The modified RF-7s

[Deang]

It was becoming apparent to me that equipment change outs were not going to achieve the level of performance I was looking for. My first DQ-10 restore demonstrated that upgrading the quality of components in the crossover netted improvements in every area of things related to sound. I really wanted to implement some changes to the RF-7's, but without a schematic -- I was hesitant. Leo saved the day by tearing his down first, and ended up holding my hand through most of the project. We did however, end up taking different paths.

I went with Auricaps and ICW's, and Leo went with the Jensen PIO's. I ended up building completely new boards, and changed out every part. Leo is still using the PCB's and two of the three original inductors. I also removed the Monster Z wire, and replaced it with the Northcreek silver over copper wire. The runs are all between one and two feet, and since they are after the crossover -- probably do not make as much a contributon to the improvement as the crossover parts themselves. I think using the wire in the Cornwalls made the difference it did simply because the old zip cord in the Cornwalls was in such bad shape.

I also removed the birwire capability by going to two posts per speaker. The leads from the crossover are soldered directly to the back of the binding posts.

In Summary

Auricaps in the tweeter circuit

ICW's for the Klipschcones

Mills non-inductive resistors

14 AWG Solen Perfect Lay for the woofers

Custom wound HF inductors from Madisound

Northcreek 14 AWG silver over copper

Dayton low mass binding posts

Cardas solder

The Results

The noise floor is in the basement. Where previously I spoke in degrees of grain when comparing the various components I have had in this system -- there is now none. The midrange and upper treble is the cleanest I have ever heard come out of these speakers. I can easily drive them into the 110 db range without pain or earbleed.

One thing I half expected to happen, and did happen -- is that these RF-7's are now tipped up somewhat. The treble goes on forever, and sometimes I wish it would stop. The midrange is more forward, but at this point it could just as easily be blamed on the EL-34's in the Quicksilvers. I will wait a couple of weeks, and then pick Leo's brain for a new resistor value for the bandpass circuit running in series with the horn. I am hoping however, that things settle in.

Since I can modify the treble signature, the forwardness is of no consequence -- the emphasis here should be on the cleanliness of the output, and as I said, I do not believe continued equipment change outs would ever garner this level of clarity. The best sound is clearly achieved by having decent components and related parts from the beginning of the chain to the end. There is really no logic in using $2000 monoblocks to push a signal through $2 capacitors and oxidized wire.

The Quicksilvers

Mike Sanders of Quicksilver believes in minimal circuitry, and the Mono-60's have 5 parts in the signal path. Looking at the bottom of the amp, there seems to be less parts overall then the Apollos had. This simple ultra linear based circuit puts out 60 watts of EL-34, of which there are four per amp.

Oh yes, more power than I need, and many, including Dennis Had of Cary, and even our very own beloved Pompous Azz would say "Power corrupts".

I don't know if I can agree.

The low order distortion of a SET amp running past it's limits produces distortion much more objectable to my ear than a well designed 30 wpc push-pull lazily lobbing along while producing the same output level in SPL. Since I don't own speakers with ruler flat impedance curves, or have sensitivity ratings climbing into the mid 100's, typically listen to music which I consider somewhat demanding, and enjoy the ocassional live session with the drywall shaking down around me -- will always end up taking low powered amps into areas they were simply not designed nor intended to be. That's just the way it is.

The bantering regarding the 'best' circuit or tube type is a complete waste of time. There are just too many variables involved. I've had several different amps in my system over the last year. They all sounded great. I put the Scott on the RF-7's and it sounded great. It didn't sound like the Superamp did, but it sounded great. Did it sound as good as the Superamp? Yeah, it did -- but it was different. So, old pentode push-pull with lots of buttons sounds as good as new fancy class A triode amp with no feedback. Go figure. There are NO absolutes with this stuff. I got the Apollos -- they sounded great. O.K., they sounded really great -- but within limits. I don't like limits.

I will refrain from comments attempting to compare the Apollos to the Quicksilvers directly -- as changing crossover components, internal wiring, speaker cable, interconnects, and preamps -- precludes making any valid comparison, so -- I'm off the hook.

I can however, make a comparison dealing with the systems as a whole.

Do I miss the Apollos and AE-3 DJH? Well, I miss the bass. The Apollos and AES combo definitely had better bass. OTOH, the leaness in the bass I am presently experiencing might be related to the tipped treble. I also know the EL-34 is generally speaking, somewhat limp-wristed in that area. I remember this same leaness in the bass when I put some Siemans EL-34's into the Superamp. Maybe my ears favor the beam and triode tubes over the pentode types? Of course, the Scott uses pentodes and I don't seem to have a problem with that.

I would characterize the system I was listening to last month as tonally rich, with a softness in treble and good bass slam. Superior imaging and transparency were the order of the day, but with a propensity towards pinching and hardness when driven to live levels. The system as it is now -- excels in the area of speed. The Quicksilver sound is aptly named. The Monos sound 'fast' on the RF-7's. They remind me of the Superamp DJH in this area.

At the low to moderate volume levels the two systems have much in common. I sure wouldn't say the differences are jaw dropping by any stretch -- and least not with my music (noise). I definitely have to give the Apollos and AE-3 DJH the edge in bass slam, and the Quicksilver/Cary combo taking the midrange and treble -- it is crystalline without giving in to sterility. The midrange of the Quicksilver/Cary combo sounds a little incisive -- but not near as cutting as the Superamp did. I'm sure the treble has much to do with the improved crossover parts. Since I never heard the Apollos with the RF-7 mods -- this statement is probably not fair. I will say at this point that in spite of slight forwardness, the midrange of the current setup sounds 'right'.

The area where the Quicksilivers and Cary really shine is soundstaging. It's a big bold sound -- and something I had not experienced yet. With the Superamp and Apollos I could understand the concept of 'bloom'. With this setup it's not about bloom -- it's about 'explode'.

Perfect.

For now.

[leok]

deang,

ComCast welcomed us to their internet service by providing two days of no hassle total disconnect. I noticed as I left the house this AM that the modem has re-linked. So, this eve I can respond with more observations. The xover looks great. Give those caps some time to break in. The high stuff should smooth out more over 100 hours or so of operation.

leok

[Deang]

I hope you're right about the break in. I need more bass, and the best way to get it is to have that midrange and treble relax a little. I already removed the spikes from the RF-7's to get some coupling to the floor, and moved them back almost another foot.

I'm enjoying the clarity though, and it's so clean -- it's easy to ignore the forwardness. Last night I was really noticing the lack of congestion during complex passages. Everything just hops along. Sweet.

[leok]

deang,

You've spent some time listening to Cornwalls while the RF-7s were down. I spent 2 Hours at Chris Robinson's house listening to heritage designs and boy, did the RF-7s sound thin.

I've learned a couple of things. First, I think the RF-7s still have a high end that has an edge on the 3-ways. Second, floor reflections can kill a lot of RF-7 bass.

On the second issue: Get two similar furniture cushions (overstuffed chair or sofa cushions). Place the cushions, standing up (you'll probably have to lean them against boxes or something to hold them) halfway, directly between your listening position and each speaker. This provides a barrier that blocks floor reflections from the two woofers. You should still be able to see both woofers, over the cushions, as you sit and listem. If that helps, one of your problems is Allison Suck-Out, which I described toward the end of the thread about Chris's place.

I'm getting some bass absorbtion foam devices to accomplish the same thing, or better, without stealing cushions. I'll let you know if they work as well, or hopefully better. I do find that the cushion method is very successful in my setup. This is a problem with woofers that are off the floor .. probably affects my Fortes as well at some higher frequencies.

Another thing you should really try, especially with all that pp power, is: Get 2 8-ohm 5-watt resistors (closest value to 8 between 6.8 and 10 Ohms is fine). Connect your RF-7s to the 4-Ohm amp out. Connect the resistors in parallel. This is very easy engineering logic .. not a trick. Just do it.

Do these things and tell me how it all works out.

leok

[Deang]

I don't think I'm experiencing the "suck out" phenonmena in that room upstairs. The bass is there, the treble is just tipped up a little. When I got home from work tonight, I thought I sensed a more rounded nature to the sound. I'll continue to abuse the RF-7's until they fall in line. At any rate, lot's of carpet, and I'm a piddly 8 feet away. I suppose I'll set some cushions up just to see what the effect is (as long as no one is looking:)

No, The RF-7 is not a Cornwall or K-horn. With Heritage you get a wonderful BIG sound. With the RF-7's, you get velvet intimacy. When I'm in need of therapy, I go upstairs. I still think at the very low volume levels -- the Cornwalls and RF-7's sound very similiar. At higher levels, the RF-7's are rock steady, and the treble is gorgeous -- not an adjective that comes to mind when I'm listening to the Cornwalls.

Man, you got a thing for resistors.

Because it's you -- I'll do it.

I guess I just connect positive and negative together with the resistor at the speaker binding posts? Yeesh, that's wierd.

[NOSValves]

Dean,

I'm not sure that is what he means. I would wait for more clarity before trying that !! I'm curios as to what he means in parallel . Parallel with what ?

Craig

[leok]

deang,

Ys .. definately at 8' . so put the baffles at 4'. Carpet won't stop lf reflections. A baffle will deflect them.

The resistor: In parallel with the speaker .. between the pos and neg out. You're driving an 8 ohm speaker and an 8 ohm resistor in parallel. That means your driving 4 Ohms. With the resistor in, the amp sees a more resistive and uniform load. The speaker sees better damping. The resistor damps reflections and resonances.

I have a 33 Ohm inmy Moondogs (which are configured for 8 Ohms out. The difference is very impresive.

Also on reflections, I forgot one thing. Place a small pillow at the base (in the front) of each speaker. This ay be a point of re-radiation at low freq. just a precaution. You can do it when nobody's looking

I think you'll like all this. You really should try it.

leok

[leok]

Oh yes .. I use the 4 ohm tap and 8 ohm resistor on my pp design. Just like I'm suggesting for you. No going back.

leok

[leok]

deang,

I disagree on several points with Mark.

You will not cut your power in half, but by the expected 1/square root of 2 (0.707 x 8 ohm power) that would be expected when using the 4 instead of 8 ohm outputs. With 60 x 0.707 = 42 watts avail you can still do structural damage to your house with those RF-7s.

There will be no dynamic loss .. there is no technical justification for that comment .. except of course for the loss in the dynamics that were a result of resonances and impedance peaks that are reduced by the resistor.

I believe you will have plenty of power and dynamics. Most likely, your perception of both will improve because of the reduced distortion.

leok

[AnalOg]

I by no means have any electrical background so I'm trying to understand this. By putting the resistors in parallel are you in essence turning the speaker into a 4 ohm speaker as appose to a 8 ohm speaker?

thankx

Tom

[leok]

Mark,

I should have thought more carefully before I wrote. My concern is Dean is sitting on the fence here, and threat of amplitude or dynamic loss could prevent him from trying something I believe is very beneficial, esp. with those RF-7s. Having done this with pp and SET amplifiers and 5 different output tubes between them, with the RF-7s, my experience is that the sound is cleaner and can be driven much louder comfortably because resonances are damped.

As to power .. I think I was wrong, and the power available to the speakers will be halved, as you said.

Mark, I took your posts as intended, but my response, focused more toward Dean, was off in tone. Sorry.

leok

[Dave Harris]

I've been reading about some other people's experience with the RF-7's comparing them to mine. Mine are exactly a week old, and therefore, probably have less than 40 hours on them.

Initially, I was very pleased. I am not a huge fan of booming bass, and I love a clean mid and high end, and these things dont disappoint. But, over the last day or two, I just can't help feel that I am really missing some bass. The bass that there is seems solid and quick, but there doesn't seem to be enough of it.

I was listening to Kid Rock's "Cowboy" and quick drum kicks right before "...Kid Rock and you can call me Tex..." just seemed shallow whereas my old PSB's would hit you in the gut (although a bit too boomy at high volumes). I have even had to turn my sub up close to max and the crossover up to about 80.

Am I being impatient? Do speakers really have a break-in period or is that bogus? I would really like to like these speakers, but I am wondering if I should have gone with the Soliloquy 6.2 or NHT 3.3?

Dave

[Deang]

Sure is nice seeing some of the top brains of the outfit handling a slight difference of opinion in such an intelligent and calm manner. Of course, a technical slug fest between you two would have been pure bliss.

Well, from the day I received the Quicksilvers, I've had them on the 4 ohm taps of the transformer because of the known dips in the RF-7's impedance. I had the RF-7's wired this way with the Apollos, and didn't see any reason to change this on the Quicksilvers.

A little of topic here, but not really I guess -- the literature with the amps say they put out 60 watts whether on the 4 ohm or 8 ohm taps. I don't really understand how this can be possible.

Just think, going to 4 ohms halves my power. If I wire them in triode I halve them again. Before I know it, I'll have 8 EL-34 tubes giving me less than 20 watts. Yeesh. I actually like the Ultralinear sound with my music quite a bit, so I'll be leaving them this way for a time.

As far as adding the resistor goes, I think I'll give it a try. As far as non-flat response goes -- ain't many of us getting that anyway. Between room acoustics, and running tube amps on speakers with less than ideal impedance curves -- who knows what the real response looks like. Hey, if it sounds good -- who cares?

One thing Leo. If you look at the impedance curve of the RF-7, and average the whole thing out -- it's really a 6 ohm nominal speaker. Based on this, what do you think about me trying 12 ohm resistors instead? The idea is to get a 4 ohm load at the amps outputs, correct?

[Deang]

Dave,

You gotta fill us in.

Equipment

Room Size

Placement

Etc.

[leok]

That would be fine tuning and I don't know. Go for 12 and see what happens. If you like it and want more .. try 8. I wouldn't go lower than that.

leok

[Dave Harris]

Sorry, I've posted a lot on here lately, and I keep mentioning my setup - but forgot this time.

The RF-7's are my stereo pair as well as the fronts in my HT (rarely used as HT though - girlfriend says "surround sound is scary.") The whole thing is powered by a Yamaha integrated amp (DSP-A-1092). I have a Jolida tube amp coming.

The equipment is in my city loft which has a lot of dead air space. Floor is 20x32 and ceilings are 13'6". Speakers were nearly 2 feet from back wall but I now have them back to about 8 to 10 inches. Equipment is set up on short wall - opposite wall is exposed brick - adjacent wall comprised of two very large (6 foot by 11 foot) windows. Room also has a lot of soft furnishings. Using very ordinary 16 gauge Monster cable in 2 20 foot lengths.

And my kitty's name is "Mittens."

Regards,

Dave

[NOSValves]

Mark,

Gald you covered that I tried to tell Old Dean the same thing way back when and I think he thought I was nuts. Tube amps have seperate taps for each independance and put out rated power to each tap with the proper load. SS amp don't have this feature as far as I know !

Craig

[leok]

Dave,

deang and I seem to be the most vocal and experimental in our involvements with the RF-7s. We've both upgraded crossover components and damped the horns (I think deang has anyway). This behavior is not unusual for members of this forum. Many speakers, regardless of vintage, have been tweaked. In any event, most of us like our various Klipsch speakers because we like the fundamental designs and implementations.

I listen primarily to classical music. deang listens to some other kinds of music .. some of which I listen to too.

The RF-7 is an approach that Klipsch (even Paul himself) has tried on several occasions. It is a 2-way rather than 3-way. For now, I'd say, that is the basic feature of the approach. I personally like 2 way speakers because I believe (and I know I don't KNOW) they have a cleaner sound. I like having a single speaker (the RF-7 horn) cover from 20KHz down as far as possible. I think it provides the most believeable presentations of instrument timbres and makes for a very stable stereo image.

The RF-7 doesn't have horn lower midrange and bass. To do so it would have had to be much larger and more expensive. The ported bass it does have, and the vertical arangement of the two woofers are a compromise. But I think, if you work with the compromise the speaker is hard to beat (I haven't found anything that I prefer*).

My house is small, possibly like your application. A complete horn implementation, like the La Scala is attractive, but it is large and I doubt the top is as clean. I've chosen, for now, to optimise the RF-7. That has included use of an amplifier that has low distortion at low power (required for all Klipsch speakers), some minor electronic and mechanical tweaks, and the floor reflection baffles I mentioned at the start of this thread. You might as well try it too.

The Yamaha amp (I think I have that right) is most likely an issue (distortion at low power makes all Klipsch speakers sound harsh and thin). The Yamaha is probably not real god at low power. The Jolidas should be better, but I have no experience with them.

Should you have purchased other speakers? Maybe, but if I knew which ones, I would have them and I wouldn't be here.

* Heritage models offer a different approach and different sound. They are fabulous speakers. The dynamics and power are beyond what the RF-7s can do, but much more beyond what anything else can do. I don't think they are as detailed in the upper midrange and up, as the RF-7s. But the power and frequency response its tremendous.

[Deang]

Bumped for mOOn -- who wants to know more about crossover changes.

[m00n]

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On 3/8/2003 2:17:12 AM DeanG wrote:

Bumped for mOOn -- who wants to know more about crossover changes.

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Uh.. Thanks man for making my brain work at incredible levels before I have had my Saturday morning coffee yet.

What you all said: "Very knowledgable input"

What m00n heard: "blah blah blah blah blah"

That was like trying to teach trig to a baby.

I will re-read it all as it will come handy I am sure. I didn't even realize there were mods for RF7s... I am very interested in this as I would like to warm up mine a bit.