Instant dismissiveness on some persons behalf is to be expected. But we know that current driving a speaker, with all its fraught problems, actually prevents the back-EMF impedance of the driver opposing current. Voltage drive is affected though. Why are we not allowed to examine those mechanisms and look for alternatives? And no, it does not waste a lot of power if done properly. Many loudspeaker system designers use large parallel resistors that have to be huge, I can mention names, and they DO waste a lot of power. But an elegant EQ of current is actually quite frugal.
OK, but sometimes persistence is a virtue. Others can call it other things. All depends where you are coming from and where you are going. But I am getting both great encouragement and also negative attitudes. I expect it - that is just how things are.
Cheers, Joe
I guess that you need to consider if all the opinions carry the same weight.
The fact that shunting an ideal voltage source with any network does not change its output impedance is not an opinion. There are two issues here, Joe's speakers might sound fine or great to lots of folks even me and could even provide a great value but the invalidation of basic principles is not involved.
you guys are talking way above me in terms of AE & EE, but the entire goal of audio is not measurement, it is sound reproduction - does it sound good?
i have heard good sound since the 1970's. is audio better now? yes, but not so much. we no longer need to clean LPs with a discwasher. we can stream video and audio. we can record to digital files and save them forever, etc.
is all of this discussion about current driven vs voltage driven an example of OCD or is it about improving audio?
i said goal not correlation. if you weren't around for audio in the 70's, you missed an very exciting time. sound was good, but sound is better now.
and since you introduced correlation, i wonder if there is a correlation between current/voltage amplifiers and OCD?
I still have some of the stuff from back in the 70’s. So I know and compare. Actually, insufficient improvement is why I jumped into audio tech development.
You have a goal, but you also need appropriate measurement and data analysis to make sure one is constantly in the right direction.
Will I go back to look at old equipment? Not unless I hear certain qualities that are not in my current designs, which up to now has not happened.
you guys are talking way above me in terms of AE & EE, but the entire goal of audio is not measurement, it is sound reproduction - does it sound good?
i have heard good sound since the 1970's. is audio better now? yes, but not so much. we no longer need to clean LPs with a discwasher. we can stream video and audio. we can record to digital files and save them forever, etc.
is all of this discussion about current driven vs voltage driven an example of OCD or is it about improving audio?
And that I have certainly considered, so now I perhaps needs to get a bit more detailed about that.
So, I have spoken to many and gotten some really interesting discussions, both with people who design speakers and amplifiers, several physicists and academics and more. And it has not been a waste of time, a number of things were put aside because they did not stack up. Getting beyond the noise, because there is no shortage of diversion of ideas, and many are just that and no more, diversions.
I decided I should concentrate only what the current does and what an impedance does to the current. An impedance is something that impedes current, not voltage. An impedance curve is about what happens to the amplifier current wise, yet the amplifier has no control over current. That has to be thought through, because to control the voltage, it cannot control the current.
The problem is that it is simply not possible to present a full case on social media, that just doesn't work. So I have put together some very detailed discussion papers with huge numbers of measurement and have also used SoundEasy modelling that shows agreement - but based on actual physical measurements, you know, actually getting microphones out in front of a speaker, no short-cuts here. And it all tallies up.
I devised an 'equivalence' test that would mean that the only change in dB-SPL was caused by the impedance above Re. The test can also be done on full speaker system but is most revealing with a single driver. The equivalence is that between current and voltage drive and they should give the same dB-SPL, the same frequency response if you will. The change is caused by the back-EMF impedance in a single driver only, it isolates it as the only cause of the change in dB-SPL. It worked, but also revealed a number of things, but I doubt suitable for a social media free-for-all, not that I have not, in the right spirit, being willing to listen, most often one-on-one, because that works best most of the time.
The numbers were collated and the change in dB-SPL correlated directly with the change in current. At 3KHz the change was 9dB and the change in current was 3:1 - I could pick any frequency and do the maths, at any frequency, even LF, total correlation. Very pleased indeed.
The 'equivalence' test has been looked at and checked by others that I respect and it does indeed seem to stand up.
They also stand up, and this should interest you, when you calculate the dissipation in Watts. I mean, this is intriguing, not just is there a correlation between the current and dB-SL, there is an exact correlation of the heat dissipated in the voice coil and the dB-SPL of the driver. This can be calculated by the voltage that occurs across the Re part of the voice x the current flowing through the voice coil. The maths are so basic that it brings a smile to your face. Again, this was passed by my 'superiors' if you like.
But I don't consider myself 'home and free' because with a subject like this, that may never happen. But I am still glad I did it, and it has not been wasted time. And it makes great discussions over a beer. Like "Do you realise...."
But what I have mentioned here is just the tip of the iceberg. The behaviour of that back-EMF impedance, the part of the impedance above the Re value, this is where the real problem is, and I have barely touched on that, but have in previous posts: The current fluctuates because all the current runs through a series of impedances, starting from the Zo of the amplifier, then the back-EMF impedance of the driver, then the rather stable Re. The Re is not the problem, the back-EMF impedance is. All the flaws of a driver (and indeed the speaker system) shows up in the back-EMF impedance, causing the current of the amplifier to react to those flaws, the final current corrupted ends up at the figuratively end of the chain as 'wronged' current and the Re gets it. Here at Re the 'equivalence' test shows conclusively that we hear is the current, because it is what correlates with the dB-SPL of the driver, measured with an actual microphone. The overall impedance of the driver is not stable because of that back-EMF impedance, because these element are all in series. Hence, the current cannot be entirely stable, not dynamically, because the back-EMF impedance is part of that chain.
Again, if not taken seriously here, I can assure you that elsewhere it is being looked at, and there is some reasonably sound thinking behind it. And great discussions too. Taxing one's own thoughts and that of your friends, kinda good.
Now, who of you here are going to guide me to the chopping block?
Cheers, Joe
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i have heard good sound since the 1970's. is audio better now? yes, but not so much. we no longer need to clean LPs with a discwasher. we can stream video and audio. we can record to digital files and save them forever, etc.
is all of this discussion about current driven vs voltage driven an example of OCD or is it about improving audio?
I was around in the 70's and working for Hago-Hagemeyer, Panasonics, Technics, JVC. The second have of the 70's brought back tubes.
All this current versus voltage drive, it's a schamozzle and you are right, it only passes muster if the sound gets better.
a few years back i bought a pair of Polk 7c in nearly perfect condition off craigslist for $60. read that they were matthew polk's favorite speaker. 2 years back i mounted them on a wall, each one hung by one of the heavy duty swivel tv stands.
the sound - really good?! wall mounting speakers really improves the sound. this is not mentioned much in DIY since you can't build some of the really great horn loaded enclosures into a wall.
the same year i bought an onkyo integra surround receiver in perfect condition w/ remote for $60 off ebay. new the unit cost ~$1k. no hdmi, but optical in. also really good sound!
could not have made a decent pair of speakers for $60, or an amplifier for $60.
some things are about perspective and timing.
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