A few days ago, I bought a Cyrus Straightline amp to go with my Cyrus 2 and
my valve amp, and I am now doing the tri-amp thing. The valve amp is on the
tweeters, the Cyrus 2 on mid range, and the Straightline on bass. Some
tweaking of the Behringer DSP parametric thingy with the aid of a sound
level meter has yielded what, to my ears, is a pretty balanced sound.

The main perceived sonic differences are bucketloads of low bass, and much
more punch overall - no sign of amplifiers straining at highish volumes.
Sometimes, I feel that the mid is a bit shouty, but this is only evident on
some pieces of music - a lot of things have changed, and I'm stll getting
settled with the new sound, so it's entirely possible that there's plenty
scope for adjustment and tweaking. I just backed the midrange level down a
little, so I'll see how things go.

Most noticable improvements in instrument/music terms are that drums are
more solid - tighter and more punchy; acoustic guitars are much better -
much clearer; and classical music seems to have acquired a dynamic range I
was unaware of beforehand.

I haven't really cranked it up much - I did it once and got a couple of pops
from the bass drivers, which got me out of my seat and diving for the volume
control pretty damn quick. At the moment, it goes about as loud as I dared
go when it was just the Cyrus 2 and the 3-way passive crossovers, except
that it's now much, much cleaner - night and day, in fact.

Methinks there's definitely something in this amplifier headroom lark.


The next thing to look at is the speakers. Before I go off designing boxes,
I have some questions about driver time alignment. Some background info, and
then my questions...

The Behringer active crossover uses, I believe, Linkwitz-Reilly 24dB/octave
filters. Mid/top xover is at 3.5KHz, bass is currently 400Hz or so, and will
eventually be lowered to around 80Hz. The crossover also has a settable
delay on the bass output (up to 2ms, I think). Drivers are KEF B139, B110
and T27.

Do I need to give driver time alignment serious consideration? If so, how do
I determine the offsets?

Do I align the tweeter dome with the recessed dustcap of the midrange?

What about alignment with the flat-fronted B139? These are to be used as
subs - will positioning them away from the mid/top make a mess of things,
and can I make amends by using the delay feature of the crossover? If not,
and I have to make a 3-way speaker, how do I align the B110's normal cone
with the B139?


What's the deal with carbon fibre cones? My KEF B110s have those plasticised
or bextrene cones which received wisdom suggests are a bit dull at low
volumes (experience over many years would bear this out - I've never felt
that my big KEFs really rocked until the volume was up a bit). Wilmslow
Audio are selling Monacor bass/mid drivers which are direct replacements for
the B110 - see...

https://secure.wilmslow-audio.co.uk/...onacor_Drive_U
nits_17.html

The SPH-135/AD polymer cone Bass is the one they tout as a B110 replacement,
and they also do another version of the same driver - SPH-135/C - which has
a carbon fibre cone. What would be the likely differences I'd get with these
carbon fibre jobbies?


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk