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Revel C52 Speaker Review and Measurements

amirm

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#1
This is a review and detailed measurements of the Revel C52 center, three-way speaker. I purchased it years ago for my theater. It comes in a gorgeous maple finish which Harman was discontinuing so I got them for a song. :) It costs US $2,499. It has been on the market for well over ten years, if not fifteen.

My photo booth is too small for the speaker. So here is a quick shot of it as it sits in the Klippel NFS measurement system in our messy garage:
Revel C52 Center Speaker 3-way Review.jpg

It is quite heavy for its size and took effort to lift it to put on the platform. This is a cell phone picture and is a shame you can't see the quality of the finish.

Here is the back side:


Revel C52 Center Speaker 3-way Back Panel Connectors Review.jpg

Those bus bars connecting the tweeter to woofer/mid-range section are so shiny and high quality you want to wear them as jewelry! I kid you not.

You can see the test conditions with "stand mounted" selected and tweeter level set to 0 dB. Temperature in the lab was 55 degrees F. We are at see level as far as pressure goes.

FYI you can see the Klippel Microphone boom and its z-axis peaking above the speaker. This was a challenging speaker to measure because it is so wide. But more so because it has four drivers so creates a very complex soundfield. It is a great test of the Klippel Scanner to see if it is able to properly solve the field equations so that it can predict the farfield data we like to see from nearfield (close to speaker) measurements. Nearly 540 measurements which is the same as other speakers I have measured. I thought I may have to increase that but did not have to. Frequency resolution of the graphs is 10 points per octave (actual measurements are at 0.7 Hz resolution).

I know you not be very interested in this speaker but you will be when I tell you that I have the anechoic chamber spinorama measurements for this speaker! So we finally get to check the Klippel NFS system against another set of independent measurements.

Spinaroma Speaker Measurements
I hope by now you are getting used to the CEA-2034 "spinorama" picture which essentially tells us everything we need to know about the speaker's tonality:

Revel C52 Center Speaker 3-way Measurements CEA2034.png


I have set the scale to show from 40 to 110 dB SPL. That compresses the graphs but I have done so that the results can be matched to anechoic chamber results I will show shortly. For now, notice the incredibly smooth frequency response. Other than a slight dip around 1000 Hz, this thing is as rule flat as speakers get.

Oh, the above graph is generated with the fix from Klippel that shows proper Early Reflection DI (it uses to be very smooth and incorrect). Our scale is a bit compressed but you can see that the Early Reflection DI is smooth as we like to see (it doesn't have to be horizontal like on-axis should).

Net, net, this one well-behaved speaker.

Now let's compare it to anechoic chamber measurements:

Revel C52 Center Speaker 3-way Anechoic Measurements CEA2034.png


As far as I can eyeball it, we are right on the money. Same flat response sans the dip around 1000 Hz. Klippel NFS is more accurate down to 20 Hz, not that we care. The directivity plots are all very close to each other as well (note that they have red and blue swapped compared to Klippel NFS).

Given the fact that my sample is not the identical one measured in anechoic chamber, and vagaries of speaker measurements in general, I say it doesn't get any better match than this! The Klippel system using the same parameters as I have used with other speakers is generating data as accurately as anechoic chamber.

I will continue to test speakers that have anechoic chamber to keep building confidence but this is a major milestone, two weeks after the system came to life and made its first measurement!

FYI, sound and vision magazine also measured the C52 using the DIY method and got this:



It is a hard to read graph but the purple line which I am assuming is the direct axis, correlates well with my measurements as well, showing the same dip around 1 kHz.

EDIT: consistent with more recent reviews, here is the same graph but with 50 dB vertical scale:
Revel C52 Center Speaker 3-way Measurements CEA2034 Updated.png


Back to our measurements, our predicted in-room response shows what we already know that once you blend in a set of predicted reflections with direct sound, you get a response that is pretty close to what we want to have:
Revel C52 Center Speaker 3-way Measurements Predicted In-room Response CEA2034.png


Sloping "target curve" is there without any equalization. Yes, it is not like the line I drew but remember, we are talking about speakers here and including a bunch of reflections.

That is it then. I know, you want to see the impedance curve and such but I was freezing in the garage and so didn't take them. Will do so tomorrow and update the review.

Advanced Speaker Measurements
Let's drill down for those interested. Looking at likely horizontal axis reflections that matter we get:

Revel C52 Center Speaker 3-way Measurements Sidewalls Response CEA2034.png


This response (in green) is very similar to on-axis response meaning the brain will likely integrate it well and not think it is another type of sound. Result is that it will broaden the image presented by the center speaker if you allow side-wall reflections. And this is what you want as your theater screen is much wider than the center speaker. Someone talking may not be right at the center so you don't want "pinpoint" sound from the center speaker.

Vertical performance for the likely surfaces has a serious dip:
Revel C52 Center Speaker 3-way Measurements Vertical Response CEA2034.png


If your room is not already too dead, then floor carpet and ceiling absorbers is advised. Those reflections are not beneficial like sidewall ones are so absorbing them is fine.

The full set of horizontal and vertical reflections at 10 degrees are:

Revel C52 Center Speaker 3-way Measurements Full Horizontal Response CEA2034.png

Revel C52 Center Speaker 3-way Measurements Full Vertical Response CEA2034.png


Full spinorama measurements are included as text format for those of you want to make your own plots.

Conclusions
I remember being stunned how good these Revel C52 speakers sounded when I first put them in the room. The house was just finished being remodeled and all I had was a carpet in the theater. So the room was fairly live. Despite that, the sound was sublime. I remember sitting there until 2:00am listening to these speakers. FYI I have them for all 7 channels, not just center. They work very well because they don't interfere with the screen and perfectly match each other.

Purpose of the review was mostly to show how well the Klippel NFS measurements are relative to anechoic independent measurements. I hope you agree they are extremely close and highly trustworthy. Those of you betting the measurements are wrong, better get ready to pay up! :D

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

I can't run a heater while I am testing speakers in the garage. I am sitting there freezing. I am thinking I need some electric blankets to keep warm as I can't run any kind of regular heater due to noise. I hear they make very nice and expensive ones. So please donate to help warm me up using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

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amirm

amirm

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Thread Starter #2
And here is the Predicted-In-Room response data for the ones working hard to get us the preference rating.
 

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Krunok

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#5
Excellent work and good news with confirming compliance between anechoic an Klippel measurements.

Any chance, after yo get some sleep, you can do a simple RTA MMM measurement with REW so it can be compared with predicted in-room response? :)

IMHO it would be really nice to have even a simple comparison between predicted in-room response curve and what we measure in our rooms and this speaker seems to be a perfect candidate for that.

P.S. I am not proposing you do manual measurement with every speaker you test - I'm proposing you do that only one with this speaker so we can correlate predicted in-room response with what you would measure.
 
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digicidal

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#7
So your system is $17,500?
I need to rethink my audio budget... :oops:

Great to see a SOTA speaker reviewed!
@amirm probably has some electronics to go with those as well. Just sayin' :p
 
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#8
@Krunok identified an error in the CTA 2034 curves generated by the Klippel software. This was in NHT review thread at post 27. Has Klippel fixed the software for the Revel F52 test?
 

milosz

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#9
Do you have these Revel center speakers all 'round? Or do you their floorstanders for left and right? Revel makes good speakers.
 

JIW

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#10
@Krunok identified an error in the CTA 2034 curves generated by the Klippel software. This was in NHT review thread at post 27. Has Klippel fixed the software for the Revel F52 test?
Yes.
Oh, the above graph is generated with the fix from Klippel that shows proper Early Reflection DI (it uses to be very smooth and incorrect).
 

pma

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#11
Nice work! The dip between 800-1200Hz is interesting, there should not be a crossover frequency? Is it phase cancellation, or diffractions, or something else? Seen both in horizontal and vertical directional plots. Midrange driver issue?
 

napilopez

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#13
Now this is what I'm talking about! Great stuff Amir. Measurements we can match right up with anechoic data. And it matches extremely closely for different measurements, taken in different places, with different techniques, different hardware, and a different test unit - not to mention a speaker that appears to have been well worn with use.

Since I've become the resident scaling and overlays guy, here you go. Tried to match SPL level of primary curves, which are a bit higher in amir's than Revel's, so the DI curves end up being offset by a dB or so:

Snag_a6ee46ab.png


For all practical interpretation purposes these results are basically identical. Yours shows a bit less energy in the top octave and bass, that's about the only notable difference. The horror :eek:
 
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flipflop

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#17
Since there's no dip in the Early Reflections graph at 800-1200 Hz, does that mean it can't be fixed with EQ?
 

Krunok

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#18
Since there's no dip in the Early Reflections graph at 800-1200 Hz, does that mean it can't be fixed with EQ?
From the room EQ perspective you should be looking at predicted in-room response graph and there it doesn't seem to be anything that needs fixing except adjusting it to your preferred tonal balance curve.
 

spacevector

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#19
So am I understanding correctly that you have 7 of this exact same speaker for your surround sound setup? I haven't yet come across using a 'center channel speaker' in this way.

Would you recommend a pair of these for a stereo setup?
 

flipflop

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#20
From the room EQ perspective you should be looking at predicted in-room response graph and there it doesn't seem to be anything that needs fixing except adjusting it to your preferred tonal balance curve.
PIR shows a ~1 dB dip. Not much, but why not EQ it if there's no downside?
 
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