Line Source Dipole Versus Point Source Cone: Which Soundstage Presentation is More Realistic?

[Ron Resnick]

Different topologies of loudspeakers offer different presentations of soundstage. To many audiophiles a planar dipole offers a soundstage presentation which sounds different than the soundstage presentation offered by dynamic drivers in boxes.

Do you prefer the soundstage presentation of a line source or of a point source?

How would you describe the differences in soundstage presentation?

And what about a D'Appolito line array of dynamic drivers such as the Evolution Acoustics MM7, Tidal La Assoluta, Gryphon Kodo, Rockport Arrakis, VSA Ultra 11? Does the soundstage presentation of this design come closer to the soundstage presentation of a planar dipole or of a point source?

 

[dcathro]

I always find the presentation of point sources to be more realistic - images are smaller and closer to what I believe to be real.

Apart from Quad 63s with their delay mechanism, I have always found panels to make images larger than life.

 

[Duke LeJeune]

Which creates the most realistic soundstage presentation... hmmm...

At the risk of over-generalizing:

Ime good point-source-approximating monopole speakers tend to produce more realistic sound image localization, including more realistic separation of individual voices and instruments.

Meanwhile, ime good line-source-approximating dipole speakers tend to create the more realistic illusion of "you are there", immersed in the three-dimensional soundscape on the recording. (Good omnis can do this too, under favorable conditions.)

The Quad 63's mentioned by @dcathro are point-source-approximating dipoles. Ime the narrow-pattern, line-source-approximating Sanders Sound hybrid electrostats also tend more towards the "precision sound images" end of the spectrum, rather than the "immersion" end of the spectrum. So it depends on the specifics, surprise surprise. And the one does not necessarily preclude the other!

In my opinion it is the earliest in-room reflections that are the most detrimental to both precise sound image localization and a "you are there" presentation, while the later-arriving in-room reflections can facilitate a "you are there" presentation, BUT if the late reflections are too loud, they will degrade both image precision and overall clarity. Big rooms push the arrival times of the first reflections back in time, tipping the presentation more towards "you are there" regardless of which type of speaker is used, WITHOUT degrading image precision.

Imo the large expanded-D'Appolito speakers are a special case of the point-source-approximating monopole, and this is one of their spatial quality advantages: They inherently have less floor and ceiling interaction than more conventional monopoles. Such speakers tend to end up in big rooms with long reflection paths, wherein they tend to do well at creating a "you are there" presentation, thanks in large part to those long reflection paths.

If I had to pick between realistic and precise sound images and a convincing "you are there" presentation... well I would probably pick the latter, but not by a huge margin. I'd like to have both, of course!

 

[Robh3606]

Interesting question. When I had my 2 way Heil set-up I experimented with level of the backside radiation pattern. No attenuation and it was a more immersive sound field with vague focus. If I attenuated the back wave completely I ended up with a more point source more focused presentation. I ended up with a moderately attenuated back wave that was to me a good balance between the two.

I see it as really a preference issue. In real life you don't get point source imaging so to me a balance between the 2 is more "realistic" for lack of a better word but that's just me.

Rob

 

[Duke LeJeune]

Interesting question. When I had my 2 way Heil set-up I experimented with level of the backside radiation pattern. No attenuation and it was a more immersive sound field with vague focus. If I attenuated the back wave completely I ended up with a more point source more focused presentation. I ended up with a moderately attenuated back wave that was to me a good balance between the two.

Very interesting!

How were you attenuating the backwave of the Heil? And if you recall, about how far in front of the wall were the Heils?

 

[morricab]

As I have always had line sources that were also dipoles this is a confounding factor in the spatial presentation. Monopole line sources don't seem to have as much a spatial advantage as dipoles, which throw half their sound around the room. Dipole line sources do have generally larger and more "walk around" soundstages and if toed-in correctly, still getting a very precise imaging.

A lot of Duke says is pretty accurate from my experience.

 

[Robh3606]

Very interesting!

How were you attenuating the backwave of the Heil? And if you recall, about how far in front of the wall were the Heils?

Hello Duke

I was using fiberglass batting or felt of different thickness's and combinations. I ended up with a square of fiberglass batting right behind the driver.

Distance? From close about 2ft to about 4 ft measured from the backwall the driver toed in towards the corners. There is a rug in front. The backwall, sidewall and ceilings all reflective.

Here's a couple of pictures.

It was a fun experiment!

Rob

 

[Duke LeJeune]

I was using fiberglass batting or felt of different thickness's and combinations. I ended up with a square of fiberglass batting right behind the driver.

Distance? From close about 2ft to about 4 ft measured from the backwall the driver toed in towards the corners. There is a rug in front. The backwall, sidewall and ceilings all reflective.

Hi Rob,

Thanks for the information and pictures! BEAUTIFUL room and setup!

And imo you DID IT RIGHT by using a thick enough layer that the absorption was over the entire frequency range that the Heil was putting out. A thin layer that only absorbed the short wavelengths would have, in effect, degraded the spectral balance of the rear-firing energy.

Was there any correlation between how much rear-firing energy sounded best and how far out from the wall the Heils were located? I would guess that the further from the wall, the more rear-firing energy you could get away with before clarity and/or image precision started to be degraded. Did you notice anything like that?

 

[DasguteOhr]

big coax speaker 12~15" with horn driver make realistic razor-sharp arrangement of musicians and instruments possible for me. this big advantage over other concepts is not for nothing. a big cone e.g. 15" usually breaks up just under 1khz and starts to bundle strongly (increase in sensitivity) if you want to operate something like this without xover you have to work with a notch filter to prevent the increase. if you manage that you have a very good speaker.
I went a step further, so to speak, a Frankenstein speaker with a 15" coax in an open baffle. I opened the horn drivers on the back ( lower distortion ) so that the coax works as a complete dipole and point source. A bit of a mix of two worlds. You get a great soundstage in width and depth coupled with the advantages of the coax. I can recommend everyone to try it out.
Of course it's only for DIY people, if you want to hear a concept that you can buy and that produces a similar result then please listen to Bastanis speakers.

 

[Robh3606]

Was there any correlation between how much rear-firing energy sounded best and how far out from the wall the Heils were located? I would guess that the further from the wall, the more rear-firing energy you could get away with before clarity and/or image precision started to be degraded. Did you notice anything like that?

Hello Duke and thanks

It was an evolution over time. I tried several placements with no back wave attenuation and ended up with a position where I felt I had the best image. If I dropped them closer to the corners imaging would degrade but it was really hard to "hear" where the speakers where. It was one big vague sound stage around the room.

Once I had the best image I tried attenuating the back wave and imaging improved but the sound field got smaller, if that makes any sense. So I ended up with a balance biased towards imaging. I should have done a couple of snap shots to measure the attenuation but never did so it was completely subjective.

Rob

 

[Alrainbow]

I never was a box speaker guy but I have changed
a line source that only fires at you still fires behind
it’s the distance between you and them that effects things
tow helps fix if needed but some tow is bad
one thought is Any line source is 3 db compared to 6 db lower in sound level per distance
so distance matters a lot
at last year and this year box speakers were the shows top rooms
my thoughts