I have to state up front that I am not a fan of loudspeaker arrays. IMHO, they are a compromised solution. Having said that, there are a lot of situations where a compromise is in order.
One example that comes to mind is when you want to use a driver with a wide bandwidth and low power handling. For instance, TangBand, Peerless and Aurasound make some great small drivers which can literally cover seven octaves with authority. I've used the Aurasound Whisper with great success. IMHO, this cheap tiny driver sounds as good or better as many two-way speakers that cost ten times as much! Even better, you could do a project with one of these drivers in a single evening.
That sure beats MY projects, which seem to span weeks or months
Of course the Achilles Heel with these tiny drivers is that they're power handling is atrocious.
One array that might be the solution is the little used Bessel array. The Bessel array is exceptionally simple. In a nutshell, the Bessel array takes a single driver, then adds four more. Two are on one side, and two on the other. The trick is that half of them are out-of-phase. The end result is a "virtual driver" with higher power handling than a single driver, and a bit more efficiency.
IMHO, probably the greatest feature of the Bessel Array is that it doesn't have to be vertical. So for instance, you could put a horizontal Bessel array under your TV as a center channel, or on the dash of your car where a vertical line array wouldn't work.
For anyone who's interested in reading more, check these out.
Simple explanation:
http://www.angelfire.com/sd/paulkemble/soundf.html
Another good one:
http://www.prosoundweb.com/install/synaudcon/tt25_4/tt25_4_p1.shtml
Google patents has so many papers on the bessel array it's not even funny:
http://www.google.com/patents?q=bessel+array&btnG=Search+Patents
McIntosh is obsessed with the Bessel array:
One example that comes to mind is when you want to use a driver with a wide bandwidth and low power handling. For instance, TangBand, Peerless and Aurasound make some great small drivers which can literally cover seven octaves with authority. I've used the Aurasound Whisper with great success. IMHO, this cheap tiny driver sounds as good or better as many two-way speakers that cost ten times as much! Even better, you could do a project with one of these drivers in a single evening.
That sure beats MY projects, which seem to span weeks or months
Of course the Achilles Heel with these tiny drivers is that they're power handling is atrocious.
One array that might be the solution is the little used Bessel array. The Bessel array is exceptionally simple. In a nutshell, the Bessel array takes a single driver, then adds four more. Two are on one side, and two on the other. The trick is that half of them are out-of-phase. The end result is a "virtual driver" with higher power handling than a single driver, and a bit more efficiency.
IMHO, probably the greatest feature of the Bessel Array is that it doesn't have to be vertical. So for instance, you could put a horizontal Bessel array under your TV as a center channel, or on the dash of your car where a vertical line array wouldn't work.
For anyone who's interested in reading more, check these out.
Simple explanation:
http://www.angelfire.com/sd/paulkemble/soundf.html
Another good one:
http://www.prosoundweb.com/install/synaudcon/tt25_4/tt25_4_p1.shtml
Google patents has so many papers on the bessel array it's not even funny:
http://www.google.com/patents?q=bessel+array&btnG=Search+Patents
McIntosh is obsessed with the Bessel array:
An externally hosted image should be here but it was not working when we last tested it.
Thanks for bringing this up Patrick.
Bessel arrays have always intrigued me. I saw your example from McIntosh and I immediately thought, "What a great way to control directivity while maintaining a close C-C spacing with the mid or lo freq driver." Of course, that particular array only controls in the horizontal axis, but its a start. AND you get the benefits of (per the prosoundweb.com link) an extra 4.5dB SPL and the associated power handling.
For practical implementation's sake, it would be great to see a white paper similar to Griffin's whitepaper on line arrays. Of particular interest would be how the C-C spacing would affect the directivity and what the limit is before the array 'falls apart'.
I have half a mind to buy up a bunch of the Dayton backmounted neos and start tinkering....
Anybody have hands on experience and/or listening impressions from a Bessel Array?
Cheers,
Sam
Bessel arrays have always intrigued me. I saw your example from McIntosh and I immediately thought, "What a great way to control directivity while maintaining a close C-C spacing with the mid or lo freq driver." Of course, that particular array only controls in the horizontal axis, but its a start. AND you get the benefits of (per the prosoundweb.com link) an extra 4.5dB SPL and the associated power handling.
For practical implementation's sake, it would be great to see a white paper similar to Griffin's whitepaper on line arrays. Of particular interest would be how the C-C spacing would affect the directivity and what the limit is before the array 'falls apart'.
I have half a mind to buy up a bunch of the Dayton backmounted neos and start tinkering....
Anybody have hands on experience and/or listening impressions from a Bessel Array?
Cheers,
Sam
I heard a quite amazing demonstration of a 5x5 array
using coax drivers of approx 10cm diameter at a university
near my hometown in spring this year.
Several modes of power distribution were demonstrated
auditively and by measurement.
It was astonishing to me, that control of directivity was
even possible in frequency ranges where wavelength is
like driver spacing or smaller.
Even though the polar diagram looks somewhat tattered
towards higher frequencies, it still works to a great extent
auditively.
We were able to walk around in the demonstration room and
switch e.g. between bessel distribution and even distribution.
One interesting mode to drive the array was to use the lower
4x5 drivers as bass cones with equal distribution and in phase,
while driving the upper horizontal row in the mid-high range
with bessel distribution. The result was a reasonable PA Box
with wide dispersion in the mid high range.
You can do a lot with those arrays and by the way you drive
the single sound sources you can adapt it to many requirements
given in a certain room / auditory.
I was invited to that demonstration by a colleague who knew
my interest in "weighted" or "shaded" line arrays. From
own experience i know, that a somewhat scattered polar
plot in one plane can be tolerated very good as long as
the "overall shape" fits the need and does not vary too much
with frequency.
It is most preferable to the very frequency dependent
overall distribution of usual fullrange or 2-Way concepts IMO.
Regards
using coax drivers of approx 10cm diameter at a university
near my hometown in spring this year.
Several modes of power distribution were demonstrated
auditively and by measurement.
It was astonishing to me, that control of directivity was
even possible in frequency ranges where wavelength is
like driver spacing or smaller.
Even though the polar diagram looks somewhat tattered
towards higher frequencies, it still works to a great extent
auditively.
We were able to walk around in the demonstration room and
switch e.g. between bessel distribution and even distribution.
One interesting mode to drive the array was to use the lower
4x5 drivers as bass cones with equal distribution and in phase,
while driving the upper horizontal row in the mid-high range
with bessel distribution. The result was a reasonable PA Box
with wide dispersion in the mid high range.
You can do a lot with those arrays and by the way you drive
the single sound sources you can adapt it to many requirements
given in a certain room / auditory.
I was invited to that demonstration by a colleague who knew
my interest in "weighted" or "shaded" line arrays. From
own experience i know, that a somewhat scattered polar
plot in one plane can be tolerated very good as long as
the "overall shape" fits the need and does not vary too much
with frequency.
It is most preferable to the very frequency dependent
overall distribution of usual fullrange or 2-Way concepts IMO.
Regards
more info on them here: http://www.angelfire.com/sd/paulkemble/soundf.html
oops, you've already posted that link
The question is how far away do you have to be for the array to gel & does this make them impractical for home use?
(if it's frequency dependent then tweeter arrays may be OK?)
oops, you've already posted that link
The question is how far away do you have to be for the array to gel & does this make them impractical for home use?
(if it's frequency dependent then tweeter arrays may be OK?)
I think it's something like 5-10x the size of the array. So for instance, a 5 element bessel array of two inch drivers should be listened to from 50" to 100" as a minimum.
Don't quote me on that - I'm reciting that off the top of my head.
Check ou the AES papers, and there's a Phillips paper out there too.
Don't quote me on that - I'm reciting that off the top of my head.
Check ou the AES papers, and there's a Phillips paper out there too.
US pat. application 20060159288 (feed that number into www.pat2pdf.org) covers this topic in big detail, showing response plots and many practical variations (beware, 101 pages, 4MegByte).
This is really interesting stuff, never heard of it before.... now a dipole panel with 7x7 2" Auras (36 total, actually) plus a center AMT tweeter would look quite radical, for sure.
Something I'm not clear about is whether the polar patterns of the square arrays is considerably uniform in all directions, not only vertical/horizontal.
... time to lauch Akabak and try some sims on this...
- Klaus
This is really interesting stuff, never heard of it before.... now a dipole panel with 7x7 2" Auras (36 total, actually) plus a center AMT tweeter would look quite radical, for sure.
Something I'm not clear about is whether the polar patterns of the square arrays is considerably uniform in all directions, not only vertical/horizontal.
... time to lauch Akabak and try some sims on this...
- Klaus
Patrick Bateman said:
Ditto.
FWIW, here's a response to a basslist thread long ago on a BA's power handling:
>my BassBox Pro database for the FE-167 says that the
average power handling is 33 watts for a single
driver. The max SPL/Hz @ 1 m of the single driver is
107 dB.
>A 5 driver Bessel arrangement yields power handling
of 115.5 watts and a max SPL of 113 dB at an
impedance of 2.29 ohms.
>The Bessel arrangement has two drivers connected in
opposite phase so their SPL effectively cancels each
other leaving one driver parallel connected to two in
series. Hence, less SPL vs. a standard 5 drivers in
parallel arrangement.
====
My info says only one driver is wired in reverse
phase, with one pair in series, one pair in parallel.
Assuming this is correct:
One pair in series, and one pair in parallel =
10*log(4/1) = +6dB increase in efficiency.
Half of both the series and parallel pair's output is
negated by the single reversed phase driver, so we're
left with only the +6dB surface area gain added to
the output of what is effectively one driver.
This tells us that whatever the driver's voltage
handling limit is, it's also the limit for the array,
or 33W/8ohms = 16.24V.
Three 8ohm drivers in parallel = 2.667ohms, which in
parallel with 16ohms = 2.286ohms. 16.24^2/2.286 =
115.38W.
So based on my info, the 113dB/115.5W that BBP
predicts is close enough for me. Since peak to
average SPL is ~24dB, this means that each driver
will only need ~0.46W on average.
But of more importance is the better imaging at
greater distances compared to the same drivers wired
conventionally. When a number of these arrays are
ganged together is where the concept really pays off.
Dr. Patronis (GaTech) has built some using large
format horns in outdoor venues which have superior
pattern control/intelligibility compared conventional
arrays.
GM
stinems said:
There's a pretty good tutorial in Don and Carolyn Davis's book that I used to experiment and a couple of folks were real pleased with a HT CC and a stereo BA: http://www.amazon.com/Sound-System-Engineering-Second-Carolyn/dp/0240803051
GM
I have been involved in a commercial Bessel vertical array system some years ago. The front cancellation control is comparable to a conventional line array. But no special ''cylindrical wave'' Mid-HF waveguides are needed so costs and HOMs stay under control.
Also the elements can be broken down and used as common cabinets. Great benefit for the hiring business. Problems are that the available power is not utilized fully due to reversed polarity elements and power tapping. Also the vertical lobe is taller than the array and spills to the stage. But the sound has a natural feel although not as long in reach as a conventional line array, because its a big made up point source bubble.
It's interesting though, that when I was studying various conventional line arrays, it seemed to me that they could be modeled as infinite vertical Bessel arrays rather than long cylindrical sources, which never quite persuaded me, although its the mainstream assumption.
Also the elements can be broken down and used as common cabinets. Great benefit for the hiring business. Problems are that the available power is not utilized fully due to reversed polarity elements and power tapping. Also the vertical lobe is taller than the array and spills to the stage. But the sound has a natural feel although not as long in reach as a conventional line array, because its a big made up point source bubble.
It's interesting though, that when I was studying various conventional line arrays, it seemed to me that they could be modeled as infinite vertical Bessel arrays rather than long cylindrical sources, which never quite persuaded me, although its the mainstream assumption.
http://www.xlrtechs.com/dbkeele.com/papers.htm
Paper #21
http://www.xlrtechs.com/dbkeele.com/PDF/Keele (1989-10%20AES%20Preprint)%20-%20Bessel%20Arrays.pdf
Any relevance? -> http://www.yamaha.com/yec/soundprojectors/
I'm pretty sure Yamaha is also using some form of Optimal Source Distribution as well.
Paper #21
http://www.xlrtechs.com/dbkeele.com/PDF/Keele (1989-10%20AES%20Preprint)%20-%20Bessel%20Arrays.pdf
Any relevance? -> http://www.yamaha.com/yec/soundprojectors/
I'm pretty sure Yamaha is also using some form of Optimal Source Distribution as well.
Not sure if anyone is looking at this thread or not it has been quiet for some time but I figure it is worth a try.
I am curious how this would work in a car If you built an array of 1,2 or 3 inch full range drivers that spanned the entire dash, what would be optimal. If you made a PCV enclosure would it be vented or sealed? Could you share the space with the left and right speakers? I am so intrigued by this concept but do not have the technical back round in audio to decode the raw data to no what to use. If I can get a great bang for the buck driver that would like to try it to be different.
I am curious how this would work in a car If you built an array of 1,2 or 3 inch full range drivers that spanned the entire dash, what would be optimal. If you made a PCV enclosure would it be vented or sealed? Could you share the space with the left and right speakers? I am so intrigued by this concept but do not have the technical back round in audio to decode the raw data to no what to use. If I can get a great bang for the buck driver that would like to try it to be different.
Hi, thanks a lot for sharing this.
In the mountain of information, the single array for stereo grabbed my eyes (as attachment).
What surprises me is the sum signal is distrubuted at 3 positions: far left-center- far right, with both ends attenuated.
And the (partially) differential signals go to the midway between center and far left/right.
Is there any explanation about that?
I've also browsed through the US pat. KSTR mentioned, not much about stereo is brought up.
In the mountain of information, the single array for stereo grabbed my eyes (as attachment).
What surprises me is the sum signal is distrubuted at 3 positions: far left-center- far right, with both ends attenuated.
And the (partially) differential signals go to the midway between center and far left/right.
Is there any explanation about that?
I've also browsed through the US pat. KSTR mentioned, not much about stereo is brought up.
Attachments
Hi,
Reminds me of a build I made first 20 years ago using Phillips AD 5060M4 drivers after acquiring Don Davis/Carolyn Davis: Sound System Engineering book and later tested with Tangband that really was a success:
When Bessel-arrays really should IMO/IME be considered: Adding a suggestion of a small tweeter-array that may be used vertically or horizontally, localization issues blameless above a listening distance of ~5 feet and perfect at over ~9 feet:
b
Reminds me of a build I made first 20 years ago using Phillips AD 5060M4 drivers after acquiring Don Davis/Carolyn Davis: Sound System Engineering book and later tested with Tangband that really was a success:
When Bessel-arrays really should IMO/IME be considered: Adding a suggestion of a small tweeter-array that may be used vertically or horizontally, localization issues blameless above a listening distance of ~5 feet and perfect at over ~9 feet:
b
Attachments
Hi SunRa,
Maybe a clever XO but what about the tweeter-array dispersion?
b
Attachments
I tried a proof of concept idea. Enclosure was only for housing the drivers and didn't concern myself with airspace. I was also using ambiophonic processing. I still preferred adding in a bank of tweeters. The test mules drivers were nothing special, and I destroyed a few for various reasons. The last version I tried was using the peerless 830970 drivers with some mbquart super tweeters. I went another route for cosmetic reasons, plus I wanted a lower midrange crossover point. The need to be "far way" could be debatable. I demoed it at a Michigan meet a few years ago hosted by Tom Nousaine and David Clark and some people seemed to like it.
Cheapo gentoo 2" test mule
New Route (No Bessel)
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Durwood,
Thank you for sharing your build. I will have to look up "ambiophonic processing", since I have no idea what that is. What speakers are you running in the dash now?
I have seen alot of threads discussing theory and some MTM designs but I have not see any that spanned the entire dash. I did see two that were started but not complete. I have a very deep dash in my Suzuki SX4 so it seemed like a good canidate for a Horizontal Line Array on the dash.
I am considering the following set up
MMMTMMM MMMTMMM using the Tang Band W3-881SJF and Vifa BC25SC06-04 1" Textile Dome Tweeter. The Tang Band's will run of one channel of my ADS PH15.2 and the Tweets on the second chanel. Saving the last 2 channels for a pair of Dayton Audio RS180-4 7" Reference Woofer 4 Ohm in a sealed enclosure in the front doors. Of coarse this is all theory but I was hopeing to make a single enclosure giving each driver more airspace to help with the low freq response. This is my first attempt builing anything custom for the car audio wise. I am really looking for something that will not break the bank and can get loud and clean, as well as be different. I think the bigest challange is making it so will still allow the defroster... well defrost the front winsheild.
Phil
Thank you for sharing your build. I will have to look up "ambiophonic processing", since I have no idea what that is
. What speakers are you running in the dash now?I have seen alot of threads discussing theory and some MTM designs but I have not see any that spanned the entire dash. I did see two that were started but not complete. I have a very deep dash in my Suzuki SX4 so it seemed like a good canidate for a Horizontal Line Array on the dash.
I am considering the following set up
MMMTMMM MMMTMMM using the Tang Band W3-881SJF and Vifa BC25SC06-04 1" Textile Dome Tweeter. The Tang Band's will run of one channel of my ADS PH15.2 and the Tweets on the second chanel. Saving the last 2 channels for a pair of Dayton Audio RS180-4 7" Reference Woofer 4 Ohm in a sealed enclosure in the front doors. Of coarse this is all theory but I was hopeing to make a single enclosure giving each driver more airspace to help with the low freq response. This is my first attempt builing anything custom for the car audio wise. I am really looking for something that will not break the bank and can get loud and clean, as well as be different. I think the bigest challange is making it so will still allow the defroster... well defrost the front winsheild.
Phil
I had the same issue about the defroster, still needed it to function. You also have to think about how it would attach so it does not become a projectile.
3" seemed too big for me even though my raised hood created a dead zone. Making an enclosure that is no bigger then the driver is difficult. Maybe your dash sits lower. Before going all out, maybe test with a temporary baffle wedged between the dash and the window in your driveway. Then if you like it, build the real deal.
Here is a 2.5" compared to a 3" vifa TG9
The new drivers are 5" coaxial/concentric BMS 5CN140
3" seemed too big for me even though my raised hood created a dead zone. Making an enclosure that is no bigger then the driver is difficult. Maybe your dash sits lower. Before going all out, maybe test with a temporary baffle wedged between the dash and the window in your driveway. Then if you like it, build the real deal.
Here is a 2.5" compared to a 3" vifa TG9
The new drivers are 5" coaxial/concentric BMS 5CN140
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