DIY acoustic treatment for home recording studio

Nowadays, with technology progress, most of the amateur, but also professional music production happens in the home studios, usually in our bedrooms. It is time to learn how to build perfect control room, right in your bedroom.

The shape of the room

If possible , avoid square layouts. The worst possibility is a cube . Also, long elongated rooms are not appropriate. It is best to have rectangular room.

Placement of furniture and equipment

The most important spot in the studio is the listening position. The acoustic should be optimize there as much as possible. For rectangular room the desk with monitors should be positioned parallel to the shorter wall, ie . it should be perpendicular to the long wall. Due to the accumulation of echos and reverbs of the room, it is not suitable to place listening spot in the middle of the room. Place it closer to the shorter wall. It should be placed about 40 percent of the longer side. Ideal position for studio monitors is separate stands located between the shorter wall and the desk. Studio monitors should be above the table top. If the studio monitors must be placed on the table, it is always good idea to separate them from the table using a special material, so they do not reflect unwanted reflections. This material should not transmit vibrations to the table, so definitely wood is not a good idea. Try to use polystyrene foam or other harder, thicker layer of rubber, in an emergency you can use books.

The tweeter of studio monitors should normally placed at ear level, but it is better to look in the monitor manual, some manufacturers have a sweet point between the woofer and tweeter. Monitors should be at a greater distance from the wall, and certainly not in the corner, because then we will hear enhanced bass frequencies.

On a stand or tabletop slightly turn the speakers so they are pointing to a common point, which is the head of the listener. These three points - left monitor, right monitor and the head of the listener should together form an imaginary equilateral triangle with an angle of 60 ° at each corner. Location of monitors in the studio is the most important thing and it is worth some time to look for the best possibility with the help of the measuring microphone.

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For the acoustics the room symmetry is crucial. The table should be as far away from the wall to the left and right side. If you place furniture along one wall, there should be something similar along the other wall. Also, we place the acoustic elements symmetrically, as if the left part of the room would be mirrored the right. Otherwise you will hear a different sound in the left and right ear.

Noise of computer

Noise computers is a huge problem in the recording room. There are two ways to deal with this problem. Either you let build an entire computer from components, which are the least noisy or you will place comp. outside the recording room. The first solution is very expensive and also never completely resolved. The computer can also be placed in a sarcophagus - lined acoustically absorptive material, but there is a risk of overheating. Therefore, I can see the location of the PC outside the recording room as the final and best solution. Not a big deal to drill a larger hole in the wall, route the cables through a hole and afterwards clog it again with something. For this solution, it is advisable to use an external CD / DVD drive (USB or FW ), located in the recording room , so you do not have to constantly run out.

The room acoustics

We must distinguish the purpose for which the room we want to use. If we want to record instruments and sing into the microphone, acoustic treatment should primarily deal with thumping bass. Mids and Highs reflection can be present, so in the final sound will be powerfully and vividly, not sterile.

If the room is used for mixing, we have to choose a compromise between more vivid and dead rooms, because during the mixing session is desirable to have less reflections. Some engineers and music producers even prefer to mix in the completely dead room.

A separate chapter is, when we want to deal with in addition to the room acoustics also sound leakage inside out. Then we have to basically build a room in the room. First, overlaid on sides (including doors) with a thick layer of acoustically absorptive material (eg mineral wool) and closes all openings, because even the smallest can ruin our work, and afterwars we can deal with the internal acoustics in the inner room according to the text above.

Suitable materials

In the small rooms it is the best form of treatment acoustic absorption, ie . absorption of maximum number of reflections. As a complementary solution we can also install diffusers, which are designed to eliminate repetitive echoes and resonators that absorb specific frequencies, which were calculated. But it is always good to start in a home studio with absorbers.

Generally, a higher frequency (1.6 kHz above) absorbs any material that has a little rougher surface, such as the drapery hooked on the window. Mid-frequency (300Hz - 1 .6 kHz) already require a mass of material and the hardest is to absorb frequencies below 300kHz, where we need to have a good acoustically absorptive material and even a considerable thickness.

For beginners with acoustics is best to purchase a broadband absorber that absorbs everything - bass, mid and treble. The first suitable product with such a properties is a mineral wool. Each of the producers (Rockwool Orsil Knauf and others) has a range of more preferable types of wool for sound absorption and less suitable. It is necessary to look into the catalog. I had a very good experience with the products Orsil Orstrop , Rockwool and Isover Domo Airrock ND.

Another suitable material is the so called acoustic foam, which have open cells, and absorbs sound energy very well. If you have more money you can buy whole acoustic solution set for room treatment.

How thick acoustic material we need

It is true that the lower frequencies we absorb, the stronger must be acoustically absorptive material. Absorber for absorbing bass, middle and treble is necessary to use mineral wool ideally with a thickness of 200 mm. The same holds true with acoustic foam. The thickness of wool around 100m we will not have absorbed frequencies below 100Hz. If you have a low budget, you can install crash absorbers with a thickness of wool around 100m and slightly delay it from the wall. Absorption lower frequencies will improve, but a much better solution is to have a thickness of absorbing material more than 160 mm .

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Home made production of acoustic elements

For the homemade production of acoustic elements you have basically a few options:

  1. Make a portable walls, and surround your recording corner. After recording you can always move them somewhere in a corner. Wooden frames filled with mineral wool in foil and covered with textile are usually working well.
  2. Make the elements that will be placed on the walls and into corners, but in the case of migration will be transferable.

Some comments on this:

When working with mineral wool definitely wear a dust mask and gloves. Long-term inhalation of cotton is hazardous to health. That is why I recommend wool absorber placed in a foil (eg large plastic garbage bags) to avoid leakage of small particles of cotton. If you drag a textile over the absorber material, you do not have to worry about the negative impact of plastic bags on the acoustic properties. Mids and bass pass through it without any problems and the Hi will absorbs into the textile.

Where to place the acoustic elements

Let's start by installing acoustic components in all corners of the room and floor-to -ceiling windows. Due to the accumulation of bass in the corners there should be a maximum thickness of absorbing material - ideally 200 mm and more. Other absorbers can be placed on the wall, which routes the monitor speakers. When you sit at the table, it should be a wall behind you. Absorbers install in locations where the monitors are pointing out. You can choose absorbers with thinner materials (eg 100 mm) and because of the fragmentation of reflection is suitable absorbers slightly rotated.

Next, place the ceiling absorber between your head and the back wall. Afterwards we can measure our treatment with microphone, because it is possible that these adjustments will already be sufficient.

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Measurement

After installation of acoustic elements is appropriate to not only rely on our ears. It is always good to measure the acoustics of the room with microphone. Cheapest microphones for use are a Behringer ECM8000 T.BONE MM1. You can also use another microphone (for example, large diaphragm vocal condenser), but then you must have a manufacturer specific characteristics of your printed piece and have entered into the measuring software. Measurement microphones apart from other mics are characterized by a relatively linear characteristic. If you use other microphone with an unknown characteristic, there is always a risk, that you will see in the resulting graph problem, where in fact it is not.

As measuring software can be used as Room EQ Wizard. The measurement is performed so that the microphone is placed on the stand against one of the monitors. The height should be where is your head when listening. If the microphone has a switchable characteristics, switch to the omni. Other characteristics tend to hide the shortcomings of the room. Run the preamp and measurement software. On the preamp we will set the required gain and run the test. From the monitors we will hear a frequencies from the bass to the  highs, which microphone will record into software. After measuring and generating curves turn the microphone against the next monitor and repeat the measurement.

After the measurement, the measuring softwarewill generate the curve of the two monitors through the entire frequency range. The elevations or depressions in the graph show room problems, which need to be discussed further.

For example, if there is a hump at 150Hz, it means that in the room there are too rumbling bass and you need to install additional acoustic elements. Conversely, if for example there is a suppressed band around 5 kHz, it means that we too many absorbers at higher frequencies and it is necessary to increase the number of smooth surfaces.

With Acoustic modifications and treatments we are always trying to straighten the curve as much as possible . If these differences will result in + / - 15dB, we have suitably adjusted room for recording,  excellent adapted room will result into + / -6dB.

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