Making multi-room audio sound like a winner

52Multi-room audio doesn’t need to be just for background music. With a little bit of work, you can make whole house audio systems sing. Anthony Grimani explains.

A lot of folks seem resigned to the fact that whole house audio systems, with their in-wall/ceiling speakers, are going to sound pretty ho-hum. That doesn’t have to be the case.

Let’s take a closer look at some ways to improve the sound quality of whole house audio.

You should be pretty familiar with how to pick equipment, but there are a couple of things that often get overlooked. First, make sure that the matrix switching/routing system includes individual EQ and high-pass capabilities for each zone output. Products such as Crestron’s SWAMP have a 5-band parametric EQ already built-in. It’s buried in menus, but it’s there. Savant is another place to look. If your chosen brand doesn’t include EQ or HPF, there are products from Ashly, Symetrix and many others that will get you up and running.

Second, keep the speaker cable runs to reasonable lengths. High resistance in the wire may combine with the reactive load of the speaker to create significant electrical frequency response errors before sound ever leaves the speakers! These errors can easily exceed 3dB, which is plainly audible. Ideally, the wire loop resistance should not exceed 0.4Ω. For good quality 2.5-4 mm2 wire, this corresponds to about 36m. To make sure the wire resistance is not introducing major response errors, hook the wire up to the amp and speaker you plan to use, play pink noise and measure across the speaker terminals with your RTA. If the errors are less than 3dB, any wire run of equal or lesser length will be OK.

Third, avoid expensive, esoteric speakers. The mounting, orientation and room acoustics issues associated with in-wall/ceiling speakers overshadow the small improvements you might get with audiophile-type speakers. Don’t buy junk but don’t break the bank either. Put the money into the equalisation processing and wiring.

On to setup. If you add extra EQ or signal processing devices to the system, make sure you have adequate rack space and ventilation. Also investigate remotely locating an amp, or using individual zone amplifiers, to reduce speaker wire lengths. It’s always better to send audio over IP/Ethernet or balanced analogue for long distances.

Take care installing the speakers. Careless installation can lead to myriad problems that affect sound quality, such as inappropriate speaker cavity volume or mounting hardware that rattles and buzzes noisily.

Finally, test out each and every zone. What do I mean by tuning? Definitely measure the DC resistance through each wire and the attached speaker. A dead short could mean a blown amp with down time for replacement. Also check phase. With the sheer number of speakers in a whole house system, it’s a good bet somebody wired a few wrong. The quickest way to do this is to light up the entire system using a polarity pulse generator like the Gold Line APT2 or Galaxy Sound Cricket. Then check all the speakers using the analyser.

Once you’re sure all the speakers are in phase and receiving a good electrical response, it’s time for the special secret source: frequency response correction and tailoring. Now’s the time to engage that high-pass filter. What, specifically, does it accomplish? The typical two-way in-wall/ceiling speaker can’t handle much bass. The woofer gets pushed too hard, causing massive distortion and audible noise artifacts. Filtering out bass below 60Hz or 80Hz will produce a cleaner, more pleasant sound.

Finally, break out your audio analyser and start measuring and correcting the in-room frequency response. I suggest averaging at least four locations or using a four mic RTA multiplexer. I like to use free software by REW for signal generation and analysis, along with a reasonably good USB converter and test microphone. One trick I have learned is that the ideal frequency response curves we target for home cinema don’t necessarily translate well to whole house. This is due to a combination of factors, such as the sound power response of the speakers and comb filtering from multiple speakers on the same zone. Once you’ve smoothed out the peaks and dips in the response using your analyser, walk around comparing pink noise through the system to pink noise through reference in-ear transducers like Etymotic ER4-S. Tweak the spectral balance of the system until the two match.

This is a lot more work and expense than you’re probably accustomed to right now. I get that. It’s also a great way to grow your business and offer customised service that your competitors don’t. I suggest setting up a demo in your showroom to A/B the difference between a whole house zone with wire resistance that’s too high, a speaker that’s out of phase, bass overload and frequency response full of errors vs. the same speakers/amps with good wire, everything in phase, bass filtered, and smooth, equalized response. I promise you that the difference won’t be subtle. Once the client is sold on the results, it’s just a matter of multiplying that out to every zone!


Anthony Grimani is president of PMI, Ltd., an award-winning home cinema engineering firm; MSR Acoustics, a manufacturer of fine acoustical tuning systems; and Grimani Systems, a maker of groundbreaking and forward-thinking audio systems. MSR is represented in Australia by Wavetrain.

Chase Walton contributed to this column.

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Reference: Connected Home

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