Positive-Feedback-v2.qxd 6/30/99 11:18 AM Page 1 Version 2 .
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 1Version 2Positive Feedback The Advantages of FBX Feedback Exterminators Automatic feedback control More wireless mic mobility Louder & clearer sound systemsINSIDE:Feedback andthe FBX:the wholeStory of Feedback1Equalization2The FBX Solution3Glossary of Tech Terms5Applications9True MobilityTMWireless15storyPage 1Adaptive Audio Products17Who Uses FBX19Real-lifeexamplesof the FBXin usePage 9"No one's ever taking thePOWER-Q off me. It's weldedTheentire FBXinto the (Spice) rack!"– Mike Dollingproduct linePage 17
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 2The Story of FeedbackBy Doran Oster, PresidentEver since Lee DeForestinvented the first vacuumtube, engineers have walkedthe tightrope between feedback and system gain. Thepurpose of this guide is to giveyou the tools to get all thegain you need without theagony of feedback. We’ll startwith a common-sense discussion of the techniques soundengineers now use to controlfeedback to get the most gainand clarity out of their soundsystems.Our imaginarywork benchImagine a mic and speakers set up in a tiny showerroom. Clap your hands. Thesound reverberates back andforth between the tile wallsand floor. Just a touch of thevolume fader fills the roomwith screeching feedback.Now move our sound system out to an openFig. 1:grassy field. Clap yourhands. There is noecho. The speakers arewell away from themicrophone and thereare no reflections, sonow we can really crankup the system without abit of feedback.Most sound systemshave characteristics thatfall between these twoexamples, but examining the extreme cases makesit easier to understand themore common in-between situations.1What is acousticfeedback?Feedback is the loud ringingsound that occurs when thesound leaving a speaker ispicked up by a microphone andreamplified again and again.(See Fig. 1.) The cycle repeatsuntil the feedback reaches thesystem’s maximum loudness oruntil someone turns down thevolume. Virtually every soundsystem that has a microphoneand a speaker in the same roomis susceptible to feedback.Which frequencies feedback? All acoustic systemshave distinct resonant frequencies. Regardless of where youthump a guitar’s top, it alwaysresponds with the same tone.This is the natural resonant frequency of the guitar. It is thefrequency where all of theinstrument’s componentsvibrate naturally as a unit. Insound systems, these resonantpoints are the frequencieswhere feedback occurs.Feedback LoopEach of the system’s components, including and especially the room itself, has its ownset of resonant frequencies.Each component adds together to produce the total system’s resonant frequencies. Itis almost impossible to predictwhich frequencies will feedback without first “thumping”the system, but you only haveto turn up the amp for them torudely reveal themselves.The frequency that feedsback first is the one thatrequires the least amount ofenergy to excite the resonance.If you remove the first feedbackfrequency, the next feedbackfrequency will be the one thatrequires the second leastamount of energy, and so on.Controlling feedbackIn order for feedback tooccur, the amplifier has to beturned up enough so thatsound from the speaker reenters the microphone louderthan the original sound. In ourimaginary experiment, feedback easily occurred in theshower room because thesound leaving thespeakers did notdissipate verymuch before reentering themicrophone. Butwhen we movethe speakersaway in the openfield, the soundenergy dissipatesas it radiatesaway from thespeakers. If thereare no surfaces to reflect thesound back to the mic, thesound quickly loses energy,dropping to one quarter the
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 3EQUALIZATIONenergy every time the distancefrom the speakers is doubled.By the time the sound finallyreaches the microphone, thesound energy is weaker thanthe original sound, so there isno feedback. From this example we deduce the PrimeDirective of Feedback Control:Keep the sound emanating from the speakers awayfrom the microphones asmuch as possible.Here are the most common tricks of the trade forcontrolling feedback: Stand close to the microphone. Speak loudly andclearly so that you do not haveto amplify the sound too much. Each open microphonehas a chance to feed back.Mute or turn down the gain ofany microphone that is not inuse. Noise gates can be helpful for this. Mount the microphones infixed positions. Moving themicrophone around on thestage increases the chancesthat the microphone and thespeaker will form new resonantpaths. Use cardioid or hyper-cardioid microphones, and pointthe mics away from thespeakers. They pick up muchless sound from the back sideof the mic, which protectsagainst monitor feedback. Becareful not to put your hand onor too close to the microphone’s screen, since this cancover the ports that enable theheart-shaped (hence cardioid)rejection pattern. Place the speakers in frontof the microphones so thereis not a direct path back to themicrophone. Aim the speakers so thesound does not reflectdirectly off a wall back intothe mic. You can estimate thespeaker’s dispersion pattern(the area that is directly“sprayed” with sound) for themids and high frequencies byimagining rays of light radiatingout of the speaker’s horns. Ifyou can see the center part ofthe horn, you are probably inthe dispersion pattern. Lowerfrequency sounds tend to radiate out in all directions from allsides of the speakers. Make the surfaces of theroom as sound absorbent aspossible to reduce soundreflections. Use acousticalabsorbing tiles in the ceiling, putdown carpeting, and hangcurtains.In the real world of mostperformance spaces, you cannot always follow these antifeedback techniques. Leadsingers insist on pointing themonitors directly at the mic.Worship leaders insist on themobility of a wireless microphone, and night club ownerswill not likely carpet the dancefloor and hang velvet curtains.Even after you’ve tried all thesetricks, you may still not haveenough gain and clarity to satisfy the audience. Do the bestyou can, and then go on to thenext level of feedback control:equalization.EqualizationEqualizers (EQs) are setsof filters, or volume controls, fordifferent parts of the audiospectrum.Since the earliest days,sound engineers have usedequalizers for two distinctly different purposes: 1) To improvethe tone quality and balance ofthe sound, and 2) To controlfeedback for extra gain andmicrophone mobility. Sometypes of EQs are best at shaping the tone and other types arebetter at controlling feedback.It may seem paradoxical toadd filters to a sound system inorder to increase the gain. Butif you can use extremely narrowfilters to turn down the frequencies that are feeding back, youwill be able to increase the gainof all the other frequencies for atotal net gain. There areessentially three categories ofequalizers: graphic, parametricand adaptive parametric.Graphic EQGraphic EQs are basicallya set of volume controls forindividual sections of the audiospectrum. The earliest musicequalizers were the bass andtreble tone knobs. As technology advanced, these filters werenarrowed to give more precisecontrol. Today, the industrystandard is called a 1/3-octavegraphic equalizer, which has 31individual volume controlsspaced 3 per octave.There is a common misconception in the industry about1/3-octave EQs that is important to this discussion. Manyindustry veterans incorrectlypresume that 1/3-octave EQsuse 1/3-octave wide filters. Ifthis were the case, the EQ filters would not be wide enoughto create smooth curves.Instead, they would produce anotched frequency responsethat would make the EQ useless for shaping the sound anduseless for controlling feedbackfrequencies between the sliders. Actually, most manufacturers use 3/4 to 1-octave wideoverlapping filters placed on1/3-octave center points. Thesewider filters provide the necessary smooth frequencyresponse. (See Fig. 2.) It’simportant to understand thatthe term “1/3-octave” refersto the spacing of the sliders,not the filter width.Graphic EQs are excellentfor shaping the sound, and theyare fairly simple to use.However, using one-octavewide EQ filters to control feed2
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 4THE FBX SOLUTIONback invariably causes anunnecessary decrease in thegain and fidelity of the program.It’s easy to see that if feedbackoccurs somewhere between thesliders, you will have to pull oneof those EQ sliders down prettyfar to eliminate feedback. Thatpulls out plenty of your program,too. On the other hand, you’llget considerably more net gainand much better sound quality ifyou use wide graphic EQ filtersfor tone control and insist onnarrow filters for feedback con-trol. (See Fig. 3.) That’s whereparametric EQs come in.Parametric EQIn the quest for perfectsound, engineers developedvery narrow tuned filters forcontrolling feedback points inauditoriums. In the early daysof sound reinforcement, thesefilters were custom made to aspecific frequency and width fora specific application. Nowthere are a number of commercially available parametric filtersets that allow engineers to dialFig. 2: Graphic EQTypical Graphic EQ:-10 dB cut at 500, 630, 1K, 1.25K, 1.6K & 2K Hzin the width, center frequencyand depth of the filter.The problem with parametrics is that they’re expensive, they require a good dealof expertise and auxiliaryequipment to tune properly,they require constant retuningwhenever the room acousticschange, and they are far tooslow and cumbersome forcatching feedback that occursduring the program.Adaptive Parametric:The FBX SolutionThe Sabine FBXFeedback Exterminator is thenext step in the evolution offeedback control. The FBX isessentially a self-tuning parametric EQ. It constantly monitors the program, searching fortones that have the overtonesignature of feedback. Oncefeedback occurs, the FBXautomatically places a verynarrow, constant-width filterdirectly on the feedback frequency and lowers it just deepenough to eliminate the ringing sound.The FBX out performsother EQs five ways:If the graphic EQ really had 1/3-octavefilter widths, the frequency responsecurve would vary 6 dB between sliders.This would ruin the sound.1. The FBX finds and eliminates feedback automaticallybefore and during the program.2. The FBX’s narrow filterseliminate feedback without losing the fidelity of the sound.3. The FBX is fastest. It typically finds and eliminates feedback in less than one second.Graphic EQ’s usually use oneoctave wide overlapping filtersthat provide much smoother frequency response curves. Noticethat the overlapping filters addtogether to cut -16 dB when thesliders are only pulled -10 dB.4. The FBX gives the mostgain. Use wide-filter graphicEQs for controlling the shapeof the sound and narrow FBXfilters for controlling feedback,and you’ll typically achieve a 6to 9 dB increase in gain compared with using the EQ alone.5. Increase wireless mic mobility.3
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 5THE FBX SOLUTIONWhat about that 6 to 9 dBincrease in gain? Gainincrease from equalization really depends on the characteristics of the sound system andthe room. Returning to ourimaginary system in the showerroom, the sound bounces offthe hard tile surfaces andreflects back into the microphone with only a slight touchof the volume slider. If you filter the first feedback point, youcan only increase the volumefader a touch more before thesecond feedback occurs at anew frequency. Even if you filter six different resonancepoints, you may only achieve 1or 2 decibels of net gainbecause there are so manylow-energy resonant paths.When we set our system ina large open field and thespeakers are far away from themicrophone, we really have tocrank it up before we hear thefirst feedback. We would needan enormous system to drivesix feedback points. In thissystem, damping six feedbackpoints could easily deliver wellover 15 dB net gain!How much gain do youachieve with the six FBX filters? Six resonance pointsworth - whatever that happensto be in your unique system.You can maximize your gain byfollowing our anti-feedbackdirectives and by learning moreabout how the FBX filters workbest for your situation.Microphone MobilityMobile karaoke and wireless microphones present aspecial feedback challenge. Itdoes little good to set a numberof filters for a mounted microphone if you plan to carry themic around the stage to different locations. Each position onthe stage has its own uniqueset of resonant frequencies, sothe filters that control feedbackin one location will probably notprovide much help in otherlocations.You are faced with a balancing act. If you insert toomany filters in the system, youwill hear a degradation of thesound quality. If you set toofew filters, you will not haveenough mobility or gain.move. These filters provide theinitial maximum gain beforefeedback and are set automatically during setup. Dynamic filters can release and move tonew feedback frequencies andare for adaptive feedback control during the performance.You can change the number offixed vs. dynamic filters usingFig. 3: FBX vs. 1/3-Octave Graphic EQIn this case, it is usually bestto walk around the stage areauntil you find an area wherefeedback is a particular problem.Then place one or two feedbackcontrol filters to take care of thatlocation and repeat the processin the next few areas. FBX filters add less gain to mobile systems than to fixed microphonesystems, but they add a significant increase in the usable areawhile preserving the naturalclear sounds.Feedback ControlDuring the ProgramOne of the most powerfulfeatures of the FBX is that itcan eliminate feedback duringthe program. FBX filters comein two types: fixed and dynamic. Both filters are placed thesame way: Feedback is detected, and the filter is placed justdeep enough to eliminate it.The difference comes after thefilter is placed. Fixed filtersremain on the initially detectedfeedback tone - they do notA PA System was setup using a microphone, mixer, FBX,power amp and twospeakers. The system’s gain was raiseduntil the FBXremoved nine feedback points. Next theFBX was replacedwith a graphic EQ.The EQ was adjustedwhile the system gainwas raised to thesame level achievedwith the FBX. Thefrequency responsecurves of each devicewere then plotted.front panel controls.Hearing is BelievingTo hear the difference foryourself, insert an FBX in yoursound system and bypass it.Mount the mics on stands to fixtheir positions. Remove asmuch feedback as possibleusing your normal method withjust the graphic EQ. Next, lowerthe volume, bypass the graphicEQ, and activate the FBX. Nowslowly raise the gain of the system until at least six FBX filtershave kicked in.Next, turn down the micsand play your favorite CDthrough the system. Alternatelylisten to the system with just theFBX and then just the graphicEQ. You will hear the FBX provides much clearer, brighter andlouder sound.If you do not have immediate access to an FBX, run thisexperiment with a graphic EQalone. You will be amazed tohear what it does to your sound.SEE THE GLOSSARY ON THE NEXT PAGE (p. 5)FOR DETAILED EXPLANATIONS OF SOME OF THETERMS USED HERE.4
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 6TECH TERMSGLOSSARY:Definitions of“tech” termsWhat is Gain?Gain is a measure of thechange in power (or loudness)in a sound system. For example, turning up the amp causesan increase in gain, while moving away from the speakerscauses a decrease in gain. Byconvention, gain is expressedin decibels.TMClipGuard AdaptiveClip Level ControlSabine’s ClipGuardTMmakes FBX feedback controlfaster and easier to use, andit adds about 10 dB to theeffective dynamic range. UntilClipGuard, engineers manuallyset the input and output levelcontrols to a compromise setting that causes unnecessarynoise during quiet programsand risks clipping overloadduring high level programs.Now ClipGuard constantlyreadjusts the FBX’s electronicsto match the continually changing program levels.Another feature ofClipGuard is TURBO modethat cuts the time of the preprogram setup to just a fewseconds. ClipGuard is currentlya standard feature in Sabine’sFBX-1020P & 2020P FeedbackExterminators, POWER-QADF-4000, GRAPHI-Q,DQX-206 parametric EQ/delayand the REAL-Q2 Real-TimeAdaptive Equalizer.Noise Gate/Comb FiltersAs we mentioned earlier,every microphone creates apotential source of feedback,5so it is advantageousFig. 4:to turn off microphonesthat are not currentlybeing used. Noisegates do this automatically by continuouslymonitoring the program’s loudness. If theloudness falls below athreshold set by theuser, the noise gateautomatically turns offthe microphone. Oncethe loudness exceedsthe threshold, themicrophone channel automatically turns back on.Noise gates are useful fora number of important soundapplications besides feedbackcontrol. For example, if a person or instrument is picked upby two microphones placed indifferent locations, the combined mic signals will interferewith each other, causing a typeof distortion called comb filters.Comb filters add gain at certainfrequencies and thus increasethe chance of feedback. At thesame time, they cut the gainat other frequencies, causingthe program to sound thin andover-equalized. Gating theLoudness in Decibelsunused microphones eliminatesthis source of comb filtering.Noise gates are oftenemployed in CD players toeliminate noise between songs.They are similarly used insound systems to mute the hissof noisy electronic componentsduring quiet periods.Most Sabine FBXFeedback Exterminatorsfeature user-progammablenoise gates.What are Decibels?We have the ability to hearan amazing range of loudness.People placed in an absolutelyquiet anechoic chamber eventu-Fig. 5: Typical Frequency Response1K EQ slider pulled down 12 dB
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 7TECH TERMSally perceive the sound of airmolecules hitting theireardrums. On the other hand,people working near jetengines hear sounds a billiontimes more powerful.Engineers have developed aconvention that economizesthe calculations of such anenormous range of values.This convention describesthese changes in terms ofdecibels (abbreviated dB)named in honor of AlexanderGraham Bell.Many non-technical peoplefind the different uses of theterm decibels confusingbecause it seems to have somany different meanings. Forexample, decibels are commonly used to describe theloudness of a sound, thechange in loudness (or gain)from one time to another, forchanges in signal voltage, anda number of other technicalmeasurements involving thepower ratio of large numbers.While we gladly leave thesecalculations to the engineers, itis helpful to realize that achange of 1 dB is equivalent toa 27 percent change in power.With this in mind, we realizethat turning up the system gainby 3 dB increases the powerapproximately 100% (27% x 3).In other words, turning up theamp from 400 Watts to 800Watts adds about 3 dB to thesystem gain.Wow! Does doubling thepower from 400 Watts to 800Watts make it sound twice asloud? No! A three decibelchange sounds only slightlylouder. In general, you have toincrease the power about 10times (or 10dB) to make thesound seem twice as loud.When engineers describethe loudness of a sound interms of decibels, they arecomparing the sound pressurelevel of a particular sound compared to an international standard. Fig. 4 gives several common reference points.FrequencyResponse CurvesA frequency responsecurve is a graph that shows thegain of a component or a groupof components at different frequencies. Fig. 5 shows the frequency response of a typicalFig. 6: Typical Frequency ResponseTwo overlapping EQ sliders pulled down 12 dBequalizer with the 1,000 Hzslider pulled down 12 dB. Thefrequency response curveshows that the biggest cut inpower, called the center frequency is at 1,000 Hz, that thefilter removes half of thepower (-3dB) between 645 Hzand 1550 Hz, the Q of the filter is 1550-645 Hz/1000 Hz(.905), and the maximumdepth is -12 dB.Fig. 6 shows the frequencyresponse of two adjacent sliders pulled down 12 dB. Noticethat the center frequency of thetwo sliders is at 885 Hz. Thecombined filter width is 1.49octave and the two filters addtogether to give a maximumdepth of -19.3 dB.Constant-Q FiltersIt is common to describe afilter’s quality factor, or “Q,” asthe center frequency of the filterdivided by the filter width (inHertz) measured at the -3dBpoint. Filters that have thesame Q, or width, at the -3dBpoint regardless of the filter’scut or boost are called constantQ filters. Filters that get wideras the filter gets deeper arecalled proportional Q filters.There seems to be a newdevelopment in the audioindustry. The definition of constant Q is blurring. Manyequalizer manufacturers claimtheir equalizers have constantQ filters, when in fact they getsubstantially wider as they getdeeper. The only way to knowfor sure if the filters are trulyconstant Q is to inspect theirfrequency response curves.(See Figs. 7 & 8.)Net GainBefore FeedbackMany people measure theirincrease in gain by the amountthey push up the mixer’s calibrated slider. But if adding gain6
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 8TECH TERMSFig. 7: Typical Constant Q Filtercauses feedback, you willhave to cut the gain of thefeedback frequency at the EQin order to add gain at themixer. A more accurate concept could be called NET gain.It is the amount of gain youachieve pushing up the mixerslider, minus the gain you loselowering the EQ sliders. NETgain is the gain you realize infront of the speakers as measured by a sound pressurelevel meter. That is the gainthat matters. (See Fig. 9.)The FrequencySpectrumFig. 8: Typical Proportional Q FilterFig. 9: Net Gain Mixer minus EQ7People with excellent hearing can hear frequenciesbetween 20 and 20,000 vibrations per second or Hertz. Fig.10 shows an imaginary 120key keyboard that would bebig enough to play all thenotes that we can hear. Thelowest key would play a 20 Hz“E” and the highest key wouldplay a 19,912 Hz “D#.” Noticethat doubling the frequencyraises the pitch one octave.We hear the same one-octavemusical interval between 40and 80 Hz as we do between10,000 and 20,000 Hertz.A graphic equalizer issuperimposed that showswhich sliders affect the notesof several instruments. Forexample, the chart shows thatthe 250 Hz slider affects mostof the bottom 1/3 of a guitar’srange.The typical FBX filterbelow the EQ shows the relatively smaller size and effecton sound of FBX filters andillustrates why they cause lesstonal change and gain loss.The nine FBX filters arenot preset on any particularfrequencies like EQ filters.They are placed preciselywhere feedback occurs.
Horizontal bars showpractical ranges ofmusical instruments.Light gray shaded areashows tones affectedby one graphic EQ filter(250 Hz). Note largegaps in response ofmany instruments whenjust one EQ fader ispulled! Compare this tothe much narrower areaaffected by one FBX filter (dark gray bar).Fig. 10: The Frequency Spectrum 1997 Sabine, Inc.Positive-Feedback-v2.qxd6/30/9911:18 AMPage 9TECH TERMS8
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 10APPLICATIONSP OWE R-QSixteenchannelsof monitors:ChrisTrimby &TFI FridayChris TrimbyEvery Friday evening at 6:00all of Britain celebrates the startof the weekend with the hit television show "TFI Friday."Hosted by star Chris Evans, TFIFriday features an informal "bigbar" setting as a backdrop forentertaining conversationbetween host and guests, plusthe occasional musical act.Adding to the normal mayhemand stress of a weekly televisionproduction is the fact that theshow is broadcast live to millions of devoted fans. Then consider that Chris and his guestslike to wander around the setduring the course of their conversations – with their lavaliermicrophones amplified to quiteloud levels for monitoring purposes. Finally, throw in not justone, but three sound stages forlive music, and you might think asound engineer in charge ofsuch a setup would long wistfullyfor a carefree career as a professional mine sweeper or someother less stressful occupation.Not so Chris Trimby, monitorengineer extraordinaire, incharge of 16 monitor mixes forTFI Friday. Chris, whoseLondon rental company ENTECsupplies all the sound requirements for the show, has madehis demanding job far lessstressful by harnessing a total ofeight Sabine POWER-Qs (plus 2in rotational duty), all controlledfrom a central computer station."The POWER-Q containsevery possible bit of informationyou could ever need to detectproblems and then put them rightin a fraction of the time it wouldhave taken using traditionalmethods," states Chris. "Set-uptime for the POWER-Qs isremarkably fast. Via the PC, allthe machines copy to each other,so once one is programmed,they can all be preset. By thetime the show airs on Friday, Ican virtually put my feet up! Iget an extra 9 dB of gain beforefeedback! It's a real joy to mix."Chris uses all the features ofthe POWER-Q, but especiallyfinds the EQ and powerful FBXnotch filters useful in preventingany surprises during the show'slive broadcast. He also uses theunit's delay, compression, limiting, and Real Time Analyzer andcurve display. Chris finds thepotential uses of the POWER-Qalmost limitless. "I am discovering new ways to manipulate thesystem all the time," claimsChris. He describes thePOWER-Q's flexibility as anabsolute essential in live television, where the limits are alwaystested and new problems are aconstant challenge. "Sabine’sPOWER-Q is the perfect tool forthe job."Thanks to Kiera Leeming ofFuzion, Sabine's UK distributor,for her assistance in compilingthis information.9
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 11APPLICATIONSSabine's adaptive audio products provide a gentle but powerful application of technology tosolving acoustical challengespresented by both historic houses of worship, and brand new,modern facilities. That's whyyou'll find the name "Sabine" inuse all over the world, in placesof worship of all shapes, sizes,and denominations – from thehuge scale of the Vatican inRome (GRAPHI-Qs and FBXs)and the Grand Mosque in Mecca(a rack full of FBX-1020Pluses),to small churches and modestministries.Somewhere in between thelargest and smallest house ofworship is the 2,200-seatAssembly Hall of the Jehovah'sWitnesses in Daytona, Florida.Here Sabine's POWER-Q provides feedback-free sound andworry-free operation, perfectlysuited for quiet contemplation orfestive celebration.Contractor Larry Kommers ofSight & Sound in Laurens, SCcalls the POWER-Q a “powerfuland essential” piece in theAssembly Hall's sound system."We chose the POWER-Qbecause we knew we could usethe equalizer, the FBX FeedbackExterminator , the compressor/limiter and the real-time analyzer– without a bunch of boxes allhaving to be converted back andforth from digital to analog. Itmakes for a much cleaner installation," asserts Kommers.The Assembly Hall installationmakes good use of the POWERQ many functions. "We are usingparametric EQ, graphic EQ, theFBX and the compressor," statesKommers. "And of course weused the auto-EQ function to setit up. We also use the displayscreen on the POWER-Q tomonitor what's going on in theaudio signal," he continues.The POWER-Q's ease ofoperation also helps assureagainst system failure. Kommersinstalled two completely identical,redundant systems into the mainauditorium. "Now these systemshave to be dead equal to eachother," states Kommers. pointingto the POWER-Q precision asanother reason to buy one. "Withthe POWER-Q, we can very easily get the exact same equalization, exact same compression,and the exact same configurationfor the sound on each of them.During the program we can hitthe switch to go from standbyand the audience will never hearthe switch – never detect that itis now going through differentequipment."The POWER-Q is not the onlySabine equipment installed within the Assembly Hall. Kommersused a Sabine FBX-1020Feedback Exterminator for thestage monitors – making surethat "the people on the stagecould hear what the audiencewas hearing – without causingany feedback."POWER-QFBX-1020PlusUsing theFBX inchurches:DaytonaBeachAssemblyHall of theJehovah’sWitnessesWilliam HeienAssembly Hall ManagerSince the Assembly Hallopened its doors in January,1999, the sound system hasreceived nothing but praise."We are delighted with thesound," says William Heien,manager of the Daytona BeachAssembly Hall of Jehovah'sWitnesses. Kommers has hadrequests from other similarfacilities – one in New YorkState, one in Pittsburgh andanother one in Florida – to lookover their systems and giveadvice. Not surprisingly, “we aregoing to recommend usingSabine," asserts Kommers.10
Positive-Feedback-v2.qxd6/30/9911:18 AMPage 12APPLICATIONSGRAPHI-QGRQ-3102GRAPHI-Qon BoardGRQSavesFerry fromStructuralOverhaulIb SigismundThe quest for bigger and better almost put the Danish ferryboat Christian IV in for structuraloverhaul – that is, until Sabine'sGRAPHI-Q was called in to solvethe problem.The nightclub on the ChristianIV offers such a powerful soundsystem that the bass frequenciesenjoyed by its patrons were disturbing the sleep of passengersthree decks away. The club'smetal stage, and an array of subwoofers placed underneath it,combined to act as a huge reso-11nant chamber, and the thud ofbass drums and other low frequencies were being transmittedto distant decks through the hullof the ship.Musik Huset Hjorring (MHH),the installation contractor, proposed a solution that wouldrequire difficult and expensivemodifications to the stage construction. Fortunately, prior totheir undertaking such costlyaction, they called Ib Sigismundof Ascon, the Danish distributorof Sabine pro audio products.Ascon had already providedMHH with 2 Sabine GRAPHI-Qs(GRQ-3102 units) for the installation. MHH was initially attractedto the GRAPHI-Q because of itspowerful combination of features(2-channel compressor, delay,graphic equalizer, parametricequalizer, and of course Sabine'sin
The Sabine FBX Feedback Exterminator is the next step in the evolution of feedback control. The FBX is essentially a self-tuning para-metric EQ. It constantly moni-tors the program, searching for tones that have the overtone signature of feedback. Once feedback occurs, the FBX automatically places a very narrow, constant-width filter
Physics 3330 Experiment #5 Fall 2013 Experiment #5 5.1 Positive Feedback and Oscillators Purpose In this experiment we will study how spontaneous oscillations may be caused by positive feedback. You will construct an active LC filter, add positive feedback to make it oscillate, and then remove the negative feedback to make a Schmitt trigger. .
Positive Psychology, Positive Psychology Parenting, Authentic Happiness Model, Positive Parenting, Positive Discipline 1. Introduction Every single day, about one million adults become parents for first time (Bornstein How to cite this paper: Kyriazos, T. A., & Stalikas, A. (2018). Positive Parenting or Positive Psychology Parenting? Towards a .
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1. Ask for Feedback – on an ongoing basis. Feedback is so important that we have to ask for it if it does not occur naturally. Sometimes we do get feedback, but it is restricted to one aspect of our behavior, and we may have to ask for additional feedback. To ensure that we get feedback the way we’d most easily hear it, we can direct the giver
7 Feedback Most op-amp circuits are designed to use feedback. Feedback is defined as taking a portion of the output of a circuit and coupling or feeding it back into the input. If the output fed back is in phase with the input then the circuit has positive feedback. If the output fed back is out of phase with the input then the circuit has negative feedback.
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fabulas.qxd:Leyendas_Becquer_CAT.qxd 26/4/10 15:22 Página 14. 15 No hay que imitar a la cigarra ya que siempre llega el in-vierno en la vida y nos falta lo que despreciamos otro tiempo. Pero tampoco se debe ser tan poco caritativo como la hormiga, porque compartir las cosas da mucho gusto.
asset management industry, that in the future will need to move these resources within its boundaries. handling compliance some Regulatory challenges In the past few years, regulatory compliance has constantly been at the top of asset manager’s agenda. Currently, the most debated regulation is the upcoming Market in Financial Instruments Directive (MiFID II), as it covers many areas of the .
