[Fred DeRosa]

This is a diagram of my North American Sound monitor series loudspeaker. In
the literature, it is billed as a "transmission line" speaker.

http://panterragroup.home.mindspring...%20Speaker.pdf

Is this really a TL speaker? Of the TL designs I have seen, this has got to
be the simplist. It is 36" tall and with approximately 1ft^2 footprint.

Might as well show the actual literature.
http://panterragroup.home.mindspring...o/monitor1.jpg
http://panterragroup.home.mindspring...o/monitor2.jpg
http://panterragroup.home.mindspring...o/monitor3.jpg

[Don Pearce]

On Sat, 03 Mar 2007 18:18:13 GMT, "Fred DeRosa"
wrote:

This is a diagram of my North American Sound monitor series loudspeaker. In
the literature, it is billed as a "transmission line" speaker.

http://panterragroup.home.mindspring...%20Speaker.pdf

Is this really a TL speaker? Of the TL designs I have seen, this has got to
be the simplist. It is 36" tall and with approximately 1ft^2 footprint.

Might as well show the actual literature.
http://panterragroup.home.mindspring...o/monitor1.jpg
http://panterragroup.home.mindspring...o/monitor2.jpg
http://panterragroup.home.mindspring...o/monitor3.jpg


No, that isn't a transmission line, just a plain old vented enclosure.
The purpose of that baffle in the centre is unclear, unless it is
designed to provide some stiffness to the box.

d

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

[Fred DeRosa]

"Don Pearce" wrote in message
...
On Sat, 03 Mar 2007 18:18:13 GMT, "Fred DeRosa"
wrote:

This is a diagram of my North American Sound monitor series loudspeaker.
In
the literature, it is billed as a "transmission line" speaker.

http://panterragroup.home.mindspring...%20Speaker.pdf

Is this really a TL speaker? Of the TL designs I have seen, this has got
to
be the simplist. It is 36" tall and with approximately 1ft^2 footprint.

Might as well show the actual literature.
http://panterragroup.home.mindspring...o/monitor1.jpg
http://panterragroup.home.mindspring...o/monitor2.jpg
http://panterragroup.home.mindspring...o/monitor3.jpg


No, that isn't a transmission line, just a plain old vented enclosure.
The purpose of that baffle in the centre is unclear, unless it is
designed to provide some stiffness to the box.

d

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

Thanks Don,

In reading over my own literature that I posted I could not find where I got
"Transmission-Line." However it does describe the enclosre as "a unique
acoustically damped bass reflex system." Ok, it does look like that. I
suppose I was reading too fast as I read "phase-aligned" and "time-aligned."

fd

[Peter Larsen]

Don Pearce wrote:

This is a diagram of my North American Sound monitor series
loudspeaker. In the literature, it is billed as a "transmission
line" speaker.

There is no such thing, in modelling terms a transmission line
loudspeaker is a special case of the bass reflex design, ie. with almost
no volume and a very long port.

http://panterragroup.home.mindspring...%20Speaker.pdf

Is this really a TL speaker?

No. Transmission line designs aim for a port length some 1/8 to 1/4
wavelengths long, but designs are empiric - ie. one fiddles with the box
until it sounds right - and impedance measument reveals the standard
dual hump bass reflex curve, albeit with the lower hump much larger than
the upper, consistent with a small box tuned to a low frequency by and a
long port. Dick Pierce wrote something about this over in rec.audio.tech
some years ago, if what he wrote differs from my rendering of this, then
he is the one that is right.

Of the TL designs I have seen, this has got to be the simplest.

A real transmission line has an infinitely long port, ie. none, and a
gradually decreasing cross-sectional area from the end the loudspeaker
is in to the other end where the port with zero area is located. Such a
cabinet has the interesting property of adding the mass of the air in it
to the mass of the membrane so that the loudspeaker unit in the box
exhibits a lower main resonance than in open air. I have hear two
different implemenations of this, both sounded very good indeed.

No, that isn't a transmission line, just a plain old
vented enclosure. The purpose of that baffle in the centre
is unclear, unless it is designed to provide some stiffness
to the box.

It is a neat way to combine port wall with box bracing.

d

Regards

Peter Larsen