Bjorno said:
Bjorno!
Thank you for the very detailed investigations! I'm afraid my level of skills is not quite high enough to fully understand it all, but I do think I got most of it.
The Rila speaker might very well be a poor choice, it is the very cheapest 5,25" driver I have found in Sweden.
The reason I thought about these 5,25" drivers and a 2580 Hz crossover was because on page 16 in James R. Griffin's paper, it sais that 2582 Hz is the maximum, with 130mm C-c distance, to avoid "increasing directivity" and "comb lines".
I'm not saying that anyone of you are wrong, but you seem to tell me something else, or do you mean that the crossover must be at a much lower frquency since it only falls with 12 dB/oct?
The tip about the wave guide is very interesting!
3" woofers sound like a good idea, but to reach 70% of my ceiling height, I would need about a 1.75m array, right?
I thing all the 3" drivers needed would end up being too expensive for me...
The other 5.25" driver I had in mind (the Zachry), at least had Qts, Fs and Vas listed. Do you think I should mistrust these figures as well?
Still, there seems to be some builders quite happy with non-perfect array designs, so I really don't know what to think.
Zarathu, what woofer spacing and crossover frequency do you use??
(Yes I live in Sweden)
/Magnus
3 inch mid/woofers, 3/4 inch dome tweeters.
Electronic crossed at 165 and 2500, Mid woofs have a 5 inch c-to-c, tweeters have a .85 - .95 inch c-to-c.
Very important that you use electronic crosses and 24 db/octave L-R crosses. This cannot be done passively and with anything less than 24db/octave L-R slope.
Zarathu
Electronic crossed at 165 and 2500, Mid woofs have a 5 inch c-to-c, tweeters have a .85 - .95 inch c-to-c.
Very important that you use electronic crosses and 24 db/octave L-R crosses. This cannot be done passively and with anything less than 24db/octave L-R slope.
Zarathu
Hi Magnus,
2580 Hz is the maximum usable frequency that if used would limit further directivity because the directivity drops steeply down just above c-c=lambda and how fast and deep depends on how many drivers is used, a very steep filter is needed. J. Griffin does recommend to crossover below lambda but not… how… low, J Griffin writes:
J.Griffin does not recommend to crossover at lambda, he merely points out the consequences with his example and the action to be taken if crossing over…below… lambda and how close depends on driver characteristic dispersion quality but the criteria’s he shows is Urban near and Ureda’s far field criteria that its recommended to stay within.
I wonder how Nearfield line array builders are interpreting this:
Of course the nulls will point at other directions than straight ahead, but nulls are nulls what is left out here is that strong side lobes appears pointing mirrored at the floor and ceiling, stronger than the main frontal lobe corrupting the vertical scene sense.
Look at the polar plots and globes for 2500,3150 and 4000 where it’s evident that all the second sound lobe emissions is stronger than the main frontal (they exists for most 3-5” drivers).
Most cheep drivers have also cone break-up at lambda making it even more undesirable to crossover at this region and leavening the whole crossover region corrupt.
The FR drop close to lambda creates a plateau difficult to cure if not an equalizer is used (see the on-axis FR plot).
Worse is the drop in directivity that means a huge increase of the side lobes that is characteristic for a newbie array or arrays that have a very coloured soundstage, array sound artefacts that arrives from the array design not from the inherent driver quality.
It’s my opinion that the dispersion artefacts should be eliminated, attenuated using good design practise.
Yes, If you are intending to use a 12 dB/octave filter i.e. acoustic 12 dB slope for the 5.25” drivers, use the lambda/2 criteria.
The wave-guide is very easy to build and recesses the tweeters to align acoustically with the M drivers.
You need 20/line = 20 x 0.081 = 1.62 m. I can spare you the 40 drivers needed from my extensive DIY driver stock if you want.
I offer you unused 3” Aura NS3 194 8E drivers for less than the Rila’s e.g. 20 Skr less than the retail prize of a Rila 5048 driver, you pay the freight costs from STHLM, not from the US. Mail me if you want to make a deal, this offer is open for a few days only, Im not a driver retailer.
No, this driver could do well as a W in an OB array but not as an M crossed over to a Dayton ND20FB line array.
I can’t help you here, its up to you to makeyour own decisions, my 2 cents of help is only to promote DIY’rs not to build arrays sounding array.
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Attachments
comb filter distortion: hearing it
A triple of important points:
1. All humans don't hear the same, and recollection of heard sound is very poor. Suggestibility of heard sound is very great. If I tell you to listen for something, then you will hear it, even if its not there. Audio hallucination is much more common than visual.
2. The most critical range of sound for differentiating instruments is in the 300-3000 range. If you have accurate presentation in this range you will be able to differentiate between all music and voice clarity. But the most critical human range for hearing differences between sounds is in the 2000 to 5000hz range.
Humans have difficulty differentiating differences in sounds between 5000 to 10000hz. And above 10000, humans can't tell what is what. Most humans can't hear much at all above 15000. If you can eliminate the start of comb filter distortion to above around 15000, only people under the age of 18 may be able to hear it.
3. Be careful you don't get caught up in tiny little audio points which you can see plainly on paper, but you simply cannot hear listening to real music in real life. I've been assured by EE types on the PE forum(a place I no longer go to post) that I have a seriously flawed line array. It matches the major criteria of Griffin. These people have never built a line array in their lives, and never even heard one. But by looking on paper they see major flaws; I CANNOT HEAR ANY OF THESE FLAWS.
Zarathu
A triple of important points:
1. All humans don't hear the same, and recollection of heard sound is very poor. Suggestibility of heard sound is very great. If I tell you to listen for something, then you will hear it, even if its not there. Audio hallucination is much more common than visual.
2. The most critical range of sound for differentiating instruments is in the 300-3000 range. If you have accurate presentation in this range you will be able to differentiate between all music and voice clarity. But the most critical human range for hearing differences between sounds is in the 2000 to 5000hz range.
Humans have difficulty differentiating differences in sounds between 5000 to 10000hz. And above 10000, humans can't tell what is what. Most humans can't hear much at all above 15000. If you can eliminate the start of comb filter distortion to above around 15000, only people under the age of 18 may be able to hear it.
3. Be careful you don't get caught up in tiny little audio points which you can see plainly on paper, but you simply cannot hear listening to real music in real life. I've been assured by EE types on the PE forum(a place I no longer go to post) that I have a seriously flawed line array. It matches the major criteria of Griffin. These people have never built a line array in their lives, and never even heard one. But by looking on paper they see major flaws; I CANNOT HEAR ANY OF THESE FLAWS.
Zarathu
"Where do you cross..."
I am not sure about how much this amount of 2"-3" helps in low end power - I imagine that with this huge amount of drivers they would be able to roll off on their own, without too much Xmax - the design will depend on this
If so, the woofers should play up to about 100hz with a plateamp
Tweeter - I imagine the single tweeter would be crossed in somewhere above 7khz to 10khz - maybe it even could be rear mounted, or both a front and rearmounted super tweeter if dipole would be considered
I am not sure about how much this amount of 2"-3" helps in low end power - I imagine that with this huge amount of drivers they would be able to roll off on their own, without too much Xmax - the design will depend on this
If so, the woofers should play up to about 100hz with a plateamp
Tweeter - I imagine the single tweeter would be crossed in somewhere above 7khz to 10khz - maybe it even could be rear mounted, or both a front and rearmounted super tweeter if dipole would be considered
tinitus said:
I'm not sure I understand your question.
I have a line array with a 3 inch mid woofer. But you need to use electronic crossovers at at least 24 db/octave L-R slope. And in my opinion you need to use one with an Xmax of at least 3.0 mm to get the maximum deep extension on them(down to 150 or so) so that you can use a set of sub woofers going down to about 20. If you go much higher than 150 or so, then you need a line of woofers in addition to your lines of mids and tweets, and YOU STILL NEED ANOTHER SUB WOOFER TO GET DOWN TO 20.
There are no specs listed on the Visaton so I've no idea if that is suitable or not.
Also I don't think you can cross at 7000. If you do that, the three inchers are too big. Even if you put them right next to each other you can't cross them any higher than about 4000hz, or you will get comb filter distortion that you CAN hear. If you use a 2 incher, then you won't be able to get down to 165hz, AND you'll still need a tweeter.
I'm not big on using single tweeters since it makes for an imbalance in the sensitivity of the array, and it fixes it so the mid ranges are in the near field and the tweeter is in the far field, which is another imbalance.
Am I answering your question?
Zarathu
Its not for nothing that many people use a larger midrange with a sub woofer, and ribbon tweeters.
There are more flexibility circumstances. Using ribbons means that you can go lower, possibly as low as 900hz. Going lower with your tweeters means that you don't have to try to go as high with your mid ranges.
Using 3 inchers doesn't give you as much flexibility. However, I chose them for other design reasons:
1. I didn't want a crossover(even an active one with a very steep slope) in the middle of the 300- 2500hz frequency range. A larger mid range would not go to 2500hz so I would be forced to cross there.
2. I wanted as much distortion reduction as possible in the system. The more speakers you use, the smaller load each must carry, and thus the lower the distortion. Using 6 inch mid woofers means that you end up using maybe only 12 of them in a 7 foot array, and less than that it a smaller one. Using ribbons in the tweeters often means only using 6 of them. Compare this to using 17 mid ranges, and 30 tweeters for a substantially greater reduction in distortion.
3. For the reason of number 2 I also didn't taper them( in addition the the fact that I wanted a huge sound stage not a simulated micro stage.)
4. It is my belief that coloration in the mid range is largely caused by artefactual sound coming back through speaker from the back side. I wanted some of the unusual benefits of a closed tube for my mid range speakers, and I wanted the speakers completely separated from the other midrange speakers. By using tubes:
a. the whole system is much much lighter in weight
b. the tubes actually are separated by 1/2 inch of free air from each other.
c. I can pack the interior of the tube to 4 lb cu ft of fiberglass attenuating the back wave to better than 95%
d. There is almost no storage of sound energy in the structure
e. odd ordered harmonics are eliminated from the limited amount of sound that does return from the cabinet and goes through the speaker cone
5. While ribbons have a reputation for sizzling transient response this is only because they have such a light membrane that doesn't have the inertia of a dome, which is much heavier. But some domes like the Dayton NeoND20A have extremely thin shells, and when asked to move just a tiny bit, they are pretty fast too. If you look at the spectral decay which should show the ribbon responding much faster, only the B&G Beo3 on Zaph's test handily beats the Dayton. And the Dayton's FR is comparative. And when you compare 30 of them to maybe 5 of the Dayton Planars, I can't see the Planars or maybe even the B&G's coming out first.
Zarathu
There are more flexibility circumstances. Using ribbons means that you can go lower, possibly as low as 900hz. Going lower with your tweeters means that you don't have to try to go as high with your mid ranges.
Using 3 inchers doesn't give you as much flexibility. However, I chose them for other design reasons:
1. I didn't want a crossover(even an active one with a very steep slope) in the middle of the 300- 2500hz frequency range. A larger mid range would not go to 2500hz so I would be forced to cross there.
2. I wanted as much distortion reduction as possible in the system. The more speakers you use, the smaller load each must carry, and thus the lower the distortion. Using 6 inch mid woofers means that you end up using maybe only 12 of them in a 7 foot array, and less than that it a smaller one. Using ribbons in the tweeters often means only using 6 of them. Compare this to using 17 mid ranges, and 30 tweeters for a substantially greater reduction in distortion.
3. For the reason of number 2 I also didn't taper them( in addition the the fact that I wanted a huge sound stage not a simulated micro stage.)
4. It is my belief that coloration in the mid range is largely caused by artefactual sound coming back through speaker from the back side. I wanted some of the unusual benefits of a closed tube for my mid range speakers, and I wanted the speakers completely separated from the other midrange speakers. By using tubes:
a. the whole system is much much lighter in weight
b. the tubes actually are separated by 1/2 inch of free air from each other.
c. I can pack the interior of the tube to 4 lb cu ft of fiberglass attenuating the back wave to better than 95%
d. There is almost no storage of sound energy in the structure
e. odd ordered harmonics are eliminated from the limited amount of sound that does return from the cabinet and goes through the speaker cone
5. While ribbons have a reputation for sizzling transient response this is only because they have such a light membrane that doesn't have the inertia of a dome, which is much heavier. But some domes like the Dayton NeoND20A have extremely thin shells, and when asked to move just a tiny bit, they are pretty fast too. If you look at the spectral decay which should show the ribbon responding much faster, only the B&G Beo3 on Zaph's test handily beats the Dayton. And the Dayton's FR is comparative. And when you compare 30 of them to maybe 5 of the Dayton Planars, I can't see the Planars or maybe even the B&G's coming out first.
Zarathu
Drivers selected
The decision is made. The mid/woofers will , thanks to Bjorno, be 20 3" Aurasound NS3 194 8E per array!
These are wideband drivers (125-20000 Hz), which opens up for a couple of ideas or "steps" in the design:
1. I will try running the array without tweeters or crossovers.
This will of course lead to "combing" since the "tweeters sources" will be at least 81mm apart. It will be interesting to see if I will notice the theoretical flaws in this design! Either way ,sooner or later, I assume I will try moving on to anther step.
2. Crossover at 2500 or something, to a single tweeter in each array.
This will be some kind of hybrid between array and point source. The biggest problem will be that the tweeter level in the room will vary with the distance from the speakers. It might not be a problem in a stationary sofa though...?
3. Arrays of cheap "Apex JR" tweeters. As far as I can see, these drivers can only be used from about 4500 Hz (with a steep crossover), which once again makes the woofer spacing a problem. How big? It might be worth a try... perhaps with a wave guide?
4. Arrays of Dayton ND20Fb tweeters. This should be very good, but the cost is bigger as well. How much better than stage 3??
5. Long DIY ribbon tweeters. Should have a great frequency range, perfect line sources... The problem here is that they have to be home-made, and still aren't very cheap. It would probably be a very interesting DIY project. I really would like to try!
Any comments? Any other interesting combinations that might be worth trying?
The decision is made. The mid/woofers will , thanks to Bjorno, be 20 3" Aurasound NS3 194 8E per array!
These are wideband drivers (125-20000 Hz), which opens up for a couple of ideas or "steps" in the design:
1. I will try running the array without tweeters or crossovers.
This will of course lead to "combing" since the "tweeters sources" will be at least 81mm apart. It will be interesting to see if I will notice the theoretical flaws in this design! Either way ,sooner or later, I assume I will try moving on to anther step.
2. Crossover at 2500 or something, to a single tweeter in each array.
This will be some kind of hybrid between array and point source. The biggest problem will be that the tweeter level in the room will vary with the distance from the speakers. It might not be a problem in a stationary sofa though...?
3. Arrays of cheap "Apex JR" tweeters. As far as I can see, these drivers can only be used from about 4500 Hz (with a steep crossover), which once again makes the woofer spacing a problem. How big? It might be worth a try... perhaps with a wave guide?
4. Arrays of Dayton ND20Fb tweeters. This should be very good, but the cost is bigger as well. How much better than stage 3??
5. Long DIY ribbon tweeters. Should have a great frequency range, perfect line sources... The problem here is that they have to be home-made, and still aren't very cheap. It would probably be a very interesting DIY project. I really would like to try!
Any comments? Any other interesting combinations that might be worth trying?
Frame of reference from another forum
The following were some points made by someone who listened to a set of Dali Mega's in a show:
".........some things did stick out as different.
"1. The sound was a little out of proportion,
"2. image size within the soundstage were larger than they should be
"3. image positioning was vaguer than I was used to on familiar tracks.[compared to my own speakers]
"4. it was a little in your face. Again this was with tracks I was familiar listening to on my own speakers.
"5. The problem I had with the demo was that the room was often busy with folks walking in front of speakers, talking or the door opening and letting in noise from the corridor etc."
-----------
My response:
I think the sticking point here is your perception in comparing the line array to your present speaker system. As long as anyone compares a point source system to a line array, and believes that the point source is the standard to be maintained the line array will come up different and this difference will be perceived as "wrong".
I try hard not to compare them to a point source system. What I try to do is compare them to an actual performance of the musicians as if they were in my music room. In the case of full orchestra, I've found that the sound stage from where I sit with my season's tickets on the first balcony is about 12 feet, and soloists are far away. If I want to listen to soloists and feel them as they are then I sit in the 10 row down stairs, and the sound stage now is not 8 x 12 but more like 22 by huge.
Both of these are completely different from an experience with a point source.
If I want to listen to Sweetwater(a blues group from Louisiana, USA), I be sitting on the floor and they will be up on a little 3 foot stage, and I will be sitting about 2 tables away), and they will be IN MY FACE.
When I listen to single insturments, I remember that they are sitting on a stage, not right next to me.
When I listened to my point source speakers, because they are so small, and because the dynamic range is so limited, only parts of the sound image came forward. When i expanded the same music piece to a full array size, the image increased in its component parts and some of the things that I knew where they were in the little speakers changed and became more like a real performance.
------------------
You didn't take the array home to your home. After listening to my line array for 6 months, I now compare my array to live performances not to other speakers. Often the recording is a piece of crap. Sometimes listening to a CD in my car sounds great but its just too thin in my real system. Phantom of the Opera was a perfect case. The DVD might have been different, but currently my DVD player is not hooked up to the line array.
I would put forward that you are comparing your point source system to the line array hoping that the line array will be just like your point source system only better. I would put forward that the line array is a COMPLETELY DIFFERENT LISTENING EXPERIENCE.
Zarathu
The following were some points made by someone who listened to a set of Dali Mega's in a show:
".........some things did stick out as different.
"1. The sound was a little out of proportion,
"2. image size within the soundstage were larger than they should be
"3. image positioning was vaguer than I was used to on familiar tracks.[compared to my own speakers]
"4. it was a little in your face. Again this was with tracks I was familiar listening to on my own speakers.
"5. The problem I had with the demo was that the room was often busy with folks walking in front of speakers, talking or the door opening and letting in noise from the corridor etc."
-----------
My response:
I think the sticking point here is your perception in comparing the line array to your present speaker system. As long as anyone compares a point source system to a line array, and believes that the point source is the standard to be maintained the line array will come up different and this difference will be perceived as "wrong".
I try hard not to compare them to a point source system. What I try to do is compare them to an actual performance of the musicians as if they were in my music room. In the case of full orchestra, I've found that the sound stage from where I sit with my season's tickets on the first balcony is about 12 feet, and soloists are far away. If I want to listen to soloists and feel them as they are then I sit in the 10 row down stairs, and the sound stage now is not 8 x 12 but more like 22 by huge.
Both of these are completely different from an experience with a point source.
If I want to listen to Sweetwater(a blues group from Louisiana, USA), I be sitting on the floor and they will be up on a little 3 foot stage, and I will be sitting about 2 tables away), and they will be IN MY FACE.
When I listen to single insturments, I remember that they are sitting on a stage, not right next to me.
When I listened to my point source speakers, because they are so small, and because the dynamic range is so limited, only parts of the sound image came forward. When i expanded the same music piece to a full array size, the image increased in its component parts and some of the things that I knew where they were in the little speakers changed and became more like a real performance.
------------------
You didn't take the array home to your home. After listening to my line array for 6 months, I now compare my array to live performances not to other speakers. Often the recording is a piece of crap. Sometimes listening to a CD in my car sounds great but its just too thin in my real system. Phantom of the Opera was a perfect case. The DVD might have been different, but currently my DVD player is not hooked up to the line array.
I would put forward that you are comparing your point source system to the line array hoping that the line array will be just like your point source system only better. I would put forward that the line array is a COMPLETELY DIFFERENT LISTENING EXPERIENCE.
Zarathu
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