Greg Monfort ML-TL Design Update for Alpair 10.2

[NewMountain]

Hello,
I am interested in building Greg Monfort's ML-LT Design shown on Dave's site
[FONT=Skia-Regular_Regular][FONT=Skia-Regular_Regular]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!

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[cogitech]

Watching with interest.

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

 

[Jim Griffin]

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/Griffin-A10-MLTL-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]

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]

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]

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]

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]

Ted Jordan's VTL for the JX92 is 4 in deep

Perhaps not a good example.

dave

 

[Jim Griffin]

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]

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.

 

[xrk971]

Perhaps not a good example.

dave

I never knew it would sim so poorly - is it lack of stuffing? Anyhow, I was trying to point out that there are thin 4 in designs around. It's tough to beat rectangular csa MLTL for a smooth response. Do you think the MJK sim would break down if aspect ratio became very flat? Well, at some point you run out of depth for driver magnet, so practical limit is like 3 in.

 

[planet10]

I never knew it would sim so poorly - is it lack of stuffing?

It is an example of classic TL design.

dave

 

[NewMountain]

Greg Monfort's MLTL Ver. 10.3 / 10P

In the spirit of GM, GREETS!
I never got my hands on a pair of Alpair 10's before they disappeared.
I do however have a pair of the new 10.3 metal cone and 10p paper cones.
I'm still interested in Greg's mltl design for the alpair 10's (either flavor) due to the higher driver position off of floor and slim proportions.
Would anyone be interested in updating Greg's design for one or both of the new drivers.
Or I am CAD handy myself and would be glad to draw up if someone provides the data.
Not a math cad guy but I can make a mean box.
I'm wrapping up Jim Griffins alpair 6 mltl build, and will be starting Bob Brines alpair 12p build shortly, so looking forward to a Mark Audio hat trick!

 

[Scottmoose]

It should go in & work reasonably as-is, on the basis of a quick look. I think it's better to leave any changes to Greg himself though, since I for one wouldn't have the brass face to interfere with his design.

 

[GM]

Greets!

As Scott noted, the cab is acoustically large enough and the various driver’s specs close enough that any of these will work well enough in the existing alignment, but with the 10.3, the bass will be rolled off a bit more than with the 10.2 or you can increase the WxD to 7.56” x 4.625” i.d. to maintain the original’s aspect ratio and get a bit more bass than the 10.2 in the existing design while maintaining the ~ same roll off Q.

To get ~ the same roll off Q with the 10P.1, a 9.5” x 5.875” i.d. WxD is desirable along with shortening the vent to baffle thickness.

Hopefully, Dave p10 will make some new drawings from the existing one since just a few dims need changing.

Being a ‘BIB’ kind of guy, hope you build to the larger dims to compare to the other designs and report back here with them.

GM

 

[cogitech]

So exciting watching the next wave of drivers inspiring both new designs and revisions of proven boxen.

I am a few months away from getting a pair of 10.3s but when I do I am thinking of taking a "no holds barred" approach. There is a design that I have in mind that I think the A10 family really deserves. So much so that I might be willing to "donate" a respectable sum of money to have it professionally designed. Hoping the usual suspects might be interested in my idea.

 

[NewMountain]

Greg, Thank you so much for the updates to your design!!!
I will build one or both with the new dimensions and report back.
Looking forward to others' build logs and experiences too.

Has anyone heard any feedback on the Alpair 10.3 yet? Hoping it closes the gap with 7.3.
Scott, thx for your thoughts on the new 10P.

 

[GM]

You're welcome! Looking forward to how it all pans out.

GM

 

[xrk971]

So exciting watching the next wave of drivers inspiring both new designs and revisions of proven boxen.

I am a few months away from getting a pair of 10.3s but when I do I am thinking of taking a "no holds barred" approach. There is a design that I have in mind that I think the A10 family really deserves. So much so that I might be willing to "donate" a respectable sum of money to have it professionally designed. Hoping the usual suspects might be interested in my idea.

What's your idea?

 

[Scottmoose]

I'll look forward to seeing some pictures of the finished build.

New units are always nice to see. I have a pair of 10.3s here -thus far, it seems to be a solid unit with more HF extension than the 10.2 so I suspect people will find it closer in character to the smaller driver.