[time-nuts] COMPLETELY off topic - but I know you'll read it anyway.

[Didier Juges]

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Bruce Griffiths
> Sent: Saturday, October 11, 2008 7:24 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] COMPLETELY off topic - but I know 
> you'll read it anyway.
> 
> Jim Palfreyman wrote:
> > OK I have an interesting but simple problem that has nothing to do 
> > with time. But I'm sure someone on this list will know. And 
> > besides I can't be stuffed finding another list with such a 
> > good S/N ratio.
> >
> > In my spare time I play in a band.
> >
> > I have a 1000W amplifier that can be either two 500W stereo 
> > channels or a single 1000W mono running in "bridged" mode. 
> > (Basically one channel amplifies the upper part of the sine 
> > curve and the other the lower.)
> >
> >   

> Thats not an accurate description of how bridged amplifiers work.
> The load is connected between the 2 outputs which are 180 
> degrees out of phase.
> This doubles the available voltage swing across the load.
> For a given load, this quadruples the power (provided neither 
> of the amplifiers goes into current limit).
> 

> > The amp can drive speakers down to 4 ohms.
> >
> >   

> 4 ohms in bridged mode?
> Or 4 ohms in single ended mode?

> > I have two 8 ohm speakers.
> >
> > The source is mono.
> >
> > Do I run each 8 ohm speaker on its own 500W channel?
> >
> > or
> >
> > Do I run in bridged mode and put the two speakers in 
> > parallel onto the 1000W amplifier?
> >
> > Any takers?
> >
> > Regards,
> >
> > Jim
> >   
> 
> Bruce
> 

Jim,


Since your amplifier is specified at 1000W bridged and 2x500W non bridged,
that seems to indicate that the amp would be current limited (otherwise you
could get 200W in bridged mode), so in bridged mode, you are expected to use
speakers with 2ximpedance specified for non-bridged operation.

You say the amplifier can drive speakers down to 4 ohms, but is that the
impedance where it can deliver 500W non-bridged?

If so, you will need 8 ohm impedance to get 1000W bridged. You can't get
there with two 8 ohm speakers, unless you use a transformer.

Since the power is likely to be the same if you bridge the amplifier and put
the speakers in series, or drive each speaker with it's own channel, I would
recommend the second (each speaker on it's own output, non bridged
operation) as it will probably have lower distortion.

Didier