Determining power handling of a speaker ?

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)

RMS continuous ? What model.

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

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)

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

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 ?

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?

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

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.

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.

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.

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

On Fri, 12 Jan 2007 18:23:30 +0000, N Cook Has Frothed:

Most high power voice coils I've seen use flat wire. I would assume this adds to the watt rating.

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794

15 millimeters = 0.590551181 inches 1/.59055 * 90 = 152.400 turns per inch.

That would be AWG 34 (143 TPI) or 35 (158 TPI), or British SWG 38 or

1. I don't see how it could handle 300 watts at 8 ohms.

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

If it is square wire, multiply the current rating times 1.27

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

calculations.

time0

Exactly my problem , I cannot square the blurb statement with analysed physical reality.

It`s not a pure resistor, it`s an inductor, operating in a strong magnetic field, and theoretically with forced air cooling. Also, some manufacturers lie about their specs!

You still haven't disclosed what make and model of speaker it is.

Ron(UK)

I agree the aerodynamics of air forced through a narrow slot to produce cooling is going to be highly significant, I hadn't considered that. I need to find the current carying capacity of copper wire if allowed maximum foprced-air cooling. Then come back a bit from that as the covered layer is not cooled as efficiently as the outer layer.

I've been on Usenet long enough not to deliberately add material , not relevant to the thread, it will divert of its own course usually anyway.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I'm coming round to thinking that as these pots are easily openable and there is no wear at all on the tracks, then clean out all the lubricant with meths or something, coat the wiper with something to stiffen it up a bit and re-assemble, with no lubricant at all, maybe just "dry lubricant" of fine graphite powder laid in the track area instead.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

There ya go !!

Arfa

Oh for heaven's sake guys, it's *force cooled* !

Certain manufacturers have also demonstrated their voice coils operating red hot, the materials are that good.

Graham