and areas of high pressure. In fact, diaphragmatic absorption needs sound pressure to operate at its best. You can add foam to the low frequency absorber to handle middle and high frequencies.

Regards,
Mike

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