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

Rate this speaker mod:

  • 1. Poor (headless panther)

    Votes: 8 4.4%
  • 2. Not terrible (postman panther)

    Votes: 39 21.7%
  • 3. Fine (happy panther

    Votes: 109 60.6%
  • 4. Great (golfing panther)

    Votes: 24 13.3%

  • Total voters
    180

Vicfontaine

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You think you do. You don't know. There is so much folklore around tubes that vast majority of people are biased by that. I have done countless listening tests of tubes. They are either transparent or distortion factories. Neither matches what you and others claim. Until you perform a controlled, blind test, you don't know what you really prefer.
Are there any studies that follow up on double-blind preference tests to see if the preference holds after the listener is unblinded? That is, if someone picked out a product based on a double blind test. They then have to get it home and listen to it knowing what it is and carrying the weight of our biases. Can we get ourselves to obliterate our biases with listening tests? Have you found that to be the case in your own listening tests?
 

ThoFi

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Are these double blind tests independent of the room?
Same results in different rooms?
 

deniall83

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You think you do. You don't know. There is so much folklore around tubes that vast majority of people are biased by that. I have done countless listening tests of tubes. They are either transparent or distortion factories. Neither matches what you and others claim. Until you perform a controlled, blind test, you don't know what you really prefer.
I had a relatively expensive Donald North Audio tube headphone amp many years ago. I absolutely loved it and was convinced it sounded better than any SS amp I'd heard. I finally got around to doing a test against a small, cheap, SS headphone amp and couldn't reliably tell which was which. I was bummed but I learnt a lot about placebo effect and sold the amp not long after.
 
OP
amirm

amirm

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Are there any studies that follow up on double-blind preference tests to see if the preference holds after the listener is unblinded? That is, if someone picked out a product based on a double blind test. They then have to get it home and listen to it knowing what it is and carrying the weight of our biases. Can we get ourselves to obliterate our biases with listening tests? Have you found that to be the case in your own listening tests?
I don't know any kind of follow up test like that. In general, we adapt to less than ideal sound. You might say then it doesn't matter what the speaker is doine. But it does the first time you go listen to a neutral speaker! Then realize yours is too bright, etc.
 
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amirm

amirm

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Are these double blind tests independent of the room?
Same results in different rooms?
Dr. Toole while at NRC has conducted them in different rooms (and Harman also tested different seating positions). Statistical analysis is performed and room is always a factor as well. But speaker tonality stands on its own as an independent and statistically significant factor.
 

BDWoody

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Are there any studies that follow up on double-blind preference tests to see if the preference holds after the listener is unblinded?

"In summary, the sighted and blind loudspeaker listening tests in this study produced significantly different sound quality ratings. The psychological biases in the sighted tests were sufficiently strong that listeners were largely unresponsive to real changes in sound quality caused by acoustical interactions between the loudspeaker, its position in the room, and the program material. In other words, if you want to obtain an accurate and reliable measure of how the audio product truly sounds, the listening test must be done blind."
http://seanolive.blogspot.com/2009/04/#:~:text=In summary, the,be done blind.
 

Sonny1

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Apr 5, 2020
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No. His argument was not even coherent. I plan to do a video and explain.

Thanks for bringing intelligent commentary and science to the murky world of hifi snake oil deception. I look forward to your video. Also, I’m not picking on Danny, he seems like a nice enough guy.

Great stuff!
 

Dial

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May 27, 2022
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Their only interest is the high sensitivity but since their measurements are exaggerated (They claim, anyone can build such things themselves. They claim 96 dB ("I" version) or 94.5 (!) ("II" version, much more expensive: twice the price!).
 

davidki

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Jul 9, 2022
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I retailed Axiom for a couple of years and they sold well against Paradigm, Klipsche and Polk.
I saw your post on Axiom and thought I'd ask you about their Bookself M5 product. Also, it's no secrete that they also product speakers for Bryston ... did you retail the Bryston as well. I just purchased a new Bryston 4B3 for our studio and was wondering about their Mini Mini T product.... it seems like both companies have much "Review" support and not much of a showing when trying to research them... any idea's why?
 
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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.
View attachment 215422

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):
View attachment 215423

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:

View attachment 215424

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:
View attachment 215426

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:
View attachment 215427

And with it, predicted in-room response:
View attachment 215428

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:

View attachment 215429

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

View attachment 215430

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:
View attachment 215431

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:
View attachment 215432

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:

View attachment 215600
View attachment 215601

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:
View attachment 215602

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.

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Honestly, I think the upgrade makes little sense. Just use an eq or pick speakers that have a flatter response. 244 for speakers that can be had brand new for less than 400 now. But thanks for the informative review.
 
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