Jordan jx92s Bipolar design -

[Johnvn]

As I am very new to DIY audio in every way, my background many years ago was in the development of ultrasound machinery, but now I have been seduced by the idea of building my own speakers, I am asking anyone for help. I have access to CNC machining and all types of timbers. I have recently purchased 4 Jordan jx92s drivers and would like to mount them in a bipolar configuration based on a bass reflex style box. Any help would be appreciated, and if successful I will post full plans for anyone to use.😕

 

[johngalt47]

Maybe this will help

This is not exactly what you are asking for but maybe you can get some ideas:

http://homepage.mac.com/tlinespeakers/FAL/downloads/BipolarMLTLDesignPak.pdf

Here is another design using only one driver per enclosure:

Jordan JX92S DIY Tower Loudspeakers

 

[Jim Griffin]

I've dealt with bipolar designs in MLTLs. I like MLTLs as they account for the placement of the driver and port such that optimal bass response is realized. I use the Martin J. King spread sheets to design the MLTL enclosures.

You have a link for one of my bipolar designs and another bipolar approach is my offset variant.

http://www.diyaudio.com/forums/full-range/148939-offset-bipolar-mltl-css-el70-drivers-part-1-a.html

I also have a long history with the Jordan JX92S in mini-monitor and MLTL designs. I've included a link to my Jordan with a ribbon MLTL which has been widely replicated with success. My other Jordan designs are also reported in diyaudio postings.

http://www.diyaudio.com/forums/full-range/81634-jordan-ribbon-mltl.html

Let me hear if you need guidance.

Jim

 

[Johnvn]

Interested in Griffin Bipolar designs

Firstly, thankyou for your replies to my post regarding Bipolar designs. In particular I am interested in Jim's designs, I would like to replace the ports with passive radiators and would like your opinion on the effect of bass response as well as recommended types of passive radiator.
As well, would I need to increase the amount of stuffing if I use passive radiators.

 

[GM]

Hmm, finding a PR with suitable specs may be problematic since it will need to be very light with an incredibly large Vas by PR standards. There use to be junk cardboard diaphragm/foam surround PRs with suitable specs back before the DIYer's 'age of enlightenment' was ushered in by the inventor Tom Danley, but some Googling didn't return any places that still sells them.

No, same or less IME.

GM

 

[Colin]

Why would you want to use passive radiators? I don't think any of either Jim's or Ted Jordan's designs would be suitable.

The bipolar bit is already introducing one variable. Don't add any more or you'll wander so far off tried and tested territory it will be difficult to evaluate what you end up with.

The MLTL is an excellent enclosure design. If bothered about using a port, then stick to GM's shorter 31" design which will reduce the risk of too much bass in some locations.

 

[GM]

I don't think any of either Jim's or Ted Jordan's designs would be suitable.

Well, they certainly aren't the type of alignments best suited to PRs, but I wouldn't go so far as to say that they aren't suitable. The 31" MLTL OTOH would be best served with a PR, but again, finding one with good enough specs is problematic.

The main reason for using a PR is to eliminate vent compression and its associated pipe harmonics. Simple MLTLs help by mass loading the vent, but ML-horns (aka ML-TQWT by some) load them much more, so the elegant solution is to redesign the 31" to shorten its vent. IIRC, JG's MLTL designs already have a short vent, so either adding a PR or converting them to a ML-horn will only equate in reducing the amount of stuffing required, a worthwhile goal IME, though some others disagree.

GM

 

[Jim Griffin]

I too would question the use of a passive radiator in a bipolar MLTL design. The dominant factor is that Martin King's software used for my design (and many others) does not allow for a PR even if you had an ideal solution. A port will work just fine and as others have said there are a multitude of MLTL designs for the Jordan including the 31 and 48 inch variants. Thus you can vary the length of the MLTL to suit your needs. Just a few runs through Martin's software to optimize.

 

[Colin]

Well, they certainly aren't the type of alignments best suited to PRs, but I wouldn't go so far as to say that they aren't suitable.
GM

Ah, I'm overstepping the bounds of my technical knowledge then (as usual).

Thanks for the extra info - an education, as always.

 

[norman bates]

full ranges and passive radiators ?

To me, the radiatior will want to keep moving, that then moves the air that the pushes against the cone that does voice (when it shouldn't be).

Perhaps it sounds the same as a port, I'd have to experiment to give a true opinion.

Passive radiator (to me) is more about tuning really low in a smaller box when a port that is large enough to deal with the mach air thing. Think of a dual 15s in 3ft3 that has 12db of boost at 25hz (just to measure flat). A port would be too long.

Norman

 

[GM]

It sounds better than a port with 'better' meaning more accurate due to the lack of vent harmonics comb filtering with the driver's mids. Again though, the PR has to have the right specs to damp, rather than modulate, the driver. For the typically small FR drivers discussed here, 'pancaking' a pair of the 'junk' rectangular foam surround cardboard units that PE and others used to sell worked well enough. By themselves though, they had a tendency to wobble and quickly rip the super flimsy surround.

I couldn't even find a picture of one in a quick search. A pity really now that we have drivers with Vas specs suitable for them, they're apparently extinct. Oh well, maybe a marketing opportunity for one of the driver manufacturers.

GM

 

[GM]

Thanks for the extra info -

You're welcome!