If speaker impedance wasn't complete... what are we missing?

[rayma]

Power = current x voltage x Cos(phase angle between the 2)

The last factor is 1 if the load is purely resistive, otherwise the cos() is less than 1.

dave

Check the paper, info first published in the 80s. Not talking about single frequency sine waves.

 

[planet10]

I read that paper when it was fresh off the presses.

dave

 

[rayma]

Yup, also a similar article was published in Audio Magazine in the 80s.
Shows that even repetitive waveforms (with certain shapes) can produce
large current transients from the amplifier due to energy storage in the crossover.

 

[planet10]

One of the reasons i tend to avoid (speaker level) crossovers.

dave

 

[AllenB]

Yes, but that's what a crossover is for.. to direct what is needed from the amplifier. We may not only configure it to attenuate but even to take more than it otherwise would. It is all accounted for in the impedance which will be low if we ask more from the amp.

 

[thirdicomplex]

PS - I always thought the issue with Infinity was that they just didn't have the tools. If memory serves, computer spreadsheets (Lotus 1 2 3) had just become popularized, and being able to simultaneously tune for fr and impedance was very hard to do.

Now in the modern times I've seen Focal introduce impedance LOWERING circuits which apparently only exist to create a < 4 Ohm impedance in the bass.

Here's a snippet from a conversation between Bill Watkins and somebody else:

"Now I set the parameters of the original QLS-1 in a
prototype and shipped it to Infinity. It had a minimum
impedance of 3.2 ohms, acceptable for a 4 ohm speaker.
At that time we were operating a retail store selling
Infinity. Our first shipment of the QLS-1's arrived,
we tested a pair and found the impedance to be
~1 3/4 ohms from ~50 - 80 HZ. Now, the fun begins...
Mr. Nudell wanted a spec down to 20 HZ, he got to
18, as I recall, by adding ~35 grams of mass under
the dust cap, BUT he did not re-tune LC to the
lower resonant frequency, leaving vc-2 operating
somewhat above the new fundamental resonance, and
creating a low impedance in that area. My name
was already on the royalty agreement, which had no
stipulation to cover such... I did voice my
disapproval to no avail."


Infinity also used Lpad's in many of their speakers but didn't connect the "ground" pin. I've measured some low dips in the mid/treble depending on the level position on a pair of Kappa 7.1's and RS5B's. Frankly, my dear I don't think Arnie gave a damn

 

[eriksquires]

One of the reasons i tend to avoid (speaker level) crossovers.

dave

Coward.




All in good fun, I am doing my first active speaker and I can 100% see the advantages.