The array in question was only used in the XRT24 and 25. I don't think in anything after, although the have used the Bessel arrays as described in the paper (after Keele and others).
There have been a lot of audiophile line array systems that could be significantly improved by proper tapering. Yet I am not aware of any high-end designer that has understood or used the technique. This includes electrostatic and planer magnetic designs. I've tried to explain the approach and benefit to numerous designers and always get the blank stare.
David
Thanks David...
My stare is not blank... more like that confused look a cat or dog can give you??
No, seriously I "get it"... but as i said, McIntosh seems (ed) to keep this "feature" unstated. At least I never noticed it in anything i ever read, not that I read everything... but I have never heard it mentioned...
Speaking of Bessel arrays - my impression is/was that they are frequency tapered from a "center" point (up and down) not amplitude tapered?
_-_-bear
My stare is not blank... more like that confused look a cat or dog can give you??
No, seriously I "get it"... but as i said, McIntosh seems (ed) to keep this "feature" unstated. At least I never noticed it in anything i ever read, not that I read everything... but I have never heard it mentioned...
Speaking of Bessel arrays - my impression is/was that they are frequency tapered from a "center" point (up and down) not amplitude tapered?
_-_-bear
speaking of the inverse (??), I was at Wallmort the other day and I walked past a spot in the aisle in the cosmetic section and suddenly heard sound. I stared up at the high black metal truss work overhead and saw what looked like an array of small (computer sound sized) speakers, in a line, behind black perf metal grille. Very very very directional from about 20 feet above. Oh, parallel to the aisle...
Reverse tapering?? Or??
_-_-bear
Reverse tapering?? Or??
_-_-bear
Fun with Arrays
This is another interesting applications of arrays: using super directivity to focus a beam to a narrow audience. I think some museums are using this where you can walk from painting to painting and a large area array gives you comentary that is only audible in front of the painting. (Either that or WalMart just had a few plasma TV speakers left over!)
Somewhat related are the panel arrays that One Digital (Pioneer) and Yamaha are selling. A single rows-and-columns array can create multiple sharp beams that might reflect off your walls to create 5 surround sources. All they have to do is create tight, wide frequency band pencils of sound, that fire in the appropriate directions of the room.
Multi antenna deep space arrays are also the same technology.
David
This is another interesting applications of arrays: using super directivity to focus a beam to a narrow audience. I think some museums are using this where you can walk from painting to painting and a large area array gives you comentary that is only audible in front of the painting. (Either that or WalMart just had a few plasma TV speakers left over!)
Somewhat related are the panel arrays that One Digital (Pioneer) and Yamaha are selling. A single rows-and-columns array can create multiple sharp beams that might reflect off your walls to create 5 surround sources. All they have to do is create tight, wide frequency band pencils of sound, that fire in the appropriate directions of the room.
Multi antenna deep space arrays are also the same technology.
David
Thanks David...
My stare is not blank... more like that confused look a cat or dog can give you??
Speaking of Bessel arrays - my impression is/was that they are frequency tapered from a "center" point (up and down) not amplitude tapered?
_-_-bear
The Bessel array is a weighted coefficients or shaded array. The common example is 5 elements with coefficients of:
+0.5 -1 +1 +1 +0.5
In other words the outter elements are 6dB down and one element is out of phase. It turns out that such an array has no extra directivity in spite of being 5 elements long. Mac has some speakers with 5 tweeters mounted sideways using the Bessel weighting. Because of one tweeter out of phase and two at half strength, you get minimal extra output from your 5 tweeters, so it seems like a marginal benefit to me.
I think what you are thinking of would be like the 3 element arrays that have been designed for THX approval or elsewhere when a little more directivity was desired. (Another Mac product like the HT1) In that case the outer tweeters of the trio would be rolled off in the right amount and you can achieve good response and no lobes.
David
re #103
To add to David's reply. The Bessel array was initially designed, as a spherical radiation solution. At the time Philips (the Patent holders) were involved in sound reinforcement. The Bessel array was a cost effective solution to reduce interference effects, caused by positioning multiple adjacent drivers, or systems, side by side. At the time a step up from the usual cheap and nasty column speakers.
Iain.
bessel arrays.
McIntosh XRT18 Speaker System history
Bear,
To add to David's reply. The Bessel array was initially designed, as a spherical radiation solution. At the time Philips (the Patent holders) were involved in sound reinforcement. The Bessel array was a cost effective solution to reduce interference effects, caused by positioning multiple adjacent drivers, or systems, side by side. At the time a step up from the usual cheap and nasty column speakers.
Iain.
bessel arrays.
McIntosh XRT18 Speaker System history
Thanks for that input...
Odd, my brain must be misfiring, not an uncommon occurance (!!) but I seem to recall reading about Bessel Arrays in Berenek's Acoustics textbook... obviously I got it wrong. (grrrr...)
Ok so what then is a frequency tapered line array??
All of my reading on this - not a lot at that - predates anything like THX, and is (omg!!) LAST CENTURY!!
_-_-bear
Odd, my brain must be misfiring, not an uncommon occurance (!!) but I seem to recall reading about Bessel Arrays in Berenek's Acoustics textbook... obviously I got it wrong. (grrrr...)
Ok so what then is a frequency tapered line array??
All of my reading on this - not a lot at that - predates anything like THX, and is (omg!!) LAST CENTURY!!
_-_-bear
Don't know if the group delay steering used in the JBL CBTs works worth a whit yet, but I think it's darn clever and easy to implement DIY.
Is that a Keele or a Button innovation?
[They're obviously WAY smarter than the Zilchster, who is more like 10,000 monkeys by comparison.... ]
Is that a Keele or a Button innovation?
[They're obviously WAY smarter than the Zilchster, who is more like 10,000 monkeys by comparison....
]
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Yes, University and others were rolling off the highs of outer units in column speakers in the 50s and 60s. What you would like an array to do is appear to have constant length in proportion to (inverse) frequency. That is be twice as long for every octave down you go. Then its beamwidth and polar pattern would be constant. If you use a row of identical drivers but progressively roll off the high frequencies to the outer ones then you can approach that. That would be frequency tapering. I used it for THX arrays at Mac and the XA (eXpanding Array) series at Snell.
http://www.diyaudio.com/forums/multi-way/159706-dappolito-arrays-waveguides.html
If you just vary the strength (not frequency response) of elements, typically turning down the outer elements, then that has been called shading. That can give a much better behaved polar pattern, but it will still vary with frequency.
Thanks for the Bessel reference, Applehorn.
David
With the talk of power tapering, bessel arrays, etc., being too difficult for me to understand I simply went the other way with a focused array. Actually, I built the array itself about 13 or 14 years ago and finally built a bass module earlier this spring. Very flat in-room frequency response from 33 Hz to about 17+ kHz or so.
Best Regards,
TerryO
Best Regards,
TerryO
The small (approx. 1.5 inch) shielded fullrange drivers were a Radio Shack close out and the woofer is an Adire AV8 woofer (also shielded). They use a series crossover @ 450 Hz.
BTW: I have around $81.00 invested altogether.
It took 1st place in the 2-way class at "The Puget Sound! DIY Speaker Contest" which has a thread in the "Multiway" forum, as well as several mentions in the latest Vancouver Island DIY Fest in the "events" forum of diyAudio.
Best Regards,
TerryO
TerryO, touche' sorry I missed it.
Bear, bump!
I really do want to put forth something that does not seem to be concluded here. While all the GedLee's, Sigfried and Earl's, Don and his team, David Smith and lets not forget the author of the most sited line array paper recently Jim, (sorry, if I don't recognize, or left any of this decades Line Array guru's out) might still be subscribed, can anyone comment on Roger Russell's IDS-25? Or the relatively simplistic theory behind it, he says works? Totally paralelled drivers I believe? Floor to ceiling? No tweeters? No delay, physical or electrical or splayed mounting? Likely lots (to much) EQ. etc. etc.
Maybe this is a little OT but? Not to me...
Advantages of the IDS Technology
My Experience with Column Systems (2/3rds down)
Did anyone of you here it? Do you have comments? Thx
Bear, bump!
I really do want to put forth something that does not seem to be concluded here. While all the GedLee's, Sigfried and Earl's, Don and his team, David Smith and lets not forget the author of the most sited line array paper recently Jim, (sorry, if I don't recognize, or left any of this decades Line Array guru's out) might still be subscribed, can anyone comment on Roger Russell's IDS-25? Or the relatively simplistic theory behind it, he says works? Totally paralelled drivers I believe? Floor to ceiling? No tweeters? No delay, physical or electrical or splayed mounting? Likely lots (to much) EQ. etc. etc.
Maybe this is a little OT but? Not to me...
Advantages of the IDS Technology
My Experience with Column Systems (2/3rds down)
Did anyone of you here it? Do you have comments? Thx
Hello David,
i use a combination of weighting by distance and
power tapering (frequency dependent) in this
project. The lower three drivers are rolled off
towards higher frequencies.
Attachments
I can't comment directly on Roger's product's performance, but floor to ceiling arrays will have an easier time of achieving good performance than shorter arrays will. If your array is floor to ceiling and your floor and ceiling are hard surfaces, then the surface reflections make the array seem infinite (imagine a line between two mirrors and you will see an infinite line, counting the reflections). You can move up and down in front of the unit and see none of the finite length, variable beamwidth issues that all of the modified designs are trying to improve.
There will still be the issues of unit packing (having enough points close enough together to get around the fine HF pattern of uneveness, and you have to deal with making a unit work well over the full range, but for those that like to play with full range drivers and a little EQ, there is a lot to work with here.
I also did some simulations of floor-almost-to-ceiling arrays and the performance was about the same for all practical purposes. That is if your line array was a foot or so shy of the ceiling the repeated reflection sections would have a gap between one and the next. It didn't degrade the response too badly.
David S.