Powering Polk RTia9's

[Gmoney]

It is the phase angle between the applied voltage and the current drawn by the speakers. AC voltage and current are referred to as "phasors", (think vector on the mech side that most people understand). Phasors have magnitude and direction like vectors do, but the direction in this case is the "phase".

Phase Relationships in AC Circuits

For a moving coil loudspeaker, both the magnitude (in ohms) and phase angle (in degrees or radians), would vary with frequency. Below are the impedance plots of the RTi A1 vs frequency.

SoundStage! Measurements - Polk Audio RTi A1 Loudspeakers (3/2010)

Phase angle (in degrees):

View attachment 34265

and the magnitude in ohms:

View attachment 34266



It depends on how far you sit too, but given that you don't push past 75 dB, based on the published specs of he RTi-A9 that says:

Sensitivity: 90 dB/W/meter
Nominal impedance: 8 ohms

so if you sit from say 15 feet, you need about 0.33 W to get 75 dB with just one speaker. For every 3 dB increase in SPL, you need 2X the power.

S&V's review (https://www.soundandvision.com/content/polk-rti-a9-speaker-system-ht-labs-measures) showed the RTiA9's bass response from 40-300 Hz very flat, so if you are a bass head, the only thing you can do is to use them with subwoofers. REQ such as Audyssey (with the Editor App), YPAO, Dirac Live can also help.

The measurements did show some nasty phase angles at below 70 Hz, so again if you use sub(s) and set the crossover frequency to 80 Hz, you will take care that potential issue too, at least to a large extent if not totally.

Phase angle issues will result in more power/heat the amp's output devices must dissipate for the same current draw by the speakers. External fans may therefore be needed to help remove some heat.

PENG, as usual your rule bro! I really enjoy reading your post I always learn something from them. Those RTi a9 speaker’s are some nice looking speakers. One would think Polk would update those
speakers, the build on those are really nice I have the RTi a5’s I like them a lot. From what I was told by Ken at Polk they used a different driver on the a5’s midrange is very sweet on the a5’s. There are some over at Polk who have done Mods on the XO and changed out the driver’s and ended up with a very nice pair of tower’s. Sad that Polk didn’t man up and redo their RTi line given they Actually built a very nice speaker Cabinet for that line.

 

[Fuelsrock]

Thanks for the input guys! I was able to get Best Buy to price match the Denon x4500 for $899. I still haven't got the towers yet, but hope this will be enough to drive my 5.1 set up. If you guys have any tips on maximizing the full potential of the Denon, let me know. I am a beginner and am now FULLY tapped on my Home Theater budget.

 

[PENG]

Thanks for the input guys! I was able to get Best Buy to price match the Denon x4500 for $899. I still haven't got the towers yet, but hope this will be enough to drive my 5.1 set up. If you guys have any tips on maximizing the full potential of the Denon, let me know. I am a beginner and am now FULLY tapped on my Home Theater budget.

Yes, there is one good tip Gene offered when he reviewed the 3600 but it is only applicable if you are using it with an external amp. So until then, you don't have to worry about that one. Do try to run Audyssey properly by following instructions to the letter and use the $20 editor app.

 

[mtrycrafts]

I guess I was "sold" in the Magnolia Sound Room then. He played a Arcam 390 at volume 65 and then cut it over to the Denon 2600 and the sound difference was night and day....

Interesting test. Who knows how it was really set up without proper proper level matching and not with music.
Easy to cheat on setup especially to one who may not know what is involved in basic level matching.