Hi Louis,
I check a bunch of my magazines for a review of your speakers, and I only found one from 1987, the Infinity Reference Standard 9 Kappa.
And I also found listing for the Infinity Kappa 9 from 1988.
And another listing for the Infinity Kappa 9.1 Series II, from 1996.
And one more Infinity Kappa 9.1 Series II, from 1995.
If you can describe me how many drivers and what size they are, I will be able to pinpoint more the year.
Also, which year is your Sony STR-B930 QS receiver?
* Now, if your Kappas have two 12" woofers per speaker, with a total of 7 drivers per speaker, you're in luck. (Is there one ribbon tweeter on the rear?)
If your Kappas have a total of 4 drivers, they are the most recent models, but I think there is a mistake in two of my magazines, this happened in those years.
That Sony receiver is a powerhouse or what?
* Take note: Are there 4 controls in the back? In addition to that, there is a 2 way toggle switch. Set that switch to it's "Normal" position. Because if you set it in it's Extended position, your Kappa 9 will be almost impossible to drive with most amplifiers at more than moderate levels. That's a fact!
Also when this toggle switch is set to it's "Extended" position, the impedance of your speakers drops considerably. A very high current power amplifier is a must. Also they are quite inefficient.
With a very powerful amplifier, your Kappas are beautiful in their total response across the entire audio range, with a low extension down to a clean 25hz, and the high frequency goes beyond 25khz.
You don't really need a subwoofer with these 4 x 12" drivers, they push a tremendous amount of air (with the right amp, of course).
But that toggle switch was your main culprit, because even with an amplifier that gives 350 watts RMS per channel into 4 ohms, will shut down at 90 db levels! And there is no way that the Yamaha RX-Z7 can deliver this huge amount of power. You need a very heavy power amplifier for that, not a receiver, even the flagship of any brand. You'll be much better off with two Emotiva Mono-blocks XPA-1 to drive your speakers to their full potential. But you will be rewarded with magnificent sound indeed. They demand the very best amplification. Their impedance drops easily below 4 ohms too.
Your Yamaha RX-Z7, even if it's a nice receiver, is no match for your speakers, period! Even in bi-amp mode. It needs an external amp(s) to power your two front very HUNGRY Kappas.
Also, I highly recommend that you set the treble controls to their lowest setting.
I hope this help you understand now what you are facing here.
Regards,
Bob
Note: If you want to know more about the beauty of your speakers, let me know, and I will provide to you the entire review (I will have to type it). So maybe, it will be best to do it in the "Speakers" section, just let me know if you are interested.
If you are, just start a new thread about "Full review of Infinity Reference Standard 9 Series II Kappa". It's my gift to you.