Hi Joachim,
Thank you. I was actually very fortunate that McGraw-Hill let me put in as much as I did. When you try to cover a lot of topics there are sometimes some difficult decisions to be made about what to cut.
Cheers,
Bob
Yay, my copy turned up yesterday! What a great work, right on target! - (on first take, at least!). What a pity though; the sad reviewer Mr de Velder (post #577) can't get his head around these new ideas in solid-state. His review is even more clearly prejudiced than that he gave of D. Self's Small signal audio publication.
Hurtful as they are, I don't think readers are going to see his comments stacking up with the publisher's or the text itself, even with regard to simple matters like book content. Still, I'm sure you'd rather not see such stuff in the major distributor's presentation, Bob.
I guess it's all part of some "equal-time" policy for airing contrary views as in the public face of many large corporations today.i
Hurtful as they are, I don't think readers are going to see his comments stacking up with the publisher's or the text itself, even with regard to simple matters like book content. Still, I'm sure you'd rather not see such stuff in the major distributor's presentation, Bob.
I guess it's all part of some "equal-time" policy for airing contrary views as in the public face of many large corporations today.i
I did some measurements of speaker distortion at various soundpreasures as requested.
Note that my measurement amp is an inexpensive Alesis and i use a simple M-Audio Transit soundcard so some of the "grass" you see is from my electronics. Nevertheless the measurements confirm in general the monothonic nature of speaker distortion.
There are too much measuement to put in one post so i start here with a measurement of second and thrird harmonic at 75dB and 105dB in 1m. The driver is an Audio Technology 18cm midwoofer with filled Polypropylen membrane in a 35 liter bass reflex cabinet. I measured in 10cm so the soundpreasure scale looks way to high and i did not normalise.
Note that my measurement amp is an inexpensive Alesis and i use a simple M-Audio Transit soundcard so some of the "grass" you see is from my electronics. Nevertheless the measurements confirm in general the monothonic nature of speaker distortion.
There are too much measuement to put in one post so i start here with a measurement of second and thrird harmonic at 75dB and 105dB in 1m. The driver is an Audio Technology 18cm midwoofer with filled Polypropylen membrane in a 35 liter bass reflex cabinet. I measured in 10cm so the soundpreasure scale looks way to high and i did not normalise.
i also looked at harmonic 5 if there is any raise of higher harmonics with level again at 75dB and 105dB.
Here is the Spectral Contamination ( multitone distortion ) at 95dB. And the "Gerhard Test" also at 95dB ( sorry. i did not find a better word for it ). This a a wav. that you can play back.
I got it by putting in 30 frequencies over the range from 20 to 20kHz that are chosen not to stack up harmonics. I them supressed the tones digitally and did an invers FFT on the residuum to extract the time domain signal. I then converted into 16 bit 44kHz wav.
It is a good indicator of rubb and buzz and when you listen carefully you hear the "sound" of the membrane. Note that this distortion is at a very low level and i had to "blow" it up a lot to make it audible.
I got it by putting in 30 frequencies over the range from 20 to 20kHz that are chosen not to stack up harmonics. I them supressed the tones digitally and did an invers FFT on the residuum to extract the time domain signal. I then converted into 16 bit 44kHz wav.
It is a good indicator of rubb and buzz and when you listen carefully you hear the "sound" of the membrane. Note that this distortion is at a very low level and i had to "blow" it up a lot to make it audible.
Hi Ian,
Glad you got your copy and thanks for the kind words.
Negative reviews are just part of the territory. Some will have valid points, others will be a result of too quick a skim, and others may be the result of a technical philosophical difference. Moreover, no book can be complete and without error on every topic. The important thing is just like a vote. If those who like the book will write reviews, then the overall picture of the book will come out as more balanced. When you have only two reviews, one good and one bad, the picture is too lacking of data points. As more people read the book, I hope more reviews will be written.
Cheers,
Bob
Hi Bob,
I'm not sure what this guy is talking about precisely. Perhaps he is referring to Bruno Putzeys:
"A notable disadvantage of phase control is that the modulation is inherently nonlinear, adding distortion at large modulation indexes."
See his article at the end of page two: hypex.nl/docs/ucd_aes.pdf
Cheers,
E.
Hi Edmond,
Greetings from RMAF. I expect to be having a beer with Jan in a short while.
I actually read that paper on the plane on the way here. I think that what was being referred to is a nonlinearity that afflicts self-oscillating feedback class D amplifiers that employ post-filter feedback, like the Hypex. As you know, with a straightforward triangle-reference PWM modulator, linearity of the result requires linearity in the triangle reference signal. In a self-oscillating design with post-filter feedback, the "reference" is the output signal, which is a sinusoid if the input signal is a sinusoid. To some extent, this is analogous to having a rather nonlinear triangle reference in a conventional pwm modulator.
In the paper, Putzeys does not go on to say much about the effect or how it is mitigated in his design, other than the negative feedback that is applied.
Cheers,
Bob
My copy arrived today - I've briefly thumbed through it and am really looking forward to getting my teeth into it over the coming weeks. Great job Bob! Thank you
Hi Bonsai,
Thanks! I'm glad you got the book and I hope you enjoy the read. Jan Didden and I are here at our table at RMAF and the show is really going well.
Cheers,
Bob
Great to know! diyAudio member udailey just texted me a few minutes ago and he mentioned that he had been by your table. Lucky, lucky!
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The show is going very well and Jan and I have met a lot of nice people who are interested in both of our books, and several of each have sold. Attendance is up. I was told it is about 4000. Our table is in a very good location in the lobby close to the registration tables, so traffic is good.
Cheers,
Bob
Hi Bob,
I'm glad the show is going very well and give my best regards to Jan.
I'm not sure whether Ray de Velder is indeed referencing to this phenomenon. There are other schemes as well that produces distortion. For example, when feedback is taken from an output that's not free from switching residuals.
Cheers,
E.
