Cyrus II subwoofer impedance matching
 

I'm building up a sound system for our living room using second hand
parts. I would like to keep things as small and unobtrusive as
possible. So far I have a Cyrus II amp - this has outputs for one pair
of speakers (rated at 8 Ohms). My plan is to connect two small
bookshelf speakers like the Tannoy Revolution R1s and add a subwoofer.
The options as far as I can see a

1) connect a passive subwoofer in parallel with the bookshelf speakers
2) connect a passive subwoofer in series with the bookshelf speakers
3) connect a subwoofer with a built in amp

I think 1 risks blowing the amp, 2 could affect the sound quality so
I'm leaning towards 3 but this seems a bit of a waste of the power
available from the Cyrus II. Any opinions?

Cyrus II subwoofer impedance matching
 

On Sun, 4 Jan 2009 08:42:59 -0800 (PST), molipix
wrote:

I'm building up a sound system for our living room using second hand
parts. I would like to keep things as small and unobtrusive as
possible. So far I have a Cyrus II amp - this has outputs for one pair
of speakers (rated at 8 Ohms). My plan is to connect two small
bookshelf speakers like the Tannoy Revolution R1s and add a subwoofer.
The options as far as I can see a

1) connect a passive subwoofer in parallel with the bookshelf speakers
2) connect a passive subwoofer in series with the bookshelf speakers
3) connect a subwoofer with a built in amp

I think 1 risks blowing the amp, 2 could affect the sound quality so
I'm leaning towards 3 but this seems a bit of a waste of the power
available from the Cyrus II. Any opinions?

The built-in amp option is easiest to implement, but if you have a
driver, there is no reason why you shouldn't power it from the Cyrus
II, which is flat down to about 1Hz. Search the Internet and find a
circuit for a crossover unit and scale the values of L and C so it
operates at about 100Hz (or whatever your sub needs). Use this to
split the power between the sub and the normal speakers - you will
have to choose a channel to operate from, you can't use both.

Provided you have chosen a sub driver with an output level similar to
the Tannoys, you will have a decent starting point for the long slow
job of bringing the sub into line with the mains.

This will be option 4)

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

Cyrus II subwoofer impedance matching
 

In article
,
molipix wrote:
I'm building up a sound system for our living room using second hand
parts. I would like to keep things as small and unobtrusive as possible.
So far I have a Cyrus II amp - this has outputs for one pair of speakers
(rated at 8 Ohms). My plan is to connect two small bookshelf speakers
like the Tannoy Revolution R1s and add a subwoofer. The options as far
as I can see a

1) connect a passive subwoofer in parallel with the bookshelf speakers
2) connect a passive subwoofer in series with the bookshelf speakers 3)
connect a subwoofer with a built in amp

I think 1 risks blowing the amp, 2 could affect the sound quality so I'm
leaning towards 3 but this seems a bit of a waste of the power available
from the Cyrus II. Any opinions?

Various things strike me about (1) and (2).

Firstly, that you might not be able to get enough power. Mainly because a
sub will tend to be inefficient unless you are going to use a large
cabinet.

Secondly, that getting the levels to match from sub and main speakers may
well be difficult (without losing even more power). In particular I'd
expect a sub to need somewhat more power than bookshelf speakers - but you
don't say what sub you plan, so hard to say more.

Thirdly, that (2) would probably upset the responses of the bookshelf
speakers. i.e. as you say that may well cause problems with the results.
Again you say nothing about any passive crossover filters you would be
using, so hard to say more.

Finally, that any passive sub may well need you to experiment with
filtering to try and correct the sub response, again risking wasting power
if done between amp output and speakers.

To make life easy I'd recommend (3) or if you wish to experiment with
'DIY'...

(4) use another amp to drive your sub. Take the outputs from the 'record
out' of the Cyrus and use a low-pass filter between that and the extra
amplifier. You may find a cheaper high power amp from an electronics
supplier may do for this. Something along the lines of a module or kit.

or

(5) If you don't need high power, add a filter into the tape loop that can
extend the response of the speakers at LF. This is obviously to be done
with caution, though, as it would rapidly run you into trouble if you want
loud sounds down in the sub region.

However I guess the choice will depend on how much time and skill you can
devote to trying something. Again, that isn't clear from what you write, so
I can't comment.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Cyrus II subwoofer impedance matching
 

"molipix" wrote in message


I'm building up a sound system for our living room using
second hand parts. I would like to keep things as small
and unobtrusive as possible. So far I have a Cyrus II amp
- this has outputs for one pair of speakers (rated at 8
Ohms). My plan is to connect two small bookshelf speakers
like the Tannoy Revolution R1s and add a subwoofer. The
options as far as I can see a

1) connect a passive subwoofer in parallel with the
bookshelf speakers

Passive subwoofers operated from the same power amps as the mains have
pretty well fallen out of favor. The reasons are many. One is that they take
power away from the mains. Another is that subwoofers tend to be less
efficient than mains, so matching the sub to the mains means that there must
either be a level mismatch or an attenuator in series with the mains. Then
you're back at the first problem! :-(

2) connect a passive subwoofer in
series with the bookshelf speakers

Same problems as (1) if you get the crossover right. The two are essentially
the same, like comparing series and parallel crossovers.

3) connect a subwoofer with a built in amp

(4) A passive subwoofer with an external amp and active crossover.

I think 1 risks blowing the amp, 2 could affect the sound
quality so I'm leaning towards 3 but this seems a bit of
a waste of the power available from the Cyrus II. Any
opinions?

I wouldn't call a Cyrus 2 a high powered amp by modern standards. 50 wpc?
You can get a clean 100 wpc out of a ca. $100 receiver.