The shite wot is writ here...
 

"Don Pearce" wrote in message
...
On Tue, 26 Sep 2006 18:49:48 +0100, Eiron wrote:

Don Pearce wrote:

As for the tones and what you hear. 14.5kHz would be about right for
chaps our age - and it does make the top octave a bit academic. It is
only reached a couple of seconds from the end of the sweep because the
sweep is log - equal time per octave. Now, for the low end stuff, what
you are hearing from the 20Hz is certainly second or third harmonics;
they can sound surprisingly like the real thing. The drivers may claim
30Hz (Fs= 36Hz), but in those cabinets they will be falling very
steeply below about 60Hz.

Test tones below 30Hz at even modest levels can make you feel rather sick
in less than the time it takes to tune a reflex port.

Well, if it was a truly tuned port (or rather a line) it would be at
36Hz to match the speaker's resonance, but the dimensions say it is
somewhat above that (it needs about fifteen feet for half wave at
36Hz), so I don't really understand how it is meant to work. Add to
that the fact that the line is tapered, so it is providing some gain
to the back wave, rather than the loss which would make much more
sense, and it is all a bit mysterious.


It is indeed - I am almost (but not quite) on the threshold of beginning to
start to get the earliest hint of a sign of an inkling about all this....

;-)

The shite wot is writ here...
 

Don Pearce wrote:

On Tue, 26 Sep 2006 18:39:17 +0100, Eeyorewrote:
Don Pearce wrote:

Back on the air - my ISP has had busted Usenet for a couple of days.

How did they do that *this time*. Talk about them being a careless bunch or what !

Graham

They had a busted hard drive in their RAID and it took them that long
to diagnose it. The mind boggles.

Astonishing !

Graham

The shite wot is writ here...
 

On Tue, 26 Sep 2006 19:53:59 +0100, "Keith G"
wrote:


"Don Pearce" wrote in message
...
On Tue, 26 Sep 2006 18:49:48 +0100, Eiron wrote:

Don Pearce wrote:

As for the tones and what you hear. 14.5kHz would be about right for
chaps our age - and it does make the top octave a bit academic. It is
only reached a couple of seconds from the end of the sweep because the
sweep is log - equal time per octave. Now, for the low end stuff, what
you are hearing from the 20Hz is certainly second or third harmonics;
they can sound surprisingly like the real thing. The drivers may claim
30Hz (Fs= 36Hz), but in those cabinets they will be falling very
steeply below about 60Hz.

Test tones below 30Hz at even modest levels can make you feel rather sick
in less than the time it takes to tune a reflex port.

Well, if it was a truly tuned port (or rather a line) it would be at
36Hz to match the speaker's resonance, but the dimensions say it is
somewhat above that (it needs about fifteen feet for half wave at
36Hz), so I don't really understand how it is meant to work. Add to
that the fact that the line is tapered, so it is providing some gain
to the back wave, rather than the loss which would make much more
sense, and it is all a bit mysterious.


It is indeed - I am almost (but not quite) on the threshold of beginning to
start to get the earliest hint of a sign of an inkling about all this....

;-)


I know that feeling all too well.

How long do you reckon the horn bit of those speakers would be if you
straightened it out?

d

--
Pearce Consulting
http://www.pearce.uk.com

The shite wot is writ here...
 

"Don Pearce" wrote
How long do you reckon the horn [...] would be if you
straightened it out?

Ferfuxake, I don't wanna know the length of Keith's "horn".


M :-/
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.livejournal.com/userinfo.bml?user=fleetie

The shite wot is writ here...
 

On Tue, 26 Sep 2006 21:18:17 +0100, "Fleetie"
wrote:

"Don Pearce" wrote
How long do you reckon the horn [...] would be if you
straightened it out?

Ferfuxake, I don't wanna know the length of Keith's "horn".


M :-/

Just you keep your eyes closed while he goes behind the screen...

d

--
Pearce Consulting
http://www.pearce.uk.com

The shite wot is writ here...
 

"Don Pearce" wrote

Well, if it was a truly tuned port (or rather a line) it would be at
36Hz to match the speaker's resonance, but the dimensions say it is
somewhat above that (it needs about fifteen feet for half wave at
36Hz), so I don't really understand how it is meant to work. Add to
that the fact that the line is tapered, so it is providing some gain
to the back wave, rather than the loss which would make much more
sense, and it is all a bit mysterious.


It is indeed - I am almost (but not quite) on the threshold of beginning
to
start to get the earliest hint of a sign of an inkling about all this....

;-)


I know that feeling all too well.

How long do you reckon the horn bit of those speakers would be if you
straightened it out?


Gawd knows, probably not that long - the Jerichos are 3'10" high:

http://www.apah69.dsl.pipex.com/fost...fe206pic08.JPG

http://www.plasmatweeter.de/images/jericho/horn.gif


And the (In)Fidelios are 3'4" high:

http://www.apah69.dsl.pipex.com/infi...nfidelio02.jpg

http://www.lowtherloudspeakers.co.uk...gs/fiddwg.html


Your guess would be as good as mine! :-)

The shite wot is writ here...
 

"Don Pearce" wrote in message
...
On Tue, 26 Sep 2006 21:18:17 +0100, "Fleetie"
wrote:

"Don Pearce" wrote
How long do you reckon the horn [...] would be if you
straightened it out?

Ferfuxake, I don't wanna know the length of Keith's "horn".


M :-/

Just you keep your eyes closed while he goes behind the screen...



It's not that scary, I'm sorry to say.....

:-(

The shite wot is writ here...
 

Just you keep your eyes closed while he goes behind the screen...

And he puts on his dark glasses, and he shows you where to hit.
The cameras pan
The stand-in stunt man
DRESS REHEARSAL RAG
IT'S JUST A DRESS REHEARSAL RAG
YOU KNOW THIS DRESS REHEARSAL RAG


Sorry, I hate it when it does that.

The shite wot is writ here...
 

On Tue, 26 Sep 2006 21:44:24 +0100, "Keith G"
wrote:


"Don Pearce" wrote

Well, if it was a truly tuned port (or rather a line) it would be at
36Hz to match the speaker's resonance, but the dimensions say it is
somewhat above that (it needs about fifteen feet for half wave at
36Hz), so I don't really understand how it is meant to work. Add to
that the fact that the line is tapered, so it is providing some gain
to the back wave, rather than the loss which would make much more
sense, and it is all a bit mysterious.


It is indeed - I am almost (but not quite) on the threshold of beginning
to
start to get the earliest hint of a sign of an inkling about all this....

;-)


I know that feeling all too well.

How long do you reckon the horn bit of those speakers would be if you
straightened it out?


Gawd knows, probably not that long - the Jerichos are 3'10" high:

http://www.apah69.dsl.pipex.com/fost...fe206pic08.JPG

http://www.plasmatweeter.de/images/jericho/horn.gif


And the (In)Fidelios are 3'4" high:

http://www.apah69.dsl.pipex.com/infi...nfidelio02.jpg

http://www.lowtherloudspeakers.co.uk...gs/fiddwg.html


Your guess would be as good as mine! :-)


Eyeballing the pic of the Jericho, I reckon that's about seven feet of
line. That would put the tuning point at around 86Hz. You can expect
the output to drop pretty rapidly below that. The Fidelios will be
correspondingly higher.

The sums go like this: speed of sound (345m/sec) divided by the line
length in metres (2) divided by 2 again for half wave, which is what
you need for the back wave to reinforce the front radiation.

In a traditional transmission line speaker the line is filled with
absorber which does two things - it tames the resonance peak (which is
probably what sounds like good bass in these) and slows the sound
wave, making the line effectively longer.

There is a really useful paper on transmission lines speakers here
http://www.t-linespeakers.org/projec.../response.html
yours is sufficiently close to a transmission line that this stuff
will apply just fine. The effect of filling on the speed of sound is
the part of main interest.

d

--
Pearce Consulting
http://www.pearce.uk.com

The shite wot is writ here...
 

Don Pearce wrote:
On Tue, 26 Sep 2006 21:44:24 +0100, "Keith G"
wrote:

"Don Pearce" wrote

snip

There is a really useful paper on transmission lines speakers here
http://www.t-linespeakers.org/projec.../response.html
yours is sufficiently close to a transmission line that this stuff
will apply just fine. The effect of filling on the speed of sound is
the part of main interest.


Excellent site - thanks.

Rob