[sdiy] Speaker Impedance

[Seb Francis]

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
>>>
>>>--
>>>No virus found in this incoming message.
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>>>      
>>>
>>5/22/2005
>>    
>>
>>-- 
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>>Checked by AVG Anti-Virus.
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>>5/22/2005
>> 
>>
>>
>>
>>
>>    
>>
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