GR Research X-LS Encore Kit Speaker Review

[KaiserSoze]

With DIY kits, the focus is on making the speaker cabinet as simple as possible to reproduce.
Rounded side edges would certainly improve the radiation pattern. However, the radius must have a certain size for this.

This is nothing new, however, as the magazine Hobby-Hifi, for example, already showed in detail 20 years ago.
Here is a small excerpt from the article (Have removed the German comments from the picture, the results speak for themselves, the frequency responses 0° to 60° are shown):
Source: http://hobby-hifi.de/Archiv/01/05_01/05_01.html
View attachment 75493
The test object had a baffle width of 0.17m. This means that the distance of the tweeter to the lateral edge of the baffle is 0.85m, which at a wavelength corresponds to the frequency of 4kHz - exactly the problematic frequency range.

UPDATE: The percentages in the image refer to the baffle width of the loudspeaker. In order to achieve a similar effect as in the bottom diagram with a 0.3m wide loudspeaker (problematic frequency range would be around 2.3kHz), the radius of the rounding must be 45mm.

Two important remarks on this:
- A radius that is too small further exacerbates the problem of edge diffraction - the frequency response becomes even more unsteady.
- Rounding the side edges reduces the "effective" baffle width, the effect of edge diffraction shifts to higher frequencies and "smears" the edge diffraction over a wider frequency range, which means that the crossover will most likely have to be adjusted.

Nowadays, even for hobby loudspeaker developers, it is no longer a problem at all to optimize the radiation of a loudspeaker through simulation (before the first prototype must be produced)- it is almost child's play

I had several thoughts after reading this.

First and foremost, there is little reason to hypothesize that the irregularity in the off-axis response of the X-LS Encore is related to edge diffraction. The overall shape of the off-axis response is strongly indicative of an off-axis response that you get when, at the crossover point, there is a directivity mismatch between the woofer and the tweeter. At face value there is the obvious question of how it would make sense to think that this could be corrected through a technique that deals with diffraction-related problems.

In the MLSSA graphs you show from the article, the curve at the front appears to be the on-axis response; the curve at the back is the response 60 degrees off-axis. We are concerned here with correcting an anomaly in the off-axis response, whereas in the article the response anomaly that is being dealt with is in the on-axis response (primarily at least it is the on-axis response). Thus, the diffraction-related technique as illuminated in the article is not concerned in any useful or particular way with how the off-axis response per se is affected by diffraction ripple or is likely to be affected by a diffraction-mitigating technique that applies expressly to the on-axis response.

It might turn out that in the off-axis response the diffraction ripple for this speaker will produce a dip at about 1.6 kHz and a peak about an octave higher in frequency, such that there will be reasonably good frequency alignment between the problem and the proposed solution. If so, there is at least a possibility (albeit remote) that diffraction reduction will have the desired effect on the off-axis response. But there are two points I'll make. First, nowhere in the article that you included or in your comments is there any hint that in order for this approach to have even a slim possibility of working it is first necessary to investigate whether the off-axis response is affected by the diffraction ripple in the particular way by which reduction of the diffraction ripple would have the desired effect as opposed to making it worse (i.e., the good frequency alignment that may in fact exist was in no way a given). Second, if it happens that the frequency alignment is such that reducing diffraction would have the desired effect on the off-axis response, then it will also be true that the diffraction ripple is beneficial to the on-axis response and that if you reduce the diffraction ripple by rounding the edges (enough for it to matter), the on-axis response will suffer correspondingly. This implies the need to make adjustments to the crossover, superficially analogous to the need you encounter if you add a waveguide to the speaker. Except that it is relatively straightforward to make the indicated adjustment to compensate for the effect of a waveguide, whereas if the on-axis response owes its flatness to the presence of diffraction ripple and you take away the diffraction ripple, the correction that would need to be applied to restore the on-axis response to flatness would be essentially equivalent to correcting for the effect of diffraction ripple in an on-axis response that would be flat were it not for the effect of the diffraction ripple. You might be able to do this using DSP and using multiple parametrically-defined corrections, one for each peak and one for each dip in the diffraction ripple, but it is obviously not something that is realistic in the context of a passive crossover.

 

[Thomas_A]

The off-axis plateau in that range will almost certainly be audible although "harsh" might not be the best word to describe it (except for lack of a better word that comes to mind ...). As you say, rounding the edges is not likely to have any effect on this. In fact if it has any effect it will be the opposite of the intended effect because the 1st peak in the diffraction ripple occurs right in the middle of the response dip below the crossover frequency, i.e., the response dip that is due to the woofer's high directivity at frequencies slightly below the crossover point.

With respect to the 1-5 kHz region, it is of importance that the 2-4 kHz region is not peaking in relation to 1-2 kHz, and this applies both on and off-axis. I don't have an ideal word for it but "harsh", "bright", "hard" or just "unpleasant" when listening to soprano voices is what I have experienced during my 20 years DIYing loudspeakers and filters. I have not looked through all review results but there are several speakers showing this kind of peaking. And for this one, he made EQ to lift the 1-2 kHz region, which might fix a bit.

 

[KaiserSoze]

If you can explain that in more detail, I can't follow you.
The combination 6.5'' woofer with 1'' tweeter is actually unproblematic in terms of matching radiation (if CD behaviour is not the goal).

Say what? This is confusing. Are you saying that the directivity mismatch is not attributable to the difference in the driver size and to the fact that the wavelength at the crossover point is roughly equal to the diameter of the woofer and more than 6 x greater than the diameter of the tweeter? Are you saying this, or are you saying that directivity mismatch is not a problem except when it is deemed a problem? I honestly can't tell which you are saying.

 

[KaiserSoze]

its pretty much accepted generally on the gr forum at audiocircle a 3/8 roundover is necessary. Id like to see a review of these speakers with captainHemos flatpack with norez and proper cabinet construction (w roundovers).

A roundoff radius of 3/8 inch is barely going to have any effect at all at frequencies below 4 kHz.

Exactly what problem is this supposed to solve? Even if this amount of roundoff where particularly effective at the crossover frequency (it wouldn't be), do you think that the dip in the off-axis frequency response at about 1.6 kHz and the broad plateau about an octave higher is caused by diffraction? If this is what you believe, could you please explain why?

 

[maty]

Okay, there were some statements in the last posts that I can't understand - could partly be due to the translation.

Therefore I would like to show in a simplified way what is possible by changing the baffle, with unchanged cabinet dimensions - similar to the Philharmonic-BMR.

To keep my effort low, I use chassis simulations that are already on my hard disk. As woofer I use the SB17NAC35 and as tweeter the Seas-DXT, because the tweeter of the Encore also has a small waveguide. The cabinet dimensions are the same as in the Encore kit.

The fact that cancellations occur around the crossover frequency in the vertical radiation of vertically stacked drivers no longer needs to be explained, therefore the horizontal radiation is mainly considered.

If not stated otherwise, the normalized horizontal radiation pattern up to 90° is shown in 15° steps. To save computing time, the simulation is only reliable up to 7-8kHz.

First, let's have a look at the radiation pattern with a dome without wave guide - only the tweeter simulated:
View attachment 75568
View attachment 75567

A certain similarity to the complete loudspeaker measured by @amirm cannot be denied:

View attachment 75569


Then the next thing we'll look at is what happens with a 3/8'' rounding - only the tweeter simulated:
View attachment 75571
View attachment 75572

This is certainly an improvement and should possibly work without adjusting the crossover.


Next consideration now would be to shift edge-diffraction most far to high frequencies, because then
a) the crossover remains free of interference
b) by using the small waveguide the radiation at high frequencies is still controlled and the edge diffraction is lower

First of all we lead the rounding as close as possible to the tweeter. The drivers have been moved upwards while maintaining their spacing (would have to be simulated in detail to see if this is really advantageous) - only the tweeter simulated:

View attachment 75573
View attachment 75574

That looks pretty good, the crossover-region at 1.8kHz is now completely interference-free in the radiation and the radiation of the woofer should not cause any problems anyway.

The edge-diffraction now causes us problems around 5kHz.

Our small waveguide (here the Seas-DXT instead of the T26SG used in the kit) should help us and tame the interference a little bit - only the tweeter simulated:
View attachment 75575
View attachment 75576
The optimization of the Encore kit is finished - it is as simple as that - please donate to @amirm , he needs a new handyman



But while we're at it, how would a complete loudspeaker with the SB17NAC plus Seas DXT as a tweeter simulate/measure with these dimensions?

Therefore we roughly simulate a crossover with [email protected]:
View attachment 75575
View attachment 75577

... and look at simulated end results:

View attachment 75579

Horizontal normalized sonogramm +-180°
View attachment 75580

Vertical normalized sonogramm +-180°
View attachment 75581

...and there goes the forum speaker

The only thing that interested me about these OLD loudspeakers was the woofer and its distortion. Waveguide is always a good idea. Better a good coaxial or ribbon tweeter with waveguide.

About the aluminum SB woofer, measurements:

SB Acoustics SB17NAC35-4
http://www.audioexcite.com/?page_id=5833
https://www.diyaudio.com/forums/multi-way/295732-sb-acoustics-sb17nac35-4-measurements.html

SB17NBAC35-4 vs SB17NAC35-4
http://www.audioexcite.com/?p=7353

 

[KaiserSoze]

Air likes to see smooth transitions, which is why good horn designs aren’t like a megaphone, take a look at some Avantgrade horns.

The same physics applies to the baffle, a flat edge isn’t great, chamfered is better, and roundover even more so. I also think cabinets with curved sidewalls help.

B&Ws teardrop tweeter design for instance is really good, super curved and slowly tapers to a point.

All good, but there is also a condition that must be satisfied, on the basis of the ratio of the wavelength to the overall dimension of the object (the roundoff radius), before the wave will take notice of the object. DIY speaker builders are haphazard with respect to this condition and in the assumptions they make as to the frequencies at which the roundoff of the corner will have any appreciable effect. A statement will often be encountered that indicates the appropriateness of a specific roundoff radius but this is done with indifference to the frequency or wavelength at which it is supposed to be effective. The roundoff radius has to be adequately large, in relation to the wavelength, in order for the rounding to have any appreciable effect at diminishing diffraction ripple. There needs to be a rule of thumb. According to Linkwitz, the radius needs to be greater than 1/8 of the wavelength to have any appreciable effect. To be particularly effective, the radius needs to be more like half the wavelength. A 3/8 inch roundoff will barely have any effect at all on frequencies below 4 kHz, and will only have a strong effect on frequencies outside the range of human hearing.

 

[ctrl]

Are you saying that the directivity mismatch is not attributable to the difference in the driver size and to the fact that the wavelength at the crossover point is roughly equal to the diameter of the woofer and more than 6 x greater than the diameter of the tweeter? Are you saying this, or are you saying that directivity mismatch is not a problem except when it is deemed a problem?

The different diameters of the sound sources pose no problem at the selected crossover frequency of 1.8kHz.
The simulation of an entire loudspeaker with 6'' woofer and 1'' tweeter in Post#80 shows this ([email protected]) - except the woofer used in the Encore kit would emit extremely unusual radiation, which I do not believe:

No directivity mismatch, no step in the FR off axis. By shifting the crossover frequency, the radiation can of course, within certain limits, still be changed.

For example, B&W chooses a very high crossover frequency for some models when using a 6.5'' woofer and thus consciously uses the narrowing of the woofer's radiation to obtain a dip in the power response in the 2-3kHz range - you could call this a "mismatch".

 

[Biblob]

Okay, there were some statements in the last posts that I can't understand - could partly be due to the translation.

Therefore I would like to show in a simplified way what is possible by changing the baffle, with unchanged cabinet dimensions - similar to the Philharmonic-BMR.

To keep my effort low, I use chassis simulations that are already on my hard disk. As woofer I use the SB17NAC35 and as tweeter the Seas-DXT, because the tweeter of the Encore also has a small waveguide. The cabinet dimensions are the same as in the Encore kit.

The fact that cancellations occur around the crossover frequency in the vertical radiation of vertically stacked drivers no longer needs to be explained, therefore the horizontal radiation is mainly considered.

If not stated otherwise, the normalized horizontal radiation pattern up to 90° is shown in 15° steps. To save computing time, the simulation is only reliable up to 7-8kHz.

First, let's have a look at the radiation pattern with a dome without wave guide - only the tweeter simulated:
View attachment 75568
View attachment 75567

A certain similarity to the complete loudspeaker measured by @amirm cannot be denied:

View attachment 75569


Then the next thing we'll look at is what happens with a 3/8'' rounding - only the tweeter simulated:
View attachment 75571
View attachment 75572

This is certainly an improvement and should possibly work without adjusting the crossover.


Next consideration now would be to shift edge-diffraction most far to high frequencies, because then
a) the crossover remains free of interference
b) by using the small waveguide the radiation at high frequencies is still controlled and the edge diffraction is lower

First of all we lead the rounding as close as possible to the tweeter. The drivers have been moved upwards while maintaining their spacing (would have to be simulated in detail to see if this is really advantageous) - only the tweeter simulated:

View attachment 75573
View attachment 75574

That looks pretty good, the crossover-region at 1.8kHz is now completely interference-free in the radiation and the radiation of the woofer should not cause any problems anyway.

The edge-diffraction now causes us problems around 5kHz.

Our small waveguide (here the Seas-DXT instead of the T26SG used in the kit) should help us and tame the interference a little bit - only the tweeter simulated:
View attachment 75575
View attachment 75576
The optimization of the Encore kit is finished - it is as simple as that - please donate to @amirm , he needs a new handyman



But while we're at it, how would a complete loudspeaker with the SB17NAC plus Seas DXT as a tweeter simulate/measure with these dimensions?

Therefore we roughly simulate a crossover with [email protected]:
View attachment 75575
View attachment 75577

... and look at simulated end results:

View attachment 75579

Horizontal normalized sonogramm +-180°
View attachment 75580

Vertical normalized sonogramm +-180°
View attachment 75581

...and there goes the forum speaker

Loool, you nailed it with these simulations. Love it.

 

[KaiserSoze]

Okay, there were some statements in the last posts that I can't understand - could partly be due to the translation.

Therefore I would like to show in a simplified way what is possible by changing the baffle, with unchanged cabinet dimensions - similar to the Philharmonic-BMR.

To keep my effort low, I use chassis simulations that are already on my hard disk. As woofer I use the SB17NAC35 and as tweeter the Seas-DXT, because the tweeter of the Encore also has a small waveguide. The cabinet dimensions are the same as in the Encore kit.

The fact that cancellations occur around the crossover frequency in the vertical radiation of vertically stacked drivers no longer needs to be explained, therefore the horizontal radiation is mainly considered.

If not stated otherwise, the normalized horizontal radiation pattern up to 90° is shown in 15° steps. To save computing time, the simulation is only reliable up to 7-8kHz.

First, let's have a look at the radiation pattern with a dome without wave guide - only the tweeter simulated:
View attachment 75568
View attachment 75567

A certain similarity to the complete loudspeaker measured by @amirm cannot be denied:

View attachment 75569


Then the next thing we'll look at is what happens with a 3/8'' rounding - only the tweeter simulated:
View attachment 75571
View attachment 75572

This is certainly an improvement and should possibly work without adjusting the crossover.


Next consideration now would be to shift edge-diffraction most far to high frequencies, because then
a) the crossover remains free of interference
b) by using the small waveguide the radiation at high frequencies is still controlled and the edge diffraction is lower

First of all we lead the rounding as close as possible to the tweeter. The drivers have been moved upwards while maintaining their spacing (would have to be simulated in detail to see if this is really advantageous) - only the tweeter simulated:

View attachment 75573
View attachment 75574

That looks pretty good, the crossover-region at 1.8kHz is now completely interference-free in the radiation and the radiation of the woofer should not cause any problems anyway.

The edge-diffraction now causes us problems around 5kHz.

Our small waveguide (here the Seas-DXT instead of the T26SG used in the kit) should help us and tame the interference a little bit - only the tweeter simulated:
View attachment 75575
View attachment 75576
The optimization of the Encore kit is finished - it is as simple as that - please donate to @amirm , he needs a new handyman



But while we're at it, how would a complete loudspeaker with the SB17NAC plus Seas DXT as a tweeter simulate/measure with these dimensions?

Therefore we roughly simulate a crossover with [email protected]:
View attachment 75575
View attachment 75577

... and look at simulated end results:

View attachment 75579

Horizontal normalized sonogramm +-180°
View attachment 75580

Vertical normalized sonogramm +-180°
View attachment 75581

...and there goes the forum speaker

This is vastly more meaningful than the article you posted previously, which revealed very little about the effect of diffraction in the off-axis response or the anticipated effect, in the off-axis response, of taking steps to mitigate diffraction.

I understand that trying to write in a language that isn't your native language is difficult to say the least. But what you are saying is now much clearer. I believe you are saying in essence this:

What appears to be a directivity mismatch in the off-axis response and is widely assumed to be a simple directivity mismatch is not so much a directivity mismatch as the effect of the ripple associated with diffraction at the baffle edge.

This is what you are saying, isn't it?

If this simulation is correct, then my preference is for a baffle shaped in the manner indicated in your simulation, in lieu of placing the tweeter in a waveguide. In any case the simulation gives you adequate reason to prefer diffraction ripple over simple directivity mismatch as the underlying cause of the irregularity in the off-axis response.

Personally, though, I regard these simulations as useful but I do not regard them as conclusive. One thing I do not like about your simulation is that the effects of the changes are shown as a change in the off-axis response relative to the on-axis response. This is confusing. No doubt it is useful for some purposes, but to my way of thinking this is not useful for this purpose. Not only do I desire to see how the on-axis response is affected by the change that is made, but I desire to see how the off-axis response is affected in the absolute, not in terms of the difference with respect to the on-axis response.

 

[ROOSKIE]

...Building one of those is the equivalent of trying to bake Wonderbread at home. Sure you can do it, but why?

Quite frankly DIY is not for everyone. Some folks are just fundamentally different from others. If "why" is your first instinct, doing a kit simply might not be for you. My first instinct is why not? I have to keep myself from over extending my desire to DIY. & really DIY is a way to share as in no way does the "Y" really fit. You are not doing this thing "yourself", There is a ton of sharing of skills, research, designs, experiments, and on and on. Every screw, every wire, every driver, every bottle of glue all of it, every tool involved masterfully created by others for our use in making a speaker- it is really mind blowing to connect dot after dot. This is a collaboration with the world. Super fun times for the right participant!

Plus really, Wonderbread? Start baking bread by making some good standard everyday sourdough. Yes you can buy bread at a reasonable price (and support those who make a living selling it) but you can NEVER make it yourself if you only buy it from someone else.

... I don't know the kit market well, but $250 intuitively sounds very expensive to me for 4 generic Indian-made plastic frame drive-units combined without any thought to integrating dispersion patterns, and what looks like a 4 or 5 component crossover...

You can make a great speaker with fairly inexpensive parts (This is what almost all manufacturers are doing). I can't say what the monetary value is of the GR kit. there have been many much more expensive products here measure worse. I can say there NOTHING wrong with a 4-5 component crossover. The design should be based off of performance not component count - EVER. Some drivers/designs need very little in way of added circuits to be smooth, others need many components. These are characteristics and nothing more.

Just to introduce you to the DIY speaker market a bit, various kits exist that run from very easy for a novice - to difficult for an experienced builder.
For more kits and an intro to some of the broader market, check on
DIY Soundgroup
https://www.diysoundgroup.com/
and Parts Express
https://www.parts-express.com/cat/speaker-subwoofer-kits/286
and Madisound
https://www.madisoundspeakerstore.com/speaker-kits/
and Meniscus
https://meniscusaudio.com/product-category/speaker-kits/
There are many, more.

...I also get the idea of wanting to build something just to do it, but by the same token one would think a person values her time enough to do so when the result is something not easily purchased. That doesn't mean "expensive," it means "different."...

Take gardening, I can buy tomatoes. I can buy cucumbers. I can buy flowers, why garden?
Why paint when you can buy a print of a masterpiece at Target now? Why play the piano when I can listen to a master off Tidal streaming at will?

These questions have no real answer IMHO. Really everything has been done before. Nothing is really unique or different or special unless you personally find it so.
There are people who dedicate themselves to climbing Everest and others who would rather be lounging in a hammock reading a book about Everest and dozing in summer breezes. Both activities potentially offer a rich experience.

That GR kit is pretty basic and straight forward, a level up from true beginner as it does require very, very basic woodworking skills. (or a good pal that has them to help you) Who ever assembles it will be guaranteed "something". Hopefully the journey of making, the experience of it, was a challenge worthy of their time.

To wrap up this post, as said in my previous post, I do enjoy buying "complete" products and I also enjoy DIY.
One really big benefit of DIY is that while fun, it is even more humbling. That "blood, sweat, tears" humbling can really temper the sense of entitlement that often comes up in such a consumer oriented culture.
Don't get me wrong I still enjoy be critical of products and designs, breaking them down - adding them up, (there is a lot of crud out there) but I have much more respect for the whole value of what we have available and how much work it all has taken.

 

[Thomas_A]

Okay, there were some statements in the last posts that I can't understand - could partly be due to the translation.

Therefore I would like to show in a simplified way what is possible by changing the baffle, with unchanged cabinet dimensions - similar to the Philharmonic-BMR.

To keep my effort low, I use chassis simulations that are already on my hard disk. As woofer I use the SB17NAC35 and as tweeter the Seas-DXT, because the tweeter of the Encore also has a small waveguide. The cabinet dimensions are the same as in the Encore kit.

The fact that cancellations occur around the crossover frequency in the vertical radiation of vertically stacked drivers no longer needs to be explained, therefore the horizontal radiation is mainly considered.

If not stated otherwise, the normalized horizontal radiation pattern up to 90° is shown in 15° steps. To save computing time, the simulation is only reliable up to 7-8kHz.

First, let's have a look at the radiation pattern with a dome without wave guide - only the tweeter simulated:
View attachment 75568
View attachment 75567

A certain similarity to the complete loudspeaker measured by @amirm cannot be denied:

View attachment 75569


Then the next thing we'll look at is what happens with a 3/8'' rounding - only the tweeter simulated:
View attachment 75571
View attachment 75572

This is certainly an improvement and should possibly work without adjusting the crossover.


Next consideration now would be to shift edge-diffraction most far to high frequencies, because then
a) the crossover remains free of interference
b) by using the small waveguide the radiation at high frequencies is still controlled and the edge diffraction is lower

First of all we lead the rounding as close as possible to the tweeter. The drivers have been moved upwards while maintaining their spacing (would have to be simulated in detail to see if this is really advantageous) - only the tweeter simulated:

View attachment 75573
View attachment 75574

That looks pretty good, the crossover-region at 1.8kHz is now completely interference-free in the radiation and the radiation of the woofer should not cause any problems anyway.

The edge-diffraction now causes us problems around 5kHz.

Our small waveguide (here the Seas-DXT instead of the T26SG used in the kit) should help us and tame the interference a little bit - only the tweeter simulated:
View attachment 75575
View attachment 75576
The optimization of the Encore kit is finished - it is as simple as that - please donate to @amirm , he needs a new handyman



But while we're at it, how would a complete loudspeaker with the SB17NAC plus Seas DXT as a tweeter simulate/measure with these dimensions?

Therefore we roughly simulate a crossover with [email protected]:
View attachment 75575
View attachment 75577

... and look at simulated end results:

View attachment 75579

Horizontal normalized sonogramm +-180°
View attachment 75580

Vertical normalized sonogramm +-180°
View attachment 75581

...and there goes the forum speaker

Looking close to the effects of the 3/8 rounding of the edges, there is only tiny differences compared to the original. There is still a lot more energy around 2-5 kHz compared to 1-2 kHz.

Changing the relative baffle size around the tweeter vs. woofer using round/large slanted shapes is a way to deal with the problem, which is related to baffle size. It is not until you provide a wave-guide you get a smooth response all the way - and then you have in practice matched the directivity difference between the wofoer and tweeter.

All in all, you don't fix the directivity problem just by doing some 3/8 rounding of the edges.

 

[ta240]

....I also get the idea of wanting to build something just to do it, but by the same token one would think a person values her time enough to do so when the result is something not easily purchased.

I get a kick out of the "my time is worth more than that" argument against DIY. Do people that say that weigh everything they do as to the time/cost benefit? Do they not spend any of their time doing things that result in absolutely no increase in productivity? I completely understand that DIY isn't for everyone and many would even find it tedious and possibly unpleasant; but that could be said about a lot of hobbies and even sports. "you could just wait until the other team goes home and then carry the ball to the other side of the field". Likewise there are people that get enjoyment out of the process of building and not just building but making the next build better than the last. Some people sip expensive scotch and stare off into space to relax; I solder and glue things together. Some watch golf on TV... my time is worth more than that

.... Building one of those is the equivalent of trying to bake Wonderbread at home. Sure you can do it, but why?

Unless someone is a born with advanced abilities in every field they generally have to start somewhere with the learning process. People probably don't start out trying to recreate wonderbread at home but they usually start with simple recipes and move to more complex ones. As Rooskie said this is a step up from a flatpack kit; an inexpensive step into building your own enclosures.

 

[amirm]

Do people that say that weigh everything they do as to the time/cost benefit?

I spent $1,000 on compost to amend the soil in our garden so I can plant vegetables. If I get $100 out of the harvest, it would be good.

 

[thebabyparrot]

I have two pairs for sale.

Currently looking to get my very own Phil 1's. However, how are they? Do they measure well? I'd be interested to see a spin-o-rama .

 

[KaiserSoze]

The different diameters of the sound sources pose no problem at the selected crossover frequency of 1.8kHz.
The simulation of an entire loudspeaker with 6'' woofer and 1'' tweeter in Post#80 shows this ([email protected]) - except the woofer used in the Encore kit would emit extremely unusual radiation, which I do not believe:
View attachment 75587
No directivity mismatch, no step in the FR off axis. By shifting the crossover frequency, the radiation can of course, within certain limits, still be changed.

For example, B&W chooses a very high crossover frequency for some models when using a 6.5'' woofer and thus consciously uses the narrowing of the woofer's radiation to obtain a dip in the power response in the 2-3kHz range - you could call this a "mismatch".

Certainly I agree that your simulations give you reason to believe that there is no directivity mismatch, per se, between the 6.5" woofer and the small tweeter, even though the wavelength at the interface is almost exactly the same as the diameter of the woofer and is more than six times greater than the diameter of the tweeter.

As a matter of fact, your graph here, obtained from your simulation, shows a very significant decrease in the tweeter dispersion by the point in frequency where the wavelength is still several times greater than the diameter of the tweeter. Let us say, at wavelength 3 x greater than the tweeter diameter, at 4.5 kHz, the tweeter is already revealing the decrease in dispersion. (This is plainly evident in most actual measurements of actual speakers, but it is somewhat less apparent in your graph, for reasons that I won't try to sort out.) The obvious question is why the same physical limitations, based in the ratio of wavelength to piston diameter, are not evident in your graph as it applies to the woofer? A similar effect ought to be apparent for the woofer by 900 Hz at the most (allowing for the actual piston diameter to be 5" and not 6.5"). The question is obvious: why isn't this evident?

It occurs to me that three distinct questions are being muddled here, not by anyone's express intent, but by circumstances. There is the somewhat theoretical question of what the directivity pattern of each driver would be, operating by itself on a flat baffle with the same dimensions as the actual baffle of this speaker. There is the question of what the off-axis response looks like for the two drivers mounted together, which we have seen. Then the third question: what the off-axis response looks like for the two drivers mounted on a highly modified baffle and with the tweeter placed within a waveguide.

This occurs to me: it is within the realm of possibility that the changes you make to the baffle in your simulations compensate for the inherent directivity mismatch of the two drivers on the flat baffle with the tweeter flange flush with the baffle. This could not easily be ruled out, and as such, is it logically valid to infer from your simulations that there is no directivity mismatch? Please use caution when addressing this question.

 

[KaiserSoze]

Loool, you nailed it with these simulations. Love it.

And if the very substantial changes he applied in the simulation compensate for the inherent directivity mismatch, it follows logically that there isn't any directivity mismatch? Right?

 

[KaiserSoze]

Looking close to the effects of the 3/8 rounding of the edges, there is only tiny differences compared to the original. There is still a lot more energy around 2-5 kHz compared to 1-2 kHz.

Changing the relative baffle size around the tweeter vs. woofer using round/large slanted shapes is a way to deal with the problem, which is related to baffle size. It is not until you provide a wave-guide you get a smooth response all the way - and then you have in practice matched the directivity difference between the wofoer and tweeter.

All in all, you don't fix the directivity problem just by doing some 3/8 rounding of the edges.

Well said. The changes that occur with mere 3/8" rounding are very small. And when making the major, ambitious changes that he made, it seems logically questionable to take a position that asserts that there was no directivity mismatch. If you can make something go away, does this mean that it did not exist? If you really wanted to prove that there was no directivity mismatch, you would have to measure the dispersion of each driver independently, each on the flat baffle with sharp edges, and show that at the crossover point they are matched in directivity.

However it is a different question to ask whether the major irregularities in the off-axis response of the speaker are attributable to the directivity mismatch per se. IF you could prove conclusively that the primary cause of the off-axis response irregularity is something else, i.e., edge diffraction, then you would have a compelling argument that directivity mismatch is not the primary cause. That is, if you can prove that the primary cause of some effect is A, it follows logically that the primary cause cannot be B. Okay, but did he prove conclusively that edge diffraction is the primary cause of the off-axis response irregularity? No. I think he probably did not clearly realize that this is what he would need to do, to produce a logically correct argument that directivity mismatch is not the primary cause.

 

[KaiserSoze]

I spent $1,000 on compost to amend the soil in our garden so I can plant vegetables. If I get $100 out of the harvest, it would be good.

May all your tomatoes be vibrant red, mouthwatering and sweet.

 

[amirm]

May all your tomatoes be vibrant red, mouthwatering and sweet.

They have been the best we have grown! It is a "high-end" compost with fish meal and such.

 

[ctrl]

If this simulation is correct,

The simulation is very accurate as long as the participating chassis behave "ideally".
The simulation for a "soft" plastic cone or for a huge fabric midrange dome will not match reality as well as the simulation of a Be tweeter, because my simulations assume ideal drivers.

Here is a project where I simulated the complete loudspeaker in advance, compared to measurements of the finished loudspeaker - to high frequencies it becomes less accurate, because I wanted to save computing time again (my 4-core CPU likes to calculate 6 hours for such a simulation)
https://www.diy-hifi-forum.eu/forum/showthread.php?19868-El-Grico&p=282530&viewfull=1#post282530
(Please note the scaling)

What appears to be a directivity mismatch in the off-axis response and is widely assumed to be a simple directivity mismatch is not so much a directivity mismatch as the effect of the ripple associated with diffraction at the baffle edge.
This is what you are saying, isn't it?

Yes, the radiation pattern is due to the interaction of the drivers with the baffle.

One thing I do not like about your simulation is that the effects of the changes are shown as a change in the off-axis response relative to the on-axis response. This is confusing. No doubt it is useful for some purposes, but to my way of thinking this is not useful for this purpose. Not only do I desire to see how the on-axis response is affected by the change that is made, but I desire to see how the off-axis response is affected in the absolute, not in terms of the difference with respect to the on-axis response.

Normalized to the on-axis frequency response shows you the absolute FR off-axis. Imagine you manage to create a dead straight on-axis FR during crossover tuning, then you have exactly what the on-axis normalized diagrams show you.

You just have to be incredibly careful not to misinterpret them, when compared to real loudspeaker. The edge diffraction is always accompanied by a dip on axis - if no attempt is made to straighten it via the crossover. As a result, the off-axis FR shows usually no or only a small sound pressure increase in the affected frequency range.

Normalized to on-axis

The normalization to the axis frequency response simply shows best whether the radiation is uniform over all angles.

For example, you can also normalize to 30°, then it doesn't look so serious, but that doesn't change the fact that the reflections of the 0° FR tonal don't match the 30° FR.

All three diagrams show basically the same thing, but with different degrees of clarity.

... and one cannot emphasize it often enough, just because a loudspeaker radiates more evenly does not automatically mean it sounds better, because that depends on the fine-tuning of the crossover.