JBL LSR28P and LSR25P Near-Field Studio Monitors


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Background And Introduction

Designers and manufacturers of monitor loudspeakers pursue a Holy Grail all their own: the accurate acoustical representation of the electrical audio signals sent to their speakers. An ideally designed speaker gives voice to an audio signal with no added coloration whatsoever--no EQ bump, no added warmth or brightness. Any coloration or "character" that belongs in a recording should be in the mix long before signal gets to the speakers. The current trend in powered near-field monitor speakers furthers this quest.

By careful design and match of the speaker's internal power amplifier to the driver units, the designer of a powered monitor can effectively "divorce" or remove an external power amp's influence over the drivers' performance and, therefore, the monitor's final sound. This "systems" approach to accurate monitoring and listening started with studio control-room design in the late 1970's, where designers controlled the room's shape, construction materials and placement of the soffit-mounted monitors. In these studio designs, the entire room and speakers are designed to work together as a total system to achieve an accurate sound at a certain focus point. For the most part, engineers were looking for good on-axis frequency response in these rooms...the mixing "sweet spot." With the loudspeakers available in those days, they were lucky to get that! Now, with the wider use of near-field monitors turning any existing room into an instant monitoring work space, the loudspeaker designer must go beyond on-axis performance and insure that the monitor performs well over a wide listening area in most acoustic spaces.

The LSR Philosophy

Linear Spatial Reference, or LSR, is JBL's tag for their measurement and design philosophy. LSR considers many other factors besides on-axis performance. Quoting the JBL LSR manual: "...this includes the direct sound field, the reflected sound field and the reverberant sound field." These are important factors to producers and engineers who make all major mixing decisions such as sound image placement, EQ, balance and timbre within a 30-degree vertical and 60-degree horizontal virtual aperture in front of the monitor speakers. The LSR philosophy was accomplished by a complete top-to-bottom design and rethinking of every component in the powered loudspeaker. From cabinet materials to individual drivers to the final assembly of the die cast parts, the entire line of LSR units reflects JBL' s intent to make a line of monitors in sizes to fit every room and purpose. Their end goal is that sound quality and balance from smaller production rooms, main music mix rooms and larger dubbing theaters will translate well.


The LSR Line

JBL makes several speaker systems in the LSR line.

LSR32 is a three-way system with a 12" woofer.

LSR28P is a two-way system with an 8" woofer.

LSR25P is a two-way with a 5.25" inch woofer.

LSR12P is a 250-watt active subwoofer.

The 32, 28 and 25 speakers all have controls to revoice them to co-exist with an external subwoofer unit. On the front of all of these systems (except the LSR32) are green LED operating indicators that change to red when the system is in clip.

For purposes of this review, JBL kindly sent me two pairs: the LSR28P and LSR25P. Both the 28's and 25's are designed for vertical orientation and I advise not setting them up differently.

The LSR28P is a bi-amplified reference monitor with the 218F's 8" woofer based on JBL's patented Differential Drive® technology. The monitor measures 406mm x 330mm x 325mm and uses a 250-watt amplifier for the woofer and a 120-watt amplifier for the high frequency driver. It is capable of maximum continuous SPL of greater than 108dB at one meter (that 's super loud). The woofer driver uses two 1.5" drive coils to reduce power compression--the driver actually gets quieter and changes frequency response when driven harder and harder. There is a third coil that acts like a "brake," limiting excess cone excursion thus reducing distortion at high volumes. Supported by a soft butyl surround, the cone is made of a carbon fiber composite material that forms a rigid, piston-like mechanism. The high-frequency driver 053ti has a 1" diaphragm and feeds an Elliptical Oblate Spheroidal Waveguide; i.e., a smooth horn with 100 x 60 degree dispersion angle.

The LSR25P is the smallest speaker system in the line and consists of a 5.25" rigid woofer piston with a soft butyl rubber suspension. It measures 17.3 x 26.9 x 24.1cm and uses a 100-Watt amp for the woofer and a 50-Watt amp for the highs. A cast aluminum basket provides heat dissipation for less compression under full power. The entire driver is shielded for use near video monitors and other equipment sensitive to magnetic fields (important especially with the today's computer-based studios). The titanium high-frequency driver has a 1" composite diaphragm integrated with a horn shaped the same as the 28.

The LSR25P monitoring system is expressly designed to provide users of multimedia and digital audio workstations with the same performance monitoring in smaller environments as users glean from of the larger JBL LSR32 and LSR28P speaker systems.

Two Sets Of Speakers

Having two sets of JBL speakers at the same time to A/B is fun. I would expect that the bigger 28's reproduce the lower octaves much better and clearer than the smaller 25's, so buy a subwoofer if you intend the 25's for serious monitoring. The 25's are the ticket for a small surround studios, where you would have five of them around you to do Foley recording, effects or dialog editing. Using the 25's, I certainly did not get the feeling I was missing anything in comparison to the 28's...the 28' s just offer a much bigger, room-filling sound. The 28's are for recording studios' main near-fields in full-sized control rooms while the 25's are for personal space monitoring use, such as a small editing bay.

I had an opportunity to play many CD's I have worked on through both sets of monitors. These are definitely reference monitors because I can hear all the right and wrong stuff going on with these CD's! Wonderfully non-fatiguing, both the 25's and 28's did not flatter or hype the sound at all. There is a remarkable and similar character between both sets of speakers: they are clear and present mid-range quality, not honky and "forward" sounding. I'll call it the JBL sound, and it makes me nostalgic for the '70's, when I was coming up as an engineer. Back in the stone ages, there were really only three monitor choices: the coaxial Altec Lansing 604E; Tannoy Reds or Golds (also coaxial units); and James B. Lansing's multiple drivers. I was always happy with these speakers although eventually (at least in L.A.) the much more powerful JBL systems caught on, especially at the rock and roll studios.


Speaker evaluation I liken to wine tasting: it takes a while to fully appreciate, savor and then form an enlightened opinion. Ignoring that advice, I jumped right into the studio and cut a track using the LSR28P's! After all, I wanted to test them in the world they are designed for.

LSR28P's don't fold under pressure. I had no trouble using the 28's in the control room since they have both line level balanced +4dBu XLR and -10dBv 1/4" inputs. I had my assistant plug them straight into the console monitor outs, and away I went. One caveat: Be careful unpacking and setting up the speakers since both the high-frequency drivers and woofers are fully exposed and easily punctured by probing fingers. The horns and the rear-positioned reflex ports look like good places to grip the speaker when pulling it out of the box but watch out! The accommodating rear panel has an on/off switch, fuse, an AC mains selector and three-prong IEC (International Electrical Connector) mains connector, so the hook-up was simple.

For me, getting drum sounds is the supreme test of near-field monitors. I'm old-school: I get drum sounds with the speakers loud. I find that a lot of powered monitors start to "fold" just as the kit is starting to sound punchy; clip LED's start flashing away, making it difficult to tell what is clipping; the speakers, the mics, mic-pre or the mics themselves. The JBL's did not fold at all and were tireless in reproducing perfectly some of my worst ever drum tones. Fact is, these speakers didn't disguise either my slacker engineering or the "flogged-to-death" drum heads my drummer was trying to squeeze another gig out of. The 28's did great for mixing as well, with plenty of clear bottom end that translated well when I played the mix on other systems. I found it easy to place (pan) tracks, and the flat 50Hz to 20kHz response made balancing and equalizing easy.

I found the 28P's also easy to adjust for various rooms. There is an eight-position DIP (Dual Inline Position) switch on them for tweaking the high-frequency level up or down 2dB above 1.8kHz, adjusting the bass alignment from flat to + or - 2dB and switching input sensitivity from two different presets or from the input level trim pot on the rear panel. If you work in a very dead room with lots of high-frequency absorption, you may want to bump up the high frequencies so your mixes translate to other systems with just as much brightness. Working in a very live and "splashy" room can cause your mixes to translate dull; in these cases, try taking the top end down 2dB and go for more high end when equalizing. I tried all of these switches and I ended up back to the way the units come out of the box: all switches down (flat response). This setting held up in the control room and in my 12x12' listening room at home, which is very convenient for checking mixes.

After I had a good mix together, I hooked up the 25's and found them to sound much the same as the 28's...just a scaled-down version with not so much subsonic extension. Frequency response is rated at 70Hz to 20kHz for these monitors and all elements of the mix remained in the same balance both in tonality and level. The 25's have a front-mounted level control, on/off switch and two reflex ports. I used the XLR input connector (as I did on the 28's) but there is also a RCA jack for -10dBv levels. The DIP switch here has four positions: 80Hz high pass mode for subwoofer use; HF (high frequency) lifted 1.5dB above 2.3kHz; HF reduced 1.5dB above 2.3kHz; and Boundary Compensation. The Workstation Boundary Compensation control adjusts the bass and mid-bass output for better sound and correct spatial response when the monitors are placed adjacent to video monitors on desktops in typical workstation environments.

Either of these LSR systems can fulfill your monitoring needs for any size studio. The LSR28P sells for $1,121 (MSRP) each while the smaller LSR25P's sell for $489 each.

JBL Professional is part of the Harman International network of professional and consumer audio companies. For more information, contact JBL Professional at 8500 Balboa Blvd. P.O. Box 2200 Northridge, CA 91329. Telephone: 818-894-8850. Web to: www.jblpro.com

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