PMC EB1i impedance curve

[jbaudio68]

Originally Posted by jdandy

Here is an impedance and phase curve chart that was publish in HiFi Crtitic for the IB2i. Sorry, but it wasn't any clearer in the web page.

http://www.hificritic.com/downloads/...IC_PMCIB2i.pdf

Dan, I had missed this article. Thanks so much or posting. If the EB1 follows the IB2 it would explain why Jerome's speakers (and my mono-blocked 275s) might sound better using the 8 ohm taps. I know there are autoformers but I thought the IB2 was a 4 ohm speaker.

[jdandy]

Originally Posted by jbaudio68

Dan, I had missed this article. Thanks so much or posting. If the EB1 follows the IB2 it would explain why Jerome's speakers (and my mono-blocked 275s) might sound better using the 8 ohm taps. I know there are autoformers but I thought the IB2 was a 4 ohm speaker.

Jeremy.......Looking at the chart, it appears the impedance begins to climb above 4 ohms below 70Hz, peaking at 17 ohms at 40Hz, dropping to 8 ohms at 30Hz, then peaking again to 16 ohms at 21Hz. The impedance stays between 3.5 ohms to 10 ohms across the remainder of the frequency band. That is essentially a stable impedance, and would work quite well on 4 ohm or 8 ohm taps. Again, it is impressive that the phase curve follows the impedance. PMC crossovers are very well designed.

[PHC1]

And then there are Peak Consult speakers. Let me know if you find anything more stable.

[jbaudio68]

Originally Posted by jdandy

Jeremy.......Looking at the chart, it appears the impedance begins to climb above 4 ohms below 70Hz, peaking at 17 ohms at 40Hz, dropping to 8 ohms at 30Hz, then peaking again to 16 ohms at 21Hz. The impedance stays between 3.5 ohms to 10 ohms across the remainder of the frequency band. That is essentially a stable impedance, and would work quite well on 4 ohm or 8 ohm taps. Again, it is impressive that the phase curve follows the impedance. PMC crossovers are very well designed.

Dan, would you mind explaining why phase should follow impedance? I can say that going to the 8 ohm taps created a deeper sound stage and seems to have improved the bass. Maybe somehow it is allowing more current? If so, then going solid state should be amazing...(with a tube pre). What I do know is that my IB2S amaze me on a regular basis. Somehow I stumbled onto a great brand.

[jdandy]

Jeremy.......Wikipedia explains it better than I could.

Impedance variations of the load with frequency translate into variation in the phase relationship between the amplifier's voltage and current outputs. For a resistive load, usually (but not always) the voltage across the amplifier's output devices is maximum when the load current is minimum (and the voltage is minimum across the load) and vice-versa, and as a result the power dissipation in those devices is least. But due to the complex and variable nature of the driver/crossover load and its effect on the phase relationship between the voltage and current, the current will not necessarily be at its minimum when the voltage across the output devices is maximum - this results in increased power dissipation in the amplifier output stage which manifests as heating in the output devices. The phase angle varies most near resonance in moving coil loudspeakers. If this point is not taken into consideration during the amplifier design, the amplifier may overheat causing it to shut down, or cause failure of the output devices.

Here's the link to the entire artical on electrical characteristics of dynamic loudspeakers: Electrical characteristics of dynamic loudspeakers - Wikipedia, the free encyclopedia

[Jerome W]

Dan,
At least in the bass, this does not look as a stable impedance to me but more like the valleys and mountains of the Alps where we had our last vacations.

[tdelahanty]

You guys have stumbled upon the realities of speaker design. Impedance specs are usually nominal, an average. It is a mathmatical repesentation. Two things are important considerations; 1) impedance generally is lowest at low frequencies and, if too low, can suck up a huge portion of your amp's power. 2) as frequency gets higher impedance increases thus making it more difficult for your amp to drive higher frequencies. to rated output.

[Face]

Originally Posted by PHC1

And then there are Peak Consult speakers. Let me know if you find anything more stable.

That is impressive.

[DaveNote]

Originally Posted by ian@pmc

I tried getting to Stereophile for review the EB1i. They instead chose the DB1i.

I wouldn't hold your breath for an impedance curve.

Ian, I'm not surprised about Stereophile not reviewing the larger PMC speakers. I remember reading some years ago somewhere that John Atkinson doesn't much care for transmission line designs. I've also heard that PMC has been criticized about the published measurements of their speakers. I've owned IB2s, MB2s and now MB2is - and frankly I don't much care how they are designed or their measurements. I simply like the way they sound.

[jbaudio68]

Originally Posted by jdandy

Jeremy.......Looking at the chart, it appears the impedance begins to climb above 4 ohms below 70Hz, peaking at 17 ohms at 40Hz, dropping to 8 ohms at 30Hz, then peaking again to 16 ohms at 21Hz. The impedance stays between 3.5 ohms to 10 ohms across the remainder of the frequency band. That is essentially a stable impedance, and would work quite well on 4 ohm or 8 ohm taps. Again, it is impressive that the phase curve follows the impedance. PMC crossovers are very well designed.

Dan, as an owner of PMC EB1i speakers (the closest speaker I know to the IB2) and both the 601 and 2301 amps, which amp one would you choose if you could only have one system (and why?)? I ask because I am getting closer to making a purchase of a 2300 and either the 601 or the 2301 to drive my IB2S speakers. Thanks for your input.