" We attempted to minimize both AM and FM distortion"
What about PM distortion. It's called breaking the peace. Some think it should be a capital crime. Thump, thump, thump, thump, thump.
Scott, if you will go back to #8352, on this thread, you will find PK's paper on FM distortion, published April 1969 in the JAES. As I was a full member of the AES from 1966 till recently, I read the article at the time. This is why we knew to keep to cone area high, even if we could have had more throw per speaker, at the time. This reduced FM distortion in the speakers. For low horn throat distortion, we did NOT use horns, EXCEPT above 4000 Hz, and then we used a whole lot of powerful EV Tweeter Horns (T350) alnico version and kept the horn throat pressure of each unit relatively low, as well.
When it comes to FM or PIM distortion in amps and preamps, we did NOT know much yet, except for the TIM research of Matti OTALA, that guided me to make successful electronics that could replace the tube drive electronics, previously used. ONLY TIM was considered at the time, BUT the HIGH OPEN LOOP BANDWIDTH called out by Otala, made the circuits that I designed in 1973 successful enough to replace the older tube electronics, and most of Dick Burwen's efforts on behalf of Mark Levinson in the near future.
When it comes to FM or PIM distortion in amps and preamps, we did NOT know much yet, except for the TIM research of Matti OTALA, that guided me to make successful electronics that could replace the tube drive electronics, previously used. ONLY TIM was considered at the time, BUT the HIGH OPEN LOOP BANDWIDTH called out by Otala, made the circuits that I designed in 1973 successful enough to replace the older tube electronics, and most of Dick Burwen's efforts on behalf of Mark Levinson in the near future.
Was it true that the vocal mics were stereo mics
wired out of phase to create a hyper ' nearness boost ' (phrase?)
I lament the disappearance of straight forward audio engineering artiles from the JAES and try to do something about it by publishing Linear Audio on my own money.
So far there's no shortage of high quality articles, just need some more readers to break even
jan didden
You just got one more Jan
was meaning to buy last year when you first announced but then got sidetracked. Should make for good reading on the train to and from work Tony.
As mentioned way back try putting a 10 uf motor run capacitor straight across the AC power line. If this lowers the mechanical noise you will have confirmed it is a dirty power line. The capacitors are available from McMaster-Carr
"if I had to chose from the CES examples, I might well consider horns, as well as direct radiators for a reference system. They were just more 'alive' sounding."
Reminded you of the Grateful Dead then? I guess if that's your idea of high fidelity, to each his own I suppose. Did it make it to 130 db? Ah, those were the good old days.
" We attempted to minimize both AM and FM distortion"
What about PM distortion. It's called breaking the peace. Some think it should be a capital crime. Thump, thump, thump, thump, thump.
Is there any CORRECT technical content to your posts, or do you have a need just to be nasty?
You raise an interesting issue. A load that does not draw equally from both positive and negative swings of the AC voltage such as a single diode rectifier will affect the power quality. I have trouble calling this DC as the local power line is most likely fed from a transformer, so the output must be AC. However the harmonic structure certainly can be modeled as a DC offset.
In the operation of a transformer a DC offset will change the operating points through the BH loop. A well designed transformer will allow for some of this, as well as a transformer operating below full load.
The low quality AC line will interact with the reactance of the various loads in reaction to the unequal diode type load. So the current in the line filter will not be symmetric. As the filter inductor in such a filter is often a bifilar design the offset will affect it much more than a power transformer. The idea being the matching windings cancel, but with an asymmetric waveform that is not true.
So the result of a diode type load is that the reactive loads must absorb the unbalanced power. This can be dissipated as heat or in this case noise. That is why I suggest adding a capacitor to the line as inductance is always present.
So where I think you have correctly identified an important issue, the terminology, although often used, can lead to misunderstandings.
Yes, when the SPL is 130 dba, ten times the threshold of pain, it is unlikely that any sound system reproducing the output of a source sound system which is supposedly the live music could be distinguished from any other sound reproducing system at that level. At such levels, conventional notions of distortion are meaningless, it is the entire idea itself which is a distortion.
Uneven power draw gives different problems on each side of the atlantic as you usually use 3 wire 3 phase and we usually use 4 wire three phase in the UK, the error term causes phase errors between the pairs, whilst we usually get "ground" wire currents.
I know that the american 3 wire 3 phase saved my life once, cleaning out a 600VAC 1,000 amp bay, on planned maintenance dusting down the heatsinks, whilst the next bay had a cover off for air balancing adjustment, and my hand brushed against one of the heatsinks (at 600VAC), it was a very big ouch that threw me across the aisle. The nameplate said "Westinghouse Low Voltage Switchgear"...
Wrinkle
1 130dbc not dba.
2 120dba peak is not usually considered the threshold of pain. It varies with the individual though but I will defer to you as being an expert on pain.
3 A woofer at that time would be about 92 db/w at 4' with a maximum output of 115 db at 4' or less.
4 It is the equivalent point source that would have been equal to 130dbc peak. Note the MF is above ear level.
5 An spl measurement of a loudspeaker without a distance reference is meaningless.
6 The spl at the front of the audience might peak at 110dbc and average 90dba.
7 It is at the back of the audience that distortion is less important as the high frequency attenuation of the air could exceed 20 db.
8 At 90dba distortion perception would be close to optimum as regards ambient noise s/n+n ratio.
A nice picture was just posted, it makes it clear how the system was designed.
Your mpl rating is 2!
The average temperature of the earth for all I know may be 40 degrees F but it doesn't matter much when you're in Death Valley when it's 140 degrees.....or in Antarctica when it's 100 below zero. The average age of Americans may be forty or fifty. I'll remind you of that when you'r 99....if you live that long
He said the SPL on stage where he was was 130 db. He didn't say A or C weighted or unweighted as I recall. Frankly I for one believe him about that. Macho man.
For me the threshold of pain when the grateful dead are playing is....anything above zero db
My ears will be grateful when they're...............not in earshot.
I guess you weren't the one with whom I was competing for tickets. I saw them live perhaps a dozen times- the sound at the shows was pretty good for that sort of thing. The music varied from indifferent to genius, sometimes in the space of 15 minutes. But fine, if you don't get it. I don't get techno. Or rap. Or "audiophile music."
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