| Smokeyone |
Hello
I am planning to build the jordan mltl 48 design based on the triangle cross section usuing the jx92s. Has anyone any thoughts on this.
Have already found this link
http://diyaudioprojects.com/Speaker...r-ONE/index.htm
but would welcome other ideas please. Can I get away with usuing 12mm mdf which I just happen to have but was thinking of making the three corners out of solid wood and rounding them off like a 60 degree semi circle....
Thanks |
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| pikkujöpö |
Hi
How about using the search on this forum;)
I bet you will find plenty of information about mltl48 and many other JX92s systems.
If you clue two 12mm MDF boards together it will be strong enough.Only one 12mm is too thin even with braces.Many have recomended the baltic birch plywood for the construction.It should sound better,so consider this option. |
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| Smokeyone |
Thanks for the advice. I did try search but could not find the triangle shaped version.
Will take your advice about glueing two lots of 12mm mdf together or perhaps 12mm mdf with 12mm plywood birch on top.
Do you think the internal diamentions are critical...If the speaker cabinet was slightly larger would that improve the sound or leave well enough alone....
Thanks |
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| Colin |
Hm - interesting site, though the author claims rather a lot for his contribution to the design. The design is the same as the MLTL on the Jordan site, designed by GM. But good to see someone talking about the specifics of building. Note though that he's wrong about some aspects, notably toe-in. The JX92 is designed to toe-in at 30 degrees to get the sound balance and imaging correct.
There are several threads about the triangular version on here. I've contributed to several, having already built the triangular MLTL. Mine used a sandwich of half inch ply and insulation board, which makes quite a light, stiff enclosure. However I'm not convinced it's any better than using three quarter inch ply alone, which is what I'll try next time. I used edge strips to hold the main panels together, resulting in a six-sided external shape. This seemed the easiest way to go when I don't have a proper workbench.
Given the time and labour involved, I'd recommend starting with birch ply of the right thickness rather than messing around laminating 12mm mdf panels together.
The triangular shape does help reduce resonances. I've since built another JX92 enclosure which has a square cross-section and by comparison it sounds shouty on spoken word. Not so noticable on music. Although the design is different, I suspect the majority of the colouration is down to the reflections coming off the back and side walls. |
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| Colin |
| As a PS, I can confirm the Tobler author's impressions about corner placement for this design. They sound more balanced away from corners. If corner placement is your only option, go for the 31" MLTL (also on the Jordan site). GM designed this to have a flatter, more accurate bass response. |
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| Colin |
| Here you go - this is the thread which kicked it all off. Bruce built most of the available JX92 enclosures and gives his impressions. |
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| Smokeyone |
| Thanks for the advice and where to find the thread. |
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| Nardis |
I rejected the triangular version becauseof its wide panels, and instead I built a pentagonal version with the same cross sectional area as the original, using 18mm MDF.
Internal angles are 2 x 110 degrees, 2 x 90 and 1 x 140.
Internal dimensions are baffle 130mm, sides 101.5mm, rear 106.20mm
External will depend on the thickness of the material.
The advantages of this shape are:
- no parallel sides to reflect rear waves
- narrow panels resonate less
- very narrow baffle (156mm) improves imaging (yes I know not everyone agrees about the JX92 on narrow baffles). It is very close to one of the shapes that Martin Colloms tests out in "High Performance Loudpseakers" with good diffraction results
- elegant looks
Disadvantages are:
- you have to work out the external and internal dimensions of the panels. These vary with the thickness of the material used. (I ended up doing an Excel spreadsheet to cope with this.)
- you need to cut the angled pieces exactly so you need access to a good table saw. (In fact you only have to cut at either the normal 90 degrees or at 20 degrees off the vertical and a with a careful cutting plan you need only a smal number of angled cuts)
- it's tricky to assemble
I adapted Jim Griffin's crossover (I use a Fountek JP3 Ribbon and they are close to the wall) and I am delighted with the sound.
GM's original design and Jim's integration of the ribbon have produced a knockoput speaker. |
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| Colin |
Regarding the narrow baffle, I find putting the triangular units back against the walls compensates for th lack of baffle step. If you use your enclosures out in the room, try placing a piece of card or board alongside to hear what it does to the sound. It does seem to make it fuller. I believe there is a link on the site I mentioned above where someone has measured the effect.
Anyway, glad to hear you're happy with the speakers. Sounds like a very elegant design - have you posted a pic of the finsihed enclosure? |
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| smallangryboy |
| Can the port be fitted to the rear of the MLTL 48 out of interest ? |
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| pikkujöpö |
| quote: | Originally posted by smallangryboy
Can the port be fitted to the rear of the MLTL 48 out of interest ? |
Yes,if placed near the wall corner ,the bass will have more corner loading this way. |
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| smallangryboy |
| Many thanks, that's just the ticket :) |
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| Colin |
Last year GM posted somewhere here that if placed in a corner the port could be replaced wih a hole at the back and corner placement used to load the bass. I didn't keep a record of it, unfortunately.
When I redo my MLTL triangles, to make them a less rough-hewn looking, I'll commission someone with woodworking skills and workshop. The pentangle sounds elegant but I like the way the triangles can go flush against a back wall and appear as a planned part of the room.
I was able to take one of my samples to Ted Jordan last summer so he could measure them. He commented that the triangular shape did a good job of suppressing resonances.
Ted experimented with a BSC circuit for the triangle and came up with R = 4.7, L = 3.2mH. Comparison plot attached. The red line is with compensation in place. It substantially cleaned up a thinness to the sound which I had previously attributed to the driver.
BTW, the dip at 150Hz showed up on another design so may be a room effect. Due to pressure of time so we didn't try averaging from a number of measurement positions. |
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| smallangryboy |
I'm getting hold of Solidworks so that I can work my designs up into CAD friendly ones, time willing I can help out anyone else.
Hopefully I should have a contact to CNC any designs, this may be of interest to you Colin ? |
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| Colin |
| Yes, I'd certainly be interested in getting a price for it, especially if we're both planning to do the same enclosure design. |
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| smallangryboy |
Just had a closer look at the dimensions of the 48, stupid boy for looking at the image on the Jordan website and not the actual numbers.
The form factor makes it very skinny and very tall, unfortunately impractical for my environment and my tearaway young daughter, I'm looking for something with more conventional dimensions, like 170mm x 200mm x 900mm or along those lines, looks like this may be a deal breaker. |
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| Colin |
It may be possible to fold the MLTL, to give a more conventional shape. Alternatively, the 31 inch MLTL may be a better bet, arranged so that it has a sloping front and can stand directly on the floor.
Due to dogs and clumsy owners (that would be me), my next triangle will be bolted to the floor, rather than spiked.
A more conventionally-shaped TQWT is shown here. |
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| smallangryboy |
lol
My previous Jordan design is based on the TIDY TL so I wanted something that would be a step up from that sonically, which is why the rave reviews about the 48 piqued my interest.
Do you think this more traditional design would be on a similar footing to the 48 [no pun intended :)] ? |
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| Colin |
| Not sure. One poster commented that it had a bass resonance he didn't like, but that may have been room related. Not having heard it, I'd go for the VTL or a folded version of the 48. The VTL doesn't go as deep but sounds nice and is an elegant shape. You could mount it direct on the floor - rather than use the small stand shown on the Jordan site - and have the line exiting at the side. |
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| Jim Griffin |
| Those of you who are concerned about the stability of the Jordan MLTL could do as I have on my Jordan with a ribbon MLTL design. I use a base to wide the stance so that the floor contact is spread out. My base is Corain--a man made stone like material which can be machined. Other ways to add stability is to add weight to the bottom of the enclosure, use spikes to bite into carpets, etc. Several ways to achieve stability for your MLTL. Stability is a problem that can easily be solved. This should not be a reason to select another design. |
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| planet10 |
| quote: | Originally posted by Jim Griffin
Those of you who are concerned about the stability of the Jordan MLTL could do as I have on my Jordan with a ribbon MLTL design. I use a base to wide the stance so that the floor contact is spread out. My base is Corain--a man made stone like material which can be machined. Other ways to add stability is to add weight to the bottom of the enclosure, use spikes to bite into carpets, etc. Several ways to achieve stability for your MLTL. Stability is a problem that can easily be solved. This should not be a reason to select another design. |
Also, one could add a fixture so that they could be screwed into the wall at the top. (as i understand it, these like to be up against the wall -- if not i'll let you know once ours are built)
dave |
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| abpea |
| quote: | Originally posted by Jim Griffin
Those of you who are concerned about the stability of the Jordan MLTL could do as I have on my Jordan with a ribbon MLTL design. I use a base to wide the stance so that the floor contact is spread out. My base is Corain--a man made stone like material which can be machined. Other ways to add stability is to add weight to the bottom of the enclosure, use spikes to bite into carpets, etc. Several ways to achieve stability for your MLTL. Stability is a problem that can easily be solved. This should not be a reason to select another design. |
I agree, stability for this cabinet is a simple problem to solve. For my 48er I found a nice full 2 1/2" thick plank that I cut into lengths, put a fancy routed edge on them, painted them black and added spikes for the carpet. Bolted them to the bottom of the 48er column and it is solid as a rock, or Corian, etc. :)
You will have one problem with these speakers... people will keep trying to take them, or get you to build them a pair. They're great, build a pair you'll be glad you did!!
Bruce |
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| smallangryboy |
| Many thanks for the replies, do you have a link to the folded design of the 48 as a search has come up blank. |
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| Colin |
I don't think there is a folded 48 design - this was just an off-the-cuff idea. I agree, the stability is a problem to be solved, hence bolting to wooden floors in my case.
PS to Planet 10 ... I know what you're like for modifications. I am definitely waiting until you've reported on your build before commissioning mine. |
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| smallangryboy |
| quote: | Originally posted by Colin
I don't think there is a folded 48 design - this was just an off-the-cuff idea. |
I'd be interested in exploring this design ! |
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| GM |
Why? Then it's so short you need a tall stand to get the driver up to ear height. That, or a tall, deep bookshelf.
GM |
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| Colin |
Yes, the 48 started out specifically to get the driver to ear height without needing a stand. Maybe one of the compact horns (hifisound.de) would be a better bet if you want a short, rectangular enclosure?
The 48 does look very elegant when placed back against a wall, especially in triangle format. (I haven't seen a pic of the pentangle.) |
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| Nardis |
| quote: | | The 48 does look very elegant when placed back against a wall, especially in triangle format. (I haven't seen a pic of the pentangle.) |
It's a pentagon, not a folk-rock band! Shown here before its top was bolted down.
I wish now I had put the port at the rear. Its sound never ceases to amaze me as I go through source and amplifier upgrades. Thanks to GM for the original design and Jim for the xover starting point. |
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| planet10 |
| quote: | Originally posted by Colin
PS to Planet 10 ... I know what you're like for modifications. I am definitely waiting until you've reported on your build before commissioning mine. |
I probably won't be able to resist, but for the short term the idea behind the JX92s is to see how badly they get spanked by the FE127eN :) (i'll be happy to be surprised thou)
With Ron really starting to make progress on actually figuring out the physics of EnABL and Soong so up on the JX92, i'll probably just let them work out the treatment for the 92.
Also with the bifurcation of Jordan with Ted funding his retirement, i'm going to sit back a bit and see how things shake out before seeing were they fit with the business ends of things (i do have a set of the "rogue" 50 mm headed this way to play with :) Hopefully new blood & competition will spur the products forward so that they become better & more affordable (that last probably just tied in with getting the volumes up)
dave |
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| Colin |
| folk band or military industrial complex, they still look nice speakers. |
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| Nardis |
| quote: | Originally posted by Colin
folk band or military industrial complex, they still look nice speakers. |
Thanks Colin
I have been racking my brains for a name but neither "The Pentagons" or "The Military Industrial Complexes" sit comfortably.
They remain "Pentagonal Versions of GM's 48"MLTL (with a ribbon added)". I did think of calling them "GM's Wonders" but decided it sounded too like a variety of potato.
I haven't managed to hear either standard or triangular versions of the design. although I have heard a number of DIY JX92 projects. Where these theoretically have an advantage is narrow baffle (155mm), narrow panels for less resonance and no parallel reflective surfaces. Is there anyone in the London area with the rectangular or triangular designs who would like to do a comparison?
The cabinets were inspired by the Pentachord, a very slim, tall design using little Bandor drivers, that I heard at a HiFi show at Heathrow, London many years ago. I designed a pentagonal shape with the same CSA as GM's MLTL. Cutting isn't as tricky as it looks if you have a table saw. All the cuts are either 90 degrees or 20 degrees. Clamping for assembly is the difficult bit. |
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| Colin |
I remember the Pentachord - that had Bandor drivers and sounded good. I attended one of the shows in the 90s which had several Bandor systems on demo. The Pentachord was the simplest and, IMO, the nicest sounding.
Yours look quite B&O. Perhaps they should be called the high five ...
Elsewhere on the forum there has been a thread about steel enclosures. This shape would look good in metal, if anyone was brave enough to try.
Do you use the standard BSC circuit which is part of Jim's crossover or have you altered it to compensate for the narrower baffle? |
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| Nardis |
| quote: | Elsewhere on the forum there has been a thread about steel enclosures. This shape would look good in metal, if anyone was brave enough to try.
Do you use the standard BSC circuit which is part of Jim's crossover or have you altered it to compensate for the narrower baffle? |
I did hear some JX92s in a sealed 25 or so litre curved cabinet made of 2 layers of aluminium with an injected polyurethane foam filling and a plywood baffle. They were superb.
Metal doesn't appeal aesthetically to me, but I am in the process if costing out Corian and its more acoustically inert variants. If I can find somone who gives me a reasonable quote I will let people know. A good proportion of the expense is apparentlly in programming the CNC cutter used, so the unit price drops and the more takers the cheaper they become It may even be possible to give the cutters a CAD file if we can do it in the right format.
As for the xover, I used Jim's as a basis, took out what I thought were the BSC elements and then basically tuned it by ear until it sounded right for the position in my room. I had used an online BSC calculator to help, but I can't remember the link at the moment. |
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| Nardis |
I remembered the BSC calculator I used. It's on Martin King's Quarter Wave site and is an Excel sheet by Hong Nguyen.
http://www.quarter-wave.com/General/BSC_Calculator.xls
I used this to work out roughly the BSC element in Jim's xover given his baffle size, deducted it from the xover values, recalculated it for the narrower baffle and used the table of results to start with a very small correction given I was very close to a rear brick wall. In the event I decided that I needed very little BSC, as it came to a fine balance point between a fuller-bodied sound and bass boom due to room modes. At this point I settled on the slightly lighter bass.
Since then I've been involved in amplifier issues and when they are sorted out, I will retune the xovers. if they need it. I've been looking at doing this with a passive line level filter based on
http://sound.westhost.com/bafflestep.htm
which should give me finer control with neglible losses. Has anyone used this?
I have to be careful of losses as I am running the MLTLs from a chinese 300B SE 9W per channel amp (bought on Ebay by getting up at 4am to slam in a last-second bid). It sounds superb but I can't afford to lose more headroom on the xovers. |
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| GM |
| With a 300B and near wall location, I'm surprised you need more than a Lpad on the tweeter. |
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| Nardis |
| quote: | Originally posted by GM
With a 300B and near wall location, I'm surprised you need more than a Lpad on the tweeter. |
Yes. You may well be right.
Oddly enough I just encountered a piece in the UK magazine HiFi World Feb 2008 issue suggesting using the Fountek JP3 ribbon (which I use) as a super-tweeter with a full range design they have published., and other full range drivers or designs with tweeters rolling off just above 20k..
They have a circuit which boils down to a cap in series used as a 1st order high pass filter and a variable L-pad.
I think I have the appropriate values, and it’s a wet weekend…… |
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| Nardis |
| quote: | Originally posted by Nardis
Yes. You may well be right.
Oddly enough I just encountered a piece in the UK magazine HiFi World Feb 2008 issue suggesting using the Fountek JP3 ribbon (which I use) as a super-tweeter with a full range design they have published., and other full range drivers or designs with tweeters rolling off just above 20k..
They have a circuit which boils down to a cap in series used as a 1st order high pass filter and a variable L-pad.
I think I have the appropriate values, and it’s a wet weekend…… |
Well, the wet weather continued and I tried running the MLTL full range with the Fountek rolled in above 12k and also above 16k. The amount of detail improved, but this was not entirely surprising given that the signal was not going through 50 feet of copper inductor. The top end was hard verging on harsh.
When I switched back to Jim's design the whole presentation improved, and it became smoother and much better integrated. I definitely preferred the music using the 3k xover based on Jim Griffin's design . |
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| t-head |
http://www.carolinaaudio.com. I have the JLM. 6.5"x5.75"x36" with larger base attached. Rear rectangular port, 3x folded line. Mine are painted white, 1/2" MDF. Single JX92S running wide-range. 40hz up in room. You brilliant folks here should be able to duplicate them. Sit nicely at front wall 15' apart, 10 deg. toe-in. Room 16'x16'. Driver 2" below ear level when seated. Very nice...;)
t |
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| Jim Griffin |
t-head,
The 48" MLTL with the JX92S has a 37 Hz 3 dB down low end without considering any room gain. This variant will edge out Ronnie's design for bass impact and you can DIY the cabinet. You get DIY satisfaction while saving hundreds of dollars. What is not to love about that?
My version of this 'Jordan with a Ribbon MLTL' design (actual about 46.5" long) adds the superb Aurum Cantus G2si ribbons which are excellent above 3000 Hz. Just ask Nardis a couple of messages before this one how he likes his version (albeit with a similar Fountek ribbon).
Jim |
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| t-head |
Hi Jim,
I bought from Ronnie before I ever discovered DIY. I have heard good things about your designs and certainly meant no disrespect. I have another pair of JX92Ss coming thru the group buy...when they arrive I'll be in touch...;) But all that notwithstanding, Ronnie makes a great pair of $1250 speakers for the hopelessly non-diy types...
t |
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| Colin |
| quote: | Originally posted by smallangryboy
I'd be interested in exploring this design ! |
Okay, I'll bite.
Here's my take on how a folded MLTL48 might look. It would give an enclosure 7.5" wide, 12.25" deep and 25.5" high. You'd have to incorporate a stand or extend the enclosure (with a sand-filled cavity), height to suit. The horizontal divide would be 2" thick, all the rest 0.75" material.
A bit deep and not as elegant as the original but it gets close to your size requirement. I have no idea how the loading would change with the folds but at least it would be a stable box! |
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| planet10 |
| quote: | Originally posted by Colin
Okay, I'll bite.
Here's my take on how a folded MLTL48 might look. It would give an enclosure 7.5" wide, 12.25" deep and 25.5" high. You'd have to incorporate a stand or extend the enclosure (with a sand-filled cavity), height to suit. The horizontal divide would be 2" thick, all the rest 0.75" material.
A bit deep and not as elegant as the original but it gets close to your size requirement. I have no idea how the loading would change with the folds but at least it would be a stable box! |
Excellent. I can see variations where you would run the bottom part down further to avoid stands and leave the void in the middle of the back. From a potential resonance POV, the 2 11.5" pipe sections may be a problem.
dave |
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| Colin |
| Hi Dave - thanks for the comment. Yes, I wondered about the void in the back but left it off for simplicity. If open to the back, the void could incorporate a reflector to 'load' the port in the same way as GM's original 31MLTL. The height of the void would also allow some flexibility to vary one of the two 11.5" line lengths so they were dissimilar. |
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| A Sanchez |
Hi everyone, a new member here with a quick question.
I believe I have read everything that has been written on the internet about GM's MLTL's 31 and 48 designs (and their variations) and there is something that is still not clear for me.
As a matter of fact the 31' version becomes at least a 44' tower when the extension is added, making it in practice very similar to the 48' in terms of height.
So, since the 48' reaches 35Hz vs 45Hs with the 31' and the 48 seems easier to build, what is the advantage of building the 31' version?
Do they have a different sonic character altogether? Are they suitable for different rooms, purposes , tastes, etc??
I am about to receive a pair of JX92s to build my first DIY speakers and your comments will be greatly appreciated. I have a tight budget and unfortunately I cannot build them both to compare. Actually, my plan in principle is to build Jim Griffin's 46' version in order to be able to eventually add the Aurum Cantus G2si if I feel it necessary (using his xover design), but I am still intrigued about the possible convenience of going for the 31'
Many thanks
Antonio |
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| abpea |
Hi Antonio,
Welcome to DIY!! :-)
The biggest differences between the two are the 31" is more narrow than the 48"er (at least the way I build them). As you've already mentioned, the 48"er will go lower than the 31". But probably the most significant difference between the two is there seems to be some harmonic interaction in the 48"er that you don't get in the 31".
I enjoy this 'coloration' in the 48"er very much. The sound of the 31" is more analytic or more, I hate to say it this way, true if you will. Now please understand I am not saying one is better than the other. Believe me you will be delighted with whichever one you choose to build. They both are truly excellent speakers.
I'm sure Colin can add some light on this as well.
Hope that helps a little -
Bruce |
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| A Sanchez |
| quote: | Originally posted by abpea
Hi Antonio,
Welcome to DIY!! :-)
The biggest differences between the two are the 31" is more narrow than the 48"er (at least the way I build them). As you've already mentioned, the 48"er will go lower than the 31". But probably the most significant difference between the two is there seems to be some harmonic interaction in the 48"er that you don't get in the 31".
I enjoy this 'coloration' in the 48"er very much. The sound of the 31" is more analytic or more, I hate to say it this way, true if you will. Now please understand I am not saying one is better than the other. |
Thanks Bruce,
I remember someone saying that the 31' has a "tight" bass response. If tight means a clear, well defined, response maybe this be a reason for its analitic character? Lets see what others say.
Antonio |
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| GM |
Correctomundo! My audio goals from the get-go has been to as accurately reproduce the signal as practical, so design vented alignments that have the accuracy of a 0.5 Qtc sealed cab in our acute hearing BW except with more gain BW.
The 48" done at Bruce's request and by far the most popular of the two OTOH is proof positive that most folks 'talk the talk' of wanting accuracy of reproduction, but the reality is most prefer some euphonic distortion to artificially replace some of the subtle ambient information often lost in the recording process, hence the continuing popularity of tube electronics and under-damped (sub) woofer cab alignments.
I've neither built nor auditioned either, but some others who have done both note that BSC is required for the 48" Vs the 31" just needing to be toe'd in per Jordan's recommendation.
As always though, YMMV.
GM |
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| Colin |
Bruce and GM beat me to it. Good summary from Bruce (who has probably built more JX92S variants than anyone on the planet). I would add that the 31 is probably the better bet if you are planning to use the speakers in corners.
Scott produced a couple of sims for me a while back, which I've added below. These may give a clue as to why the 48 needs BSC to overcome a leaness to the sound. If the 31 will do without BSC, you'll have a more efficient speaker and can always add a sub later, funds permitting.
GM's insight is fascinating. I've never been a fan of tubes but appreciate that accuracy is not the easiest aspect of sound to live with in the home. The 48s certainly draw you in and make you want to listen. They may well be more amp dependant than the 31 - the Naim amp I use has a reputation for leaness so the two balance each other to an extent.
BTW, Instead of a group buy we should instigate a group build so that GM can hear why we think his design is so good. |
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| abpea |
| quote: | Originally posted by Colin
BTW, Instead of a group buy we should instigate a group build so that GM can hear why we think his design is so good. |
Colin,
This is a truly excellent idea!!! I've been promising GM a pair of speakers forever (really GM I'm gonna get a pair to you before either of us die)! :-)
Bruce |
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| Colin |
Hi Bruce - Good plan. I have a similar commission from Ted Jordan. I'll race you ...
Colin |
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| abpea |
| quote: | Originally posted by Colin
Hi Bruce - Good plan. I have a similar commission from Ted Jordan. I'll race you ...
Colin |
Deal Colin! Although we'll have to wait till the weather warms up a bit for me to start.
Middle of winter + unheated garage workshop = Not able to cut straight lines while shivering!! :D |
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| Colin |
| Same here, though in my case it's a car port so I have the added fun of a cheery English gale whipping my drawings away into the garden. |
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| A Sanchez |
| quote: | Originally posted by abpea
The biggest differences between the two are the 31" is more narrow than the 48"er (at least the way I build them). Bruce |
In terms of dimensions, according to Jordan's page the only difference between the two apart from the height is the driver placement from the top but the original designs are equally wide.
| quote: | Originally posted by Colin
I would add that the 31 is probably the better bet if you are planning to use the speakers in corners.
Scott produced a couple of sims for me a while back, which I've added below. These may give a clue as to why the 48 needs BSC to overcome a leaness to the sound. If the 31 will do without BSC, you'll have a more efficient speaker and can always add a sub later, funds permitting.
GM's insight is fascinating. I've never been a fan of tubes but appreciate that accuracy is not the easiest aspect of sound to live with in the home. The 48s certainly draw you in and make you want to listen. They may well be more amp dependant than the 31 - the Naim amp I use has a reputation for leaness so the two balance each other to an extent.
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I am actually for flexibility in terms of placement. I want to have as many options as possible when negotiating with my wife the speakers position.
Colin, thanks for the sims. Now I have to do my homework to understand all the subtle differences in paper properly. That's the only way to learn.
I would have never thought that accuracy could be an issue when one is in principle looking for (high) fidelity. You and GM are really making me think. I do want something I want to listen without much fatigue even if some coloration is around.
I hope my Sonographe amp and pre amp (a 1980's Conrad Johnson entry level models) do a good job with Jordans either with the 48 or 31.
Anyway, thank you all for your replies, which make the decision more difficult but a lot more interesting!
Antonio |
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| Colin |
I think Bruce produced a wider front version of the triangle than is shown on the Jordan pages. You could do this with either of the two MLTL designs, so don't worry about that too much.
I've found the 48 a joy to listen to, pulling out bass lines and information I have not heard before. It's only once been caught out by a track which sounded overblown. But the design as shown on the Jordan site does need the BSC to avoid a thinness to male voices. Again, a wider baffle might sort that and warm up the sound at the expense of a bulkier-looking cabinet.
My previous Jordans - a JX53/JX125 design - had a sealed cabinet aligned to 0.7 which rolled off below 45Hz. So in theory more accurate than the 48s. It sounded good but upon hearing the 48 triangles, my partner's reaction was: "Sell the old ones".
My reading of Scott's sims - given that I have only heard the 48 version - is that the 31 may not sound as initially exciting as it doesn't have the lower bass kick of the 48. And that kick may come from the low bass being exposed compared to the lowered output in the 150-400Hz region. Given that you have tube amplification (I assume, I'm not familiar with the model), perhaps the 31 is the one to go for, the accuracy of the bass balancing out any warmness from the amplifier.
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| abpea |
| quote: | Originally posted by Colin
I think Bruce produced a wider front version of the triangle than is shown on the Jordan pages. You could do this with either of the two MLTL designs, so don't worry about that too much. |
Antonio,
What Colin suggests in the quote above is exactly what I do. The baffle on my 48"ers are significantly wider than the plans call for. I tried a BSC on my 48"er and didn't like it so I listen to mine wired straight from the amp to the driver. Never thought the 31" version needed a BSC either.
Go for it, you'll not regret building either design.
Bruce |
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| A Sanchez |
Bruce/Colin
Thanks for your replies/advise.
The Sonographe is a Mosfet amp and apparently Mosfet transistors produce a very tube like sound.
I like the idea of the triangular shape to avoid reflections but I am a bit afraid of the construction difficulties, mainly of having the wood angles perfectly cut and then I imagine that the clamping/gluing/bracing process is easier with rectangular shapes than with triangles. There is a CNC cutting company in London that would do any cut at a reasonable price but they do MDF only and I have not found a company that would do he same with plywood (all these things in London are particularly expensive).
My problem is that I will build the boxes in the London way: that is, in my little kitchen...
I will definitely go for it but will decide the size/shape tomorrow evening after work and a couple of drinks.
Antonio |
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| A Sanchez |
Actually what will really help me decide between 31' and 48' is this:
Which one in your opinion performs better (in terms of balance between highs mids and lows) at lower volumes??
I wonder if the 48' would show its capabilities in the low range also at low volumes.
Your feedback will again be very appreciated.
Antonio |
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| Colin |
Okay, Bruce is your man for the comparison.
Re the 48, I'm happy listening at low volumes - my listening levels peak at 85dB and are usually in the upper 70s dB - and the bass seems to provide enough drive to keep toes tapping at low levels.
Interesting question whether a more accurate speaker would need more volume to come alive. I wonder if GM has any information on this. |
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| Nardis |
Antonio
I sent you an off-board email inviting you to contact me by phone.
I'm running a pair of 48" MLTLs in Chiswick, West London. I don't know which part of London you are in, but you are welcome to come and hear them if you want. They are pentagonal and have a ribbon tweeter using a xover based on Jim's but I can easily run them without the ribbon and xover as in the original design.
I also have some suggestions about getting the wood cut.
Please check if you got the email and contact me or post a reply if you if you didn't. I don't want to put my phone number on the web. |
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| A Sanchez |
Nardis, Thanks very much. I got your e-mail but I could not reply earlier. Your offer is very welcome and appreciated. Nothing like listening to the speakers myself. I will e-mail you in a moment.
Thanks Colin. The issue of low volume came to my mind when I thought about the reality of home systems (at least my reality). Apart from the few times I will find to enjoy the speakers at mid- high volume, most of the time I will be listening to music while spending time with my wife and daughter and honestly we cannot cope with high volumes for a long time. However, that does not mean I like having, damped, semi-dead or indistinguishable music playing at the back. Also, it is nice to be able to play a nice music passage for others without blowing everyone ears and stopping completely the flow of a conversation because the music needs to be very loud for the speakers to come alive . I know this topic is very subjective, but anyway this is my view.
Lets see what the others say about low volume performance of these speakers.
Antonio |
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| abpea |
Hey Antonio,
With regards to low level listening between the two I favor the 48"er.
One other significant difference, as you may have noticed on the drawings, between the two cabinets is the 31" port fires down and the low level sounds are 'bounced' into the room. It is very pleasing but you don't get that low level 'thump' in the chest with some music.
My 48"ers are ported directly out the front of the baffle. You wouldn't think it would make much of a difference but it does. I find that the low end on the 48"er has more energy and 'thump' compared to the 31". That's one of the reasons (the nice harmonic distortion GM mentioned earlier being the other) I like the 48"er better at low levels than the 31".
Certainly if you have the chance to listen to a nicely built pair do it. I'm sure you'll enjoy it. The other thing I was going to say was build them both!! :)
Have fun -
Bruce |
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| A Sanchez |
Bruce,
What you are saying is what I imagined somehow. However, I also thought that a bigger cabinet would require more volume for the sound to come alive than a smaller one since the driver would need to generate more pressure for the low frequencies to emerge. I do not know the theory or the mechanics involved and am just speculating. I'll try to do my homework but it would be interesting to hear some more expert opinions.
Next week I will try to listen to Nardis' 48's . It would be great if there was a Londoner with 31's to compare.
I know myself and am sure I will end up building them both, but at the moment that is too ambitious.
Antonio |
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| A Sanchez |
| I wonder if BSC makes speakers to be less efficient/responsive at low volumes?? I have not found he answer anywhere although it seems logic that the above is true. Any ideas? |
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| GM |
| quote: | Originally posted by A Sanchez
However, I also thought that a bigger cabinet would require more volume for the sound to come alive than a smaller one since the driver would need to generate more pressure for the low frequencies to emerge. |
If the cab is just a bigger rectangular box, you're right, but the point of pipe loading is to let it do the work, so actually takes less power for a given SPL, but the price you pay is increased distortion in the form of increasing delay of the driver and port signals with increasing length with the 31" being what I consider the max acceptable trade-off between pipe gain and excessive delay for this particular driver's specs.
GM |
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| GM |
Audio often isn't very intuitive unfortunately, BSC will make it sound more balanced than not assuming it has a low insertion loss, i.e. low Dcr components ($$) to keep electrically raising the driver's effective Qts to a minimum.
GM |
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| Colin |
Clearly I am going to have to build the 31 as well to hear the difference for myself. I needed an Easter project.
Am I correct in assuming that an internal sized 10" wide, 3" deep cabinet - to give a wider baffle and allow a side-firing port - would not alter the pipe action too much? |
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| A Sanchez |
| quote: | Originally posted by Colin
Am I correct in assuming that an internal sized 10" wide, 3" deep cabinet - to give a wider baffle and allow a side-firing port - would not alter the pipe action too much? |
Interesting. That would look similar to the Jordan's VTL from the outside. |
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| GM |
| quote: | Originally posted by Colin
..........- would not alter the pipe action too much? |
Correctomundo! Aspect ratios > ~9:1 add enough friction running towards aperiodic with increasing ratio, so in most cases the driver's depth limits how much you can 'pancake' them.
FWIW, my most popular designs were these except instead of a rectangular shape the baffle was 'bent' back to side firing vent(s) as required. IOW a simple vertical kerf on each side of the driver to 'break' the baffle back to whatever aspect ratio side firing vent(s) up to ~9:1 tuned it to minimize thickness at this point. Due to not having any elaborate test gear or design software, tuning was accomplished by starting with the sides brought ~ to an unfinished, unsecured point, then I would cut small, equal 'slices' off each side until I got a ~flat in-room response. Obviously time consuming and may render the speakers ~ useless if relocated, but with today's software you could design in removable vent ducts.
GM |
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| dsb |
hello,
After much reviewing I am strongly considering building the triangle 48er. Recent posts #54 and 55 - making the triangle wider - gives rise to a question:
I assume 'wider' refers to the baffle's external front face only, both the internal cross sectional area, maintaining the as-illustrated equilateral triangle, and volume remain the same? Also, although I promise not to "worry about that too much", a few inches, 12 inches, more?
Very generally, if the front face of the triangle 48er had surface curvature, are there any guidelines on this or with this design the front baffle should remain flat? I notice numerous commercial and some diy speakers have all manner of front baffle face surface geometry, grooves, etc., accompanied both by convincing as well as dubious claims of increased performance.
Thank you. |
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| abpea |
Hi dsb,
You are correct, maintaining the cross-section area and other internal dimensions is critical. You can be as 'artistic' as you like with the external part of the cabinet.
The front baffle on my 48"ers is 1" thick and 23" wide. Some people will say a 1" baffle is overkill, but I had the wood and it looks great! :) You can make the front baffle as wide as you like. I think wider makes it better.
Can't help you much about the curved front baffle. Sounds interesting though.
Stay warm -
Bruce |
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| planet10 |
GM,
Did you use the published specs for the GM48 & GM31?
This data just in from a sampling of the latest 100 from Sweden
http://www.diyaudio.com/forums/show...136#post1426136
| quote: | Here are the average values of the T/S parameters for the 20 drivers that were measured (not broken in):
DCR 5.2 ohms
Fs 58.6107 Hz
Qms 1.0726
Qes 0.3645
Qts 0.2720
Vas 10.2355 L |
higher Vas, lower Q, lower Vas than spec
dave |
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| GM |
Greets!
I just used the published specs at the time and bumped up Qes/Qts a little bit to account for VC heating since JG's small monitor measured pretty much dead on and TJ's TL simmed good using them. For sure, I find it hard to believe that any of these alignments would be popular based on how they sim with these latest specs.
GM |
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| GM |
| quote: | Originally posted by dsb
I assume 'wider' refers to the baffle's external front face only, both the internal cross sectional area, maintaining the as-illustrated equilateral triangle, and volume remain the same?
Very generally, if the front face of the triangle 48er had surface curvature, are there any guidelines on this or with this design the front baffle should remain flat? |
Greets!
Right, though the internal angles can be changed as long as the CSA is at least as large as spec.
WRT curvature, consider the size of the WLs involved. A 100 Hz WL has a ~21.6" radius, so even if it was ~21.6" wide measured on the 'flat' it wouldn't have that great of a curvature acoustically as far as higher frequency wave launch was concerned.
Where curvature plays a role in superior performance is reducing standing waves amplitude or getting rid of them altogether and the funky shapes some cabs have are addressing this issue. Here you have to work with the 1/2 WL length size of two end points, so our ~21.6" baffle is going to be slightly longer over its surface or ~308 Hz wide, so to reduce its standing wave amplitude considerably we have to round over the edges with a 7" radius, leaving a curved center section that now looks ~flat, though as far as the 100 Hz wave launch is concerned it still looks relatively flat acoustically.
GM |
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| Colin |
| There's a discussion of a curved MLTL on this thread complete with pics. Looks erm fun ... |
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| A Sanchez |
Hi,
Back to the project.
Last week I paid a visit to Nardis' who very kindly offered me the chance to listen to his pentagonal 48’ towers. I was very impressed by the speakers, which by far exceeded my expectations. Nardis has very high quality equipment and I would be happy if the drivers perform half as well with my set up. The pentagons look very elegant and I am sure the smaller panel areas and having no parallel sides are an important plus in sound quality, but at this first stage I prefer not to get into the trouble of cutting and assembling that design, which is a bit tricky.
I have decided to go for the 31’ version. Since I am new to this and do not have much parameters to compare, I believe it is better to start by getting used to the design which is more “pure”. In any case after listening to Nardis' 48’s I can see that there should also be plenty of bass power for my needs and room size with the 31’version . My current B&W 601s have frequency response down to 70hz and I already feel is quite a lot. So if I get down to 45hz with the 31’s that should be more than enough for me (at least for now).
I already have the drivers and I just have to decide about the design:
One option is to do the 31’ using the baffle size applied by Jim Griffin with his mini monitors and his 46’ Jordan MLTL version (7.5’) as this would allow me in the future to add the Aurum Cantus G2Si using Jim’s crossover configuration, which is a proven design. I will obviously keep the original CSA intact.
Since I have some problems with WAF, another option is to copy DIAR’s design http://kotiweb.kotiportti.fi/~w4398...Jordan/Jordan1/ which in my opinion has the most elegant looks as the narrow (only around 6') baffle produces, aesthetically, very nice proportions, by increasing the depth in order to keep the original CSA. From what I have learnt the problem with this design would be that Jordan’s perform better with wide baffles. But, would you think there would be a clearly noticeable difference between 6 and 7.5 inches?
Another thing I was thinking was to build the bottom window at the back instead of the front. I thought this may help to have more room interaction and possibly more room gain on the lower frequencies by trying different locations. Would anyone think this could be counterproductive?
Your comments will be again very appreciated.
Best regards
Antonio |
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| t-head |
Antonio,
I have not found a problem with my 6.5" baffle and rear-firing port, placed against the front wall (actually 3" away). In comparison with similar design with wider (11.75") baffle, marginally more/lower LF are detectable, but I am happy with my narrow baffle. YMMV
t |
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| A Sanchez |
| quote: | Originally posted by t-head
Antonio,
I have not found a problem with my 6.5" baffle and rear-firing port, placed against the front wall (actually 3" away). In comparison with similar design with wider (11.75") baffle, marginally more/lower LF are detectable, but I am happy with my narrow baffle. YMMV
t |
T-head,
Do you have GM's 31' MLTL? the thing with the 31' version is that as a matter of fact the port fires downwards and I am just intending to move the window to the back, which might not make much difference. I imagine that few inches would not much difference in terms of baffle size, except maybe for very well trained ears
Antonio |
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| t-head |
Antonio,
No, I have the JLMs from Carolina Audio. 36"x6.5"Wx6A"D. I imagine the design internals similar to the triangular design on Jordans site. Quarter-wave, 3x folded design with rear-firing rectangular port.
http://rthack.tripod.com/KOTA/Page_7.html
wider baffles do assist bass, but I have not found the difference huge...Good Luck with your build!
t |
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| BWRX |
Zaph will be measuring a pair of drivers and johngalt47 will also be measuring his pair using Woofer Tester 2, so we should have some better numbers than the ones I came up with ;) |
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| A Sanchez |
Another quick question: Does the the down-firing port have to be positioned right in the middle of the bottom panel or I could place it towards the front?
Many thanks
Antonio |
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| GM |
The WLs are so large I don't see how it matters.
GM |
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| Colin |
| It's worth bearing in mind that the drivers like a little space around them inside the cabinet, which would deter me from building a design with too narrow a front baffle. The wider baffle helps the lower mid and upper bass, giving it a fuller sound. You can always compensate with BSC, at the expense of a little efficientcy. |
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| Nardis |
| quote: | Originally posted by Colin
It's worth bearing in mind that the drivers like a little space around them inside the cabinet, which would deter me from building a design with too narrow a front baffle... |
That's one of the reasons why I went for the pentagonal MLTL - it's an attempt tp get the best of both worlds. I was also influenced by the section on cabinet shapes in Martin Colloms' "High Performance Loudspeakers"
See the attached PDF which shows how the JX92S "breathes" in this shape.
Has anyone tried them in some 6 inch diameter pipe? The CSA of the pipe is just over 90% of GM's design, so there would have to be some trade-off. |
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| Colin |
| I located some 6 inch diameter cardboard tube used as the centres by the paper making industry. In the end, I didn't use them as the MLTL required a 9 inch diameter if I was to use half as a semi-circular cross-section cabinet. I've yet to go and see if tubes that size are available. The cardboard was good and solid and came in four foot lengths. |
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| t-head |
Colin,
I am curious if you have actually heard a narrow baffle design, or if your comments are based on purely conjecture, or prediction from specs? This is a friendly question...;) I am learning...
t |
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| Colin |
Hi - Yes, I've compared my own triangular MLTL against both the 12 inch VTL and a narrow Augusperger TL. They all had their own characteristics but the comparison between the MLTL and VTL was the most interesting. The VTL sounded much fuller but didn't go as deep. The MLTL matched it better when BSC was added.
I haven't tried a properly adjusted BSC on the smaller TL yet. It's not a design I plan to pursue.
Of course, the MLTL and VTL are very different designs, so I'm sure some of the difference was down to factors other than the baffle width. But they did sound a lot closer in the lower-mid with BSC. It was particularly noticable on female voices.
I can see why Ted, among others, prefer the wide baffle approach, although I do like the appearance of the narrow designs. There is a quick way you can try it out with a narrow-baffle enclosure; place a board on one or both sides to temporarily extend the baffle and see how it alters the sound. |
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| A Sanchez |
Hi,
I have started building the 31' Jordan MLTL and am ready to glue the panels. I am using 3/4' birch ply (13 layers, dense and strong, but am not sure it is "baltic") So, just one question:
I could still add one window brace (4.92' x 6.10 with a 4' hole) just below the drivers (which will also help to keep the damping material in place). It will take some box space and I do not know if bracing is factored in this design or if this does not matter.
Thanks
Antonio |
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| Colin |
| I used a window brace (I believe Jim's design does too) but further comments from GM make me wonder if it is such a good idea. The design relies on the vertical resonance of the enclosure, so perhaps someone has a better solution? At any rate, if doing it again, I'd make the window 'frame' as narrow as possible. |
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| A Sanchez |
Thanks Colin.
I read a lot about bracing the 48' version, where bracing is understandable because of the length. However the 31' might not need bracing or might be more sensitive to it as it is suppose to have the "right" size. Lets se if GM could give us his view.
I forgot to say that I am putting a double top by the way.
Antonio |
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| GM |
| quote: | Originally posted by A Sanchez
I could still add one window brace (4.92' x 6.10 with a 4' hole)..............and I do not know if bracing is factored in this design or if this does not matter. |
Greets!
No, since when made from a suitably rigid material (no void 19 mm 11 ply plywood or higher MOE), pretty much any pipe with a < ~144"^2 CSA or any panels < 12" wide doesn't need any bracing except for the driver and until it gets really massive will benefit from additional top down mass loading such as from a heavy potted plant, barbell weight(s), etc..
While I have no scientific proof that window braces negatively affect pipe action, ~analogous high pressure water flow indicates there would be a strong disruption in pipe dynamics, so do not recommend them, instead preferring golden or acoustic ratio offset longitudinal braces on edge combined with dowel or similar 'X' braces staggered down the pipe to tie all six sides together.
That said, if the cutouts are large enough that they mimic the 'X' braces and rigid fiberglass insulation panels are used to the line the walls to fill in the perimeter flange to provide a smooth pipe perimeter, then you 'kill three birds': bracing, damping, and mass loading. Done this way, the pipe's CSA would be measured from the insulation wall's i.d. dims rather than the basic shell's.
Regardless of bracing scheme chosen, 'God' (or Devil, depending on your POV) is in the details, so any bracing/object out in the airstream should be damped to prevent any spurious reflections/eigenmodes (standing waves) IMO.
GM |
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| A Sanchez |
GM,
Many, many, thanks for such a detailed, useful and interesting reply!
The project continues (no bracing needed in this case).
Best regards
Antonio |
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| A Sanchez |
| quote: | Originally posted by GM
doesn't need any bracing except for the driver
GM |
GM,
What do you mean by "except for the driver"
Thanks
Antonio |
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| planet10 |
| quote: | Originally posted by Colin
I used a window brace (I believe Jim's design does too) but further comments from GM make me wonder if it is such a good idea. The design relies on the vertical resonance of the enclosure, so perhaps someone has a better solution? At any rate, if doing it again, I'd make the window 'frame' as narrow as possible. |
It is better to run the braces the other way -- vertically. This would give box bracing, and act as a driver brace (more important IMHO). Make the brace holey.
dave |
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| GM |
Huh! When I copied/pasted my response I unintentionally left out this paragraph:
"Dave P10's vertical panel bracing scheme is obviously excellent from a structural POV, but I wonder about how the cutouts in them affect pipe action due to their high friction. Then again, the additional friction may be beneficial from a stuffing density POV, so as always YMMV."
GM |
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| GM |
| quote: | Originally posted by A Sanchez
GM,
Many, many, thanks..........
What do you mean by "except for the driver" |
You're welcome!
As Dave noted, bracing (aka mass loading) the driver to both support it if heavy and pre-load it to the cab to maximize its acoustic efficiency is key to getting the 'tightest' response from a given driver/alignment.
GM |
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| Colin |
Hi Dave and GM
Does this mean that the 90s fashion in UK commercial speakers (KEF amongst others) for decoupling the driver from the cabinet was misconceived or are the quarter wave alignments a special case? |
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| Corloc |
So, a cabinet with vertical brace is alright? Any ideas or concerns for this 31" MLTL?
The idea was to make a lamination a little less wasteful. All angles of the lamination are 45 or 90 deg.
Chris |
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| planet10 |
| quote: | Originally posted by Colin
Does this mean that the 90s fashion in UK commercial speakers (KEF amongst others) for decoupling the driver from the cabinet was misconceived |
IMHO yes misconceived
When we got the 1st shipments of the KEFs with the decoupled drivers we quickly discovered that they sounded better when you cranked down the scres such that the isolation was short-circuited.
dave |
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