June 18th, 2012, 11:16 PM
I found a speaker cabinet for sale. Turns out it has a Sears Roebuck label on it, part # 257-14253200. Number doesn't mean anything to Google.
There are 4 12" speakers. The code 138-29 is ink stamped on the magnet. The code W12016 is printed on the back of the paper cone.
I didn't pick them up yet because I was concerned that the W12016 might stand for something like woofer, 12 inch 16 Ohms.
Anybody have the knowledge on how to check them for impedance?
June 18th, 2012, 11:32 PM
Are these old hi-fi speakers? Sometimes they can work OK for lower powered musical instrument use, but usually they can't handle it.
Send us a pic, maybe they are good...
As far as determining impedance, a quick and easy way to get an idea is to measure the DC resistance with an inexpensive ohm meter, which usually reads a little lower than the actual impedance (a dc measurement of about 6 ohms will indicate a likely 8-ohm speaker).
June 19th, 2012, 03:06 PM
What kind of cabinet were they in?
Like Bob said, the issues are power handling and frequency range.
Guitar speakers are strongly mid range present and rapidly roll off below about 50-80 hz and above 4-6k hz.
So if they are HiFi type speakers they may not be able to handle the power output from an amp, or their wider frequency response range may lead to an unpleasant overall sound.
You can measure dc resistance across the speaker for a rough approximation of impedance, but that is more about not misloading your amp than protecting the speakers. Beyond that you can give them a try and will probably be safe if you either stick to a small (ie. less than 15 watt) amp and/or keep the volume down.
June 19th, 2012, 03:54 PM
It is definitely a bottom speaker cabinet, albeit a rather cheap one. 3' x 2' x 1' with a 1/4" input jack. Typical guitar box construction.
I was looking at these for the purpose of experimenting with the 5F1 at first and possibly a 5F2A, 5E3, or 5F10 down the road. I have a feeling that 5F10 is going to be the next hot thing around here.
My main concern when seeing them was the impedance rating.
Overall, they don't appear to be any wimpier than the speakers I've seen in pictures of old vintage amps.
Like you say the speakers aren't nearly as much concern as ruining an amp, especially my first build-to-be.