Keith G wrote:
Keith G wrote:
"Serge Auckland" wrote
As to
phasing, I really don't understand the point of a variable phase
control. 0 & 180 switched should be provided to phase up the sub with
the mains (which hopefully will be in phase with each other), but apart
from that, I can't see it's possible to match the phase of the main LF,
as it will be frequency dependant. As you suggest, with two subs, trying
to get the phase right would be a nightmare.
I've twiddled it back and forth and can't say it makes a lot of
difference anyway and it ends up back at 0 deg!
Other controls needed are a crossover frequency selector and a level
control. Ideally, if the main speakers are small (say don't go below
70Hz) then the extreme bass should be rolled-off to the mains
considerably improving their power handling and lowering distortion.
Not sure I understood that....??
If the main 'speakers are small, they won't reproduce deep bass. Feeding
them with deep bass from the power amp will only serve to stress the bass
unit suspension and heat up the voice coil without actually producing any
sound.
OK, but this happens a million times a day on a million setups with small
speakers, does it not.....???
It is therefore better to limit the bass drive to
small speakers so that they are only given what they can deal with. It is
actually much better if the bass reduction can be done *before* the power
amplifier so that the PA isn't being asked to generate unusable volts.
This way, the power amp driving the small 'speakers will be able to
generate more volts that the 'speakers *can* handle, and so effectively
produce a higher output.
Hmm, OK.....
For my son's Christmas present some years ago, I built him a subwoofer
'Built' - as in 'done up an old bicycle'?? Nowadays, your kids could/would
divorce you for that....!! ;-)
system consisting of an electronic filter removing bass below a preset
frequency, a mono combiner and filter providing a balanced output to a
single subwoofer. The filter frequencies were selectable as was levels to
the subwoofer. The main 'speakers (small Missions) were connected to the
L&R output of a Quad 303 and were driven from 70Hz upwards. 70Hz downwards
was monoed to a balanced output driving a 100wpc AIWA power amp in bridge
mode into the subwoofer which was a large bass-reflex box tuned to 20Hz.
It was most successful, and saw him through his University days and
afterwards, not always to the pleasure of his neighbours however....
:-)
OK, with this setup (Oktavas):
http://www.apah69.dsl.pipex.com/show/submicsetup01.JPG
http://www.apah69.dsl.pipex.com/show/submicsetup02.JPG
I grabbed these sub/no sub snippets (the filename gives you the clue):
http://www.apah69.dsl.pipex.com/show...20No%20Sub.mp3
http://www.apah69.dsl.pipex.com/show...With%20Sub.mp3
http://www.apah69.dsl.pipex.com/show...20No%20Sub.mp3
http://www.apah69.dsl.pipex.com/show...With%20Sub.mp3
And these longer samples (because it impossible to shorten it too much):
http://www.apah69.dsl.pipex.com/show...20No%20Sub.mp3
http://www.apah69.dsl.pipex.com/show...With%20Sub.mp3
(The dreaded heartbeat has crept in here again and if they come up
*absolutely identical* then I'll have buggered up the file-saving!! :-)
Now, unless I'm missing summat, I can't see how the (In)Fidelios are
benefitting from the sub - the omnipresent 'traffic noise' (with the sub up
loud enough to 'count' - which it is) and the 'wha wha wha' tail-off (way
behind the speakers) is far more of a PITA than any extra whoomph on the
deep stuff....??
The problem is the sub's gotta go back tomorrow and I've got only a small
'WOO' to experiment with it!
"Serge Auckland" wrote
As to
phasing, I really don't understand the point of a variable phase
control. 0 & 180 switched should be provided to phase up the sub with
the mains (which hopefully will be in phase with each other), but apart
from that, I can't see it's possible to match the phase of the main LF,
as it will be frequency dependant. As you suggest, with two subs, trying
to get the phase right would be a nightmare.
I've twiddled it back and forth and can't say it makes a lot of
difference anyway and it ends up back at 0 deg!
Other controls needed are a crossover frequency selector and a level
control. Ideally, if the main speakers are small (say don't go below
70Hz) then the extreme bass should be rolled-off to the mains
considerably improving their power handling and lowering distortion.
Not sure I understood that....??
If the main 'speakers are small, they won't reproduce deep bass. Feeding
them with deep bass from the power amp will only serve to stress the bass
unit suspension and heat up the voice coil without actually producing any
sound.
OK, but this happens a million times a day on a million setups with small
speakers, does it not.....???
It is therefore better to limit the bass drive to
small speakers so that they are only given what they can deal with. It is
actually much better if the bass reduction can be done *before* the power
amplifier so that the PA isn't being asked to generate unusable volts.
This way, the power amp driving the small 'speakers will be able to
generate more volts that the 'speakers *can* handle, and so effectively
produce a higher output.
Hmm, OK.....
For my son's Christmas present some years ago, I built him a subwoofer
'Built' - as in 'done up an old bicycle'?? Nowadays, your kids could/would
divorce you for that....!! ;-)
system consisting of an electronic filter removing bass below a preset
frequency, a mono combiner and filter providing a balanced output to a
single subwoofer. The filter frequencies were selectable as was levels to
the subwoofer. The main 'speakers (small Missions) were connected to the
L&R output of a Quad 303 and were driven from 70Hz upwards. 70Hz downwards
was monoed to a balanced output driving a 100wpc AIWA power amp in bridge
mode into the subwoofer which was a large bass-reflex box tuned to 20Hz.
It was most successful, and saw him through his University days and
afterwards, not always to the pleasure of his neighbours however....
:-)
OK, with this setup (Oktavas):
http://www.apah69.dsl.pipex.com/show/submicsetup01.JPG
http://www.apah69.dsl.pipex.com/show/submicsetup02.JPG
I grabbed these sub/no sub snippets (the filename gives you the clue):
http://www.apah69.dsl.pipex.com/show...20No%20Sub.mp3
http://www.apah69.dsl.pipex.com/show...With%20Sub.mp3
http://www.apah69.dsl.pipex.com/show...20No%20Sub.mp3
http://www.apah69.dsl.pipex.com/show...With%20Sub.mp3
And these longer samples (because it impossible to shorten it too much):
http://www.apah69.dsl.pipex.com/show...20No%20Sub.mp3
http://www.apah69.dsl.pipex.com/show...With%20Sub.mp3
(The dreaded heartbeat has crept in here again and if they come up
*absolutely identical* then I'll have buggered up the file-saving!! :-)
Now, unless I'm missing summat, I can't see how the (In)Fidelios are
benefitting from the sub - the omnipresent 'traffic noise' (with the sub up
loud enough to 'count' - which it is) and the 'wha wha wha' tail-off (way
behind the speakers) is far more of a PITA than any extra whoomph on the
deep stuff....??
The problem is the sub's gotta go back tomorrow and I've got only a small
'WOO' to experiment with it!
I haven't listened to your samples as I'm currently using the internal
'speakers on my laptop, and they're not the best thing to use for
evaluating subwoofers.
In my view, the best way to set up a sub is to set the crossover
frequency at whatever you reckon is the -3dB point of your existing
'speakers, in your case, I'd start with 50Hz.
Start with the level control turned right down, and listening to normal
music (say an orchestra) turn the sub level up until you can hear it
filling in the bottom. Then try some bass heavy music and make up/down
adjustments until it sounds right. If you can't get it sounding right,
then try changing the crossover frequency, say 40Hz.
When I first set mine up, the biggest surprise was on some chamber music
which didn't have any deep bass *in the music*, but there was plenty in
the recorded ambiance, and it went from sounding like a studio recording
to sounding live. It was, by the way, recorded in a hall rather than a
studio, but with the subs, you could hear distant traffic noise.
S.