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Fabulous RF-7 modification!


Joepie

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For all Klipsch RF-7 loudspeaker owners, I would like to share a fine and easy ‘do it your selves’ modification that brings your RF-7 loudspeakers to the next level! This concerns a modification of the speaker’s horn and reduces a strain that many people continue to experience in the higher frequencies. Other people call this ‘stress’, ‘harshness’ or ‘listening fatigue’. Again other people refer to this as ‘sibilance’. Well, whatever we call it; to me there it was clear that there was some harshness in the highs that caused me a degree of tiredness after a period of listening to the RF-7’s.

Although it always remained a sheer pleasure to listen to these fantastic loudspeakers, I kept thinking what could cause this harshness in the highs. And whatever the system I used in the front, it always kept coming back, so I concluded that it had to be in the speakers themselves. A while ago I already applied the DeanG filter, which was absolutely a wonderful step in the right direction, but still… I kept hearing some harshness…

Then I considered the mechanical properties of the horn and recently I concluded that there must be a resonance from its housing. When knocking on the tweeter enclosure, I judged that the horn had too much of an own resonating frequency which surely would be excited by the vibrations coming from the tweeter it selves. Also when feeling the tweeter enclosure with the hand whilst playing music, I clearly felt structure vibration.

So what to do about it? Build a completely new enclosure from solid wood was one option, but surely not an easy one as it will require a time consuming and very precise handwork. So something else should be possible to test this. And then I found out about the option to dampen vibrations with the use of Bitumex sheets, a technique usually applied in cars. This would be a great thing to try. It would be relatively easy to apply and without risks I could know the effect. So I bought two sheets of 4mm Bitumex FG4SK for the minimal cost of 16€ including the postage cost (I would not advise 2 or 3 mm as it is the mass that makes the difference in this elastic system). Applied this and arrived in a different world, the next level of performance for the RF-7, a ‘must do’ mod for every RF-7 owner I would say now. Listening fatigue is gone, depth improved, focus improved and the highs finally sound smooth now! Initially it feels as if there are fewer highs, and as a matter of fact that is correct, the distortion caused by the resonance of the horn is just gone now. Try this and listen. Your next pleasure is there! And that for only a few bucks! Just make sure you fit the Bitumex at the outer side of the tweeter, not the inside of the horn, which would destroy the horn acoustic properties [:D]

At YouTube I have placed a mini movie how this is done (See

). Try it and let me know your experience. I would be happy to hear your story. Success and I wish you added listening pleasure in the next level of RF-7 potential.
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Sound deadener also comes spray able for cars, although spray in bed liner and even undercoating does similar things. A can of undercoating is relatively cheap and would be as easy as spray paint. Just an idea.

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Thanks for the tip. That deadener spray could indeed be interesting too. Do you know if that easily sprays to a thick layer like the 4 mm Bitumex? And will it be equally heavy? And, just to know, is it removable in case desired for some reason? I will check around to get to know that sticky stuff :-)

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I used a nondrying modeling clay to dampen the horns in some Forte I's and Tangent 400's about one pound per speaker. I thought it was an improvement reduced listing fatigue and increased clarity. This was something my wife could pick up from a discount department store because I dislike shopping. About $30 for all 4 speakers. i don't know how hard it would be to remove.

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Thanks! This sounds as a good option too, with the ability to add a good amount of mass. My concern would be whether the modeling clay would be sticky enough, but apparently that went well. Have you ever checked whether it stayed well put on the horn?

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I expect that the real question is not how hard it is to get off but how well it will stay in place? Constrained layer damping materials often have automotive grade adhesives are very compact easy to use and very effective at damping. Look for products like Dynamat. Best regards Moray James.

Please Note: I was referring to modeling clay

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I expect that the real question is not how hard it is to get off but how well it will stay in place? Constrained layer damping materials often have automotive grade adhesives are very compact easy to use and very effective at damping. Look for products like Dynamat. Best regards Moray James.

I "sound proofed" few cars and used
different materials. There is only one condition for butyl based materials-no
oily substances on the panels.

Even if panels are bit dusty and dirty it still will stick
and stay there forever. Heat up applied deadener
after application a bit with heat gun and deader adhesive will melt through the
dust and stick to any surface.


Avoid air bubbles and oily surfaces (can be cleaned with
alcohol) and deadener will never pill away.


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Thanks! This sounds as a good option too, with the ability to add a good amount of mass. My concern would be whether the modeling clay would be sticky enough, but apparently that went well. Have you ever checked whether it stayed well put on the horn?

I have had the drivers out lately, the clay is holding in place and is still sticky. I'm sure there is better products for this application. The clay works for me mostly because my wife could pick it up with out having to search too hard.

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I did this about a year and a half ago. I did all of my RF-7's and my RS-7's. I need to do my RB-75's now. I used a thick thermal type of tape that worked great. It does help quite a bit IMO. Good video btw.

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  • 1 month later...

Joepie, that is quite possibly one of the finest self-made instructional videos I've seen on youtube to date. clap.gif Very nice!

Regarding the harshness from your RF-7's however, it's not coming from your horns, if how you listen to your speakers is as placed as you have shown in the video.

From what I can see, they aren't toe'd-in enough, and are thus reflecting off the nearby side wall....a lot.

The toe angle keeps the horn off the wall, which is a pretty big deal sound-wise.

"Harsh" would be the last word I would use to describe the sound of an RF-7. Many others would agree.

Just a suggestion.

Not that the bitumex isn't a good idea none the less, it just won't solve the acoustic geometry problems resulting from improper placement.

In the diagram below (something I grabbed from a previous thread), if your ears are situated in the pink zone, you'll hear a mix of direct and reflected sound. It will sound "honky" or "harsh".

This is at 45 degrees of toe. With even less angle , the pink area (reflected sound field) can grow to consume the entire listening area, which is bad sound.

LSPosition1002.jpg

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The harshness comes from the cones, there is some breakup and ringing around the crossover region. The woofers were modified in the later reference speakers to deal with it. Some don't notice it, it drives others nuts. When it's gone, it's really noticeable.

http://infinitysystems.com/tl_files/content_resources/infinity/white%20papers/cmmd.pdf

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The harshness comes from the cones, there is some breakup and ringing around the crossover region.

Why would Klipsch knowingly spec a filter network that passes a signal into the driver's break-up region...on flag-ship model none the less?

Why would anyone intentionally do that in any design if it could be avoided...like say during the initial design stage of a significant product? [:^)]

I do not doubt the merit of of the paper you link to in relation to the discussion, but for 9 outta 10 times, when someone is complaining of harshness or honkiness form horns, it's either from air leaks, bad aim, bad source, or not enough bass.

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your kidding right? never heard the experssion "good enough so leave it alone?" start a company ant tell me you would not consider doing the same thing. companies do lots of stupid things every day and Klipsch is no exception. just look what they did with the CF series because hard line Heratige heads did not like the sound. Not that you list of possibilities is not valid and well worth looking into but companies do the darndest things. Best regards Moray James

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"Why would Klipsch knowingly spec a filter network that passes a signal into the driver's break-up region...on flag-ship model none the less?"

Well, there is a story behind that, and I was asked to be quiet about it. After hearing my modification, I was asked by a Klipsch employee how I got rid of the ringing. I took a modified filter to Klipsch headquarters a few months later where they ran a transfer function analysis on it. The Infinity white paper relates to the cone material, and explains why they modified their drivers.

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Many very good drivers, particularly ones that don't self damp and are very hard (usually very good on lower level detail mind you) have serious resonance problems. You typically have three choices,

  1. dampen the driver by design (possibly lowering the detail) - requires driver redesign
  2. keep the driver out of that particular frequency range - usually requires more costly drivers and crossover components since you have to lower the crossover point to cover the frequency not covered by the lower frequency driver
  3. electronically attach it with components to combat the resonance area - costs a lot in components and possibly efficiency along with the more costly drivers in case of a hole in the response

If you look at Madisound and Parts Express, you will see most higher end drivers have a nasty resonance at the top of their range. These are good drivers but by many are not good sounding for DIY because of the required interface components and cost involved in making them sound good. OTOH drivers which are not as hard and are more self damped will usually sound warmer, slightly less detail, and are usually much easier to work with.

Disclaimer: the above is not where you go when you are talking about cheap and poorly made drivers.

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  • 3 weeks later...

Hi, Great exchange of knowledge!

@ Quiet_Hollow : Good you consider this positioning option. It is a point that I am aware of too. However I am positioned in the blue area of your triangle, whereas the distance from me to the loudspeakers is even less then the distance between the loudspeakers themselves. I like this position due to great soundstage, direction precision and great dynamics :-) But moreover: I do not hear any harshnesh left after the DeanG mod and then the bitumex. I am really happy at current. But also further in my room I am hardly troubled by the walls as there is plenty stuff on the wall catching the indirect waves. Anyhow, good to take this in consideration.

@ Vital and UH1dg337 : Thanks for sharing your good experiences too. It is good to see such confirmation and I am sure it will help other people to consider this.

@ AletheiaAudio : Hi Dean, Interesting about the breakup. When I modded the filter according to your partslist and specs, did I take my cone also away from the breakup frequency? Is that what happens with the DeanG mod? Great knowledge anyhow and thanks for the document showing all differences.

@ pzannucci: I guess we can hear the resonance / ringing frequency when ticking on the woofer cone material. It does sound relatively high indeed due to the stiffness. Anyhow I am always very happy with this stiffness indeed as there is lots of detail in the bass. All wave shapes seem to present very well. Fast stuff!

There is just one thing that remains to puzzle me as a next mod. Although my RF-7 speakers do sound very smooth now (so all harshness gone), I do still hear some slight colouring. I suspect this is due to the absence of a phase plug in the tweeter. Now we know Klipsch has introduced that in several other loudspeakers, but this is missing for the RF-7 right? I have heard the effect on the RB51 but also the Palladium series use this. I have the feeling that this could perhaps also benefit the RF-7. Does anyone know, would there be any option to make an own mod in order to play around and test such phase plug in the RF-7 tweeter? Did anyone try already with RF-7? I guess this could also have other side effects that are perhaps not desirable, but I do not yet know what.

Anyhow, I have the loudspeakers now since 2009, and each day I start to love them more, also after hearing quite some other stuff around. Last week I bought the new Pat Metheny CD called "Tap". What a revelation through the RF-7! Fantastic dynamics and musical adventure.

All following this posts, have a great day! [8]

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