Surround Sound Speaker Systems
- Written by Jim Clements
- Published on 12 July 2010
- JBL LS 80 Floor-Standing Speakers, LS Center, LS 40 Rear Surround Speakers, and LS 120P Subwoofer
- Page 2: Design of the JBL LS Home Theater Speaker System
- Page 3: Setup of the JBL LS Home Theater Speaker System
- Page 4: The JBL LS Home Theater Speaker System In Use
- Page 5: The JBL LS Home Theater Speaker System On the Bench
- Page 6: Conclusions About the JBL LS Home Theater Speaker System
- All Pages
The JBL LS 80's are large floor standing speakers. They aren't crazy big like some speakers out there: the LS 80's are built to an acceptable domestic scale. But they are pretty big. I find that large floor standing speakers have an ease and harmonic richness to their sound. These are qualities that many small sat/sub systems can only hint at with their performance. If the speakers are large, chances are their sound will be big.
Let's start out by looking at the 176ND mid/tweeter. This is a 2" compression driver with a pure titanium diaphragm. It has a surround that is formed in a diamond pattern that is said to extend the driver's operation beyond its resonance limit. It has a powerful magnet structure and a lightweight aluminum voice coil. The voice coil is edge-wound with conductors that have rectangular cross-sections. This driver is ferrofluid-cooled as well. JBL claims that this driver substantially reduces thermal compression due to many of these design elements. This driver is loaded into a Bi-Radial horn. This horn provides constant directivity and excellent transient response.
These speakers are equipped with a ¾" super tweeter which is said to have extension beyond 40kHz. The diaphragm on this driver is a polyimide ring radiator which is driven by a high power magnet structure similar to the one found in the mid/tweeter.
The woofers have diaphragms made of Polyplas® which is a special long-fiber cellulose material (paper). It is said to have good internal damping properties because of the material's long fibers. These drivers also have powerful magnet structures and cast aluminum frames/baskets. Many of the design elements of these drivers are focused on providing high power handling, linear response and reduced thermal compression.
A special note must be made of the crossover design, frequencies and slopes. Starting from the bottom, both woofers operate from the tuning frequency to 400Hz at which point the bottom woofer fades out by way of a first-order (6dB/octave) low-pass filter. The upper woofer/mid continues up to a highish 2,500Hz crossover point (24dB/octave) at which point the 176ND horn takes over until it crosses over to the super tweeter at 8kHz. I didn't detect any beaming from the upper 8" mid/woofer as might be expected around the 2,500Hz crossover. Minimizing the potential for beaming is one reason the crossover has steep slopes at this point.
The JBL LS 120P powered sub features a 12" Polyplas® driver in a ported enclosure. It has line level inputs (no speaker level ins or outs). It has a volume control, a low pass filter control and a 0^/180^ phase switch. The amplifier is rated at 400W RMS. Its cabinet is actually a little smaller than I was expecting, but the port is very large diameter and makes a nice handle when moving the sub.
These speakers are available in two real-wood veneer finishes: either black gloss or a streak-ebony finish. My review units were streak-ebony and, as mentioned before, they were downright gorgeous. JBL claims that it takes three weeks to build each cabinet. There are several layers of lacquer and lots of hand sanding/rubbing that goes into the finish. The technique is very similar to the way guitars or fine furniture are finished. The speakers have rugged textured black surfaces on the top, front and back. This is very handy when you have parties and someone leaves a cocktail glass on the speaker . . . no rings!