Jim Griffin's JX92S designs

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#81
here is the pic and specs 🙂

Sensitivity 90dB/1M/2V
Power handling 12W nominal, 25W max
Frequency range 2,000-40,000Hz
Nominal impedance 5 ohm
DCR 0.02 ohm
Ribbon dimension 8mmX38mmX0.015mm
Effective ribbon area 304 square millimeter
Ribbon weight 10 milligram
Gap flux 0.50 Telsa average
Gap height 10 millimeter
Recommend cut frequency 3,500Hz with -18dB
Net. Weight 410 gram
 

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#82
WCT and Henry raised a few questions on the 'Jordan with a Ribbon' mini-monitor and MLTL designs.

1. Port Tube. The port tube that I use that for the mini-monitor is the Parts Express #260-388 which is 1.375" inside diameter and 4.3125" long (I'm using it without the sliding adjustable section). For the MLTL the port tube is the P-E #260-322 which is 2.0625" inside diameter and cut to 3.0" long.

2. Crossover Network Location. I locate the crossovers inside the enclosures and the sketch that I show in the design package works for me. I use 3/8" thick x 3.5" wide hobby board cut to length. The crossover is located in the bottom of the mini-monitor and is screwed down inside the box. As I use a 4 post terminal plate (Madisound TD Cup), I have access to place and screw the network to the inside of the front wall of the MLTL.

3. MLTL Dimensions. While I built my prototype a little short (46.5") of GM's 48" internal dimension, you can use his 48" length if you wish. I use 0.75" thick material for my box so the total outside length becomes 49.5". The width of the box externally needs to be 7.5" (important to allow the same crossover circuit with integral baffle step correction for the mini-monitor to be used in the MLTL). The external depth of the enclosure is 6.375".

4. Stuffing. For the mini-monitor I use the P-E #260-516 convoluted foam material to line the rear, top, and side walls of the box with a cutout for the port tube. For the MLTL I fill the volume from an inch below the cutout for the JX92S to the top of the box with teased Acousta Stuf material (P-E #260-317). In my MLTL box I located a windowed brace just below the JX92S cutout so that I can use a wire grid to prevent the stuffing from falling into the lower volume of the enclosure. No stuffing is located below the brace.

5. Design Package. The mini-monitor design package is located at:

http://www.esnips.com/doc/0cd36443-0972-477d-9e54-1267c790b359/JX92SG2siDesignPak


If you need more info on the MLTL version, you can send me e-mail at 'jiffin at cookeville dot com' with the appropriate alterations.

6. Different Tweeter. I have not used the Fountek Neo CD 1.0 tweeter so I can not certify that it will work as well as the Aurum Cantus G2si. A few folks have used the Fountek Neo CD 3.0 and report good results but again I do not have first hand experience. I suspect that you may have to change the series resistor in the tweeter loop of the crossover network to adjust for sensitivity differences between the Fountek and A-C tweeters.

Jim
 
#83
thanks jim, i know this jx92s is superb driver, and your design really inspiring and answers the need for a high quality and simple speakers.

today just reviewed an old kef reference 101 bookshelf, its good sounding, but really outclassed by the jordan's deep, excellent imaging and solid sound 🙂

i have one more question though, in your opinion jim, which one u prefer? ml-tl or the original?

thanks
cheers
 
#85
Jordan Minimonitors

bluegti said:
I just built a set of the mini-monitors using the .25 cu. ft. cabinet from Parts Express. The finish on the cabinets is very nice and the cost is less than the materials and my time is worth.

They had their public debut at a local audio meet last week. Everyone was very very complimentary. Several people ranked them among the best monitors they have ever heard.

I just drilled the back of the cabinet for the port. Come to think of it, the cabinet is only 3/4 inch thick, I probably need to add a few straws to the port to make it 1 inch. Even so, they have very good bass for their size.

I lined the back and sides with 1 inch foam from parts express. No other stuffing. I think they sound good and as I said, so did the rest of the listeners.

My crossovers are currently external so I can continue to tweak them. The layout I used is different from Jim's. I couldn't figure out how to connect all the wires cleanly looking at his layout. The nice thing is that since they are on two smaller boards, there is lots of options when I choose to put them inside the cabinet.
Click to expand...

I heard these speakers at the meet and can attest to their performance. They are terrific sounding for their size, i was truly suprised. I`d love to hear a pair of the mltls.
Steve.
 
#86
A couple of comments on which one to build--the mini-monitors or the MLTL? I'll confess that my daily listener is the MLTL. It is a more complete sound to me with enough bass for most everything. The difference in the F3 point (3 dB down on the low frequency end) is about 15-20 Hz as the mini-montior can do do 55 Hz while the MLTL goes below 40 Hz. You would be surprised just how much more impact the MLTLs have. The imaging and soundstage sounds the same to me between the two designs so the bass impact is the icing on the cake.

Also the MLTLs have a smaller cross-sectional foot print than the minimonitors. They look very slim and neat in my biased opinion. Thus, if you have to use a stand with the monitors, then the MLTL offer built-in 'legs'.

Of course the MLTLs stand tall (just over 4 feet) so that perhaps will discourage a few folks.

Jim
 
#88
Hi Jim

I was going to ask you which design you prefer, but did not want to overdo it with all the questions. Glad you stated it, and afterall, you have heard both.

With regards to the MLTL build, I read all of what you have written in other threads. But one question, how many window braces do you use in the MLTL cabinet? And what is a window brace? Sounds like a horizontal plate whose dimensions are are equal to the inside dimensions of the cabinet. In this plate is a very large circular opening so as not to affect the cabinets tuning. Is that it?

thanks again

Curt
 
#89
Curt (WCT) asked:

"With regards to the MLTL build, I read all of what you have written in other threads. But one question, how many window braces do you use in the MLTL cabinet? And what is a window brace? Sounds like a horizontal plate whose dimensions are are equal to the inside dimensions of the cabinet. In this plate is a very large circular opening so as not to affect the cabinets tuning. Is that it?"

Yes, you are correct. The brace that I use is 4.875" x 6.0" with a 4.125" diameter hole in it. I'm using just one for the cabinet.

Jim
 
#91
I am about to start building a 31' GM mlt with a 7.5' baffle in order to be able to add the G2si using Jim Griffin's xover/bsc network and have a question.

Is there any implication if I place the G2si as far up as possible rather than next to the JX92s?

Thanks

Antonio
 
#92
A Sanchez said:
I am about to start building a 31' GM mlt with a 7.5' baffle in order to be able to add the G2si using Jim Griffin's xover/bsc network and have a question.

Is there any implication if I place the G2si as far up as possible rather than next to the JX92s?

Thanks

Antonio
Click to expand...

As a general rule,the tweeter should be as close to the mid as possible(jx92s in this case).Unless you are listening the speakers from very far distance.
 
#93
Antonio,

You really need to place the tweeter next to the Jordan driver as the crossover was derived with that specific placement. If you move the tweeter upward as you suggest, then you mess-up the crossover coherence.

As you likely realize, the tweeter needs to be centered at ear level for the listener. That usually becomes about 0.9 meter high for a seated listener. Now if your 31" MLTL places the tweeter too low, then you can add a false bottom to the box when you construct it. Another option is to use a short stand to raise the enclosure to the correct height.

Good luck with your project.

Jim
 
#94
Many thanks for your comments.

Jim,

Due to space constrains the height of the structure will be around 41' in total including the false bottom. This would leave the center of the Jordan at about 28' and the Ribbon next to it at about 33'. Since this is still a bit low, I was thinking about putting a bit of a slope at the base so that the waves project up few degrees to compensate. I do not know if this is counterproductive with MLTL designs.

In relation to the false bottom itself, I am considering something similar to the one shown in the Jordan's web site but with the opening window to the back instead of the front, or with two windows, to the front and the back ( I wonder if this could have an impact, good or bad).

On a separate topic. I was thinking to see if a 40' GM MLTL in a rectangular shape would allow the port at the front or the back instead of the bottom. If this was possible I suppose I could end up with a bit more hertz in the Lf (maybe around 40hz?). The problem is that I do not yet have the knowledge or the tools to calculate this.

I know the triangle allows this but it has a very low WAF in my case.


Best regards

Antonio
 
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