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When, where and how to install acoustic panels in your home theater.

Posted by Karl Anderson on 7/9/2020 to DIY
So you’ve spent good money on a DIY audio system for your home theater which most likely includes a bunch of surround sound Atmos speakers and an AVR (audio video receiver) or Pre-Processor and amplifiers. If you’re like most people the installation of this equipment seemed to take forever and you definitely spent more time on it than you thought you would when you first envisioned doing this little DIY audio project. But it’s done now and you’ve got it all working in the room and now comes the fun part, you get to sit down and evaluate the performance of your home theater audio system. Now, like most people who spend the time to install an advanced audio system from a selection of premium electronics you are most likely immediately blown away by the initial listening experience. After all, you spent some good time and money on this stuff and it should perform well out of the box. It’s a job well done and depending on your expectations this could be where the story ends, another home project under your belt and the system sounds great!

For the rest of this article I will be speaking to those of you who want or need to know they are getting the most out of their home theater surround sound speaker system. Perhaps those initial impressions of your sound system have faded and you’ve now had some critical listening time with mixed results. Whether you’ve found some real sound problems or just want more out of your speakers, here are some solutions that can dramatically improve how your room speakers sound.

Spend some time calibrating the speakers for the room:

All legitimate AVRs and Pre-Processors have a calibration feature that can make important corrections to speaker timings, levels and equalization. Using the included microphone you can dramatically change the result of the sound performance of your room. For best results follow the calibration instructions that came with your device and remember to re-apply when you change the room’s acoustics, such as moving furniture, adding drapery or acoustic panels.

Time for some acoustic panels:

Interestingly enough the addition of acoustic panels to a room is one of the most affordable ways to increase the audio quality of a home theater. Installation times vary depending on panel sizes but for an average full room set of acoustic panels it only takes about an hour for a 20’ x 20’ room.

So what type of acoustic panels should I get? The three main criteria for selecting acoustic panels are thickness, size and fabric. Average basic fabric panels are usually around fifty dollars a panel for a larger 1” or 2” thick panel with plenty of fabric colors and textures to choose from. At Home Theater Seattle we sell a 1” thick acoustic panel that is 25” x 37” in sizethat will run you $199 each. The major difference in price being that our panels have movie poster art printed on the acoustically transparent fabric which will cost you more. Overall using acoustic panels with a size that stops waves from the walls getting to your ears is the expected result.

So to answer the questions of when, where and how let’s start with why.

Why do I need acoustic panels?

It’s all about the physics of sound. Let me illuminate briefly. A sound wave that travels from your speakers to your ears takes multiple paths from the speaker. Not only does it travel straight to your ears but it also travels to the walls in your room where it gets reflected toward your ears. These reflections also make the journey from the speaker to your ears but arrive shortly after the non-reflected sound waves do. You may not even notice the effect of this “comb filtering”, but you are hearing the wall’s negative influence on your room audio (frequency response). Since it is fair to assume that the wave is still intact for both paths the peaks and valleys of the waves for both paths are now out of phase and have a tendency to cancel or boost each other which damages the imaging and clarity of sound to the listening position. Stopping the walls from reflecting sound removes or reduces this effect. Acoustic panels “absorption panels” are an excellent product used to significantly decrease or eliminate these sound issues.

When should I use acoustic panels?

Always! Why not? Regardless of the speaker system you have, the speakers will produce reflections that reduce the quality of sound to your ears. If your room has walls for acoustic panels you should consider applying some.

Where in my home theater room should I put acoustic panels?

There are some simple rules to follow that will create great results and get you 90% of the way there without much effort.

For the purpose of this blog post we will only touch briefly on some very rudimentary aspects of acoustic panel placement. Although acoustics is a science, using some of these simple rules and techniques can easily help make a dramatic improvement in any listening environment.

Let’s start by combating “First Reflections” using these steps:

Find the “First Reflection Point” by using a mirror. This is done by sitting in the main listening position of the room facing the front speakers. Have a friend place a hand mirror on the left wall. At speaker height have the friend move the mirror on the wall until you can “SEE” the left speaker’s reflection in the mirror. Mark that spot on the wall with tape. Continue moving the mirror until you see the right speaker. Mark that spot on the wall with tape. Repeat this process for the right wall. You now have your first locations for acoustic panels in your room! If you have a second row of seats repeat this for that listening location and mark the wall.

A really great video from GIK Acoustics showing this concept can be found here:

Ultimately the spots you marked on the wall should be the location(s) of your acoustic movie posters! In practice you can approximate the location of your acoustic panels and split the difference with one acoustic movie poster to save on the number of panels needed. It’s up to you! For a simple home theater this seems to work just fine.

For a 20’ x 20’ room we usually suggest one or two acoustic movie posters for the back wall and one or two for the back third of the side walls of the room for aesthetics and other reflection points in addition to the first reflection panels. So as a rule, an average room should have between 5 and 12 strategically placed acoustic movie posters or a mix of acoustic movie posters and acoustic panels.

Although the placement, type, and quantity suggestions we have made above are very effective, they should not be considered complete or definitive acoustic treatment of a room. If you’re interested in a more precise sound environment we suggest contacting an acoustic service professional in your area for a consultation.

How do I install acoustic panels?

There are a lot of ways to hang an acoustic panel on a wall. At Home Theater Seattle we have a slick little z-clip system that works particularly well. Half the clip is mounted level on the wall and the other half is applied upside down and level on the acoustic panel. For a really good look at an installation of panels in a home theater check out the video from our friends at Crafted Workshop. You'll find the acoustic panel install near the end of the video! Enjoy.

In conclusion:

Understanding the when, where, why, how of acoustic panels is fun and the results are often remarkable without even trying. Experiment with sizes, locations, and dig as deep as you want into this fascinating science.