Greetings to all!

I am starting a new project with the idea of having a corner MLTL cabinet using the following parameters,

Drivers - GPA 416-8B, GPA 802-8G, Altec 811B horn, GPA N1200-8A XOver (or other passive XO)
Room Size - 15 ft W X 30 ft L X 9 ft H
Amplifier - 45 SET integrated (76/6SN7/45 tubes), output impedance is ~ 3 Ohms

Maximum Cabinet Dimension - 60? H - (preferably including the horns) X 40? W along with appropriate depth for corner cabinets.

I know there are many GM designed MLTL materials out here and other forums however, I did reach out to GM for his help. As always, he is so kind in helping me out in this design.

Based on his initial calculation, here are the properties of the cabinet

Volume = ~25.25 ft^3 gross, so ~24 ft^3 net MLTL
L = 58.5"
W = 38.5"
D1 = 9.75" rectangular protrusion
D2 = 19.25" baffle to triangular section's 'point', though may want to square it off a bit due to room corners typically being a bit uneven
Horn down = 4.75"
Driver down = 22"
Therefore horn/driver ctc spacing = 17.25"

Vent = [1] 5" dia. x panel thickness [0.75" assumed]/side for ~25 Hz Fs or can both be on one side horizontally.
Recommend using a removable baffle to try up to [1] 9" dia. vent hole/side for more typical Altec tuning or just start big and add smaller hole discs till it sounds right. For all I know, having different size holes in each side may work best overall since the room dominates and SET tube amps can be pretty finicky about impedances not ruler flat, but the passive components to flatten a low Fs bass driver's impedance are large, not cheap.

We thought it would be good to continue the discussion in this forum. So?.

Also, Many Thanks to Westend, Dan Kercher, and Altec Best (John) and others for posting their MLTL design in detail and answering my questions.

-Sri

- - - Updated - - -

GM,

Thanks for the measurement. From our conversations...


Right, I understood that there's a 60" speaker height limit plus this is to be basically a tall M19, so the horn sits in a cavity with foam around it.
Is the total speaker height 60" or ??
Note again that ideally we want the woofer in a room odd harmonic, which ATM is within a fraction of an inch based on a 96" room height.
Note that for your tall M19, the woofer ideally needs to be mounted on the face of the baffle to preserve the time/phase offset.


60? is what I am thinking of maximum height, few more (up to 4 or 5?) is fine if required. Can I keep the horn in a separate box, with foam around, on top of the cabinet? This might add some flexibility.

Thank you,
Sri