RF-7 II Amplification - The difference between 200 and 300 watts?

[cornfedksboy]

With my Onkyo TX-NR708 +/- Marantz MA-500u Monoblocks, I do not enjoy 2 channel stereo or Pure Direct in my HT room. Perhaps it's my room (although it was good with the WF-35s), but the mids are too watered down to be enjoyable. I do THX Music (5.2/7.2) in the HT room with Audyssey EQ as the RC-62 truely balances out the missing mid-range in the 82s.

[onawav]

What about the RF-7 II/Onkyo 809 combination do you feel is lacking?

How far do you sit from your speakers? What is a reasonable volume? Those things combined with the sensitivity of your speakers have a great impact upon how much power you need.

I sit 10' from the speakers. With the calibrated Onkyo, a volume of 70 is about an loud as I'm comfortable listening at. In terms of something lacking, I'll need to listen more to gain a better feel, but I'd say a bit more bass response would be welcomed.

Ultimately, after making a substantial purchase on the speakers, I want to ensure I'm providing a sufficient power source to get all I deserve out of them.

[onawav]

Out of curiosity, did you re-run Audyssey after hooking up the RF-7s? Did you follow the procedures for taking measurements (use a tripod, use all measurement locations, start at the primary listening position, and fan out from there about 2-3 feet away at a time, etc)? I find that I vastly prefer stereo mode over Pure Audio mode, but it depends on what you're looking to hear I guess.

Yes, I did re-run Audyssey after I installed the new speakers. I like stereo, too, but I feel the Pure Audio mode is best for critically listening to the RF-7IIs only. The added subwoofer of stereo is nice. I'm playing with all the listening modes. There are so many I'm not yet sure which I prefer.

[onawav]

It only takes one vibrating picture frame to make me nuts.

I cannot recall any amp design I have used causing listening fatigue like room issues or bad digital jitter.

Completely agree! As a side gig, I DJ parties and weddings and my living room also houses my DJ gear for practice. Through used of my Yorkville LS801P (18" 1500 watt sub), I've identified and eliminated plenty of rattles. Still have some room reflection I'd like to tame, though.

[kx200]

I've had my RF-7 II's for about half a year now, and can say that with a well matched amp I have never heard a better sounding speaker. They are, however, very revealing of any shortcomings of your source or equipment. I first had them driven by a Harmon Kardon "high current" 120 watt stereo receiver and the bass was somewhat anemic. But after running them from the amp section of an old 160 watt Sansui G-9000, the bass was strong enough to punch you in the chest while still being very clear and accurate. They also sounded very good driven by 2 different Fisher 7591 tube based amplifiers (KX-200 and 500C). It is my understanding that these speakers may have a serious impedance dip in the very low frequencies and need an amp that can keep hold of the speakers down there, but once you find the right amp you will be rocking!

[StephenM]

I sit 10' from the speakers. With the calibrated Onkyo, a volume of 70 is about an loud as I'm comfortable listening at.

Good evening onawav. For starters, I'd recommend setting your volume to the relative level which shows volume as + or - dB from reference, ie +5dB or -15dB. This gives a better idea of the volume level than the absolute level. Also, since music has no fixed encoding level, it'd be useful to know the actual volume at the listening position from a SPL meter.

FWIW, I will try to give you a rough idea as to what kind of power you'll need: while your speakers have not been measured that I know of, you can get a rough idea of their actual quasi-anechoic sensitivity from their predecessors, the RF-83s.

http://www.hometheater.com/content/klipsch-reference-rf-83-speaker-system-ht-labs-measures

As you'll note through the bass range (200Hz until it rolls off a little over 40Hz), sensitivity is on average about 95dB, which is pretty darned high, and ultimately means you probably won't need much power for bass, although minimum sensitivity is about 90dB at a little over 1kHz. Because lack of bass is your complaint, I'll run with the 95dB figure. Also of note, impedance does dip a bit below 4 ohms in the upper bass, and is rather reactive, which spells trouble for an amplifier.

With that data, you can play around with this little calculator: http://myhometheater.homestead.com/splcalculator.html

To be conservative, select do not consider placement. 95dB w/ 1 watt will be the sensitivity at an 8ohms, and 92dB w/ 1 watt will be the sensitivity at a 4 ohm load. With that input data along with a 10 foot distance, you would need a bit under 100 watts @ 8 ohms or 200 watts @ 4 ohms to achieve a 105dB peak with one channel driven. Because your Onkyo is THX Select 2 rated, we do know it is certified by THX to swing a 12.5 ampere peak on its main channels, which equates to 625 watts at 4 ohms. This suggests to me that unless you're listening at ridiculous levels (which doesn't appear to be the case), even the Onkyo shouldn't be limited by raw power/current drive. However, because the Onkyo isn't rated to drive a load below 4 ohms, which the RF-7 II does very likely present at some frequencies, this could be a source of trouble. With that in mind, I wouldn't spend a lot of time worrying about the differences between 200 and 300 watt amplifiers (which you can also see in cold hard dB on the calculator), but focus on getting something that will competently drive a speaker with low impedance dips. Either Emo should serve the purpose in that regard, although I know of no hard data about their ability to drive sub-4ohm loads.

I'll need to listen more to gain a better feel, but I'd say a bit more bass response would be welcomed.

In addition to amplification, I'd suggest that playing with placement could yield significant gains in this department for a total cost of $0. You would need to use Pure Audio mode for this since it bypasses Audyssey's room correction (which would be worthless if the position changes), and re-run Audyssey when you were done. For example, placing your speakers in a corner for example could yield considerably greater bass then having them away from walls. Moreover, if your seating position happens to be in a null, amplification isn't going to fix your problems. Personally I think it is unfortunate that Onkyo doesn't have a pure audio mode that does engage the subwoofer for 2 channel music.

[cornfedksboy]

Personally I think it is unfortunate that Onkyo doesn't have a pure audio mode that does engage the subwoofer for 2 channel music.

It does. You just turn off Audyssey EQ in the menu and switch to 2-channal stereo. Sub-woofer is activated and everything is flat vs the source.

[onawav]

Thanks StephenM! That is great information. Very insightful and helpful.

[StephenM]

It does. You just turn off Audyssey EQ in the menu and switch to 2-channal stereo. Sub-woofer is activated and everything is flat vs the source.

True enough!

[psg]

Either Emo should serve the purpose in that regard, although I know of no hard data about their ability to drive sub-4ohm loads.

I am surprised that noone has tested them for that by now, e.g. this thread:

http://www.avsforum.com/avs-vb/showthread.php?t=855865

[Fish]

Either Emo should serve the purpose in that regard, although I know of no hard data about their ability to drive sub-4ohm loads.

My 125 watt Emotiva amp drives my 7's(sub 4 ohm) to cabinet busting levels for as long as my house can stand it, what else is there to know?

[StephenM]

what else is there to know?

Hard data to quantify performance is always a nice supplement to subjective evaluation.

Also, does anyone know what the impedance curve of the RF-7 II actually looks like, ie minimum impedance, phase angles, etc?