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-   -   Putting the Science Back into Loudspeakers (http://www.diyaudio.com/forums/multi-way/105136-putting-science-back-into-loudspeakers.html)

graaf 12th July 2007 07:43 AM

Putting the Science Back into Loudspeakers
 
Hello everybody!

since John Watkinson's "Celtic Audio" website is down and the essay "Putting the Science Back into Loudspeakers" is no longer available online I decided to attach it here at diyaudio.com
Because I think it is worth reading and I noticed that it was only discussed in neodymium/magnetic threads so far. And the question of neodymium is quite marginal in that essay by the Author of "The Art of Sound Reproduction"
fortunately the essay, "a thought provoking article" in the words of Siegfried Linkwitz, is short and the file is not too big to be attached here

best,
graaf

graaf 12th July 2007 07:45 AM

Re: Putting the Science Back into Loudspeakers
 
2 Attachment(s)
another try :)

OzMikeH 12th July 2007 10:00 AM

Thanks Graaf.
I think everyone should read this, It will provoke some interesting discussion and research.

Using variable bit rate encoding to evaluate speaker quality is brilliant... But only if people's ability or training to detect compression artifacts are equal. Still great for one person benchmarking their speakers.
I wonder how many of the highly rated headphones are popular only because they are good at masking compression artifacts.
Now to find some free software that can do that on-the-fly provided CD is actually "blameless" that is.

so rectangular reflex boxes = bad. Now how to define what a good box/baffle is.

phase_accurate 12th July 2007 11:12 AM

Celtic's Cabar is of course a speaker where all off John W's claims are taken into consideration. There are no sharp corners and it has a transient perfect crossover. The woofer "box" is of cylindrical shape and offers therefore more inherent stiffness than a conventional box.
Since their homepage is down for days already (anyone knows what happened ?) one has to look elsewhere to see the design. Fortunately it is on the front cover of one of John's books:

http://books.elsevier.com/bookscat/c...0240515120.jpg

It shows the right third of the speaker. The small wideband metal-cone driver is the mid-high. AFAIK is there another one on the backside as well. Together with the proprieatary signal processing an exactly predetermined radiation pattern is achieved.
There are only smooth shapes involved as one can see.
The metallic-looking "ring" is in fact the grille for the woofer which is hidden from sight and which is using the part of the tube to the left of the grill. The center section of the tube carries the electronics and the left part is the mirror-image of the part shown on the picture.

One that I know of that would also fulfil many of John W's claims:

http://www.pupazzo.page.ms/

Since both the Cabar and the Pupazzo have limited SAF in my case - I use a conventional box that is still better regarding transient reproduction than > 99.9 % of the speakers out there. And yes my mid-tweeter has a rare-earth magnet as well !

Regards

Charles

graaf 12th July 2007 11:22 AM

Quote:

Originally posted by OzMikeH
Thanks Graaf.
I think everyone should read this, It will provoke some interesting discussion and research.



You are very much welcome :)
I hope that it will provoke some interesting discussion

best,
graaf

graaf 12th July 2007 11:48 AM

Quote:

Originally posted by phase_accurate
Celtic's Cabar is of course a speaker where all off John W's claims are taken into consideration.

this is what was on closed website regarding Cabar:

Quote:

The design and shape of the Cabar enclosure has been determined by the requirements for minimum diffraction, the closest possible spacing between the HF and LF drivers and as a sufficiently rigid pressure vessel. The basic body of the cabinet is an aluminium pipe, 150mm in diameter, divided into three sections. The centre section houses all the electronics for the fully active system: multiple power amplifiers, analogue signal processing, power supplies and connectronics. The two outer sections are the low frequency enclosure spaces, which extend out to the ends of the pipe. At each end of the pipe there are moulded high frequency enclosures, each housing two 50mm drivers. The overall length is 1.5metres. All the aluminium is anocoloured prior to a hard anodising finish, the other cabinet parts are epoxy painted.

The enclosure shapes are not just the whims of external design fancy, but combined with the transducer systems to produce an acoustic polar diagram that is a dipole at high frequencies and gradually shifts into an omni-directional pattern for the low frequencies. As a result oif carefully engineering, the polar diagram is very smooth and without any lobing: The reverberant sound field excited by a loudspeaker within a room is in effect the frequency response of the indirect emissions from the loudspeaker: If this indirect, or polar response is not clean and even, then the reverberation heard will be coloured and will add clutter to the overall imaging. A secondary benefit of a good polar response is the reduced requirement for acoustic treatment for the room: normal room reverberation in itself does not reduce the ability to listen accurately, so long as the reverberation is excited in a mimic of the natural trigger, in other words triggered by a smooth and even polar response.
the drivers were supposedly the Bandors

Quote:

Originally posted by phase_accurate

One that I know of that would also fulfil many of John W's claims:

http://www.pupazzo.page.ms/
it looks much like a crude DIY version of Beolab 5
with Manger Driver and kind of "Moultonian" acoustic lense

best,
graaf

CeramicMan 12th July 2007 11:57 AM

Awww... but I wanted to ask: what would be the best sounding carpet spikes for my speakers?

:clown:

Good stuff!

Perhaps one idea would be establish which ideas/concepts etc are decidedly UN-scientific?

graaf 12th July 2007 12:03 PM

Quote:

Originally posted by CeramicMan


Perhaps one idea would be establish which ideas/concepts etc are decidedly UN-scientific?

rectangular speaker boxes? bass reflex?

phase_accurate 12th July 2007 12:07 PM

Quote:

it looks much like a crude DIY version of Beolab 5
I think you are actually doing the constructor wrong. His design is older than B&O's space station. And it is omnidirectional, a thing that the B&O isn't.
And it is also transient-perfect another thing that the B&O isn't (which is quite a shame taken the B&O's massive built-in digital signal processing into account).

Regards

Charles

graaf 12th July 2007 12:12 PM

Quote:

Originally posted by phase_accurate


I think you are actually doing the constructor wrong. His design is older than B&O's space station. And it is omnidirectional, a thing that the B&O isn't.
And it is also transient-perfect another thing that the B&O isn't (which is quite a shame taken the B&O's massive built-in digital signal processing into account).


well, it looks like, that is all I have said :)
and it does look very, very crude

I don't know much about Beolab 5
I'm only interested in some ideas behind this commercial speaker


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