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Funny, the physical laws of reflection, refraction, scattering, diffraction, etc, are similar for sound waves and light waves, but the resemblance does not stop there. Listening to various car loudspeakers, I found the minimal diameter for an acceptable sound is 70mm, and that's also the smallest diameter for a satisfactory telescope in my view. 80mm grant a little more resolution in both, and 80mm is a very popular diameter in compact scopes or compact radios, at least the older ones.

They make 90mm scopes to get some extra oomph, and the 90mm loudspeaker begins to issue more discernible bass, so much so I keep one from an old radio my father bought in the 70's, not knowing what I'll do with it but the bass, checked that when plugged to a guitar amp, is noticeable enough despite the size. Then the standard louspeaker size in non-toy stereos is 100mm, and the standard refractor size to get good resolution and power is also 100mm. There must be a reason if so many observers buy that many expensive 4-inch apos, but not nearly as many buy tighter apertures for comparable sums.

Following the same progression, monitors in studios have 125mm to 130mm loudspeakers (that need to be complemented by a tweeter because the similarity cannot be total between light and sound), and these diameters are also the ones that provide deeper resolution on planets. 150mm approaches real power in telescopes, and 150mm is also the entry-level size for a guitar amp, like my 15 watt Fender Frontman, which does not lack bass despite its handbag format (WonderWoman's kinda big and heavy handbag).

200mm is quite enough for most observers, resolution-wise and power-wise, which happens to match the size of more serious amps. I have a modded Stagg 20w 200mm guitar amp and an Ampeg 20w 200mm bass amp, both are plenty large enough to deliver a full sound in their range. There is a reason if so many 8-inch Schmidt-Cassegrains and newtonians are in use everywhere!

Then the 10-inch scopes are heavier, but not unbearably so, and the 10-inch loudspeakers also deliver the near-maximal power and resolution for an amp that remains not hard to carry around. 12-inch scopes deliver enough light and detail to satisfy most everyone; again, the equivalent 12-inch size amps give out enough frequency range and raw power to please the vast majority of players. Size and weight become an issue in both cases, but not enormously so.

And lastly, the ultra-large 15" amps or 15" to 16" scopes start another league in power and resolution but they both become equally difficult to transport.

Not quite apples and oranges in my opinion, does it seem like a coincidence to you?

Edited by Ben the Ignorant
typo

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and heres me thinking you was on about surfing:icon_biggrin:, have tryed bose I have some 50mm speakers, the sound is mindblowing. charl.

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Yes, and that is the diameter of the standard astro binocular; even some 40mm latest-tech speakers pump out some very decent sounds when there is no room for larger ones, and this is also the format of some fine performers in binocular lenses. The trend seems to be confirmed if it is not a chance resemblance.

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But diameter and comparing to aperture is not everything.

A lot depends on the quality of the components used. No point having loads of diameter size with sub standard components or workmanship.

If you take telescopes a good little one will best a poor larger aperture one especially on the likes of planetary

Size is not everything, but quality of components and craftsmanship can be ☺

 

 

 

 

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14 hours ago, Ben the Ignorant said:

Not quite apples and oranges in my opinion, does it seem like a coincidence to you?

I smell a conspiracy, somewhere. :wink:

Nice comparison, though.

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A fun comparison, food for thought. I guess this only makes sense on earth where we have an atmosphere. If we were to go into space suddenly the smaller scope starts to do amazing things and the speaker......won't be heard at all!

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What a coincidence ??!! 

Maybe you just now discovered the unifying theory of everything factor? 

 

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2 hours ago, MarsG76 said:

What a coincidence ??!! 

Maybe you just now discovered the unifying theory of everything factor? 

 

No, the unifying theory of everything is a formula I read somewhere: "95% of everything is junk!". :evil4:

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5 minutes ago, Ben the Ignorant said:

No, the unifying theory of everything is a formula I read somewhere: "95% of everything is junk!". :evil4:

I believe that.. I watch free to air news... 95% is garbage

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Yet you don't see professional musicians using speakers with 10m diameters..!

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The optimum aperture size  and speaker size is 42. Obviously.

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I would not want to be close to this one at full blast http://alex-audio.com/en/prod/world-biggest-speaker/ . At 350 kg each (+ substantial enclosure?), not very portable, particularly if you want a stereo pair.

EDIT: just found this one https://productforums.google.com/forum/#!topic/gec-huge-unique/6X9sQNzijbY . It looks as though it would take a 2" eyepiece, but needs some serious glass at the objective end :headbang:

Geoff

Edited by Geoff Lister
  • Haha 1

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I only have a 2" speakers on my sound system. I sit in my listening room and the sound is amazing!

IMG_7114.JPG

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I think the original analogy is a valid one, a two inch speaker can produce low bass just as good as a twelve drive inch unit perhaps better (it is stiffer and lighter) but not at the same sound levels. Equally a two inch lens can will give better results than an eight inch because its easier to make a top quality small one but again it cant compete on the "volume or level" it transmits.

Alan

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47 minutes ago, Stu said:

I only have a 2" speakers on my sound system. I sit in my listening room and the sound is amazing!

IMG_7114.JPG

I believe that this is the actual antenna that was instrumental in the discovery of cosmic background radiation, aka the aftermath of the big bang.

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1 hour ago, Alien 13 said:

I would love to see the scope that this camera fits onto for afocal use :icon_biggrin:

world_s_largest_camera__chicago__illinois.thumb.jpg.168fe9b9b2c77aeeba3b2d613a4fd826.jpg

Alan

king_214.jpg

How about this one?

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2 hours ago, Geoff Lister said:

I would not want to be close to this one at full blast http://alex-audio.com/en/prod/world-biggest-speaker/ . At 350 kg each (+ substantial enclosure?), not very portable, particularly if you want a stereo pair.

I didn't know loudspeakers could be made that big, but they hit barriers like very large scopes do. That 80" vibrates only between 28Hz, not such deep bass for such a large membrane, and 2500Hz, very low under the 20.000Hz we can hear. Oversize (amateur) telescopes are underexploited in resolution because of turbulence, and oversize speakers are underexploited in frequency range. Makes me like my moderate telescopes and amplifiers even more.

I currently have two 10" amps, the most powerful is only a 40w; I used to play a Peavey Studio Pro 50, but it was really a 57w amp, and its 12" speaker moved so much air, never could play at a decent volume and distortion level without disturbing people. So I sold it to a friend's son after I saw he understood and respected the quality.

Speakers have to produce the waves when scopes can collect them passively, but in both cases great size causes more problems than I would deal with. I will obviously look into all oversize telescopes that I might find in a star party, but I don't think I'll ever buy one bigger than 16".

Edited by Ben the Ignorant

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10 minutes ago, wimvb said:

I believe that this is the actual antenna that was instrumental in the discovery of cosmic background radiation, aka the aftermath of the big bang.

I wondered why I was getting some hiss on it.... ;)

You are correct, yes it is.

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The speed of light in a vacuum has been defined fairly accurately. The speed of sound in a vacuum seems to present more of a challenge :icon_biggrin:

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