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Old 12th October 2010, 12:10 AM   #561
Javin5 is offline Javin5  Switzerland
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Quote:
Originally Posted by Joachim Gerhard View Post
See my atattached measurement of a small 2 way speaker i design recently. It is a 10cm woofer and a 19mm tweeter with waveguide. The rising distortion under 60Hz comes from the fact that this speaker has restricted bass response. Note especially the low amount of 3rd order distortion. Second order distortion in the bass can be brought down by a factor of 3 by using two woofers in push-pull and i do that in my subwoofer designs.
Your plot of the "small speaker distortion at 1 KHz", reveals some (lower level) spectral lines which are not harmonics of the fundamental. Any idea what produces them?

Kurt
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Old 12th October 2010, 12:15 AM   #562
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This is rubb and buzz. I comes from imperfect glue joints, noise in the suspension, iron dust or hairs in the airgap etc. A little bit also comes from my generator. I used a simple M-Audio Transit soundcard.
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Old 12th October 2010, 12:26 AM   #563
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The highest of this side distortions is 74dB under the main signal. I am not sure if i can hear that. Funny enough rub and buzz is audible if you crank it. Until recently there was a women in every serious loudspeaker factory that checked every spaeker with a loud sine sweep. A terible job only for people with iron health. The latest Klippel System that costs a fortune claims to make that unnecesesarry but i am not 100% convinced. Fix a little bell to the membrane of the speaker you measure and you here the bell ringing loud all the time whereas the first and second harmonic on the analyser show the same result as without the bell. The ear seems to be superb to pick up noise that escapes conventional analysers.
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Old 12th October 2010, 10:48 AM   #564
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Originally Posted by Damon Hill View Post
Successfully ran my first SPICE sim using the diff amp example. The current source wouldn't take "2 mA"--kept changing it to "2". That attempt to run a 2 A current source generated an interesting error log; .002 worked.

I've found a SPICE model for the Leach amplifier on his site; if I can get the hang of this software, it should be a valuable learning tool worth far more than the price of your book. Thanks for getting me motivated!
Hi Damon,

That's wonderful if the SPICE tutorial in the book helped you get going with LTspice. It's a great tool that I know from experience can be very helpful in gaining insight and refining circuits.

When you enter a value like 2 mA (the way we would write it in a sentence), for LTspice you need to enter it as 2mA with no space. Also, the thing that counts is the "m", so if you wrote 2m for a current source that would signify 2 mA as well. Also, be careful of resistor values in the megohm range. 2M will not work. You need to write 2Meg. If LTspice sees an m or M, it thinks milli.

Cheers,
Bob
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Old 12th October 2010, 11:00 AM   #565
AndrewT is offline AndrewT  Scotland
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all units are normally tagged on to the value.
5lbs, 4inches, 25degC, 2pair, it's the way we technocrats do it.
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Old 12th October 2010, 12:48 PM   #566
AndrewT is offline AndrewT  Scotland
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p23, The Ideal Transistor. 2nd para:
infinite current gain, infinite input impedance, infinite output resistance.
Really? This confuses me.
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Old 12th October 2010, 05:29 PM   #567
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Originally Posted by AndrewT View Post
all units are normally tagged on to the value.
5lbs, 4inches, 25degC, 2pair, it's the way we technocrats do it.
No Andrew, Bob is actually correct and the way it should be written is with a space, e.g. "2 mA". I think it's also stated to be written that way in British Standards. Most engineers do it wrong!
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Old 12th October 2010, 05:59 PM   #568
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Originally Posted by Bob Cordell View Post
That's wonderful if the SPICE tutorial in the book helped you get going with LTspice. It's a great tool that I know from experience can be very helpful in gaining insight and refining circuits.

[snip]

Cheers,
Bob
Bob,

I know you are busy, but could you post one of the SPICE models for the complete amplifier from your book? I have been reading the book, and have been re-acquanting myself with SPICE modeling (it has been ~10 years), and I would like to start to dig in with a working model.

Thank you for your book!
Edward
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Old 12th October 2010, 06:12 PM   #569
AndrewT is offline AndrewT  Scotland
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Hi all,
I have finished Intro + Ch1 & Ch2.
A very good read.
I particularly like the way Bob talks us through these early topics.

I am amazed at how well he ties all the disparate nuggets together into a coherent whole. Decades of titbits are coming together, some for the first time.

I look forward to reading the rest and expect my Christmas present to be the "knowledge" and not the physical book, as I had first thought.

Thanks Bob.
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Old 12th October 2010, 06:50 PM   #570
JPV is offline JPV  Belgium
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Originally Posted by Joachim Gerhard View Post
The highest of this side distortions is 74dB under the main signal. I am not sure if i can hear that. Funny enough rub and buzz is audible if you crank it. Until recently there was a women in every serious loudspeaker factory that checked every spaeker with a loud sine sweep. A terible job only for people with iron health. The latest Klippel System that costs a fortune claims to make that unnecesesarry but i am not 100% convinced. Fix a little bell to the membrane of the speaker you measure and you here the bell ringing loud all the time whereas the first and second harmonic on the analyser show the same result as without the bell. The ear seems to be superb to pick up noise that escapes conventional analysers.
Sorry but could you reexplain this bell stuff. It should ring because of the main signal , no ?

JPV
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