{"id":1583,"date":"2011-08-30T15:28:40","date_gmt":"2011-08-30T05:28:40","guid":{"rendered":"http:\/\/www.bssound.com.au\/wordpress\/?page_id=304"},"modified":"2011-08-30T15:28:40","modified_gmt":"2011-08-30T05:28:40","slug":"pa-systems","status":"publish","type":"page","link":"https:\/\/bssound.com.au\/?page_id=1583","title":{"rendered":"PA Systems"},"content":{"rendered":"

Disclaimer: this was written in 1998 so some of the
\nconcepts and terminology are “Old-School”.<\/em><\/strong><\/h2>\n

TYPES OF PUBLIC ADDRESS (PA) SOUND SYSTEMS:<\/h2>\n

Rough rule of thumb: 5 watts per person in audience<\/p>\n

SIZE \/ TYPE \u00a0\u00a0\u00a0 CHANNELS\u00a0\u00a0   POWER\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0    AUDIENCE SIZE\n\nVocal PA\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0 6 - 12 \u00a0\u00a0\u00a0\u00a0\u00a0  300 - 500 watts\u00a0\u00a0\u00a0\u00a0up to 100 people\n\nSingle 3-Way\u00a0\u00a0 12 - 16\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 1000 - 2000 w\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 around 200 people\n\nDouble 3-way\u00a0\u00a0 16 - 32\u00a0\u00a0 \u00a0\u00a0\u00a0 2000 - 5000 w\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 200 - 800 people\n\nTriple or quad\n3,4, 5-way     24 - 32\u00a0\u00a0\u00a0\u00a0\u00a0  4000 - 10 kw\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 500 - 4,000 people<\/pre>\n
Size and Type of system:
\nThe Size refers to the number of sets of speakers on each side:
\nThe Type refers to how many different sorts of speakers are used<\/p>\n
For example:
\na single 3-way may have: 1 W (bass) Bin, 1 mid bin & 1 Horn\u00a0(treble), on each side of the stage.
\na double 4-way may have: 2 Subs (bass), 2 mids, 2 Horns & 2 sets of Rings (ultra-high) on each side.
\nThere are many variations on this, ie;
\na double 3-way might consist of a total of 4 Sub-lows and 4 Composite 2- way boxes. or a double 2-way might be 8 4560 Bins (low) and 4 horns (hi) The term ?-way refers to how the active crossover splits the sound before the amplifiers feed the speakers.
\nA further example; you could have a system described as being active 3-way\/passive 4-way where an active 3-way crossover feeds 3 sets of amps driving a speaker system that contains subs, mids, horns and rings, within which there is a passive crossover which further splits the hi component into hi and ultra hi between the horns & rings.<\/p>\n
A Vocal P A is generally used for vocals only, ie: the room or crowd is small enough that the instrument amps and drums are loud enough without additional re-inforcement. Except the Kick drum is usually also miked due to its poor position (close to
\nthe floor) and its importance in most music forms.
\nUsualy the speaker system would be a 15″ speaker and 90\u00b0 horn combination, but this is not regarded as 2-way as there is no active crossover involved and only 1 amp drives the speakers.
\n(the term 1-way is not used, the usual descriptive term is full-range box as the speakers handle both low and hi) These speaker boxes would contain a passive crossover which splits the sound low & hi between the speaker and horn.
\nA system such as this could be described as passive 2-way.<\/p>\n
CHANNELS:<\/strong>
\nNumber of channels relates to the number of inputs of the mixing desk. This is usually the maximum number of microphones. In a full mic up you will consider every vocal,
\nnumber of instruments and size of drum kit. For example the following is a typical mic list:<\/p>\n
desk ch.\u00a0 instrument\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 microphone\n\n 1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 kick drum\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Beyer 88\n 2\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 snare drum\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Shure 57\n 3\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 hi hats\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 condensor\n 4\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 rack tom\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Sennheiser 421\n 5\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 floor tom\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Sennheiser 421\n 6\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 over head\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 condensor\n 7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 bass guitar\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 D I Box\n 8\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 bass guitar amp\u00a0\u00a0\u00a0\u00a0 Shure 57\n 9\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 left guitar amp\u00a0\u00a0\u00a0\u00a0 Shure 57\n10\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 right guitar amp\u00a0\u00a0\u00a0 Shure 57\n11\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 keyboard\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 D I Box\n12\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 sax\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 bug\n13\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 left vocal\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Shure 58\n14\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 centre vocal\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Shure 58\n15\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 right vocal\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Shure 58\n16\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 delay return\naux1\u00a0\u00a0\u00a0\u00a0\u00a0 left reverb return\naux2\u00a0\u00a0\u00a0\u00a0\u00a0 right reverb return<\/pre>\n
POWER:<\/strong><\/p>\n
These figures are the most used and abused specifications that you will come across. Since the advent of composite speakers the conventions of classifying in terms of double, single, 3-way, 4-way etc have been going by the wayside. It seems very
\nclear cut to use a number to express the power of a system but you must realise that the Dynamics of a system will be a function of its Efficiency versus its Power. As yet there is no clear measurement of efficiency. Surprisingly the more modern composite systems are less efficient than the larger old style speaker systems, so a 4 kw composite system may be equal to a 3 kw double 3-way in terms of Sound Pressure Level.<\/p>\n
S P L:<\/strong><\/p>\n
Sound pressure level is measured in deci-Bells. this is an even worse can of worms as dB s are measured in a logarithmic scale and the value of SPL measured in dB is also a function of distance from the source.<\/p>\n
PASSIVE \/ ACTIVE:<\/strong><\/p>\n
Another way of describing systems and the way in which the sound is divided between the different types of speakers. A Passive system might have one power amp driving a passive speaker box containing a high frequency Horn, low frequency Speaker and a Passive Crossover which divides the signal within the speaker box. An Active system will incorporate an Active crossover, which is an electronic processor, wired in
\nbefore a number of power amps enabling separate amps to be used for each type of speaker.<\/p>\n
CROSSOVERS (& 2-WAY SPEAKERS):<\/strong><\/p>\n
Capacitors pass high frequencies and resist low frequencies.
\nInductors\/Coils pass low frequencies and resist high frequencies.<\/p>\n
An RLC circuit has a resonant frequency, the resistance of the speaker is a determining factor in the behaviour of a passive crossover.<\/p>\n
The crossover frequency is a point 3dB below where the frequency attenuation drops away or comes back up. This is because it is not possible to stop dead at a particular
\nfrequency, the frequency attenuation curves away according to a slope measured in deci-Bell per Octave. It is difficult to measure the point where the frequency starts to curve away as it starts as a gentle slope, it is easier to measure where it has dropped by 3dB. This point is of significance to us as a drop of 3dB is usually about half the sound power. If both your high and low speakers use the same crossover point you
\nshould have a fairly even response as both speakers are each taking half the power for frequencies surrounding the crossover point.<\/p>\n
A steeper attenuation slope is more desirable as this means that less of the low frequencies go to the high speaker and less of the high frequencies go to the low speaker. A steeper slope is achieved by a more complex crossover circuit. For high powered speaker systems it is more desirable to use an active crossover which is an electronic signal processor operating at line level before the power amps (separate amps for low and high frequencies).<\/p>\n","protected":false},"excerpt":{"rendered":"
Disclaimer: this was written in 1998 so some of the concepts and terminology are “Old-School”. TYPES OF PUBLIC ADDRESS (PA) SOUND SYSTEMS: Rough rule of thumb: 5 watts per person in audience SIZE \/ TYPE \u00a0\u00a0\u00a0 CHANNELS\u00a0\u00a0 POWER\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 AUDIENCE SIZE Vocal PA\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0 6 – 12 \u00a0\u00a0\u00a0\u00a0\u00a0 300 – 500 watts\u00a0\u00a0\u00a0\u00a0up to 100 people Single […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1576,"menu_order":8,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1583","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/bssound.com.au\/index.php?rest_route=\/wp\/v2\/pages\/1583","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bssound.com.au\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/bssound.com.au\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/bssound.com.au\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bssound.com.au\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1583"}],"version-history":[{"count":0,"href":"https:\/\/bssound.com.au\/index.php?rest_route=\/wp\/v2\/pages\/1583\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/bssound.com.au\/index.php?rest_route=\/wp\/v2\/pages\/1576"}],"wp:attachment":[{"href":"https:\/\/bssound.com.au\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1583"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}