Preamp and impedance question

EPDR is not a meaningful term for this topic. That is a term more applicable to solid state amplifiers operated in the linear region and is most applicable to a discussion on thermal dissipation, not drive capability or optimization for frequency response and THD.

"And that if it say -50 degrees in the bass, which is not uncommon, combined that with the "5ohm" of what the manufacture "says" the speaker is, "could" represent a combined EPDR ("equivalent peak dissipation resistance") load even down to 2ohms depending on what the -phase angle is."

thats good news that I can just add the volume pots. =)

If the amp is a stereo amp, then a balance control is a really good idea. If they are monoblocks and each has its own volume, you have to manually adjust the volume for each channel- that gets old fast!

@georgehifi Please excuse my limited knowledge, I don’t fully understand the phase angle and stuff.  But to clarify, my X5 has one 12” Eminence driver and one 12” powered Eminence subwoofer by Hypex Fusion NCore plate amp.  

The cross over frequency is 90Hz. AMT - 1 kHz and up
12” mid range - 90Hz to 1 kHz
12” powered subwoofer - 90Hz and below
But that 90Hz to 1 kHz is exactly where the impedance dips to 7 ohm.

actually, I can do a test on my current amp which supports 4 ohm.  And I have been connecting my X5 to 4 ohm.  I did a brief test earlier and I remember there is no difference on my X5.  But I remember there is an improvement to use the 4 ohm tap on my Zu Omen Def.  So, it seems this really depends on the speaker.  Maybe the phase angle is less relevant in a open baffle speaker?  
But I may change speaker or I may sell this.  Definitely having a 4 ohm tap is more future proof, but I am not sure if I want to spend 20% more for the unknown future.  If I happened to buy a new speaker, maybe I should just buy another better matching amp .... decisions,  decisions .... 

The phase element, if Georgehifi is relating it to EPDR is not relevant. It relates to thermal dissipation in output devices which tubes don't have an issue with.

gte357s OP
@georgehifi Please excuse my limited knowledge, I don’t fully understand the phase angle and stuff.

EPDR is the -phase angle (expressed in -degrees) combined with the low impedance measured, and represents a "far more severe loading" to the amplifier than just the impedance itself, don’t listen to any idiots that says otherwise.

Here is the Wilson Alexia, it's one of the worst bass loads I’ve seen, and so thinks HNRR and Stereophile, it has an EPDR of 0.9ohm!!!!. And the reason why you should get the 4ohm transformer tap as well as 8ohm.

https://ibb.co/stQ44Ry

https://ibb.co/C8d2Zny

Cheers George