xta - djeconcept.djeproduction.com · XTA Electronics Ltd. The Design House, Vale Business Park,...

XTA Electronics Ltd.The Design House,

Vale Business Park,Worcester Road,

Stourport-on-Severn,Worcs. DY13 9BZ.

EnglandTel: 01299 879977 (Intl. +44 1299 879977)

Fax: 01299 879969 (Intl. +44 1299 879969)Web: http://www.xta.co.uk

© XTA Electronics Ltd 05/2006

XTA Electronics Ltd.The Design House,

Vale Business Park,Worcester Road,

Stourport-on-Severn,Worcs. DY13 9BZ.

EnglandTel: 01299 879977 (Intl. +44 1299 879977)

Fax: 01299 879969 (Intl. +44 1299 879969)Web: http://www.xta.co.uk

© XTA Electronics Ltd 05/2006

tax

.If you have any comments or suggestions about this document, please

contact XTA at the address above, or email [email protected]

.If you have any comments or suggestions about this document, please

contact XTA at the address above, or email [email protected]

Some definitions...Low frequency or LF - the “Bass” notes - typically 100Hz or lower.

Mid-range frequencies or MF - the “Middle” notes - typically above 100Hz but less than 10,000Hz.

High frequency or HF - the “Treble” notes - typically above 10kHz.

Low frequencies responsible for weight of sound - bass guitars & drums.

Mid-range covers most instruments, including the human voiceand guitars, brass, strings etc...

High frequencies responsible for “sparkle” - cymbals, clarity ofvoices - things sound muffled if HF missing.

FLATFLAT

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CUTCUT

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BASSBASS MID-RANGEMID-RANGE HIGHHIGH

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FLATFLAT

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More BASS (low frequencies)More BASS (low frequencies)

Adjusting the sound by boosting frequenciesBoosting low frequencies emphasises the bass notes, makingthe sound more “weighty”.

Note that this boost is constant over a range of low frequencies withless and less applied as the frequency increases, until at a certainfrequency, there is no boost applied.

At this point the response is said to be .FLATFLAT

This is known as a Low Shelving Filter, due to its shape resembling a shelf.

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FLATFLAT

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More TREBLE (high frequencies)More TREBLE (high frequencies)

Adjusting the sound by boosting frequenciesBoosting high frequencies emphasises the treble notes, makingthe sound “sharper” or “clearer”.

The response is at low frequencies this time, and more boost is applied at high frequencies.

FLAT FLAT

This is known as a High Shelving Filter, due to its shape resembling a shelf.

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FLATFLAT

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Mid-range BOOSTMid-range BOOST

This is known as a Standard Parametric Filter, not because of its shape, but becauseall three basic filter parameters are adjustable - Frequency, Level, andBandwidth.

Frequency

Bandwidth

Leve

l

Adjusting the sound by boosting frequenciesBoosting mid-range frequencies emphasises the middle notes, making the sound “harsher” or “louder”.

The response is at low and high frequencies this time, with boost applied only across frequencies in between.

FLAT FLAT

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Mid-range BOOST (WIDE Bandwidth) - Bigger rangeMid-range BOOST (WIDE Bandwidth) - Bigger range

The Meaning of BandwidthThe Bandwidth is a measure of how far the effect of the boostextends above and below the chosen .

A WIDE Bandwidth means a bigger range of frequencies are affected - extending further to low frequencies andfurther into high frequencies.

This is always a symmetrical phenomenon - the same to theleft and the right of the chosen .

centre frequency

centre frequency

Centre FrequencyCentre Frequency

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Mid-range BOOST (NARROW Bandwidth) - Smaller rangeMid-range BOOST (NARROW Bandwidth) - Smaller range

Changing the BandwidthA NARROW Bandwidth means a smaller range of frequencies are affected.

Narrow bandwidth filters are useful for picking out certain soundswithout affecting other ones at nearby frequencies - for examplehighlighting a bass drum sound without making the bass guitar unduly obvious.

Lots of relatively narrow filters can be used together to form aGRAPHIC EQUALISER...

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Multiple Bands BoostedMultiple Bands Boosted

Multiple EQ BandsTraditionally the BANDWIDTH of the filters in a graphic equaliserare all fixed at the same value, and their centre frequencies areequally spaced to cover as much of the audio band as possible.

The more bands available, the more accurate the adjustmentsthat can be made.

The standard for a professional graphic equaliser is 30 bandsspread from 20Hz to 20kHz.

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GQ600 DUAL CHANNEL GRAPHIC EQUALISER

+10dB

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25 31 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1K 1K25 1K6 2K 2K5 3K15 4K 5K 6K3 8K 10K 12K5 16K 20K

HI - PASSFILTER

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FREQ(Hz) GAIN(dB) FREQ(Hz) GAIN(dB)

H.F. TRIM IN EQ IN

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Multiple Bands Boosted Low Frequencies OnlyMultiple Bands Boosted Low Frequencies Only

Graphic Equaliser ResponseA GRAPHIC EQUALISER is so called as each slider representsthe level of each of the filters, which combine to give agraphical representation of the response achieved.

Boosting the low frequency sliders as above will produce an affect similar to the low shelving filter seen earlier, and this shapeis represented by the fader positions on the front panel.


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FLATFLAT

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Typical “Full Range” Speaker ResponseTypical “Full Range” Speaker Response

One Speaker for AllCan a single speaker reproduce all the frequencies we canhear at equal level so as to produce a ?

Yes...and no...

This speaker will be able to reproduce frequencies from about100Hz up to 10kHz quite well, but low bass and high frequencieswill not be heard accurately.

FLAT RESPONSE

Is there a way to correct this, based on what we know about equalisers so far...?

FLAT RESPONSE

Is there a way to correct this, based on what we know about equalisers so far...?

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FLATFLAT

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Correcting the Speaker’s Response?How about boosting the parts of the responsethat are too low in an attempt to produce therequired flat response?


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This doesn’t really work!Boosting frequencies that the speaker cannot naturally reproducewill result in wasted power, damaged speakers and lowersound levels than could otherwise be achieved.

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FLATFLAT

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Natu

ral “

Roll-

off” of l

ow

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Natu

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Roll-

off” of l

ow

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s Natu

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oll-o

ff” of h

igh fre

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Na

tura

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ll-off” o

f hig

h fre

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Correcting the Speaker’s Response Properly!The best method to fix this problem is to use multiple speakers,each specifically designed to cover part of the entire audio range.When all heard together, these will be able to reproduce allthe frequencies as required.

First step in ensuring this all works correctly is to cut back all the frequencies that the speaker cannot properly handle.

This ensures it will operate correctly and not be unduly stressed.

To achieve this we use a different type of filter - a high pass or low pass filter.

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FLATFLAT

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Rem

ove

use

less

low

freque

ncie

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Rem

ove

use

less

low

freque

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Re

mo

ve u

sele

ss hig

h fre

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Crossovers - what they do...HIGH PASS FILTERS cut out low frequencies and allow high frequencies to pass;LOW PASS FILTERS cut out high frequencies and allow low frequencies to pass.

These filters only REMOVE frequencies - they cannot boostanything.

Combinations of these filters form what are known as crossovers - the basis of what a DP224, DP226 and DP428 does.

HIGH PASS FILTERHIGH PASS FILTER LOW PASS FILTERLOW PASS FILTER

“Tweeters” reproduce high frequencies, but cannot reproducelow frequencies.

“Woofers” reproduce low frequencies, but cannot reproducehigh frequencies.

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FLATFLAT

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“Woofer” reproduces low frequencies“Woofer” reproduces low frequencies

Remove useless high frequencies that speakercannot reproduce efficiently...Remove useless high frequencies that speakercannot reproduce efficiently...

FLATFLAT

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“Woofer” reproduces low frequencies“Woofer” reproduces low frequencies

Remove useless high frequencies that speakercannot reproduce efficiently...Remove useless high frequencies that speakercannot reproduce efficiently...

LOW PASS FILTER = LOW FREQUENCIES ONLYThe LOW PASS FILTERS cut out high frequencies and allow lowfrequencies to pass.

As the woofer cannot reproduce high frequencies, powerwould be wasted sending them to it.

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FLATFLAT

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“Tweeter” reproduces high frequencies“Tweeter” reproduces high frequencies

Remove useless low frequencies that speakercannot reproduce efficiently...Remove useless low frequencies that speakercannot reproduce efficiently...

FLATFLAT

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“Tweeter” reproduces high frequencies“Tweeter” reproduces high frequencies

Remove useless low frequencies that speakercannot reproduce efficiently...Remove useless low frequencies that speakercannot reproduce efficiently...

HIGH PASS FILTER = HIGH FREQUENCIES ONLYThe HIGH PASS FILTERS cut out low frequencies and allows highfrequencies to pass.

The tweeter cannot reproduce low frequencies: it would most likely be damaged by receiving them, due to low frequencies almost always being much higher powerin a normal audio signal.

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FLATFLAT

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Recombining two responses covers complete spectrumRecombining two responses covers complete spectrum

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WOOFER + TWEETER = !Each output on a crossover will have both low pass and high passfilters to permit only a certain band of frequencies to get through,as appropriate to that speaker’s useful reproductive range.

FLAT RESPONSEFLAT RESPONSE

High and low pass filters are called CROSSOVER filters when used like this, due to the fact that the bands overlapenough to produce a FLAT RESPONSE.

The point at which the bands overlap is called the CROSSOVER point.

CROSSOVERPOINT

CROSSOVERPOINT

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FLATFLAT

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Multiple bands can be used for multiple driver systemsMultiple bands can be used for multiple driver systems

LOWLOW MID-RANGEMID-RANGE HIGHHIGH

SPLITTING THE SOUND MORE...The signal may be divided up into more than two bands - typically 3 or 4 when dealing with a large professional concert sound system.

This is mainly because when high powers are involved (and the requirement for high sound levels), speaker drivers become more specialised over smaller frequency ranges.

This allows their design to be tuned to give higher efficiency and so be louder, at the expense of wide bandwidth - so we need more overlapping over to cover the entire audio spectrum.

DP428 AUDIO MANAGEMENT SYSTEM

= 2 x 4 Way Crossover == Input EQ & Graphic EQ =tax

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