Tri-amping, driver time alignment, and carbon fibre cones
 

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

Tri-amping, driver time alignment, and carbon fibre cones
 

"Wally" wrote in message
m...
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.

I thought it's advisable to use exactly the same poweramps (for gain) for
all the amps?

Tri-amping, driver time alignment, and carbon fibre cones
 

On Wed, 11 May 2005 00:35:27 +0100, "Nath" wrote:

"Wally" wrote in message
om...
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.

I thought it's advisable to use exactly the same poweramps (for gain) for
all the amps?

Yes indeed, but If you're not using an active crossover, it's an
utterly pointless exercise in any case!

Wally by name.......................
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Tri-amping, driver time alignment, and carbon fibre cones
 

Stewart Pinkerton wrote:

I thought it's advisable to use exactly the same poweramps (for
gain) for all the amps?

Yes indeed, but If you're not using an active crossover, it's an
utterly pointless exercise in any case!

I am using an active crossover.
None of the amps is set to maximum volume.
The active crossover allows +/- 6dB gain adjustment on each band.
I can easily dial in far more treble than is neccessary.
The sound level meter shows that mid and treble are fine.


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

Tri-amping, driver time alignment, and carbon fibre cones
 

Nath wrote:

I thought it's advisable to use exactly the same poweramps (for gain)
for all the amps?

Why? What will happen if I don't?


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

Tri-amping, driver time alignment, and carbon fibre cones
 

In article , Wally
wrote:


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.

How do measurements of the frequency response now compare with before you
made the changes?

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Tri-amping, driver time alignment, and carbon fibre cones
 

On Wed, 11 May 2005 07:20:16 GMT, "Wally" wrote:

Stewart Pinkerton wrote:

I thought it's advisable to use exactly the same poweramps (for
gain) for all the amps?

Yes indeed, but If you're not using an active crossover, it's an
utterly pointless exercise in any case!

I am using an active crossover.
None of the amps is set to maximum volume.
The active crossover allows +/- 6dB gain adjustment on each band.
I can easily dial in far more treble than is neccessary.
The sound level meter shows that mid and treble are fine.

OK, in that case you have a genuine option going for you. Most of the
best box speakers I've heard have been active designs. Proper ones,
that is, not the Linn/Naim skamkrap.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

Tri-amping, driver time alignment, and carbon fibre cones
 

On Wed, 11 May 2005 08:58:59 +0100, Bob Latham
wrote:

In article ,
Wally wrote:
Stewart Pinkerton wrote:

I thought it's advisable to use exactly the same poweramps (for
gain) for all the amps?

Yes indeed, but If you're not using an active crossover, it's an
utterly pointless exercise in any case!

I am using an active crossover.
None of the amps is set to maximum volume.
The active crossover allows +/- 6dB gain adjustment on each band.
I can easily dial in far more treble than is neccessary.
The sound level meter shows that mid and treble are fine.

Since 1978 I've owned a pair of KEF model 105s. I've still got them and
still love them. But some time in the 80s KEF kindly provided me with a
circuit diagram for an active crossover specifically for model 105/2. I
was assured that it should be fine with 105/1.

Anyway I built it and spent weeks playing with the adjustments. At the
time I worked for BT and borrowed a signal generator and measuring
equipment to set the levels as per a graph provided by KEF.

Although the slopes and levels matched what the graph showed I never got
this to sound right. As you say, it did have much better bass and headroom
without doubt, but the balance was not there.

I concluded that there were several possible reasons why I couldn't get it
right and among them ......

1) Not using identical amps for all 6 drive units.

2) The 105/2 bass/mid xover is at 150 Htz my 105/1 is at 400Htz. Part of
the 24db/oct slope comes from cabinet dimensions and natural driver
roll off. The mid range cabinet on 105/2 is larger than 105/1 to extend
the B110 down to 150Htz. I think I would need to change the active
crossover to 400Htz to match the original design but to be honest I
don't have enough knowledge to do this. Any offers of help?

If you can mail or post the schematic, I can probably advise new
values.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

Tri-amping, driver time alignment, and carbon fibre cones
 

On Wed, 11 May 2005 07:20:17 GMT, "Wally" wrote:

Nath wrote:

I thought it's advisable to use exactly the same poweramps (for gain)
for all the amps?

Why? What will happen if I don't?

You'll get different levels on bass, mid and treble, which you'll have
to adjust via the active crossover.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Tri-amping, driver time alignment, and carbon fibre cones
 

Stewart Pinkerton wrote:

Why? What will happen if I don't?

You'll get different levels on bass, mid and treble, which you'll have
to adjust via the active crossover.

Each amplifier also has its own volume control (the Cyruses are integrated
amps, the valve has an independent vol on each channel).

If the issue is primarily one of disparate gain, then I don't think that's
an issue. The sensitivities of the amps for full power are all around
200-300mV, and the DAC, as you may be aware, puts out 2V (pk-pk). As it is,
turning the preamp much over half-way causes the limiter LEDs in the
crossover to flicker (the limiter is adjustable, and is set to +6dB).


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