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Old 24th March 2005, 07:55 AM   #1
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Default passive radiator ???

hi alll ...
what s passive radiator ???
& what is PA ! ???
lol
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Old 24th March 2005, 10:15 AM   #2
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A passive radiator is actually a different take on the bassreflex system. It's a woofer without a magnet and voicecoil that actually resonates at the resonance frequency of the box it's in.
The passive radiators Fs is mostly very low, it should at least be one actave lower then the box resonance frequency. So tuning is a bit different then a bassreflex system, though it seems less critical then a regular bassreflex system.
I use passive radiators a lot, especialy in two-way system because a passive radiator never has a port-lenght-resonance wich could cause colouration.
Also, the excursion of the woofer is slighlty less when it has to produce frequencies under the tuning frequency then a regular bassreflex system.
There's only one drawback, the roll-off is steeper.

PA stands for Public Adress, these are the system that are mostly used for outdoor events, bands, dance halls etc.
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Old 24th March 2005, 02:44 PM   #3
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Ahmad:

By your other posts, I can see you are a beginner, so I will keep it simple.

The two most common types of enclosures are

A) The Sealed Box. This is a box with no holes in it other than that for the woofer, and any midranges or tweeters you might mount in the enclosure. The mids and tweets have their own separate enclosures behind them, so they don't affect the woofer and main box-for bass purposes, they might as well not be there.

The Sealed Box is also called the Closed Box, the Infinite Baffle, (IB), or the Total Enclosure . All of these are the same.

B) The Ported Box. Also called the Ducted Box and the Bass Reflex-same thing. This is like a Sealed Box only with a duct or port cut into the wall. The hole might or might not have a tube attached onto it. The diameter of the port and the length of the tube, (if any), is very important, since this port tunes the box to resonate at a certain frequency. There are programs that will help you determine the proper diameter and length of the port, and people here who will be happy to use the programs to tell you the correct size.

Change the diameter of the port, or the length of the port tube, and you have changed the tuning of the enclosure and affected the sound of the box.




So what is the Passive Radiator box? As Bombardon stated above, it is variation on the Ported Box. Instead of tuning the enclosure by varying the diameter and length of a port, a Passive Radiator is used. No ports are present in a Passive Radiator box. The Passive Radiator element substitutes for the port. Most often, the Passive Radiator element resembles the actual woofer, with a metal basket, cone, etc. The difference is that it is NOT hooked up to the amplifier.

The cone and suspension of the Passive Radiator is weighted so that it tunes a certain size box to a certain frequency. The speaker builder can also add weight to tune the Passive Radiator himself for which ever box he is building. The speaker builder can also use two Passive Radiators in a box with one woofer, if he chooses. There are people here who can tell you how to add weight to the Passive Radiator, or Passive Radiators, to get the tuning you need for your individual box.

Sometimes, it is easier to use one or two Passive Radiator elements instead of building the proper size port. Details upon request.
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Old 24th March 2005, 09:07 PM   #4
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hi ..& thank u so much ..
yes as u say i m so beginner in the audio & electronic :P ...
thnx for help ...
i have another question ...
i find out that i have to use PA speakers for music instruments ... yeah ???
and if yes should i use PA amps for PA speakers & music instrumensts ??? or if i use an instrument pre amp and connect it to a hi fi amp thats enough ???
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Old 24th March 2005, 11:39 PM   #5
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Ahmad, do you want to make a system for a certain instrument?

I play bassguitar myself, I did build my own system.

So, please tell what kind of instrument you want to amplify, guitar, keyboards, horns, etc.
Some instruments need other requirements then others. A guitar amp e.g. needs a totally different speaker setup then a regular PA system.

If you just want a small practice amp you could use a hifi amp(if it has enough power) with an instrument preamp. I did this too you know, but now I have an old Bell 9024 PA amp to power my bassguitar system. It has more then enough power (2x600 watts 4ohm). But I would recomment a PA amp because they are made for that purpose (build more sturdy).
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Old 25th March 2005, 08:22 AM   #6
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hi
yes ... i m playin bass guitar too ..
wich amp , and speaker u suggest ???
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Old 25th March 2005, 10:23 AM   #7
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Hey! cool man, welcome to the bass community.

What kind of music do you play? Because that also has alot to do with the speakers you may want to use.

My setup has two 10" woofers for the midbass and one 15" for the lows. The Bell 9024 amp has an active crossover so I can use one channel for mid and one for bass. I play mostly funk/jazz/pop/rock.

Just tell me what style of music you play and maybe what kind of bass. That way I can design a system for you.

Also tell me how much money you want to spend.

Just give me as much info you have, I will help you.
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Old 25th March 2005, 02:02 PM   #8
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hi bombardon73 ...
i mostly play metal ( death metal ) or hardrock ... & i own an ibanez sr3005 prestige model w active electronic ( that s really an excelent instrument man ,,, u should try it )
& in fact i don have enough money to buy good speakers or anythin else .. i just wanted to build a box for my bass w two sony car subs and one woofer , but i stop it cuz i afraid it doesnt satsfy me , and waste my money ...
i just ask questions to improve my info ... i never want to buy them still ( may be one day i become reach enough & i ll buy a good series speaker .. but that day is not now :P ) ...
lol ... so i ll be so glad ,, if u tell me what kind of amp and speakers i exactly want .. pa or hi fi ...
thank u so much man ...
what s ur bass ( or basses ) ? ...
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Old 25th March 2005, 03:33 PM   #9
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I have four basses, two I did build myself (a 4 string and a fretless 6 string). The other two are a cheap 4 string I upgraded with EMG pickups and a new bridge and the other is a 6 string from Bassline.

Those Ibanez basses are all great instruments! So the one you have is a 5-string, the low B is what you need for those detuned heavy songs.

If you want raw power (thats what you need with metal) I would use 2 or 4 12" woofers.

You should check out http://www.eminence.com/eminence/pag...s/main12sp.htm

or you can also take a look at these http://professional.celestion.com/gu..._bass/bass.asp

If you need more info let me know
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Old 25th March 2005, 07:01 PM   #10
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hi ..
so are those PA or HiFi speakers ? ...
and what bout Beyma , Peerless , Monacor ??? ...
they have a better frq response range ... and what bout higher freq ???
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