Jordan JX6 full-range line array

[bcherry]

The JX6 4-driver line array has been in our office for a few months now. This spiderless driver's strengths are tremendous coherence and seamlessness. Within it's range it is lightening quick and never fatiguing.
Each driver has about 24sq/cm of surface area. x4 drivers would give about 100sq/cm or roughly equivalent to one 5 1/2" full range driver. Dynamics must be limited then to the amount of air that limited surface can move. By comparison the 10" Ciare we have here is a noticeably more dynamic-sounding (despite it limited Xmax) but it has ~320sq/cm. So it should be expected to move a lot more air with more than 3x the surface area, within its range. But in every other respect the Jordan beats it by a country mile. Our listening area is large, >1000sq/ft so ability to move air is an issue. Interesting that the 4 driver array has the same subjective efficiency as the Ciare - at the listening position.

What if we were to double or triple the number of drivers in our Jordan line array? 8 drivers would give ~200sq/cm of cone, roughly equivalent to an 8" driver (Lowther, Supravox territory) . x12 would be almost 300sq/cm, a little more than a 9" driver.
These little wonders are expensive so for this project I've acquired 16 more drivers, 2 x 8driver arrays. If it seems advantageous, I can always add the existing 4 drivers to make it a 12 driver array.

Noted are some comments about full-range drivers being problematic in line arrays. I haven't found that to be the case so far and frequency distribution in our room measures roughly similar to to single full range driver. No combing is evident. The JX6 do mount fairly close together. I tried the suggested EQ from the Jordan site but then removed it; it was for the JX53 which is no longer made and quite a different driver. The JX6 sounds more lively without EQ.

We will see what the 8 driver array brings.

The Jordan website suggests using the linked design for the box. It's not the typical configuration for a line array but those that have heard it at Ted Jordan's home report that it sounds great. It would certainly suit the small listening environments we have here in a typical Hong Kong flat.

So wondering what you think? Has anyone built the cabinet as shown? Or any comments on it? Caveats etc welcome.

Whichever cabinet I go with will be built in stackable 4-driver enclosures.

Brian

[Scottmoose]

The stackable is probably a good move. I suspect the short array works because of the driver size, and that it's intended for the far-field (the opposite of most line-arrays). If you increase the array lenght, you'll also shift the transition between near and far-field further back, and I suspect because of this (i.,e you'll probably begin to end up in the nearfield), you'll start to run into lobing issues in the HF. Tred carefully. Going stackable means you'll have a fall-back. Other option would be to create a curved array. I'm not a fan because of the tiny sweet-spot they provide, compared to a regular arrays huge 'sweet area' as Jim Grifin describes it. But it should help focus the HF a bit.

Best
Scott

[Colin]

Hi Brian

I'm also running the JXR6 but as singles. To throw a spanner in the works, I believe that the next step up from a 4-unit array is actually a 9-unit set up, then the 16 after that. I have the write up about it somewhere and will dig it out.

The box design on the Jordan site for the array is designed to mount against a wall. Sounds good but the best I heard was a prototype using the JX53 array in a closed box similar in size and shape to the VTL (wide and shallow). Maybe scaling it up would be too visually overpowering for a 9 or 16 array. The Jordan drivers are generally quite sensitive to back reflections so anything you can do to reduce this, the better.

Colin

[bcherry]

Thanks Scott and Colin,

Scott:

If you increase the array lenght, you'll also shift the transition between near and far-field further back, and I suspect because of this (i.,e you'll probably begin to end up in the nearfield), you'll start to run into lobing issues in the HF.

I will pay attention to the nearfield/farfield issue as we have a big room for testing but if I take them home they most definitely will be listened to closeup about 8ft from the drivers. At the office I can get up to 30ft from the speakers.

Colin:

I believe that the next step up from a 4-unit array is actually a 9-unit set up, then the 16 after that. I have the write up about it somewhere and will dig it out.

Interesting, would really appreciate knowing more.

Sounds good but the best I heard was a prototype using the JX53 array in a closed box similar in size and shape to the VTL (wide and shallow).

That sounds interesting as well. Was that used with EQ and against a wall? Is there a source for more info? The 4 driver array I have is also in a wide flat sealed acrylic box, firing straight ahead. Not against the wall though.

The Jordan drivers are generally quite sensitive to back reflections so anything you can do to reduce this, the better.

Internal cabinet reflections? I held the diaphragm of the JX6 and it is is almost imperceptibly light. It makes sense that back reflections could easily excite the back surface and muddle up the sound radiating from the front.

Thanks, gentlemen, for the comments.

Brian

[Dumbass]

My prediction is that combing issues will seriously come into play with larger lines.

[Scottmoose]

That's two of us. The polar response is going to look very ragged, with severe lobing in a nearfield array, and pretty dramatic attenuation of the highs. I know the Jordans aren't large and havce narrow surrounds, which will push it a bit higher than most other units, but you can't bypass the laws of physics. As I say, I suspect the only way to mitigate against this will be to construct a curved array rather than a line array, which will help focus the treble energy. It's probably the only thing you can really do, nearfield array-wise, with full rangers. I'm still not convinced, but I think that way you'll at least be giving yourself a better chance of something workable.

I honestly hope I'm wrong. But I'm pretty sure I'm not.

Interesting remarks re the rear of the cone. Probably lining the rear of whatever enclosure with thick foam or rubber would be a good move?

[Will]

What about doing something similar to the BD-design; instead of using the FE206, use a single Jordan as a wide ranger 200hz upwards, and supplement the bass with 2x15 incher 200hz below. I think that should sound awesome.

[Colin]

Hi Brian

I'll dig out details about the 9-unit array later today and try to post this evening.

Ref the VTL box, this was a prototype, plain sealed box with no EQ or anything fancy. It was the extra volume and the wide baffle which made the difference and re the latter, it was out in the room, so using the cabinet you describe against a wall would take care of that.

Regarding the combing issues, I suspect Ted's design takes care of this as the JXR6 was always designed to be used in an array and it's something he's worked on since the mid-70s. The only mild effect I've heard is when you are close to the array (6 feet or so) and you stand so that your ears are well above the array, then the HF tails off.

I wouldn't recommend using a focused array as that may negate the effect Ted was trying to achieve (image stability irrespective of where you stand in relation to the speakers). If a curved array worked, I'm sure he'd be recommending it on his website.

[Scottmoose]

Agreed to an extent. I dislike curved arrays myself. My concern is that to the best of my knowledge he's not recommending a tall array on his site either. A short array with small full-range units will usually still place the listener in the farfield, so integration should still work, but an extended one shifts this to nearfield, and no matter what you do, the driver centres, which are the bits producing the HF will still be physically too far apart. Checking Jim Griffin's white paper & the other general math, I'd expect attenuation to kick in from ~15Khz, with an increasingly rough response about 1KHz below that.

[Colin]

The image below is a copy of one in Ted's 1963 Loudspeakers book, in which he talks about using multiple, widebandwidth drivers. The aim was to get increased power handling to enable smaller units to be used which would have a better transient response than larger cone drivers. He says:

"the number of units used must have an integral square root. Such numbers are 1, 4, 9, 16, 25, etc. ... the combined impedance is that of a single unit."

The idea of a 9-unit array also cropped up in some of his sales literature in the 90s but there isn't any indication of whether it was necessary to tailor the response in any way. I did hear a 9-unit array when Jordan Watts used his J51 units at a hi-fi show in aorund 1991. I thought it sounded pretty good. Certainly went loud.