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GR Research Klipsch RP-600M Upgrade Review (speaker)

Rate this speaker mod:

  • 1. Poor (headless panther)

    Votes: 7 4.0%
  • 2. Not terrible (postman panther)

    Votes: 39 22.2%
  • 3. Fine (happy panther

    Votes: 107 60.8%
  • 4. Great (golfing panther)

    Votes: 23 13.1%

  • Total voters
    176

amirm

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This is a review of a Klipsch RP-600M which has been upgraded to a new crossover, binding posts and "No Rez" by GR Research. The kit costs US $244.
GR Research Klipsch RP-600M Mod New Crossover review speaker.jpg


OK, so there is nothing externally which is different. :) I can't open the unit to show the different bits but here is the back with new binding posts (two are in parallel):
GR Research Klipsch RP-600M Mod New Crossover review no-res tube connector speaker.jpg


I performed all of my testing using the standard binding post.

My old review of RP-600M did not have the latest measurements so what you see is me adding those measurements.

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

Reference axis is the tweeter.

Klipsch RP600M With GR Research Mods Measurements
I am going to contrast the stock version with the new. The former will always be on the left. Let's start with the all important spin/frequency response:

GR Research Klipsch RP-600M Mod New Crossover frequency response Measurements.png


The stock version is fatally flawed in crossover region with that large hole. GR Mod uses a first order (?) filter to make the two drivers roll off slower and thereby, filling that whole. This gives us a much more flat on-axis response. There is a cost though in sensitivity which drops by 3 or so dB.

We can see the correction better in near-field measurement:
GR Research Klipsch RP-600M Mod New Crossover Driver Near-field frequency response Measurements.png


There were to port/cabinet resonances in the stock version which are gone now. Whether this is due to padding being different, I can't tell. But it is certainly welcome.

The fix naturally improves the early window response:
GR Research Klipsch RP-600M Mod New Crossover Early Window frequency response Measurements.png


And with it, predicted in-room response:
GR Research Klipsch RP-600M Mod New Crossover Predicted-in-room frequency response Measurements.png


So very good job there. Let's now look at distortion. This was tricky as I had to match levels. Doing so with speakers of different response is non-trivial but I got close:

GR Research Klipsch RP-600M Mod New Crossover Distortion 86 dB relative Measurements.png


At 86 dBSPL above, it is hard to see much of a difference. Going up to 96 dB gives us more data:

GR Research Klipsch RP-600M Mod New Crossover Distortion 96 dB relative Measurements.png


Stock unit has that broad distortion hump. That is much reduced with the mod but now there is a sharp resonance. There is some reduction of distortion at the far side of the spectrum with the mod.

Company makes a lot of hay out of CSD waterfalls so let's look at that:
GR Research Klipsch RP-600M Mod New Crossover CSD Waterfall Measurements.png


Seems like some reduction in resonances. The peak in the stock speaker around 800 Hz is gone which results in less ringing there.

Impedance and phase plots also show similar improvement:
GR Research Klipsch RP-600M Mod New Crossover Impedance and Phase Measurements.png


Impedance is also brought up a bit which is nice.

EDIT: I managed top compute the directivity of the original version and updated the three graphs below.

I was interested to see the impact on directivity. The impact horizontally is due to filling in the hole:

GR Research Klipsch RP-600M Mod New Crossover horizontal beam width Measurements.png

GR Research Klipsch RP-600M Mod New Crossover horizontal directivity Measurements.png


The (general) narrower directivity means you have a less wide sweet spot and more narrow/less diffused imaging.

What improvement we see there, we give up in vertical dimension:
GR Research Klipsch RP-600M Mod New Crossover Vertical directivity Measurements.png


In the stock version we have the classic "dual eye" pattern. But we see broad tearing of the response with the mod. The impact of this is hard to analyze and at any rate, we are less sensitive to vertical directivity error than horizontal. So not a bad trade off.

Listening Tests
I started listening to the stock RP-600M and immediately noticed its brightness and lack of spectrum in mid frequencies. I switched it out for the modded version and improvement was substantial. The sound was tonally very balanced now. I thought the highs were a little unnatural so switched out the speaker for Revel M105. There was too little bass in that smaller speaker to compete so I put it aside and put on the Revel M16. The Revel projected a much larger/diffused sound which I much preferred to the RP-600M. I switched back to it and the vocals seemed to shrink to the middle of the RP-600M cone. This is backed by the directivity plot (which I had not seen at the time).

The dynamics were a bit more limited with the mod due to its lower sensitivity. And by this I mean it started to get distorted a bit less than the stock speaker did. Impact was in bass frequencies which became progressively ugly. That said, this was happening at fairly high playback level and with one speaker. So as a practical matter it should be fine if you have enough amplification power.

Conclusions
The flaw in stock RP-600M is so obvious and so is the solution. It was reassuring to see GR Research correcting the response and smartly using lower order filters as to keep the cost down. The difference is dramatic. I can't listen to the stock version. But with the mod, the combination was definitely a contender. You lose some sensitivity so better have a good sized amplifier. The narrow directivity is not to my taste but may be to yours.

Overall, this is a job well done by GR Research and I am going to recommend it to owners if they are not inclined to use my software EQ fix.

Video review also posted with a bit of bonus information:

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

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thewas

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Overall a good mod. I wonder how a purely EQ adjustment would fair; the vertical performance of this mod is a bit worse than stock, so using this mod in the near-field may not be best.
Yes, due to the less steep slope the vertical directivity and distortion suffers, so I would rather equalise it or just buy the successor generation as Klipsch corrected that dip there:


 
Last edited:

fragzone

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Why would anybody in his right mind buy a Klipsch in the first place? Those small ones are just terrible and big ones sound "interesting" for first 10 minutes.
Zero fidelity says he would prefer the rp600m (and triangle bro 3) over the Elac dbr 62 reference because it is more engaging and livelier.
 

dfuller

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I guess it makes sense if you already own the speakers, but... I dunno.
 

Nwickliff

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These are my speakers. I bought them over a year ago for $300 on Craigslist. I was just gettting into the measuring and building at the time and started with some OG Klipsch Heresy speakers and rf82II speakers. Both of which have out of control frequency responses. So with the kit being $244 I was only in $544 for the pair. Not a bad deal, plus I got to learn how to solder a XO together and read a schematic. Well worth the money for me. The new speaker costs $749. I also cross to two sealed ultimax 18” subs so do t have to worry about the bass or sensitivity. To each their own I suppose. Thanks for measuring them, Amir!
 

YSC

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Considering recent events with the LGK, it's good to see not all is lost with Danny and GR. I'd imagine he is pretty confused right now though with ASR... :p

A through comparison review Amir.


JSmith
why would he confuse, he just need to promote Amirm finally knows he is exposed by Danny about his BS false claim so now need to repair relationship.....

But anyway, this is why I am a lurker of ASR, brand alone will give us a biased perception no matter what, but the data is always brutal and tells us what one really need to know
 

Cars-N-Cans

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Why would anybody in his right mind buy a Klipsch in the first place? Those small ones are just terrible and big ones sound "interesting" for first 10 minutes.
Myself, out of ignorance years ago. In the absence of objective data, Klipsch gives the impression of being a more upscale mid-fi brand to consumers who are not savvy with audio. They do look nice and the copper woofer adds a unique bit of flair to the speaker. I think I bought an early version of this or the 500 series. Listening to one of them told me they were not going to be that great. Fortunately the FedEx guy broke the other one for me ahead of time so I had a valid excuse to send them back.
 

Cars-N-Cans

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Still makes me just wonder about a better speaker rather than "fix" a big box store speaker....
From measurements of the RP-500M II by Erin, it seems Klipsch has done much of this already if one were to get the later model. In that regard the kit looses its "raison d'etre" since its paying for something you can just about already buy.
 

voodooless

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Yes, or just buy the successor generation as Klipsch corrected that dip there:


Looks like GR is well aware of this:


… apparently steel nuts for the binding posts would negatively affect the sound :facepalm:
 

thewas

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From measurements of the RP-500M II by Erin, it seems Klipsch has done much of this already if one were to get the later model. In that regard the kit looses its "raison d'etre" since its paying for something you can just about already buy.
Yes, also in the RP-600M II which he has also measured.
Also by using shallower slopes he worsens the vertical directivity and distortion behaviour so I don't see his mod as a improvement, would rather EQ the dip or use/copy the crossover of the new version.
 
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