Voicing RF-7s

[leok]

I've enjoyed a pair of RF-7s for just about a year. The high-end detail and imaging qualities are tremendous. But there is a peak in the high end that adds an un-natural crispness and coloration that I would prefer to do without, especially in listening to classical music.

In studying the horn crossover network I found a very effective device for reducing that peak. There is a 2 Ohm resistor along one side of the high pass network (the crossover board closer to the mounting panel). If this resistance is reduced slightly, the peak vanishes. The resulting instrument timbres are much more natural, while the detail and imaging qualities remain.

The patch:

(Note, there is a 1 Ohm resistor on the other side of the

same circuit board. Don't mess with that one.)

Tack a resistor in parallel with the existing 2 Ohm resistor.

8 Ohms in parallel results in 1.6 Ohm total.

I currently have this installed. It may be a little too much.

12 Ohms in parallel results in 1.74 Ohms total.

I'm going to try that next.

18 Ohms in parallel results in 1.8 Ohms total.

I'll try that is 12 Ohms is still too soft.

I suspect Klipsch marketing lobbied for a brighter than flat sound. If you're looking for something a little more natural, this is an easy mod and it can be changed or removed in a few minutes. Personally, I'm very pleased with the results. I think people will find that the RF-7 is a great speaker, a worthy addition to the Klipsch line, once they figure out how to optimize its capabilities.

A final note. Please use good, low distortion amplification with the RF-7. This mod won't compensate for distortion.

leok

[mobile homeless]

Interesting post. Needless to say, RF-7 owners are lucky to have someone doing such experiments.

Unfortunately, I have noticed several things:

1. The typical RF-7 owner will look at a soldering iron like it's plutonium

2. The same aforementioned RF-7 owner does not employ tube amplification

3. Said RF-7 owner LOVES that brightness

4. Mr. RF-7 is probably located in HT system

5. RF-7 Owner Philosophy: More Watts = More Better

6. Mod will make falling "Pearl Harbor" Zero payload sound less WOW

You and deang might be sharing low fives...but the average RF-7 owner would rather sit in a vat of flaxen seed than ponder an internal update. But, for the lucky few...

kh

[leok]

Kelly,

Absolutely! But, were it not for the HT market, the RF-7 platform would be out of reach. There are people who do want to hear a more natural sound and for the few who will take the route, the RF-7 is an inexpensive alternative, but a soldering pencil is required. Legacy 3-way is another route, but a soldering pencil is usually required there too. My point is that the RF-7, with minimal effort, has a place, as a 2-way aproach, in the Klipsch lineup.

leok

[mobile homeless]

Yeah, well that response of mine was part tongue-in-cheek and part truth. Obviously, I think anything reducing that artificial brightness that some mistake for DETAIL is a GOOD thing. This same problem is why amplifier recs fall on minunderstanding as most now are biased towards an artificial detail hyped to take the place of real, honest, musical resolution.

kh

[leok]

Just a quick follow-up:

I increased the parallel resistor to 10 Ohms (making the combination 1.67 Ohms) and I don't think I want it any brighter. So, I would suggest, for a first try, go for 10 Ohms in parallel with the existing 2 Ohms.

leok

[mace]

Hi,

While I realize that this is an RF-7 discussion... is there any such mod on the KLF-30 that can be done to reduce the brightness? If I could shoot you a picture of the KLF-30 crossover would you know which resistor to tweak?

Also, how did you verify the reduction in brightness, or peak?? Was it just by listening or did you measure it?

I was at a rock concert recently (The Bears, with the singer/guitarist from King Crimson) in a rather small venue. I forgot ear plugs and the sound was so screechy I could hardly stand it. The consonants from the vocalist (esp. ssss's) were very sharp and piercing. I couldn't help but think about how many Klipsch owners want to duplicate that live rock sound and how the newer Klipsch speakers (Legend/Reference) really seem overly bright at times. It seems that somewhere along the line "ear piercing brightness" got mistaken for "accuracy in sound reproduction". The same goes with movie theaters... so often they have the sound at high volume levels which are piercingly bright, so much so it is utterly distracting. Seems home HT systems are duplicating this. I dunno, maybe my ears are just getting old but I find this emphasis on the high frequencies not pleasant.

Thanks,

Mace

[leok]

Mace,

I don't know about the KLF-30 design. It is probably somewhat similar to the Forte-IIs. I have auditioned the KLF-30 however, and found it to be quite smooth. I worry about the NAD. My last ss amp was an NAD 3130 and it was an extremely distorted disaster. There was crossover distortion in the output, op-amp distortion in the preamp, and an FET used as a mute directly in the signal path.

Try something very easy: Get 2 10 Ohm 20 Watt resistors and 2 1 Ohm 5 Watt resistors. Make 2 voltage dividers with a 10 and 1 Ohm resistor each, in series. Connect your amp across the entire network so the signal for each channel goes through a 10 then 1 ohm resistor. Connect your KLF-30s across the 1 Ohm resistors where the * are in the diagram below. Make sure you keep them phased correctly.

(amp +)---(10 Ohm)-*-(1 Ohm)-*-(amp -)

Now, listen. This will take more volume than you're used to using. Go slowly, be careful that everything is connected and working. The resistors will get warm and maybe hot. If you listen real loud you may want 50 Watt resistors for the 10 Ohm pair. But really you should just listen at moderate volume and 20 Watt will be OK.

If this sounds MUCH smoother, it's probably your amp. Try tube or ss class A. This is easy and worth a try.

As for the Klipsch 3-way crossovers, I have never tried to voice one. All I've ever done is upgrade the caps and inductors. If the KLF-30 is really all that bright, it would be a very complex undertaking because the bright area probably runs across the mid-tweeter transition so both sections would require tuning and matching.

For my work with the RF-7, I did it by ear. The entire problem is much simpler becase of the 2-way config. and the fact that the peak I was after already has a tuning circuit. I just tweaked that tuning circuit.

Sorry I can't provide more help. If you havn't heard the KLF-30 with a tube amp I encourage you to try the abuve experiment.

Tell me what you find out.

leok

[mace]

Hi Leok,

Thanks for the tip. I'll have to give the above a try since it does seem pretty simple. Is the basic principle that the voltage divider changes the tonality or does it just require that the amp provide more power output for a given sound volume? i.e., is the point to push the amplifier to higher levels for less distortion (out of the milliwatt range and into the watt range)? The 3240 is rated at only 0.03% THD at 0.25 W. I realize such ratings don't tell the whole story but at the same time I have no idea what the rest of the story is! Is there some easy way (I don't have an oscilloscope) to measure op-amp distortion? What is an FET (my NAD doesn't have a mute but it does have a "-20 dB" button).

I'm currently using the NAD as my pre-amp. When using the the NAD for both pre-and power amp the cornwalls sounded much smoother than the KLF-30's to me. When I use the NAD for just pre- and the B&K for power the cornwalls sound only somewhat smoother than the 30's (rock and classical). It seems that the KLF's are less forgiving with crappy sources somehow. The B&K power amp (class A and A/B) made a big difference in the listenability at louder volumes for both speakers, especially for the 30's... i.e. I didn't find myself wanting to turn it down because of the harshness but rather I don't really realize how loud it is until I try to speak (85-95 dB range)! The B&K has made the cornwalls sound sweeter and fuller and the KLF's not so harsh, less fatigueing. In my experimenting I've also found that speaker placement has been much better (i.e. less harsh) along the long wall in my room than on the short wall.

I realize that right now either my pre-amp or CD player is the weak link of my system and next year I'm planning on getting some sort of tube pre-amp. I think it was mobile who said the pre-amp makes a bigger difference compared to the power amp.

Mace

[leok]

mace,

The idea behind the voltage divider is as you mentioned: transistor amp distortion tends to be constant - not dependant upon output voltage excursion. This test forces a 10x voltage excursion for a given output and thus divides the constant distortion by 10. It's a rough check, but very informative. 0.03% distortion at 0.25W looks good. If this test shows a much smoother sound with the resistors I would wonder what the specs really mean. My Tripath is 0.05% at 0.5 Watt which is higher, and I doubt it gets lower at lower power. The Tripath amp sounds very smooth with the KLF-30.

The FET I was refering to is a field effect transistor that was used as an analog switch in the 3130. It prevented popping at power-up/down and inserted a lot of distortion.

If you really have a substantial ss distortion problem in the power amp, the divider test should make it obvious. Based on your descriptions, that's what I'm expecting. If you really have a reasonable signal and it's just the difference between the CW and KLF-30 then that's worth knowing. At that point, you would probably want to focus on the CW .. and that brings you back to tubes and SETs .. and that's plenty of fun.

leok

[mace]

leok,

Good stuff.

My 3240 pops when I turn it on so I guess I'll conclude no FET's. The B&K does the same type of pop with a different tonality (more of a momp).

I'll pursue the resistor test with the 3240 power amp side although it is sort of academic since the B&K is what I'm using long term now anyway.

Thanks again for the good info,

Mace

[Deang]

Leo,

You voiced your RF7's BY EAR!! Are you out of you mind! Now you have no idea what you have -- it might sound horrid, and you wouldn't even know it!!!

Kelly's best post of the month. LOL.

Jeepers, Leo, if you get that SET amp, you're gonna have to change all those resistors out:)

Was that you posting on the Welborne Forum about the Moondogs? Hee hee, gonna go with a solid watt huh?

[leok]

deang,

Very funny. In fact, all of those apply. I was thiking similar thoughts as I swapped various resistors in and out. But they're my speakers.

Yeh, 1 Watt, maybe 2 if I'm lucky. I don't think that's going to do it. Maybe my math is wrong. I'm not going to jump until I can get the arithmetic and what I hear to be at least in the same ballpark.

Meanwhile, with the small tweak, I'm having a great time with the RF-7s.

[Deang]

I wonder if Kelly's right. Maybe we're the only two people on the planet trying to press out the last ounce of musicality from these things.

I miss some of the aggressiveness of the SuperAmp -- but the imaging and trimensionality of the soundstage makes my DQ's sound almost flat by comparison. I have to dump almost everything the Aragon has into the DQ's, to get them to sound as open as the RF7's with a couple of watts.

[leok]

deang,

In this forum section "Updating Older Speakers" thread "511B Horn measurements" did you see comments by TBrennan about halfway down the page.

"The highs from the Altec are softer but sound more integrated to me, the highs from the CW are more extended but also seem to sound detatched. I think that the simplicity of the 2-way Altec gives more musical highs but have no doubt, they are definately rolled-off at the very top compared to the CW. This was always my best friend's big beef with Altecs."

Now, move the crossover point for the 2-way up to 2KHz and the high end is solved leaving the high hundreds to 2K at risk. Compromise, but not unreasonable. Throw in 2 smaller cones to better service the at risk portion and you have the RF-7.

TBrennen .. no intent to distort or take your comments out of context.

leok

[Audio Flynn]

This is fun to read!

I have said in the past my dealer is missing the boat by not demoing the RF-7 with tubes.

In my correspondence with LEOK he appears to have a comfort zone with his "micro tweaks" based upon sound knowledge of electronics and a reasonable ear.

I still have allot of studying to do to be comfortable in this arena.

I am convinced mass market SS seems to be a bit of a devil for high efficiency speakers.

[Deang]

I never understood the big deal about the cones and the x-over anyways. The low bass is vented, and the cones barely move except at the most outrageous SPL's. I think the 7's have some of the cleanest midrange I have ever heard. I don't see anything wrong with having the horn handle the majority of the midrange harmonics, and the fundamentals by the cones. It sounds O.K. to me:)