New RF-7 II's with tube amp a bit harsh, but sing with khorns

[jcm]

This thread could probably be classified under "speaker break-in" or "room acoustics", but here goes:

I received a pair of RF-7 II's last week, and hooked them up to a demo unit of a PrimaLuna ProLogue Premium Integrated amp. I let the speakers break in for over 40 hours so far, and the sound is still very harsh in the midrange. The PrimaLuna is using EL34's, which are generally known to have a sweet, if a bit forward, midrange, so the tube might have a little something to do with it.

The room is huge: it's basically my downstairs, which is about 1000sqft, with 25' high ceilings and not much in the way of acoustic treatments. My previous system did not have anywhere near this much harshness (old Infinity SM225s with a Denon 4806), so the room can't be all of it either.

Speaker placement is about 8' apart, 12' from the listenting area. The downstairs isn't square, and kind of meanders, so there is no "long" side, but the shortest wall is over 20'. Because of the wall-mounted TV above the fireplace and some other room considerations, I don't have a lot of play with speaker positions.

Anyway, I took the PrimaLuna upstairs and hooked it into my (very well broken in) khorns, and the sound was simply mesmerizing. No harshness at all, great dynamics, tons of khorn bass.

So, on to the question: is this just a matter of breaking in the RF-7's for another 40 hours? Perhaps move to KT88's? Or is the room too lively without treatments? I'm sure my wife would love to add tapestries all over the place, but that cuts into the budget for a turntable

Thanks,

John

[derrickdj1]

The RF 7II's are a different kind of speaker than your K-horn. I expreienced the harsh sound that people refer to Klipsch speakers when I setup my RF 7's for the first time without autocalibration. It is most likely a problem with the setup and room. Have you tried the emotiva pre-amp/amp with the 7II's? Room reverb and , standing waves are also a factor. Eight to12 feet apart and if possible 1-2 feet from the back wall is appropiate for setup. Most RF 7 and 7II owners use a stronger amp since these speakers love adequate power and high current for their best performance. After I corrected for room reverb and standing waves in the room, the harness went away and the bass was no longer out of control. Others will give more tips and advice for your setup.

[CECAA850]

Most likely the room. If you could lug the 7's upstairs to your other listening room, I'd bet they'd sound completely different.

[jcm]

This is going to be an all-analog system (with the exception of a Sonos/DAC), so using room correction is not really an option. I'd rather marry the amp and speakers well and get around that. But that may not be possible. As for power, the Primaluna has serious authority and weight. Quite surprising given the power ratings, but I think we all know that 35w of power from a serious class-A amp will always trump 120w of power from an AVR. Or at least it has in my experience. I am thinking tube amp upgrade for the khorns...

LOL, I'm not sure if I can lift those RF-7's upstairs. They are beasts I'm not entirely sure it's the room, though, as I used to use a pair of RB81's and Infinitys, and neither reacted this way. But I bought both of those systems used, so they had already been broken in. I let the system run for 12 hours straight today, and it sounded better on good source material. I will say this about the RF-7s: garbage in = garbage out x 10. Compressed modern music sounds awful at high volumes.

On second thought, I would like to try some room autocorrection. Emotiva should be coming out with their XMC-1 next month, and I have an upgrade card. Perhaps I'll put that one upstairs and bring the UMC-1 down and try that out. I wish Emotiva would make a standalone room correction solution. Or better yet, a combined room correction/DAC!

[Danzo]

There is 35W power and there is 35W power. What is Prima Luna power rating at 2 Ohms? For Class A, may i suggest you do it properly and go for full class A or high bias Classe, Krell, Pass Labs?

Also, while TACT on XMC-1 is likely to turn out pretty nice, you would probably gain more from speaker repositioning and room treatment;

[pzannucci]

I received a pair of RF-7 II's last week, and hooked them up to a demo unit of a PrimaLuna ProLogue Premium Integrated amp. I let the speakers break in for over 40 hours so far, and the sound is still very harsh in the midrange. The PrimaLuna is using EL34's, which are generally known to have a sweet, if a bit forward, midrange, so the tube might have a little something to do with it.

If you read the Stereophile Measurements section it explains that there can be very high fluctuations in the frequency response on this amp due to the very high output impedance.

The amplifier would really like a speaker that does not have a wild response curve such as the RF7's so it could very well come down to component synergy.

As the variations for the bass are not near as bad on the khorns (plus much stronger than the RFs) so it is likely the khorns would not to sound as lean with the mid/highs overly prominent as the RFs.

The RF7's would do with a very low output impedance and a lot of current. Neither are available in that type of amplifier to drive the bass section adequately.

[jcm]

I rarely read the test measurements in Stereophile, but this is a great catch! According to the tests, I should be using the 4 ohm tap instead of the 8 ohm tap. I will give that a whirl and see what happens.

I wonder if the Dialogue series is better in this regard. Stereophile has unfortunately not tested the Dialogue 1 or 2.

[jcm]

Wow, what a difference! I moved the speakers to the 4 ohm taps, and the midrange is now solid but not overwhelming, the bass is heftier, and the soundstage just doubled in width. I can't believe such a simple change could make such a huge difference. Thanks for the catch, Peter!

[jcm]

So being a tube newbie, how much does the choice of tube affect the impedance curve, if at all (say a KT88 vs EL34)? Or does it come down to transformers, etc? Any info appreciated.

[craigtone]

I had similar issues driving RF-7's with a Dynaco ST-70. The RF-7's are VERY sensitive to tube rolling in that most tubes are too transparent bringing out the brightness of the Tractix horn. To be honest, the single most improvement I made was the Dean Wescott crossovers in the RF-7. That took most of the harshness and crossover distortion out of the picture.

[erik2A3]

I was going to ask if that amp had 4 ohm output taps -- evidently it does and things sound better. Good. Though I'm not one who worries too much about breaking in three feet of IC (that's just me), mechanical break in of driver surrounds and spiders can help improve frequency response balance, so a little more time on the drivers will probably help, too. Enjoy your system!