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Old 23rd January 2003, 05:05 PM   #11
DRC is offline DRC  United Kingdom
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halojoy,

Quote:
An amplifier capabable of producing Sinuswaves with very low distortion
and Driving Lodspeakers who produces soundwaves from such signal
with low distortion Should be what I am aiming for.
If a system can reproduce sine waves without amplitude or phase distortion then it **will** faithfully reproduce square waves too !!

Dave
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Old 23rd January 2003, 07:37 PM   #12
halojoy is offline halojoy  Sweden
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Quote:
Originally posted by DRC
halojoy,
If a system can reproduce sine waves without amplitude or phase distortion then it **will** faithfully reproduce square waves too !!

Dave
I said very low distortion.
I said not zero distortion.

There is an upper limit, will always be.
In what the machines can produce.

But there is another limit - that is what human sensors
can catch.

We are already onto machines, that delivers beyond
human limits.
There are even machines that perform better then the usually used
test-equipment.
CD- players with noise less than the "noise-floor".

--------------------------------------------------------
There will always be people longing for to goto the moon.
And then Mars and then .....
Even though there is not much use in doing so.
Other than saitisfy some curios minds
Most people would be just as satisfied with
trying to create as good living as possible on THIS PLACE.
And be busy enough by keeping their daily life running.

/halo - belongs more to this later category
- but sometimes also wonders - what is round that corner over there?
- maybe there is something "more green" than on my side
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Old 24th January 2003, 01:12 AM   #13
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Quote:
Originally posted by phase_accurate
Hi Circlotron

If you look at the real life dynamic driver at a specific frequency - then force is proportional to current and current is proportional to voltage and therefore force is proportional to voltage as well. Regards

Charles
Mmmm.... That makes sense. The voice coil resistance would make the voltage source of the amplifier appear somewhat of a current source too. What I am thinking about is the effects an amplifier with a bit of *negative* output resistance will have on the driver, particularly it's frequency response in a sealed enclosure when it is below resonance. I am hoping it would reduce the LF rollof. I'll have a bit of an experiment this weekend and see.
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Old 24th January 2003, 07:13 AM   #14
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Hi Circlotron

There were several articles in EW+WW dealing with this. What you actually do is increasing damping, i.e. lowering Qes artificially.
There are even circuits around that use a complex output impedance in order to influence ALL mechanical parameters. There is one company in Sweden (Audio Pro) that were building subwoofers using this principle (ACE, Amplifier Controlled Euphonic).
I have the JAES article if you are interested.

Regards

Charles
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Old 24th January 2003, 09:01 AM   #15
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Last night I saw a site selling those AceBass things. I remember the word "euphonic" because I don't know what it means. Read the patent about it too, but is was a bit cryptic.

JAES article?? Yes please!!!!!
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Old 24th January 2003, 10:27 AM   #16
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Hi Circlotron

Unfortunately I don't have a scanner myself. But I could send you the photocopies by snail-mail.
I even have a veroboard prototype of an ACE circuit I built more than 10 years ago. It is ugly though but would be O.K. for playing around with. It is consisting of an input summing circuit, a subsonic filter, a lowpass filter, a limiter (using a CA3080 OTA) and the ACE bandpass filter and current-feedback circuit. It is using TL074 opamps or the like. I haven't thrown this board away so far for nostalgic reasons. If you want it you may have it for free.
I used it with a Philips power amplifier that is DC coupled throughout.
You would have to change resistors and capacitors to make it fit your driver(s).
I used it with two woofers made by ILP UK (the ones with the large IC amplifiers). Those drivers were long excursion 12" PA drivers (10 mm one-way, and this back in 1988 !!!) which are not made anymore.
The bass emerging from the box was very deep and clean and it made the whole house shake even at moderate volumes. When you tapped the cones slightly with your fingers you could hear the difference in fs between ACE in use or not !!!!
There was a problem with dynamic headroom however, that's why I gave up on this circuit. The woofers are now serving in 6th order bandpass enclosures, used for small PA purposes (i.e. for private drinking bouts etc).

IMO the modern specialist long-excursion woofers offer more versatility for building compact and well sounding subwoofers.

Regards

Charles
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Old 24th January 2003, 03:56 PM   #17
DRC is offline DRC  United Kingdom
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phase_accurate,
Thanks for the explaination of "radiation resistance" - I guessed as much but it's useful to know for sure . If I had a specific name for this I think it would have been acoustic load. Maybe I prefer radiation resistance.

Quote:
The movement of a speaker cone is mainly compliance controlled below fs (which explains the finite cone travel for the battery example) and above fs it is mass-controlled.
OK - I didn't realise this. Does this always have to be the case (because fs in related to mass, spring k and damping) ?


Quote:
Theoretically an IDEAL single fullrange-driver should therefore be capable of reproducing a square-wave as it was passed through a very wide bandpass filter !!!
Surely a S-W through a wide bandpass filter is just a S-W ? In this case is this not what I originally stated (or tried to) ?

Quote:
Therefore both types of drivers should behave the same way.



Dave - not trying to be difficult
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Old 25th January 2003, 03:08 AM   #18
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Quote:
Originally posted by phase_accurate
Hi Circlotron
I could send you the photocopies by snail-mail.
Regards Charles
Sure! email me and I'll tell you my *secret* location.
No need for the board though, besides it would cost way more to post.
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Old 25th January 2003, 06:44 AM   #19
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Hi Circlotron

You can simply e-mail me with the e-mail button down below.

Regards

Charles
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