That was the sub :Audio Physic Rhea powered subwoofer | Stereophile.com
Unfortunately no measurements.
Unfortunately no measurements.
Henry Kloss in one of his late interviews (Audio magazine) was asked about the innovation and progress with speakers during the last decades.
He replied: “It’s the adhesives that have become much better”
Thank you. See this paper:
http://www.aes.org/tmpFiles/elib/20140828/7059.pdf
(especially equation 22 and Fig.5)
"Current-Driving of Loudspeakers" is IMO a very good book, regardless of the adoption or rejection of current drive approach.
George
One might use N.P.'s approach :
Start with a relatively pure current source amp
and add output networks to fit speakers ...
http://www.firstwatt.com/pdf/art_cs_amps.pdf
Start with a relatively pure current source amp
and add output networks to fit speakers ...
http://www.firstwatt.com/pdf/art_cs_amps.pdf
550? Guess, I should get one of them.
I also need to invest in a large test equipment warehouse.
-RM
An old post …
My favorite example. These signals differ only in phase of one of the spectral components. For absolutely identical amplitude spectra, we get totally different time domain signals. One of them will push the amp to clipping, the 2nd will not .....
One has to be careful when working with amplitude spectra only. It is only a half of the necessary information.
George
Metal with a mu close to 1 will actually cause a reduction of an air core coil. It does so by flux exclusion ala Lenz effect. I put measurements of this in my gallery.
If the external magnetic field of the speaker is time varying, an air core can experience proximity effect resistive increase, which can be rather non linear. Also, if it couples enough, I've no idea what the resultant response would be.
I do know that my eminence delta 12's modulated a CRT television picture located about a foot from the speaker cab when driven at about 300 wrms, so unshielded pro drivers certainly play loosely when it comes to flux containment.
jn
Thanks for the information and confirmation of an unshielded magnetic speaker magnets flux field. I wonder if people have sort of forgotten about what a large magnet from a speaker can do since most people have flat screen TV's and computer monitors these days, I haven't placed a large magnet near a flat screen TV or monitors to see if there is still some kind of effect. I did get my *** chewed out once for placing a raw frame 15" speaker next to a computer but nothing happened.
Well that sure does suck big time.
Wanna start it up again? Using my TC Sounds (18 incher)? Dual 2 Ohm coils. THx-RNMarsh
Here is a question, relevant to both speakers and microphones. Many years ago I read that mixing an dynamic mike with a condenser mike on the same instrument was problematic because of the phase relationship of the pressure wave to the electrical output. A dynamic mike has its peak out out at the fastest changing part of the waveform- the zero crossing. The condenser at the peak of the pressure wave, 90 degrees different. I have never verified this, no need to, but it sounds reasonable.
Could the same be true for voltage and current drive of a speaker? And in the current amplifier, is the peak current at the peak of the input voltage wave? The few experiments I have tried in the past had a good phase/amplitude correlation of the current driving a speaker (dynamic and electrostatic) and the voltage wave from a condenser mike in front of the speaker.
This could lead to more angst than getting absolute phase of the playback right. You need an electrostatic speaker for recordings made with condenser mikes and dynamic speakers for dynamic mikes. Or is it the other way? What about carbon mikes?
A barometer works like a mic too, not well but some have ~3K response. Remember the particle amplitude of the air also goes 6dB/octave.
I read the same thing many years ago in the 'Handbook for Sound Engineers'. The explanation as far as I remember is that because of the different phase relationships, the stereo image goes out of whack.
Peak current will not always be at peak voltage wave. It is a minimum phase system so impedance variations of the driver get translated into phase shifts of the current. I am toying with this ideaof current drive in my head for a long time, so this is why I thought stability would be a complication.
Now, Hitsware was kind enough link to Nelson Pass's site (thanks!). I wasn't aware of his work in this field, but his solution is elegant. He puts a compensation network (coils, caps and resistors) in front of the driver, which exhibits the inverse peak. This would also correct the phase relationship between voltage and current I suppose, so that is a neat and simple way of dealing with it.
No, with an electrostatic loudspeaker you have to sit 1/4 wavelength further away, so that the phase relationship gets restored
p.s. Howie, thanks for the positive recommendation of the book - just ordered my copy - and hope you will be able to relaunch your research.
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Any compensation network across the driver reduces drive impedance so works against current drive. The idea is to short out the back EMF as little as possible - so there is a minimum source impedance that is useful for current drive. Crossovers work against this as well.
FR can be taken care of using a compensation network at the amp input or even the feedback loop if it's a dedicated amp. A modular input compensator could be made with enough knobs to compensate any speaker, without reducing drive impedance at all.
As for amplifier stability, it is not a problem with current drive, just a change in the compensation scheme.
FR can be taken care of using a compensation network at the amp input or even the feedback loop if it's a dedicated amp. A modular input compensator could be made with enough knobs to compensate any speaker, without reducing drive impedance at all.
As for amplifier stability, it is not a problem with current drive, just a change in the compensation scheme.
Demian Martin:
>Many years ago I read that mixing an dynamic mike with a condenser mike >on the same instrument was problematic because of the phase relationship >of the pressure wave to the electrical output. A dynamic mike has its peak >out out at the fastest changing part of the waveform- the zero crossing. >The condenser at the peak of the pressure wave, 90 degrees different. I >have never verified this, no need to, but it sounds reasonable.
This is my belief too.
It is what physics predicts.
>Could the same be true for voltage and current drive of a speaker?
JAES Volume 12 Number 4 October 1964 Page 348:
F.K Harvey, Bell Telephone Laboratories, Inc., Murray Hill, New Jersey
SNIP
"It should be pointed out that the measuring microphone (The condenser pressure omni measurement mic, my comment) is generally free of phase distortion, the ordinary direct radiator loudspeaker is not. The latter is generally operated above resonance (mass controlled), and thus provides a minimal 90° phase shift (0.25 wavelength) at most frequencies throughout the useful range.
In such a loudspeaker, the mechanical driving force in phase with the electrical current. However, the diaphragm velocity is 90° out of phase with this force and its magnitude drops 6 dB/octave .
It is purposely designed in this way so that the product of the velocity squared and the air radiation resistance (rising 12 dB/octave) tends to provide a constant acoustical power output up to the point where the dimensions of the diaphragm become comparable to the wavelength.
It is generally overlooked that one of our most popular loudspeaker designs possess an inherent 90° phase distortion.
Consequently, preservation of the complex waveform is impossible, even in free space, except with the aid of preliminary amplitude independent phase correction. (using an all pass phase shifter giving a constant 90° phase shift but having a flat frequency response, my comment).
Snip
>This could lead to more angst than getting absolute phase of the playback >right. You need an electrostatic speaker for recordings made with >condenser mikes and dynamic speakers for dynamic mikes.
Yes.
But dynamic mics have problems of their own so sounds different because of the dynamic mic defects not inherent in condenser mics.
--
Best regards,
Goran Finnberg
The Mastering Room AB
Goteborg
Sweden
E-mail: mastering@telia.com
Learn from the mistakes of others, you can never live long enough to
make them all yourself.*** -** John Luther
(\__/)
(='.'=)
(")_(") Smurfen:RIP
>Many years ago I read that mixing an dynamic mike with a condenser mike >on the same instrument was problematic because of the phase relationship >of the pressure wave to the electrical output. A dynamic mike has its peak >out out at the fastest changing part of the waveform- the zero crossing. >The condenser at the peak of the pressure wave, 90 degrees different. I >have never verified this, no need to, but it sounds reasonable.
This is my belief too.
It is what physics predicts.
>Could the same be true for voltage and current drive of a speaker?
JAES Volume 12 Number 4 October 1964 Page 348:
F.K Harvey, Bell Telephone Laboratories, Inc., Murray Hill, New Jersey
SNIP
"It should be pointed out that the measuring microphone (The condenser pressure omni measurement mic, my comment) is generally free of phase distortion, the ordinary direct radiator loudspeaker is not. The latter is generally operated above resonance (mass controlled), and thus provides a minimal 90° phase shift (0.25 wavelength) at most frequencies throughout the useful range.
In such a loudspeaker, the mechanical driving force in phase with the electrical current. However, the diaphragm velocity is 90° out of phase with this force and its magnitude drops 6 dB/octave .
It is purposely designed in this way so that the product of the velocity squared and the air radiation resistance (rising 12 dB/octave) tends to provide a constant acoustical power output up to the point where the dimensions of the diaphragm become comparable to the wavelength.
It is generally overlooked that one of our most popular loudspeaker designs possess an inherent 90° phase distortion.
Consequently, preservation of the complex waveform is impossible, even in free space, except with the aid of preliminary amplitude independent phase correction. (using an all pass phase shifter giving a constant 90° phase shift but having a flat frequency response, my comment).
Snip
>This could lead to more angst than getting absolute phase of the playback >right. You need an electrostatic speaker for recordings made with >condenser mikes and dynamic speakers for dynamic mikes.
Yes.
But dynamic mics have problems of their own so sounds different because of the dynamic mic defects not inherent in condenser mics.
--
Best regards,
Goran Finnberg
The Mastering Room AB
Goteborg
Sweden
E-mail: mastering@telia.com
Learn from the mistakes of others, you can never live long enough to
make them all yourself.*** -** John Luther
(\__/)
(='.'=)
(")_(") Smurfen:RIP
Hi Scott,
A few years ago I asked the question on this forum "anyone know the frequency response of air" none of the answers at that time indicated to me that there was a clear understanding of this.
Does your comment above mean that this is well understood by yourself ?
If so, could you explain some more ?
Since quite a long time i have an idea that could reduce distortion in loudspeakers.
Second harmonic comes from asymmetries.
I learned from Klippel that this can also be seen as a DC shift.
My idea is to make a power amp that has adjustable DC Offset.
That offset could be used to partial cancel second harmonic.
Maybe not under all conditions but it is worth a try.
Second harmonic comes from asymmetries.
I learned from Klippel that this can also be seen as a DC shift.
My idea is to make a power amp that has adjustable DC Offset.
That offset could be used to partial cancel second harmonic.
Maybe not under all conditions but it is worth a try.
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