Results from the Impedance meter!

Mr. Sharpe

So I got a nice littler Impedance meter the other day with a nice big tool bag and thought i'd have fun with it and stick to my speakers.

Results:

Cerwin Vega U-103 Hed Design - 9.2 Ohms

DIY speakers - 7.1 Ohms

and the kicker! Yamaha NS-A 635A Monitor speakers - Rated for 8 Ohms, I got 6 Ohms!

Pretty sweet little instrument. Maybe I did something on the Yamaha's but I got 6 Ohms.

A thing about my DIY's, I touched the meter to the ends of the cables going into the receiver and it read 6 Ohms. That was pretty neat finding the actual impedance of the speakers.

I've always wanted one of these meters, I had fun:)

DaveHCYJ

Its always fun playing with new tools.

Side note: Doesn't the impedance change with the frequency on some speakers?

F1nut

DaveHCYJ wrote: »

Side note: Doesn't the impedance change with the frequency on ALL speakers?

Fixed and bingo!

Face

DaveHCYJ wrote: »

Its always fun playing with new tools.

Side note: Doesn't the impedance change with the frequency on some speakers?

99% of speakers.

Generally, a speaker with a DCR of 6ohms across the binding posts is an 8ohm speaker. In reality, you need a woofer tester to accurately test a speaker's impedance.

Inspector 24

Woofer tester?

Face

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=390-804

pyrocyborg

All speakers will dip way under their advertised impedance, expecially at lower frequencies. Take the LSi9/15 for example, they can go as low a 2 ohm, yet they are 4 ohm speakers.... but most of the time, yeah, they're over or at 4 ohm.

mhardy6647

F1nut wrote: »

Fixed and bingo!

well - in fairness... I do believe that most ribbon drivers (and perhaps some other types of planar drivers) behave as pretty much frequency-independent, purely resistive loads. Then again, a good old Quad electrostatic is pretty much a capacitor!

BUT, as someone considerably wiser (and perhaps even more sardonic) than I once said:

All generalizations are false, including this one

I suspect that the impedance meter in question measures impedance at a single, fixed AC frequency? Perhaps it does a frequency sweep, and measures and displays the minimum measured impedance? I dunno - can the OP provide a name/model number?

Here's a nice primer on impedance measurement (indeed, DIY Thiele-Small parameter measurement... even if you don't have a Woofer Tester!) and characteristics for a woofer.
http://sound.westhost.com/tsp.htm

This is a pretty typical frequency-dependent impedance curve for a woofer (annotated to explain various facets impacting impedance as a function of frequency) from the link above.

Mr. Sharpe

Hi, yeah the meter is a G2 Phoenix Pro: DL379. Yeah I've always known there were impedance curves in all speakers, I think when it starts curving is when the frequency gets wider. Fun stuff electricity yes?