Speaker Isolation, The Tweak That Actually Works
n HiFi, many tweaks claim to improve sound quality, but the isolation of speakers and their component parts is one that truly makes an audible difference.
I am not typically one to promote the use of special objects in the listening room, but isolation is a concept that has real science and logic behind it. And it’s something I have recent experience with. Almost by accident, or perhaps by fortuitous timing, I have found a simple and inexpensive way to improve bass balance and control in my speakers. I’ll talk about my application shortly but first, some background and context.
What Is Isolation?
When a driver cone or ribbon is excited by electricity, it vibrates. The moving cone or ribbon pushes air, hopefully in the direction of our ears, and we hear the result as sound. Obviously, controlling that vibration is the key to more realistic sound reproduction. We can have super precise drivers and a crossover built from premium components but that’s not enough. The driver itself must be physically restrained, otherwise more than just the cone or ribbon will vibrate. Remember that Newton guy? He said, “Every action has an equal and opposite reaction.” If you don’t lock that cone down, the cage, motor, magnet, and everything else that makes it up will vibrate too. Driver cages aren’t engineered to reproduce sound. So, you don’t want them spoiling the party.
Most speaker designs bolt the driver firmly to the front baffle. But this introduces another variable. Now, the baffle will want to vibrate. The energy from the driver’s cone must go somewhere. Good speakers combat this with a thick baffle, usually made from MDF or some other heavy inert material. But what if the driver had some way of dissipating that energy before it reached the baffle? Hmm, I think we’re on to something.
Examples of Isolation in Modern Speaker Designs
Paradigm then isolates the baffle from the enclosure in the same way, with elastomer mounting. Any sound resonating inside the enclosure is controlled by extensive bracing which keeps the enclosure from moving any air of its own. Then the enclosure is isolated from the floor by two-piece feet. The end result is that sound is produced only by the movement of the driver cone and nothing else.
How I Addressed the Issue
Adding the feet was almost like dialing in a response filter. The bass modes weren’t completely erased but they were so much quieter that I quickly stopped noticing them. If you want to try this for yourself, cue up the nightclub scene in the first Matrix film. It has a pounding bass and drum track that will expose poorly controlled bass no matter what your room or system is. Bolting on the feet made this scene far more watchable and I could now hear Neo and Trinity’s conversation without straining.
The Logic Behind It
To affect compromise, I installed aftermarket engine mounts. They are stiffer than the stock rubber pieces but still soft enough to keep vibration at a reasonable level. Yes, I felt some buzzing in the cabin. But the car was much better behaved in corners where I had to get on or off the throttle.
How does this translate? It’s simple. When a driver cone moves air, it produces sound. It’s precisely controlled by its motor and magnet. If that driver also vibrates the cabinet, it dissipates some energy that could be used to, you guessed it, produce sound. If less energy is wasted on extraneous vibration, the sound is better controlled and balanced.
One of my pairs of speakers, the Axiom M80s, is up on a wooden bench rather than on the floor. This piece of furniture will vibrate. Clearly, that removes some energy from the speaker’s ability to produce sound. By isolating the M80s from the bench, I was able to turn the volume down by 2dB to achieve the same perceived loudness. My other speakers and subs? They are on the floor, carpet over concrete. While concrete might seem to be an inert material, it is not. It will vibrate at high volumes enough that you can feel it through your bare feet. Adding the SVS SoundPath isolators allowed me to stand right next to my EP800 sub as it thumped away while I felt nothing from the floor. Again, I had to adjust the speaker and subwoofer levels to maintain the correct balance.