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Modifying the Klipsch RP-600M


rdale
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I've had a pair of Klipsch RP-600Ms for about a year and a half. I drive them with a 5 watt per channel single ended EL84 based Glow Amp One. In the small room I use them in, the Glow amp works pretty well. The RP-600Ms are great fun to listen to, and there are loads of mostly positive reviews out on the web. The better the equipment you drive them with the better they sound - they are very revealing of the system that they're connected to.

I use Atacam SE28 stands which are higher than usual. The measurements of the Klipsch give the flattest responses when it is measured at a point between the tweeter and the bass/midrange unit, otherwise you can get a dip between 1 and 2 khz. My higher stands place my ears at about there. When I measured the in room response with REW they were pretty flat between 1-2 khz. I also added IsoAcoustics Gaia III footers which improved the sound and made the stands a bit higher again:

atacam_se28_stands.thumb.jpg.e26992b83ab54094c0c54bfd2ae0a677.jpg

The only thing that I thought the stock RP-600M lacks is imaging, and the image never quite comes away from the speaker.

I watched some videos about modifying the RP-600M by Danny Richie from GR-Research:

Discussion on Audio Circle here:

https://www.audiocircle.com/index.php?topic=166535.0

It was really interesting to hear what Danny thought was wrong with the Klipschs and what could be improved. I felt his mods were a bit drastic, redesigning the crossover, and adding extra damping to the insides of the speaker. Then I found this discussion about modifying the Klipsch RP160 which is very similar to the RP-600M, it even has the same crossover:

https://community.klipsch.com/index.php?/topic/163667-how-to-make-the-rp-160m-come-alive/

Tweaker256 describes some modifications to both the bass and treble sides of the crossover. He says you can start off with a simple mod and keep the original PCB, and then completely change the board if the replacement capacitors are too big.

That sounded like a fun thing to try, and I ordered the caps and resistors from HiFi Collective. I decided to just change the treble side of the crossover at first, and ordered two 3.9 uF Janzten Cross Caps, and two 0.1 mF Audyn True Copper caps as bypass caps. And a pair of Mills 12 watt 9.1 ohm resistors.

While I waited for the caps and resistors to arrive, I tried rewiring the internal cabling with Duelund. I had intended to use Duelund DCA16GA for the bass side, and DCA20GA for the treble, but the 16 gauge was too thick to fit in the holes in the PCB. Here is a picture of the original Klipsch cable and the two Duelund sizes:

klipsch_cables.thumb.jpg.b3a1b638a8028ecda95c78787f5e4401.jpg

It looks as though the Klipsch cable is about 18 guage. I decided to double up two Duelund DCA20GA lengths for the bass side, and use single DCA20GAs for the treble side. Here is the bass cabling:

bass_cabling.thumb.jpg.ed7f3719541d382e694c34e558050705.jpg

The original Klipsch cables were wrapped in foam, and so I use bubble wrap instead. I used the original clips, rather than soldering the cable directly to the drive units. When I upgraded the crossovers I changed my mind about that and got rid of all the original clips and soldered everything directly.

Just changing the internal wiring did improve things slightly, and I felt the bass had a bit more drive. 

So I listened to the upgraded cabling for a week or two, and finally the caps arrived. It wasn’t too difficult to add them, I piggy backed the Audyn True Copper bypass caps on top of the Janztens:

rp600m_crossovers.thumb.jpg.3ec222f2cd0d4714a1fcd1cae5ba9bf2.jpg

The original cheapo components are at the bottom of the pic.

I put the Klipschs back together, and at first they sounded crap! But this is the wonderful world of capacitor rolling where you often have to wait 100 hours to get anywhere. After about a day, they got going and after two or three days they were definitely starting to sound better that the stock RP-600Ms. I've been running them for a week and a half or so now, and they really sound like different speakers - the imaging has improved and the treble has more refinement. I recently changed my mains conditioner from an old EsoPower to an IsoTek EV03 Sirius and that improved the dynamics and imaging of the system still further.

I would class the current mods as a 100% success, and I'm really over the moon with the sound. I might decide to attempt further mods to the bass side of the crossover, but I'm not in a rush.

Edited by rdale
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Good work. I've completed rebuilt/ upgraded two sets of speaker crossovers myself and it is a) fun b) satisfying and c) very rewarding sonically.

Your rewiring is the one thing I didn't do but I've got a plan to do that soon. 

Nice choice of caps too.

I also agree with your plan to modify the top end first, that's exactly what I did. Get used to changes one at a time :)

Edited by Psilonaught
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17 minutes ago, Psilonaught said:

Good work. I've completed rebuilt/ upgraded two sets of speaker crossovers myself and it is a) fun b) satisfying and c) very rewarding sonically.

Your rewiring is the one thing I didn't do but I've got a plan to do that soon. 

Nice choice of caps too.

I also agree with your plan to modify the top end first, that's exactly what I did. Get used to changes one at a time :)

Thanks. I used Duelund because I use it for both my interconnects and speaker cables, and so I’ve got Duelund all the way with the Klipschs (and Tandy LX5 speakers that I also did recently).

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  • 2 months later...

I recently upgraded the Klipsch binding posts to KLE Classic Harmony binding posts. They were pretty easy to fit, I just drilled out the holes in the plastic back plate a bit. There are two pairs each side, and so the speakers can still be biwired, although I don't think I'll bother. The have a special washer over the bare wire connections, and maybe two bare wire connections for bass and treble are better than just one. Here is what they look like:

kle_binding_posts.thumb.jpg.e65748d9681a4c1b0c61bef1b8a366cc.jpg

I also added a pair of the new 0.01 uF Duelund JDM silver foil bypass caps to a 43 uF electrolytic in the LF side of the crossover:

duelund_bypass_cap.thumb.jpg.cfb2c98b60429103b09c6bd91a99c670.jpg

Again there were easy to fit. I drilled holes in the PCB with a set of small drills I got really cheap on Amazon:

https://www.amazon.co.uk/gp/product/B07F7QCNJ1/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

I did a lot of reading about bypass caps, and the consensus is that the bypass cap should be about 100th of the value of the main cap. So with the 43 uF cap in the crossover, that should have equated to about 0.43 uF which is a lot more that the value of the 0.01 uF Duelunds I fitted.  There is one company that has ignored this rule of thumb, and that is JBL who have bypassed 40 uF capss with 0.01 uF ones on some of their studio monitors. I only did the upgrades a couple of weeks ago, and so if the caps are having any effect they will still be settling in.

I don't think this round of changes has made as much difference as when I upgraded the treble part of the crossover and internal wiring, but it is still very worthwhile. I would say the sound is more dynamic with tighter bass (making the RP600Ms more dynamic is quite a thing). The imaging has improved again, and maybe it has improved further in the last two weeks. 

I now have a pair of speakers which is very dynamic and yet refined, while being easy to drive with my 5 watt per channel single ended Glow Amp One valve amp. The treble upgrade cost about 75 pounds, and the latest binding posts and bypass cap upgrades were about another 225 pounds or so. So I've spent 300 pounds upgrading a pair of speaker which only cost just over 600 pounds. Is that like making a silk purse out of a sows ear? I don't think it is because I haven't revealed any weaknesses in the sound of the Klipschs, they are still very much the same speaker but substantially improved. So I'm pretty happy with how it has turned out. I may visit the bypass caps in the future and try higher values, but there is no rush with the sound as it currently is.

Edited by rdale
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SO, no dampening of the units yet? (I saw the improvement articles too)

Good to hear Klipsch getting beyond their Horn image-not MY view, but, a bit akin to 'Citroen with their weird suspension' image (it isn't-just lovely to ride in!)

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6 minutes ago, Hornucopia said:

SO, no dampening of the units yet? (I saw the improvement articles too)

Good to hear Klipsch getting beyond their Horn image-not MY view, but, a bit akin to 'Citroen with their weird suspension' image (it isn't-just lovely to ride in!)

I’ve only touched the electrical side so far.

I could add some damping on the units. The thing I’m most tempted to do is to put some rolled up bubble wrap in the speakers. I tried that with my Tandy LX5s and they sound great with it. 

I’m not sure that the cabinets are much of a problem, even though they are a bit cheap and don’t have much damping. So I think it is possible to just end up making the speakers sound different or worse with more damping.

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Mr Boston Audiophile puts dampening material on the woofer frame.

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On 22/08/2020 at 10:53, Hornucopia said:

Mr Boston Audiophile puts dampening material on the woofer frame.

Thanks for that. I’ve just looked at some of his videos including the one about damping the horns. The Dynamat Xtreme he uses is only 22 euros for two 25 cm square sheets and so I think I might try that on the bass horn. The guy whose crossover mods I copied damped the bass horn, and he seems to know what he is doing. The treble waveguide on the RP600M treble horn is made of rubbery material and so I don’t think it makes sense to damp anything there.

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  • 2 weeks later...

It's always a good learning experience to try such modifications in my book.  I've tried many of the high end capacitor brands in different DIY amplifier builds including the Duelund Cast Copper.

The Duelund JDM Silver bypass caps are a bit of a bargain imho if bypassing output capacitors I've been very impressed with the results of doing so myself.  However I haven't used it in crossover.

Fwiw I also use Duelund DCA wire for speaker cable, be mindful that there are more than a few reports online saying it takes around100hrs of use to come on song. I certainly thought performance improved given a week or two of play time myself.

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11 hours ago, Fatmarley said:

Have you seen this?

I preferred the standard version, and it seems a lot of others do too.

I couldn’t hear much difference on an iPad mini. It would be nice to have a real life bake-off between the stock RP600-M and the mods I’ve done, and the GR-Research mods. Record Day Ron doesn’t actually like the RP600-M all that much and spends the end of the video suggesting alternative speakers. 

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10 hours ago, JamieMcC said:

It's always a good learning experience to try such modifications in my book.  I've tried many of the high end capacitor brands in different DIY amplifier builds including the Duelund Cast Copper.

The Duelund JDM Silver bypass caps are a bit of a bargain imho if bypassing output capacitors I've been very impressed with the results of doing so myself.  However I haven't used it in crossover.

Fwiw I also use Duelund DCA wire for speaker cable, be mindful that there are more than a few reports online saying it takes around100hrs of use to come on song. I certainly thought performance improved given a week or two of play time myself.

I agree about the learning experience, and even if a particular change doesn’t make much difference, you still learn something.


Everything Duelund needs plenty of breakin time, and the Duelund bypass caps and KLE binding posts need 100-200 hours to burn in, and they’ve certainly had less than 200 hours so far. I need to give them a week or two more. I would have to temporarily unsolder the bypass caps perhaps to determine what difference they made, and I’m not sure if that’s worth doing.

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39 minutes ago, rdale said:

I couldn’t hear much difference on an iPad mini. It would be nice to have a real life bake-off between the stock RP600-M and the mods I’ve done, and the GR-Research mods. Record Day Ron doesn’t actually like the RP600-M all that much and spends the end of the video suggesting alternative speakers. 

I couldn't hear much difference either TBH, but the standard ones just sounded a bit more alive. The modified ones were a touch dull. As you say, it would be interesting to hear them in the flesh. The results could be quite different.

Thinking about it, whenever I've listened to music on YouTube and compared to the digital version on my PC, the YouTube one always sounded a bit dull.

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  • 8 months later...
On 23/08/2020 at 11:46, rdale said:

Thanks for that. I’ve just looked at some of his videos including the one about damping the horns. The Dynamat Xtreme he uses is only 22 euros for two 25 cm square sheets and so I think I might try that on the bass horn. The guy whose crossover mods I copied damped the bass horn, and he seems to know what he is doing. The treble waveguide on the RP600M treble horn is made of rubbery material and so I don’t think it makes sense to damp anything there.

I finally got round to doing this and damped the bass horn with Xtreme Dynamat. Here is a horn treated and ready to go back inside the speaker:

klipsch_horn_treated.thumb.jpg.be5051d1a59692ac0889c6c1365a8580.jpg

The Dynamat was easy to work with and after applying the damping the horn is pretty dead. I didn't even need to remove the Klipschs from their stands, and so for an hour and a half's work and about 30 pounds I think I've got a worthwhile improvement in sound. I need to listen for another week or two to decide exactly what has changed.

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