Build Your Own Baffle Wall for Your Home Theatre

Some of the Content of this article from from the SHC LCR10 DIY Speaker Build Guide

The “Infinite” Baffle Wall

Sound emanating from speakers will generally go around the cabinet, hit the wall, bounce back and interfere with the direct sound. This can be problematic in the lower midrange and upper bass especially, and rob the sound of some of its clarity.

To solve this issue, Australian speaker manufacturer, Krix invented the Infinite Baffle Wall for commercial cinema applications in the early 1980s.  It has been used in commercial cinema since then with great success, with other manufacturers following suit. It is only recently that this technology started to trickle down to the home with Krix once again being a pioneer with the MX Series of Speakers, called The Wall of Sound.

After hearing a home installation of Krix’s MX30, we knew we wanted to create a design that can match – or better – the performance of it, but with a shallower and more modular design that would fit into more spaces. This certainly turned out to be a challenge, but we feel we have achieved our goals by employing clever design and making the right compromises. The results are the SHC LCR10s (LCR stands for Left Centre Right) employing 10″ midrange drivers and the SHC SUB15s employing 15″ high-efficiency OR high output subwoofer drivers.

But before we introduce the speakers and go into the configurations, let’s recap the benefits of a baffle wall.

“Infinite” Baffle Wall Benefits

• Sound doesn’t “wrap around” the speakers, bounce off the front wall then interfere with the direct sound. Instead, the sound runs along the face of the baffle wall and hits the left and right walls. However, those are generally too far away to interfere in the same way as the front wall and can be easily treated for even better performance.
• The above results in a lot more clarity, especially in the midrange and upper bass
• The frequency response of the front soundstage smooth out delivering a more balanced sound and much higher impact
• The phase / time-domain response of the front soundstage gets much better delivering better clarity and imaging
• Dialogue intelligibility goes up as there is very little interference with the direct sound

SHC LCR10 Speaker Configurations

You could simply build 3 SHC LCR10s for the front wall and fill the rest in using fibreglass insulation to create an Infinite Baffle Wall. However, in this article, I want to talk you through all the options that you can use whatever the size of your room or the space behind or even under your screen.

LCR10 30L (half-height) Configuration

Dimensions (WxDxH): 45cm x 25cm x 52cm / 18in x 10in x 20.5in- 2 ports of 20.5cm / 8in (30L = 30Litres)

The 30L is called that because it has an internal volume of 30 litres.

This configuration is suitable for smaller rooms where space is at a premium. The box still delivers an F3 of around 58Hz by design and 50Hz in-room in rooms of up to 5 meters in length.

In spite of its smaller size, this speaker packs quite a punch due to the high efficiency of over 96dB and its low tuning frequency. In fact, even without using a subwoofer, bass notes in music take on a real presence due to the large 10” mid-range driver that extends down to 50Hz cleanly and will provide some bass even down to around 40Hz.

While this speaker isn’t meant to be used without a sub for movies, we thoroughly enjoyed listening to bass heavy dance music on them without subs during design and testing.

LCR10 60L (full-height) Configuration

Dimensions (WxDxH): 45cm x 25cm x 104cm / 18in x 10in x 41in – 2 ports of 20.5cm / 8in (60L = 60Litres)

This configuration is suitable for larger rooms of up to 10meters in length while still delivering an F3 of around 40Hz. It is also the recommended setup if you will be installing it behind the screen into a larger gap, and you will be employing 4 subs at the front, as the full 4-sub configuration is only compatible with the full-height boxes after an additional 20cm extension – more on that in a moment.

To achieve the full height, you will be creating an extension box that either goes on the top or the bottom of the speaker. Alternatively, you can also bolt on half-extensions to both the top and the bottom to have the drivers sit half-way for shelves that are mid-height. This allows you to aim the speaker correctly at the audience.

When deciding which configuration you need, you need to consider that the half-way point between the horn-loaded compression driver and the midrange driver is the speaker’s acoustical centre. This needs to be at ear-height for the listeners. If there are more than one rows of seats, try and have the acoustical centre to be at the midway point of people’s ears in the different rows. It is generally a good idea for the compression driver to clear the top of the first-row seats so that it can project into the back row without any obstacles.

Speaker Configuration	Acoustical Centre from Bottom w/o Feet	With EXT16
30L	278mm	438mm
60L Top	814mm	967mm
60L Middle	538mm	698mm
60L Bottom	278mm	438mm

If you are unsure, it is best to build the 30L box first, try different speaker heights and then decide which extension box you will need for the full-height speaker. When doing this, remember to only use screws to attach the top and bottom panels. This is why we designed the 30L LCR to have separate top and bottom plates, while the extension boxes do not have this feature as they don’t need it.

Extension Boxes

There are three extension boxes for SHC LCR10s: an extra 30L box, a 15L box and a 16cm height extension box.

30L Extension Box

The 30L extension is designed to extend the internal volume of the box to 60 litres and can be installed either on the bottom or the top of the box, dependent on how high you want the drivers to sit. In my room, for example, they will be installed on top, as the shelf they sit on is already at the right ear height. However, in your room, you may have the speakers sitting on the floor, which means they will need the extension box to be put on the bottom.

15L Extension Box

The 15L extension box allows you to bring the drivers into the middle of the speaker box which might allow for better driver-positioning in your room. You can achieve this by bolting on the 15L extension to both the top and the bottom of the LCR10s. This means you will always make the 15L extension boxes in pairs.

“Wall of Sound” Configurations

Now that we had a look at how to configure the LCR10 by itself or by using extension boxes, let’s have a look at the options for building the Wall of Sound using them.

Half-Height Configuration

This configuration uses LCR10s in their 30L half-height configuration with matching 60L subs. This configuration is suitable for users that:

1. Can only place the speakers below or over the screen.
2. Don’t have a lot of space behind the screen / have a small enclave or shelf
3. The shelf behind the screen is not strong enough to hold full-size speakers

The half-height configuration retains the performance of the full-height configuration and is suitable for rooms up to 5 metres in length. Beyond this, we would recommend two extra subwoofers at the back of the room for support.

Full-Height Configuration (1m height) – DRIVERS TOP

This configuration uses LCR10s in their 60L full-height configuration with matching 120L subs. This configuration is suitable for users that:

1. Have enough space behind the screen 
2. Intend to place the speakers on the floor standing behind the screen or onto a low shelf / enclave
3. Want the lower extension that both the 60L LCRs and 120L subs can deliver.

This is the full-performance configuration and is suitable for rooms up to 10meters in length with some caveats. Please see the Room Sizing chapter for more information.

Full-Height Configuration (1m height) – DRIVERS BOTTOM

This configuration uses LCR10s in their 60L full-height configuration with matching 120L subs. This configuration is suitable for users that:

1. Have enough space behind the screen 
2. Intend to place the speakers on a higher shelf or enclave with the drivers needing to be on the bottom of the cabinets.
3. Want the lower extension that both the 60L LCRs and 120L subs can deliver.

This is the full-performance configuration and is suitable for rooms up to 10meters in length with some caveats. Please see the Room Sizing chapter for more information.

Full-Height Configuration (1m height) – DRIVER MIDDLE

This configuration uses LCR10s in their 60L full-height configuration with matching 120L subs. This configuration is suitable for users that:

1. Have enough space behind the screen 
2. Intend to place the speakers on a mid shelf or enclave with the drivers needing to be in the middle of the cabinets.
3. Want the lower extension that both the 60L LCRs and 120L subs can deliver.

This is the full-performance configuration and is suitable for rooms up to 10meters in length with some caveats. Please see the Room Sizing chapter for more information.

Full-Height Configuration (1m height) – 4 Subs

In this configuration, the LCRs are reach 104cms in height. This also allows us to use  two subwoofer boxes per side , as opposed to only 1 driver each.

These subwoofer drivers can either share the same box volume or be in their own internal chamber and be driven independently – such as when employing the extra drivers for Active Room Treatment as in the case of Dirac Live ART or Trinnov’s solution for the same. 

This configuration is suitable for people that need the most output from the subwoofers due to a larger room or want to use Active Room Treatment without taking up more floor-space for the extra subwoofers.

Creating the Enclave Behind The Projection Screen

As we said earlier, you have some configuration options to place The Wall of Sound under or behind the screen. If you want to go for the option of creating an enclave, you need to make sure of the following:

• It is at least 30cm deep. This will allow you to have space for wiring and some space between the screen and the speakers, especially if you will be using a woven screen.
• If you plan on employing a perforated screen, you need to be aware that placing speakers an additional 15-30cms behind the screen would allow for better sound quality due to less pronounced comb filtering. Comb filtering creates peaks and valleys in the frequency response that cannot be calibrated out with EQ. Unfortunately, perforated screens are affected by this more.

Conclusion

While I will talk about the performance of these speakers in other articles, let me just say that we are delighted with the results. I haven’t heard such clarity in my own home theatre, and I have spent many years optimising it – if you have been reading this blog and my guides.

But this is why we wanted to take the next step in the evolution of our home theatre: designing our own speakers, and boy, are we glad we did! More to come soon!