[sdiy] Speaker Impedance

[rkmoore at memphis.edu]

I agree that putting resistors in series with the speakers is a bit of a
kludge at best, but I was referring to very small circuits like the
cracklebox.  The crackle box doesn't even have collector or emitter
resistors that could be altered.  The only other option I could see
would be placing a couple of resistors in the circuit to divide the
voltage before it goes into the bases of the first transistors.

I think that in a very small, low power circuit like the cracklebox that
not enough heat would be generated to pose a problem.  I might be wrong
here, though.  I definitely would not use power resistors to control
output volume to a PA system or instrument amplifier (even though big
rheostats are sometimes used by manufacturers to attenuate horns, etc).

Again, I think the output resistors might be an option for SMALL
circuits only!  Don't replace the 16ohm speakers on your suitcase rhodes
and put quarter watt resistors in series with new 4ohm speakers.  This
would be BAD . . . 

Richard Moore
----- Original Message -----
From: Seb Francis <seb at burnit.co.uk>
Date: Monday, May 23, 2005 5:49 pm
Subject: Re: [sdiy] Speaker Impedance

> This talk of putting resistors in series or parrallel with 
> speakers is 
> *not* good advice .. you will end up just turning power to heat in 
> the 
> resistor.  e.g. using a 4 ohm resistor in series with a 4 ohm 
> speaker 
> will convert 50% power to sound and 50% to heat.
> 
> Far better would be to adapt the circuit to cope with the actual 
> impedance speaker you have.  In actual fact it is very likely that 
> you 
> can use a 4 ohm speaker with a circuit intended for 8 ohms if you 
> just 
> make sure you don't turn the volume too high!  And equally it is 
> very 
> likely you can use an 8 ohm speaker with a circuit intended for 4 
> ohms, 
> but you will just find that the max volume isn't as loud as it 
> would be.
> 
> Seb
> 
> 
> 
> Metrophage wrote:
> 
> >Hi Tim,
> >Does this mean that the same applies to a speaker plus a 
> resistor? Does
> >, for example, a 4 ohm resistor in series with a 4 ohm speaker 
> equal an
> >8 ohm impedance for the output? I was wondering whether or not 
> this was
> >the case. 
> >CJ
> >
> >--- Tim Parkhurst <tparkhurst at siliconbandwidth.com> wrote:
> >  
> >
> >>Hey Rafael,
> >>
> >>If memory serves (sometimes it does, sometimes it don't...), I
> >>believe the
> >>same tricks used with resistors will work with speakers. Ohm's Law
> >>still
> >>applies. In other words, two 16 Ohm speakers wired in parallel will
> >>give you
> >>8 Ohms. Conversely, two 16 Ohm speakers wired in series will 
> give you
> >>32
> >>Ohms, and so on. 
> >>
> >>
> >>Tim (a Starbucks mocha in each hand gets me wired in parallel) Servo
> >>
> >>"Imagination is more important than knowledge." - Albert Einstein
> >>
> >>
> >>
> >>
> >>    
> >>
> >>>-----Original Message-----
> >>>From: Rafael_Cohen at prusec.com [mailto:Rafael_Cohen at prusec.com]
> >>>Sent: Monday, May 23, 2005 9:56 AM
> >>>To: synth-diy at dropmix.xs4all.nl
> >>>Subject: [sdiy] Speaker Impedance
> >>>
> >>>
> >>>Hey everybody,
> >>>Guess what... it's another newbie question!!
> >>>
> >>>I have some schematics requiring 8 ohm speakers, and in some of my
> >>>DIY/scavenging I come across speakers of various other impedance,
> >>>      
> >>>
> >>usually
> >>    
> >>
> >>>higher than 8ohm.  Everything from 16ohms to 45 ohms... sometimes
> >>>      
> >>>
> >>computer
> >>    
> >>
> >>>speakers or speakerphones, etc...
> >>>
> >>>My question is, what do I need to do in order to adapt the circuit
> >>>      
> >>>
> >>to
> >>    
> >>
> >>>speakers of different imedance?  Also, is there a simple way to
> >>>      
> >>>
> >>test the
> >>    
> >>
> >>>imedance of a speaker?
> >>>
> >>>Thanks again,
> >>>Rafael
> >>>
> >>>--
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> >>>      
> >>>
> >>5/22/2005
> >>    
> >>
> >>-- 
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> >>Checked by AVG Anti-Virus.
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> >> 
> >>
> >>
> >>
> >>
> >>    
> >>
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