[HAM] Speakers and frequencies .. what's it all about

[goffmac747 at aol.com]

 I'm curious though if the bass rotor design of a normal leslie will effectively "rotate" lower bass frequencies and not just affect the higher bass frequencies...


 


 

-----Original Message-----
From: benjamin <benjaminmassy at hotmail.com>
To: kziss at ozemail.com.au; hammond at zeni.net
Cc: benjaminmassy at hotmail.com
Sent: Fri, 28 Dec 2007 3:47 am
Subject: [HAM] Speakers and frequencies .. what's it all about










Hello Kon , 

Very nice  to find somebody who respects good music-reproduction within our 
fysical limits of hearing . Me to, I am leaving the scene if it is to loud and 
the risk of eardamage is to high . 

Now about your your Bi amped 925  project : 

First of all the passive 12 db slope is a problem to make with coils and caps 
between the amp output and the speakers , why , because the coils and caps you 
need are loosing a lot of power since they will have to pass high currents and 
these components do have an internal resistor that you will have to take in 
account . plus for 12 db slope you need a lot of coils and caps .... in short : 
to much for what the results will be . Also it will put a difficult load on your 
amps since part of it is capacitive load and the other part is an inductive load 
combined with the speaker impedance , it could give unpredictable results in 
some cases..even burning out your amp by oscilation and if it is supersonic 
oscilation you will not even notice it unless you have attached an osciloscope 
to see what happens; in short  an amp is build for a certain application and a 
certain load that is matched to it ; 

second point : the gain by doubling the power output is only 3 dB louder 
theoretically , practically there will be no noticable gain here if you take 
into account the losses you will have by the passive components between speakers 
and amp 

third point ; do you know why speakersystems are split up in active systems ?  
mainly because of  to avoid DISTORTION  , the distortion that you get is the 
mixing product of different frequencies  and is called intermodulation 
distortion , I give you an example:  if you have two frequencies entering an amp  
like 100 HZ and 2000 HZ  ; since no     amp is completely linear in 
amplification there will be produced mix frequencies and they will be the 2000 
Hz minus 100 Hz  thus 1900 Hz and also the 2000 Hz plus the 100 Hz thus 2100 Hz  
so your amp will produce at the speaker  not only 100 and 2000 Hz but also 
1900Hz and 2100 Hz  plus the harmonics from these frequencies .. if you have 
only harmonical distortion  you have not a big problem since the harmonics are 
sounding ok  ( every octave is the double from the one that sounds lower so 
harmonic distortion is not a bad thing that it will give you an ugly sound) , 
but the Intermodulation products  from the intermodulation distorti!
 on    , These are very bad in the ear ! unless you like that sound , but most 
people don't like it ; 
so to avoid these bad distortions , music systems are split up in active 
frequency splitted amps and speakersystems ... that is the whole secret . 
If you are going to distroy this principle you will always have a bad or worse 
reproduction then the original and in this case practically no gain , or 
marginally in sound production .. 
the distortion  is mostly in the end or power  amplification  , it is rarely in 
a preamp since preamps have to deal with low power low voltage signals , but in 
the high voltage , high current portion of the final amps , there is what you 
get from distortion due to non linear behaviour of the circuits ; 

If your friend wants to make it sound louder then let him buy a second 925  
instead of spoiling his system that he owns now . or buy a tuneable active 
preamp splitsystem that is used in caraudio and put more powerful amps in the 
925 , but DON'T try to filter after the amp.. this is the wrong way of doing ; 

I give you here some calculations and a bit of insight about speakerfiltering on 
this link  http://64.233.183.104/search?q=cache:lx2-F3scZOIJ:www.bcae1.com/passxovr.htm+passive+crossover+filter+calculation&hl=nl&ct=clnk&cd=1&gl=be

So dear friend Kon , I am sorry for my bad English , but I tried to explain you 
and some other non technical people what it all is about . 
Hope it helps you and some other people .. 

all the best from Belgiums  Benjamin  ( and yes 16 Hz is a revelation to feel in 
the belly and to let it blow away your pants )   :-))

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