Pentaline project : JX92 based pentagonal TLine - diyAudio
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Old 24th November 2002, 07:38 AM   #1
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Lightbulb Pentaline project : JX92 based pentagonal TLine

Have a look at this new project :

I wanted to create a JX92S TLine like the ones of Carolina Audio or Konus Essence (Jordan cabinet design), but with some improvements :
- Wall mounted to get a deeper bass
- At the same time having the speaker axis crossing in front of the listener ( important with JX92S )


For this reason the cabinet is a pentagon, the 3 parts of the TL are organised like a L.
My drawings are available on request ( graphics interchange format, designed with TurboCad freely downloadable from imsi, can be read with TurboCad or any CAD software). Volumes are equivalent to the Jordan Tline with a 30° angle between speaker axis and wall.
The Tline stays unstuffed, and the upper chamber is almost unstuffed (a few grams of Dacron in the corner).

First impressions after 50 hours ( JX92S are really OK after 100 hours, and the first 20 aren't very good ) :

They really soud GREAT. I think that due to the asymetric shape of the upper chamber, there is almost no need for any dampening, and there isn't any behind the speaker (no parallel walls).

The first time I listen to them, I had to check that my active sub was off... and it was. The bass guitar is deep and razor sharp at the same time : unbelievable for such a small speaker ! Now I can resell my sub...

The voices are vibrant, the stage is in front of me ! I don't regret the extra work of "folding" the Tline to create a pentagonal speaker : having the axis crossing in front of the listener makes a real difference, and the speaker being against the wall (no yet wall mounted on the picture, but there designed for that, there isn't any stand) reinforces the bass.

At the same time all instruments (inc. voices) are clear and distinctly placed on the stage : now I have to build a high end amplifier to use all of their potential...

The picture shows the speaker before front panel fixing.

Regs
François
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Old 24th November 2002, 08:26 AM   #2
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Default Re: Pentaline project : JX92 based pentagonal TLine

Those look nice. Without damping thou, you are going to have a lot of ripple in the bass and lower midrange -- they don't care that your cabinet is a pentagon.

dave
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Old 24th November 2002, 09:53 AM   #3
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In fact not so much, and it's surprising. Just a little dampening in the upper corner. There isn't any dampening in the Jordan orginal design (except behind the speaker). I think the volumes of the TLine were calculated for no dampening.

I had first put some dacron, but I prefer the sound without anything (almost anything, just a little bit for the psycho-acoustic effect).

What's really surprising is the clear bass : contrebass, electric bass, drums : all very clear, and at the right level. The sub isn't required at all.

They currently are at the garage ( ! ) for painting. When they come back I'll try some other dampening configurations.

François
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Old 4th December 2002, 05:52 PM   #4
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Finished !


I've added some dacron in the upper chamber, but mostly on the side walls.


There is maybe a little renonance something around 400Hz : it only appends on some CDs. Don't know if it comes from the upper chamber or the line itself. Anyway they sound great ( a "concert-like" sound), incredibly detailled with a very precise placement of the instruments on the stage.

François
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Old 4th December 2002, 09:51 PM   #5
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I have been using the 92S in TL enclosures for about nine months and I agree with Dave on the stuffing issue. I have built three prototype TL boxes so far using the 92S and found that they sound surprisingly good unstuffed, but much better properly stuffed. I have also found that the driver performs better if the reflections from the back of the diaphragm are kept away from the driver (something that your upper chamber probably does pretty well). I have tried distance, geometry and elastomeric material like Deflex to get rid of the parasitic reflections. Distance seems to be the best method.

Wall mounting is a good solution and one I tried as well. Your cabinets are quite nice looking, but I wonder why you didn’t make the baffle panel flush with the wall surface? An interesting experiment would be to add a small panel in this space or cut a piece of foam to fit the void and listen to it. My guess is that it may sound a little smoother and more coherent.

The first prototype box I constructed, while not much like yours in appearance, was designed with wall mounting in mind. It had a 3 segment, hinged baffle that when opened all the way was 1.2m (4 feet) square, which did allow me to place them against the walls, as well as angle the “wings” to any configuration in the room. By folding one “wing” back and joining center panel the driver was mounted in to the wall surface and extending the opposing “wing” into the room, I actually approximated what you have done. Against the wall and angled in sounded very good, but my room is too wide to really take advantage of this configuration. All in all the folding baffle experimentation was very educational.

Subsequently, I have constructed a narrow face rectangular enclosure and a convex face cylindrical enclosure. Both sounded more open, but a little “edgier” than the wider box. The cylindrical enclosure seems to go deeper and is a little smoother. Neither one is an aesthetic masterpiece. However, the results from all three enclosures using the Jordan drivers were successful enough to provide the motivation build yet another enclosure. My final 92S prototype has been designed using Martin King’s excellent MathCAD worksheets (I can’t say enough good things about them or Martin for that matter), as a push-push ML_TQWT. The simulations look promising with good output to about 35Hz and a reasonable box size.

Now, if they work as well as the worksheets indicate and I can finish them as well as you did, I will be very happy.
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Old 5th December 2002, 12:00 AM   #6
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Quote:
Originally posted by dana
a push-push ML_TQWT
That i am VERY interested in seeing.

BTW i am always looking for new projects for the TL web-site (can't promise getting them up right away -- i have a bit of a lack of time)

dave
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Old 5th December 2002, 12:25 AM   #7
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I'm interested in the push pull project too ... I'd love to use these for our family room (not the HT room). I mean, right now I'm using the TV speakers

I want to try a single driver next (I'm finishing up my Thor's) so truth be told I'm interested in ALL of these projects
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Old 5th December 2002, 07:08 PM   #8
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Quote:
Originally posted by planet10


That i am VERY interested in seeing.

BTW i am always looking for new projects for the TL web-site (can't promise getting them up right away -- i have a bit of a lack of time)

dave
Thanks for the interest. And actually thanks to you for posting the TLb project on your site, which gave me the inspiration.

I have most of the design work completed on the push-push project, but haven’t started cutting wood yet. As it turns out, it was a lot easier using Martin's software than I initially thought. The worksheets gave me an easy way to try a bunch of different taper rates and line lengths. Once I have enough completed, I will post it.
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Old 6th December 2002, 12:09 AM   #9
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Does anyone have a good ordering link for the Jordans? I can't seem to find one.
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Old 6th December 2002, 12:19 AM   #10
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Try Creative Sound if you are looking at the 92S.

http://www.creativesound.ca

If you need access to the full line, you can order them directly from Jordan. Send them an email and they will give you a quote very quickly.

http://www.ejjordan.co.uk
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