GR Research X-LS Encore Kit Speaker Review

[Rick Sykora]

The only information or insight I have into what sort of felt would be needed is what I read this afternoon in the writeup by David Ralph, which he wrote twenty years ago.

https://www.speakerdesign.net/felt_amelioration/feltssenter.html

I have no idea whether there is more recent research that is available. But based on what I saw there, it seems likely that F13 at least 1/2" thick, placed to both sides of the tweeter and extending from the edge of the flange to the start of the roundoff of the baffle edge (or possibly sticking out past the point where the baffle edge begins to recede), and with height matching the diameter of the tweeter flange, should produce a measurable attenuation of the off-axis response rise just above the crossover point. I say "should" because if felt is truly effective at suppressing diffraction ripple this is what we should see, given that ctrl has pretty much demonstrated that about half of the response rise just above the crossover point is actually a diffraction effect. But this isn't something that I'd bet on. It would be an interesting experiment and one that has the potential to yield useful information.

I have tried this many times before with limited or no measurable difference btw. My initial motivation was to see if felt could be used to avoid flush mounting drivers. TBH, based on that effort, my expectations are rather low, but will try anyway.

I know Vandersteen uses felt extensively in his lower end models. Given more contemporary, less expensive fabrication techniques and the aesthetic downsides, do not see much used for external damping any more. My Signet speakers had sorbethane around the tweeters and it eventually deteriorated.

 

[Francis Vaughan]

John Dunlavy was an advocate of the felt approach (indeed he claimed to have invented it, and had the patent.) He was pretty clear that it was for control of diffraction and managing directivity. Then again, he told me that he sourced his felt from South Africa, because it had to be just the right felt, or it didn't work properly. Another local company, VAF, continues this approach, and are quite clear it is all about diffraction. (They have some common heritage with Dunlavy, one of their designers worked for Duntech at one point.) Like many, I have played with, and had a frustrating time, with felt. I feel it can be made to work, but it isn't a trivial task. I also think waveguide theory has rendered the approach obsolete. In some very fuzy way I suspect the layers of felt are working bit like a lossy waveguide.

https://patents.google.com/patent/US4167985A/en

https://vaf.com.au/products/signature-i-93mkii-active?variant=9000918679617

 

[KaiserSoze]

Ah, sorry, I wasn’t being as clear as I might. No, the directivity and other major issues won’t be affected. But there will be changes to the bass and lower mid. There is a whole lot a waffle about the merits of the kind of damping and what resonances it can affect. The design of NoRrez is very specific and claims are made about the effect on sound quality. If it works as claimed there should be clear measurable changes. Then the question might be whether these changes are desirable. Eventually there is a question of cost effectiveness. Right now the preferred cabinet damping costs a similar amount to the bass driver it is supposed to be magically transforming the sound of.

I read the spiel on gr-research. It seemed to be trying to say that it damps both panel resonances and internal standing waves. It would potentially have some effect at decreasing Qtc, the system resonance of the driver/enclosure, similar to the effect of stuffing the enclosure with fibrous material. If it alters Qtc there should be some change in how the bass rolls off. The mild response rise at 110 Hz, which seems to be milder than the similar response rise found in the great majority of speakers, should be slightly attenuated, and the rolloff below 100 Hz should be slightly less steep. The same effects you would get by making the enclosure slightly bigger, or by stuffing it with fibrous absorptive material. But the speaker does not really exhibit any defect in this area. And the spiel promoting the product does not mention this effect specifically. And I don't see how it would have any beneficial effect at smoothing out the off-axis response.

So far as I know Danny Richie has not made any comments about which specific shortcomings of the speaker are to be blamed on not doing the roundoff, not using the NoRez, etc., and has not indicated what specific improvements are likely to be observed in the more luxurious version of the speaker. It seems like he is just hoping that there will be some difference that Amir will discover. It will be interesting.

 

[KaiserSoze]

The OLD design has problems regardless of the shape of the cabinet.

GR-Research-X-LS-Encore-horizontal

View attachment 76102


Much more interesting is the NEW desing.

GR-Research-NX-studio-horizontal-off-axis-resized

View attachment 76103

Very meritorious considering that the ribbon tweeter (waveguide) is open baffle.


Update, NX-Studio ribbon tweeter (rear)
https://www.audiocircle.com/index.php?topic=171448.msg1816325#msg1816325

I don't understand this. Is this supposed to be a redesign of the same speaker? Or is this a completely different speaker? I don't know what it is, and you have not explained what it is or how it relates to the speaker to which this thread is dedicated, the X-LS Encore. If this is a completely different speaker, why did you post this here? Why on earth would you do that? I really wish that you would explain, and unless this is somehow not what it appears to be, you should either delete it or ask for it to be moved to a different thread.

 

[Deleted member 2944]

This is a guy (Danny Richie) who not long ago commented that ASR should learn how to use that fancy test equipment.
How funny is that?

Dave.

 

[KaiserSoze]

I like much more the graph of 5.25" coaxial (KEF Q100), measured by Zvu, but it is other design and sound than NX-Studio.

View attachment 76104

Why are you dumping all this other stuff here? Isn't this thread supposed to be specifically about the X-LS Encore? Most threads do eventually veer off in random directions, but this one had been strictly about one specific speaker. I am very confused.

 

[KaiserSoze]

I have tried this many times before with limited or no measurable difference btw. My initial motivation was to see if felt could be used to avoid flush mounting drivers. TBH, based on that work my expectations are rather low, but will try anyway.

I know Vandersteen uses felt extensively in the lower end models. Given more contemporary, less expensive fabrication techniques and the aesthetic downsides, do not see much external damping any more. My Signet speakers had sorbethane around the tweeters and it eventually deteriorated.

I've never personally done any experimentation with it, so I don't have any strong opinions about it. I read the article that David Ralph wrote for AudioExpress, and while it was fairly persuasive, I tend to take everything with a gain of salt until multiple people have done similar experiments and have obtained similar results. I think that appropriate use of felt is more likely to mitigate the diffraction issue than the recommended 3/8" rounding of the baffle edge will.

 

[maty]

I don't understand this. Is this supposed to be a redesign of the same speaker? Or is this a completely different speaker? I don't know what it is, and you have not explained what it is or how it relates to the speaker to which this thread is dedicated, the X-LS Encore. If this is a completely different speaker, why did you post this here? Why on earth would you do that? I really wish that you would explain, and unless this is somehow not what it appears to be, you should either delete it or ask for it to be moved to a different thread.

X-LS Encore is a very old design, at least for me. Much more interesting its latest design (but more expensive). When you listen to open baffle loudspeakers, you do not forget the experience. Unfortunately they require very large rooms ... except for the NX-Studio.

First without sub, after with a sub and later with two subwoofer.

 

[maty]

To compare graphs.

 

[KaiserSoze]

John Dunlavy was an advocate of the felt approach (indeed he claimed to have invented it, and had the patent.) He was pretty clear that it was for control of diffraction and managing directivity. Then again, he told me that he sourced his felt from South Africa, because it had to be just the right felt, or it didn't work properly. Another local company, VAF, continues this approach, and are quite clear it is all about diffraction. (They have some common heritage with Dunlavy, one of their designers worked for Duntech at one point.) Like many, I have played with, and had a frustrating time, with felt. I feel it can be made to work, but it isn't a trivial task. I also think waveguide theory has rendered the approach obsolete. In some very fuzy way I suspect the layers of felt are working bit like a lossy waveguide.

https://patents.google.com/patent/US4167985A/en

https://vaf.com.au/products/signature-i-93mkii-active?variant=9000918679617

I hadn't really thought about the role of diffraction in the off-axis response until ctrl used simulation to demonstrate that diffraction very likely is responsible for about half of the rise in the off-axis response of this speaker above the crossover point. Since a waveguide would prevent the tweeter's output from strongly illuminating the baffle edge at this frequency range, it does seem likely that even the diffraction-related portion of that rise would go away if a waveguide were used. But perhaps in a three-way speaker where the designer doesn't want to put the tweeter in a waveguide, the use of felt might then be effective. But even if so I don't think I'd want to use it because to me it is unattractive.

With respect to your last comment, raising the possibility that felt works kind of like a lossy waveguide, I was thinking the same thing last night when I read the article that David Ralph wrote for AudioExpress. In one of the arrangements he found especially effective he used a thin strip of felt close to the tweeter on one side and then a thicker piece further out, in a stepwise manner. He found it very effective but said that he didn't know why. Many of these acoustic effects are so empirical that trying to isolate individual causative effects in a non-contrived way seems almost silly. Maybe he would have gotten a similar result using constant thickness but with a gradient in the density of the felt. The felt is partly reflective and partly absorptive, so it is possible that in his stepped configuration that what he had actually done was to have implemented a waveguide made of felt. This would be an interesting area for experimentation, especially if the premise or hypothesis is that it would be better for the waveguide to not affect the on-axis response to the extent that it does.

 

[KaiserSoze]

I'll tell you what......you worry about your posts and I'll worry about mine.
Does that work for you???

Dave.

Now I am more confused than before. The comment to which you replied wasn't directed to you and had nothing to do with you. It was a reply to one of the posts by maty, who has placed at least two posts, in this thread, that do not seem to belong to this thread. Maybe somehow the wires are getting crossed at the audiosciencereview.com server and posts are showing up as responses to the wrong post. I don't know what's going on, but I certainly did not write that comment in response to any of your posts.

 

[richard12511]

Well, why don't you quote Maty and/or provide the context for your comments then? That's just common courtesy.
I will edit/delete my post then.

Dave.

He did quote maty. Is that not what you see? I too was confused by your reply.

 

[Deleted member 2944]

He did quote maty. Is that not what you see? I too was confused by your reply.

My fault. Sorry.
When you fellas quote Maty, please just make a mention of his name in your text so those of us who are ignoring him understand the context.
Why that guy is not banned on numerous forums is a mystery to me. But oh well.

Apologies.

Dave.

 

[KaiserSoze]

My fault. Sorry.
When you fellas quote Maty, please just make a mention of his name in your text so those of us who are ignoring him understand the context.
Why that guy is not banned on numerous forums is a mystery to me. But oh well.

Apologies.

Dave.

No worries.

 

[Mnyb]

I wanted to take seriously those people who think they can hear a sound change after replacing a cheap foil capacitor with a high-end capacitor in the high frequency path of the crossover (and ignore the possible psychological effects that can lead to such a perception).

To then show step by step that this change in sound is very likely caused by slightly different capacitance values, since only minimal differences occur when measuring really identical capacitors, in the frequency range relevant for humans. And this completely independent of the type of measurement IMD, CSD, FR,...
and that these results cannot possibly be reconciled with the sound assessments made in the capacitor reviews.

At least I tried...

I think many non engineeris are oblivious to tolerances ? They don’t know what it is .
We that are some kind of engineeris knows that capacitors comes in x mf +- y mf and resistors in similar fashion some ohm +- some tolerance E96 series or similar . Ie all components vary somewhat.

OT: sometimes the expensive components are actually the same as the cheap ones , but selected to tighter tolerance

 

[KaiserSoze]

I think many non engineeris are oblivious to tolerances ? They don’t know what it is .
We that are some kind of engineeris knows that capacitors comes in x mf +- y mf and resistors in similar fashion some ohm +- some tolerance E96 series or similar . Ie all components vary somewhat.

OT: sometimes the expensive components are actually the same as the cheap ones , but selected to tighter tolerance

Capacitors are very nearly as simple as resistors. Apart from the way in which different types of capacitors age differently after being in use for a few decades, and apart from the fact that some capacitors use an electrolyte that will misbehave if a DC bias is applied to it with the wrong polarity, the differences in the different types are mostly limited to how much real estate they require and the voltage they can withstand. The numerous formulas and equations that you see in textbooks that describe capacitor behavior in some way or another are never specific to the type of capacitor. I've need seen a formula or equation that dealt with the electrical behavior of a capacitor in a circuit where there was any footnote or warning that said something like, "Note: the above formula is only valid for tantalum capacitors; if you use mylar film capacitors, please refer to the chapter on the theory of mylar film capacitors."

 

[Rick Sykora]

The only information or insight I have into what sort of felt would be needed is what I read this afternoon in the writeup by David Ralph, which he wrote twenty years ago.

https://www.speakerdesign.net/felt_amelioration/feltssenter.html

I have no idea whether there is more recent research that is available. But based on what I saw there, it seems likely that F13 at least 1/2" thick, placed to both sides of the tweeter and extending from the edge of the flange to the start of the roundoff of the baffle edge (or possibly sticking out past the point where the baffle edge begins to recede), and with height matching the diameter of the tweeter flange, should produce a measurable attenuation of the off-axis response rise just above the crossover point. I say "should" because if felt is truly effective at suppressing diffraction ripple this is what we should see, given that ctrl has pretty much demonstrated that about half of the response rise just above the crossover point is actually a diffraction effect. But this isn't something that I'd bet on. It would be an interesting experiment and one that has the potential to yield useful information.

Felt's effectiveness follows my prior test experience, but first a couple of notes. Thickest felt I have is 1/4". 1/2" is pretty thick and Vandersteen's used something closer to 1/8". I tried strips the height of the tweeter; first close to the edge and then on the tweeter faceplate. There is some fairly significant shifts in frequency response, but little change in the overall diffraction rippling. The main issue is that the felt response is not clearly better and might be arguably worse. Pics to come once I get them off of the computer I use to measure...

 

[KaiserSoze]

Felt's effectiveness follows my prior test experience, but first a couple of notes. Thickest felt I have is 1/4". 1/2" is pretty thick and Vandersteen's used something closer to 1/8". I tried strips the height of the tweeter; first close to the edge and then on the tweeter faceplate. There is some fairly significant shifts in frequency response, but little change in the overall diffraction rippling. The main issue is that the felt response is not clearly better and might be arguably worse. Pics to come once I get them off of the computer I use to measure...

My suggestion to apply felt to this speaker to see whether it would fix the diffraction issue was sort of reckless. Please do not take that suggestion seriously. It would very likely prove to have been a waste of time and effort. What is more relevant, rather than demonstrate the effectiveness of felt, is to demonstrate that 3/8" rounding of the baffle edges has no appreciable effect at mitigating the diffraction effect. This will be demonstrated by comparing the soon-to-arrive speaker with the one already tested and observing that the diffraction-related effects are no less pronounced in the one with 3/8" rounding than in the one without.

 

[Rick Sykora]

My suggestion to apply felt to this speaker to see whether it would fix the diffraction issue was sort of reckless. Please do not take that suggestion seriously. It would very likely prove to have been a waste of time and effort. What is more relevant, rather than demonstrate the effectiveness of felt, is to demonstrate that 3/8" rounding of the baffle edges has no appreciable effect at mitigating the diffraction effect. This will be demonstrated by comparing the soon-to-arrive speaker with the one already tested and observing that the diffraction-related effects are no less pronounced in the one with 3/8" rounding than in the one without.

too late, but no problem!

The actual rounding test will be done by Amir comparing my build to the designer's. Although this will have the issue of changing things other than just the baffle rounding.

 

[KaiserSoze]

too late, but no problem!

The actual rounding test will be done by Amir comparing my build to the designer's. Although this will have the issue of changing things other than just the baffle rounding.

If the soon-to-arrive speaker with rounding shows a clear reduction in diffraction effect vs. the one you built, then the question of whether it is due to the rounding vs. something else will need to be considered. If that happens, then if there isn't a wholesale change in the crossover, I would have to attribute the improvement to the 3/8" roundoff. But I will be very surprised if the evidence indicates that 3/8" rounding is effective at mitigating diffraction at frequencies below upper treble.