[sdiy] Speaker Impedance

[Bob Weigel]

Sure.  But say you started with a 4 ohm speaker that had a 3 ohm DC 
voice coil (potentially 25% efficient or less).  NOW....with the 
resistor you have the equivelent of an 8 ohm speaker with 7 ohms of DC 
resistance that is only making heat..no sound. So now it's half as 
potentially efficient roughly. 
     In other words were you to have put a speaker instead of a dead 
impedence there (sonically speaking) then you would have an 8 ohm 
speaker equivelent neglecting phase cancellations and so on from having 
two sources now... that is the same efficiency as one speaker.   ie. if 
you give the entire unit 100watts of power, you will realize the same 
decibel level (ideally again) that you would get with a single speaker 
with 100watts of power across it.  Follow?  BUT....you now can double 
the power without blowing out the speaker.  -Bob

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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>>5/22/2005
>> 
>>
>>
>>
>>
>>    
>>
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