Shoebox-70.3 vs mMarS-1v0

Well, I was all set on building the Shoebox-70.3 using the Markaudio CHR-70.3 Gold when I stumbled across the mMarS-1v0 plan in the Frugal-phile library ( Now I'm wondering about the differences (physical and subjective) between the two. What I do know is the Shoebox is a Bass Reflex design versus the Sealed mMarS. The Shoebox is slightly larger in size at about 7 litres (Exterior: 14.4 cm W x 31.4 cm H x 23.6 cm D). The mMarS clocks in at 5.5 litres (Exterior: 17.3 cm W x 29.7 cm H x 17.85 cm D).

Although neither is a complicated build the mMarS looks to be the simpler of the two. This project is a gift that will be intended as near-field monitors for computer use by a college student so I will probably have to incorporate (removable) grilles for protection even though I'd rather not.

Does anyone know the expected output frequency range for these two designs? Results from subjective listening? Recommendations?

The sealed millSize box is 5.5 litre, it works pretty well. I figure optimum volume for the CHR at 9 litre so the larger shoebox will go lower (but perhaps not with the same finesse). It does look like it has some fiddly bits that aren't really going to do anything useful. I would also seriously worry about how skinny the shoebox is, the lowest we will go is 14 cm internal, smaller than that you get significant reflection back thru the cone with the sides so near.

For the CHR70.3 there is also a vented millSize box. For optimum performance (if you can live with the size) the Classic Golden Ratio box Frugal-phile | Box Library / Mark Audio

Thank you, Dave. I would be very interested in the vented millSize box. I don't see it at the Frugal-phile site. Is it available for download or do I need to pay you for the plans? I did look at the CGR box you referenced but I think it would be too wide/large for the intended application.

If I were to go with the Shoebox I would simplify the "reflector" behind the driver by turning it into a solid brace and forego the optional bracing altogether.

Good to know re: the internal width of the front panel. I'll keep that in mind when I design for future use of the CHR-70 driver. On a related note, I saw that the vertical brace on the mMarS is just off-center while the horizontal brace is centered behind the driver magnet. I've noted your designs typically incorporate the driver brace slightly off-center; any reason for the change in this design? Also, instead of using paper shims for the final fitting of the brace would it work to use 1/8" thick gasket tape that compresses to 1/16", or would that be too much cushion for the brace to work as intended?

Thanks again for all your input and willingness to respond.

The vented millSize (and a whole lot more boxes) is in the paid plan-set (email me if you are interested). A subscription also entitles you to a custom box if so desired (ie it has been my intention to do a bunch of 7 litre boxes).

Off centre has to do with the box walls not the driver… so the horizontal brace is off-centre too (but on the centre of the driver).

A squishy shim will work but not be as effective at passing energy thru the brace to the other panels.


You already got the CHR-70.3? Otherwise you can take a look at the Pluvia 7 - newer model, easier to mount, a few $ more. Might need slightly bigger box vs CHR - Dave can confirm.


I do indeed have the CHR-70.3 drivers already as well as a pair of Alpair 6Ms for another summer project I'm working on. I definitely have my eyes on the Pluvia 7 for future projects, though, especially as they seem to be drop-in replacements for the CSS EL70s.



Paid Member
2011-02-04 11:35 am

Have fun with your build. I haven't listened to the CHR-70.3, but from what I have read on the forum they are good 4" drivers. I have a pair of the Alpair 6M gen2 also, and those do pretty nicely in the Stinger (Woden Baby Labs design).

What box do you have in mind for the Alpair 6M?
The Alpair 6Ms will be used in a folded variation of Jim Griffin's MLTL design. Jim told me that he had never attempted to fold his design and that I should make sure to preserve the original 30" line length through the center of the line and folds. I have a couple more twists to apply that I won't reveal right now but I do plan a build thread (or at least pictures) for the forum.

Will it be successful, who knows? I've been building speakers off and on for almost 30 years now and my instincts haven't failed me yet. I'm not afraid to think outside the box even when it comes to established designs, to tweak them to my own aesthetics.