Testing a loudspeaker with noise cancellation (anti-phase) ?

[N Cook]

Has anyone tried it, for high power testing without blowing a speaker ?
Perhaps tying one speaker enclosure over the one under test with a
microphone midway to monitor standing wave.
Same generator feeding both but adjusting power and phase by some means to
the added one to cancel a lot of the overall noise in a confined space.

 

[Ron(UK)]

Has anyone tried it, for high power testing without blowing a speaker ?
Perhaps tying one speaker enclosure over the one under test with a
microphone midway to monitor standing wave.
Same generator feeding both but adjusting power and phase by some means to
the added one to cancel a lot of the overall noise in a confined space.

I don't really understand what you are trying to do here, are you trying
to generate an antiphase signal to cancel out the sound from the speaker
under test?

Ron(UK)

 

[N Cook]

I don't really understand what you are trying to do here, are you trying
to generate an antiphase signal to cancel out the sound from the speaker
under test?

Ron(UK)

Giving the speaker, under test, with a thorough work-out in the workshop
without driving youself nuts and any neighbours.
Or even testing out an amp with a speaker rather than a dummy load if there
is likely to be reactance/oscillation problems at high level say.

 

[Arfa Daily]

Giving the speaker, under test, with a thorough work-out in the workshop
without driving youself nuts and any neighbours.
Or even testing out an amp with a speaker rather than a dummy load if
there
is likely to be reactance/oscillation problems at high level say.

You do have some interesting problems and potential solutions !! I've never
had a problem running an amp into a dummy for high power testing. I built
myself one a long time back. I incorporated a power meter, a small speaker
with a volume control to monitor with, a pass-through jack so that you can
go on out to a speaker, but keep the power meter section connected, a BNC
output for a 'scope, and a fall back impedance switching system, with bright
LED indicators. If I do want to test into a speaker, I have a piece of thick
high density foam on which I place the cabinet face down, on a concrete
floor. You can then run that fairly hard, without kicking up too much noise.

Arfa

 

[N Cook]

You do have some interesting problems and potential solutions !! I've never
had a problem running an amp into a dummy for high power testing. I built
myself one a long time back. I incorporated a power meter, a small speaker
with a volume control to monitor with, a pass-through jack so that you can
go on out to a speaker, but keep the power meter section connected, a BNC
output for a 'scope, and a fall back impedance switching system, with bright
LED indicators. If I do want to test into a speaker, I have a piece of thick
high density foam on which I place the cabinet face down, on a concrete
floor. You can then run that fairly hard, without kicking up too much noise.

Arfa

Foam directly between floor and face of speaker with no extra air volume for
the moved air to compress into at very high power levels and for extended
time. ?
I would have thought that was a definite no-no or are you just doing so, for
no more than 10 seconds say. ?
I tie an old folded up duvet to the front of the cabinet for low to medium
power but I've never dared to turn up the wick to full like that with just a
cone's worth of volume to compress into.

 

[Ron(UK)]

Foam directly between floor and face of speaker with no extra air volume for
the moved air to compress into at very high power levels and for extended
time. ?
I would have thought that was a definite no-no or are you just doing so, for
no more than 10 seconds say. ?
I tie an old folded up duvet to the front of the cabinet for low to medium
power but I've never dared to turn up the wick to full like that with just a
cone's worth of volume to compress into.

I don't really understand why you want to run a speaker at high power
levels for an extended period if you don't want to hear what the speaker
is doing. If you are testing for rattles, sweeping a tone is the easy
way and it doesn`t have to be particularly loud

Ron(UK)

 

[Arfa Daily]

You do have some interesting problems and potential solutions !! I've
never had a problem running an amp into a dummy for high power testing. I
built myself one a long time back. I incorporated a power meter, a small
speaker with a volume control to monitor with, a pass-through jack so that
you can go on out to a speaker, but keep the power meter section
connected, a BNC output for a 'scope, and a fall back impedance switching
system, with bright LED indicators. If I do want to test into a speaker, I
have a piece of thick high density foam on which I place the cabinet face
down, on a concrete floor. You can then run that fairly hard, without
kicking up too much noise.

Arfa

Well, I'm not doing it for hours on end, but not for just a few seconds
either. Most of my high power tests are done into a dummy load as I said,
but occasionally, when I do want to test the 'real' dynamic performance into
a complex load, as you say, just to make sure that the output stage is
stable under those conditions, I just lay the cab face down on the foam, as
described, and have never had a problem. I would guess that the air still
shifts ok through the foam, just that it is broken up by the foam acting as
microbaffles like a car exhaust silencer. It doesn't produce a totally quiet
situation, but does attenuate the sound quite a bit.

Arfa