X-TREME XTD88 User Manual Download

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8. PASSIVE SPEAKERS:

GUIDELINES AND PRECAUTIONS

The Deflector Line comes in both passive and amplified versions.
The passive version contains crossover filters with equalization and
attenuation cells, designed so that transducer channels have a con-
sistent frequency response.
This makes it possible, in particular, to attain excellent sound quality
of 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 active

crossover function in the case of multi-amplification, e.g. with the
XTD1015 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 higher
modules. However, using the processor is useful in all cases in which
the 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 to
control the input tension of the amplifiers, so as not to damage the
passive components present in the speaker with signals that are too
powerful, or otherwise unsuitable for a sound transducer: the follow-
ing paragraph explains

how

and

why

Beforehand,  in  other  words  by  operating  the  amplifier  input  audio
signal, it is clearly not possible to protect the speakers from harmful
phenomena 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 switching
the amplifiers’ upstream devices on or off, may damage the transduc-
ers  if  the  amplifiers  are  turned  on.  As  a  result,  while  turning  on  an
electro-acoustic system, it is important

to switch on the amplifiers only

after power has been supplied to the mixer and the control electronics

and have stabilized; the opposite sequence must be followed to shut
down the system, switching off the power amplifiers first.
Therefore, it is recommended control and maintenance of the audio
installation and the correct on/off power sequence for the devices
present in the audio system.

8.1 Amplification and limitations

In general, too much power frequently causes damage to the trans-
ducer coil, due to the excessive temperature it produces (high RMS
power for long periods), while it only rarely breaks the mechanical part
of the cone (membrane or suspensions). In particular, frequencies low-
er than the reflex tuning frequency may cause excessive excursions
in the cone (which is impractical considering the almost non-existent
efficiency at these frequencies) with resulting damage. For this reason,
it is always advisable to use external processors, which protect the
woofer 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 by
a special filament device. It is the user’s responsibility not to supply a
passive loudspeaker system with signals that harm transducers.
For a precise signal management X-Treme recommends using

XTDP

processors

. The purpose of sizing the amplifiers and limiters cor-

rectly is to reach the maximum passive speaker capacity without
risking damage. In order to have the best performance, i.e. exploiting
the transducers to the maximum at the same time as the peaks in
the signal, a good practical rule is to have a

double powered

ampli-

fication channel (or

over-sized

, as we call it) compared to the RMS

power tolerated by the transducer. To protect the transducer coil, it
is necessary to use a limiter which prevents RMS power from being
overused for long periods.

This  is  the  function  of  the  limiters  in  the  Deflector  series  amplified
models and the XTDP external processors.
Generally  speaking,  an  amplifier  whose  power  is  lower  than  the
one  tolerated  by  the  transducer  (the

down-sized

amplifier) does

not  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 output
signal  “square”  -  this  means  a  higher  level  of  power  compared  to
the  nominal  one  of  the  amplifier  and  the  presence  of  temporary
intervals  characterized  by  continuous  tensions,  which  are  par-
ticularly  harmful  to  the  acoustic  transducers.  The  X-Treme

Digital

Technology Series

class D

amplifiers, recommended for amplify-

ing passive speakers, come with an internal limiter (

anti clip

) which

prevents the signal from squaring. Therefore, if under-sized, they are
a good guarantee against transducer breakages. However, for the
maximum dynamic expression to be reached, as explained above,
using over-sized amplifiers is recommended, limiting the input with
the XTDP processor limiter functions. If used with Digital Technology
Series amplifiers, the correct limiter tools and XTDP processor cuts
are included in the official

presets

set up for such processors by

X-Treme Audio. To calculate the limitation threshold if other amplifiers
are used, X-Treme provides a “

Limiter Calculator

” electronic sheet

with the processor.

8.2 Presets

For 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 parameter
tools for each system configuration shown, in the different versions
with and without subwoofers. These presets can be downloaded
from the www.x-tremeaudio.com website, where the updated ver-
sion is always available. To be able to use these, it is necessary to
make the correct connections between the processor outputs and
the amplification channels: see the documentation provided with the
processor itself.

8.3 Connections between amplifiers and loudspeaker systems

The table sums up the cabling on the inside of the cabinet between
the

NL4 Speakon

connector and the transducers.

PIN 1-

PIN 1+

PIN 2-

PIN 2+

XTD88

Full Range

Negative

Full Range