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capacitor phools




 
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WBear2GCR
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« Reply #100 on: May 12, 2008, 02:50:35 PM »


I was wondering if anyone has had the experience of being on the air, particularly on one of the higher bands, 20, 15, 10 and tuning up or calling CQ on a frequency only to find out that there was a QSO on that frequency that you couldn't hear because of either your antenna gain (you're on a dipole, they're on beams) and/or they're all on tall towers also and you're not?

I've noticed that the guys with big beams on tall towers consistently hear more DX on those bands, and work more DX on those bands compared with me or anyone else with a lower gain ant and lower ant than they have...

The correlation is in concept only, but seems to me the sort of thing that is going on here with folks who with good reason are incredulous about the ability to discern differences in things like "exotic" capacitors. The point being that if you didn't hear the other guy working the DX and only had your own rig to make a determination with as to what was or was not on the band you'd naturally think the band was dead. Same thing with the caps in concept. That's all there is to it. It's as simple as that.

If you need a technical basis for this happening, the link I posted earlier provides that.

As far as changing any minds, not sure that's possible if your mind is made up in advance though... and that's not actually my aim. The idea was to illuminate the issue and point out that while there may be some things in audio that are "BS" or "snake oil" there are far more that are not and have a solid basis. This is one of the latter.

Where I differ is when the tone and nature of the discussion becomes derisive across the board toward all things audio that are "exotic" or "high-end".

For almost all applications in ham radio and most home audio it makes absolutely no difference which cap type you use, as long as it is generally appropriate for the circuit.

                     _-_-Wrabbit Bear 2 Gorilla Cheetah Rabbit



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kb3nqd
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« Reply #101 on: May 12, 2008, 05:28:31 PM »

as the thread starter, I'm requesting it be locked and allowed to fade away. Everyone's had their say, and no minds have been changed.

Please lock it up and allow it to die a dignified death.

Not that my opinion would matter that much but I second Derb's motion....All in favor?
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KA1ZGC
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« Reply #102 on: May 12, 2008, 05:30:30 PM »

DADDY!! Timmy took our ammunition away again and he won't give it back!!!
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af6im
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« Reply #103 on: May 12, 2008, 06:52:50 PM »

Damn. right off Digikey's site.

Quote
ELNA developed new raw material for the separate paper which uses a silk fiber. Therefore, this series can give high grade sound for any audio design. This series can be used to relieve the musicís vibration energy, to decrease the peak feeling sound at high compass, rough quality sound at middle compass and to increase massive
sound at low compass.


800 thread count Egyptian cotton fabric coated with oak gum varnish is best for separating the cap plates. Has to be from cotton harvested at the Northern end of the Nile Valley. The cotton from the other regions gives a brassy sound which is OK for sax, horns and rock guitar, but is wholly unsuitable for cello and viola.

Wait for next year: Peltier cooled RCA plugs. You heard it first on AMFONE.



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Opcom
Patrick J. / KD5OEI
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« Reply #104 on: May 12, 2008, 08:35:20 PM »

That is funny. In closing (maybe), here's a picture of one of my speakers. They are 4x2x2 FT. Note that there are no silk capacitors in them. All the drivers except the woofers are from a set of old Pioneer HPM-150's. The cylindrical space-age-looking tweeter is around here somewhere, I didn't use them. The speakers are sitting on 1 FT tall aluminum chassis video monitors. These make good stands.

The only problem is that the 14 cu. FT of the box devoted to the woofer is too much volume for them and they get unloaded at low frequencies (too much excursion). This is very annoying when trying to use the R-390A to extract the deep bass sound of the embedded secret and very narrow PSK signal out of the Russian AM shortwave radio station's carrier. If someone can suggest somethig there, it would be welcome. There is enough room for an 18" woofer.

The coil hanging down is part of an antenna  coupling coil I used in here for a while with a shortwave radio. It is made of CAT-5 cable. I ran a wire loop around the living room ceiling, and put it through a pair connected as a single wire, and then used another pair similarly between the radio's antenna input and ground. It got rid of alot of noise.

The rack on top of the speaker with the 4-#10 wire is for the 120VAC from the 20A air conditioner wall plug to the stereo and everything else in the corner. The power boxes came from a VAX and a PDP-11.

The two top units in the rack are the Ling 850 watt shaker table amps for bass, and in the bottom where can't be seen because of the door and fan cooling arrangement, are two Altec 175W tube amps. They drive the crud out of the midranges and tweeters. Every time I fire them up, maybe once a month, the crud just falls right off.


* my_speaker.jpg (77 KB, 480x640 - viewed 1007 times.)
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WBear2GCR
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« Reply #105 on: May 13, 2008, 12:49:17 PM »

Opcomm,

Consider a high pass filter at 6dB or 12db/oct to eliminate the over excursion... you'd set the -3dB point at just below the resonant frequency of the port

Otoh, optimizing the cabinet volume vs. T/S parameters might alleviate the over excursion problem.  One can derive the T/S params with a few relatively simple bench tests.

It's not the diameter of the driver that matters, it's the Xmax (maximum linear excursion) of the driver and the T/S params for the driver + cabinet which will determine the limit of the power WRT frequency for the combination... there are freeware simulators that will pop this out instantly in graphical form as you change the box volume and/or T/S params and power input.

                _-_-bear


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wavebourn
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« Reply #106 on: May 13, 2008, 04:45:47 PM »

Just put a memory foam mattress inside, that's it.
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« Reply #107 on: May 13, 2008, 09:39:26 PM »

Opcomm,

Consider a high pass filter at 6dB or 12db/oct to eliminate the over excursion... you'd set the -3dB point at just below the resonant frequency of the port

Otoh, optimizing the cabinet volume vs. T/S parameters might alleviate the over excursion problem.  One can derive the T/S params with a few relatively simple bench tests.

It's not the diameter of the driver that matters, it's the Xmax (maximum linear excursion) of the driver and the T/S params for the driver + cabinet which will determine the limit of the power WRT frequency for the combination... there are freeware simulators that will pop this out instantly in graphical form as you change the box volume and/or T/S params and power input.

                _-_-bear




I should say there's no port. The hole is for the mid and tweeter controls. That part of the enclosure is the space for the open-back mids. I'll look at the other stuff, thanks.
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WBear2GCR
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« Reply #108 on: May 14, 2008, 12:35:51 PM »

If it is a sealed box it will try to roll off at some frequency determined by the VAS (equivalent volume of the driver's displacement), fs (free air resonant freq) and the box volume, Vb, at 12dB/oct below that freq. But because this box is likely very large WRT the driver's VAS, it won't control the cone at a high enough frequency.

Bottom line is that the driver must be matched to the cabinet volume for a sealed box to operate properly, and that can only be determined using T/S parameters - the best way is to use one of those simulation programs (of which there are many now).

Or just use a highpass filter to limit the electrical energy going to the driver, and so decrease the excursion at freqs low enough to be a problem (like anything below ~20Hz. is a good idea here). A nice butterworth HP 4th order IC filter would work fine in series with the line going to the amp.


            _-_-bear
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wavebourn
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« Reply #109 on: May 14, 2008, 06:59:55 PM »

Again, the same like you add a resistor to your tuned circuit to lower it's Q add sound absorbing material inside of your box. The memory foam is the best I've found (it absorbs wide band of freqs). Also, if walls of your cabinet resonate (no doubt they are) glue a linoleum inside of them. HPF below Fs is *: speakers already roll off 12 dB/oct below Fs.

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WBear2GCR
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« Reply #110 on: May 14, 2008, 07:28:19 PM »



Wavebourn, stuffing the box with absorbant foam will do one of two things depending on the actual acoustic effect of said foam vs. frequency. Usually foam of any sort unless it is extremely thick has nil effect at LF, or put another way, as the frequency goes higher it usually absorbs more sound.

IF it is a good absorber at LF, then it will make the box appear larger which is likely the opposite of what is needed in this instance (probably). If it is a bad absorber at LF then it serves to reduce the box volume at LF which may be what is needed here, but that's probably not the best way to accomplish it - although unintended as it may be an ideal combination of bad LF absorption and good HF absorption could be an interesting way to "adjust" box volume and reduce rear radiation at the same time, but hard to control or measure in simulation (as in, how much, how thick, what density, etc...).

In terms of absorbing the rear midbass and up radiation from a driver, reducing reflections that re-radiate (in essence as "distortion"), if that's what we're talking about absorbing that energy is a good idea.

These speakers roll off in terms of frequency response or SPL[/u] below F3 not Fs at 12dB/oct, but NOT in terms of EXCURSION. The excursion actually continues to increase even though there is no increase in acoustic output.

Watch ur language please.

              _-_-bear
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WBear2GCR
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« Reply #111 on: May 16, 2008, 03:40:33 PM »


Mmmmm... I think what I wrote is not.


Quote
F3 is the frequency on which roll-off is 3 dB. I.e. already below peak response that happens on Fs that is Frequensy of Self resonance. Why F3? Because people assume that roll-off less than 3 dB is inaudible.
But it does not mean that no roll off between Fs and F3. It is already 3 dB (or much more, if 3 dB is measured against an average response)!

F3 is not because "people assume that roll-off less than 3 dB is inaudible."
It is because it a verifiable measurement of rolloff IN THE BOX.

Fs on the other hand is FREE AIR RESONANCE. No Box.

Quote
Excursion of a speaker is maximal on Fs. By definition (Frequency of self resonance).
You probably sing an aria from a different opera: there is an approach of equalization where in order to force speakers to work below Fs equalizers are implemented that boost signals below Fs 12 dB / octave, in such case indeed on a frequency one octave below Fs you will need 16 times more of power than nominally that means huge demand on extra excursion possibilities without unacceptable amount of distortions.

Read what Bob Cordell wrote about that.
I do not necessarily agree with Bob Cordell, but he's an authority on a number of audio related subjects. That being the "EBS" alignment. NOT what I am talking about.

Fs != F3 in 99.99% of all possible configurations.
Oh, going below Fs by -3dB also != F3.

Quote
Appearance of well damped box as being larger does not mean increase in it's size. It "appears" in terms of lesser raise of a resonant frequency, but as soon as a damping material absorbs an energy Q goes down. If somebody used fingers to show you how to count 2 apples plus 2 apples it does not mean that fingers has a smell and taste like apples, right, though it appears as if you counted apples counting fingers?

Friend, I have no idea what you are trying to say here.

You can make a cabinet be damped WRT resonances and transmission of audio energy.
You can try to make the internal volume of a cabinet be absorptive.

So far there is no material that I know of that is a) very effective at LF vs. physical thickness and/or b) absorptive equally at HF vs. LF (the problem being that most materials are not particularly absorptive at LF.

The fact that "memory foam" appears to not spring back quickly does not automatically mean that it is either effective at not transmitting LF energy or absorbing LF energy (the other side of the same coin) - meaning that it is good at turning sonic vibrations into heat.

Long hair natural wool is regarded as one of the best in this regard, and it is not very good - at BEST it adds an effective 10% to the volume, which is the flip side of lowering the Fb of the system, eh?

Put this even more directly, if "memory foam" was as good as you seem to think, then it would be possible (based on its fantastic LF absorbtion) to build speaker systems that are much much smaller than what are required today and have the same LF response as a much larger cabinet built as is commonly done. Thus, all the myriad of companies, with engineers and Phds would all be made fools at once, if this were so. Now, such a thing could happen - but I doubt that this is going to be such a case.

Quote
Memory foam is very different from what you assume: it absorbs acoustic energies on very wide frequency band, including fractions of Hertz. How long a memory foam mattress "remembers" your position when you stand up from your bed?

Indeed, it has specific mechanical properties due to the way it is made.
However, it is still the same compound as "regular" foam, the difference is in the way the "foam" part is handled during manufacture. If it absorbs LF audio differently that has yet to be established (afaik) in any literature. It would be pretty easy to do some simple "lab" tests to establish the difference.

Quote
Watching my language I may say that... hmmm... what you write is... hmmm.... Bearcandy?  Grin

I guess the use of such language is up to the moderators - but I don't like it when you use it to characterize my posts.

Quote
Now, back to that Big Box and R-390.
The problem may have nothing to do with Fs, F3, and the rest of bearcandies. Results of intermodulations of radio waves on AM detector have many frequencies, from infrasounds to high pitch whistles. So  filtering out everything around frequency band that is enough for speech recognition is a good practice, so indeed some HPF and LPF are desired, but not because of that bearcandies you wrote about.  Smiley

Dude, he wrote that he was getting over excursion at extreme LF.
Did you read that?
Apparently not.

10-4 gud buddy.

          _-_-
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WBear2GCR
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« Reply #112 on: May 16, 2008, 03:42:50 PM »

.
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KA1ZGC
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« Reply #113 on: May 16, 2008, 03:46:10 PM »

Just a suggestion, here...

Since you guys are talking very directly to one another about a topic that doesn't seem to be drawing in any other protagonists, and you're not discussion capacitors per se, perhaps you two lovebirds should carry this on via email?

Just my $0.02.

--Thom
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W1EUJ
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« Reply #114 on: May 16, 2008, 04:50:02 PM »

This thread is the King of the Dead Horses. All hail our corpse-horse masters!
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WBear2GCR
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« Reply #115 on: May 16, 2008, 05:20:55 PM »

odd that you'd say that Dave, since it is apparently the 5th most read thread in the Technical Forum?

         _-_-Wily Bear 2 Golden Chicken Roosts
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« Reply #116 on: May 16, 2008, 06:54:44 PM »

Suspect most are 'rubbernecking' the 'train wreck' in progress... Wink
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WBear2GCR
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« Reply #117 on: May 16, 2008, 07:15:39 PM »

Steam or Diesel?

Passenger or Freight?

Domestic, Euro, India??  Roll Eyes

             Grin           _-_-bear
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wavebourn
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« Reply #118 on: May 16, 2008, 07:50:35 PM »


Put this even more directly, if "memory foam" was as good as you seem to think, then it would be possible (based on its fantastic LF absorbtion) to build speaker systems that are much much smaller than what are required today and have the same LF response as a much larger cabinet built as is commonly done.


Here you go:



This studio monitors are built of a solid concrete (I don't have such composites as Harman has) with linoleum and memory foam inside.
Unfortunately, in order "have the same LF response as a much larger cabinet built as is commonly done." bigger area of cones is needed, or other means to match acoustic impedances like horns, while damping materials help to control resonances only, unlike in your virtual reality made of phrases taken without understanding of their meanings from popular literature.

odd that you'd say that Dave, since it is apparently the 5th most read thread in the Technical Forum?

Did you try to read an Elementary Physics schoolbook instead?  Wink

I am not going to comment what you wrote: anyway you'll complain to Moderator asking to remove my comments.

Good luck!  Grin

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WBear2GCR
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« Reply #119 on: May 16, 2008, 09:01:13 PM »

Wavy,

This is the AMfone forum.

I suggest that since you are a participant on DiyAudio.com, as I am, that you put your designs and physics up on that forum, and see if it flies or not. Forget about what I think or can't think of, ok?

Let's talk about radio, ham radio, and AM here.

People other than myself started this thread about caps, and their audibility, etc...
I have only tried to bring some information to light.

There is no need for me to comment on your good looking boxes... if you want my comments, then PM me with a link to your post on this topic or any topic like it on DIYaudio, alright then?

Good.

I'll try to avoid any further comments on topics that are OT in this thread.

       Cheesy

                     WBear2GCR
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wavebourn
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« Reply #120 on: May 17, 2008, 01:09:29 AM »

Bear;
it does not matter: AM it, FM, RF, Audiofile, what else, but absorbing energy from speakers you can't increase loudness. Never. It is the law of physics.
"Oh you researchers of perpetual motion, how many harebrained ideas have you created in this search. You may as well join the gold-makers." (C) Leonardo da Vinci
More information: http://www.hp-gramatke.net/perpetuum/english/page0060.htm

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ka3zlr
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« Reply #121 on: May 17, 2008, 09:37:24 AM »

Welp, I guess it's Safe to say then: That:...ah, better cabinetry design criteria are perpetually better with the square of the released volume of pressure..sound quality is correspondingly increased with the stability of the vibrating membrane..absorption factor isn't desired only for spills, leaks and wipes.  Grin

Now as to the crappacitor issue...? Cool
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wavebourn
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« Reply #122 on: May 17, 2008, 01:53:47 PM »

Welp, I guess it's Safe to say then: That:...ah, better cabinetry design criteria are perpetually better with the square of the released volume of pressure..sound quality is correspondingly increased with the stability of the vibrating membrane..absorption factor isn't desired only for spills, leaks and wipes.  Grin
Translation: below main resonant frequency speakers drop 12 dB/Oct, like 2'nd order filters. On resonant frequency they excibit a peak (boom, really) that is the louder the higher is Q of resonating system. When you put a speaker into an enclosure stiffness of an air causes increase of a frequency of that main resonance, so the smaller is the box, the higher is the main resonance frequency is shifted up (i.e. from the higher frequency the speaker will start to roll off). So, in order to cover lower frequencies we need speakers with lower resonant frequencies in bigger boxes. The lower is the self resonant frequency of the speaker, the smaller the box we can afford.
Now, in order to divide flies and meatballs, let's talk about the main resonance: to avoid a "boomy" sound we need to lower Q of the resonating system. Whe know how to make Q less: to add something that will turn an energy of resonating system to heat: resistor in radio, or damping material in speaker boxes. If to "underdamp" sound will be boomy; if to "overdamp" bass will be rolled of.

No black magic at all!

Quote
Now as to the crappacitor issue...? Cool

It was discussed already: electric field repel and attract plates of capacitors even in an air. Change in distances change capacitances (remember Teremin, capacitive alarm detector?). Acoustical resonances happen in capacitors.
Properties of dielectrics also depend on strength of electric field. It means, capacitors are not linear, and non-linearity is frequency depended and phase shifted. Their capacitances and  losses depend on applied voltages and frequencies. If they are not linear, they distort signals, it is the axiom.
The question is, which capacitors, in which conditions, give less distortions. The answer can't be simple...

Rod Eliott has some useful information on his site: http://sound.westhost.com/articles/capacitors.htm
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WBear2GCR
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« Reply #123 on: May 17, 2008, 02:10:46 PM »

Bear;
it does not matter: AM it, FM, RF, Audiofile, what else, but absorbing energy from speakers you can't increase loudness. Never. It is the law of physics.
"Oh you researchers of perpetual motion, how many harebrained ideas have you created in this search. You may as well join the gold-makers." (C) Leonardo da Vinci
More information: http://www.hp-gramatke.net/perpetuum/english/page0060.htm

Don't recall saying anything about absorbing energy from speakers increasing loudness...  Roll Eyes Roll Eyes ??

Please do not either put words in my mouth, or misquote.
If I said that, please cite it as a quote.

But WRT perpetual motion, might not the laws of physics only apply locally?
Do they work properly in a black hole?
Do they work properly at or beyond the event horizon?
And, might not the universe as a whole turn out to be a perpetual motion machine?

Never mind...

       _-_-
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ka3zlr
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« Reply #124 on: May 17, 2008, 03:48:57 PM »

What happened, somebody go get married while i was gone...Grin....Wavy where's your sense of Humor Babe...My main interests have always been in construction practice in UHF to microwave regions..Cavity, Plane and Length Resonance are the issues in that realm... Cheesy Filters are a plumbers delight... Cool

Calculate your opening aperture of the cavity for the desired bass response required Brother...an Let that air out OM... Cheesy

Of course that's Old School thinken... I R an Old Guy Now... Grin


ya know, there's just to much drama in this world.....an Not Enough Humor...




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