From: poulson@cs.widener.edu (Joshua R. Poulson)
Newsgroups: rec.audio.car
Subject: Re: Autotek Amplifiers? (1 ohm stability stuff)
Date: 13 Apr 1992 15:59:04 -0400
Organization: Widener Univ. Dept. of Computing Services
Distribution: na
NNTP-Posting-Host: lisa.cs.widener.edu

In article <1992Apr13.135209.16437@hemlock.cray.com> jch@teak.Cray.COM (J.C. Hamlin) writes:
>If you examine audio amplifiers on the market, you'll find that most 1 ohm 
>and 1/2 ohm stable amplifiers are lower power (rated 50 watts or less 
>into 4 ohms).  And, the "monster" (high voltage) amps are only 2 ohm stable.

That' true, but the BIG amps have higher damping factors into the same
impedance compared to "cheater" amps.

>The trick (in 4 ohm rated power classed competition) to using 1 ohm and 1/2 
>ohm stable amps is not the 4 ohm rated power.  You don't connect a single 
>speaker to each terminal with these guys, you add extra speakers to it--and 
>each one will get the same amount of power as the single driver connected to 
>it (theoretically).  It is like getting a free amp.  Or, you bridge the 
>amplifier whichs doubles the power, and then use a 4 ohm speaker dropping the 
>impedance per channel to 2 ohms--thus quadroupling the power per driver.  

Each drop in impedance is accompanied by a drop in damping factor.  The
lower the damping factor, the less likely the amp can slow down your
magnets properly, and we've introduced more distortion... :)

>Depending on the amp, you should be able to connect multiple drivers bridged.

Like all the prize-winners in the lower power classes have done...

>Here's one example (the one I am using thanks to a suggestion from Joshua 
>Poulson).  I am running four 4 ohm C-10s bridged across the terminals of 
>an Orion 225HCCA (2x25, 1/2 ohm stable).  This produces 100 watts per driver 
>and a 2 ohm load on each channel per driver.  With four drivers, you get a 
>load of 1/2 ohm on each channel and 400 watts of power total.  From a 
>50 watt amplifier. :-)

I believe we figured out that the damping factor for the Orion was 400
to start with... but it falls dramatically:

2x25  into 4 ohms --> 400
1x100 into 4 ohms --> 200
1x200 into 2 ohms --> 100
1x400 into 1 ohm  -->  50

When will we get a chance to test this on the driver setup?  I'm curious
to see if this amp can handle the array without flopping all over the
place.

>I am considering using a Phoenix Gold MPS-2500 
>(2x50, 1/2 ohm stable) to get 200 watts per driver, but I am unsure as of 
>yet.

I haven't been able to dig up a damping factor on that piece yet.

>When searching for an amp to produce a lot of power into many speakers (one 
>that is low impedance stable), don't expect a lot of power per driver unless 
>you bridge it or use 2 ohm drivers.  Of course there are notable exceptions 
>like the Orion 2100 HCCA (2x100, 1 ohm stable).

Of course, that amp has the price tag to go with its awesome power
handling capability.

You get what you pay for... :)
-- 
Joshua R. Poulson (NIC handle: JRP8)       [Joshua R. Poulson@cyber.Widener.EDU]
Systems Programmer, Widener University     [poulson@cs.Widener.EDU]
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Newsgroups: rec.audio.car,rec.autos,misc.consumers