leok

This could be getting into some old territory where several of us continue to disagree. I use Jensen paper-in-oil caps for the direct series elements and Solen "Fast" capacitors for the parallel filter circuits. I Voltage conditioned all caps (subjected them to DC Voltage, both polarities at about half of their Voltage ratings or 150VDC whichever was lowest). I also use power line filtering for all sources and amps. There is, as a rule, no sibilance distortion/exageration from my RF-7s using any of the three amps listed. I say, as a rule, because there is such distortion occasionally, but not so often that I find it a problem. It's a tough problem but it can be virtually eliminated. The RF-7s have a very clean high end and any distortion there is painfully obvious. I do find, however, that once the system is cleaned up the RF-7s are a delightful speaker. Leo

Do you have a power line filter (one that filters out RF)? Also, I'd stay with the 4 Ohm amp output. Leo

1) Try using the 4 Ohm speaker outputs on the ST-70. 2) Get a cd with sinewave sweep 20Hz - 20KHz meant for audio system burn-in, put it on repeat, set volume for loud, but not set for structural damage, let it run for 20 hours (2 days, 10 hr ea). 3) set them up in corners, about 8" from front and side walls, for port optimization. I think those are the 3 most important things I did with my RF-7s. They are very picky about clean signals, but are really natural sounding when you get it right. I worked on My RF-7 system for 2 years, moved it into where I had been using the Chorus-II system and the RF-7s are much more of what I want. The Bass is better defined and goes lower. Highs are much cleaner and (believe it or not, smoother because of the improved detail). Good luck Leo

Brandon, If you half the voltage (and you may want to drop it by something greater like 1/5) you will be able to use all of the volume out of the receiver, it will simply be moved so that you get a better ratio of signal to noise. You're not having any problem getting things loud enough are you? It's just that there is a lot of background noise. By attenuating the output, the noise floor is reduced and you have to turn the pre volume higher to get the amplitude you want (that's a good thing). It's worth a try if you can easily obtain a simple stereo variable attenuator or can make a 1/5 divider. Leo

With a "noisy" pre, I guess a solution, if there is not a gain control; on the amp, is a voltage divider (attenuator) between pre and amp so that the pre can be run hot. What you want to do is be using a Volt or more of signal level out of the preamp. But this will blow you out of the house so you have to pad it back down to a fraction of a Volt before it goes into the amp. Cheap attenuators (volume controls) with RCA in/out connectors are available at various electronics stores. You can pick one up and see if it helps. Leo

Brandon, I suspect there is way too much gain in your system and you're not using any of the dynamic range of the pre .. just the noise floor. If there is gain on the amp, turn it down so the pre gain is higher. Otherwise try a Voltage divider between the pre and amp so the pre gain can be set higher. I'm not really a fan of preamps, but the performance shouldn't be as bad as you describe. Leo

Do you use a power line filter (one with RF filtering, not just surge protection)? SS can be very sensitive to RF. Belkin makes a few for under $100. Leo

I suggest you consider optimizing with a 2-channel amp. The Crown D-45 I use is in your price range, but it is really meant for use in a 19"rack, has non-standard connections (for home use) and has separate volume control for each channel. There are good integrated amps in your price range. I recommend you be careful not to go for power alone, but be sure you get good sound quality at all levels (especially low levels). A powerful amp than handles low power well is likely to sound good at all levels. A powerful amp that sounds thin at low levels will probably sound harsh at all levels. Some brands like Cambridge Audio and Music Hall may be a possibility. I've never used over 10 Watts of power, but I don't listen at high levels and my speakers are somewhat more efficient than yours. I can't imagine you'd need more than 45 to 50 Watts of very low distortion power. Also, consider getting a power line filter (available for under $100). Leo

I used a swept sine wave track (20Hz to 20KHz) on a CD that contains various audio "utility" tracks. The sine output amplitude reduces as the frequency goes up so the tweeter isn't blown. I set the amplitude so it was higher than I could tolerate (I wore ear protectors when in the room). Be careful! don't blow the speakers. A sine wave produces considerable driver motion at minimal power. I found the woofers moved at least +/- 1/4" at 20Hz.I set the cd player to repeat the swept sine track and let it play all day, two days in a row. The result was an overall smoother speaker sound with stronger bass. Other tips: speakers in corners to reinforce rear ported bass, power line filtering, amp that is low in distortion at low power. Good luck, Leo

Some possibilities to consider: "Acousta-Stuf" is a very user friendly acoustic damping material available at Parts Express. I found it made Chorus-II bass less boomy and much better defined. I think I used the recommended formula of 1/2 lb / cu ft. The product is inexpensive, easy to use, and easy to remove if you don't like it (I tried it in my RF-7s and didn't like the results). The Chorus-II needs a very low distortion signal at low power to give you clean highs. A power line filter should help (I find it does). Then there's the amp itself. I like the highs with tube amps, but with my no-feedback amps, the Chorus-II's midrange impedance peak resulted in a midrange sound peak that I didn't like. I've found the Crown to have clean highs and no midrange peak (very good overall sound). If you do use tube amps I suggest you try the 4 Ohm output to minimize the amp's susceptability to the speaker's impedance swings. Crossover upgrade is worth the effort, but that's possibly something for later. I found that upgrading crossover caps resulted in further cleaning up of the high end. Congratulations on your new Chorus-IIs. They're a great speaker and fun and rewarding to customize. Leo

Acoustic suspension (one of the first or maybe the first): not efficient. They sounded unusually good at the time. I have begun to suspect that the inefficient acoustic suspension speakers that took over in the 60s did so because the new, more powerful transistor and global feedback tube amps sounded so harsh at low power. The inefficient speakers made the amps put out more power where they sounded better. Leo

On my pp amps I've had a 29 Ohm 2W resistor across the speaker terminals (in parallel with the speaker). Those amps have only the one 4 Ohm output. It's probably a good idea to try adding a damping resistor there first. If you like the general affect you can try resistance (several 10s of KOhms if I remember correctly) on the transformer primary. I'll look up my notes and post some sample values. Leo

Dean, Good point. I found another way to limit impedance excursions and damp parasitic oscillation also: place a damping resistor on the input side of the output transformer. Not as easy as the output method, but I found more effective. I can look up the value if anyone's interested. That approach is on my SET amps. I'm in process of revising the pp amps and may install it there too. In any event, good point, I had forgotten that I also find damping resistance of some kind a plus when dealing with large speaker impedance variations. Leo

4 Ohm (2 Ohm if you can). Chorus-II doesn't need much Voltage, but the impedance swings are better controlled with lower impedance amp outputs. Both of my tube amps are set for 4 Ohm (and I still prefer the ss Crown or pwm on the Chorus-IIs because they ignore the high impedance peak in the midrange). Bear in mind: my amps have no feedback so output impedance is higher than that of feedback amps. If your amp is a feedback type I'd still go for 4Ohm out, but would expect reasonable handling of the mid high impedance peak .. better than the no feedback types. Leo

I've had a pair of RF-7s pretty much since they were introduced. I had Forte-IIs when I purchased the RF-7s and have since replaced the Forte-IIs with Chorus-II. The 2 and 3 ways are very different, and have different advantages. The RF-7 does go lower than the Chorus-II (not lower that the Forte-II), and the RF-7 has cleaner upper midrange to top end performance. The Chorus-II has better overall dynamic performance and a cleaner lower midrange. I recommend getting a swept sine wave (20Hz to 20KHz) burn-in source, available on many disks: one that attenuates the signal as it goes up in frequency so it doesn't fry the horn, and run it through your new speakers at a high, but reasonable (so you don't blow a driver winding) volume for a couple of days while you're at work (16+ hours total). Remember, the goal is break-in not break. The RF-7 required substantial break-in. Second, get over the fact that a 2-way doesn't sound like a 3-way and you might find that there are instances in which a 2-way outperforms the 3-ways. I find that with music that gets very complex or critical in the upper mids and top end (some types of cymbals, pipe organ reeds, and violin harmonics bow and body sounds) is fatiguing on the Chorus-II but not the RF-7 and that I will give up on the Chorus-II and move to the RF-7. I don't know that the newer Reference speakers are as good as the RF-7, they probably are, so, If you're feeling "stuck" with them you might spend a little time to hear what they can do. If not, I guess you are stuck. Good luck, Leo

There is a 6uF N.P. electrolytic as high pass for the mid and two 2uF (blue plastic of some kind) caps in the tweeter high pass. I'd replace the 6uF with at least a good metalized polypropylene cap. There are plenty of opinions about the two 2uF caps. I like Hovland "Musicaps," but did find I had to "Voltage condition" them by applying about 80V DC in each (of two) polarity to each unmounted cap before insertion. There are plenty of opinions about that also. Good caps make a substantial and positive difference in the sound of the Chorus-II. I also added some plastic acoustic damping material (Acousta-Stuff?) in the cabinet which I found improved bass definition (plenty of opinions about that). And, finally, I set the cabinet on spikes, building up the base, front and rear inside the riser, and attaching spikes so the riser is just off the floor. That cleaned highs and lows (plenty of opinions about that). The Chorus-II is a nice speaker and fun to customize if you're so inclined. Give them good amplification that has low distortion at low power. (not all amps do that). Leo

I originally had reservations about the size, but reviewing the size of your room I would back the La Scala choice with Chorus-II as an alternative. Leo

Forte-II may be ideal considering your room size. Chorus-II is also good (I prefer it, but there are minor tradeoffs, one being the larger size). I don't know if you have room for anything bigger (I don't). Thebes has what I think is a KG series model that I was very impressed with. Maybe he'll see this and help out. The RF-7s I have are tricky to get right. They can be considered "clinical" or "detailed" depending on the source and one's mood. Whatever speaker you end up with, I recommend using the 4 Ohm output, if one is available, on your amp. The lower amp output impedance improves handling the significant impedance swings of all of these soeakers. Leo

Wolfram, Capacitors do have a remarkable influence on audio. Getting the right match can be tricky, but is often worth the effort. Congratulations on finding a mix that improves your system. Leo

tigerbalm, I have been very happy with a set of RF-7 pretty much since they were introduced. I find, as I have with any speaker/amp combination, all you need in power is enough to handle your peak demands, plus a 25% to 33% margin for loss of linearity as clipping approaches. Figuring out the "peak demand" may be a bit tough. Fortunately for me, I had a digital oscilloscope and found with +/- 4V peak swings into my Forte-IIs I was driven out of the room. "Efficiency" of the RF-7 is a bit higher so I still consider +/- 4V to be all I generally use. If that +/- 4V happened to occur playing exactly the famous 2.8 Ohm frequency then the amp would require 1.43 amp and 5.72 Watts when playing that note. Add some margin for loss of linearity as clipping approaches and you're still under 10 Watts. In reality I use a 4 Ohm output on a 3.5 Watt tube amp most of the time, but I don't listen at levels used by some on this forum. I suspect these are the kinds of numbers you are curious about. They do work. Usual problems with amps and speakers (the RF-7s included) is high output impedance with tube amps, responding to the speaker impedance swings (I find the peak in the mid horn of the Chorus-II to be much more objectionable than the dip in the RF-7), and low power distortion with ss amps. There are tube amps with sufficiently low output impedance and ss amps with sufficiently low low-level distortion, but one has to select with some care. The amount of power you need is a function of how loud the sound is and making sure the worst case current/Voltage requirements are met. Leo

Mike, If it's wired for 8 it's probably not worth the trouble of changing to 4. If the amp sounds a bit "thin" then it's worth considering. Impedance of the Chorus-II has a peak in the midrange which the high impedance of a no feedback tube amp will favor. I don't know about the KLF series. Try the amps for a while. If optimization is in order that can be done any time. Leo

Let us know what you think. Also, if there's a 4-Ohm output, give it a try .. both speakers. Leo

There is a form of "delta" modulation in which pulse widths are all equal length and the modulation chooses a 1 or a 0 for an entire clock cycle. These are good for memory devices such as digital delay lines which can us single bit "word" memory chips to store waveforms. I think SACD is a type of delta modulation. Leo

A phono preamp is a precise exercise in low noise analog design. There are versions that digitize, then do RIAA equalization. But for line sources, one doesn't need a preamp: the amplitude is already high enough to drive most amps to their rated power (there are exceptions such as the Wright SETs). So, all that is really needed is a passive volume control and source switches. Digital equalization "preamplifiers" do exist. I guess those are the equivalent. Leo

meagain, I've been using a Tripath amp for years and have compared it over time to other amps. In a way it IS a case of how I would like it if it cost $600, or $2000. What I've suggested to people who hear it is, if they're going to spend more money on an amp it should sound better than the Tripath. What I've found is the Tripath is a great lesson in what low distortion at low power does for Klipsch speakers, as long as users keep other distortion producing things such as preamps out of the audio chain. Often people think the high end is muted or soft (thus the reference to higher output impedance at 10 to 20 KHz). But I think what they are really hearing, sometimes for the first time, is a lack of high end distortion that they've heard in all amplified sound, that gives it a kind of kick or "slam." Without that distortion slam they think it's rolled off. But it isn't, that's just the way things really sound, and obviously several people here are finding they like something closer to the real thing. I have found amps that I prefer, but they all cost much more. I think the Tripath amps are a great reference. One of mine is now on loan with a pair of RB-5s to a friend who is trying to design a new system. Based on the Tripath performance with Klipsch speakers, he is basing his new multichannel system on Klipsch speakers. Leo