On Wed, 10 Nov 2004 07:56:40 GMT, "harrogate2"
wrote:


"Eiron" wrote in message
...
Wally wrote:



If you have an active crossover then the tweeter amp can be rather
lower powered. In theory you could get full power out of a CD at
any
frequency but in practice the levels drop at higher frequencies.
An experiment on your favourite music with an audio editor such as
Goldwave will be helpful. Split it into three at your chosen
crossover frequencies and search for the maximum level in each
file.
This will show the relative voltage and hence power required for
each
amp, assuming all drivers have the same sensitivity.


Interesting. Is Goldwave a freebie?

http://www.goldwave.com
You can download an evaluation version.

I tried splitting a track (Money, from the CD layer of the DSotM
SACD)
at 300Hz and 3000Hz.
The peak voltages we
Low 0.96
Med 1.00
High 0.82 (surprisingly high)

So you could use a couple of Cyrus Twos and a Cyrus one for the
treble
but it would be better to use three identical amps.


Won't my T27s freak out if there's a 50W amp dedicated to them?

You could use a capacitor in series with the T27, as long as you
factor it into the active crossover response.

--
Eiron.

More to it than that - the passive crossover normally found in a
speaker is actually quite lossy.

From an article in Wireless World many years ago when bi and tr amping
were just starting, it suggested that against a 'normal' 30Wpc amp,
tri-amping needed about 20W for the bass or bass-mid, 10W for the mid
and 4-5W for the tweeter. Base that on the inefficiency of most modern
speaker systems and the equivalent of a 100Wpc amp would need 60, 30,
and 15, and that would still be far too much in most cases.

I remember one chap who did bi-amping with a 15W Class A for the bass
and 5W class A for the tweeter, and any DBT he did always gave
preference for the calss A kit.

So who needs power?

Just had a look at some modern pop music (Avril Lavigne - so pretty
much mainstream) with Audition - and it was interesting. I high pass
filtered and low pass filtered the files to mimic the action of a
crossover and looked at peak levels in Statistics to see how much
smaller the tweeter amp could be. The answer was that peak levels were
no lower above 2200Hz than they are below.

So for modern pop, you need a tweeter amp as powerful as the woofer
amp.

d
Pearce Consulting
http://www.pearce.uk.com