Poly Directional Loudspeakers

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Letitroll98

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Re: Poly Directional Loudspeakers
« Reply #20 on: 23 Apr 2017, 01:15 pm »
In describing Allison speakers I have heard the term uniform power response. See the picture below. Unfortunately as Letitroll98 indicated getting a pair in pristine shape is impossible given what the state of the art was in materials for loudspeakers back in the 80s.

Someone should resurrect his design principles and make a few models.


http://img11.hostingpics.net/pics/599524allison1.gif

They actually did, somebody acquired the rights to the name and designs, the 3's were being offered around the $5k mark.  I bought mine for something around $750 back in the 80's.    The company didn't last long and a quick search didn't bring up any online remnant.

LostInPA

Re: Poly Directional Loudspeakers
« Reply #21 on: 23 Apr 2017, 02:52 pm »
https://www.youtube.com/watch?v=ms_klvWfJ3w

JBL Aquarius IV [aka Model S109] - incorrectly spelled in attached video.   Purchased new by me in 1973, sold 2 years ago.   Crossovers rebuilt twice, main driver reconed twice.

Main driver was upfiring LE8T-2 [-2 = hard dustcap], in to a conical deflector.   Rear firing tweeter, in to a curved deflector to spread sound horizontally parallel to rear wall, therefore recommended placement was close to rear wall.  Quality of tweeter not up to quality of main driver.   I purchased a pair of fabric dome tweeters, made deflectors, and positioned these on top of the speaker cabinets, tweeters now "co-axial" to main driver.   New tweeters had similar specs to original.   Original crossover has a tweeter level control, which was useful.





joerest

Re: Poly Directional Loudspeakers
« Reply #22 on: 24 Apr 2017, 10:15 am »
While at Axpona try looking up Duke LeJeune's Audio Kinesis (not sure he or his speakers are there this year).  One of the concepts he pushes is controlled directivity.
Back in the 70's I learned to unlike B&O speakers for their dry, constipated, un-involving sound.
No; Duke LeJeune's Audio Kinesis is not at Axpona this year. There was a speaker here called the Kii. It has multiple drivers radiating from the bottom, sides and rear. There is a DSP processor built in the enclosure that feeds out-of-phase signals to each of these drivers to counter the main signal radiating from the front baffle. These secondary signals are meant to absorb the main signal which would have otherwise wrapped around the enclosure and exhibited phase distortion. As you said, sort of an opposite omnidirectional pattern. Bass was remarkable for a fairly small stand speaker. Otherwise the speaker was just OK. As for B&O, I too always found their speakers technically well defined, but not very real and natural sounding. The 90's however are another kettle of fish. Found them unremarkable for other reasons.

« Last Edit: 5 May 2017, 07:00 pm by joerest »

Duke

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Re: Poly Directional Loudspeakers
« Reply #23 on: 12 May 2017, 05:31 am »
While at Axpona try looking up Duke LeJeune's Audio Kinesis (not sure he or his speakers are there this year).  One of the concepts he pushes is controlled directivity (like the mighty JBL M2 mastering speakers).  The idea is to minimize sonic energy that hits walls/ceiling/floor and reduce the associated smearing.  Sort of the opposite of poly/omni directionals.  Duke also believes in reducing thermal effects in drivers, so leans towards high efficiency professional drivers.

I wasn't at Axpona this year.

My best speakers have been poly-directionals.  I use a narrow-pattern array of drivers aimed towards the listening area, the purpose of the narrow pattern being to minimize early reflections.   Then I use a second array, also with a narrow pattern, aimed in a direction that will produce as much time delay as is reasonably feasible before that energy reaches the listening area.   

The intention is to get a clean first arrival sound, then minimal early reflections (those arriving within about 10 milliseconds of the first-arrival sound), then a generous amount of relatively late-onset, spectrally correct reflections.

Since the ear/brain system uses the time delay between the first-arrival sound and the onset of reflections to gauge room size, this approach can make it sound like the room is bigger than it really is, and therefore like the soundstage is also pretty big.

JLM

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Re: Poly Directional Loudspeakers
« Reply #24 on: 12 May 2017, 11:32 am »
Only to try clarifying what Duke said (wouldn't dream of stepping on his toes) ...

His speakers (front radiators) are designed to be turned 45 degrees into a rectangular room to minimize first reflections off front/side walls.  Secondary speakers/drivers are designed to provide delayed ambience reinforcement (from Jim Romeyn's "Late Ceiling Splash" concept).  The idea is to make the room seem bigger by generating a second source per channel that has at least a 10 millisecond delay (as the brain will separate that amount of delay from the original sound wave).  These secondary speakers/drivers cover midrange/treble frequencies and are placed directly behind the main speakers/drivers to provide the extra distance (11 feet needed based on the speed of sound being 1100 feet per second) to create the 10 millisecond delay.  Proper in-room bass is addressed using his "Swarm" of 4 subwoofers placed near the corners of the room.

With Duke's help I've installed a super cheap version of "Late Ceiling Splash" using a $20 Parts Express tweeter with a protective capacitor in series that lay on the floor pointing up directly behind my floor standing single driver (8 inch, whizzerless) speakers.  The tweeter is wired in parallel with the the single driver speakers.  It works!  It adds treble response/dispersion and a larger soundstage (allowing the speakers to be pulled farther apart without losing the center of the soundstage).

Duke

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Re: Poly Directional Loudspeakers
« Reply #25 on: 12 May 2017, 08:27 pm »
Only to try clarifying what Duke said (wouldn't dream of stepping on his toes) ...

His speakers (front radiators) are designed to be turned 45 degrees into a rectangular room to minimize first reflections off front/side walls.  Secondary speakers/drivers are designed to provide delayed ambience reinforcement (from Jim Romeyn's "Late Ceiling Splash" concept).  The idea is to make the room seem bigger by generating a second source per channel that has at least a 10 millisecond delay (as the brain will separate that amount of delay from the original sound wave).  These secondary speakers/drivers cover midrange/treble frequencies and are placed directly behind the main speakers/drivers to provide the extra distance (11 feet needed based on the speed of sound being 1100 feet per second) to create the 10 millisecond delay.  Proper in-room bass is addressed using his "Swarm" of 4 subwoofers placed near the corners of the room.

With Duke's help I've installed a super cheap version of "Late Ceiling Splash" using a $20 Parts Express tweeter with a protective capacitor in series that lay on the floor pointing up directly behind my floor standing single driver (8 inch, whizzerless) speakers.  The tweeter is wired in parallel with the the single driver speakers.  It works!  It adds treble response/dispersion and a larger soundstage (allowing the speakers to be pulled farther apart without losing the center of the soundstage).

Very good descriptions - thank you!  Glad the upfiring tweeter is working out too! 

Nick B

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Re: Poly Directional Loudspeakers
« Reply #26 on: 12 May 2017, 09:06 pm »
I owned Shahinian Diapasons for years and really enjoyed them. They were in my living room which had a vaulted ceiling and gave me a very spacious presentation.  I wish I had them now just to see how they would do with my current amp and dac (McCormack DNA 1.0 and Antelope Gold)
I enjoy my current front firing speakers (SP Tech Timepieces). Among other attributes, I like the detail that the SP Tech provides.

Duke

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Re: Poly Directional Loudspeakers
« Reply #27 on: 13 May 2017, 05:20 am »
I owned Shahinian Diapasons for years and really enjoyed them. They were in my living room which had a vaulted ceiling and gave me a very spacious presentation.  I wish I had them now just to see how they would do with my current amp and dac (McCormack DNA 1.0 and Antelope Gold)
I enjoy my current front firing speakers (SP Tech Timepieces). Among other attributes, I like the detail that the SP Tech provides.

Very interesting. 

Imo the Shahinians and the SP Techs have more in common than is apparent at first glance:  Both do a good job of establishing a spectrally-correct reverberant field, though their radiation patterns look very different, and their respective direct-to-reverberant sound ratios are very different.  Apparently the key is, getting the reverberant sound to have the same spectral balance as the first-arrival sound.

Those aren't the exact words Floyd Toole uses, but I think the general idea is the same:

"In all of our loudspeaker evaluations, over several decades now, the highest scores have gone to those with the most uniform directivity, not the highest or any particular directivity. In fact one of the highest scoring loudspeakers for a period of time in the NRCC double-blind evaluations was an essentially omnidirectional bipole design, which would generate maximum reflections from all vertical surfaces. This makes sense in that the precedence effect would remain intact because there is a spectral similarity between the direct and reflected sounds. That was a learning experience." - Floyd Toole, "Room Reflections & Human Adaptation for Small Room Acoustics"

joerest

Re: Poly Directional Loudspeakers
« Reply #28 on: 21 Jun 2017, 03:21 am »
Since I started this topic, I was reconsidering my view of direct vs some type of omnidirectionality. At first completely abandoning poly/omni directionality to front firing seemed most logical. But after almost 8 years of living with single directional speakers, I was not quite sure either philosophy was correct. I therefore auditioned the ClairAudient 1+1 V2+ in my sound room. For those who are not familiar, these are dipoles. The two active three inch drivers face opposite baffles. A front and rear baffle. The two active drivers operate in phase. They also share a single loading chamber. The two sides contain passive radiators to support bass frequencies. At first I thought these were the perfect compromise. After a little over a week of intense listening, I returned them to Audience. I was very happy to return to my single radiating transducers. I now know I will never return to any kind of poly or omni directionaliy. Whereas the 1+1's  did many things right, (especially in the midrange), I could no longer tolerate the nebulous larger-than-life vocal image and lack of pinpont locality.  For someone who lived with some type of multiple directional speakers for close to 40 years, I was done. My biggest objection is how they create their own space. In my case the Audience redefined the listening space by doing just that. I was looking for a speaker to be symbiotic with the domestic environment, not one that creates it's own.
« Last Edit: 21 Jun 2017, 05:54 pm by joerest »

planet10

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Re: Poly Directional Loudspeakers
« Reply #29 on: 21 Jun 2017, 05:33 am »
… ClairAudient 1+1 V2+ in my sound room. For those who are not familiar, these are dipoles. The two active three inch drivers face opposite baffles. A front and rear baffle. The two active drivers operate in phase. They also share a single loading chamber.

They are not dipoles, they are bipoles.

dave

joerest

Re: Poly Directional Loudspeakers
« Reply #30 on: 21 Jun 2017, 07:00 am »
Thanks Dave for the correction. They are in fact a bipole with a twist. Due to their small size and close proximity of the two active drivers, Audience updated to the V2. This design change added a tank circuit to eliminate a null at 540 hz. So in actuallity the phase of the two drivers are electronically manipulated. Nevertheless this detail is a side issue from the point I was trying to convey.

Joe.
« Last Edit: 21 Jun 2017, 11:08 am by joerest »

planet10

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Re: Poly Directional Loudspeakers
« Reply #31 on: 21 Jun 2017, 07:03 am »
This design change added a tank circuit to eliminate a null at 540 hz.

All bipoles with drivers on the front & the back suffer what is called a bipole dip. This frequency is about right for the size of the box.

dave

JohnR

Re: Poly Directional Loudspeakers
« Reply #32 on: 22 Jun 2017, 04:47 pm »
I now know I will never return to any kind of poly or omni directionaliy.

It's a bit radical to judge a whole sphere (pun only half intended) of loudspeaker design based on a single example...

joerest

Re: Poly Directional Loudspeakers
« Reply #33 on: 23 Jun 2017, 01:37 am »
JohnR: I mean no disrespect, but I have been living with omni/poly directional speakers for over 40 years. I make no audiophile decisions based on a single anything. Why can't we have a constructive discussion on what we all love, rather than criticizing or correcting each other. I would love simply to share experiences and old audio war stories.

Joe

joerest

Re: Poly Directional Loudspeakers
« Reply #34 on: 26 Jun 2017, 12:13 am »
Wan't to thank JLM for giving me an idea. Just for giggles I turned my Townshend Maximus supertweeters around 180 degrees. They now face the wall behind the speakers.  Don't know if they give me more "air", but it certainly does not detract from the high frequencies. The bass remains improved, but it did some magic to the mids. Not convinced that this will end up to be the final configuration, but will add it to the credible possibilities. Very supprised that it did not detract from the high frequency perception.  Highs do sound a bit fatter though. Will live with it for a week or so and let you know results.

Joe

joerest

Re: Poly Directional Loudspeakers
« Reply #35 on: 2 Jul 2017, 01:28 am »
Lived with the Townsend Maximus supertweeters turned around 180 degrees for a few days. The back facing tweeters were resulting in distortion on leading edge transients. Settled with them front firing at the lowest possible volume setting. This setting (#1) also results in a frequency response which kicks in at about 9 or 10hz. Good results. Once again IMHO direct radiation wins over Omni/Poly directionality.

Joe