The RSL Advantage
Compression Guide Technology and our approach to speaker design
February 07, 2011 by EH Staff

RSL is not the only speaker manufacturer that combines high quality parts with design expertise.  However, there are things that set us apart. Among them, is our patented Compression Guidetm technology. This is a different approach to speaker design and we believe it overcomes many of the problems found in most speakers. If you’re interested in a technical explanation, read the next section “The Problem.” Otherwise,  skip to “The Benefits of Compression Guide” section.

The Problem
Conventional speaker enclosures use one of two methods to tune the woofer to the enclosure. In one method, the enclosure is completely sealed. This method is referred to as air suspension or acoustic suspension. The trapped air inside acts like a spring to put a load on the woofer. In the other method, the enclosure has a tube or a vent which leads to the outside of the enclosure. This method is called bass reflex or vented. This tube or vent resonates at a particular frequency and reinforces the bass response.

In both of these designs the enclosures have a frequency at which they resonate.  Think of it as blowing across the opening of a bottle. No matter how you blow, the bottle will always make the same sound. The same holds true in these enclosure designs. No matter what frequency the woofer produces, the enclosure will produce the same resonant frequency. For example, let’s assume the system has a resonance of 60 Hz and the speaker is called on to reproduce a 1,000 Hz tone. It will not only reproduce that 1,000 Hz tone, but in addition, 3 other unwanted tones. Besides the 1,000 HZ tone, the 60 Hz resonance tone also emerges which colors the sound. In addition, the 1,000 Hz and the 60 Hz tones mix creating 2 more tones. These new tones are the sum and the difference of the 60Hz resonance and the desired 1,000 Hz. The end result is 1,000 Hz, 60 Hz, 1,060 Hz, and 940 Hz, which severely degrades the clarity of the speaker.

Resonance is the enemy of speakers and in addition to destroying clarity, slows the woofer response. This limits bass response and gives it a sloppy quality. This is why bass at a live performance sounds different than bass at home. Instead of hearing a “rap” from the skin of a kick-drum, you hear a dull boom. It is also why most home theater subwoofers constantly let you know there is a separate subwoofer operating, instead of blending properly with the other speakers. A subwoofer should sound as if the bass is originating from the smaller satellite speakers. To combat this problem, many expensive subwoofers encourage you to cross them over at very low frequencies. This requires you to use larger satellite speakers throughout your system to properly blend to the subwoofer.

That evil Mr. Resonance has another dirty trick up his sleeve. The tweeter, which has very little mass, responds very quickly to the frequencies it’s fed.  Resonance slows the woofer making it lag behind the faster tweeter. The big difference in response speed between the woofer and tweeter causes the sound image to collapse into the enclosure. That’s why even good speakers still sound like speakers. Instead of the performers seeming to image in the room, the image still seems to come from the box. Even in expensive stereo installations, the image of a vocalist that emanates from both the left and right speakers can seem to be 8 feet wide, instead of a pinpoint position between the speakers.

The purpose of Compression Guidetm is to drastically reduce resonance inside the enclosure. A Compression Guide enclosure contains areas of varying volume. During sound reproduction, the woofer moves in and out. When moving in, sound waves are emitted from the back of the woofer cone and travel to the port of the enclosure where they are transferred to the outside. As they travel in the enclosure, they pass through areas of varying volume, which causes the air to compress and then decompress. These areas of compression properly load and tune the woofer and prevent the build up of resonances. The same is true when the woofer moves outward. Air that is drawn into the port goes through areas of varying volumes (compression and de-compression) as it moves towards the back of the woofer cone.

The Benefits of Compression Guide™
With Compression Guidetm woofer response is dramatically faster. You’ll hear details in instruments such as cellos and bass drums that are blurred by normal speakers. In addition to increased overall clarity, the bass response is deeper. Many subwoofers achieve deep bass response in a small cabinet by utilizing a very heavy woofer cone. The problem with this approach is that the bass is sloppy and the woofer is inefficient. That’s why they have to utilize amplifiers rated at very high wattage (1,000 watts or more).>

The RSL Speedwoofertm 10 is in a normal-sized enclosure (approximately 1 1/2 cubic feet) and its bass responds down to 20 Hz (-3db at 24 Hz). However, more important than the frequency response is the quality of the bass. In home theater installations, most subwoofers do not blend with the other speakers and seem to be easily distinguishable. This type of intrusion has always bothered us. Thankfully, the RSL Speedwoofertm 10 sonically vanishes and is one of the first truly intrusion-less subwoofers. In stereo installations, the RSL Speedwoofer 10 is even fast enough to blend well with expensive and lightning-fast electrostatic speakers.

With Compression Guide, bass response is so good that our satellite speakers can be smaller and still blend perfectly with the subwoofer.  The smaller the speaker, the better it can image voices and instruments in your listening room. A smaller box is also easier to place.

Also with Compression Guide, midrange sounds, (such as voices) come through crystal clear, without the boxy sound of a typical speaker. One final benefit of Compression Guide is superior imaging. With music for example, the musicians will seem like they are in your room and not coming from a box.

Many speaker manufacturers are quick to boast how their speaker enclosure uses exotic materials to eliminate cabinet resonances. What they are referring to is eliminating vibration in the walls of the enclosure, which is a good thing, but misses the point. They should also be directing their efforts at the resonance within the enclosure.

Another item speaker manufacturers hype is exotic cone material that is stiff and inert. We agree that it is important that speaker cones do not create unwanted sounds of their own.  However, when the woofer cone has to deal with the unwanted effects of resonance, its performance is diminished regardless of the cone material.

It’s Not Enough to Build a Speaker that Measures Well
Many manufacturers, rely almost completely on measurements when they design speakers. It is possible to design a speaker that measures well and sounds lousy. That’s because the science of speaker design is incomplete and constantly changing. At RSL, when we design a speaker, listening is every bit as important as measuring. We test our speakers in different environments. Many of our friends, who own high-end audio/video shops, allow us to set up our speakers next to their favorites, which are often quite expensive. These listening tests have satisfied us and our friends that our speakers will live up to the claims we make.

RSL Speakers Are a One-Time Investment
We have always used high quality parts in our speakers. That’s why many RSL Speakers are still going strong despite being up to 40 years old.
The speakers we offer today are designed to provide thrilling performances for many years to come.


RSL Speaker Systems
A Division Of Rogersound Labs, L.L.C.
26500 W. Agoura Road, Suite 571
Calabasas, California, 91302
United States of America
Phone: (800) 905-5485

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