Understanding Loudspeaker Coherency

[Big Daddy]

Originally Posted by crazyBLUE

I will see about the crossovers for my Bostons Big Daddy . This is something I have noticed . Best shown in pics , But the 2 midranges are angled different . The lower one is forwart & the upper one is angled up some & the tweeter is even behind them in relative distance . Albeit a small amount .

The important thing is to push the higher frequency drivers back. If the crossovers in your speakers are first order (6dB per Octave), they are time and phase coherent. If the crossovers are higher order, they may not fully satisfy the rules of phase coherence, but I would still give Boston a lot of credit for being innovative.

[crazyBLUE]

Originally Posted by Big Daddy

The important thing is to push the higher frequency drivers back. If the crossovers in your speakers are first order (6dB per Octave), they are time and phase coherent. If the crossovers are higher order, they may not fully satisfy the rules of phase coherence, but I would still give Boston a lot of credit for being innovative.

Thanks for the response Big Daddy !!

[kareface]

There have been some neat tests done on the audibility of phase. Fluctuations in phase tend to be much more audible than minor phase variance, which can come from the heating and cooling of the voice coils on larger drivers or tones that transition between drivers that are crossed over. Phase coherence problems are almost impossible to audibly identify from other issues, and as BD said, there is debate over the extent of its impact on reproduction. Interesting post and informative post as always BD.

[callas01]

Originally Posted by Big Daddy

The important thing is to push the higher frequency drivers back. If the crossovers in your speakers are first order (6dB per Octave), they are time and phase coherent. If the crossovers are higher order, they may not fully satisfy the rules of phase coherence, but I would still give Boston a lot of credit for being innovative.

In this case BD, all Dynaudio speakers use 1st Order 6 db/octave crossovers. You should add them to the list in the first post.

High quality 1st order crossovers
Only the highest quality components, selected for their sonic properties, are utilized in Dynaudio crossovers: carefully wound pure OFC (oxygen-free copper) air-coils, select capacitors, and temperature-stable ceramic resistors. A Dynaudio crossover features pure 1st order filters (6 dB/octave), which enable a superior transient response and can only be effectively used with the ultra-linear frequency response of the Dynaudio drivers. Another Dynaudio area of expertise is impedance correction, making a perfect combination possible with virtually all amplifiers

[BigAl87]

Originally Posted by callas01

In this case BD, all Dynaudio speakers use 1st Order 6 db/octave crossovers. You should add them to the list in the first post.

Don't forget rule number 2 Steve. If Dynaudio meet the specs with all their speakers then the Hawk has to be there which brings me to if my ears are directly beween the Midbass driver and the tweeter I technically have a perfectly coherent speaker persay.

So the Hawk could qualify as a coherent speaker.

[callas01]

Originally Posted by BigAl87

Don't forget rule number 2 Steve. If Dynaudio meet the specs with all their speakers then the Hawk has to be there which brings me to if my ears are directly beween the Midbass driver and the tweeter I technically have a perfectly coherent speaker persay.

So the Hawk could qualify as a coherent speaker.

whats interesting is that the part I bolded states, that not only does each speakers drives reach the listener at the same time, they also retest to make sure each PAIR of speakers are time-phase aligned.... another reason why dynaudios are so well built.

Dynaudio directivity control
The distinctive driver symmetry with two mirrored drive units is an unmistakable characteristic of the Dynaudio directivity control (DDC) technology. After years of development experience with Dynaudio professional studio monitor loudspeakers, it became clear that many recordings are of superb quality but, due to listening room acoustics, the potential of these recordings could not be fully experienced. In particular, reflections from floor and ceiling boundaries interfere with a faithful, realistic sonic reproduction because of distortions and added time delays. With DDC, Dynaudio has created a technology that effectively reduces these effects. The vertical symmetrical drive unit array and elaborate crossover topology reduce the energy dispersed to the floor and ceiling by approximately 75 percent. The controlled vertical dispersion makes the loudspeaker far less dependent on the room and much less influenced by positioning as compared to conventional designs. DDC isn’t simply arranging the drivers in a symmetrical array. For DDC to succeed, every single detail – from each drive unit to the crossover – must be individually tailored and optimized for this concept. With two tweeters, two mid-range drivers and, depending on the model, two or four woofers, each drive unit complements its identical counterpart in frequency response and phase relationship in such a manner that a carefully defined dispersion characteristic is achieved. This intricate matching is repeated once again for each loudspeaker pair to work together in tandem. DDC is an impressive example of the innovative Dynaudio methodology for loudspeaker design and is truly without equal.

[BigAl87]

Originally Posted by callas01

whats interesting is that the part I bolded states, that not only does each speakers drives reach the listener at the same time, they also retest to make sure each PAIR of speakers are time-phase aligned.... another reason why dynaudios are so well built.

Yes each of the speakers are time phase aligned and not ech of the drivers in each speakers, look at the figure with the Wilson Audio to really understand what they meant.

Any how I know totem does the same they test tone the drivers to pair them together properly and then the built the cabinets with the wood grain that has the closest possible match and retest to make sure the end result is as good as it was originally tested which is one of the reasons Totem have such strong imaging.


Anyhow does not mean because a speaker is not perfectly coherent it's soes not sound fantastic, in a perfect world you would always have to sit in the perfect spot with your ears at a pefect hight to reach perfect coherency. Nearly impossible if you ask me, as if you ear are 2 inches higher than me when you sit and I actually have perfect coherency than you are off.

[Big Daddy]

Originally Posted by callas01

In this case BD, all Dynaudio speakers use 1st Order 6 db/octave crossovers. You should add them to the list in the first post.

I did not intend to list every phase coherent speaker in post #1. I just used a few examples to help people understand phase coherency. I also added a few more to post #2. Unfortunately, there is a limited number of characters that you are allowed to include in one post. If you need additional room, you need to make another post.

The fact that you mentioned Dynaudio is good enough. If you want, you can always add a few pictures.

[Big Daddy]

Rockport Technologies Altair is another example of conherent speakers. They weigh 515 pounds each and cost $97,500 a pair. Their drivers are made by Audiotechnology in Denmark and some of them are made by Dynaudio.

Their Arakis speakers weigh 900 pounds each. They are $165,000 a pair. Most houses will probably collapse if you put a pair of these on the second floor. Each speaker has two(2) 15" subwoofers, two (2) 8" midbass drivers, two (2) 5.25" midrange drivers, and one 1" tweeter. The height is 81", the width is 24:, and the depth is 36.5".

Another speaker that has the curved baffle is the Gryphon Poseidon speakers. They are only $140,000. Their other speakers are also coherent.

[jsr]

Originally Posted by Big Daddy

Sometimes the differences in phase response at frequencies shared by different drivers can be corrected by adjusting the vertical location of the smaller drivers (usually backwards), or by leaning or stepping the front baffle, so that the wavefront from all drivers is coherent around the crossover frequencies. The center of the drivers determine the amount of rearward offset to time-align the drivers.

Gotcha. The leaning is used to accomplish the same task as stepping the baffle.

[prerich]

Originally Posted by Big Daddy

I did not intend to list every phase coherent speaker in post #1. I just used a few examples to help people understand phase coherency. I also added a few more to post #2. Unfortunately, there is a limited number of characters that you are allowed to include in one post. If you need additional room, you need to make another post.

The fact that you mentioned Dynaudio is good enough. If you want, you can always add a few pictures.

Ok BD - I have a question - is there a listening distance where Time-Alignment doesn't serve a function (or that the benefit would be unnoticable)? As most speaker designs are a compromise of some sort, say dynamics for imaging ect. Where would the benefit of Time Alignment be most noticable - when sitting further away from the speakers (since this would mean a farther distance for each indiviual wave to travel before reaching the listener - making the waves more out of time with each other)?

[Big Daddy]

Originally Posted by prerich

Ok BD - I have a question - is there a listening distance where Time-Alignment doesn't serve a function (or that the benefit would be unnoticable)? As most speaker designs are a compromise of some sort, say dynamics for imaging ect. Where would the benefit of Time Alignment be most noticable - when sitting further away from the speakers (since this would mean a farther distance for each indiviual wave to travel before reaching the listener - making the waves more out of time with each other)?

Time alignment and angling of the drivers depends on the height of the ears and distance from the speakers.

As I indicated in Post #1, Richard Vanderseen is the champion of time and phase coherency. He has designed speakers so that you can adjust the backward tilt of the speaker so that all the drivers are perfectly synchronized and their signals converge at the listener's ears. The angle of tilt depends on how far the listener is from the speaker. In their owner's manual, there is a graph that tells you the required amount of offset in relation to the distance of the listening position.

The image is from the Vandersteen 3A Manual.

CoherentSpeakers.jpg

[Matty_J]

Does Rockport Technologies include modest forklift with those asking prices?
How else can one move those beasts?

[Big Daddy]

Originally Posted by Matty_J

Does Rockport Technologies include modest forklift with those asking prices?
How else can one move those beasts?

You buy them first and then build a house around them.