Tech discussion about new Indiq speakers

Vineethkumar01

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Hi

Have anyone auditioned these new Indiq speakers:
1657506560559.png 1657506583748.png

Let me say why I am interested in them. Because they follow a (golden reference) 2 way bookshelf design philosophy (except maybe a teensy bit about a protruding edge at the top. But that may not be an issue for this specific tweeter which doesn't radiate as wide to edges compared to some others) .. :)

Flush mounted edges and chamfered cabinet lowers diffraction not only at high frequencies but also to lower frequencies.. This is because a curved cabinet itself can act as a waveguide with possibility of maintaining directivity control from the top all the down to the midrange frequencies.. :) (anybody interested may look at Revel M 105 curved cabinet speakers' measurements to see how that happens. Other advantage as they mention is improvement in rigidity and lowered standing wave modes.

Now comes an even more important part, the crossover. In the above ad, it says 2.8 kHz and 3.3kHz in the two speakers?
Why is it important? Because of Kimmosto's c-c rule for crossover.. :)
In short, the rule is that for farfield listening, the center-center driver spacing should be 1-1.4 x wavelength at crossover. This will result in a uniform/even power response in room. For a 1inch tweeter and a 5.25 inch midwoofer, the lowest possible separation is about 130mm between the drivers. From the pics, it looks like 140+ ish mm. This means that per Kimmosto's rule, the ideal crossover frequency range is somewhere in between 2400 - 3400kHz (depending upon the crossover topology and comfort level of drivers in this range). Isn't crossover frequencies in this range exactly the ones we see in the specs.. ;)
Then comes the clever tuning frequency of the port, tuned up rather high compared to typical 30 Hz ish tuning small speakers. This may give better sensitivity and cleaner power handling capabilities if designed properly... Expecting thundering bass from small bookshelves by tuning it low is nonsense. Hence this tuning a bit higher approach works..

Due to all these reasons, I am excited about these speakers. Now we are knocking at the doors of designs from world class speaker designers.. :)
I have been the one who started a ruckus in the past on this forum when a saw a relatively bad design philosophy.. Well I will be the first one to appreciate a good trend in speaker design.. Now I am even interested in hearing these speakers.. :)
I wish all the best to their new product line. Hope people will find it sounding good too. Hence I am interested to know feedback from people who have heard in person..
PS: In future, I hope they do something (baffle) like in below pic, but with their curved cabinet. That would be adopting a truly world class design philosophy (Below pic is the actual one designed by Kimmosto :) )
1657507816572.png


Thanks
Vineeth
 

keith_correa

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This is because a curved cabinet itself can act as a waveguide with possibility of maintaining directivity control from the top all the down to the midrange frequencies..
I'm interested in knowing how curved sides act as a waveguide and affect directivity for frequencies mid upwards. And I'm not referring to a spherical shaped enclosure here but like in the speakers referred to, just a curved sided enclosure.
(anybody interested may look at Revel M 105 curved cabinet speakers' measurements to see how that happens.
I've looked but cannot find anything to show how this happens and it is possible that I've not looked hard enough. I'd appreciate if you can kindly spoon feed me and point me towards measurements showing this.
Other advantage as they mention is improvement in rigidity and lowered standing wave modes.
The stiffness (which is desirable) of the curved panels is more if the panels are made of wood and this is because of increased tension depending on the method employed to attain the curved panels. Is this the rigidity that you are referring to?
Also, I think if the walls in a curved panel were not covered with an absorbent material, then yes, there would be some effect of lowering of standing waves due to the curve, but if the walls were covered with absorbent in curved and flat panels, then the effect is a moot point - the lowering would be almost identical.
Then comes the clever tuning frequency of the port, tuned up rather high compared to typical 30 Hz ish tuning small speakers.
I think what they've done is good but in my opinion not particularly clever. Of course, it also depends on what you and I consider "clever". For example, in the mid-1990's, Ken Kantor designed the NHT SuperZero - a tiny bookshelf speaker. Now, that realistically could not produce any bass worth mentioning and it didn't, but what Ken did is to tune the cabinet to produce a bump at the "knee". This resulted in bass (if you can call it that) and then people who used them without a sub were happy too. Now, THAT was clever at that time and that "technique" is now common place. :rolleyes:
 
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Vineethkumar01

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I'm interested in knowing how curved sides act as a waveguide and affect directivity for frequencies mid upwards. And I'm not referring to a spherical shaped enclosure here but like in the speakers referred to, just a curved sided enclosure.
Here is a starting point.. :D
Patrick Bateman's posts in above thread were the ones that started the investigation into this idea. He also explains some of it with Revel M106 speaker as an example. Subsequently, many people have experimented with these kind of things and the common consensus nowadays is that cabinet shaping is one of the important factors in directivity control at lower frequencies. We had explored this in my own 3-way speaker design thread using BEM simulations.

The idea is that not only the baffle but also the entire cabinet acts like a "waveguide". Controlling low frequency diffraction properly is what yields the low frequency directivity control. Often, in the past, when people referred to diffraction, almost all its effects were thought of as manifesting at higher frequencies (in the crossover range between mid-tweeter in a 2 way and tweeter frequency range) and were thought to be brought about by dimensions and geometry of the baffle.
One of the most common diffraction effects that is put in this (baffle-only affected) category is the "baffle step", where the radiation transitions from 2pi to 4 pi steradians. This was partly due to the focus on only on-axis measurements, which doesn't show the complete picture. However, with recent use of polar maps of frequency response, we can see that the baffle step is a (gradual) transition in the directivity response which is also significantly (and in a complicated way) affected by the cabinet depth, cabinet width, and overall cabinet geometry.

Here is a simple example of the impact of cabinet width and depth on horizontal directivity of a 5.25inch midwoofer from my own speaker thread on diyaudio. The cabinet geometry under investigation is 30cm wide, with variable depth and not having curved sides). Observation point for taking directivity measurements is 105cm up from the base of the cabinet on tweeter axis. The below picture shows wavefront propagation at 400Hz in all 3 dimensions together. Darker the color, stronger the amplitude.
1657538940784.png

Normalized horizontal directivity plots of the midwoofer from above cabinet is shown below.
Plot-1 below shows the results for a 30cm wide, 20cm deep cabinet. Plot-2 below shows the same for a 30cm wide, 40cm deep cabinet.

1657539395406.png



Now compare the 100Hz to 1kHz range in both the above plots. We can see that the 20cm deep cabinet (top plot) is much more smooth/uniform in terms of those peaks and valleys in directivity compared to the 40cm deep one (bottom plot) :)

After the above and much more experiments, we concluded that if the sound was guided along the walls of the cabinet (smooth transition, gentle curved walls) instead of the boxy cuboidal shape which causes abrupt transitions, the directivity plot will vary smoothly till lower midrange due to lowering of low frequency diffraction. This can sort of now be seen in the Revel M 106 horizontal polar measurements :D

:)

The increased stiffness (which is desirable) of the curved panels is more if the panels are made of wood and this is because of increased tension depending on the method employed to attain the curved panels. Is this the rigidity that you are referring to?
Also, I think if the walls in a curved panel were not covered with an absorbent material, then yes, there would be some lowering of standing waves due to the curve, but if the walls were covered with absorbent in curved and flat panels, then the effect is a moot point - the lowering would be almost identical.
Yes you are right in both cases.. :) Stiffness increase is what I was thinking about. I thought they might be using thin layers of bent plywood or something similar to create that curved shape. Basically panels held together in tension. If they achieved it, it is good. If not, at least it looks good for the eyes and may have directivity benefits. :)
Yes. As you pointed out, standing wave reduction can also be achieved with judiciously chosen and judiciously placed absorbent material in the cabinet. Need not always go for a curved shape for standing wave reduction alone.

I think what they've done is good but in my opinion not particularly clever. Of course, it also depends on what you and I consider "clever". For example, in the mid-1990's, Ken Kantor designed the NHT SuperZero - a tiny bookshelf speaker. Now, that realistically could not produce any bass worth mentioning and it didn't, but what Ken did is to tune the cabinet to produce a bump at the "knee". This resulted in bass (if you can call it that) and then people who used them without a sub were happy too. Now, THAT was clever at that time and that "technique" is now common place. :rolleyes:
Maybe the definition of 'clever' that I was thinking about while writing this is different.. Or I didn't put much thought into that word while using it :D
In general, I keep seeing many small speakers tuned lower than they should be with claims of port tuning/speaker being able to reach down in the 30s of Hz. Even if they go that low, ultimately how much power the speaker can take and how much SPL it can put out with less distortion at those low frequencies is what will matter, in my opinion. Yes it depends on other factors also and we need to look at the driver specs and cabinet volume to be more thorough. But tuning a small driver in a sensibly chosen bass reflex alignment (if they have done it properly) is refreshing to see.. :)
But unless we have data, I see no point in discussing further about this.. :D

Regards
Vineeth
 

Vineethkumar01

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For those not interested in the technical side of things mentioned above, especially the directivity control aspect in the 300-1kHz range, here is its impact in perceivable effects.roughly 300 to 600-700 Hz range is where the "body" of the vocals are supposed to lie in.
So directivity control in this range offers two benefits in general:

1) less cabinet induced colorations in the "vocal" range. If you see the directivity charts above you can see the peakiness in the response caused in this range of frequencies by the box dimensions. Having directivity control in this range therefore helps in more natural vocals

2) Less room dependent colorations without room treatment. More the directivity control, less the sound hitting boundaries and then getting the colorations imparted by it. Again this helps in more "natural" vocals.

Well if one likes the "colorations" all is well with any cabinet size, shape and geometry. But for those obsessed with having as less "colorations", as possible, all this directivity control thingies can help offer peace of mind howmuch ever less extent it is.. :D

Well, as with all, there maybe minor tradeoffs, but lets not go into that now.. :)
 

keith_correa

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Here is a starting point.. :D
Thanks for this!
After the above and much more experiments, we concluded that if the sound was guided along the walls of the cabinet (smooth transition, gentle curved walls) instead of the boxy cuboidal shape which causes abrupt transitions, the directivity plot will vary smoothly till lower midrange due to lowering of low frequency diffraction. This can sort of now be seen in the Revel M 106 horizontal polar measurements :D
Where did you get this conclusion from? Who is "we"? You and others or is that something Patrick said in that thread?
I'm confused because I see that in post # 13 in that thread, Patrick says:
"Curving and tapering the sidewalls seems to make nearly no difference, so I'm guessing it's largely cosmetic. I was a bit surprised by this, because nearly all of the Revel line has a trapezoidal shape. Perhaps the idea is to make the speaker look less imposing."
 

Vineethkumar01

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Where did you get this conclusion from? Who is "we"? You and others or is that something Patrick said in that thread?
I'm confused because I see that in post # 13 in that thread, Patrick says:
"We" includes me (who didn't do much useful work and only stared at graphs other created) and others who helped me in my own project.
The major determinants of low frequency directivity control is the ratio of width of the cabinet to its depth and the amount of "rounding/chamfereing" at all places in the cabinet including the back. The width-to-depth relation impact part of is clearly shown in sims in above thread.
That a rounded/tapering shape to the back of the cabinet like a curve or a triangle has an impact on the diffraction/directivity was shown by tmuikku using ripple tank simulations etc in the last year or so. It is buried somewhere in that forum. But it will be still there.. :D
ASR directiva v2 thread or some similar one also has pointers somewhere in it where FM cntrl shows a cleverly designed low depth, rounded cabinet with which he was able to get directivity control down to lower midrange. :)

While we are on the topic of directivity control using cabinet shaping, here is an excellent example of how to do it the right royal way from none other than Kimmosto :D
I would seriously encourage anyone interested in these aspects to please go through this build:
Look at its directivity control from the 0-120 degree off axis measurements graph. And look at the shape of the cabinet too. It is like a smoothed out diamond shape :)
Please also read his subjective interpretations of this speaker at the end of the thread.
Commercial offerings that employ similar yet different design philosophy include Sonus faber Ellipsa/Stradivari and from the diy world: http://www.troelsgravesen.dk/PMS-EXCEL.htm

Mods may please move/remove my posts if it is not relevant to this thread.

Thanks
Vineeth
 

Silencer

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Looks like folks at Indiq have nailed it this time.

And Amit has kept his word by listening to the criticisms and came up with an improved design.

Frankly I didn't like the old boring boxy design.
This new iterations are really appealing.​
 

Vineethkumar01

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Looks like folks at Indiq have nailed it this time.

And Amit has kept his word by listening to the criticisms and came up with an improved design.

Frankly I didn't like the old boring boxy design.
This new iterations are really appealing.​
I personally appreciate the overall design direction that they have taken. But due to the lack of any objective data along with my own listening impressions, I am unable to say anything concrete about this whole thing..

So let your own ears be your guide.. If it sounds good to you on the musical genres you listen to at high and low SPL levels, then probably that is all what matters.. :)
 

Vineethkumar01

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@keith_correa :
Here are more sims about the effect of cabinet shaping from some sims that FM fluid had done long back :):
In the above post, the pics show obvious advantages at higher frequencies for shaped cabinets.
If we compare the below 1kHz directivity, we can see that small straight line ish nature of the off axis curves for the elliptical cabinet compared to the slightly "bunching" curves with square box, both boxes of the same depth and width. :)
 
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