Tech Talk

By An Nguyen, Distinguished Engineer
HARMAN Luxury Audio

Introduction
The JBL L75ms is an all-in-one music system with a classic JBL look, modern audio technologies and acoustic innovations. It is a 2-channel stereo audio system with center fill, which would address the need for replacing all cumbersome audio components with an all-in-one system that provides high quality audio playback from sources such as streaming, gaming and movie sound when connected to a television.

Why the JBL L75ms?
The world of technology has advanced at an incredible pace in the last two decades. Audio is also part of that. Audio playback formats have gone from CD to Hi-Res streaming, while traditional 2-channel audio has progressed into immersive audio, gaming and movies that continue to drive innovations within the audio space. Hi-Res streaming has played a huge role in replacing all playback audio components, which has created a gap that needs to be filled by products such as the JBL L75ms all-in-one system with streaming capability.

• The L75ms is an all-in-one system where left and right channels are positioned closely to each other, which could potentially compromise the stereo image in audio reproduction. JBL solves this issue by a combination of angling left and right channels away from each other and using DSP to enhance the stereo image for music, gaming and movie applications.

The left and right channels in the L75ms are angled at 15 degrees away from each other to take advantage of sidewall reflections in order to enhance the stereo image. The angled baffle also helps to keep the on and off axis frequency responses consistent, which is critical for producing a good sound stage. The L75ms features an “FSX” mode, which expands the sound field to achieve an even larger sound stage. The center mid-range channel helps to anchor the vocal at center of the sound stage. The SFX mode can be accessed via remote control.

Digital Signal Processing based crosstalk cancelation along with time delay (or phase shift) are employed to enhance the stereo image in music, gaming and movie applications (see above diagram for stereo crosstalk cancelation). The L75ms produces a great stereo image/soundstage when placed between two sidewalls and against a rear wall.

• The 5.25-inch low frequency transducer employs a 1.5-inch diameter voice coil with 20mm peak-to-peak excursions for high dynamic output, low power compression and extended bass. Vented pole piece reduces air noise and helps cool the motor structure. Symmetrical field gap improves position dependent magnetic force, which reduces harmonic distortions at low frequency. Copper ring/cap (Eddy-Current ring) reduces the distortions caused by the reluctance force at high frequency and decreases the self-inductance for more output. Aluminum shorted ring (flux stabilizer ring) reduces flux modulations, which reduces harmonic distortions at low frequency. The 4-inch mid-range also employs a copper cap to extend operation bandwidth.

• The L75ms has a total of 350W class D amplification with an innovative feedback circuit for ultra-low distortion. It features pure digital signal path from input to amplifier stage, therefore Digital-to -Analog Conversion steps are no longer needed, which improves distortion and latency. All processing from entire input section including two analog inputs (3.5mm Aux and Phono), DSP, and amplification section are done at resolution up to 192 kHz.

• DSP chip handles two stereo enhancement settings, electronics crossover between drivers, anechoic EQ, limiters, and auto sensing sub-woofer connection. When the sub-woofer connection is detected, DSP unit shifts the HP filter up to an optimized frequency in order for the L75ms to play louder without increasing distortions.

• Music streaming is an easy task using wired or wireless networks via Google Chrome cast or Apple Airplay2. Music from cloud-based services such as Qobuz, Tidal and Spotify can be streamed directly to the L75ms with a simple set-up. In addition, The L75ms also works with ROON and MusicLife app to enhance the user’s experience. By the way, I have curated a Qobuz playlist featuring all the tracks that I used to voice this amazing product.

• The L75ms also employs an HDMI with Audio Return Channel feature (ARC). HDMI provides simple connection to the TV for great movie or gaming sound and eliminates the need for an additional composite audio or optical cable.

Summary
The JBL L75ms All-in-One System is the best of both worlds. It has the JBL classic look along with the sound quality of a hi-fidelity audio system. It is packed with the latest streaming technologies, various digital and analog inputs, and has the dynamics and soundstage that contradicts its size in music, gaming and movie applications. In addition, it is engineered at the Acoustic Center of Excellence at Northridge, California.