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MLTL for dual Jordan Eikona Drivers
MLTL for dual Jordan Eikona Drivers
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Old 5th December 2017, 02:38 AM   #31
GM is offline GM  United States
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This specific link: Jordan Eikona 2 Designs

OK, all is clear now, he chose to use the 1/5th harmonic for the driver location Vs the more popular 2/5ths or 1/3rd that most folks, including him, normally use, hence the need for much more damping due to the 'stronger' eigenmodes.

I totally missed the 30" height spec though and it should have been noted from the get-go since as Scott pointed out, this is going to put the top driver too close [~1.47"] to the top, which combined with heavy damping is going to 'muffle' it somewhat, so recommend either moving the driver's midpoint down to at least ~0.349*30 = ~10.47" or going to a taller cab if the drivers/floor height is already where you want it.

Offsetting is a good plan and use to recommend it a lot on wider baffles, but none bothered AFAIK, so gave up. I doubt it audibly matters though on narrow baffles where it's not much wider than it needs to be to mount 'FR' driver[s]. With a 43 Hz Fs, 11" i.d. baffle, its eigenmodes comb filtering with the driver's output might be audible off the front, so recommend a golden or acoustic ratio offset: 1.00:0.618, 1.14, 1.17, 1.25, 1.26, 1.28, 1.39, 1.41, 1.47, 1.54, 1.60, 2.1 were the most common decades ago, so with '1.00' being the outer edge of the [mirror imaged] baffles, pick one that doesn't put the driver too close to the inner side wall.

Once you move away from polyfil, the only thing you can do is experiment with different materials, density till you find something that sounds good to you, i.e. it no longer sounds 'hollow' and maybe some more if the [mid]bass, or lower mids sound too resonant/whatever.

GM
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Old 5th December 2017, 07:27 AM   #32
Colin is offline Colin  United Kingdom
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Here are the plans of the ML30

http://www.ejjordan.co.uk/PDFs/Eikona_MLTL30.pdf

The ML38 or one of Jim's taller designs would be a better choice for a double MLTL

http://www.ejjordan.co.uk/PDFs/Eikona_2_38_MLTL.pdf
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Old 6th December 2017, 08:01 AM   #33
colmo is offline colmo  United Kingdom
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Hi GM
Couple of questions to clarify things, if the mid point is now1/3rd down should it not be 10" not 10.47" or is there a reason for this.
Dont quite understand the golden ratio thing if I want to offset the least what should the offset be, I was going to do same as Jordan DCR 20mm.
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Old 6th December 2017, 08:52 AM   #34
Scottmoose is offline Scottmoose  United Kingdom
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I'm not GM, but FWIW the 0.349% offset is what Martin King specifies as the tap location for an untapered pipe in his alignment tables.

Golden ratio = 1:1.618 so for any lateral driver offset use said (providing there is sufficient clearance), i.e. lateral offet = external baffle width x 0.618. If that does not provide sufficient clearance, then use one of the other ratios GM mentioned. Ensure the cabinets are mirror imaged if you use a laterally offset driver.
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Old 6th December 2017, 12:37 PM   #35
colmo is offline colmo  United Kingdom
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What would 1.14 offset mean when measured a cross the baffle width.
I assume we are talking about offset from the vertical centre line for both drivers.
Also should I use two ports or one.
I have also discovered that I can buy Acousta stuf Polyfill in the UK how much should I use in each cabinet.
One more thing does moving the drivers down affect the bass response, will I still get -3db @30hz.
The drivers are a bit low now but I can put a small base under to lift the speakers.
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Old 6th December 2017, 01:36 PM   #36
Colin is offline Colin  United Kingdom
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We've used BAF and it's been OK and easy to adjust. Don't get too hung up on the details at this stage as you can adjust later.

We have a customer use some very fine material called Angel Hair but the results in the MLTL40 weren't as good as BAF, imo.

Mundorf Twaron Angel Hair Wadding | Hifi Collective

Rather than add a base to the MLTL30, would it not be easier to build one of the taller designs and get added bass extension?
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Last edited by Colin; 6th December 2017 at 01:39 PM. Reason: link
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Old 6th December 2017, 05:05 PM   #37
colmo is offline colmo  United Kingdom
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Quote:
Originally Posted by Colin View Post
We've used BAF and it's been OK and easy to adjust. Don't get too hung up on the details at this stage as you can adjust later.

We have a customer use some very fine material called Angel Hair but the results in the MLTL40 weren't as good as BAF, imo.

Mundorf Twaron Angel Hair Wadding | Hifi Collective

Rather than add a base to the MLTL30, would it not be easier to build one of the taller designs and get added bass extension?
Hi Colin
Thank you and all the other members for your help.
I Would rather stick to the 30 inch high design with a small base to bring the dual drivers up to required height.
Sorry but I am one of those people who like to have a clear idea of what they are doing before going ahead so the minor details are important even if they are just a starting point.
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Old 7th December 2017, 02:38 PM   #38
colmo is offline colmo  United Kingdom
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One of the reasons that I want to use the 30 in high cabinet instead of the taller cabinets is that I will be using a fairly wide baffle and will place the cabinets very close to the back wall, but about 6ft from corners.
This will obviously give quite a bit of room gain lower down and I am hoping that I will not need any baffle step correction.
Trying to finalise my design and this is what I am thinking of doing
Cabinet internal dimensions 30 ins. high x 112 sq. ins.csa.
Centre point of the 2 speakers 10.47 ins down from top internally.
Speaker frames 1 in. apart.
Offset drivers 50mm and make 2nd cabinet as a mirror image.
2 x Ports 2.0 ins. internal dia x 6 ins. long located 2ins. centre from internal bottom.
Is all the above ok to give performance of Jim Griffins design.
Final thing is damping / stuffing.
I could use 8mm wool felt as Scottmoose suggests the type sold by Jantzen Audio.
Will this be enough or should I just use Acousta Stuf Polyfill and if so how much per cabinet.
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Old 7th December 2017, 03:06 PM   #39
Scottmoose is offline Scottmoose  United Kingdom
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I didn't say 8mm. I said 1in (25mm) acoustic fiberglass or SAE-F10 rated felt. If you stuff it: use the amount specified and adjust as you see fit.
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Old 7th December 2017, 03:43 PM   #40
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Quote:
Originally Posted by colmo View Post
Hi GM
Couple of questions to clarify things, if the mid point is now1/3rd down should it not be 10" not 10.47" or is there a reason for this.
Greets!

If it was a closed pipe, then it would be ~0.333, but the vent shifts it down a bit, so its odd harmonics wind up being ~0.21, 0.35, 0.42, 0.70, 0.85, though in most cases using the 0.2, etc., will work just as well since typical damping density will drop it to inaudibility.

GM
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Last edited by GM; 7th December 2017 at 03:45 PM.
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