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Old 27th April 2010, 04:06 AM   #11
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21" tall, 4" wide, and 6" deep, comprising 8 drivers with group delay steering:

http://www.jblproservice.com/pdf/CBT/CBT50LA-WH.pdf

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Old 28th April 2010, 09:47 AM   #12
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Looking at the JBL speaker in the link, I tried something very similar a few months ago:
+ 8 x 3.3" drivers (Visaton FRS8, not exactly the cheapest at around 10 EUR)
+ narrow open baffle

I tried a lot of configurations including: all full range, power tapering, response shaping of the outer drivers (as in the JBL speakers above) and a super tweeter in the middle. The speaker measured quite good in terms of both FR(apart from comb filtering, of course) and polar response but...

...it just did not sound right.

Compared to my classic 2way (7" mid, 1"tweeter) open baffle panels, it was worlds away in all departmens. Yest, it sounded balanced as if the polar response was quite good, but my guess is that direct sound we hear in mid-highs counts a lot and that was not so good (possible drivers themselves + time differences)

I was hoping to have a more stable image as I heard it should be the case with line arrays and I am not the kind of listener that stays in a small spot. It was the other way round, scene collapsed quickly as I moved around a few inches.

Possible reasons for my failure:
+ line arrays are hard to get right - given the effort I put into this, I am not interested in wasting my time further to "get them right". Maybe it's me, though
+ maybe a full ceiling to floor array would be better - at this point, not willing to try

Overall, not my cup of tea and I wanted to share this with you guys: I am not saying it is not worth a try, but if you jump into it, be aware you might also be disappointed.

It looks like at least in a normal domestic environment, you can get better performance with less effort using a classical arrangement (woofer+tweeter)

My story refers exclusively to open baffle, so take it with a grain of salt. I remember MJK, I think, suggested once that an open baffle array would not be worth the effort and complexity: I give him right now.


PS: that JBL speaker seems to be designed rather for PA, not hi-fi. Clearly, for PA a line array would indeed do a terrific job.

HTH.
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Old 28th April 2010, 10:46 AM   #13
soongsc is offline soongsc  Taiwan
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Basically, the less drivers you can get the SPL and bandwidth you need, the better off you are.
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Old 28th April 2010, 01:38 PM   #14
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One more thing: my experience/comments above are related exclusively to arrays of fullrange drivers.

It might be very well that a well engineered multi-way array (proper separation distances between drivers according to the reproduced frequency) is vastly superior in terms of sound quality. But also more difficult and expensive to build.
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Old 28th April 2010, 01:56 PM   #15
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Default Array made right!

Have a look at the picture on the left please. That is a line array but not the curved type or open baffle or just midrange as it is from 80Hz-20kHz, -3dB at 80 and -0 at 20kHz. This speaker is as good as it gets in my experience. 14 amplifiers for just the speaker shown (1250 watts total for one speaker) and active control of the beam with this one a directivity index of 10 and THD of less than 0.1% at 100dB. And the sound... all say the same thing, a level of clarity and dynamics only heard on this speaker. Peak SPL from is 127dB from the one speaker shown.

Arrays are one of my personal goals however cheap attempts just do not sound very good as many say. Please do not dis the design concept as it is IMHO one of the best available. Yes, quite expensive!
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Old 29th April 2010, 02:02 PM   #16
Elias is offline Elias  Finland
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Hi,

I have also done line array with 8 * FRS8. I've been also using FRS8 as a single driver configuration. The conclusion was that FRS8 is not a 'perfect' driver and it has serious limitations at the top end. How good a 3.3" tweeter can sound like? On the other hand there may be better 3.3" drivers out there.

In contrary however, the line array up to 20kHz is not a bad idea at all, but it is better to be done by other means than stacking 3.3" drivers. A long ribbon array for example works much better, as I have found by experimenting.


- Elias



Quote:
Originally Posted by bzfcocon View Post
Looking at the JBL speaker in the link, I tried something very similar a few months ago:
+ 8 x 3.3" drivers (Visaton FRS8, not exactly the cheapest at around 10 EUR)
+ narrow open baffle

I tried a lot of configurations including: all full range, power tapering, response shaping of the outer drivers (as in the JBL speakers above) and a super tweeter in the middle. The speaker measured quite good in terms of both FR(apart from comb filtering, of course) and polar response but...

...it just did not sound right.

Compared to my classic 2way (7" mid, 1"tweeter) open baffle panels, it was worlds away in all departmens. Yest, it sounded balanced as if the polar response was quite good, but my guess is that direct sound we hear in mid-highs counts a lot and that was not so good (possible drivers themselves + time differences)

I was hoping to have a more stable image as I heard it should be the case with line arrays and I am not the kind of listener that stays in a small spot. It was the other way round, scene collapsed quickly as I moved around a few inches.

Possible reasons for my failure:
+ line arrays are hard to get right - given the effort I put into this, I am not interested in wasting my time further to "get them right". Maybe it's me, though
+ maybe a full ceiling to floor array would be better - at this point, not willing to try

Overall, not my cup of tea and I wanted to share this with you guys: I am not saying it is not worth a try, but if you jump into it, be aware you might also be disappointed.

It looks like at least in a normal domestic environment, you can get better performance with less effort using a classical arrangement (woofer+tweeter)

My story refers exclusively to open baffle, so take it with a grain of salt. I remember MJK, I think, suggested once that an open baffle array would not be worth the effort and complexity: I give him right now.


PS: that JBL speaker seems to be designed rather for PA, not hi-fi. Clearly, for PA a line array would indeed do a terrific job.

HTH.
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Old 2nd May 2010, 01:31 PM   #17
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by Elias View Post
Hi,

..I have also done line array with 8 * FRS8. I've been also using FRS8 as a single driver configuration. The conclusion was that FRS8 is not a 'perfect' driver and it has serious limitations at the top end..

In contrary however, the line array up to 20kHz is not a bad idea at all, but it is better to be done by other means than stacking 3.3" drivers. A long ribbon array for example works much better, as I have found by experimenting.


- Elias
Hi Elias,

Agree, IMO, short arrays using 3-inch FR drivers sounds bad above 3 kHz where the vertical dispersion suddenly becomes huge even if the real driver is narrowing the upcoming secondary lobes.

FYI: This can be clearly being seen and estimated using a point source simulation: see picture (1)

b
Attached Images
File Type: gif 8x3.3inch-arr.GIF (174.6 KB, 1145 views)
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Old 2nd May 2010, 01:38 PM   #18
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by sumaudioguy View Post
Have a look at the picture on the left please. That is a line array but not the curved type or open baffle or just midrange as it is from 80Hz-20kHz, -3dB at 80 and -0 at 20kHz. This speaker is as good as it gets in my experience. 14 amplifiers for just the speaker shown (1250 watts total for one speaker) and active control of the beam with this one a directivity index of 10 and THD of less than 0.1% at 100dB. And the sound... all say the same thing, a level of clarity and dynamics only heard on this speaker. Peak SPL from is 127dB from the one speaker shown.

Arrays are one of my personal goals however cheap attempts just do not sound very good as many say. Please do not dis the design concept as it is IMHO one of the best available. Yes, quite expensive!
Hi

’ Array made right!’

Of course all arrays built by DIY’rs are right but this example looks for me like a typical first short array design-shot where the performance numbers given supplied are colored with a grain of wishful thinking. Note: I don’t dismiss the DIY’rs subjective impression when he is stating: ‘It sounds good’ as this is just an opinion based on unknown preferences.


Just for fun: Cloning an avatar-array: See picture (2)

b

Ps: Earlier treads dealing with similar subjects:

Line Array question

Beyond the Ariel


http://www.diyaudio.com/forums/attac...amp=1179074994
Attached Images
File Type: jpg avatar-test-clone.JPG (628.7 KB, 1143 views)
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Old 2nd May 2010, 04:32 PM   #19
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Default Plots have nothing to do with my array made right

Quote:
Originally Posted by bjorno View Post
Hi

’ Array made right!’

Of course all arrays built by DIY’rs are right but this example looks for me like a typical first short array design-shot where the performance numbers given supplied are colored with a grain of wishful thinking. Note: I don’t dismiss the DIY’rs subjective impression when he is stating: ‘It sounds good’ as this is just an opinion based on unknown preferences.


Just for fun: Cloning an avatar-array: See picture (2)

b
<snip>
Well those plots and graphs are interesting but have nothing to do with this array. Each driver has its own amplifier because each driver has a different signal than the driver adjacent to it. The signal applied is derived from methods similar to "synthetic aperture" radar antenna systems. All those custom drivers have the same phase (plus/minus 10 degrees in the pass band) and frequency response on axis and 30 degrees off axis. The result is a coherent 60 degree wide beam horizontally and this particular synthetic aperture is 12 degrees vertical providing a directivity gain of 10dB.

All the data presented was measured and not some guess or colored by happy thoughts. This is not a bunch of drivers all hooked in parallel. It is a very sophisticated system with lots of DSP and custom everything from the amps, So just how "good" can a chip amp be ? , drivers, power supplies, and the whole line level to transducer system. The goal was to make a speaker system that had significantly lower distortion than the ear and that was achieved with this setup. There are 5 subs to go with this using the same methods which go down to +3 at 20Hz and plus/minus 2dB from 25Hz to 120Hz.

One thing which seems to occur to often on DIY audio is someone comes along and says "what this guy claims is impossible." Just do not get the point of this. How about instead "How did you do this" rather than claiming authority and expertise to then disqualify some other persons accidental of intentional excellent results? I accept everyone's word until they are shown wrong or are clearly making wrong conclusions, as in this example, bjorno intentions I am certain were good but the conclusions are based on incorrect assumptions on the workings of this array. The system has been used by hundreds of different engineers from all over the world and almost without exception all say at the very least it sounds really good. Subjective, yes. Sounding very good, very likely. It is the best I have ever heard.

-SUM
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Old 2nd May 2010, 09:01 PM   #20
jcx is offline jcx  United States
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in the curved array the physical geometry provides the phase shift - only amplitude "shading" is needed - parallel/series diriver combinations are used in some of the physical prototype curved CBT arrays that exist so that they can be driven with a single standard audio power amplifier
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