Selah Audio RC3R 3-way Speaker Review

[napilopez]

NBD just cares about FR deviation in small, separate segments.
SM cares about FR deviation and tonal balance, by looking at the segments together.

Thanks, that's what I thought, since the Olive paper describes NBD being good for detecting resonances. I guess we can't just eyeball smoothness then. I can't tell that the smoothness looks that much worse than the Neumann or LS50s from your spreadsheet, both of which scored much higher in this specific part. Also goes to show the importance of having enough measurement resolution...

Neumann (0.786):

LS50 (0.764):

Selah 0.422:

EDIT: Just saw your own edit with the extra context, thanks, that helps a lot!

 

[dshreter]

This is my speaker Amir measured. Amir, huge thank you for taking this one for a spin!

In real life the speakers are bright like the measurements have suggested. I use treble cut and bass boost tone control, which flattens our the in room response nicely. The spinorama is pretty smooth, and to my ear they respond well to the necessary but basic EQ.

Vertical treble response is unsurprisingly odd because it is a vertical ribbon tweeter. Horizontal directivity is solid though.

It seems like there’s not clear consensus yet on what these measurements say about the speaker, and it “scores” quite poorly. This is at odds with my subjective experience with the speaker. Also it is from a talented designer that leveraged some fairly expensive drivers (which are still available), so there may be more to unpack here.

Apologies that the review from Amir is not as detailed at others, this can be attributed to logistical matters of getting the speaker back to me.

 

[MZKM]

and it “scores” quite poorly.

It’s around as good as the LS50.

 

[TimF]

I imagine that we can conclude that good components such as well made drivers and cross-over components do insure a fine functioning final product in toto. Also, I imagine that we can conclude that all speakers have design and performance compromises such as on-axis and off-axis balance. I assume I (we) will learn as we assess more speaker examples the most common occurring performance weaknesses, and the degree to which the better performing speakers address the various aspects of performance. That is, in the realm of the affordable products, how good are the better performers, and what constitutes good performance. I am the student here.

 

[BYRTT]

After looking at the PIR, I expected the the preference rating to be awful. Since it's not, I had another look at the PIR and noticed it's now shown in 2 dB increments instead of 5 dB like in the previous reviews. It's really not that bad at all

.....Please pay attention to scaling everyone......

.....Amir’s graph of the PIR shows this to a magnified degree.

Selah Audio RC3R PIR curve overlaid Spinorama on 50dB scale plus polars normalized at right side:

 

[hardisj]

I do find it interesting how the horizontal response (maybe the vertical, too; I haven't looked closely) is not symmetrical across the -90 to +90 measurements. Makes me question the result, TBH. I don't see a reason why one side would measure differently unless the drivers weren't perfectly center-aligned. OTOH, the difference is only a couple dB. Just one of those things that makes you think "hmm". *shrug*

(I provided my plot of the data below)

 

[dshreter]

I do find it interesting how the horizontal response (maybe the vertical, too; I haven't looked closely) is not symmetrical across the -90 to +90 measurements. Makes me question the result, TBH. I don't see a reason why one side would measure differently unless the drivers weren't perfectly center-aligned. OTOH, the difference is only a couple dB. Just one of those things that makes you think "hmm". *shrug*

(I provided my plot of the data below)

View attachment 48310

It’s a 16 year old speaker on its second owner. Things could happen in that time that could explain this....

 

[ctrl]

If no one has mentioned it, Amir please change your conclusions in this diagram.

It's most likely not resonances around 800-900Hz, but simply vertical cancellations caused by the crossover from the woofer to the midrange dome.
Followed by a strong vertical expansion in the radiation in the range 1000-2000Hz - see "Vertical Directivity Normalized" in Post#4.

The horizontal frequency response measurements show no signs of resonance in the 700-1000Hz range - see "Horizontal Directivity" in Post#4.
The ScanSpeak 18M shows a suspension resonance in the range 800-1000Hz, but in this case it is suppressed by the crossover.

 

[dshreter]

Just a note of minor interest - this is a sealed (no port) speaker. Most of the speakers analyzed so far have been ported.

 

[hardisj]

It’s a 16 year old speaker on its second owner. Things could happen in that time that could explain this....

 

[phoenixdogfan]

"Good to go back in time and look at a speaker that while not terrible, doesn't follow the rule of having good "off-axis" sound."

Great point. Floyd Toole's ideas for speaker design are just starting to gain wider currency in the market. It will be interesting to see in the next few years what designers will be putting out to follow this blueprint for better sounding speaker designs.

 

[phoenixdogfan]

Pink Panther was gone to the meeting before Amir.

Musta called in sick.

 

[lszomb]

I started to worry my 25 years old ATC SCM35...

 

[maxxevv]

From a mechanical gut-feel kind of perspective, would the directivity been better if the 3 drivers were placed closer together in the vertical stacking ?

 

[dshreter]

Looking at Revel and JBL, what are the advantages of building 3+ way speakers these days? If they can build the M2 in a 2-way, why is top of the Revel line a 4-way? While they share a philosophy for output, construction is wildly different.

 

[bobbooo]

Thanks, that's what I thought, since the Olive paper describes NBD being good for detecting resonances. I guess we can't just eyeball smoothness then. I can't tell that the smoothness looks that much worse than the Neumann or LS50s from your spreadsheet, both of which scored much higher in this specific part. Also goes to show the importance of having enough measurement resolution...

Neumann (0.786):

View attachment 48287

LS50 (0.764):View attachment 48292


Selah 0.422:
View attachment 48288

EDIT: Just saw your own edit with the extra context, thanks, that helps a lot!

The smoothness variable (SM) in Olive's formula includes the 'slope' variable (SL) in its calculation, which he defines as the difference between the 'target slope' (-1.75 for the predicted in-room response i.e. a gentle downward slope) and the actual measured PIR slope. I suspect it's this larger difference from the target slope for the Selah (basically too flat PIR, and so perceptually too bright) compared to the other speakers, which appreciably lowers its smoothness score, as opposed to any significant deviation from the regression line (what we would intuitively call smoothness). So 'smoothness' is a bit of a misnomer here, as it implicitly includes spectral tilt in the form of the slope variable as per Olive's definition.

 

[bobbooo]

It seems like there’s not clear consensus yet on what these measurements say about the speaker, and it “scores” quite poorly. This is at odds with my subjective experience with the speaker. Also it is from a talented designer that leveraged some fairly expensive drivers (which are still available), so there may be more to unpack here.

It's currently ranked 4th out of the 11 speakers tested so far (higher than the KEF LS50) if it were used with a subwoofer - not bad for a 16 year old speaker The bright spectral tilt is holding it back though. @MZKM's very useful 'Breakdown' plot for the speaker shows the details of the score.

 

[Francis Vaughan]

Looking at Revel and JBL, what are the advantages of building 3+ way speakers these days? If they can build the M2 in a 2-way, why is top of the Revel line a 4-way? While they share a philosophy for output, construction is wildly different.

The core part of the M2 is the waveguide. Design of these is not trivial, nor is construction. There are not many manufacturers with the expertise and resources to do this. But a critical problem is that the performance of the waveguide with frequency is tied to its size. You simply cannot make a waveguide go low if it is not wide enough. The width of the M2 cabinets is defined by the low frequency cutoff of the high frequency driver. So this places constraints on the low frequency driver. As well as being able to perform all the way up to the crossover, its directivity must match at the crossover, and this places limits on its diameter. One will note that pretty much all waveguide two ways have the same morphology. Without a scale they all look the same. This is partly determined by matching of waveguide cuttoff and bass driver high frequency directivity.

Using a stack of drivers of different diameters allows control of directivity simply by choosing the crossover points so that you cross over before a driver becomes too directional. The intrinsic directivity determined by the driver diameter allows design of the overall horizontal directivity.

One feels sure market expectations, WAF, and economics have a great deal to do with what is marketed. I'm sure we will be seeing more and more large waveguide speakers as the technology becomes better appreciated. But there is no free lunch. Waveguides have engineering tradeoffs of their own, so don't expect more conventional designs to vanish.

 

[napilopez]

Looking at Revel and JBL, what are the advantages of building 3+ way speakers these days? If they can build the M2 in a 2-way, why is top of the Revel line a 4-way? While they share a philosophy for output, construction is wildly different.

Different ways of approaching the same issue? I mean, if you can design a good speaker on different ways that appeal to different users, why not?

And to add to @Francis Vaughan's point about directivity and waveguides, using such a massive deep waveguide will lead to narrower directivity, and we know that wide vs narrow directivity is largely preferential and contingent upon the reproduction venue. Top revels and the M2 are probably some of the best speakers in the world, but from all I've read, they don't sound the same.

 

[LDKTA]

Very interesting...