Speaker impendance and bi amping

[IvoCRO]

Thank you all for your answers about this topic!

In the case of bi-amping passively using the bi-wire inputs on your speaker, you are dividing these curves into two pieces (which don't show up in the above measurements), one for the low-pass (woofers) and one for the high-pass (tweeters). For example, if you look at the impedance of the tweeter connection, you will see the effect of the crossover network's job to keep bass energy out of the tweeter. That means the crossover will raise the (magnitude of the) impedance at that input towards infinity (like an open circuit) at frequencies below the crossover frequency so that little lower-frequency energy flows to the tweeter. Then using your (magnitude of) Z equation in the woofer frequency range ( 1/Z(total)=1/Z(hi input) + 1/Z(lo input) ) where Zlo is getting to be infinity at lower frequencies and 1/Zlo then becomes zero and so 1/Z(total)=1/Z(hi input) + 0 or 1/Z(total)=1/Z(hi input) measured at the tweeter input. The same idea applies at in woofer input operating in the tweeter frequency range.

Well, this and other explanations gives answer to my question, and to my options which are two same amplifiers and without active crossover.

About speakers that I have: I might have an option to buy Canton Reference 8K in beginning of next year.

Here are few links with descriptions, reviews and measurements:

https://www.stereo.de/hifi-test/produkt/canton-reference-8k-1519 It is on german language, but google translate it pretty well

https://www.i-fidelity.net/testberichte/high-end/canton-reference-8-k/test.html detailed test which also can bi translated by google. Last two pages gives measurements

I hope that this long link will work:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwiGtYzD3P7lAhWYAxAIHTWzBxAQFjAAegQIARAC&url=https://stereo-magazine.com/archive/articles?tx_archive_pi1%5Baction%5D=download&tx_archive_pi1%5Barticle%5D=69335&tx_archive_pi1%5Bcontroller%5D=Archive&cHash=6a42e00695c649758f9061e413ea8075&usg=AOvVaw0yQTAPwHpsHeAeIBahIfMU

Right now I have smaller model, Reference 9 K with stands, for test at home, and they sound excellent.

 

[twiiii]

By convention a speaker system impedance used to be measured at the lowest reading just above the resonance of the woofer. Whats a convention. That when a bunch of the old boys sit around a table trying make a rule simple while drinking a case of beer or downing a few bottles of whiskey.
4 ohm speaker can be fairly linear if the speaker isn't ported or mounted in a horn and special attention is paid in designing the crossover. The woofer can be close to 4 ohms over its range and the mid can be 4 ohms as can be the tweeter. Its not usually the case but can be. So 4 ohm for the LF amp and 4 ohm for the HF. amp is totally possible. But not usual if the passive crossover has been totally removed. Altec, Bozak and JBL were famous for bi-amping. Bozak was easy all their drivers matched in impedance and sensitivity if the N-107 was used. Altec and JBL were a different story . You could have 8 or 16 ohm woofers, 8 or 16 or even 22 to 24 ohm HF drivers. Tweeters for 3 way systems could be almost any reading. You got out your impedance bridge or spec sheet and went accordingly. What makes things tricky is if you have woofers say with a 92 db sensitivity that can handle 200 watts RMS and HF drivers that are attached to horns with 108 db sensitivity but can only handle 15 watts RMS. So not only do have to match levels but deal with power handling issues. Then choosing the appropriate crossover frequency can influence the power handling capability. Altec driver for horns rated at 15 watts with a 500 hz crossover point could handle over 75 watts in some cases when crossed at 1200 hz before attenuation to match the woofer. The more attenuation of the HF driver the less likely of the driver failure. One system I installed required over 1000 watts for the 6 woofers and only 25 watts for the tw0 horns, one long throw, one short throw. Then you have to figure in the acoustic equivalent distances. to get the over balance correct depending on the reverberation constant for the room for a specific bandwidth covered by a particular driver in large space where the reverb time is over 1.5 seconds. Home systems are easy by comparison. Short reverb times make calculations and measurements in Anechoic chambers fairly easy and accurate. Big stuff needs to be done out doors. We always voiced systems late at night whether indoors or out doors to reduce back ground noise an hope for little or no breezes.