Hi Lynn
My apologies not getting back to you, going to ETF18 in Normandy and the last week has been crazy getting things done and leaving tomorrow. Will be seeing a number of people before ETF starts on 15th.
Your overhung versus underhung comments interest me. And I agree with the points you make because they are obvious. The best driver should be underhung, but if only it was that easy. This story indicates why:
Last year I went visiting SB Acoustics in DK and the topic came up when conversing with their designer Ulrik Schmidt - because I had noted that he only designed overhung voice coils (but highly symmetrical drive) and I made the point that underhung drivers has noticeable lower sensitivity for the same respective impedance (4 or 8 Ohm) and that it must be because of the magnetics in a long gap makes for weaker concentrated magnetic circuit. He confirmed that. So for a given dB-SPL the voice coil gets hotter. The low sensitivity, this is why he stuck with overhung, and he said you can only go so far in getting a strong magnetic circuit in underhung. I suppose we all do with what we are comfortable with.
But with underhung, the heat will also be distributed more evenly, as heat convection along the entire length of the coil across gap. I consider that a good thing, even if there is more heat to dissipate. So this is swings and round-abouts. But I like voice coils to run cool, I like a lot of surface area, so that excursions are OK at my listening levels. I do prefer a Bessel like vented alignment, interfaces well with the room, keeps excursions down, I tune low 30s Hertz and OK down to 25 Hertz. so sub 25 Hertz? Well, you have a point about that limitation. But still way fuller range than 99.9% of speakers out there.
Cheers, Joe
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Recent OT posts about amplier back-emf and load impeadnce have been moved here:
Back-EMF and flat impedance
In case of amplifiers, THD levels are so low that they almost never get above the average level of noise in listening room (which is usually 20-30 dB)...
I noticed that for loudspeakers THD measurements are always made in relation to frequency.
But I wonder, what results could bring measurement of THD vs power?
That is, if you measure like for an amplifier...
I can hardly find such measurements of tweeters, but but I have never come across such a measurement of midrange or bass speaker.
Perhaps there would sometimes be interesting results that would help in the selection of a transducer for DIY project?
I noticed that for loudspeakers THD measurements are always made in relation to frequency.
But I wonder, what results could bring measurement of THD vs power?
That is, if you measure like for an amplifier...
I can hardly find such measurements of tweeters, but but I have never come across such a measurement of midrange or bass speaker.
Perhaps there would sometimes be interesting results that would help in the selection of a transducer for DIY project?
This statement requires a flat-earth approximation of THD. I'd let it go through to the keeper if it wasn't leading you to an erroneous conclusion.
See:
Crowhurst, N. H., 1957 Some Defects in Amplifier Performance Not Covered by Standard Specifications JAES 5(4)
Hamm, R. O. (1973). Tubes Versus Transistors-is there an Audible Difference. JAES, 21(4), 267-273
Temme, Steve, 1992, "Audio Distortion Measurements" Brüel & Kjær application note.
As a meme it should be long dead. Unfortunately, various marketers keep pulling the stake out of the corpse and reanimating it.
If you want to know about the gross distortion mechanisms in speakers (short of reading all of this and related threads) start with Wolfgang Klippel's recent works. Siegfried Linkwitz also deserves a read, if you can keep up with his math.
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Thanks, but the basics of knowledge about linear and non-linear distortions and the problems of their audibility, I know probably well, I think.
I read the studies of both canonical authors and some of the latest research on this topic.
(unfortunately, what bothers me the most is largely ignored in the available literature)
As an advocate of experimenting, I also tried to research myself on how far the harmonic distortions from the amplifier and speakers (as well as the undesirable components from the aliasing from the digital part of the track) can be audible in my listening room.
It consisted in recording technical signals with a microphone in the near field as well as in the spot of optimal listening.
Then, using steep digital filters, I cut out the fundamental components and listened to the isolated distortions themselves.
Cranking up the volume accordingly to the needs.
Of course, in this simplistic way you can only scratch the surface of the problem of distortions, and it is not worth dealing with the range where the wavelength begins to be comparable to the size of the room.
My amplifiers in combination with the loudspeakers produced some measurable and audible distortions, but fortunately it was mainly the second harmonic.
Unfortunately, I did not have loudspeakers with a passive analogue crossover at hand.
I could notice then some IMD distortions, as well as those resulting from the lack of electrical insulation of the speakers (but that's just a guess).
Sadly, my listening room is pretty noisy in absolute terms (mainly because of highways 3-4 km near the house, I think).
Audiophiles with solidly built houses located in a quiet area could have reached quite different conclusions...
I read the studies of both canonical authors and some of the latest research on this topic.
(unfortunately, what bothers me the most is largely ignored in the available literature)
As an advocate of experimenting, I also tried to research myself on how far the harmonic distortions from the amplifier and speakers (as well as the undesirable components from the aliasing from the digital part of the track) can be audible in my listening room.
It consisted in recording technical signals with a microphone in the near field as well as in the spot of optimal listening.
Then, using steep digital filters, I cut out the fundamental components and listened to the isolated distortions themselves.
Cranking up the volume accordingly to the needs.
Of course, in this simplistic way you can only scratch the surface of the problem of distortions, and it is not worth dealing with the range where the wavelength begins to be comparable to the size of the room.
My amplifiers in combination with the loudspeakers produced some measurable and audible distortions, but fortunately it was mainly the second harmonic.
Unfortunately, I did not have loudspeakers with a passive analogue crossover at hand.
I could notice then some IMD distortions, as well as those resulting from the lack of electrical insulation of the speakers (but that's just a guess).
Sadly, my listening room is pretty noisy in absolute terms (mainly because of highways 3-4 km near the house, I think).
Audiophiles with solidly built houses located in a quiet area could have reached quite different conclusions...
I have on some forums brought up the topic and gotten trolled about this, but since the individual driver are current devices, then the distortion of the amplifier would only show up if the distortion also occurs on the current side. Please think about it, the dB-SPL of the driver we hear (loudness) at any frequency, is relative only to the current through the voice coil and not the voltage across the voice coil. So if the voltage has, as a thought experiment, zero distortion (assuming a perfect voltage source), then the current can still be corrupted by a current that deviates in its phase angle from that of the voltage (non-resistive) and hence harmonic distortion of an imperfect driver will show harmonics (and hence THD) on the current side, even if the voltage source has zero voltage THD.
Since all drivers are imperfect, they will create current distortion from the amplifier. The better the driver, less will be that case. Alas, it will only happen when drivers are purely resistive in load. One thing to look for in a driver, any driver, is low inductance - and this will be an indicator of a superior driver in most cases.
As you've discovered, the harmonic bits (particularly 2nd 3rd and 4th ) are not something our head considers important. 5% 2nd on a single tone instrument is almost inaudible. 3rd is more audible than 4th. Etc
IMD (aka blur, grunge, lack of clarity) is more audible, particularly on massed works, e.g. choir + organ).
What's really audible (see Steve Temme) is stuff that's basically unrelated to the music - in his case they could hear cone rub over 60db down and were trying to work out an instrumentation method to detect it.
This stuff includes all sorts of sins including various forms of clipping and limiting; bias-shift-induced crossover distortion and power supply "noise".
All of the above is then subject to Messrs Fletcher and Munson
Indeed! The tuning phase has a huge psychological effect on me.
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I like this idea! It fits with the aesthetic I employ in my recordings.
On one of solo piano, where we knew we were recording the last piece on the intended CD, the pianist and I agreed that he should hold the last chord (of his own composition) until he could not longer hear the piano strings at all before he released, then quietly get up and walk off stage and close the heavy sound-proof door before I stopped recording. It worked quite well! It also took nearly a minute, if I recall, for the piano to become effectively silent.
Also, whenever I made CDs, I always tacked on at least 30 seconds of silence at the end of the last track, space permitting. I have always thought it inappropriate to break the listeners' reverie the second the last piece ends with the sound of the CD player going through its dance, and in a car, most players go immediately to the beginning of the CD which is not doing justice to the music, in my opinion.
The short abrupt transitions are so jarring, so unnatural. At least to me. Many people I see just right into the next thing with no pause - be it music, a film or whatever.
When I grew up Concerts on the BBC Third Programme always included the initial tuning up. The silence before it starts has you on the edge of your seat.
So, after 12 years...
Let me start by saying that this has been an enourmously informative and valuable thread, at least for me. So there's that, for sure.
And I also remember that at some points throughout this thread there have been some discussions of various "Beyond the Airel prototypes", and at least one (semi?)final version has been built by Gary Dahl.
But how about the originator of the thread?
Has Lynn finally finished his own version of the BTA loudspeaker system?
Or has he ditched the whole project? And if so, why?
Just curious.
Let me start by saying that this has been an enourmously informative and valuable thread, at least for me. So there's that, for sure.
And I also remember that at some points throughout this thread there have been some discussions of various "Beyond the Airel prototypes", and at least one (semi?)final version has been built by Gary Dahl.
But how about the originator of the thread?
Has Lynn finally finished his own version of the BTA loudspeaker system?
Or has he ditched the whole project? And if so, why?
Just curious.
I wonder too, as many of us have probably also moved on. DHT versus SS perhaps remains with us to some degree. Ref prev quote BBC R3 remains the live music performances and pauses are very useful
To a large degree this thread has served as a pretense for Lynn to muse about speaker design. Insofar as his posts serve as food for thought, there is still some value to be found in this thread.
Otherwise, yeah, I think GPA substantially raising the cost of the 416-8B put the final nail in the coffin for anyone already ambitious enough to replicate a build where difficult to obtain and/or costly components are a noteworthy part of the terrain.
Coincidentally, a pair of drivers originally built not only for an early iteration of this project but for Lynn personally are currently for sale elsewhere on this forum.
Otherwise, yeah, I think GPA substantially raising the cost of the 416-8B put the final nail in the coffin for anyone already ambitious enough to replicate a build where difficult to obtain and/or costly components are a noteworthy part of the terrain.
Coincidentally, a pair of drivers originally built not only for an early iteration of this project but for Lynn personally are currently for sale elsewhere on this forum.
+1 on Brinkman's comments. Last time I looked at it (about 500 pages ago ) we were north of US$10K for parts. I normally multiply that by 5 or 10 for a rough idea of a COTS price.
But if you're looking at PP 300Bs IT driven by NOS PP45s cost is something you've already come to terms with.
For me, (as an Ariel owner and feckless fiddler), it's given me and understanding of at large drivers behaviour and a reason to look at them again. And between the various key players, a much better understanding of how to get horns working, should I go that way.
But if you're looking at PP 300Bs IT driven by NOS PP45s cost is something you've already come to terms with.
For me, (as an Ariel owner and feckless fiddler), it's given me and understanding of at large drivers behaviour and a reason to look at them again. And between the various key players, a much better understanding of how to get horns working, should I go that way.