X-TREME XTD88 User Manual
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User’s manual8. PASSIVE SPEAKERS:GUIDELINES AND PRECAUTIONSThe Deflector Line comes in both passive and amplified versions.The passive version contains crossover filters with equalization andattenuation cells, designed so that transducer channels have a con-sistent frequency response.This makes it possible, in particular, to attain excellent sound qualityof the XTD88, XTD12 and XTD15 speakers, without using an exter-nal processor: all plug and go!It is obviously strictly essential to use a processor for the activecrossover function in the case of multi-amplification, e.g. with theXTD1015 3-way bi-amplified speaker and with all the complete sub-woofer systems. In the latter case, the delay function will also al-low correct sound alignment between the subwoofer and the highermodules. However, using the processor is useful in all cases in whichthe need to protect the speaker is added to the sound quality, ex-ploiting the power output to the maximum, which is really a cru-cial topic in professional sound recording. In fact, it is important tocontrol the input tension of the amplifiers, so as not to damage thepassive components present in the speaker with signals that are toopowerful, or otherwise unsuitable for a sound transducer: the follow-ing paragraph explains how and why.Beforehand, in other words by operating the amplifier input audiosignal, it is clearly not possible to protect the speakers from harmfulphenomena coming from the amplifier itself. If an amplifier malfunc-tion generates continuous tension (DC) or at ultra-low frequencies,this can be harmful to the transducers regardless of the input signal.In the same way, high tension peaks, which are caused by switchingthe amplifiers’ upstream devices on or off, may damage the transduc-ers if the amplifiers are turned on. As a result, while turning on anelectro-acoustic system, it is important to switch on the amplifiers onlyafter power has been supplied to the mixer and the control electronicsand have stabilized; the opposite sequence must be followed to shutdown the system, switching off the power amplifiers first.Therefore, it is recommended control and maintenance of the audioinstallation and the correct on/off power sequence for the devicespresent in the audio system.8.1 Amplification and limitationsIn general, too much power frequently causes damage to the trans-ducer coil, due to the excessive temperature it produces (high RMSpower for long periods), while it only rarely breaks the mechanical partof the cone (membrane or suspensions). In particular, frequencies low-er than the reflex tuning frequency may cause excessive excursionsin the cone (which is impractical considering the almost non-existentefficiency at these frequencies) with resulting damage. For this reason,it is always advisable to use external processors, which protect thewoofer with their frequency cuts and limitations, optimizing efficiency.However, the signal directed to the high frequency drivers in the Deflec-tor line, as in all the other X-Treme models, is protected passively bya special filament device. It is the user’s responsibility not to supply apassive loudspeaker system with signals that harm transducers.For a precise signal management X-Treme recommends using XTDPprocessors. The purpose of sizing the amplifiers and limiters cor-rectly is to reach the maximum passive speaker capacity withoutrisking damage. In order to have the best performance, i.e. exploitingthe transducers to the maximum at the same time as the peaks inthe signal, a good practical rule is to have a double powered ampli-fication channel (or over-sized, as we call it) compared to the RMSpower tolerated by the transducer. To protect the transducer coil, itis necessary to use a limiter which prevents RMS power from beingoverused for long periods.This is the function of the limiters in the Deflector series amplifiedmodels and the XTDP external processors.Generally speaking, an amplifier whose power is lower than theone tolerated by the transducer (the down-sized amplifier) doesnot guarantee that damage will not be caused to the transduc-ers, unless a limiter is used. In fact, even an under-sized amplifier,in correspondence with higher input signals, can make the outputsignal “square” - this means a higher level of power compared tothe nominal one of the amplifier and the presence of temporaryintervals characterized by continuous tensions, which are par-ticularly harmful to the acoustic transducers. The X-Treme DigitalTechnology Series class D amplifiers, recommended for amplify-ing passive speakers, come with an internal limiter (anti clip) whichprevents the signal from squaring. Therefore, if under-sized, they area good guarantee against transducer breakages. However, for themaximum dynamic expression to be reached, as explained above,using over-sized amplifiers is recommended, limiting the input withthe XTDP processor limiter functions. If used with Digital TechnologySeries amplifiers, the correct limiter tools and XTDP processor cutsare included in the official presets set up for such processors byX-Treme Audio. To calculate the limitation threshold if other amplifiersare used, X-Treme provides a “Limiter Calculator” electronic sheetwith the processor.8.2 PresetsFor external amplification with XTDP processors, X-Treme has pro-vided files with extension .dfa (Device Factory Settings) to be upload-ed to XTDP processors, which contain the correct audio parametertools for each system configuration shown, in the different versionswith and without subwoofers. These presets can be downloadedfrom the www.x-tremeaudio.com website, where the updated ver-sion is always available. To be able to use these, it is necessary tomake the correct connections between the processor outputs andthe amplification channels: see the documentation provided with theprocessor itself.8.3 Connections between amplifiers and loudspeaker systemsThe table sums up the cabling on the inside of the cabinet betweenthe NL4 Speakon connector and the transducers.PIN 1- PIN 1+ PIN 2- PIN 2+XTD88 Full RangeNegativeFull RangePositive -- --XTD12 Full RangeNegativeFull RangePositive -- --XTD15 Full RangeNegativeFull RangePositive -- --XTD1015 Low FreqNegativeLow FreqPositiveMid-Hi FreqNegativeMid-Hi FreqPositiveXTDS15 SubwooferNegativeSubwooferPositive -- --XTDS18 SubwooferNegativeSubwooferPositive -- --6/12 |
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