Craig Vecchione

Four 1,250-Watt Channels with DSP Processing, but only 22 Pounds? Many of us use powered speakers, but there are a huge number of passive boxes in use, and we need to power them with something. We all like to get more from less, right? Why not have four channels of amplification in a 2RU space? While we’re at it, let’s throw in all the speaker processing needed to drive those amps correctly and safely. And let’s keep it light and small…our backs aren’t getting any younger. QSC has answered this call in a big way with the PLD Series power amplifiers. With maximum 4-channel power ratings ranging from 400 watts continuous (PLD4.2) to 1,250 watts (PLD4.5) these amps can handle most any power requirement we’re likely to encounter. Let’s have a closer look at the PLD 4.5: What You Need to Know • Four amplifier channels feature Flexible Amplifier Summing Technology™ (FAST). FAST allows the total available amplifier power to be distributed across one, two, three or four channels. No need to bridge channels, or waste an unused channel. • Four channels of DSP speaker processing: crossover, parametric EQ, limiter and alignment delay are available on each channel. • 50 user presets and 20 factory presets that can be modified. Different venue and rig settings can be saved and recalled as needed. • Preset Wizard with a selection of settings for commonly used passive speakers. • Universal switchmode power supply with power factor correction allows light weight and can be used with any available power supply from 120-240 volts, 50 or 60 Hz. The IEC power inlet socket is locking, reducing the danger of unexpectedly unplugging the unit mid-show. The power supply is from the fairly legendary PowerLight series amps. That’s nice lineage, to say the least. • 2RU (3-1/2”) height and 16 inch depth, weight 22 pounds. • An LCD display and series of controls allow navigation through the processing menus and displays system status, available voltage, current draw, and amplifier processing configurations. I found these to be fairly intuitive, but navigation speed was limited by the simplified button/knob arrangement. • In four channel mode, power output is 1150 watts (continuous) into 8 ohms, 1250 watts into 4 ohms, and 625 watts into 2 ohms. Yes, power is reduced into 2 ohms due the current limiting protection, which will reduce or eliminate the overheat problems often encountered when running low impedance speaker loads • In 1 channel mode, power into both 8 and 4 ohm loads is 4200 watts, 4250 into 2 ohms, and there’s even a 1 ohm rating of 3700 watts. • Typical distortion is 0.01 – 0.03% at 8 ohms, and 0.03 – 0.06% at 4 ohms, with maximum distortion of 1%. • Gain at the 1.2v setting is 38/4dB • Damping factor is >150 • Maximum input level at 1.2v setting is 3.88v (+14dBu) and at 3.9v setting is 12.28v (+24dBu) • The four XLR input channels can be soft patched to the 6 NL4 outputs to run one channel of amp/output each, or paired up with any combination of amp/output, with or without crossover, limiting, delay, and/or EQ. The ability to use any number of channels and make full use of available amplifier power is pretty neat, and makes the PLD a good choice for users who need the versatility of changing speaker configurations to meet various show requirements. No more swapping amps out of racks or hauling unused amps to that small show. Limitations • The user interface is somewhat hampered by the control knob programming which changes velocity proportional to the speed it’s turned. So a short quick turn does as much as a long slow turn, but it’s hard to judge how far and fast to turn the knob for a given desired change. The result is feeling somewhat disconnected from the control. • A copy feature would be nice to have in order to speed up the creation of multiple channels with identical settings, as would be used for monitor mixes, etc. • I would be remiss if I didn’t mention that it took three tries to get a working sample of this amplifier from QSC. The first two suffered the same problem; both had an “amp boot failure” message upon startup. The first unit was a pre-production prototype that had obviously been around the block a few times, and the second was a production unit. Conclusions My experience with QSC has been that they have very good products and excellent service, so the failures were surprising. As a result of this, the sample unit has been in my possession for several months and many hours have been put on it. Basically I’ve pounded it as hard as possible without abusing it. It hasn’t skipped a beat at all, powering 2 ohm subwoofer loads for hours in hot conditions while also powering the mid-highs. I’m certain the demons possessing the early models have been vanquished. The uses for this type of amp are many. Obviously one PLD 4.5 can easily power a complete club system with two subs and two mid-highs. Another unit would also run the typical four monitor mixes found in many systems. With four channels and complete speaker processing, a club system could consist of two PLD amps in a 4U rack. And of course for the minimalist, one channel on mid-highs, another on subs, and the other two for monitors would make a great bar band rig. Considering what four channels of driverack would cost, plus the cost of four 1200 watt amps, the price is very competitive. Resources Musician’s Friend QSC PLD 4.5 Product Detail Page - MSRP $2,933.33 Street $2,399.99 QSC PLD Amplifier Page QSC Home Page Craig Vecchione is an IT professional by day, and dabbles in pro audio and bass guitar in his spare time. He’s been the moderator of the Live Sound Forum since 2006.

When Mackie released the SRM450 15 years ago, it introduced powered speakers to the masses and quickly became a staple for bands everywhere. The legacy continues with the SRM550 and 650 full-range speakers, and SRM1850 subwoofer. Each model boasts internally braced poplar cabinets with a tough finish, well-placed flush handles, and a steel wrap-around grille. 1600 peak watts of Class D power lets you drive them hard, and Smart Protect™ DSP keeps it protected if you go a little too far. Fit and finish are, in a word, professional. SRM550 - What You Need To Know Equipped with a 12” woofer, this 37-lb., 132dB speaker has a titanium HF compression driver, 15mm wood cabinet, 18-gauge steel grille and is configured for either FOH or floor monitor use. It’s got sturdy rubber feet for both positions, and the monitor position puts the speaker at 60 degrees, which is great for tight stages where 45-degree wedges aim sound at your belt. There’s a 2-channel mixer with additional RCA jacks for media players. Both channels have XLR/TRS combo jacks, signal/overload LEDs and level controls that handle line- or mic-level signals. A separate limit indicator shows if the mix is too hot. The Thru output jack is switchable between Channel 1 only and the full mix, so you can add more speakers to the mix with ease. The Speaker Mode switch lets you choose from four different EQ profiles to tailor response for PA, DJ, Monitor, or Solo use. A feature I haven’t seen on an active speaker but really welcome is the one-button Feedback Destroyer. It’s got four filters with a nice, narrow 16th-octave slice to capture feedback without taking away all your tone. The single control button switches it on/off and by holding it will clear the active filters, which are indicated with four LEDs. In practice it was easy to ring out the speaker, with the usual warning that the process will create short bursts of feedback as the filters recognize and cut it. A switch lets you shut off the front panel indicator light/logo. SRM650 - What You Need To Know The SRM550’s big brother has the same power and controls, but adds a 15” driver for more low-end grunt. It’s still light at 46 pounds, but the bigger LF driver adds punch when the SRM650 is used full range. That punch makes the SRM650 a great choice for those gigs where you want to travel light but still need to hear the bass. Paired with the SRM1850 sub, this speaker can really bring it for DJs and genres that are fueled by dropped-tuned guitars and huge, bass-heavy mixes. As a bassist, I was happy to run sans amp with an SRM650 as my only stage monitor. SRM550/650 Front View SRM550/650 Rear SRM550/650 Rear Panel SRM1850 - What You Need To Know The SRM1850 subwoofer delivers the same 1600 peak watts into an 18”, front-loaded and ported cabinet of 18mm poplar plywood with a 16-gauge steel grille. Weighing in at only 64 lb., it’s easily portable, so the decision to bring it to small venues is a no-brainer. The controls and I/O are simple and complete—two XLR inputs for mono or stereo, a pair of high-pass outputs to feed mid-highs and a full range output pair to daisy-chain to another sub make up the connections. There is a phase normal/invert switch to maximize output when you can’t position the subs in line with your mid-highs, and a stereo/mono switch. The internal digital crossover has two convenient presets for the SRM550 and SRM650, and a variable setting that can be adjusted between 60 and 120Hz. A main output control, limiter LED indicator and the logo light on/off switch round out the controls. The sound is big and present, with enough definition and punch to feel the kick drum and hear the bass guitar’s B and E strings clearly. Some single-driver 18” subs run out of steam early, but the 1850’s 132dB max SPL easily kept up with the SRM650 and 550, even when pushed hard. SRM1850 Subwoofer SRM1850 Rear Panel Conclusion The new SRM speakers have the clarity, high output and flexibility to be your go-to rig for just about any band that calls. From solo performances in a coffee house to full bands in the club, you can bring the SRMs and know you have enough rig for the gig. Resources Buy the Mackie SRM550 Powered Live Sound Speaker at Musician's Friend Buy the Mackie SRM650 Powered Live Sound Speaker at Musician's Friend Buy the Mackie SRM1850 Powered Live Sound Subwoofer at Musician's Friend Learn more about the Mackie SRM Series at mackie.com

Can a digital console offer one-control / one-function mixing? By Craig Vecchione Soundcraft’s Expression Si digital console supersedes the Si Compact line. It’s available in 16, 24, and 32-channel input sizes. With appropriate optional I/O devices, up to 66 input channels can be handled on all three models. All three models share identical feature sets; only the number of channel fader sets and input jacks varies. What You Need To Know 16 XLR mono mic inputs4 TRS 1/4" line inputsColor touch screen interface66 channels to mix possiblePre/Post selection per input per busAES in and outGlobal mode encodersSoundcraft FaderGlow™GEQ on every bus20 sub-group / aux busses4 FX busses8 Matrix bussesLR and C Mix busses4 Stereo Lexicon Effects enginesDelay on inputs and outputs4 Mute GroupsFreely assignable insert loopsHarman HiQnet integration64x64 channel option card slot The mixer employs a concept Soundcraft named tOTEM™”The one-touch easy mix”, which essentially means that one key touch will bring up an Aux, FX or main bus to mix to, configurable on the touch screen, and controllable on the faders. FaderGlow™ colors each fader slot to correspond with the fader’s function as different mixes are selected.Direct Out Gain Stabiliser, “D.O.G.S.” prevents manual gain control changes from affecting the direct out levels, helpful when recording from direct outs or if two consoles are used and share the same stagebox.Copy & Paste allows copying a wide range of functions; channels, mixes, settings such as compression or EQ from one mix or bus to another.Security features allow access to be granted to or restricted from users, from the whole console to selected features.The four fader pages can be customized, such as for inserting a forgotten mic on a fader page.The four mute groups can be set up to control any selectable input for muting, and a group-muted channel’s on/off key will glow red rather than be off to indicate group muting.Graphical EQ is available on every bus, and is controlled by the fader bank, which has alternate markings to indicate frequency and + or- scaling. The center detent feel is reproduced on each fader to mimic that if a GEQ. Limitations Two minor items: The input section has 16 XLR and 4 TRS line-in jacks. There are no RCA connections for media player/recorders. Insert cables need to be XLR, as do direct outs. Generally this isn’t a problem for pros, but anyone moving from a similarly or lower-priced analog mixer will need to change or replace some of their cabling. While the channel EQ offers two parametric midrange controls, the HF and LR are shelving with no Q. Conclusions While I embrace technology fully, when it comes to mixing I’m an analog guy slowly moving into the digital world. For a few minutes I found setup to be somewhat confusing until I “got it”, and from that point on everything clicked. I was able to get an initial mix ready in about the same time it would take with the equivalent amount of analog gear, remembering that the console now has most of the outboard processing gear you’ll find in a large rack. The FaderGlow™ illuminated faders are a good idea. With each mix selection, the fader slots glow to describe that fader’s function. But a cue card with a color glossary would really help anyone new to this console, as there are a lot of colors/functions to remember. The versatility to create different mixes is impressive. The console can be configured for FOH, monitoring, recording, or a combination of functions with inputs assigned freely to aux’s, matrices, effects, inserts, direct outs and of course the left, right and center/mono outputs. Most setup tasks are easy. Fader groups are an exception, and I found it somewhat tedious to set up one or more groups, a function that is quite simple on most analog consoles. But each mix bus is easily brought up with the touch of the mix button, and can be configured via the touch screen controls. Similarly, the matrix and effects buses are accessed via their selection buttons and configured on the touch screen. Each bus mix has the full suite of processing available including compressor, delay, 4-band EQ and BSS graphic EQ. None of the processing has to be assigned to a bus; it’s all available all of the time. The four Lexicon® effects engines have a multitude of options to fully tailor any available effect. Effects are very subjective, but they were pleasing and usable to my ears. The engines are based on the MX400, a popular standalone effects unit. The gates worked as well as any analog rackmount units I’ve used, without any noise or chattering. The compressors were similarly quite good and I found them effective for vocals and instruments alike. The channel/output EQ’s are flexible and effective. A nice feature is that the touch screen can show the channel EQ settings graphically, so this info is available at a glance. Is the prospect of having one control/one function possible? For mixing tasks during a show, pretty much “yes”. The channel Global Encoders used for channel trim, pan and HPF could be argued as the exception…some sound folk might like to ride gain trimmers as much or more than faders, but I don’t know anyone who would use all three after sound check. The small color touch screen is adequate since it is not typically needed during a show…there is no need to access layers of pages whilst mixing a show. It does have the nice feature of parroting the setting changes you make to the channel strip controls. Complaints? Well, more like suggestions for improvement. I’d prefer the LR and the Mono metering to be near the respective faders instead of at the top. Also the monitor level meters are furthest from the monitor level control, with the L/R and Mono meters closer. Identifying input channels at a glance is a problem I haven’t overcome, as the only way to check the assignment name is to Select a channel and look at the touch screen, which isn’t fast enough when you need to access a channel immediately. Scribble tape could be used, but might get crowded on the first two faders that are used for channels 1 & 2, and 15 & 16. Finally, it would be nice if the input XLR’s were XLR/TRS combo jacks, and a couple of RCA jacks or a USB would make connecting a media player convenient. I don’t think it’s a big list for a console with as many features as this. In conclusion, the Expression Si is quite capable of handling virtually any mixing requirement, it sounds great, and the ease of use is very good. While not as intuitively easy to run as a good analog desk, the routing flexibility and immense processing capabilities far outweigh a few usability issues. Even this old analog guy would be happy mixing shows on it. Resources Musician’s Friend Soundcraft Expression Si 1Catalog Page ($4,200 MSRP, $2,499 “street”) Soundcraft Expression Si Page Soundcraft Home Page Craig Vecchione is an IT professional by day, and dabbles in pro audio and bass guitar in his spare time. He’s been the moderator of the Harmony Central Live Sound Forum since 2006.