Diffraction Loss due to Baffle step rolloff:
http://www.trueaudio.com/st_diff1.htm
And as an excerpt from an answer to such a question by Dr. John Murphy:
"The 6 dB loss is correct for a speaker enclosure in free space. When the enclosure is placed in a room it will encounter various effects due to the room (reverb, standing waves, boundary effect, cavity effect . . .)
"Diffraction loss and room effects are independent and completely different effects. The diffraction loss is nicely predictable whereas the effects of the room are highly variable, not only from room to room but also with speaker placement and room furnishing. This typically means that each listening environment will be unique and will require unique compensation."
Additonally the loss is way more unpredictable when using anything other than a spherical enclosure, and placement of the speakers on the baffle itself changes the bizarre curve of the loss from something smooth in a sphere the something that looks vaguely like a transient response graph.
See Murphy's article for more.
Zarathu
http://www.trueaudio.com/st_diff1.htm
And as an excerpt from an answer to such a question by Dr. John Murphy:
"The 6 dB loss is correct for a speaker enclosure in free space. When the enclosure is placed in a room it will encounter various effects due to the room (reverb, standing waves, boundary effect, cavity effect . . .)
"Diffraction loss and room effects are independent and completely different effects. The diffraction loss is nicely predictable whereas the effects of the room are highly variable, not only from room to room but also with speaker placement and room furnishing. This typically means that each listening environment will be unique and will require unique compensation."
Additonally the loss is way more unpredictable when using anything other than a spherical enclosure, and placement of the speakers on the baffle itself changes the bizarre curve of the loss from something smooth in a sphere the something that looks vaguely like a transient response graph.
See Murphy's article for more.
Zarathu
We've had a pretty good discussion about this on the PE discussion board, specifically at:
http://www.pesupport.com/cgi-bin/config.pl?read=314243
http://www.pesupport.com/cgi-bin/config.pl?read=314296
and
http://www.pesupport.com/cgi-bin/config.pl?read=314309
I usually post as Marlboro over there.
You will find that the edge diffraction of Baffle step seems to lessen to only one db as the number of speakers on the baffle increases above 12 or so. And of course we're really only talking about a difficult with Midrange speakers.
Thanks for the great discussion.
Zarathu
http://www.pesupport.com/cgi-bin/config.pl?read=314243
http://www.pesupport.com/cgi-bin/config.pl?read=314296
and
http://www.pesupport.com/cgi-bin/config.pl?read=314309
I usually post as Marlboro over there.
You will find that the edge diffraction of Baffle step seems to lessen to only one db as the number of speakers on the baffle increases above 12 or so. And of course we're really only talking about a difficult with Midrange speakers.
Thanks for the great discussion.
Zarathu
I have built a few prototype lines and have found the Foster 'wide range' (00504) drivers perform much better in the line then the more linear woofer (00463) version. The wide range driver response rises to 6-7 db up at 5k when used as a single driver. It also has about half the mass of the woofer version and performs just as well in the lower range in the line array. When the 00504 is used in a closely spaced line of 12 or more (never tried a less than 12) the in-room 2-4 meter response is very linear out to 4k (about 2 db down from 1k) and with a 12" wide baffle they go down to 150 Hz (-3 db) . The woofer (00463) driver dies at 1,2K or so as Scott predicted.
The 00504's sound very good indeed - far better then I expected from the $3.00 driver. They are also fairly sensitive with 12 of them and can play quite loud (when high passed above 120 Hz) with low perceived compression. They drive the room much like the line array I heard that inspired me to cut all these holes.
I like dipole radiation so have decided to extend the systems response below 150 with 12 (six per side) 10" Madison Warrior bass drivers. I already had six of them from a previous project so I put them on a 18" wide open baffle line and placed them close to the side wall to the outside of the 'wide range' line. These show some serious promise for duty below 150 cycles. Work in progress. I'm trying to decide if I will use seperate baffles for the bass.
The little Dayton tweeters are still in the box. I have 64 of them now so my lines will consist of 64 treble drivers, 32 'wide range' drivers and 12 ten inch bass drivers with my horn sub sytsem for the bottom end.
Being a long weekend for me I hope to have a working system near completion in a few days. 🙂
The 00504's sound very good indeed - far better then I expected from the $3.00 driver. They are also fairly sensitive with 12 of them and can play quite loud (when high passed above 120 Hz) with low perceived compression. They drive the room much like the line array I heard that inspired me to cut all these holes.
I like dipole radiation so have decided to extend the systems response below 150 with 12 (six per side) 10" Madison Warrior bass drivers. I already had six of them from a previous project so I put them on a 18" wide open baffle line and placed them close to the side wall to the outside of the 'wide range' line. These show some serious promise for duty below 150 cycles. Work in progress. I'm trying to decide if I will use seperate baffles for the bass.
The little Dayton tweeters are still in the box. I have 64 of them now so my lines will consist of 64 treble drivers, 32 'wide range' drivers and 12 ten inch bass drivers with my horn sub sytsem for the bottom end.
Being a long weekend for me I hope to have a working system near completion in a few days. 🙂
woofer arrays
Magnetar,
I hope you have some pictures.
The woofers sound awesome. I can't afford the space or the cash for a woofer array. since I already have a set of terrific 12 inch Goldsound 15 Xmax woofers, I decided to put them in a 16 x 16 box and then extend a 15 inch sonotube 86 inches to the ceiling. This gives me nearly 92 db of performance down to about 18hz. I've deliberately tuned it to a drop in the frequency starting at about thirty so that the standard room compensation doesn't overwhelm. They are obviously ported and will have 6 2 inch x 13 inch vents around the top, with a mach of about .09. At the moment I'm not planning on stuffing them except for some center stuffing about halfway.
Zarathu
😎
Magnetar,
I hope you have some pictures.
The woofers sound awesome. I can't afford the space or the cash for a woofer array. since I already have a set of terrific 12 inch Goldsound 15 Xmax woofers, I decided to put them in a 16 x 16 box and then extend a 15 inch sonotube 86 inches to the ceiling. This gives me nearly 92 db of performance down to about 18hz. I've deliberately tuned it to a drop in the frequency starting at about thirty so that the standard room compensation doesn't overwhelm. They are obviously ported and will have 6 2 inch x 13 inch vents around the top, with a mach of about .09. At the moment I'm not planning on stuffing them except for some center stuffing about halfway.
Zarathu
😎Magnetar,
Can you report on your progress with your new array speakers? Am curious as to what you ended up with and how the finished product sounds. Would love to see pictures of your work.
Hello,
I'll post a pic this weekend.
They are nearing completion and sound wonderful.
I ended up using 30 tweeters, 12 midrange and 6 ten inch pro bass drivers per channel in a triamped open baffle. The bass is measuring in at a whopping 108 DB/W/M and is very tight and tuneful...😀
What is amazing is it's the first time my horn loaded sub bass actually has seen it's match in the midbass.
This was a very successful and rewarding project for me.
I'll post a pic this weekend.
They are nearing completion and sound wonderful.
I ended up using 30 tweeters, 12 midrange and 6 ten inch pro bass drivers per channel in a triamped open baffle. The bass is measuring in at a whopping 108 DB/W/M and is very tight and tuneful...😀
What is amazing is it's the first time my horn loaded sub bass actually has seen it's match in the midbass.
This was a very successful and rewarding project for me.
Looks very nice. I wish I could hear them prior to my next speaker project. Can you take a pix of the backside?
Thanks
Thanks
Magnetar said:
i guess when you are not afraid of big speakers with big baffles and lots of cone area the efficiency comes naturally...
if you are up towards the cleveland area, the downtown audiocraft store usually has some top of the line macintosch line array speakers on hand (kind of wierd since they are almost 100% a lo & mid fi, tiny speaker store now). the line arrays where the only "hifi" speakers that i heard that could compare with the dynamic range & output of some of your earlier horn based projects. it might be fun to compare & contrast.
don't tear them down before i get to hear them! talk you later.
Hi,
I remember that there is a PDF file about line sources and it had a chart that showed the length a line source has to be vs. distance it is used from. Can anyone link me to that file, I can't find it!
Thanks!
I remember that there is a PDF file about line sources and it had a chart that showed the length a line source has to be vs. distance it is used from. Can anyone link me to that file, I can't find it!
Thanks!
Tenson,
In my Near Field Line Array white paper I have a graph that relates the line height, frequency, and near to far field transition distance. Take a look at Figure 5 in this paper:
http://www.audiodiycentral.com/resource/pdf/nflawp.pdf
Jim
In my Near Field Line Array white paper I have a graph that relates the line height, frequency, and near to far field transition distance. Take a look at Figure 5 in this paper:
http://www.audiodiycentral.com/resource/pdf/nflawp.pdf
Jim
might be interested, tried to send you an email but haven't posted enough yet 🙂
been looking at line arrays for my next project for a while, maybe you can send me an email and i can respond?
thanks!
been looking at line arrays for my next project for a while, maybe you can send me an email and i can respond?
thanks!
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