Dunlavy vs JM Lab

Calanctus:

To answer your question without too much technical detail:

1. A speaker that is time-accurate means that the drivers are arranged in a spatial relationship to the listener so the sound they produce arrives at the listener's ear at the same time. This can be done by mounting the drivers on a baffle that slopes away from the listener, or by tilting the speaker away from the listener. The objective is to ensure that the audio signals from each of the drivers hit the listener's ear simultaneously, as is true of live sound.

2. A speaker that is phase-accurate means that there is very little or no difference in the phase relationship between the audio input signal from the amp, and the movement of the driver(s). You are probably familiar with speaker phasing in regard to the connection of speaker wires: if you reverse the positive and negative leads of one speaker (relative to the other speaker), then the drivers of one speaker will be moving forward while the drivers of the other speaker are moving backward. This leads to acoustic cancellation because the phases of the two signals are opposed.

In the context here, being "phase-accurate" has a somewhat different connotation. A speaker that is phase-accurate uses a first-order crossover, which results in the drivers responding in the same, or nearly same, phase as the input signal. Crossovers of the second, third, fourth, etc., order shift the phase relationship, so the speaker movement may be 45 degrees to 180 degrees out of phase with the input signal.

There are a number of positive aspects to using a first-order crossover in a speaker, but there are some design problems that must be overcome:
1. first-order crossovers are usually of lower efficiency than higher-order crossovers;
2. the components in a good first-order crossover, such as the resistors and capacitors, must be of high quality;
3. the drivers used with first-order crossovers must be of high quality and closely matched to ensure flat frequency response.

There are very few speakers that are both time- and phase-accurate. Three of the best known are Dunlavy, Thiel, and Vandersteen, and each has a distinctive "family" sound. (Actually, I think most speakers that are made by companies headed by someone who is pursuing a personal vision of speaker design -- as in the case of John Dunlavy, Jim Thiel, Richard Vandersteen, and Jacques Mahul of JM Labs -- tend to have an identifiable family "sound".)

Our man Sean is the technical guru in this discussion, so I will let him add any clarifying remarks.

Sean, that story about the cables cracks me up. Nothing like a little accuracy upstream to show a speaker's true colors, eh? I tried for a long time to build systems around Focal drivers and just never could get them to sound "natural", a quality which I am completely unable to define scientifically but one which is present in the Dynaudio, Scanspeak, and Skaaning drivers and very little else. Maybe this is the same as your adjective "wooden".

On the subject at hand, I think that time and phase coherence are of extraordinary importance, provided of course that everything else is taken care of too. There are very few multi-driver speakers in the world that actually achieve this. Vandy/Thiel/Meadowlark are only time-coherent at a particular listening angle, and don't have spatial coherence. Dunlavys are symmetrical, which solves the spatial issue, even though they too will only be truly correct on the tweeter axis. I think that the weakest link in the Dunlavys is the cabinet: a big slab-sided box tends to sound like one, nothing you can do about it. But they do sound a lot more accurate overall than the JM Labs. It depends on your tastes and it's certainly worth making the effort to hear them both at this level.

Thanks for your attention and detailed explanations of the various points. To answer your question, it will be primarily be a two-channel system with some occasional double duty. I will be driving them with the Classe's. My room dimensions are currently 19' by 23'.

GJames

Gjames, a lot has been said about the Dunlavy and JM Labs. All I can add is that Dunlavy V'sare the most accurate speakers I have ever heard and been satisfied with them since last 5 years. Classe and Dunlavy make a good match with right cables. Due to the reasons mentioned above regarding time coherent feature, the dunlavy's have to be PRECISELY located and towed w.r.to the listening position. A 1/4 " or 5 degree difference can upset a balance. As big they are , they do disappear sound wise bar the visual aspect. I still get amazed at times at the accuracy of the sound at all freq spectrums. Sealed enclosures produce tight and accurate bass at the precise location in a sound stage. In fact the bass is so accurate and subtle that you don't even notice it untill you feel it (?). (Non precise placing effects the bass aspects the most) It does not draw attention it itself. The V's ( and I am sure VI's) do need ample power to shine ( CA-400 is what I use). Grills off listening is my preference. I could go on. But I would says this that you should listen to both speakers yourself !

If you like the JM Lab sound, consider Osborn loudspeakers. They use the best of the same brand Focal drivers, possibly have more solid cabinets, and are much better value than JM Lab.
Details including reviews at www.osbornloudspeakers.com.au/
For example, the "Epitomes" with bass bins, while bulky, sound very impressive - natural, dynamic, hard to fault.

Rick