MG ZR Forums banner
1 - 10 of 10 Posts

·
Banned
Joined
·
1,364 Posts
Discussion Starter · #1 ·
this is more of an SQ aimed post but here goes... most probably wont want to go active ever!

ok theres 2 types of way to run a system, passive.. or active. (in this topic we will talk mainly about front componant speakers)

now a passivly run system is the most common, basically your speakers are driven by typically one 2ch amplifier 1 channel for the left and 1 for the right however on an activly run system we would use 1 channel per speaker, so in a system with a 2-way componant set run passivly would be 2 channels, and run activly would be 4 channels, and on a 3-way componant set it would be 2 channes passivly and 6 channels activly

ok, a passvly run componant set requires a passive crossover network, this is the small box you get with your componant set, in a 2-way system it has 1 input and 2 outputs (1 in 3 out in a 3-way setup), now what this little network box does is seperate the frequency of the sound, low and mid frequencys go to the mid higher to the tweeter, we have little control over what goes to the speakers in terms of what frequencys we want them to play this is decided by the passive x-over.

on an activly run system however we have no x-over "box" to control the frequencys as were running each speaker direct from one channel of the amp, however on an activily run system we would have to use a active x-over network, from this control network box, we can set our speakers to play whatever frequency we desire, but within reason we dont want to send frequencys that the speakers cant play to them and inevitably kill them, so we find the frequency range of the speaker and set accordingly, but again there is a general rule of thumb type thing for this but note that some speakers can play alot lower frequencys than others, so its always best to try and find your speakers frequency limits out first.

note: there is a mention of horn in this post if you dont know what one is ignore thats a whole new subject

  • 50hz (usually sub bass)
  • 100hz( usually mid bass)
  • 200hz (either midbass/mid)
  • 400hz (usually mid / large Horn)
  • 800hz(usually mid/horns)
  • 1.5khz (mid/tweet/horns)
  • 3khz (mid/tweet/horns)
  • 5khz(mid/tweet/horns)
  • 7khz(usually tweet/horn)
  • 10khz (tweet/horn)
  • 15khz (tweet/horn)

the benefits of an activly run system over a passivly run system are, the speakers will be getting an equal amount of clean and probably more power, an activly run system can be fine tuned alot more than a passivly run one, you dont have to use a set of componants, you could use tweeters from one set mids from another and mid bass from another!, ultimately an activly run system will perform much much better than a passive system and sound alot better!

there is a hell of alot more to cover on this topic but this is just a basic why choose active over passive thread, as stated at the beggining most of you probably wont get what the hell im on about or wont have the need for an activly run system
 

·
Senior Member
Joined
·
1,626 Posts
I run active :wman:

However as my amp has an adjustable crossover its a pain to set up but when i got it right I got it right :p

TBH it was worth it but cost me £loads because I had to buy double the length of speaker cable and i bought a PG 406a then found out my amp did it"
 

·
Senior Member
Joined
·
1,626 Posts
Hey you should have seen my face £100 plus down and I find out I could have done it with what I had Grrr!!!
 

·
Registered
Joined
·
326 Posts
nitr0genics said:
the benefits of an activly run system over a passivly run system are, the speakers will be getting an equal amount of clean and probably more power, an activly run system can be fine tuned alot more than a passivly run one, you dont have to use a set of componants, you could use tweeters from one set mids from another and mid bass from another!, ultimately an activly run system will perform much much better than a passive system and sound alot better!
lol guess u do have alot of spare time :)

im no audio ethustatic but i am meant to be kinda a specialist in this kinda field specialise in my degree on analogue ic design and power/electrical eng.

now before i go any further quick not that imalazy sod who can't be bothered reading up on my notes so all i say is off the top off my head and might be utter crap!!

now thats a spot on post u wrote there bud. only bit im gonna give my view on is the quote bit above.

active vs passive crossovers has been argued for ages. the little things that make me think.

active is meant to be the best crossover however AC(active crossover) is done before the amplifing stage, my point is in class ab amplifiers (which is most commonly used in audio systems) suffers from crossover distortion due to the push-pull transistor configuration. this adds crap to the signal which is amplified right up without being filtered.

passive solves this problem to an extent by being after the amplifing stage however as all components have a resistance u are adding series resistance to the load decreaseing the power output as more power is lost due to heat waste. and as u use inductors for filtering they suffer from saturation at the high end which adds harmonic distrortion to the signal.

overall they both have good points and bad points.

ps to nitro <-- class a amps are 7% efficent not 90% :guns: if u change the collector resistor to a inductor or transformer u can push the eficency up to about 40 -50 % because u effectively just doubled ure swing.

but after all the good post u done i wont hold it against ya :)

pss i might know all this crap but i still struggle to fit a bloody stereo :( im a pen pusher not a worker :)
 

·
Registered
Joined
·
326 Posts
oooh u gonna make me get ma book out :)

na im 100% certain class a amp have absoultely crap efficency. approx 7% or u induct it 40 -50 % i know they dont go above 50 %

i know they crap effiecny cause they are biased at the half way point which in turn means the transistors are always switched on which insures a perfect sine wave which is y u only need the 1 transistor instead off 2 to get ure sine wave. then u put them in a darlinton confiuration <--think thats what its called to push the hfe right up

excellent quality signal
very crap efficency
 

·
Banned
Joined
·
1,364 Posts
Discussion Starter · #9 ·
i did the checking :p i must be slipping up i confused the efficeny with the quality a pure class a produces
its between 10-20% efficent but the SQ is great

thanks for the correction bleeding SWOT! :p
 

·
Registered
Joined
·
326 Posts
lol gimmie a couple of months and ill forget everything i learned. just rember it the now cause i just left uni this summer probally wont know the difference between current qand voltage this time next year especially in thejob im in the now ZZZZZZZZ... :wallb:
 
1 - 10 of 10 Posts
Top