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-   -   Greg Monfort ML-TL Design Update for Alpair 10.2 (http://www.diyaudio.com/forums/full-range/230095-greg-monfort-ml-tl-design-update-alpair-10-2-a.html)

NewMountain 15th February 2013 04:31 PM

Greg Monfort ML-TL Design Update for Alpair 10.2
 
Hello,
I am interested in building Greg Monfort's ML-LT Design shown on Dave's site
http://www.frugal-phile.com/boxlib/GM-A10-MLTL.pdf

I am most interested in the extremely shallow depth (especially without bracing), tall height, and of course the Alpair 10.2.

Since this design is modeled for the Alpair 10, would anyone be interested in reworking it for the 10.2?

Or creating a similarly proportioned design for the Alpair 7?

No patience for math but I can make a mean cabinet.

Thx!


cogitech 15th February 2013 04:53 PM

Watching with interest.

Somehow I failed to notice this design while researching A10.2 cabinet possibilities.

Jim Griffin 15th February 2013 07:42 PM

My version of a MLTL for the Mark Audio Alpair 10 or 10.2 is also in the Frugal-phile library at:

http://www.frugal-phile.com/boxlib/G...LTL-030611.pdf

This design will work with either the 10 or 10.2 driver versions. You can change the width or depth of the enclosure as long as you retain the cross-sectional area the same value. You can get creative by changing the port to exit via a side wall or the bottom.

The other concern would be allowing the driver some space within the box for mounting and breathing room if you thinking of a very slim box. Plus often a wide baffle is used to place the baffle step transition where you want it.

Typically, you can achieve a lower bass frequency cutoff if you lengthen the port an inch or two. Conversely, you can reduce the bass cutoff by shorten the tube length.

What depth and width are of interest to you?

NewMountain 15th February 2013 09:32 PM

Hello Jim,
1) I would like to acheive a 6" internal width (per your design).
2) Extremely shallow depth, 4" or 5" if possible.
3) Higher dimension from floor to center of driver. Anywhere between 40" to 45".

If I maintained your internal volume, stole a couple of inches from the depth of your enclosure design and added to the height, how does the distance relationship between port / driver / top of enclosure adjust?

Thanks for your interest and help!

chrisb 15th February 2013 11:35 PM

Quote:

Originally Posted by NewMountain (Post 3371526)
Hello Jim,
1) I would like to acheive a 6" internal width (per your design).
2) Extremely shallow depth, 4" or 5" if possible.
3) Higher dimension from floor to center of driver. Anywhere between 40" to 45".

If I maintained your internal volume, stole a couple of inches from the depth of your enclosure design and added to the height, how does the distance relationship between port / driver / top of enclosure adjust?

Thanks for your interest and help!


I'd suggest reconsidering very shallow depth enclosures for any wide-band driver, and most particularly very thin metal cone units such as any of Mark's drivers or the new Jordans for example.

The excellent performing M10A10 design by Bob Brines for the 10.2 has a CSA of 64in^2 ( 8x8) - as has been mentioned, with an MLTL you can play with the aspect ratio of those dimensions a bit, but I'd be more inclined towards narrower and deeper than the other way around.

GM 16th February 2013 12:01 AM

Quote:

Originally Posted by NewMountain (Post 3371132)
Since this design is modeled for the Alpair 10, would anyone be interested in reworking it for the 10.2?

Greets!

You can use it as is or extend the vent to 4" for a ~Fs tuning.

GM

xrk971 16th February 2013 12:05 AM

Ted Jordan's VTL for the JX92 is 4 in deep. I think you can successfully flatten designs and preserve CSA to a certain extent but the flatter it is, the fewer acoustic modes you can support in the short direction and the character of the sound will be different. I took a 6x8 in CSA from a BIB design and flattened it to a 3 x 16 in for a wall mount BIB and it still worked but I think at the expense of a richer sound and it forced a resonance that matches the 16 in width to crop up. closer to rectangle proportion of golden ratio will sound better. Taken to an extreme, I would imagine that a nominal 6x8 flattened to 1 x 48 will not sound the same at all.

planet10 16th February 2013 01:36 AM

1 Attachment(s)
Quote:

Originally Posted by xrk971 (Post 3371680)
Ted Jordan's VTL for the JX92 is 4 in deep

Perhaps not a good example.

http://www.diyaudio.com/forums/attac...1&d=1360982151

dave

Jim Griffin 16th February 2013 01:48 AM

1 Attachment(s)
NewMountain,

My Alpair 10/10.2 MLTL design has an internal cross-sectional area (6” wide by 5.25” deep) of 31.25 sq inches. The external dimensions are 7.5” by 6.75” assuming 0.75” thick material. As I stated earlier you can change the width and depth as long as you maintain a CSA of 31.25”.

Greg Monfort’s Alpair 10/10.2 design has a CSA of 26 sq. in. (6.5” by 4.0”). I haven’t seen a photo of a MLTL built with his design but likely Planet 10 has a link.

Bob Brines has an Alpair 10.2 design that has an internal CSA as large as 64 sq inches with 0.75” thick material per dimensions from his website.

On your comment of a depth of 4 to 5 inches are you relating the internal or external dimensions of your space limitations? Also with a MLTL you cannot trade length for CSA—it isn’t a direct volume consideration. You can trade length (as pointed out by Planet10) for performance--the 3 dB low frequency point is the trade.

The three designs listed above would likely provide pleasing results. It would help for us to know your specific performance goals to discern which design would best fit your needs.

Finally, I have attached a MLTL family photo of my Jordan JX92S design (the Jordan with a ribbon variant), an Alpair 6 design, and the Alpair 10/10.2 design.

If I can be of additional help, let me know.

Jim Griffin

NewMountain 16th February 2013 07:30 PM

1 Attachment(s)
Quote:

The three designs listed above would likely provide pleasing results. It would help for us to know your specific performance goals to discern which design would best fit your needs.
I spend 8hrs a day behind my computer so I’m looking for a “good as possible” desktop solution.

My Desk is located in a retail store and there are some limitations.

The actual desk is very shallow so I currently cannot get the speakers back as far as I like.

Speaker location off the floor needs to be taller than normal (40” to 45”) to be at ear level, minimize reflections off the desk surface, and produce better imaging.

Speakers will be pulled quite far (6 feet) off the back wall. And there is a walkway behind them.

They need to be a slim, attractive design since they are out in the open.

I’m not sure what qualifies as near field but I am finding I like the sound with the speakers about 4’ apart, and about 4’ to 5’ back from my listening position.

With the 6P Fonken’s aimed up and with my chair rolled back the sound is crazy good. These replaced a set of Tekton’s with Fostex 127’s and I understand the Mark Audio magic now. Really different sound.


The obvious solution is stands, but I am so enamored with the Mark Audio Drivers I want to try some additional models and designs. I’ll use the Fonkens at home.

Greg’s Design looks pretty much what I’m looking for proportionally, provided the enclosure works with the 10.2. I would be tempted to build it without the brace for the super skinny version, but it sounds like this should be avoided.

Or Jim’s version with a 10” taller cabinet and dead space below the enclosure will work too.

Jim, Your Floor standing Alpair 6 design looks really interesting too!!!

I wouldn’t mind building these also so I can compare with my Planet 10 boxes. Have you shared this design publically and will it also work with the 6P (looks like yours are6M)?

Thx to all for your input and recommendations.


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