The blurb technical said 300W RMS handling for this 12 inch speaker.
Now it is blown and I've opened up
2 layers of 90 turns , so 180 turns of .16mm or 6.3 mil/thou diameter wire
on 64 mm diameter former.
300 Watt ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N Cook wrote:
The blurb technical said 300W RMS handling for this 12 inch speaker.
Now it is blown and I've opened up
2 layers of 90 turns , so 180 turns of .16mm or 6.3 mil/thou diameter wire
on 64 mm diameter former.
300 Watt ?

What make and model speaker is it? what`s failed? is the voice coil
burnt? What was diving it when it blew? and what signal content?
Ron(UK)

N Cook wrote:

The blurb technical said 300W RMS handling for this 12 inch speaker.

RMS continuous ? What model.


Now it is blown and I've opened up
2 layers of 90 turns , so 180 turns of .16mm or 6.3 mil/thou diameter wire
on 64 mm diameter former.
300 Watt ?

The temperature rating of the former ( and the glue ) is the relevant issue. Not
to mention ventilation too !

Some ppl push 2-1/2 inch formers to 300W - personally I'm happier with 3".

Graham

N Cook wrote:
The blurb technical said 300W RMS handling for this 12 inch speaker.
Now it is blown and I've opened up
2 layers of 90 turns , so 180 turns of .16mm or 6.3 mil/thou diameter wire
on 64 mm diameter former.
300 Watt ?


The field strength of the magnet assembly has a lot to do with the power
handling, also the cooling arrangements and the cabinet design.

Ron(UK)

N Cook wrote:

The blurb technical said 300W RMS handling for this 12 inch speaker.
Now it is blown and I've opened up
2 layers of 90 turns , so 180 turns of .16mm or 6.3 mil/thou diameter wire
on 64 mm diameter former.
300 Watt ?

Who knows? There are so many design factors that come into play. Let
alone what the manufacturer meant by "300W RMS handling" - Peak RMS? If
so, for how long? Continuous RMS? 300W at what frequency?

Rick

"Rick" wrote in message ...
N Cook wrote:

The blurb technical said 300W RMS handling for this 12 inch speaker.
Now it is blown and I've opened up
2 layers of 90 turns , so 180 turns of .16mm or 6.3 mil/thou diameter
wire
on 64 mm diameter former.
300 Watt ?

Who knows? There are so many design factors that come into play. Let
alone what the manufacturer meant by "300W RMS handling" - Peak RMS? If
so, for how long? Continuous RMS? 300W at what frequency?

Rick

What is " peak " RMS ? That is an oxymoron ...

Arfa

N Cook wrote in message
...
The blurb technical said 300W RMS handling for this 12 inch speaker.
Now it is blown and I've opened up
2 layers of 90 turns , so 180 turns of .16mm or 6.3 mil/thou diameter wire
on 64 mm diameter former.
300 Watt ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



My trusty 1941 Electrical Engineer's Companion has the following data
Resistivity for 0.0063 inch diameter wire 0.76 ohm per yard
Safe current carying capacity of the smallest gauge listed of 0.044 inches
diameter of 5 amps in air.
No reason to suspect this data.

This voice coil of 180 turns on 64 mm
gives 1425 inches = 40 yards
so resistance 30 ohms

Scaling by areas, current carying capacity is reduced by ratio of squares of
44 to 6.3 giving about 0.1 amp, only, in free air
I*I*R = 0.3 Watt

Where is my error ?

N Cook wrote:

N Cook wrote in message
...
The blurb technical said 300W RMS handling for this 12 inch speaker.
Now it is blown and I've opened up
2 layers of 90 turns , so 180 turns of .16mm or 6.3 mil/thou diameter wire
on 64 mm diameter former.
300 Watt ?

My trusty 1941 Electrical Engineer's Companion has the following data
Resistivity for 0.0063 inch diameter wire 0.76 ohm per yard


That would be AWG34 wire, much too small for a speaker like this. How
did you measure the wire, and did you slip a decimal place?

How many turns per inch?


Safe current carying capacity of the smallest gauge listed of 0.044 inches
diameter of 5 amps in air.
No reason to suspect this data.


Here is a basic AWG wire chart. I have to add a the other columns for
transformer and coil winding.

http://home.earthlink.net/~mike.terrell/RefAWG.html


This voice coil of 180 turns on 64 mm
gives 1425 inches = 40 yards
so resistance 30 ohms

Scaling by areas, current carying capacity is reduced by ratio of squares of
44 to 6.3 giving about 0.1 amp, only, in free air

It isn't in free air, its a wound inductor, and 6.3 mil wire is rated
at .057 amps at 700 circular mils per amp. This is a common value for
continuous duty coils and transformers.


I*I*R = 0.3 Watt

Where is my error ?


What is the rated impedance of the speaker?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Surely if confined on a coil then lower current handling?

8 ohms

N Cook wrote:

Surely if confined on a coil then lower current handling?

8 ohms


That 700 circular mils per amp is for transformer/coil calculations.
6.125 amps * 8 ohms = 49 volts * 6.125 =300.125 watts. This would
require a 14 AWG wire for 700 circular mils per amp. which is ten times
the diameter you quoted. It is 63 mils, or about 15 turns per inch.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Michael A. Terrell wrote in message
...
N Cook wrote:

Surely if confined on a coil then lower current handling?

8 ohms


That 700 circular mils per amp is for transformer/coil calculations.
6.125 amps * 8 ohms = 49 volts * 6.125 =300.125 watts. This would
require a 14 AWG wire for 700 circular mils per amp. which is ten times
the diameter you quoted. It is 63 mils, or about 15 turns per inch.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

It is 90 turns in 15 mm , 2 layers, 1 over the other, so 180 turns